Separated Fringe Packet Observations with the Chara Array. 1. Methods and New Orbits for chi Draconis, HD 184467, and HD 198084

DTIC Science & Technology

2010-06-01

similar experiments using the Infrared Optical Telescope Array ( IOTA ) on the well- studied, widely separated binary ζ Hercules, in an attempt to revive...SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT Same as Report (SAR) 18. NUMBER OF PAGES 11 19a. NAME OF RESPONSIBLE PERSON...SFPs with IOTA As noted by Dyck et al. (1995), for a binary star for which both components are within the field of view of the interferometer, it is

IUE observations of the M dwarfs CM Draconis and Rossiter 137 B - Magnetic activity at saturated levels

NASA Technical Reports Server (NTRS)

Vilhu, O.; Brandenburg, A.; Ambruster, C. W.; Neff, J. E.; Linsky, J. L.

1989-01-01

IUE observations of two active M dwarfs with known rotation rate or age and presumed to be almost totally convective are presented. The first of these stars, CM Draconis (Gl 630.1), is an old Population II binary with its components in tidally induced rapid rotation (P = 1.27 d, dM 4 + dM 4). The other one, Rossiter 137 B, forms with HD 36705 (AB Dor) a visual pair of young active stars. The activity of CM Dra is due to the forced rotation in a close binary, while Rst 137 B is assumed to rotate fast enough to generate its magnetica activity. These results are compared with those for M dwarfs, particularly AU Mic and YZ CMi, that have known rotational periods and measured ultraviolet emission line fluxes. The chromospheric-coronal saturation levels of cool dwarfs between 0.3 less than B-V less than 1.6 is determined. It is found that saturated F stars have stronger chromospheres than saturated M stars, but the opposite is true for the corona. Results of these observations seem to favor a rotation-dependent distributed dynamo generating magnetic flux in totally convective stars.

Stellar Astrophysics with a Dispersed Fourier Transform Spectrograph. II. Orbits of Double-lined Spectroscopic Binaries

NASA Astrophysics Data System (ADS)

Behr, Bradford B.; Cenko, Andrew T.; Hajian, Arsen R.; McMillan, Robert S.; Murison, Marc; Meade, Jeff; Hindsley, Robert

2011-07-01

We present orbital parameters for six double-lined spectroscopic binaries (ι Pegasi, ω Draconis, 12 Boötis, V1143 Cygni, β Aurigae, and Mizar A) and two double-lined triple star systems (κ Pegasi and η Virginis). The orbital fits are based upon high-precision radial velocity (RV) observations made with a dispersed Fourier Transform Spectrograph, or dFTS, a new instrument that combines interferometric and dispersive elements. For some of the double-lined binaries with known inclination angles, the quality of our RV data permits us to determine the masses M 1 and M 2 of the stellar components with relative errors as small as 0.2%.

Chromospherically Active Stars. XXV. HD 144110=EV Draconis, a Double-lined Dwarf Binary

NASA Astrophysics Data System (ADS)

Fekel, Francis C.; Henry, Gregory W.; Lewis, Ceteka

2005-08-01

New spectroscopic and photometric observations of HD 144110 have been used to obtain an improved orbital element solution and determine some basic properties of the system. This chromospherically active, double-lined spectroscopic binary has an orbital period of 1.6714012 days and a circular orbit. We classify the components as G5 V and K0 V and suggest that they are slightly metal-rich. The photometric observations indicate that the rotation of HD 144110 is synchronous with the orbital period. Despite the short orbital period, no evidence of eclipses is seen in our photometry.

Discovery and observation of BY Draconis variables

NASA Astrophysics Data System (ADS)

Bopp, B. W.; Noah, P. V.; Klimke, A.; Africano, J.

1981-10-01

The discovery of BY Draconis variables was efficiently accomplished by a spectroscopic survey of dK-M stars for weak H-alpha emissions, using 1-2 A resolution. The four BY Dra variables discovered are all spectroscopic binaries with P values lower than about 10 d, in light of which, it is noted that the onset of high surface activity and appearance of H-alpha emission occur sharply at v(equator) of approximately 5 km/sec. At v(equator) of about 3 km/sec, dK-M stars have low levels of surface activity. It is found that while there is a range of Ca II emission strength, and only the strongest emitters of this line are BY Dra and/or flare stars, the H-alpha feature changes abruptly to an emission feature signaling the onset of flaring and/or the BY Dra syndrome. An increase of the rotation rate above v(equator) 5 km/sec does not appear to increase the level of surface activity.

Spectroscopic Binary Star Studies with the Palomar Testbed Interferometer II

NASA Astrophysics Data System (ADS)

Boden, A. F.; Lane, B. F.; Creech-Eakman, M.; Queloz, D.; PTI Collaboration

1999-12-01

The Palomar Testbed Interferometer (PTI) is a long-baseline near-infrared interferometer located at Palomar Observatory. Following our previous work on resolving spectroscopic binary stars with the Palomar Testbed Interferometer (PTI), we will present a number of new visual and physical orbit determinations derived from integrated reductions of PTI visibility and archival radial velocity data. The six systems for which we will present new orbit models are: 12 Boo (HD 123999), 75 Cnc (HD 78418), 47 And (HD 8374), HD 205539, BY Draconis (HDE 234677), and 3 Boo (HD 120064). Most of these systems are double-lined binary systems (SB2), and integrated astrometric/radial velocity orbit modeling provides precise fundamental parameters (mass, luminosity) and system distance determinations comparable with Hipparcos precisions. The work described in this paper was performed under contract with the National Aeronautics and Space Administration.

New high-precision orbital and physical parameters of the double-lined low-mass spectroscopic binary BY Draconis

NASA Astrophysics Data System (ADS)

Hełminiak, K. G.; Konacki, M.; Muterspaugh, M. W.; Browne, S. E.; Howard, A. W.; Kulkarni, S. R.

2012-01-01

We present the most precise to date orbital and physical parameters of the well-known short period (P= 5.975 d), eccentric (e= 0.3) double-lined spectroscopic binary BY Draconis (BY Dra), a prototype of a class of late-type, active, spotted flare stars. We calculate the full spectroscopic/astrometric orbital solution by combining our precise radial velocities (RVs) and the archival astrometric measurements from the Palomar Testbed Interferometer (PTI). The RVs were derived based on the high-resolution echelle spectra taken between 2004 and 2008 with the Keck I/high-resolution echelle spectrograph, Shane/CAT/HamSpec and TNG/SARG telescopes/spectrographs using our novel iodine-cell technique for double-lined binary stars. The RVs and available PTI astrometric data spanning over eight years allow us to reach 0.2-0.5 per cent level of precision in Msin 3i and the parallax but the geometry of the orbit (i≃ 154°) hampers the absolute mass precision to 3.3 per cent, which is still an order of magnitude better than for previous studies. We compare our results with a set of Yonsei-Yale theoretical stellar isochrones and conclude that BY Dra is probably a main-sequence system more metal rich than the Sun. Using the orbital inclination and the available rotational velocities of the components, we also conclude that the rotational axes of the components are likely misaligned with the orbital angular momentum. Given BY Dra's main-sequence status, late spectral type and the relatively short orbital period, its high orbital eccentricity and probable spin-orbit misalignment are not in agreement with the tidal theory. This disagreement may possibly be explained by smaller rotational velocities of the components and the presence of a substellar mass companion to BY Dra AB.

A catalogue of chromospherically active binary stars (third edition)

NASA Astrophysics Data System (ADS)

Eker, Z.; Ak, N. Filiz; Bilir, S.; Doǧru, D.; Tüysüz, M.; Soydugan, E.; Bakış, H.; Uǧraş, B.; Soydugan, F.; Erdem, A.; Demircan, O.

2008-10-01

The catalogue of chromospherically active binaries (CABs) has been revised and updated. With 203 new identifications, the number of CAB stars is increased to 409. The catalogue is available in electronic format where each system has a number of lines (suborders) with a unique order number. The columns contain data of limited numbers of selected cross references, comments to explain peculiarities and the position of the binarity in case it belongs to a multiple system, classical identifications (RS Canum Venaticorum, BY Draconis), brightness and colours, photometric and spectroscopic data, a description of emission features (CaII H and K, Hα, ultraviolet, infrared), X-ray luminosity, radio flux, physical quantities and orbital information, where each basic entry is referenced so users can go to the original sources.

A new photometric study of the triple star system EF Draconis

NASA Astrophysics Data System (ADS)

Yang, Yuan-Gui

2012-04-01

We present new charge-coupled device (CCD) photometry for the triple star EF Draconis, obtained in 2009 and 2011. Using the updated Wilson-Devinney program, the photometric solutions were deduced from two sets of light curves. The results indicate that EF Dra is an A-type W UMa binary with a contact degree of f = 46.7%(±0.6%) and a third light of l3 ≃ 1.5%. Through analyzing the O — C curve, it is found that the orbital period shows a long-time increase with a light-time orbit. The period, semi-amplitude and eccentricity of the third body are Pmod = 17.20(±0.18) yr, A = 0.0039d(±0.0002d) and e = 0.49(±0.02) respectively. This kind of tertiary companion may extract angular momentum from the central system. The orbital period of EF Dra secularly increases at a rate of dP/dt = +3.72(±0.07) × 10-7 d yr-1, which may be interpreted by mass transfer from the less massive to the more massive component. As period increases, the separation between components may increase, which will cause the contact degree to decrease. With mass transferring, the spin angular momentum will increase, while the orbital angular momentum will decrease. Only if the contact configuration would merge at could this kind of deep-contact binary with period increasing, such as EF Dra, evolve into a rapidly-rotating single star.

Orbital period study of the Algol-type eclipsing binary system TW Draconis

NASA Astrophysics Data System (ADS)

Qian, S. B.; Boonrucksar, S.

2002-10-01

The century-long times of light minimum of the Algol-type eclipsing binary star, TW Dra (BD +64°1077, Sp A5V+K2III), are investigated by considering a new pattern of period change. Two sudden period increases and two successive period decreases are discovered to superimpose on a rapid secular increase (d P/d t=+4.43×10 -6 days/year). The secular increase may be caused by a dynamical mass transfer from the secondary to the primary component (d m/d t=6.81×10 -7 M ⊙/year) that is in agreement with the semi-detached configuration of the system and with the existence of a hot spot and a gaseous stream in the binary system. The irregular period jumps superimposed on the secular increase can be explained by the structure variation of the K2-type giant via instabilities of the outer convective layer or via magnetic activity cycles.

Resolution and Orbit Reconstruction of Spectroscopic Binary Stars with the Palomar Testbed Interferometer

NASA Astrophysics Data System (ADS)

Boden, A. F.; Lane, B. F.; Creech-Eakman, M. J.; Queloz, D.; Koresko, C. D.

2000-05-01

The Palomar Testbed Interferometer (PTI) is a long-baseline near-infrared interferometer located at Palomar Observatory. For the past several years we have had an ongoing program of resolving and reconstructing the visual and physical orbits of spectroscopic binary stars with PTI, with the goal of obtaining precise dynamical mass estimates and other physical parameters. We will present a number of new visual and physical orbit determinations derived from integrated reductions of PTI visibility and archival and new spectroscopic radial velocity data. The systems for which we will discuss our orbit models are: iota Pegasi (HD 210027), 64 Psc (HD 4676), 12 Boo (HD 123999), 75 Cnc (HD 78418), 47 And (HD 8374), HD 205539, BY Draconis (HDE 234677), and 3 Boo (HD 120064), and 3 Boo (HD 120064). All of these systems are double-lined binary systems (SB2), and integrated astrometric/radial velocity orbit modeling provides precise fundamental parameters (mass, luminosity) and system distance determinations comparable with Hipparcos precisions.

Period changes of the long-period cataclysmic binary EX Draconis

NASA Astrophysics Data System (ADS)

Pilarčík, L.; Wolf, M.; Dubovský, P. A.; Hornoch, K.; Kotková, L.

2012-03-01

The cataclysmic variable star EX Dra is a relatively faint but frequently investigated eclipsing dwarf nova. In total 35 new eclipses were measured photometrically as part of our long-term monitoring of interesting eclipsing systems. Using published and new mid-eclipse times obtained between 2004 and 2011 we constructed the observed-minus-calculated diagram. The current data present 21 years of period modulation with a semi-amplitude of 2.5 min. The eclipse timings show significant deviations from the best sinusoidal fit, which indicates that this ephemeris is not a complete description of the data. The fractional period change is roughly ΔP/P = 3 × 10-6.

Calibration of H-alpha/H-beta Indexes for Emission Line Objects

NASA Astrophysics Data System (ADS)

Hintz, Eric G.; Joner, Michael D.

2016-01-01

In Joner and Hintz (2015) they report on a standard star system for calibration of H-alpha and H-beta observations. This work was based on data obtained with the Dominion Astrophysical Observatory 1.2-m telescope. As part of the data acquisition for that project, a large number of emission line objects were also observed. We will report on the preliminary results for the emission line data set. This will include a comparison of equivalent width measurements of each line with the matching index. We will also examine the relation between the absorption line objects previously published and the emission line objects, along with a discussion of the transition point. Object types included are Be stars, high mass x-ray binaries, one low mass x-ray binary, Herbig Ae/Be stars, pre-main sequence stars, T Tauri stars, young stellar objects, and one BY Draconis star. Some of these objects come from Cygnus OB-2, NGC 659, NGC 663, NGC 869 and NGC 884.

Effect of Ag Addition on the Electrochemical Performance of Cu10Al in Artificial Saliva

PubMed Central

Salgado-Salgado, R. J.; Sotelo-Mazon, O.; Rodriguez-Diaz, R. A.; Salinas-Solano, G.

2016-01-01

In this work we proposed to evaluate the corrosion resistance of four different alloys by electrochemical techniques, a binary alloy Cu10Al, and three ternary alloys Cu10Al-xAg (x = 5, 10, and 15 wt.%) to be used like biomaterials in dental application. Biomaterials proposed were tested in artificial saliva at 37°C for 48 h. In addition, pure metals Cu, Al, Ag, and Ti as reference materials were evaluated. In general the short time tests indicated that the Ag addition increases the corrosion resistance and reduces the extent of localized attack of the binary alloy. Moreover, tests for 48 hours showed that the Ag addition increases the stability of the passive layer, thereby reducing the corrosion rate of the binary alloy. SEM analysis showed that Cu10Al alloy was preferably corroded by grain boundaries, and the Ag addition modified the form of attack of the binary alloy. Cu-rich phases reacted with SCN− anions forming a film of CuSCN, and the Ag-rich phase is prone to react with SCN− anions forming AgSCN. Thus, binary and ternary alloys are susceptible to tarnish in the presence of thiocyanate ions. PMID:27660601

Analysis of the multiple system with chemically peculiar component φ Draconis

NASA Astrophysics Data System (ADS)

Liška, J.

2016-09-01

The star ϕ Dra comprises a spectroscopic binary and a third star that together form a visual triple system. It is one of the brightest chemically peculiar stars of the upper main sequence. Despite these facts, no comprehensive study of its multiplicity has been performed yet. In this work, we present a detailed analysis of the triple system based on available measurements. We use radial velocities taken from four sources in the literature in a re-analysis of the inner spectroscopic binary (Aab). An incorrect value of the orbital period of the inner system Aab about 27 d was accepted in literature more than 40 yr. A new solution of orbit with the 128-d period was determined. Relative position measurements of the outer visual binary system (AB) from Washington Double Star Catalog were compared with known orbital models. Furthermore, it was shown that astrometric motion in system AB is well described by the model of Andrade with a 308-yr orbital period. Parameters of A and B components were utilized to estimate individual brightness for all components and their masses from evolutionary tracks. Although we found several facts which support the gravitational bond between them, unbound solution cannot be fully excluded yet.

Resonances as the general cause of the outbursts in the symbiotic system AG Draconis

NASA Astrophysics Data System (ADS)

Gális, R.; Hric, L.; Friedjung, M.; Petrík, K.

1999-08-01

The general behaviour of the symbiotic system AG Dra is studied in the context of the long-term photometry monitoring and radial velocity analysis. Period analysis of the data gave two values of periods, 549fd73 +/- 1fd59 and 355fd27 +/- 1fd82 days for orbital motion and pulsations of cool giant respectively. The new orbital elements have been determined as well as the new orbital and pulsation ephemerides respectively. The ratio of the orbital to the pulsation period is actually very close to 14/9, so resonance might occur. We suggested, that this is the general cause of the recurrence time of the active stages. The pulsations of the cool component are very probably non-radial, so accretion by the white dwarf is particularly high when the material ejected due to the pulsations, is ejected in certain directions with respect to the line joining the two stars. The manifestations of this phenomena are the observed outbursts themselves.

Thermodynamic Optimization of the Ag-Bi-Cu-Ni Quaternary System: Part I, Binary Subsystems

NASA Astrophysics Data System (ADS)

Wang, Jian; Cui, Senlin; Rao, Weifeng

2018-07-01

A comprehensive literature review and thermodynamic optimization of the phase diagrams and thermodynamic properties of the Ag-Bi, Ag-Cu, Ag-Ni, Bi-Cu, and Bi-Ni binary systems are presented. CALculation of PHAse Diagrams (CALPHAD)-type thermodynamic optimization was carried out to reproduce all available and reliable experimental phase equilibrium and thermodynamic data. The modified quasichemical model was used to model the liquid solution. The compound energy formalism was utilized to describe the Gibbs energies of all terminal solid solutions and intermetallic compounds. A self-consistent thermodynamic database for the Ag-Bi, Ag-Cu, Ag-Ni, Bi-Cu, and Bi-Ni binary subsystems of the Ag-Bi-Cu-Ni quaternary system was developed. This database can be used as a guide for research and development of lead-free solders.

Thermodynamic Optimization of the Ag-Bi-Cu-Ni Quaternary System: Part I, Binary Subsystems

NASA Astrophysics Data System (ADS)

Wang, Jian; Cui, Senlin; Rao, Weifeng

2018-05-01

A comprehensive literature review and thermodynamic optimization of the phase diagrams and thermodynamic properties of the Ag-Bi, Ag-Cu, Ag-Ni, Bi-Cu, and Bi-Ni binary systems are presented. CALculation of PHAse Diagrams (CALPHAD)-type thermodynamic optimization was carried out to reproduce all available and reliable experimental phase equilibrium and thermodynamic data. The modified quasichemical model was used to model the liquid solution. The compound energy formalism was utilized to describe the Gibbs energies of all terminal solid solutions and intermetallic compounds. A self-consistent thermodynamic database for the Ag-Bi, Ag-Cu, Ag-Ni, Bi-Cu, and Bi-Ni binary subsystems of the Ag-Bi-Cu-Ni quaternary system was developed. This database can be used as a guide for research and development of lead-free solders.

Eclipsing cataclysmic variables. Deep eclipses in H0928+501. YY Draconis, the whirling dervish. New x ray pulsar candidates from HEAO-1

NASA Technical Reports Server (NTRS)

Patterson, Joseph

1993-01-01

The status report covering the period from 1 June 1992 to 31 May 1993 is included. Areas of research include: (1) eclipsing cataclysmic variables; (2) deep eclipses in H0928+501; (3) YY Draconis, the Whirling Dervish; and (4) new x ray pulsar candidates from HEAO-1.

Absolute Properties of the Eclipsing Binary Star BF Draconis

NASA Astrophysics Data System (ADS)

Lacy, Claud H. Sandberg; Torres, Guillermo; Fekel, Francis C.; Sabby, Jeffrey A.; Claret, Antonio

2012-06-01

BF Dra is now known to be an eccentric double-lined F6+F6 binary star with relatively deep (0.7 mag) partial eclipses. Previous studies of the system are improved with 7494 differential photometric observations from the URSA WebScope and 9700 from the NFO WebScope, 106 high-resolution spectroscopic observations from the Tennessee State University 2 m automatic spectroscopic telescope and the 1 m coudé-feed spectrometer at Kitt Peak National Observatory, and 31 accurate radial velocities from the CfA. Very accurate (better than 0.6%) masses and radii are determined from analysis of the two new light curves and four radial velocity curves. Theoretical models match the absolute properties of the stars at an age of about 2.72 Gyr and [Fe/H] = -0.17, and tidal theory correctly confirms that the orbit should still be eccentric. Our observations of BF Dra constrain the convective core overshooting parameter to be larger than about 0.13 Hp . We find, however, that standard tidal theory is unable to match the observed slow rotation rates of the components' surface layers.

The high velocity symbiotic star AG Draconis after its 1980 outburst

NASA Technical Reports Server (NTRS)

Viotti, R.; Altamore, A.; Baratta, G. B.; Cassatella, A.; Friedjung, M.; Giangrande, A.; Ponz, D.; Ricciardi, O.

1982-01-01

High and low resolution spectra of AG Dra taken in 1981 are analyzed. The UV spectrum of AG Dra is characterized by prominent high ionization emission lines superimposed on a strong continuum. At high resolution, several intense absorption lines of interstellar origin are seen, in spite of the low interstellar extinction. A similar situation is displayed by the high galactic latitude sd0 stars. The radial velocity difference between the emission lines and the i.s. lines is about -105 Km/sec in agreement with the optical observations. The He II 1640 A line appears much stronger than in other symbiotic stars and suggests the presence of a hot source which is variable according to the activity of the star. The line also exhibits broad emission wings which could be formed in a rotating disk. The NV resonance doublet displays a P Cygni profile and is probably formed in a warm wind. Two components in the UV continuum are identified: a steep component dominating the far UV probably associated with the hot source, and a flatter continuum in the near UV which cannot be accounted for by f-f and f-b emission alone, but which is probably emitted by an optically thick region or disk.

Detection of a stellar flare at extreme ultraviolet wavelengths

NASA Technical Reports Server (NTRS)

Barstow, M. A.; Denby, M.; Pye, J. P.; Pankiewicz, G. S.; Bromage, G. E.; Gonzalez-Riestra, R.

1991-01-01

During the all-sky survey conducted by the Rosat Wide Field Camera, the binary flare star system BY Draconis was monitored with coverage by the IUE satellite far-UV and optical observations and by the Rosat X-ray telescope for part of the time. A stellar flare was detected in all four wavebands. This is the first unambiguous EUV detection of a flare and one of the widest simultaneous wavelength-range coverages obtained. The peak luminosity and total energy of this flare in the photon energy range 0.08-0.18 keV are comparable with the values obtained for a number of flares integrated over a larger energy range by Exosat satellite observations in 1983-86. It is concluded that radiation in the EUV carries away a substantial fraction of the total flare energy.

New Precision Orbits of Bright Double-Lined Spectroscopic Binaries. III. HD 82191, ω Draconis, and 108 Herculis

NASA Astrophysics Data System (ADS)

Fekel, Francis C.; Tomkin, Jocelyn; Williamson, Michael H.

2009-04-01

We have determined improved spectroscopic orbits for three double-lined binaries, HD 82191 (Am), ω Dra (F5 V), and 108 Her (Am), using radial velocities from the 2.1 m telescope at McDonald Observatory, the coudé feed telescope at Kitt Peak National Observatory, and 2 m telescope at Fairborn Observatory. The orbital periods range from 5.28 to 9.01 days, and all three systems have circular orbits. The new orbital dimensions (a 1 sin i and a 2 sin i) and minimum masses (m 1 sin3 i and m 2 sin3 i) have accuracies of 0.2% or better. Our improved results confirm the large minimum masses of HD 82191 and also agree with the values previously found for ω Dra. However, for the components of 108 Her our minimum masses are about 20% larger than the previous best values. We conclude that both components of HD 82191 as well as the primary of 108 Her are Am stars. However, the A9 secondary of 108 Her has normal abundances. We estimate spectral types of F4 dwarf and G0 dwarf for the components of ω Dra. The primaries of the three binaries are synchronously rotating as is the secondary of 108 Her. The secondaries of HD 82191 and ω Dra are possibly synchronously rotating.

Absolute Properties of the Pulsating Post-mass Transfer Eclipsing Binary OO Draconis

NASA Astrophysics Data System (ADS)

Lee, Jae Woo; Hong, Kyeongsoo; Koo, Jae-Rim; Park, Jang-Ho

2018-01-01

OO Dra is a short-period Algol system with a δ Sct-like pulsator. We obtained time-series spectra between 2016 February and May to derive the fundamental parameters of the binary star and to study its evolutionary scenario. The radial velocity (RV) curves for both components were presented, and the effective temperature of the hotter and more massive primary was determined to be {T}{eff,1}=8260+/- 210 K by comparing the disentangling spectrum and the Kurucz models. Our RV measurements were solved with the BV light curves of Zhang et al. using the Wilson-Devinney binary code. The absolute dimensions of each component are determined as follows: M 1 = 2.03 ± 0.06 {M}⊙ , M 2 = 0.19 ± 0.01 {M}⊙ , R 1 = 2.08 ± 0.03 {R}⊙ , R 2 = 1.20 ± 0.02 {R}⊙ , L 1 = 18 ± 2 {L}⊙ , and L 2 = 2.0 ± 0.2 {L}⊙ . Comparison with stellar evolution models indicated that the primary star resides inside the δ Sct instability strip on the main sequence, while the cool secondary component is noticeably overluminous and oversized. We demonstrated that OO Dra is an oscillating post-mass transfer R CMa-type binary; the originally more massive star became the low-mass secondary component through mass loss caused by stellar wind and mass transfer, and the gainer became the pulsating primary as the result of mass accretion. The R CMa stars, such as OO Dra, are thought to have formed by non-conservative binary evolution and ultimately to evolve into EL CVn stars.

Optical and UV spectra of RS CVn stars

NASA Technical Reports Server (NTRS)

Ramsey, Lawrence W.

1990-01-01

The observed phenomenology in RS CVn and related binary systems is considered in terms of its modeling according to solar activity by examining UV and optical spectroscopy. Current data are examined to validate the existence of cool starspots, plage, prominences, and flares, as well as to determine the consistency of spatial correlations given by these data. RS CVn stars show spots at or near the poles, contrasting the low latitudes of solar spots; plage appears to be associated with cool spots on BY Draconis-like systems; plage and prominences, although identified as distinct phenomena, are theorized to be the same event in some cases. More spectroscopic and photometric observations are proposed to identify the detailed structure and locations of spots. UV and visible data are also required to distinguish plage regions from flare variations as well as determine the relation of extended structures to starspot and plage phenomena in RS CVn systems.

Eclipse studies of the dwarf nova EX Draconis

NASA Astrophysics Data System (ADS)

Baptista, R.; Catalán, M. S.; Costa, L.

2000-08-01

We report on V and R high-speed photometry of the dwarf nova EX Draconis (EX Dra) in quiescence and in outburst. The analysis of the outburst light curves indicates that the outbursts do not start in the outer disc regions. The disc expands during the rise to maximum and shrinks during decline and along the following quiescent period. The decrease in brightness at the later stages of the outburst is due to the fading of the light from the inner disc regions. At the end of two outbursts the system was seen to go through a phase of lower brightness, characterized by an out-of-eclipse level ~=15 per cent lower than the typical quiescent level and by the fairly symmetric eclipse of a compact source at disc centre with little evidence of a bright spot at disc rim. New eclipse timings were measured from the light curves taken in quiescence and a revised ephemeris was derived. The residuals with respect to the linear ephemeris are well described by a sinusoid of amplitude 1.2min and period ~=4yr and are possibly related to a solar-like magnetic activity cycle in the secondary star. Eclipse phases of the compact central source and of the bright spot were used to derive the geometry of the binary. By constraining the gas stream trajectory to pass through the observed position of the bright spot, we find q=0.72+/-0.06 and i85+3-2 degrees. The binary parameters were estimated by combining the measured mass ratio with the assumption that the secondary star obeys an empirical main-sequence mass-radius relation. We find M1=0.75+/-0.15Msolar and M2=0.54+/-0.10Msolar. The results indicate that the white dwarf at disc centre is surrounded by an extended and variable atmosphere or boundary layer of at least three times its radius and a temperature of T~=28000K. The fluxes at mid-eclipse yield an upper limit to the contribution of the secondary star and lead to a lower limit photometric parallax distance of D=290+/-80pc. The fluxes of the secondary star are well-matched by those of a M0+/-2 main-sequence star.

Absolute Parameters and Physical Nature of the Low-amplitude Contact Binary HI Draconis

NASA Astrophysics Data System (ADS)

Papageorgiou, A.; Christopoulou, P.-E.

2015-05-01

We present a detailed investigation of the low-amplitude contact binary HI Dra based on the new VRcIc CCD photometric light curves (LCs) combined with published radial velocity (RV) curves. Our completely covered LCs were analyzed using PHOEBE and revealed that HI Dra is an overcontact binary with low fill-out factor f = 24 ± 4(%) and temperature difference between the components of 330 K. Two spotted models are proposed to explain the LC asymmetry, between which the A subtype of W UMa type eclipsing systems, with a cool spot on the less massive and cooler component, proves to be more plausible on evolutionary grounds. The results and stability of the solutions were explored by heuristic scan and parameter perturbation to provide a consistent and reliable set of parameters and their errors. Our photometric modeling and RV curve solution give the following absolute parameters of the hot and cool components, respectively: Mh = 1.72 ± 0.08 {{M}⊙ } and Mc = 0.43 ± 0.02 {{M}⊙ }, Rh = 1.98 ± 0.03 {{R}⊙ } and Rc = 1.08 ± 0.02 {{R}⊙ }, and Lh = 9.6 ± 0.1 {{L}⊙ } and Lc = 2.4 ± 0.1 {{L}⊙ }. Based on these results the initial masses of the progenitors (1.11 ± 0.03 {{M}⊙ } and 2.25 ± 0.07 {{M}⊙ }, respectively) and a rough estimate of the age of the system of 2.4 Gyr are discussed.

Absolute Properties of the Low-Mass Eclipsing Binary CM Draconis

NASA Astrophysics Data System (ADS)

Morales, Juan Carlos; Ribas, Ignasi; Jordi, Carme; Torres, Guillermo; Gallardo, José; Guinan, Edward F.; Charbonneau, David; Wolf, Marek; Latham, David W.; Anglada-Escudé, Guillem; Bradstreet, David H.; Everett, Mark E.; O'Donovan, Francis T.; Mandushev, Georgi; Mathieu, Robert D.

2009-02-01

Spectroscopic and eclipsing binary systems offer the best means for determining accurate physical properties of stars, including their masses and radii. The data available for low-mass stars have yielded firm evidence that stellar structure models predict smaller radii and higher effective temperatures than observed, but the number of systems with detailed analyses is still small. In this paper, we present a complete reanalysis of one of such eclipsing systems, CM Dra, composed of two dM4.5 stars. New and existing light curves as well as a radial velocity curve are modeled to measure the physical properties of both components. The masses and radii determined for the components of CM Dra are M 1 = 0.2310 ± 0.0009 M sun, M 2 = 0.2141 ± 0.0010M sun, R 1 = 0.2534 ± 0.0019 R sun, and R 2 = 0.2396 ± 0.0015 R sun. With relative uncertainties well below the 1% level, these values constitute the most accurate properties to date for fully convective stars. This makes CM Dra a valuable benchmark for testing theoretical models. In comparing our measurements with theory, we confirm the discrepancies previously reported for other low-mass eclipsing binaries. These discrepancies seem likely to be due to the effects of magnetic activity. We find that the orbit of this system is slightly eccentric, and we have made use of eclipse timings spanning three decades to infer the apsidal motion and other related properties.

Periodicity and eclipse minima timing of CM Draconis.

NASA Astrophysics Data System (ADS)

Vázquez-Martín, S.; Deeg, H. J.; Dreizler, S.; von Essen, C.; Kozhevnikov, V. P.

2015-05-01

Periodic deviations from a linear ephemeris of a binary star's eclipses can indicate the presence of a third body in orbit around both. Hints for such companion around the M4.5/M4.5 binary CMDra were published by Deeg et al. (2008). The assignment of a planet in the CMDra system can however only be accepted if the earlier observed periodicity trends can be verified through further observations over several years. For eclipsing binary stars of low mass, the method of eclipse minimum timing allows one to set mass limits for the detection of a third body. Deeg et al. (2008) concluded that the two possibilities for the source of CMDra's timing variations that remain valid are a planet of a few Jupiter masses on a two decade-long orbit, or an object on a century-to-millenium long orbit with masses 1.5M_J < M_{p} < 0.1M_{⊙}. However, they concluded that it is necessary to do continued observations of the timing of CMDra's eclipses to be decisive regarding the continued viability of the sinusoidal-fit-model, and hence, about the validity of a Jovian-type planet in a circumbinary orbiting around the system. Here we update the analysis of Deeg et al. (2008), including further data presented in Morales et al. (2009r) and new observations taken at Ural Observatory (2008-2013). Eclipse minimum times were obtained using the Kwee-van-Woerden method.

Ultraviolet photometry from the Orbiting Astronomical Observatory. XXXIII - The symbiotic star AG Pegasi

NASA Technical Reports Server (NTRS)

Gallagher, J. S.; Webbink, R. F.; Holm, A. V.; Anderson, C. M.

1979-01-01

Ultraviolet broadband photometry obtained with the Wisconsin Experiment Package on OAO 2 is presented for the symbiotic binary star AG Peg. The hot component of the binary is found to be a luminous ultraviolet source, with an energy distribution consistent with its WN6 optical spectral type. Total luminosities of 1000 and 17,000 suns are found for the hot star by assuming, respectively, that the giant primary of AG Peg is a normal M3 III star and that it fills its Roche lobe. The eruptive behavior of AG Peg is shown to require the higher luminosity, and the activity in AG Peg is discussed in terms of a very slow novalike nuclear-powered event.

Evaluation of the Wound Healing Potential of Resina Draconis (Dracaena cochinchinensis) in Animal Models.

PubMed

Liu, Huihui; Lin, Shaohui; Xiao, Dan; Zheng, Xiao; Gu, Yan; Guo, Shanyu

2013-01-01

Resina Draconis (RD) is a type of dragon's blood resin obtained from Dracaena cochinchinensis (Lour.) S.C. Chen (Yunnan, China). It has been used as a medicine since ancient times by many cultures. The ethanolic extract of Resina Draconis (RDEE) was evaluated for its wound-healing activity using excision and incision wound models in rats. Group I, the control group, was treated with ointment base. Group II, which served as a reference standard, was treated with moist exposed burn ointment (MEBO). Group III was treated with RDEE. The parameters observed were percentage of wound contraction, epithelialization period, tensile strength, histopathological studies, microvessel density (MVD), and the expression of vascular endothelial growth factor (VEGF) and transforming growth factor- β 1 (TGF- β 1). The group treated with RDEE showed significantly better wound contraction and better skin-breaking strength as compared with the control group. The results of histopathological examination, MVD, and the expression levels of growth factors supported the outcome of the wound models as well. The present study provided a scientific rationale for the traditional use of RD in the management of wounds.

Evaluation of the Wound Healing Potential of Resina Draconis (Dracaena cochinchinensis) in Animal Models

PubMed Central

Gu, Yan

2013-01-01

Resina Draconis (RD) is a type of dragon's blood resin obtained from Dracaena cochinchinensis (Lour.) S.C. Chen (Yunnan, China). It has been used as a medicine since ancient times by many cultures. The ethanolic extract of Resina Draconis (RDEE) was evaluated for its wound-healing activity using excision and incision wound models in rats. Group I, the control group, was treated with ointment base. Group II, which served as a reference standard, was treated with moist exposed burn ointment (MEBO). Group III was treated with RDEE. The parameters observed were percentage of wound contraction, epithelialization period, tensile strength, histopathological studies, microvessel density (MVD), and the expression of vascular endothelial growth factor (VEGF) and transforming growth factor-β1 (TGF-β1). The group treated with RDEE showed significantly better wound contraction and better skin-breaking strength as compared with the control group. The results of histopathological examination, MVD, and the expression levels of growth factors supported the outcome of the wound models as well. The present study provided a scientific rationale for the traditional use of RD in the management of wounds. PMID:23762154

Effect of CdS Growth Time on the Optical Properties of One-Pot Preparation of CdS-Ag2S Binary Compounds

NASA Astrophysics Data System (ADS)

Karimipour, M.; Izadian, L.; Molaei, M.

2018-02-01

CdS-Ag2S binary nanoparticles were synthesized using a facile one-pot microwave irradiation method. The effect of initial nucleation of CdS quantum dots (QDs) using 3 min, 5 min, and 7 min of microwave irradiation on the optical properties of the final compound was studied. The composition and crystal structure of the compounds were verified using energy dispersive x-ray spectroscopy and x-ray diffraction. They revealed that existence of Ag and Cd elements with an atomic ratio of 0.19 crystalizes in the form of monoclinic Ag2S and hexagonal CdS. Scanning electron microscope images showed a spherical morphology of the resultant compound, and transmission electron microscope images showed the formation of fine particles of CdS-Ag2S composites with an average size of 5-7 nm and 10-14 nm for CdS and Ag2S, respectively. Photoluminescence spectroscopy revealed that the initial growth time of CdS has a crucial effect on the emission of binary compounds such that for 3 min and 5 min of irradiation of CdS solution, the binary compound obtains strong red and considerable near-IR emission (850 nm), but for longer time, it rapidly quenches. The results indicate that the strong red emission can be tuned from 600 nm up to 700 nm with prolonging nucleation time of CdS. This study also emphasized that the origin of red emission strongly depends on the size and defects created in the CdS QDs.

Influence of protein size on surface-enhanced Raman scattering (SERS) spectra in binary protein mixtures.

PubMed

Avci, Ertug; Culha, Mustafa

2014-01-01

The size-dependent interactions of eight blood proteins with silver nanoparticles (AgNPs) in their binary mixtures were investigated using surface-enhanced Raman scattering (SERS). Principal component analysis (PCA) was performed on the SERS spectra of each binary mixture, and the differentiation ability of the mixtures was tested. It was found that the effect of relative concentration change on the SERS spectra of the binary mixtures of small proteins could be detected using PCA. However, this change was not observed with the binary mixtures of large proteins. This study demonstrated that the relative interactions of the smaller proteins with an average size of 50 nm AgNPs smaller than the large proteins could be monitored, and this information can be used for the detection of proteins in protein mixtures.

Copper-based alloys, crystallographic and crystallochemical parameters of alloys in binary systems Cu-Me (Me=Co, Rh, Ir, Cu, Ag, Au, Ni, Pd, Pt)

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

Porobova, Svetlana, E-mail: porobova.sveta@yandex.ru; Loskutov, Oleg, E-mail: lom58@mail.ru; Markova, Tat’jana, E-mail: patriot-rf@mail.ru

2016-01-15

The article presents the results of the analysis of phase equilibrium of ordered phases in binary systems based on copper Cu- Me (where Me - Co, Rh, Ir, Ag, Au, Ni, Pd, Pt) to find correlations of crystallochemical and crystallographic factors. It is established that the packing index in disordered solid solutions in binary systems based on copper is close to the value of 0.74 against the background of an insignificant deviation of atomic volumes from the Zen’s law.

Potential carcinogenicity of homoisoflavanoids and flavonoids from Resina sanguinis draconis (Dracaena cinnabari Balf.).

PubMed

Vachálková, A; Novotný, L; Nejedlíková, M; Suchý, V

1995-01-01

Polarographic behavior of three homoisoflavanoids and four flavanoids isolated from the dragon's blood (Resina sanguinis draconis. Dracaena cinnabari Balf.), collected at Sokotra, was investigated in aprotic solution and an index of potential carcinogenicity tg alpha was determined. Generally, homoisoflavanoids and flavanoids were reduced in two two-electron steps, the first being reversible and the second one irreversible. The parameter tg alpha values indicated that the majority of these compounds possesses no or only marginal potential carcinogenic activity. However, it was demonstrated that some structural modifications in basic flavonoid structure lead to changed electrochemical properties and a substantial increase of derivative potential carcinogenicity.

The anticancer effects of Resina Draconis extract on cholangiocarcinoma.

PubMed

Wen, Feng; Zhao, Xiangxuan; Zhao, Yun; Lu, Zaiming; Guo, Qiyong

2016-11-01

Cholangiocarcinoma (CCA) is a relatively rare, heterogeneous malignant tumor with poor clinical outcomes. Because of high insensitivity to chemotherapy and radiotherapy, there are no effective treatment options. Efforts to identify and develop new agents for prevention and treatment of this deadly disease are urgent. Here, we assessed the apoptotic cytotoxicity of Resina Draconis extract (RDE) using in vitro and in vivo assays and identified the mechanisms underlying antitumor effects of RDE. RDE was obtained via vacuum distillation of Resina Draconis with 75 % ethanol. The ethanol extract could inhibit CCA cell proliferation and trigger apoptotic cell death in both QBC939 and HCCC9810 cell lines in a time- and concentration-dependent manner. RDE treatment resulted in intracellular caspase-8 and poly (ADP-ribose) polymerase protease activation. RDE significantly downregulated antiapoptotic protein survivin expression and upregulated proapoptotic protein Bak expression. RDE also inhibited CCA tumor growth in vivo. We observed that human CCA tissues had much higher survivin expression than did paired adjacent normal tissue. Taken together, the current data suggested that RDE has anticancer effects on CCA, and that RDE could function as a novel anticancer agent to benefit patients with CCA.

Survey of the BY Draconis syndrome among dMe stars. [BVr photometry search for slow quasisinusoidal light variations

NASA Technical Reports Server (NTRS)

Bopp, B. W.; Espenak, F.

1977-01-01

Results are reported for a BVr photometric survey of 22 dK, dKe, dM, and dMe stars conducted to search for slow quasi-sinusoidal fluctuations in V (the BY Draconis syndrome). The (B-V) and (V-r) color indices are determined in an attempt to detect wavelength-dependent color changes produced by starspots and to infer starspot temperatures. It is found that nine of the stars exhibit variations in V of the order of 0.05 to 0.10 magnitude on a time scale of days or weeks, that at least three more display changes in mean light level over a period of years, that the stars generally tend to become redder at minimum light, and that some of the stars show no detectable color changes over their photometric cycle. The color data are taken to suggest a probable temperature difference of about 200 to 500 K between the stellar photospheres and starspots if the V variations are attributed to dark spots. It is concluded that the BY Draconis syndrome is clearly a very common occurrence among dMe stars.

Radial Velocity Studies of Close Binary Stars. XI.

NASA Astrophysics Data System (ADS)

Pribulla, Theodor; Rucinski, Slavek M.; Lu, Wenxian; Mochnacki, Stefan W.; Conidis, George; Blake, R. M.; DeBond, Heide; Thomson, J. R.; Pych, Wojtek; Ogłoza, Waldemar; Siwak, Michal

2006-08-01

Radial-velocity measurements and sine-curve fits to orbital radial velocity variations are presented for 10 close binary systems: DU Boo, ET Boo, TX Cnc, V1073 Cyg, HL Dra, AK Her, VW LMi, V566 Oph, TV UMi, and AG Vir. With this contribution, the David Dunlap Observatory program has reached the point of 100 published radial velocity orbits. The radial velocities have been determined using an improved fitting technique that uses rotational profiles to approximate individual peaks in broadening functions. Three systems, ET Boo, VW LMi, and TV UMi, are found to be quadruple, while AG Vir appears to be a spectroscopic triple. ET Boo, a member of a close visual binary with Pvis=113 yr, was previously known to be a multiple system, but we show that the second component is actually a close, noneclipsing binary. The new observations have enabled us to determine the spectroscopic orbits of the companion, noneclipsing pairs in ET Boo and VW LMi. A particularly interesting case is VW LMi, for which the period of the mutual revolution of the two spectroscopic binaries is only 355 days. While most of the studied eclipsing pairs are contact binaries, ET Boo is composed of two double-lined detached binaries, and HL Dra is a single-lined detached or semidetached system. Five systems of this group have been observed spectroscopically before: TX Cnc, V1073 Cyg, AK Her (as a single-lined binary), V566 Oph, and AG Vir, but our new data are of much higher quality than in the previous studies. Based on data obtained at the David Dunlap Observatory, University of Toronto, Canada.

Detecting the Companions and Ellipsoidal Variations of RS CVn Primaries. II. o Draconis, a Candidate for Recent Low-mass Companion Ingestion

NASA Astrophysics Data System (ADS)

Roettenbacher, Rachael M.; Monnier, John D.; Fekel, Francis C.; Henry, Gregory W.; Korhonen, Heidi; Latham, David W.; Muterspaugh, Matthew W.; Williamson, Michael H.; Baron, Fabien; ten Brummelaar, Theo A.; Che, Xiao; Harmon, Robert O.; Schaefer, Gail H.; Scott, Nicholas J.; Sturmann, Judit; Sturmann, Laszlo; Turner, Nils H.

2015-08-01

To measure the stellar and orbital properties of the metal-poor RS CVn binary o Draconis (o Dra), we directly detect the companion using interferometric observations obtained with the Michigan InfraRed Combiner at Georgia State University's Center for High Angular Resolution Astronomy (CHARA) Array. The H-band flux ratio between the primary and secondary stars is the highest confirmed flux ratio (370 ± 40) observed with long-baseline optical interferometry. These detections are combined with radial velocity data of both the primary and secondary stars, including new data obtained with the Tillinghast Reflector Echelle Spectrograph on the Tillinghast Reflector at the Fred Lawrence Whipple Observatory and the 2 m Tennessee State University Automated Spectroscopic Telescope at Fairborn Observatory. We determine an orbit from which we find model-independent masses and ages of the components ({M}A=1.35+/- 0.05 {M}⊙ , {M}B=0.99+/- 0.02 {M}⊙ , system age = 3.0\\mp 0.5 Gyr). An average of a 23-year light curve of o Dra from the Tennessee State University Automated Photometric Telescope folded over the orbital period newly reveals eclipses and the quasi-sinusoidal signature of ellipsoidal variations. The modeled light curve for our system's stellar and orbital parameters confirm these ellipsoidal variations due to the primary star partially filling its Roche lobe potential, suggesting most of the photometric variations are not due to stellar activity (starspots). Measuring gravity darkening from the average light curve gives a best-fit of β =0.07+/- 0.03, a value consistent with conventional theory for convective envelope stars. The primary star also exhibits an anomalously short rotation period, which, when taken with other system parameters, suggests the star likely engulfed a low-mass companion that had recently spun-up the star.

Fabrication of (Ba,K)Fe2As2 tapes by ex situ PIT process using Ag-Sn alloy single sheath

NASA Astrophysics Data System (ADS)

Togano, K.; Gao, Z.; Matsumoto, A.; Kikuchi, A.; Kumakura, H.

2017-01-01

Instead of ordinal pure Ag, Ag-based Sn binary alloys (up to 7.5 at%Sn) with higher mechanical strength are used for the sheath material of ex situ powder-in-tube (PIT)-processed (Ba,K)Fe2As2(Ba-122) tapes. We found that the use of the Ag-Sn alloy enhances the densification and texturing of the Ba-122 core, resulting in higher transport, J c. Moreover, the optimum heat treatment temperature for a high J c can be lowered by around 100 °C due to the higher packing density of the Ba-122 core prior to the final heat treatment. We also found that the smoothness of the interface between the sheath and Ba-122 core is significantly improved by using the Ag-Sn binary alloy sheaths. These results show that the Ag-Sn alloy is promising as a sheath material in PIT-processed Ba-122 superconducting wires.

Long-Term Photometric and Spectroscopic Behavior of a Symbiotic System AG DRA

NASA Astrophysics Data System (ADS)

Gális, R.; Hric, L.; Petrík, K.

A symbiotic binary, AG Dra, is studied using long-term photometry and radial velocity measurements. New radial velocities confirm the presence of a second period, found in our previous analysis, which could be due to pulsation of the cool component of the AG Dra system.

Premelting phenomena in pseudo-binary ionic crystals

NASA Astrophysics Data System (ADS)

Matsunaga, Shigeki

2010-04-01

The theory of the premelting phenomena in ionic crystals on the basis of the concept of the heterophase fluctuation has been applied to the pseudo-binary ionic crystals, KCl-NaCl, AgBr-AgCl and AgBr-CuBr systems. Molecular dynamics simulations (MD) have been performed to examine the ionic configurations in their premelting region in the vicinity of their melting points. Liquid-like clusters have been observed in the results of MD utilizing the Lindemann instability condition. The sizes of liquid-like clusters have been estimated by theory and MD. The characteristics of the dynamical behavior of ions in the premelting region have been examined by the mean square displacement and the velocity correlation functions.

On the role of structure-dynamic relationship in determining the excess entropy of mixing and chemical ordering in binary square-well liquid alloys

NASA Astrophysics Data System (ADS)

Lalneihpuii, R.; Shrivastava, Ruchi; Mishra, Raj Kumar

2018-05-01

Using statistical mechanical model with square-well (SW) interatomic potential within the frame work of mean spherical approximation, we determine the composition dependent microscopic correlation functions, interdiffusion coefficients, surface tension and chemical ordering in Ag-Cu melts. Further Dzugutov universal scaling law of normalized diffusion is verified with SW potential in binary mixtures. We find that the excess entropy scaling law is valid for SW binary melts. The partial and total structure factors in the attractive and repulsive regions of the interacting potential are evaluated and then Fourier transformed to get partial and total radial distribution functions. A good agreement between theoretical and experimental values for total structure factor and the reduced radial distribution function are observed, which consolidates our model calculations. The well-known Bhatia-Thornton correlation functions are also computed for Ag-Cu melts. The concentration-concentration correlations in the long wavelength limit in liquid Ag-Cu alloys have been analytically derived through the long wavelength limit of partial correlation functions and apply it to demonstrate the chemical ordering and interdiffusion coefficients in binary liquid alloys. We also investigate the concentration dependent viscosity coefficients and surface tension using the computed diffusion data in these alloys. Our computed results for structure, transport and surface properties of liquid Ag-Cu alloys obtained with square-well interatomic interaction are fully consistent with their corresponding experimental values.

[Studying on purification technology of Resina Draconis phenol extracts based on design space method].

PubMed

Zhang, Jian; Zhang, Xin; Bi, Yu-An; Xu, Gui-Hong; Huang, Wen-Zhe; Wang, Zhen-Zhong; Xiao, Wei

2017-09-01

The "design space" method was used to optimize the purification process of Resina Draconis phenol extracts by using the concept of "quality derived from design" (QbD). The content and transfer rate of laurin B and 7,4'-dihydroxyflavone and yield of extract were selected as the critical quality attributes (CQA). Plackett-Burman design showed that the critical process parameters (CPP) were concentration of alkali, the amount of alkali and the temperature of alkali dissolution. Then the Box-Behnken design was used to establish the mathematical model between CQA and CPP. The variance analysis results showed that the P values of the five models were less than 0.05 and the mismatch values were all greater than 0.05, indicating that the model could well describe the relationship between CQA and CPP. Finally, the control limits of the above 5 indicators (content and transfer rate of laurine B and 7,4'-dihydroxyflavone, as well as the extract yield) were set, and then the probability-based design space was calculated by Monte Carlo simulation and verified. The results of the design space validation showed that the optimized purification method can ensure the stability of the Resina Draconis phenol extracts refining process, which would help to improve the quality uniformity between batches of phenol extracts and provide data support for production automation control. Copyright© by the Chinese Pharmaceutical Association.

Measurements of anisotropy in the cosmic microwave background radiation at degree angular scales near the stars Sigma Herculis and Iota Draconis

NASA Technical Reports Server (NTRS)

Clapp, A. C.; Devlin, M. J.; Gundersen, J. O.; Hagmann, C. A.; Hristov, V. V.; Lange, A. E.; Lim, M.; Lubin, P. M.; Mauskopf, P. D.; Meinhold, P. R.

1994-01-01

We present results from two four-frequency observations centered near the stars Sigma Herculis and Iota Draconis during the fourth flight of the Millimeter-wave Anisotropy eXperiment (MAX). The observations were made of 6 deg x 0.6 deg strips of the sky with a 1.4 deg peak to peak sinusoidal chop in all bands. The full width at half maximum (FWHM) beam sizes were calculated 0.55 deg +/- 0.05 deg at 3.5/cm and a 0.75 deg +/- 0.05 deg at 6, 9, and 14/cm. Significant correlated structures were observed at 3.5, 6, and 9/cm. The spectra of these signals are inconsistent with thermal emission from known interstellar dust populations. The extrapolated amplitudes of synchrotron and free-free emission are too small to account for the amplitude of the observed structures. If the observed structures are attributed to cosmic microwave background (CMB) anisotropy with a Gaussian autocorrelation function and a coherence angle of 25 min, then the most probable values at Delta T/T(sub CMB) = 3.1 (sup +1.7 sub -1.3) x 10(exp -5) for the Sigma Herculis scan, and Delta T/T(sub CMB) = 3.3(sup +1.1 sub -1.1) x 10(exp -5) for the Iota Draconis scan (95% confidence upper, lower limits).

Magnetic field and radial velocities of the star Chi Draconis A

NASA Astrophysics Data System (ADS)

Lee, Byeong-Cheol; Gadelshin, D.; Han, Inwoo; Kang, Dong-Il; Kim, Kang-Min; Valyavin, G.; Galazutdinov, G.; Jeong, Gwanghui; Beskrovnaya, N.; Burlakova, T.; Grauzhanina, A.; Ikhsanov, N. R.; Kholtygin, A. F.; Valeev, A.; Bychkov, V.; Park, Myeong-Gu

2018-01-01

We present high-resolution spectropolarimetric observations of the spectroscopic binary χ Dra. Spectral lines in the spectrum of the main component χ Dra A show variable Zeeman displacement, which confirms earlier suggestions about the presence of a weak magnetic field on the surface of this star. Within about 2 yr of time base of our observations, the longitudinal component BL of the magnetic field exhibits variation from -11.5 ± 2.5 to +11.1 ± 2.1 G with a period of about 23 d. Considering the rotational velocity of χ Dra A in the literature and that newly measured in this work, this variability may be explained by the stellar rotation under the assumption that the magnetic field is globally stable. Our new measurements of the radial velocities (RV) in high-resolution I-spectra of χ Dra A refined the orbital parameters and reveal persistent deviations of RVs from the orbital curve. We suspect that these deviations may be due to the influence of local magnetically generated spots, pulsations, or a Jupiter-size planet orbiting the system.

Surface tension estimation of high temperature melts of the binary alloys Ag-Au

NASA Astrophysics Data System (ADS)

Dogan, Ali; Arslan, Hüseyin

2017-11-01

Surface tension calculation of the binary alloys Ag-Au at the temperature of 1381 K, where Ag and Au have similar electronic structures and their atomic radii are comparable, are carried out in this study using several equations over entire composition range of Au. Apparently, the deviations from ideality of the bulk solutions, such as activities of Ag and Au are small and the maximum excess Gibbs free energy of mixing of the liquid phase is for instance -4500 J/mol at XAu = 0.5. Besides, the results obtained in Ag-Au alloys that at a constant temperature the surface tension increases with increasing composition while the surface tension decreases as the temperature increases for entire composition range of Au. Although data about surface tension of the Ag-Au alloy are limited, it was possible to make a comparison for the calculated results for the surface tension in this study with the available experimental data. Taken together, the average standard error analysis that especially the improved Guggenheim model in the other models gives the best agreement along with the experimental results at temperature 1383 K although almost all models are mutually in agreement with the other one.

Ligand Exchange Governs the Crystal Structures in Binary Nanocrystal Superlattices.

PubMed

Wei, Jingjing; Schaeffer, Nicolas; Pileni, Marie-Paule

2015-11-25

The surface chemistry in colloidal nanocrystals on the final crystalline structure of binary superlattices produced by self-assembly of two sets of nanocrystals is hereby demonstrated. By mixing nanocrystals having two different sizes and the same coating agent, oleylamine (OAM), the binary nanocrystal superlattices that are produced, such as NaCl, AlB2, NaZn13, and MgZn2, are well in agreement with the crystalline structures predicted by the hard-sphere model, their formation being purely driven by entropic forces. By opposition, when large and small nanocrystals are coated with two different ligands [OAM and dodecanethiol (DDT), respectively] while keeping all other experimental conditions unchanged, the final binary structures markedly change and various structures with lower packing densities, such as Cu3Au, CaB6, and quasicrystals, are observed. This effect of the nanocrystals' coating agents could also be extended to other binary systems, such as Ag-Au and CoFe2O4-Ag supracrystalline binary lattices. In order to understand this effect, a mechanism based on ligand exchange process is proposed. Ligand exchange mechanism is believed to affect the thermodynamics in the formation of binary systems composed of two sets of nanocrystals with different sizes and bearing two different coating agents. Hence, the formation of binary superlattices with lower packing densities may be favored kinetically because the required energetic penalty is smaller than that of a denser structure.

Thermodynamic assessment of Ag–Cu–In

DOE PAGES

Muzzillo, Christopher P.; Anderson, Tim

2018-01-16

The Ag-Cu-In thermodynamic material system is of interest for brazing alloys and chalcopyrite thin-film photovoltaics. To advance these applications, Ag-Cu-In was assessed and a Calphad model was developed. Binary Ag-Cu and Cu-In parameters were taken from previous assessments, while Ag-In was re-assessed. Structure-based models were employed for ..beta..-bcc(A2)-Ag 3In, ..gamma..-Ag 9In 4, and AgIn 2 to obtain good fit to enthalpy, phase boundary, and invariant reaction data for Ag-In. Ternary Ag-Cu-In parameters were optimized to achieve excellent fit to activity, enthalpy, and extensive phase equilibrium data. Relative to the previous Ag-Cu-In assessment, fit was improved while fewer parameters were used.

Thermodynamic assessment of Ag–Cu–In

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

Muzzillo, Christopher P.; Anderson, Tim

The Ag-Cu-In thermodynamic material system is of interest for brazing alloys and chalcopyrite thin-film photovoltaics. To advance these applications, Ag-Cu-In was assessed and a Calphad model was developed. Binary Ag-Cu and Cu-In parameters were taken from previous assessments, while Ag-In was re-assessed. Structure-based models were employed for ..beta..-bcc(A2)-Ag 3In, ..gamma..-Ag 9In 4, and AgIn 2 to obtain good fit to enthalpy, phase boundary, and invariant reaction data for Ag-In. Ternary Ag-Cu-In parameters were optimized to achieve excellent fit to activity, enthalpy, and extensive phase equilibrium data. Relative to the previous Ag-Cu-In assessment, fit was improved while fewer parameters were used.

Tunable synthesis and acetylation of dendrimer-entrapped or dendrimer-stabilized gold-silver alloy nanoparticles.

PubMed

Liu, Hui; Shen, Mingwu; Zhao, Jinglong; Guo, Rui; Cao, Xueyan; Zhang, Guixiang; Shi, Xiangyang

2012-06-01

In this study, amine-terminated generation 5 poly(amidoamine) dendrimers were used as templates or stabilizers to synthesize dendrimer-entrapped or dendrimer-stabilized Au-Ag alloy nanoparticles (NPs) with different gold atom/silver atom/dendrimer molar ratios with the assistance of sodium borohydride reduction chemistry. Following a one-step acetylation reaction to transform the dendrimer terminal amines to acetyl groups, a series of dendrimer-entrapped or dendrimer-stabilized Au-Ag alloy NPs with terminal acetyl groups were formed. The formed Au-Ag alloy NPs before and after acetylation reaction were characterized using different techniques. We showed that the optical property and the size of the bimetallic NPs were greatly affected by the metal composition. At the constant total metal atom/dendrimer molar ratio, the size of the alloy NPs decreased with the gold content. The formed Au-Ag alloy NPs were stable at different pH (pH 5-8) and temperature (4-50°C) conditions. X-ray absorption coefficient measurements showed that the attenuation of the binary NPs was dependent on both the gold content and the surface modification. With the increase of gold content in the binary NPs, their X-ray attenuation intensity was significantly enhanced. At a given metal composition, the X-ray attenuation intensity of the binary NPs was enhanced after acetylation. Cytotoxicity assays showed that after acetylation, the cytocompatibility of Au-Ag alloy NPs was significantly improved. With the controllable particle size and optical property, metal composition-dependent X-ray attenuation characteristics, and improved cytocompatibility after acetylation, these dendrimer-entrapped or dendrimer-stabilized Au-Ag alloy NPs should have a promising potential for CT imaging and other biomedical applications. Copyright © 2012 Elsevier B.V. All rights reserved.

Pairing Heterocyclic Cations with closo-dodecafluorododecaborate (2-) Synthesis of Binary Heterocyclium (1+) Salts and a Ag4(heterocycle)8(4+) Salt of B12F12(2-)

DTIC Science & Technology

2011-01-01

10989). 13. SUPPLEMENTARY NOTES Journal article published in the Journal of Fluorine Chemistry, Vol. 132, Nov 2011. PA Case Number: 10989...TELEPHONE NUMBER (include area code) N/A Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. 239.18 Journal of Fluorine Chemistry 132 (2011... Fluorine Chemistry jo ur n al h o mep ag e: www .e lsev ier . c om / loc ate / f luo r1. Introduction Eight new binary salts that pair the icosahedral

High-resolution, far-ultraviolet study of Beta Draconis (G2 Ib-II) - Transition region structure and energy balance

NASA Technical Reports Server (NTRS)

Brown, A.; Jordan, C.; Stencel, R. E.; Linsky, J. L.; Ayres, T. R.

1984-01-01

High-resolution far ultraviolet spectra of the star Beta Draconis have been obtained with the IUE satellite. The observations and emission line data from the spectra are presented, the interpretation of the emission line widths and shifts is discussed, and the implications are given in terms of atmospheric properties. The emission measure distribution is derived, and density diagnostics involving both line ratios and line opacity arguments is investigated. The methods for calculating spherically symmetric models of the atmospheric structure are outlined, and several such models are presented. The extension of these models to log T(e) greater than 5.3 using the observed X-ray flux is addressed, the energy balance of an 'optimum' model is investigated, and possible models of energy transport and deposition are discussed.

The fourth outburst during the present active stage of symbiotic binary AG Dra

NASA Astrophysics Data System (ADS)

Galis, R.; Merc, J.; Vrastak, M.; Teyssier, F.; Lester, T.; Boyd, D.; Sims, W.; Leedjarv, L.

2018-04-01

The symbiotic system AG Dra regularly undergoes quiescent and active stages which consist of several outbursts repeating at about 360d interval (Galis et al. 2017, OEJV 180, 24). After seven years of flat quiescence following the 2006-08 major outbursts, in the late spring of 2015, AG Dra began rising again in brightness toward what appeared to be a new minor outburst (ATel #7582).

Binary titanium alloys as dental implant materials-a review.

PubMed

Liu, Xiaotian; Chen, Shuyang; Tsoi, James K H; Matinlinna, Jukka Pekka

2017-10-01

Titanium (Ti) has been used for long in dentistry and medicine for implant purpose. During the years, not only the commercially pure Ti but also some alloys such as binary and tertiary Ti alloys were used. The aim of this review is to describe and compare the current literature on binary Ti alloys, including Ti-Zr, Ti-In, Ti-Ag, Ti-Cu, Ti-Au, Ti-Pd, Ti-Nb, Ti-Mn, Ti-Mo, Ti-Cr, Ti-Co, Ti-Sn, Ti-Ge and Ti-Ga, in particular to mechanical, chemical and biological parameters related to implant application. Literature was searched using the PubMed and Web of Science databases, as well as google without limiting the year, but with principle key terms such as ' Ti alloy', 'binary Ti ', 'Ti-X' (with X is the alloy element), 'dental implant' and 'medical implant'. Only laboratory studies that intentionally for implant or biomedical applications were included. According to available literatures, we might conclude that most of the binary Ti alloys with alloying <20% elements of Zr, In, Ag, Cu, Au, Pd, Nb, Mn, Cr, Mo, Sn and Co have high potential as implant materials, due to good mechanical performance without compromising the biocompatibility and biological behaviour compare to cp-Ti.

Heteromorph ammonites from the Upper Campanian (Upper Cretaceous) Baculites cuneatus and Baculites reesidei zones of the Pierre Shale in Colorado, USA

USGS Publications Warehouse

Kennedy, W.J.; Cobban, W.A.; Scott, G.R.

2000-01-01

Calcareous sandstone concretions in the Upper Cretaceous Pierre Shale in Middle Park and in the Fort Collins area of Colorado in the U.S. Western Interior contain heteromorph ammonites of the families Nostoceratidae HYATT, 1894, and Diplomoceratidae SPATH, 1926. The following species are described: Nostoceras cf. N. approximans (CONRAD, 1855), Nostoceras cf. N. obtusum HOWARTH, 1965, N. larimerense sp. nov., Nostoceras cf. N. splendidum (SHUMARD, 1861). Didymoceras aurarium sp. nov., D. draconis (STEPHENSON, 1941), Cirroceras conradi (MORTON, 1841), Anaklinoceras minutum sp. nov., Solenoceras texanum (SHUMARD, 1861), Solenoceras cf. S. reesidei STEPHENSON, 1941, Lewyites oronensis (LEWY, 1969), and Lewyites? sp. All these species are migrants from the Gulf coastal region. Didymoceras draconis and Cirroceras conradi are also known from the Delaware-New Jersey area, and these two species, together with Solenoceras texanum are known from as far away as Israel.

Outburst Activity Driven by Evolved Pulsating Star in the Symbiotic Binary AG Dra

NASA Astrophysics Data System (ADS)

Gális, R.; Hric, L.; Leedjärv, L.

2015-12-01

The symbiotic system AG Dra regularly undergoes quiescent and active stages which consist of the series of individual outbursts. The period analysis of new and historical photometric data, as well as radial velocities, confirmed the presence of the two periods. The longer one around ≈ 550 d is related to the orbital motion and the shorter one ≈355 d could be due to pulsation of the cool component of AG Dra.

Serendipitous discovery of an irregular and a semi-regular type variable in the field of BY Draconis

NASA Astrophysics Data System (ADS)

Messina, S.; Marino, G.; Rodonò, M.; Cutispoto, G.

2000-12-01

We present new evidence of the optical variability of two red giant stars: HD 172468 and HK Dra, based on photometric and spectroscopic observations. These stars had been included as check stars in our photometric monitoring program of BY Dra and turned out to be variable. HD 172468, whereas almost constant for most of the time, suddenly started to drop in brightness to such a low level to become undetectable. We suspect that such an abrupt event may be an ``obscurational'' minimum, that is typical of eruptive RCB stars, or may be due to the variable extinction by circumstellar dust in a young Orion type object. HK Dra, already known as an irregular variable, is characterised by periodic flux modulation with season-to-season changes of the photometric period, as inferred from a periodogram analysis. It also shows changes of the light curve peak-to-peak amplitude and shape. Such a behaviour in giant stars is commonly found among semi-regular giants (SR) at the Asymptotic Giant Branch (AGB). Our radial velocity measurements rule out that HK Dra may be a close binary system.

Binary titanium alloys as dental implant materials—a review

PubMed Central

Liu, Xiaotian; Chen, Shuyang; Matinlinna, Jukka Pekka

2017-01-01

Abstract Titanium (Ti) has been used for long in dentistry and medicine for implant purpose. During the years, not only the commercially pure Ti but also some alloys such as binary and tertiary Ti alloys were used. The aim of this review is to describe and compare the current literature on binary Ti alloys, including Ti–Zr, Ti–In, Ti–Ag, Ti–Cu, Ti–Au, Ti–Pd, Ti–Nb, Ti–Mn, Ti–Mo, Ti–Cr, Ti–Co, Ti–Sn, Ti–Ge and Ti–Ga, in particular to mechanical, chemical and biological parameters related to implant application. Literature was searched using the PubMed and Web of Science databases, as well as google without limiting the year, but with principle key terms such as ‘ Ti alloy’, ‘binary Ti ’, ‘Ti-X’ (with X is the alloy element), ‘dental implant’ and ‘medical implant’. Only laboratory studies that intentionally for implant or biomedical applications were included. According to available literatures, we might conclude that most of the binary Ti alloys with alloying <20% elements of Zr, In, Ag, Cu, Au, Pd, Nb, Mn, Cr, Mo, Sn and Co have high potential as implant materials, due to good mechanical performance without compromising the biocompatibility and biological behaviour compare to cp-Ti. PMID:29026646

Rate dependent strengths of some solder joints

NASA Astrophysics Data System (ADS)

Williamson, D. M.; Field, J. E.; Palmer, S. J. P.; Siviour, C. R.

2007-08-01

The shear strengths of three lead-free solder joints have been measured over the range of loading rates 10-3 to ~105 mm min-1. Binary (SnAg), ternary (SnAgCu) and quaternary (Castin: SnAgCuSb) alloys have been compared to a conventional binary SnPb solder alloy. Results show that at loading rates from 10-3 to 102 mm min-1, all four materials exhibit a linear relationship between the shear strength and the loading rate when the data are plotted on a log-log plot. At the highest loading rate of 105 mm min-1, the strengths of the binary alloys were in agreement with extrapolations made from the lower loading rate data. In contrast, the strengths of the higher order alloys were found to be significantly lower than those predicted by extrapolation. This is explained by a change in failure mechanism on the part of the higher order alloys. Similar behaviour was found in measurements of the tensile strengths of solder joints using a novel high-rate loading tensile test. Optical and electron microscopy were used to examine the microstructures of interest in conjunction with energy dispersive x-ray analysis for elemental identification. The effect of artificial aging and reflow of the solder joints is also reported.

Precision modelling of M dwarf stars: the magnetic components of CM Draconis

NASA Astrophysics Data System (ADS)

MacDonald, J.; Mullan, D. J.

2012-04-01

The eclipsing binary CM Draconis (CM Dra) contains two nearly identical red dwarfs of spectral class dM4.5. The masses and radii of the two components have been reported with unprecedentedly small statistical errors: for M, these errors are 1 part in 260, while for R, the errors reported by Morales et al. are 1 part in 130. When compared with standard stellar models with appropriate mass and age (≈4 Gyr), the empirical results indicate that both components are discrepant from the models in the following sense: the observed stars are larger in R ('bloated'), by several standard deviations, than the models predict. The observed luminosities are also lower than the models predict. Here, we attempt at first to model the two components of CM Dra in the context of standard (non-magnetic) stellar models using a systematic array of different assumptions about helium abundances (Y), heavy element abundances (Z), opacities and mixing length parameter (α). We find no 4-Gyr-old models with plausible values of these four parameters that fit the observed L and R within the reported statistical error bars. However, CM Dra is known to contain magnetic fields, as evidenced by the occurrence of star-spots and flares. Here we ask: can inclusion of magnetic effects into stellar evolution models lead to fits of L and R within the error bars? Morales et al. have reported that the presence of polar spots results in a systematic overestimate of R by a few per cent when eclipses are interpreted with a standard code. In a star where spots cover a fraction f of the surface area, we find that the revised R and L for CM Dra A can be fitted within the error bars by varying the parameter α. The latter is often assumed to be reduced by the presence of magnetic fields, although the reduction in α as a function of B is difficult to quantify. An alternative magnetic effect, namely inhibition of the onset of convection, can be readily quantified in terms of a magnetic parameter δ≈B2/4πγpgas (where B is the strength of the local vertical magnetic field). In the context of δ models in which B is not allowed to exceed a 'ceiling' of 106 G, we find that the revised R and L can also be fitted, within the error bars, in a finite region of the f-δ plane. The permitted values of δ near the surface leads us to estimate that the vertical field strength on the surface of CM Dra A is about 500 G, in good agreement with independent observational evidence for similar low-mass stars. Recent results for another binary with parameters close to those of CM Dra suggest that metallicity differences cannot be the dominant explanation for the bloating of the two components of CM Dra.

Effect of deformation twin on toughness in magnesium binary alloys

NASA Astrophysics Data System (ADS)

Somekawa, Hidetoshi; Inoue, Tadanobu; Tsuzaki, Kaneaki

2015-08-01

The impact of alloying elements on toughness was investigated using eight kinds of Mg-0.3 at.% X (X = Al, Ag, Ca, Gd, Mn, Pb, Y and Zn) binary alloys with meso-grained structures. These binary alloys had an average grain size of approximately 20 μm. The fracture toughness and crack propagation behaviour were influenced by the alloying elements; the Mg-Ag and Mg-Pb alloys had the highest and the lowest toughness amongst the alloys, respectively, irrespective of presence in their ? type deformation twins. The twin boundaries affected the crack propagation behaviour in most of the alloys; in contrast, not only was the fracture related to the twin boundaries, but also the intergranular fracture occurred in the alloys that included rare earth elements. The influential factor for toughness in the meso- and the coarse-grained magnesium alloys, which readily formed deformation twins during plastic deformation, was not the change in lattice parameter with chemical composition, but the twin boundary segregation energy.

Evolution of the symbiotic binary system AG Pegasi - The slowest classical nova eruption ever recorded

NASA Technical Reports Server (NTRS)

Kenyon, Scott J.; Mikolajewska, Joanna; Mikolajewski, Maciej; Polidan, Ronald S.; Slovak, Mark H.

1993-01-01

We present an analysis of new and existing photometric and spectroscopic observations of the ongoing eruption in the symbiotic star AG Pegasi, showing that this binary has evolved considerably since the turn of the century. Recent dramatic changes in both the UV continuum and the wind from the hot component allow a more detailed analysis than in previous papers. AG Peg is composed of a normal M3 giant and a hot, compact star embedded in a dense, ionized nebula. The hot component powers the activity observed in this system, including a dense wind and a photoionized region within the outer atmosphere of the red giant. The hot component contracted in radius at roughly constant luminosity from 1850 to 1985. Its bolometric luminosity declined by a factor of about 4 during the past 5 yr. Both the mass loss rate from the hot component and the emission activity decreased in step with the hot component's total luminosity, while photospheric radiation from the red giant companion remained essentially constant.

Control of nanoscale atomic arrangement in multicomponent thin films by temporally modulated vapour fluxes

NASA Astrophysics Data System (ADS)

Sarakinos, Kostas

2016-09-01

Synthesis of multicomponent thin films using vapor fluxes with a modulated deposition pattern is a potential route for accessing a wide gamut of atomic arrangements and morphologies for property tuning. In the current study, we present a research concept that allows for understanding the combined effect of flux modulation, kinetics and thermodynamics on the growth of multinary thin films. This concept entails the combined use of thin film synthesis by means of multiatomic vapor fluxes modulated with sub-monolayer resolution, deterministic growth simulations and nanoscale microstructure probes. Using this research concept we study structure formation within the archetype immiscible Ag-Cu binary system showing that atomic arrangement and morphology at different length scales is governed by diffusion of near-surface Ag atoms to encapsulate 3D Cu islands growing on 2D Ag layers. Moreover, we explore the relevance of the mechanism outlined above for morphology evolution and structure formation within the miscible Ag-Au binary system. The knowledge generated and the methodology presented herein provides the scientific foundation for tailoring atomic arrangement and physical properties in a wide range of miscible and immiscible multinary systems.

Chromospherically active stars. 12: ADS 11060 C: A double lined K dwarf binary in a quintuple system

NASA Technical Reports Server (NTRS)

Fekel, Francis C.; Henry, Gregory W.; Hampton, Melissa L.; Fried, Robert; Morton, Mary D.

1994-01-01

ADS 11060 C is a double lined spectroscopic binary with a period of 25.7631 days and an eccentricity of 0.565. Spectral types of the two stars are estimated as K7 V and MO V with a magnitude difference of about 0.55 mag in V. The stars appear to be somewhat metal rich with respect to the Sun. Despite the relatively large masses of 0.53 and 0.51 solar mass, our photometric observations find no evidence for eclipses and we estimate an inclination of 77 deg plus or minus 11 deg. ADS 11060 C is, however, photometrically variable with a period of 9 plus or minus 1 day and an amplitude of 0.05 mag in V. Thus, it is a newly identified BY Draconis variable. The center-of-mass velocity of ADS 11060 C and an estimated parallax of 0.030 sec support its physical association with ADS 11060 AB, making this a quintuple system. The projected separation of the AB-C system is nearly 1200 AU. Although the log lithium abundances of the two components of ADS 11060 C are only upper limits, less than or equal to -0.14, lithium abundances of the AB-C components appear to be consistent with those of similar stars in the alpha Persei and Pleiades clusters, suggesting an age of about 70 Myr for ADS 11060 AB-C. The system is a possible member of the Pleiades moving group. Listed as an optical counterpart to a source in the ROSAT Wide Field Camera extreme-ultraviolet bright source catalog, both ADS 11060 AB and C may contribute to the observed flux.

Extrasolar planet detection by binary stellar eclipse timing: evidence for a third body around CM Draconis

NASA Astrophysics Data System (ADS)

Deeg, H. J.; Ocaña, B.; Kozhevnikov, V. P.; Charbonneau, D.; O'Donovan, F. T.; Doyle, L. R.

2008-03-01

Aims:Our objective is to elucidate the physical process that causes the observed observed-minus-calculated (O-C) behavior in the M4.5/M4.5 binary CM Dra and to test for any evidence of a third body around the CM Dra system. Methods: New eclipse minimum timings of CM Dra were obtained between the years 2000 and 2007. The O-C times of the system are fitted against several functions, representing different physical origins of the timing variations. Results: Using our observational data in conjunction with published timings going back to 1977, a clear non-linearity in O-C times is apparent. An analysis using model-selection statistics gives about equal weight to a parabolic and to a sinusoidal fitting function. Attraction from a third body, either at large distance in a quasi-constant constellation across the years of observations or from a body on a shorter orbit generating periodicities in O-C times is the most likely source of the observed O-C times. The white dwarf GJ 630.1B, a proper motion companion of CM Dra, can however be rejected as the responsible third body. Also, no further evidence of the short-periodic planet candidate described by Deeg et al. (2000, A&A, 358, L5) is found, whereas other mechanisms, such as period changes from stellar winds or Applegate's mechanism can be rejected. Conclusions: A third body, being either a few-Jupiter-mass object with a period of 18.5 ± 4.5 years or an object in the mass range of 1.5 M_jup to 0.1 M⊙ with periods of hundreds to thousands of years is the most likely origin of the observed minimum timing behavior.

The Effect of Palladium Additions on the Solidus/Liquidus Temperatures and Wetting Properties of Ag-CuO Based Air Brazes

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

Darsell, Jens T.; Weil, K. Scott

2007-05-16

As a means of increasing the use temperature of ceramic-ceramic and ceramic-metal air brazes, palladium was investigated as possible ternary addition to the currently employed silver - copper oxide system. The silver component was directly substituted with palladium to form the following series of alloys: (100-y)[(100-z)Pd - (z)Ag] - (y)CuOx where y = 0 - 34 mol% CuOx, z = 50 - 100 mol% silver, and x = 0, 0.5, and 1, denoting copper metal, Cu2O, or CuO. From differential scanning calorimetry, it was determined that the addition of palladium causes an increase in the solidus and liquidus temperatures ofmore » the resulting Pd-Ag-CuO brazes. In general, the liquidus was found to increase by approximately 220°C for the (100-y)(25Pd - 75Ag) - (z)CuOx filler metal compositions relative to comparable Ag-CuOx alloys. Likewise, the solidus was found to increase for these alloys, respectively by 185°C and 60°C, respectively for CuOx contents of y = 0 - 1mol% and 4 - 10 mol%. For the (100-y)(50Pd - 50Ag) - (y)CuOx alloys, the solidus increased between 280 - 390°C over a copper oxide compositional range of x = 0 to 8 mol%. It was determined from sessile drop experiments conducted on alumina substrates that in all cases the palladium causes an increase in the wetting angle relative to the corresponding binary braze. Alloy compositions of (100-y)(25Pd - 75Ag) - (y)CuOx displayed increased wetting angles of 5-20° relative to comparable binary compositions. (100-y)(50Pd - 50Ag) - (y)CuOx alloys exhibited an increase in contact angle of 10-60° and compositions containing less than 10 mol% CuOx were not able to wet the substrate. Scanning electron microscopy indicated that the microstructure of the braze consists of discrete CuOx precipitates in an alloyed silver-palladium matrix. In both the binary and ternary filler metal formulations, a reaction layer consisting of CuAlO2 was observed along the interface with the alumina substrate. This reaction product appears to be beneficial in promoting wetting by the remaining braze filler metal. However the formation of this layer is hindered as the concentration of palladium in the filler metal is increased, which appears to be the primary cause of poor wettability in these compositions, as indicated by the substantial amount of porosity found along the braze/substrate interface.« less

Delicate Ag/V2O5/TiO2 ternary nanostructures as a high-performance photocatalyst

NASA Astrophysics Data System (ADS)

Zhu, Xiao-Dong; Zheng, Ya-Lun; Feng, Yu-Jie; Sun, Ke-Ning

2018-02-01

Here we report, for the first time, delicate ternary nanostructures consisting of TiO2 nanoplatelets co-doped with Ag and V2O5 nanoparticles. The relationship between the composition and the morphology is systematically studied. We find a remarkable synergistic effect among the three components, and the resulting delicate Ag/V2O5/TiO2 ternary nanostructures exhibit a superior photocatalytic performance over neat TiO2 nanoplatelets as well as Ag/TiO2 and V2O5/TiO2 binary nanostructures for the degradation of methyl orange. We believe our delicate Ag/V2O5/TiO2 ternary nanostructures may lay a basis for developing next-generating, high-performance composite photocatalysts.

Apsidal rotation in the eclipsing binary AG Persei

NASA Technical Reports Server (NTRS)

Koch, Robert H.; Woodward, Edith J.

1987-01-01

New three-filter light curves of AG Per are given. These yield times of minimum light in accord with the known rate of apsidal rotation but do not improve that rate. These light curves and all other published historical ones have been treated with the code EBOP and are shown to give largely consistent geometric and photometric parameters no matter which orientation of the orbit is displayed to the observer.

Tailoring Morphology and Size of Microstructure and Tensile Properties of Sn-5.5 wt.%Sb-1 wt.%(Cu,Ag) Solder Alloys

NASA Astrophysics Data System (ADS)

Dias, Marcelino; Costa, Thiago A.; Soares, Thiago; Silva, Bismarck L.; Cheung, Noé; Spinelli, José E.; Garcia, Amauri

2018-02-01

Transient directional solidification experiments, and further optical and scanning electron microscopy analyses and tensile tests, allowed the dependence of tensile properties on the micromorphology and length scale of the dendritic/cellular matrix of ternary Sn-5.5Sb-1Ag and Sn-5.5Sb-1Cu alloys to be determined. Extensive ranges of cooling rates were obtained, which permitted specific values of cooling rate for each sample examined along the length of the casting to be attributed. Very broad microstructural length scales were revealed as well as the presence of either cells or dendrites for the Ag-containing alloy. Hereafter, microstructural spacing values such as the cellular spacing, λ c, and the primary dendritic spacing, λ 1, may be correlated with thermal solidification parameters, that is, the cooling rate and the growth rate. While, for the Cu-containing Sn-Sb alloy, the β-Sn matrix is characterized only by the presence of dendritic arrangements, the Ag-containing Sn-Sb alloy is shown to have high-velocity β-Sn cells associated with high cooling rate regions, i.e., positions closer to the bottom of the alloy casting, with the remaining positions being characterized by a complex growth of β-Sn dendrites. Minor additions of Cu and Ag increase both the yield and ultimate tensile strengths when compared with the corresponding values of the binary Sn-5.5Sb alloy, with a small reduction in ductility. This has been attributed to the homogeneous distribution of the Ag3Sn and Cu6Sn5 intermetallic particles related to smaller λ 1 characterizing the dendritic zones of the ternary Sn-Sb-(Cu,Ag) alloys. In addition, the Ag-modified Sn-Sb alloy exhibited an initial wetting angle consistent with that characterizing the binary Sn-5.5Sb alloy.

Fluxless Bonding Processes Using Silver-Indium System for High Temperature Electronics and Silver Flip-Chip Interconnect Technology

NASA Astrophysics Data System (ADS)

Wu, Yuan-Yun

In this dissertation, fluxless silver (Ag)-indium (In) binary system bonding and Ag solid-state bonding are used between different bonded pairs which have large thermal expansion coefficient (CTE) mismatch and flip-chip interconnect bonding application. In contrast to the conventional soldering process, fluxless bonding technique eliminates contamination and reliability problems caused by flux to fabricate high quality joints. There are two section are reported. In the first section, the reactions of Ag-In binary system are presented. In the second section, the high melting temperature, thermal and electrical conductivity joint materials bonding by either Ag-In binary system bonding or solid-state bonding processes for different bonded pairs and flip-chip application are designed, developed, and reported. Our group have studied Ag-In system for several years and developed the bonding processes successfully. However, the detailed reactions of Ag and In were seldom studied. To design a proper bonding structure, it is necessary to understand the reaction between Ag and In. The systematic experiments were performed to investigate these reactions. A 40 um Ag layer was electroplated on copper (Cu) substrates, followed by indium layers of 1, 3, 5, 10, and 15 um, respectively. The samples were annealed at 180 °C in 0.1 torr vacuum. For samples with In thickness less than 5 mum, the joint compositions are Ag2In only (1 um) or AgIn2, Ag2In, and Ag solid solution (Ag) after annealing. No indium is identified. For 10 and 15 um thick In samples, In covers almost over the entire sample surface after annealing. Later, an Ag layer was annealed at 450 °C for 3 hours to grow Ag grains, followed by plating 10 um In and annealing at 180 °C. By annealing Ag before plating In, more In is kept in the structure during annealing at 180 °C. Based on above results, for those designs with In thinner than 5 um, the Ag layer needs to be annealed, prior to In plating in order to make a successful bonding. In this section, we further studied the Ag-In bonding and solid-state bonding for different bonded pairs and flip-chip application. For the silicon (Si) and aluminum (Al) pair, Al has been used as the material for interconnect pads on the ICs. However, its high CTE (23 x 10-6/°C) and non-solderable property limit its applications in electronic products. To overcome these problems, a fluxless Ag-In bonding was developed. Al was deposited Cr/Cu layer on the surface by E-beam evaporator to make it solderable. 15 um of Ag and 8 um of In were sequentially plated on the Al substrates and 15 um of Ag was on Si chips with Cr/Au coating layer. The bonding was performed at 180 °C in 0.1 torr vacuum. The joint consists of Ag/(Ag)/Ag2In/(Ag)/Ag. The joint can achieve a solidus temperature of beyond 600 °C. From shear test results, the shear strengths far exceed the requirement in MIL-STD-883H. Al is not considered as a favorable substrate material because it is not solderable and has a high CTE. The new method presented in this thesis seems to have surmounted these two challenges. Since Ag2In is weak inside the joint in Ag-In system, an annealed process was used to convert the joints into Ag solid solution (Ag) to increase the joint strength and ductility. Two copper (Cu) substrates were bonded at 180 °C without flux. Bonding samples were annealed at 200 °C for 1,000 hours (first design) and at 250 °C for 350 hours (second design), respectively. Scanning electron microscope with energy dispersive X-ray (EDX) analysis results indicate that the joint of the first design is an alloy of mostly (Ag) with micron-size Ag2In and Ag3In regions, and that of second design has converted to a single (Ag) phase. Shear test results show that the breaking forces far exceed the requirement in MIL-STD-883H. The joint solidus temperatures are 600 °C and 800 °C for the first and second designs, respectively. The research results have shown that high-strength and high temperature joints can be manufactured using fluxless low temperature processes with the Ag-In system and are valuable in developing high temperature package. (Abstract shortened by UMI.).

Quasi-Periodic Long-Term Quadrature Light Variability in Early Type Interacting Binary Systems

NASA Astrophysics Data System (ADS)

Peters, Geraldine Joan

2015-08-01

Four years of Kepler observations have revealed a class of Algol-type binaries in which the relative brightness of the quadrature light varies from > 1 to <1 on a time scale of about 100-400 days. The behavior pattern is quasi-periodic. We call these systems L/T (leading hemisphere/ trailing hemisphere) variables. Although L/T inequality in eclipsing binaries has been noted from ground-based photometry by several observers since the early 1950s, the regular or quasi-regular switching between maxima is new. Twenty L/T systems have so far been found in the Kepler database and at least three classes of L/T behavior have been identified. In this presentation I will give an update on the L/T phenomenon gleaned from the Kepler and K2 databases. The Kepler and K2 light curves are being analyzed with the 2015 version of the Wilson-Devinney (WD) program that includes major improvements in modeling star spots (i.e. spot motions due to drift and stellar rotation and spot growth and decay). The prototype L/T variable is WX Draconis (A8V + K0IV, P=1.80 d) which shows L/ T light variations of 2-3%. The primary is a delta Scuti star with a dominant pulsation period of 41 m. Preliminary analysis of the WX Dra data suggests that the L/T variability can be fit with either an accretion hot spot on the primary (T = 2.3 Tphot) that jumps in longitude or a magnetic cool spotted region on the secondary. If the latter model is correct the dark region must occupy at least 20% of the surface of the facing hemisphere of the secondary if it is completely black, or a larger area if not completely black. In both hot and cool spot scenarios magnetic fields must play a role in the activity. Support from NASA grants NNX11AC78G and NNX12AE44G and USC’s Women in Science and Engineering (WiSE) program is greatly appreciated.

[Construction of a plant effective expression vector containing the gene of hepatitis B virus surface antigen].

PubMed

Lin, Bing-Ying; Jin, Zhi-Qiang; Li, Mei

2006-11-01

To construct a plant effective expression vector driven by a fruit specific promoter for the expression of hepatitis B virus surface antigen (HBsAg), to further improve the expression of exogenous gene in plant, and to prepare for the development of an effective anti-hepatitis vaccine. Tomato fruit-specific promoters' gene 2A12 and E8 were respectively introduced to pBPFOmega7 to form pB2A12 and pBE8. The DNA fragment containing HBsAg-s gene from plasmid YEP-HBs was inserted respectively into pB2A12 and pBE8 to form pB2A12-HBs and pBE8-HBs. The fragment containing "p35S+2A12+Omega+HBsAg-s+Tnos" of the pB2A12-HBs was sub-cloned into plasmid pCAMBIA1301 to yield the reconstructed plant binary expression plasmid pCAM2A12-HBs, and the fragment containing "p35S+E8+Omega+HBsAg-s+Tnos" of the pBE8-HBs was sub-cloned into plasmid pCAMBIA1301 to yield the plasmid pCAME8-HBs. The inserted gene HBsAg and fruit-specific promoters in the reconstructed plant binary expression vectors were confirmed by sequencing. Then, pCAM2A12-HBs and pCAME8-HBs were directly introduced into Agrobacterium tumefaciens strain EHA105. Digestion with restriction enzymes proved that all recombinant vectors had the inserts with expected length of the target fragments, and the sequencing results were confirmed correct. In this study, plant expression vector containing HBsAg gene driven by fruit specific promoter and CaMV35s promoter was successfully constructed.

EK Draconis. Magnetic activity in the photosphere and chromosphere

NASA Astrophysics Data System (ADS)

Järvinen, S. P.; Berdyugina, S. V.; Korhonen, H.; Ilyin, I.; Tuominen, I.

2007-09-01

Context: As a young solar analogue, EK Draconis provides an opportunity to study the magnetic activity of the infant Sun. Aims: We present three new surface temperature maps of EK Draconis and compare them with previous results obtained from long-term photometry. Furthermore, we determined a set of stellar parameters and compared the determined values with the corresponding solar values. Methods: Atmospheric parameters were determined by comparing observed and synthetic spectra calculated with stellar atmosphere models. Surface temperature maps were obtained using the Occamian approach inversion technique. The differential rotation of EK Dra was estimated using two different methods. Results: A detailed model atmosphere analysis of high resolution spectra of EK Dra has yielded a self-consistent set of atmospheric parameters: T_eff = 5750 K, log g = 4.5, [M/H] = 0.0, ξt = 1.6 km s-1. The evolutionary models imply that the star is slightly more massive than the Sun and has an age between 30-50 Myr, which agrees with the determined lithium abundance of log N(Li) = 3.02. Moreover, the atmospheric parameters, as well as the wings of the Ca ii 8662 Å, indicate that the photosphere of EK Dra is very similar to the one of the present Sun, while their chromospheres differ. There also seems to be a correlation between magnetic features seen in the photosphere and chromosphere. The temperature images reveal spots of only 500 K cooler than the quiet photosphere. The mean spot latitude varies with time. The obtained differential rotation is very small, but the sign of it supports solar type differential rotation on EK Dra. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. Table [see full text] and Figs. [see full text] and [see full text] are only available in electronic form at http://www.aanda.org

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

Lee, Min Ho; Rhyee, Jong-Soo, E-mail: jsrhyee@khu.ac.kr

We investigated the thermoelectric properties of PbTe/Ag{sub 2}Te bulk composites, synthesized by hand milling, mixing, and hot press sintering. From x-ray diffraction and energy dispersive x-ray spectroscopy measurements, we observed Ag{sub 2}Te phase separation in the PbTe matrix without Ag atom diffusion. In comparison with previously reported pseudo-binary (PbTe){sub 1−x}(Ag{sub 2}Te){sub x} composites, synthesized by high temperature phase separation, the PbTe/Ag{sub 2}Te bulk composites fabricated with a low temperature phase mixing process give rise to p-type conduction of carriers with significantly decreased electrical conductivity. This indicates that Ag atom diffusion in the PbTe matrix changes the sign of the Seebeckmore » coefficient to n-type and also increases the carrier concentration. Effective p-type doping with low temperature phase separation by mixing and hot press sintering can enhance the thermoelectric performance of PbTe/Ag{sub 2}Te bulk composites, which can be used as a p-type counterpart of n-type (PbTe){sub 1−x}(Ag{sub 2}Te){sub x} bulk composites.« less

ZnO/Ag/CdO nanocomposite for visible light-induced photocatalytic degradation of industrial textile effluents.

PubMed

Saravanan, R; Mansoob Khan, M; Gupta, Vinod Kumar; Mosquera, E; Gracia, F; Narayanan, V; Stephen, A

2015-08-15

A ternary ZnO/Ag/CdO nanocomposite was synthesized using thermal decomposition method. The resulting nanocomposite was characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, UV-Vis spectroscopy, and X-ray photoelectron spectroscopy. The ZnO/Ag/CdO nanocomposite exhibited enhanced photocatalytic activity under visible light irradiation for the degradation of methyl orange and methylene blue compared with binary ZnO/Ag and ZnO/CdO nanocomposites. The ZnO/Ag/CdO nanocomposite was also used for the degradation of the industrial textile effluent (real sample analysis) and degraded more than 90% in 210 min under visible light irradiation. The small size, high surface area and synergistic effect in the ZnO/Ag/CdO nanocomposite is responsible for high photocatalytic activity. These results also showed that the Ag nanoparticles induced visible light activity and facilitated efficient charge separation in the ZnO/Ag/CdO nanocomposite, thereby improving the photocatalytic performance. Copyright © 2015 Elsevier Inc. All rights reserved.

Outburst activity of the symbiotic system AG Dra

NASA Astrophysics Data System (ADS)

Hric, L.; Gális, R.; Leedjärv, L.; Burmeister, M.; Kundra, E.

2014-09-01

AG Dra is a well-known bright symbiotic binary with a white dwarf and a pulsating red giant. Long-term photometry monitoring and a new behaviour of the system are presented. A detailed period analysis of photometry as well as spectroscopy was carried out. In the system of AG Dra, two periods of variability are detected. The longer one around 550 d is related to the orbital motion and the shorter one around 355 d was interpreted as pulsations of the red giant in our previous article. In addition, the active stages change distinctively, but the outbursts are repeated with periods from 359-375 d.

Outburst activity of the symbiotic binary AG Dra

NASA Astrophysics Data System (ADS)

Gális, R.; Merc, J.; Leedjärv, L.

2017-04-01

AG Dra regularly undergoes quiescent and active stages which consist of a series of individual outbursts repeating at about a one-year interval. After seven years of flat quiescence following the 2006-08 major outbursts, in the late spring of 2015, AG Dra begun rising again in brightness toward what appeared to be a new minor outburst. The recent outburst activity of AG Dra was definitely confirmed by a more prominent outburst in April 2016. The photometric and spectroscopic observations suggest that these outbursts are of the hot type. Such behaviour is quite unusual, because the major outbursts in the beginning of active stages are usually cool. Can we expect the major cool or minor hot outburst during the spring of 2017? AG Dra demonstrates the importance of long-term monitoring of symbiotic stars in order to disentangle the nature and mechanisms of their active stages and outbursts.

An approximate formula for recalescence in binary eutectic alloys

NASA Technical Reports Server (NTRS)

Ohsaka, K.; Trinh, E. H.

1993-01-01

In alloys, solidification takes place along various paths which may be ascertained via phase diagrams; while there would be no single formula applicable to all alloys, an approximate formula for a specific solidification path would be useful in estimating the fraction of the solid formed during recalescence. A formulation is here presented of recalescence in binary eutectic alloys. This formula is applied to Ag-Cu alloys which are of interest in containerless solidification, due to their formation of supersaturated solutions.

First Principles Calculations of Transition Metal Binary Alloys: Phase Stability and Surface Effects

NASA Astrophysics Data System (ADS)

Aspera, Susan Meñez; Arevalo, Ryan Lacdao; Shimizu, Koji; Kishida, Ryo; Kojima, Kazuki; Linh, Nguyen Hoang; Nakanishi, Hiroshi; Kasai, Hideaki

2017-06-01

The phase stability and surface effects on binary transition metal nano-alloy systems were investigated using density functional theory-based first principles calculations. In this study, we evaluated the cohesive and alloying energies of six binary metal alloy bulk systems that sample each type of alloys according to miscibility, i.e., Au-Ag and Pd-Ag for the solid solution-type alloys (SS), Pd-Ir and Pd-Rh for the high-temperature solid solution-type alloys (HTSS), and Au-Ir and Ag-Rh for the phase-separation (PS)-type alloys. Our results and analysis show consistency with experimental observations on the type of materials in the bulk phase. Varying the lattice parameter was also shown to have an effect on the stability of the bulk mixed alloy system. It was observed, particularly for the PS- and HTSS-type materials, that mixing gains energy from the increasing lattice constant. We furthermore evaluated the surface effects, which is an important factor to consider for nanoparticle-sized alloys, through analysis of the (001) and (111) surface facets. We found that the stability of the surface depends on the optimization of atomic positions and segregation of atoms near/at the surface, particularly for the HTSS and the PS types of metal alloys. Furthermore, the increase in energy for mixing atoms at the interface of the atomic boundaries of PS- and HTSS-type materials is low enough to overcome by the gain in energy through entropy. These, therefore, are the main proponents for the possibility of mixing alloys near the surface.

Draco

NASA Astrophysics Data System (ADS)

Murdin, P.

2000-11-01

(the Dragon; abbrev. Dra, gen. Draconis; area 1083 sq. deg.) A northern constellation which lies between Ursa Major and Cepheus, and encloses Ursa Minor on three sides. The center of the constellation culminates at midnight in May, though part of it is on the meridian from mid-February to late July. Draco represents the dragon Ladon in Greek mythology, which guarded the golden apple tree that was...

Higher-efficiency photoelectrochemical electrodes of titanium dioxide-based nanoarrays sensitized simultaneously with plasmonic silver nanoparticles and multiple metal sulfides photosensitizers

NASA Astrophysics Data System (ADS)

Guo, Keying; Liu, Zhifeng; Han, Jianhua; Zhang, Xueqi; Li, Yajun; Hong, Tiantian; Zhou, Cailou

2015-07-01

This paper describes a novel design of high-efficiency photoelectrochemical water splitting electrode, i.e., ordered TiO2 nanorod arrays (NRs) sensitized simultaneously with noble metal (Ag), binary metal sulfides (Ag2S) and ternary metal sulfides (Ag3CuS2) multiple photosensitizers for the first time. The TiO2/Ag/Ag2S/Ag3CuS2 NRs heterostructure is successfully synthesized through successive ion layer adsorption and reaction (SILAR) and a simple ion-exchange process based on ionic reaction mechanism. On the basis of an optimal quantity of Ag, Ag2S and Ag3CuS2 nanoparticles, such TiO2/Ag/Ag2S/Ag3CuS2 NRs exhibit a higher photoelectrochemical activity ever reported for TiO2-based nanoarrays in PEC water splitting, the photocurrent density is up to 9.82 mA cm-2 at 0.47 V versus Ag/AgCl, respectively. This novel architecture is able to increase electron collection efficiency and suppress carrier recombination via (i) a higher efficiency of light-harvesting through these multiple photosensitizers (Ag, Ag2S and Ag3CuS2); (ii) the efficient separation of photo-induced electrons and holes due to the direct electrical pathways; (iii) the surface plasmon resonance (SPR) effect of Ag nanoparticles, which enhances the efficient charge separation and high carrier mobility. This work is useful to explore feasible routes to further enhance the performance of oxide semiconductors for PEC water splitting to produce clean H2 energy.

Determination of 200 °C Isothermal Section of Al-Ag-Ga Phase Diagram by Microanalysis, X-ray Diffraction, Hardness and Electrical Conductivity Measurements

NASA Astrophysics Data System (ADS)

Premović, Milena; Tomović, Milica; Minić, Duško; Manasijević, Dragan; Živković, Dragana; Ćosović, Vladan; Grković, Vladan; Đorđević, Aleksandar

2017-04-01

Ternary Al-Ag-Ga system at 200 °C was experimentally and thermodynamically assessed. Isothermal section was extrapolated using optimized thermodynamic parameters for constitutive binary systems. Microstructure and phase composition of the selected alloy samples were analyzed using light microscopy, scanning electron microscopy combined with energy-dispersive spectrometry and x-ray powder diffraction technique. The obtained experimental results were found to be in a close agreement with the predicted phase equilibria. Hardness and electrical conductivity of the alloy samples from four vertical sections Al-Ag80Ga20, Al-Ag60Ga40, Ag-Al80Ga20 and Ag-Al60Ga40 of the ternary Al-Ag-Ga system at 200 °C were experimentally determined using Brinell method and eddy current measurements. Additionally, hardness of the individual phases present in the microstructure of the studied alloy samples was determined using Vickers microhardness test. Based on experimentally obtained results, isolines of Brinell hardness and electrical conductivity were calculated for the alloys from isothermal section of the ternary Al-Ag-Ga system at 200 °C.

Antibacterial and Antimycotic Activity of Cotton Fabrics, Impregnated with Silver and Binary Silver/Copper Nanoparticles

NASA Astrophysics Data System (ADS)

Eremenko, A. M.; Petrik, I. S.; Smirnova, N. P.; Rudenko, A. V.; Marikvas, Y. S.

2016-01-01

Effective method of obtaining of the bactericidal bandage materials by impregnation of cotton fabric by aqueous solutions of silver and copper salts followed by a certain regime of heat treatment is developed. The study of obtained materials by methods of optical spectroscopy, electron microscopy, and X-ray phase analysis showed the formation of crystalline silver nanoparticles (NPs) and bimetallic Ag/Cu composites with the corresponding surface plasmon resonance (SPR) bands in the absorption spectra. High antimicrobial and antimycotic properties of tissues with low concentrations of Ag and Ag/Cu nanoparticles (Ag/Cu NPs) (in the range 0.06-0.25 weight percent (wt%) for Ag and 0.015-0.13 wt% for Ag/Cu) is confirmed in experiments with a wide range of multidrug-resistant bacteria and fungi: Escherichia coli, Enterobacter aerogenes, Proteus mirabilis, Klebsiella pneumoniae, Candida albicans yeasts, and micromycetes . Textile materials with Ag NPs demonstrate high antibacterial activity, while fabrics doped with bimetallic composite Ag/Cu have pronounced antimycotic properties. Bactericidal and antifungal properties of the obtained materials do not change after a washing. Production of such materials is extremely fast, convenient, and cost-effective.

Single-step solvothermal synthesis of mesoporous Ag-TiO2-reduced graphene oxide ternary composites with enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Arif Sher Shah, Md. Selim; Zhang, Kan; Park, A. Reum; Kim, Kwang Su; Park, Nam-Gyu; Park, Jong Hyeok; Yoo, Pil J.

2013-05-01

With growing interest in the photocatalytic performance of TiO2-graphene composite systems, the ternary phase of TiO2, graphene, and Ag is expected to exhibit improved photocatalytic characteristics because of the improved recombination rate of photogenerated charge carriers and potential contribution of the generation of localized surface plasmon resonance at Ag sites on a surface of the TiO2-graphene binary matrix. In this work, Ag-TiO2-reduced graphene oxide ternary nanocomposites were successfully synthesized by a simple solvothermal process. In a single-step synthetic procedure, the reduction of AgNO3 and graphene oxide and the hydrolysis of titanium tetraisopropoxide were spontaneously performed in a mixed solvent system of ethylene glycol, N,N-dimethylformamide and a stoichiometric amount of water without resorting to the use of typical reducing agents. The nanocomposites were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, along with different microscopic and spectroscopic techniques, enabling us to confirm the successful reduction of AgNO3 and graphite oxide to metallic Ag and reduced graphene oxide, respectively. Due to the highly facilitated electron transport of well distributed Ag nanoparticles, the synthesized ternary nanocomposite showed enhanced photocatalytic activity for degradation of rhodamine B dye under visible light irradiation.With growing interest in the photocatalytic performance of TiO2-graphene composite systems, the ternary phase of TiO2, graphene, and Ag is expected to exhibit improved photocatalytic characteristics because of the improved recombination rate of photogenerated charge carriers and potential contribution of the generation of localized surface plasmon resonance at Ag sites on a surface of the TiO2-graphene binary matrix. In this work, Ag-TiO2-reduced graphene oxide ternary nanocomposites were successfully synthesized by a simple solvothermal process. In a single-step synthetic procedure, the reduction of AgNO3 and graphene oxide and the hydrolysis of titanium tetraisopropoxide were spontaneously performed in a mixed solvent system of ethylene glycol, N,N-dimethylformamide and a stoichiometric amount of water without resorting to the use of typical reducing agents. The nanocomposites were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, along with different microscopic and spectroscopic techniques, enabling us to confirm the successful reduction of AgNO3 and graphite oxide to metallic Ag and reduced graphene oxide, respectively. Due to the highly facilitated electron transport of well distributed Ag nanoparticles, the synthesized ternary nanocomposite showed enhanced photocatalytic activity for degradation of rhodamine B dye under visible light irradiation. Electronic supplementary information (ESI) available: XRD of GO, EDX analysis of AgTG composites, tables show the size of graphitic domains and peak area analysis, dye adsorption plot, UV-visible absorption spectra of dye at different times, and plots of ln(Ct/C0) vs. time with the corresponding fitting curves of different samples. See DOI: 10.1039/c3nr00579h

IX Draconis - a curious ER UMa-type dwarf nova

NASA Astrophysics Data System (ADS)

Otulakowska-Hypka, M.; Olech, A.; de Miguel, E.; Rutkowski, A.; Koff, R.; Bąkowska, K.

2013-02-01

We report results of an extensive worldwide observing campaign devoted to a very active dwarf nova star - IX Draconis. We investigated photometric behaviour of the system to derive its basic outburst properties and understand peculiarities of IX Draconis as well as other active cataclysmic variables, in particular dwarf novae of the ER UMa type. In order to measure fundamental parameters of the system, we carried out analyses of the light curve, O - C diagram, and power spectra. During over two months of observations, we detected two superoutbursts and several normal outbursts. The V magnitude of the star varied in the range 14.6-18.2 mag. Superoutbursts occur regularly with the supercycle length (Psc) of 58.5 ± 0.5 d. When analysing data over the past 20 years, we found that Psc is increasing at a rate of dot{P} = 1.8 × 10^{-3}. Normal outbursts appear to be irregular, with typical occurrence times in the range 3.1-4.1 d. We detected a double-peaked structure of superhumps during superoutburst, with the secondary maximum becoming dominant near the end of the superoutburst. The mean superhump period observed during superoutbursts is Psh = 0.066982(36) d (96.45 ± 0.05 min), which is constant over the last two decades of observations. Based on the power spectrum analysis, the evaluation of the orbital period was problematic. We found two possible values: the first one, 0.066 41(3) d (95.63 ± 0.04 min), which is in agreement with previous studies and our O - C analysis [0.06646(2) d, 95.70 ± 0.03 min], and the second one, 0.06482(3) d (93.34 ± 0.04 min), which is less likely. The evolutionary status of the object depends dramatically on the choice between these two values. A spectroscopic determination of the orbital period is needed. We updated available information on ER UMa-type stars and present a new set of their basic statistics. Thereby, we provide evidence that this class of stars is not uniform.

Recent Observations of AG Pegasi's Latest Outburst Phase by Harvard Observing Project

NASA Astrophysics Data System (ADS)

Espinel, Jose Luis; Lewis, John; Budreviciute, Rimute; Bieryla, Allyson; Denham Alexander, Kate; Blanchard, Peter; Carmichael, Theron; Garrison, Lehman H.; Huang, Jane; Mayo, Andrew; McIntosh, Missy; Vanderburg, Andrew; Alam, Munazza; Cordova, Rodrigo; Gomez, Sebastian; Weaver, Ian; Yuan, Sihan; Price, Evander

2017-01-01

AG Pegasi (AG Peg) is a symbiotic binary star composed of a red supergiant and a white dwarf. Between 1860 and 1870, AG Peg brightened from magnitude 9 to 6, before gradually dimming. In 2015, the star began another brightening phase. The outbursts are thought to be caused by accretion of material onto the white dwarf. Once there is enough hydrogen accreted, hydrogen shell-burning starts leading to the the star’s evolution into a A-supergiant with a high mass-loss rate (Kenyon et al. 1993). The Harvard Observing Project (HOP) collected photometric data in BVRI filters using Harvard’s 16-inch Clay Telescope in the Fall term of 2015 and again in the Fall term of 2016. HOP is designed to get undergraduate students interested in astronomy and observing, and to allow graduate students opportunities to interact with undergraduates and get more observing/teaching experience. This study monitors the luminosity of AG Peg to constrain the amplitude and duration of the latest outburst.

Phase diagram of Ag-Pd bimetallic nanoclusters by molecular dynamics simulations: solid-to-liquid transition and size-dependent behavior.

PubMed

Kim, Da Hye; Kim, Hyun You; Ryu, Ji Hoon; Lee, Hyuck Mo

2009-07-07

This report on the solid-to-liquid transition region of an Ag-Pd bimetallic nanocluster is based on a constant energy microcanonical ensemble molecular dynamics simulation combined with a collision method. By varying the size and composition of an Ag-Pd bimetallic cluster, we obtained a complete solid-solution type of binary phase diagram of the Ag-Pd system. Irrespective of the size and composition of the cluster, the melting temperature of Ag-Pd bimetallic clusters is lower than that of the bulk state and rises as the cluster size and the Pd composition increase. Additionally, the slope of the phase boundaries (even though not exactly linear) is lowered when the cluster size is reduced on account of the complex relations of the surface tension, the bulk melting temperature, and the heat of fusion. The melting of the cluster initially starts at the surface layer. The initiation and propagation of a five-fold icosahedron symmetry is related to the sequential melting of the cluster.

AG Dra is going into outburst again, of the hot type and the third in the present series

NASA Astrophysics Data System (ADS)

Munari, U.; Righetti, G. L.; Valisa, P.; Buzzi, L.; Moretti, S.

2017-05-01

The outbursts of the Halo symbiotic binary and super-soft X-ray source AG Dra are known to come in series (1932-1939, 1949-1955, 1963-1966, 1980-1986, 1993-2008, Leedjarv et al. 2016 MNRAS 456, 2558, Galis et al. 2017, OEJV 180, 24), usually started by a large amplitude eruption of the "cool" type, followed by a train of lower amplitude events of the "hot" type (Gonzalez-Riestra et al. 1999, A & A 1999, 347, 478).

Complexation and phase evolution at dimethylformamide-Ag(111) interfaces

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

Song, Wentao; Leung, Kevin; Shao, Qian

The interaction of solvent molecules with metallic surfaces impacts many interfacial chemical processes. We investigate the chemical and structure evolution that follows adsorption of the polar solvent dimethylformamide (DMF) on Ag(111). An Ag(DMF) 2 coordination complex forms spontaneously by DMF etching of Ag(111), yielding mixed films of the complexes and DMF. Utilizing ultrahigh vacuum scanning tunneling microscopy (UHV-STM), in combination with X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) computations, we map monolayer phases from the 2-D gas regime, consisting of a binary mixture of DMF and Ag(DMF) 2, through the saturation monolayer limit, in which these two chemicalmore » species phase separate into ordered islands. Structural models for the near-square DMF phase and the chain-like Ag(DMF) 2 phase are presented and supported by DFT computation. Interface evolution is summarized in a surface pressure-composition phase diagram, which allows structure prediction over arbitrary experimental conditions. In conclusion, this work reveals new surface coordination chemistry for an important electrolyte-electrode system, and illustrates how surface pressure can be used to tune monolayer phases.« less

Complexation and phase evolution at dimethylformamide-Ag(111) interfaces

DOE PAGES

Song, Wentao; Leung, Kevin; Shao, Qian; ...

2016-09-15

The interaction of solvent molecules with metallic surfaces impacts many interfacial chemical processes. We investigate the chemical and structure evolution that follows adsorption of the polar solvent dimethylformamide (DMF) on Ag(111). An Ag(DMF) 2 coordination complex forms spontaneously by DMF etching of Ag(111), yielding mixed films of the complexes and DMF. Utilizing ultrahigh vacuum scanning tunneling microscopy (UHV-STM), in combination with X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) computations, we map monolayer phases from the 2-D gas regime, consisting of a binary mixture of DMF and Ag(DMF) 2, through the saturation monolayer limit, in which these two chemicalmore » species phase separate into ordered islands. Structural models for the near-square DMF phase and the chain-like Ag(DMF) 2 phase are presented and supported by DFT computation. Interface evolution is summarized in a surface pressure-composition phase diagram, which allows structure prediction over arbitrary experimental conditions. In conclusion, this work reveals new surface coordination chemistry for an important electrolyte-electrode system, and illustrates how surface pressure can be used to tune monolayer phases.« less

Reassessment of Atomic Mobilities in fcc Cu-Ag-Sn System Aiming at Establishment of an Atomic Mobility Database in Sn-Ag-Cu-In-Sb-Bi-Pb Solder Alloys

NASA Astrophysics Data System (ADS)

Xu, Huixia; Zhang, Lijun; Cheng, Kaiming; Chen, Weimin; Du, Yong

2017-04-01

To establish an accurate atomic mobility database in solder alloys, a reassessment of atomic mobilities in the fcc (face centered cubic) Cu-Ag-Sn system was performed as reported in the present work. The work entailed initial preparation of three fcc Cu-Sn diffusion couples, which were used to determine the composition-dependent interdiffusivities at 873 K, 923 K, and 973 K, to validate the literature data and provide new experimental data at low temperatures. Then, atomic mobilities in three boundary binaries, fcc Cu-Sn, fcc Ag-Sn, and fcc Cu-Ag, were updated based on the data for various experimental diffusivities obtained from the literature and the present work, together with the available thermodynamic database for solder alloys. Finally, based on the large number of interdiffusivities recently measured from the present authors, atomic mobilities in the fcc Cu-Ag-Sn ternary system were carefully evaluated. A comprehensive comparison between various calculated/model-predicted diffusion properties and the experimental data was used to validate the reliability of the obtained atomic mobilities in ternary fcc Cu-Ag-Sn alloys.

Viscosity and diffusivity in melts: from unary to multicomponent systems

NASA Astrophysics Data System (ADS)

Chen, Weimin; Zhang, Lijun; Du, Yong; Huang, Baiyun

2014-05-01

Viscosity and diffusivity, two important transport coefficients, are systematically investigated from unary melt to binary to multicomponent melts in the present work. By coupling with Kaptay's viscosity equation of pure liquid metals and effective radii of diffusion species, the Sutherland equation is modified by taking the size effect into account, and further derived into an Arrhenius formula for the convenient usage. Its reliability for predicting self-diffusivity and impurity diffusivity in unary liquids is then validated by comparing the calculated self-diffusivities and impurity diffusivities in liquid Al- and Fe-based alloys with the experimental and the assessed data. Moreover, the Kozlov model was chosen among various viscosity models as the most reliable one to reproduce the experimental viscosities in binary and multicomponent melts. Based on the reliable viscosities calculated from the Kozlov model, the modified Sutherland equation is utilized to predict the tracer diffusivities in binary and multicomponent melts, and validated in Al-Cu, Al-Ni and Al-Ce-Ni melts. Comprehensive comparisons between the calculated results and the literature data indicate that the experimental tracer diffusivities and the theoretical ones can be well reproduced by the present calculations. In addition, the vacancy-wind factor in binary liquid Al-Ni alloys with the increasing temperature is also discussed. What's more, the calculated inter-diffusivities in liquid Al-Cu, Al-Ni and Al-Ag-Cu alloys are also in excellent agreement with the measured and theoretical data. Comparisons between the simulated concentration profiles and the measured ones in Al-Cu, Al-Ce-Ni and Al-Ag-Cu melts are further used to validate the present calculation method.

Single-step solvothermal synthesis of mesoporous Ag-TiO2-reduced graphene oxide ternary composites with enhanced photocatalytic activity.

PubMed

Sher Shah, Md Selim Arif; Zhang, Kan; Park, A Reum; Kim, Kwang Su; Park, Nam-Gyu; Park, Jong Hyeok; Yoo, Pil J

2013-06-07

With growing interest in the photocatalytic performance of TiO2-graphene composite systems, the ternary phase of TiO2, graphene, and Ag is expected to exhibit improved photocatalytic characteristics because of the improved recombination rate of photogenerated charge carriers and potential contribution of the generation of localized surface plasmon resonance at Ag sites on a surface of the TiO2-graphene binary matrix. In this work, Ag-TiO2-reduced graphene oxide ternary nanocomposites were successfully synthesized by a simple solvothermal process. In a single-step synthetic procedure, the reduction of AgNO3 and graphene oxide and the hydrolysis of titanium tetraisopropoxide were spontaneously performed in a mixed solvent system of ethylene glycol, N,N-dimethylformamide and a stoichiometric amount of water without resorting to the use of typical reducing agents. The nanocomposites were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, along with different microscopic and spectroscopic techniques, enabling us to confirm the successful reduction of AgNO3 and graphite oxide to metallic Ag and reduced graphene oxide, respectively. Due to the highly facilitated electron transport of well distributed Ag nanoparticles, the synthesized ternary nanocomposite showed enhanced photocatalytic activity for degradation of rhodamine B dye under visible light irradiation.

Worldwide Radionavigation Systems

DTIC Science & Technology

1993-09-01

apparent pole star changes over time. In 3,000 BC the pole star was a Draconis, the brightest star in the constellation Draco (the Dragon), located...the yet-to-be-completed Global Positioning System (GPS), have added a new dimension to the science of navigation. The gyrocompass and inertial platforms...funded as an IDA Central Research Project, is a collection of technical descriptions of worldwide radionavigation systems written by the author over a

Development of an Agrobacterium-based transformation system for Rhizoctonia solani

USDA-ARS?s Scientific Manuscript database

A 8.7 kb binary vector containing the 1.9 kb hygromycin B phosphortransferase (hyg) gene was constructed with promoter and terminator regions from the glyceraldehyde-3-phosphate- dehydrogenase (gpd) gene of Rhizoctonia solani anastomosis group 3 (AG-3) at the 5'- and 3'- gene termini of hyg. Promot...

Equivalent crystal theory of alloys

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Ferrante, John

1991-01-01

Equivalent Crystal Theory (ECT) is a new, semi-empirical approach to calculating the energetics of a solid with defects. The theory has successfully reproduced surface energies in metals and semiconductors. The theory of binary alloys to date, both with first-principles and semi-empirical models, has not been very successful in predicting the energetics of alloys. This procedure is used to predict the heats of formation, cohesive energy, and lattice parameter of binary alloys of Cu, Ni, Al, Ag, Au, Pd, and Pt as functions of composition. The procedure accurately reproduces the heats of formation versus composition curves for a variety of binary alloys. The results are then compared with other approaches such as the embedded atom and lattice parameters of alloys from pure metal properties more accurately than Vegard's law is presented.

Pairing Heterocyclic Cations with closo-dodecafluorododecaborate(2-). Synthesis of Binary Heterocyclium(1+) Salts and a AG4(heterocycle)8(4+) Salt of B12F12(2-) (Preprint)

DTIC Science & Technology

2011-04-04

10989). 13. SUPPLEMENTARY NOTES For publication in the AIAA Journal of Fluorine Chemistry. 14. ABSTRACT Eight binary salts that pair triazolium...4]. This characteristic permitted the synthesis of the B12F122– dianion by electrophilic attack of supercritical HF in 1992 (it was isolated as Cs2...B. A. Wight, H. L. Ammon, D. V. Peryshkov, S. H. Strauss, Org. Lett. 12 (2010) 2714–2717. [9] D. V. Peryshkov, S. H. Strauss J. Fluorine Chem. 131

Molecular and electronic structure, magnetotropicity and absorption spectra of benzene-trinuclear copper(I) and silver(I) trihalide columnar binary stacks.

PubMed

Tsipis, A C; Stalikas, A V

2012-02-20

The molecular and electronic structures, stabilities, bonding features, magnetotropicity and absorption spectra of benzene-trinuclear Cu(I) and Ag(I) trihalide columnar binary stacks with the general formula [c-M(3)(μ(2)-X)(3)](n)(C(6)H(6))(m) (M = Cu, Ag; X = halide; n, m ≤ 2) have been investigated by means of electronic structure calculation methods. The interaction of c-M(3)(μ(2)-X)(3) clusters with one and two benzene molecules yields 1:1 and 1:2 binary stacks, while benzene sandwiched 2:1 stacks are formed upon interaction of two c-M(3)(μ(2)-X)(3) clusters with one benzene molecule. In all binary stacks the plane of the alternating c-M(3)(μ(2)-X)(3) and benzene components adopts an almost parallel orientation. The separation distance between the centroids of the benzene and the proximal c-M(3)(μ(2)-X)(3) metallic cluster found in the range 2.97-3.33 Å at the B97D/Def2-TZVP level is indicative of a π···π stacking interaction mode, for the centroid separation distance is very close to the sum of the van der Waals radii of Cu···C (3.10 Å) and Ag···C (3.44 Å). Energy decomposition analysis (EDA) at the SSB-D/TZP level revealed that the dominant term in the c-M(3)(μ(2)-X)(3)···C(6)H(6) interaction arises from dispersion and electrostatic forces while the covalent interactions are predicted to be negligible. On the other hand, charge decomposition analysis (CDA) illustrated very small charge transfer from C(6)H(6) toward the c-M(3)(μ(2)-X)(3) clusters, thus reflecting weak π-base/π-acid interactions which are further corroborated by the respective electrostatic potentials and the fact that the total dipole moment vector points to the center of the metallic ring of the c-M(3)(μ(2)-X)(3) cluster. The absorption spectra of all aromatic columnar binary stacks simulated by means of TD-DFT calculations showed strong absorptions in the UV region. The main features of the simulated absorption spectra are thoroughly analyzed, and assignments of the contributing electronic transitions are given. The magnetotropicity of the binary stacks evaluated by the NICS(zz)-scan curves indicated an enhancement of the diatropicity of the inorganic ring upon interaction with the aromatic benzene molecule. Noteworthy is the slight enhancement of the diatropicity of the benzene ring, particularly in the region between the interacting rings, probably due to the superposition (coupling) of the diamagnetic ring currents of the interacting aromatic ring systems.

Refractivity of Molten Nitrates and Chlorides: Binary Mixtures Containing Cesium Ions

NASA Astrophysics Data System (ADS)

Uchiyama, Yohji; Karawacki, Ernest

1981-05-01

By using an interferometric technique, the refractive index of some molten salt mixtures containing Cs+ ions was measured with high accuracy: (Li-Cs)NO3, (Na-Cs)NO3, (Ag-Cs)NO3, (Li-Cs)Cl, and also pure RbCl. The isotherms of molar refractivity show a small negative deviation from additivity in the (Li-Cs)NO3 and (Li-Cs)Cl systems and a positive deviation in the (Ag-Cs)NO3 mixture. A tentative attempt was made to relate the excess molar refractivities with the absorption bands of the ions.

A facile single-step synthesis of ternary multicore magneto-plasmonic nanoparticles.

PubMed

Benelmekki, Maria; Bohra, Murtaza; Kim, Jeong-Hwan; Diaz, Rosa E; Vernieres, Jerome; Grammatikopoulos, Panagiotis; Sowwan, Mukhles

2014-04-07

We report a facile single-step synthesis of ternary hybrid nanoparticles (NPs) composed of multiple dumbbell-like iron-silver (FeAg) cores encapsulated by a silicon (Si) shell using a versatile co-sputter gas-condensation technique. In comparison to previously reported binary magneto-plasmonic NPs, the advantage conferred by a Si shell is to bind the multiple magneto-plasmonic (FeAg) cores together and prevent them from aggregation at the same time. Further, we demonstrate that the size of the NPs and number of cores in each NP can be modulated over a wide range by tuning the experimental parameters.

Physical Structure of Four Symbiotic Binaries

NASA Technical Reports Server (NTRS)

Kenyon, Scott J. (Principal Investigator)

1997-01-01

Disk accretion powers many astronomical objects, including pre-main sequence stars, interacting binary systems, and active galactic nuclei. Unfortunately, models developed to explain the behavior of disks and their surroundings - boundary layers, jets, and winds - lack much predictive power, because the physical mechanism driving disk evolution - the viscosity - is not understood. Observations of many types of accreting systems are needed to constrain the basic physics of disks and provide input for improved models. Symbiotic stars are an attractive laboratory for studying physical phenomena associated with disk accretion. These long period binaries (P(sub orb) approx. 2-3 yr) contain an evolved red giant star, a hot companion, and an ionized nebula. The secondary star usually is a white dwarf accreting material from the wind of its red giant companion. A good example of this type of symbiotic is BF Cygni: our analysis shows that disk accretion powers the nuclear burning shell of the hot white dwarf and also manages to eject material perpendicular to the orbital plane (Mikolajewska, Kenyon, and Mikolajewski 1989). The hot components in other symbiotic binaries appear powered by tidal overflow from a very evolved red giant companion. We recently completed a study of CI Cygni and demonstrated that the accreting secondary is a solar-type main sequence star, rather than a white dwarf (Kenyon et aL 1991). This project continued our study of symbiotic binary systems. Our general plan was to combine archival ultraviolet and optical spectrophotometry with high quality optical radial velocity observations to determine the variation of line and continuum sources as functions of orbital phase. We were very successful in generating orbital solutions and phasing UV+optical spectra for five systems: AG Dra, V443 Her, RW Hya, AG Peg, and AX Per. Summaries of our main results for these systems appear below. A second goal of our project was to consider general models for the outbursts of symbiotic stars, with an emphasis on understanding the differences between disk-driven and nuclear-powered eruptions.

Structural and optical properties of (Ag,Cu)(In,Ga)Se{sub 2} polycrystalline thin film alloys

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

Boyle, J. H.; Shafarman, W. N.; Birkmire, R. W.

2014-06-14

The structural and optical properties of pentenary alloy (Ag,Cu)(In,Ga)Se{sub 2} polycrystalline thin films were characterized over the entire compositional range at a fixed (Cu + Ag)/(In + Ga) ratio. Films deposited at 550 °C on bare and molybdenum coated soda-lime glass by elemental co-evaporation in a single-stage process with constant incident fluxes exhibit single phase chalcopyrite structure, corresponding to 122 spacegroup (I-42d) over the entire compositional space. Unit cell refinement of the diffraction patterns show that increasing Ag substitution for Cu, the refined a{sub o} lattice constant, (Ag,Cu)-Se bond length, and anion displacement increase in accordance with the theoretical model proposed by Jaffe, Wei, andmore » Zunger. However, the refined c{sub o} lattice constant and (In,Ga)-Se bond length deviated from theoretical expectations for films with mid-range Ag and Ga compositions and are attributed to influences from crystallographic bond chain ordering or cation electronegativity. The optical band gap, derived from transmission and reflection measurements, widened with increasing Ag and Ga content, due to influences from anion displacement and cation electronegativity, as expected from theoretical considerations for pseudo-binary chalcopyrite compounds.« less

Pressure tuning the lattice and optical response of silver sulfide

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

Zhao, Zhao, E-mail: zhaozhao@stanford.edu; Wei, Hua; Mao, Wendy L.

2016-06-27

Binary transition metal chalcogenides have attracted increasing attention for their unique structural and electronic properties. High pressure is a powerful tool for tuning the lattice and electronic structure of transition metal chalcogenides away from their pristine states. In this work, we systematically studied the in situ structural and optical behavior of silver sulfide (Ag{sub 2}S) under pressure by synchrotron X-ray diffraction and infrared spectroscopy measurements in a diamond anvil cell. Upon compression, Ag{sub 2}S undergoes structural symmetrization accompanied by a series of structural transitions while the crystallographic inequivalence of the two Ag sites is maintained. Electronically, pressure effectively tunes themore » ambient semiconducting Ag{sub 2}S into a metal at ∼22 GPa. Drude model analysis shows that the optical conductivity evolves significantly, reaching the highest value of 100 Ω{sup −1} cm{sup −1} at ∼40 GPa. Our results highlight the structural and electronic tunability of silver chalcogenides as a function of pressure and suggest the potential of Ag{sub 2}S as a platform for developing optical and opto-electronic applications.« less

The Effects of Adding Elements of Zinc and Magnesium on Ag-Cu Eutectic Alloy for Warming Acupuncture

PubMed Central

Park, Il Song; Kim, Keun Sik; Lee, Min Ho

2013-01-01

The warming acupuncture for hyperthermia therapy is made of STS304. However, its needle point cannot be reached to a desirable temperature due to heat loss caused by low thermal conductivity, and the quantification of stimulation condition and the effective standard establishment of warming acupuncture are required as a heat source. Accordingly, in this study, after Ag-Cu alloys with different composition ratios were casted and then mixed with additives to improve their physical and mechanical properties, the thermal conductivity and biocompatibility of the alloy specimens were evaluated for selecting suitable material. Ag-Cu binary alloys and ternary alloys added 5 wt% Zn or 2 wt% Mg were casted and then cold drawn to manufacture needles for acupuncture, and their physical properties, thermal conductivity, and biocompatibility were evaluated for their potential use in warming acupuncture. The results of this study showed that the physical and mechanical properties of the Ag-Cu alloys were improved by additives and that the thermal conductivity, machinability, and biocompatibility of the Ag-Cu alloys were improved by Mg addition. PMID:24078827

The effects of adding elements of zinc and magnesium on ag-cu eutectic alloy for warming acupuncture.

PubMed

Kim, Yu Kyoung; Park, Il Song; Kim, Keun Sik; Lee, Min Ho

2013-01-01

The warming acupuncture for hyperthermia therapy is made of STS304. However, its needle point cannot be reached to a desirable temperature due to heat loss caused by low thermal conductivity, and the quantification of stimulation condition and the effective standard establishment of warming acupuncture are required as a heat source. Accordingly, in this study, after Ag-Cu alloys with different composition ratios were casted and then mixed with additives to improve their physical and mechanical properties, the thermal conductivity and biocompatibility of the alloy specimens were evaluated for selecting suitable material. Ag-Cu binary alloys and ternary alloys added 5 wt% Zn or 2 wt% Mg were casted and then cold drawn to manufacture needles for acupuncture, and their physical properties, thermal conductivity, and biocompatibility were evaluated for their potential use in warming acupuncture. The results of this study showed that the physical and mechanical properties of the Ag-Cu alloys were improved by additives and that the thermal conductivity, machinability, and biocompatibility of the Ag-Cu alloys were improved by Mg addition.

Thermodynamic modelling of the C-U and B-U binary systems

NASA Astrophysics Data System (ADS)

Chevalier, P. Y.; Fischer, E.

2001-02-01

The thermodynamic modelling of the carbon-uranium (C-U) and boron-uranium (B-U) binary systems is being performed in the framework of the development of a thermodynamic database for nuclear materials, for increasing the basic knowledge of key phenomena which may occur in the event of a severe accident in a nuclear power plant. Applications are foreseen in the nuclear safety field to the physico-chemical interaction modelling, on the one hand the in-vessel core degradation producing the corium (fuel, zircaloy, steel, control rods) and on the other hand the ex-vessel molten corium-concrete interaction (MCCI). The key O-U-Zr ternary system, previously modelled, allows us to describe the first interaction of the fuel with zircaloy cladding. Then, the three binary systems Fe-U, Cr-U and Ni-U were modelled as a preliminary work for modelling the O-U-Zr-Fe-Cr-Ni multicomponent system, allowing us to introduce the steel components in the corium. In the existing database (TDBCR, thermodynamic data base for corium), Ag and In were introduced for modelling AIC (silver-indium-cadmium) control rods which are used in French pressurized water reactors (PWR). Elsewhere, B 4C is also used for control rods. That is why it was agreed to extend in the next years the database with two new components, B and C. Such a work needs the thermodynamic modelling of all the binary and pseudo-binary sub-systems resulting from the combination of B, B 2O 3 and C with the major components of TDBCR, O-U-Zr-Fe-Cr-Ni-Ag-In-Ba-La-Ru-Sr-Al-Ca-Mg-Si + Ar-H. The critical assessment of the very numerous experimental information available for the C-U and B-U binary systems was performed by using a classical optimization procedure and the Scientific Group Thermodata Europe (SGTE). New optimized Gibbs energy parameters are given, and comparisons between calculated and experimental equilibrium phase diagrams or thermodynamic properties are presented. The self-consistency obtained is quite satisfactory.

Long-Term Quadrature Light Variability in Early Type Interacting Binary Systems

NASA Astrophysics Data System (ADS)

Peters, Geraldine J.; Wilson, R. E.; Vaccaro, T. R.

2014-01-01

Four years of Kepler observations have revealed a phenomenon in the light curves of short-period Algol-type eclipsing binaries that has never been reported from ground-based photometry. These systems display unequal brightness at their quadrature phases that numerically reverses over a time scale of about 100-400 days. We call these systems L/T (leading hemisphere/ trailing hemisphere) variables. Twenty-one such systems have so far been identified in the Kepler database and at least three classes of L/T behavior have been identified. The prototype is WX Draconis (A8V + K0IV, P=1.80 d) which shows L/ T light variations of 2-3%. The primary is a delta Scuti star with a dominant pulsation period of 41 m. The Kepler light curves are being analyzed with the 2013 version of the Wilson-Devinney (WD) program that includes major improvements in modeling star spots (i.e. spot motions due to drift and stellar rotation and spot growth and decay). Preliminary analysis of the WX Dra data suggests that the L/T variability can be fit with either an accretion hot spot on the primary (T = 2.3 T_phot) that jumps in longitude or a magnetic cool spotted region on the secondary. If the latter model is correct the dark region must occupy at least 20% of the surface of the facing hemisphere of the secondary if it is completely black, or a larger area if not completely black. In both hot and cool spot scenarios magnetic fields must play a role in the activity. Echelle spectra were recently secured with the KPNO 4-m telescope to determine the mass ratios of the L/T systems and their spectral types. This information will allow us to assess whether the hot or cool spot model explains the L/T activity. Progress toward this goal will be presented. Support from NASA grants NNX11AC78G and NNX12AE44G and USC’s Women in Science and Engineering (WiSE) program is greatly appreciated.

VSOP: the variable star one-shot project. I. Project presentation and first data release

NASA Astrophysics Data System (ADS)

Dall, T. H.; Foellmi, C.; Pritchard, J.; Lo Curto, G.; Allende Prieto, C.; Bruntt, H.; Amado, P. J.; Arentoft, T.; Baes, M.; Depagne, E.; Fernandez, M.; Ivanov, V.; Koesterke, L.; Monaco, L.; O'Brien, K.; Sarro, L. M.; Saviane, I.; Scharwächter, J.; Schmidtobreick, L.; Schütz, O.; Seifahrt, A.; Selman, F.; Stefanon, M.; Sterzik, M.

2007-08-01

Context: About 500 new variable stars enter the General Catalogue of Variable Stars (GCVS) every year. Most of them however lack spectroscopic observations, which remains critical for a correct assignement of the variability type and for the understanding of the object. Aims: The Variable Star One-shot Project (VSOP) is aimed at (1) providing the variability type and spectral type of all unstudied variable stars, (2) process, publish, and make the data available as automatically as possible, and (3) generate serendipitous discoveries. This first paper describes the project itself, the acquisition of the data, the dataflow, the spectroscopic analysis and the on-line availability of the fully calibrated and reduced data. We also present the results on the 221 stars observed during the first semester of the project. Methods: We used the high-resolution echelle spectrographs HARPS and FEROS in the ESO La Silla Observatory (Chile) to survey known variable stars. Once reduced by the dedicated pipelines, the radial velocities are determined from cross correlation with synthetic template spectra, and the spectral types are determined by an automatic minimum distance matching to synthetic spectra, with traditional manual spectral typing cross-checks. The variability types are determined by manually evaluating the available light curves and the spectroscopy. In the future, a new automatic classifier, currently being developed by members of the VSOP team, based on these spectroscopic data and on the photometric classifier developed for the COROT and Gaia space missions, will be used. Results: We confirm or revise spectral types of 221 variable stars from the GCVS. We identify 26 previously unknown multiple systems, among them several visual binaries with spectroscopic binary individual components. We present new individual results for the multiple systems V349 Vel and BC Gru, for the composite spectrum star V4385 Sgr, for the T Tauri star V1045 Sco, and for DM Boo which we re-classify as a BY Draconis variable. The complete data release can be accessed via the VSOP web site. Based on data obtained at the La Silla Observatory, European Southern Observatory, under program ID 077.D-0085.

Resistive switching memory devices composed of binary transition metal oxides using sol-gel chemistry.

PubMed

Lee, Chanwoo; Kim, Inpyo; Choi, Wonsup; Shin, Hyunjung; Cho, Jinhan

2009-04-21

We describe a novel and versatile approach for preparing resistive switching memory devices based on binary transition metal oxides (TMOs). Titanium isopropoxide (TIPP) was spin-coated onto platinum (Pt)-coated silicon substrates using a sol-gel process. The sol-gel-derived layer was converted into a TiO2 film by thermal annealing. A top electrode (Ag electrode) was then coated onto the TiO2 films to complete device fabrication. When an external bias was applied to the devices, a switching phenomenon independent of the voltage polarity (i.e., unipolar switching) was observed at low operating voltages (about 0.6 VRESET and 1.4 VSET). In addition, it was confirmed that the electrical properties (i.e., retention time, cycling test and switching speed) of the sol-gel-derived devices were comparable to those of vacuum deposited devices. This approach can be extended to a variety of binary TMOs such as niobium oxides. The reported approach offers new opportunities for preparing the binary TMO-based resistive switching memory devices allowing a facile solution processing.

Self-assembly of metal nanostructures on binary alloy surfaces

PubMed Central

Duguet, T.; Han, Yong; Yuen, Chad; Jing, Dapeng; Ünal, Barış; Evans, J. W.; Thiel, P. A.

2011-01-01

Deposition of metals on binary alloy surfaces offers new possibilities for guiding the formation of functional metal nanostructures. This idea is explored with scanning tunneling microscopy studies and atomistic-level analysis and modeling of nonequilibrium island formation. For Au/NiAl(110), complex monolayer structures are found and compared with the simple fcc(110) bilayer structure recently observed for Ag/NiAl(110). We also consider a more complex codeposition system, (Ni + Al)/NiAl(110), which offers the opportunity for fundamental studies of self-growth of alloys including deviations for equilibrium ordering. A general multisite lattice-gas model framework enables analysis of structure selection and morphological evolution in these systems. PMID:21097706

The Kongsberg silver deposits, Norway: Ag-Hg-Sb mineralization and constraints for the formation of the deposits

NASA Astrophysics Data System (ADS)

Kotková, Jana; Kullerud, Kåre; Šrein, Vladimír; Drábek, Milan; Škoda, Radek

2018-04-01

The Kongsberg silver district has been investigated by microscopy and electron microprobe analysis, focusing primarily on the Ag-Hg-Sb mineralization within the context of the updated mineral paragenesis. The earliest mineralization stage is represented by sulfides, including acanthite, and sulfosalts. Native silver formed initially through breakdown of early Ag-bearing phases and later through influx of additional Ag-bearing fluids and silver remobilization. The first two generations of native silver were separated in time by the formation of Ni-Co-Fe sulfarsenides and the monoarsenide niccolite along rims of silver crystals. The presence of As-free sulfosalts and the absence of di- and tri-arsenides suggest a lower arsenic/sulfur activity ratio for the Kongsberg deposits compared to other five-element deposits. Native silver shows binary Ag-Hg and Ag-Sb solid solutions, in contrast to the ternary Ag-Hg-Sb compositions typical for other deposits of similar type. Antimonial silver together with allargentum, dyscrasite, and pyrargyrite was documented exclusively from the northern area of the district. Elsewhere, the only Sb-bearing minerals are polybasite and tetrahedrite/freibergite. Hg-rich silver (up to 21 wt% Hg) has been documented only in the central-western area. Myrmekite of freibergite and chalcopyrite reflects exsolution from an original Ag-poor tetrahedrite upon cooling, while myrmekite of pyrite and silver, forming through breakdown of low-temperature phases (argentopyrite or lenaite) upon heating, characterizes the Kongsberg silver district. Based on the stabilities of minerals and mineral assemblages, the formation of the silver mineralization can be constrained to temperatures between 180 and 250 °C.

A search for radio emission from Galactic supersoft X-ray sources

NASA Astrophysics Data System (ADS)

Ogley, R. N.; Chaty, S.; Crocker, M.; Eyres, S. P. S.; Kenworthy, M. A.; Richards, A. M. S.; Rodríguez, L. F.; Stirling, A. M.

2002-03-01

We have made a deep search for radio emission from all the northern hemisphere supersoft X-ray sources using the Very Large Array (VLA) and multi-element radio-linked interferometer network (MERLIN) telescopes, at 5 and 8.4GHz. Three previously undetected sources, T Pyx, V1974 Cygni and RX J0019.8+2156, were imaged in quiescence using the VLA in order to search for any persistent emission. No radio emission was detected in any of the VLA fields down to a typical 1σ rms noise of 20μJybeam-1, however, 17 new point sources were detected in the fields with 5-GHz fluxes between 100 and 1500μJy, giving an average 100-μJy source density of ~200deg-2, comparable to what was found in the MERLIN Hubble Deep Field survey. The persistent source AG Draconis was observed by MERLIN to provide a confirmation of previous VLA observations and to investigate the source at a higher resolution. The core is resolved at the milliarcsec scale into two components that have a combined flux of ~1mJy. It is possible that we are detecting nebulosity, which is becoming resolved out by the higher MERLIN resolution. We have investigated possible causes of radio emission from a wind environment, both directly from the secondary star, and also consequently, of the high X-ray luminosity from the white dwarf. There is an order of magnitude discrepancy between observed and modelled values that can be explained by the uncertainty in fundamental quantities within these systems.

Local structure of amorphous Ag5In5Sb60Te30 and In3SbTe2 phase change materials revealed by X-ray photoelectron and Raman spectroscopic studies

NASA Astrophysics Data System (ADS)

Sahu, Smriti; Manivannan, Anbarasu; Shaik, Habibuddin; Mohan Rao, G.

2017-07-01

Reversible switching between highly resistive (binary "0") amorphous phase and low resistive (binary "1") crystalline phase of chalcogenide-based Phase Change Materials is accredited for the development of next generation high-speed, non-volatile, data storage applications. The doped Sb-Te based materials have shown enhanced electrical/optical properties, compared to Ge-Sb-Te family for high-speed memory devices. We report here the local atomic structure of as-deposited amorphous Ag5In5Sb60Te30 (AIST) and In3SbTe2 (IST) phase change materials using X-ray photoelectron and Raman spectroscopic studies. Although AIST and IST materials show identical crystallization behavior, they differ distinctly in their crystallization temperatures. Our experimental results demonstrate that the local environment of In remains identical in the amorphous phase of both AIST and IST material, irrespective of its atomic fraction. In bonds with Sb (˜44%) and Te (˜56%), thereby forming the primary matrix in IST with a very few Sb-Te bonds. Sb2Te constructs the base matrix for AIST (˜63%) along with few Sb-Sb bonds. Furthermore, an interesting assimilation of the role of small-scale dopants such as Ag and In in AIST, reveals rare bonds between themselves, while showing selective substitution in the vicinity of Sb and Te. This results in increased electronegativity difference, and consequently, the bond strength is recognized as the factor rendering stability in amorphous AIST.

Discussion Meeting on Thermodynamics of Alloys Held in Sant Feliu de Guixols, Spain on 23-26 May 1990. Abstracts

DTIC Science & Technology

1990-05-26

OFFICE OF THE U.S. ARMY EUROPEAN RESEARCH OFFICE OF THE U.S. AIR FORCE MINISTERIO DE EDUCACION Y CIENCIA I I Wednesday, May 23 8.30 Registration 9.00... especially regarding the structural but less the thermodynamic proper- ties). The third binary system Ag-Te has been investigated in detail by our group. No

A Study of Magnesium-Base Metallic Systems and Development of Principles for Creation of Corrosion-Resistant Magnesium Alloys

NASA Astrophysics Data System (ADS)

Mukhina, I. Yu.

2014-11-01

The effect of 26 alloying elements on the corrosion resistance of high-purity magnesium in a 0.5-n solution of sodium chloride and in a humid atmosphere (0.005 n) is studied. The Mg - Li, Mg - Ag, Mg - Zn, Mg - Cu, Mg - Gd, Mg - Al, Mg - Zr, Mg - Mn and other binary systems, which present interest as a base for commercial or perspective castable magnesium alloys, are studied. The characteristics of corrosion resistance of the binary alloys are analyzed in accordance with the group and period of the Mendeleev's periodic law. The roles of the electrochemical and volume factors and of the factor of the valence of the dissolved element are determined.

Structural-Phase States of Fe-Cu and Fe-Ag Bimetallic Particles Produced by Electric Explosion of Two Wires

NASA Astrophysics Data System (ADS)

Lerner, M. I.; Bakina, O. V.; Pervikov, A. V.; Glazkova, E. A.; Lozhkomoev, A. S.; Vorozhtsov, A. B.

2018-05-01

X-ray phase analysis, transmission electron microscopy, and X-ray microanalysis were used to examine the structural-phase states of Fe-Cu and Fe-Ag bimetallic nanoparticles. The nanoparticles were obtained by the electric explosion of two twisted metal wires in argon atmosphere. It was demonstrated that the nanoparticles have the structure of Janus particles. Presence of the Janus particle structure in the samples indicates formation of binary melt under conditions of combined electric explosion of two wires. Phases based on supersaturated solid solutions were not found in the examined samples. The data obtained allow arguing that it is possible to achieve uniform mixing of the two-wire explosion products under the described experiment conditions.

Spins of complex fragments in binary reactions within a dinuclear system model

NASA Astrophysics Data System (ADS)

Paşca, H.; Kalandarov, Sh. A.; Adamian, G. G.; Antonenko, N. V.

2017-10-01

The average angular momenta and widths of the spin distributions of reaction products are calculated within the dinuclear system model. The thermal excitation of rotational bearing modes is considered in the dinuclear system. The calculated fragment spins (γ multiplicities) and their variances in the reactions 20Ne (166 MeV) + 63Cu, 40Ar (280 MeV) + 58Ni, 20Ne (175 MeV) + natAg, 40Ar (237 MeV) + 89Y, 40Ar (288 and 340 MeV) + Ag,109107, and 16O (100 MeV) + 58Ni are compared with the available experimental data. The influence of the entrance channel charge (mass) asymmetry and bombarding energy on the characteristics of spin distribution is studied.

Structural-Phase States of Fe–Cu and Fe–Ag Bimetallic Particles Produced by Electric Explosion of Two Wires

NASA Astrophysics Data System (ADS)

Lerner, M. I.; Bakina, O. V.; Pervikov, A. V.; Glazkova, E. A.; Lozhkomoev, A. S.; Vorozhtsov, A. B.

2018-05-01

X-ray phase analysis, transmission electron microscopy, and X-ray microanalysis were used to examine the structural-phase states of Fe-Cu and Fe-Ag bimetallic nanoparticles. The nanoparticles were obtained by the electric explosion of two twisted metal wires in argon atmosphere. It was demonstrated that the nanoparticles have the structure of Janus particles. Presence of the Janus particle structure in the samples indicates formation of binary melt under conditions of combined electric explosion of two wires. Phases based on supersaturated solid solutions were not found in the examined samples. The data obtained allow arguing that it is possible to achieve uniform mixing of the two-wire explosion products under the described experiment conditions.

MM/T Program for Three Color Light Emitting Diode Display Modules.

DTIC Science & Technology

1981-10-01

DAVID, G W LEWIS DARKAS AG -C 0566 UNCLASSIFIED DELET-TR-RO 0566 1 ML 1.0 ______ 220 1.25 _ 1 .r DELET-TR- 80-0566-1 Research and Development Technical...is transmitted, followed by the "Literal" address of the pixel LA I16170 Sit 1034373S U~ T I I TABLE I SHIFTED ASCU CHAR. BINARY DEC. ASCU 3fHARY DEC

Construction of plasmonic Ag modified phosphorous-doped ultrathin g-C3N4 nanosheets/BiVO4 photocatalyst with enhanced visible-near-infrared response ability for ciprofloxacin degradation.

PubMed

Deng, Yaocheng; Tang, Lin; Feng, Chengyang; Zeng, Guangming; Wang, Jiajia; Zhou, Yaoyu; Liu, Yani; Peng, Bo; Feng, Haopeng

2018-02-15

To realize the full utilization of solar energy, the design of highly efficient photocatalyst with improved visible-near-infrared photocatalysis performance has attracted great attentions for environment pollutant removal. In this work, we rationally employed the surface plasmon resonance effect of metallic Ag in the phosphorus doped ultrathin g-C 3 N 4 nanosheets (PCNS) and BiVO 4 composites to construct a ternary Ag@PCNS/BiVO 4 photocatalyst. It was applied for the photodegradation of ciprofloxacin (CIP), exhibiting 92.6% removal efficiency under visible light irradiation (λ>420nm) for 10mg/L CIP, and presenting enhanced photocatalytic ability than that of single component or binary nanocomposites under near-infrared light irradiation (λ>760nm). The improved photocatalytic activity of the prepared Ag@PCNS/BiVO 4 nanocomposite can be attributed to the synergistic effect among the PCNS, BiVO 4 and Ag, which not only improves the visible light response ability and hinders the recombination efficiency of the photogenerated electrons and holes, but also retains the strong the redox ability of the photogenerated charges. According to the trapping experiment and ESR measurements results, OH, h + and O 2 - all participated in the photocatalytic degradation process. Considering the SPR effect of metallic Ag and the established local electric field around the interfaces, a dual Z-scheme electrons transfer mechanism was proposed. Copyright © 2017 Elsevier B.V. All rights reserved.

Possible association of FAS and FASLG polymorphisms with the risk of idiopathic azoospermia in southeast Turkey.

PubMed

Balkan, Mahmut; Atar, Murat; Erdal, Mehmet Emin; Rustemoğlu, Aydin; Yildiz, Ismail; Gunesacar, Ramazan; Hatipoğlu, Namık Kemal; Bodakçi, Mehmet Nuri; Ay, Ozlem Izci; Çevik, Kenan

2014-06-01

To investigate the association of the genetic variants of FAS/FASLG cell death pathway genes in male infertility, we genotyped the FAS -670A/G, -1377G/A, and FASLG -124A/G single-nucleotide polymorphisms (SNPs) by real-time polymerase chain reaction in 108 infertile men with idiopathic azoospermia and in 125 proven fertile controls. The distribution of genotypes and alleles for SNPs at FAS -1377G/A and FASLG -124A/G loci were determined not to be statistically different between the case and control groups. However, the genotype frequencies of SNPs, FAS -670AA and FAS -670AG, were found to be significantly different between the case and control groups. Whereas the FAS -670AA genotype might be regarded as a higher predisposition for idiopathic azoospermia, FAS -670AG could be interpreted to mean that this genotype provides protection against idiopathic azoospermia. The study of combined genotype and haplotype frequencies has found statistically significant differences between case and control subjects for some combinations. The AA-GG binary genotype for the FAS670 and FAS1377 loci couple, in particular, may have a high degree of predisposition to idiopathic azoospermia. Our results suggest that FAS -670A/G SNP may be a genetic predisposing factor of idiopathic azoospermia among southeastern Anatolian men. Larger studies are needed to verify these findings. Furthermore, our data indicated a possible linkage between the FAS and FASLG genes and idiopathic azoospermia.

Photometry of symbiotic stars. X. EG And, Z And, BF Cyg, CH Cyg, V1329 Cyg, AG Dra, RW Hya, AX Per and IV Vir

NASA Astrophysics Data System (ADS)

Skopal, A.; Vanko, M.; Pribulla, T.; Wolf, M.; Semkov, E.; Jones, A.

2002-04-01

We present new photometric observations of EG And, Z And, BF Cyg, CH Cyg, V1329 Cyg, AG Dra, RW Hya, AX Per and IV Vir made in the standard Johnson UBVR system. The current issue summarizes observations of these objects to 2001 December. The main results can be summarized as follows: EG And: A periodic double-wave variation in all bands as a function of the orbital phase was confirmed. A maximum of the light changes was observed in U (Delta U ~ 0.5 mag). Z And: Our observations cover an active phase, which peaked around 8.4 in U at the beginning of 2000 December. Consequently, a gradual decrease in the star's brightness has been observed. BF Cyg: A periodic wave-like variation in the optical continuum reflects a quiescent phase of this star. A complex light curve (LC) profile was observed. CH Cyg: The recent episode of activity ended in Spring 2000. We determined the position of an eclipse in the outer binary at JD 2451426 +/- 3. Recent observations indicate a slow increase in the star's brightness. V1329 Cyg: Observations were made around a maximum at 2001.2. AG Dra: Our measurements from the Autumn of 2001 revealed a new eruption, which peaked at ~JD 2452217. RW Hya: The light minimum in our mean visual LC precedes the time of the spectroscopic conjunction of the giant in the binary. AX Per: A periodic wave-like variation was observed. Our recent observations revealed a secondary minimum at the orbital phase 0.5, seen best in the V and B bands. IV Vir: The LC displays a double-wave throughout the orbital cycle.

Taxonomic examination of longgu (Fossilia Ossis Mastodi, "dragon bone") and a related crude drug, longchi (Dens Draconis, "dragon tooth"), from Japanese and Chinese crude drug markets.

PubMed

Oguri, Kazuki; Nishioka, Yuichiro; Kobayashi, Yoshitsugu; Takahashi, Kyoko

2017-07-01

Longgu ("dragon bone," Ryu-kotsu, Fossilia Ossis Mastodi, or Os Draconis) is the only fossil crude drug listed in the Japanese Pharmacopoeia. All longgu in the current Japanese market is imported from China, where its resources are being depleted. Therefore, effective countermeasures are urgently needed to prevent resource depletion. One possible solution is the development of a substitute made from bones of contemporary animals that are closely related to the original animal source of the current longgu. However, no research has been conducted on the original animal source of longgu, except for a report on the longgu specimens present in the Shosoin Repository. Taxonomic examination was performed on the fossil specimens related to longgu which are owned by the Museum of Osaka University, Japan. In total, 20,939 fossil fragments were examined, of which 20,886 were mammalian fossils, and 246 of these fossils were classified into nine families. The longgu specimens from the Japanese market belonged to a relatively smaller variety of taxa than those from the Chinese market. Despite the variety of taxa in longgu, medical doctors using Kampo preparations with longgu have not reported any problems due to the presence of impurities in the original animal source. These results suggest that the effect of longgu is independent of its origin as long as it is closely related to the origin of the current longgu. Thus, despite the considerable effects of fossilization, our results could help in developing an optimal substitute for longgu.

The Light and Period Variations of the Eclipsing Binary BX Draconis

NASA Astrophysics Data System (ADS)

Park, Jang-Ho; Lee, Jae Woo; Kim, Seung-Lee; Lee, Chung-Uk; Jeon, Young-Beom

2013-02-01

New CCD photometric observations of BX Dra were carried out on 26 nights during the period from 2009 April to 2010 June. The long-term photometric behaviors of the system are obtained from detailed studies of the period and light variations, based on historical data and our new observations. All available light curves display total eclipses at secondary minima and inverse O'Connell effects with Max I fainter than Max II, which were satisfactorily modeled by adding a slightly time-varying hot spot on the primary star. A total of 87 times of minimum lights spanning over ˜74 yr, including our 22 timing measurements, were used for ephemeris computations. A detailed analysis of the O - C diagram disclosed that the orbital period shows an upward parabola in combination with a sinusoidal variation. The continuous increase of period at a rate of +5.65 × 10-7 d yr-1 is consistent with that calculated from the Wilson-Devinney synthesis code. It can be interpreted as a mass transfer from the secondary star to the primary at a rate of 2.74 × 10-7 M⊙ yr-1, which is one of the largest rates between components of the contact system. The most likely explanation of the sinusoidal variation having a period of 30.2 yr and a semiamplitude of 0.0062 d is a light-travel-time effect due to the existence of a circumbinary object. We suggest that BX Dra is probably a triple system, consisting of a primary star with a spectral type of F0, its secondary component of spectral type F1-2, and an unseen circumbinary object with a minimum mass of M3 = 0.23 M⊙.

AGS a set of UNIX commands for neutron data reduction

NASA Astrophysics Data System (ADS)

Bastian, C.

1997-02-01

The output of a detector system recording neutron-induced nuclear reactions consists of a set of multichannel spectra and of scaler/counter values. These data must be reduced - i.e.. corrected and combined - to produce a clean energy spectrum of the reaction cross-section with a covariance estimate suitable for evaluation. The reduction process may be broken down into a sequence of operations. We present a set of reduction operations implemented as commands on a UNIX system. Every operation reads spectra from a file and appends results as new spectra to the same file. The binary file format AGS used thereby records the spectra as named entities including a set of neutron energy values and a corresponding set of values with their correlated and uncorrelated uncertainties.

Exploring the Photovoltaic Performance of All-Inorganic Ag2PbI4/PbI2 Blends.

PubMed

Frolova, Lyubov A; Anokhin, Denis V; Piryazev, Alexey A; Luchkin, Sergey Yu; Dremova, Nadezhda N; Troshin, Pavel A

2017-04-06

We present an all-inorganic photoactive material composed of Ag 2 PbI 4 and PbI 2 , which shows unexpectedly good photovoltaic performance in planar junction solar cells delivering external quantum efficiencies of ∼60% and light power conversion efficiencies of ∼3.9%. The revealed characteristics are among the best reported to date for metal halides with nonperovskite crystal structure. Most importantly, the obtained results suggest a possibility of reaching high photovoltaic efficiencies for binary and, probably, also ternary blends of different inorganic semiconductor materials. This approach, resembling the bulk heterojunction concept guiding the development of organic photovoltaics for two decades, opens wide opportunities for rational design of novel inorganic and hybrid materials for efficient and sustainable photovoltaic technologies.

Template method to controllable synthesis 3D porous NiCo2O4 with enhanced capacitance and stability for supercapacitors.

PubMed

Bai, Yang; Wang, Ranran; Lu, Xiaoyu; Sun, Jing; Gao, Lian

2016-04-15

We present a facile template method to fabricate NiCo2O4 (NCO) composites with 3D porous structure as electrodes for supercapacitors. SiO2 sol is used as the template to prevent the aggregation of NCO and construct the porous structure with high specific surface area. Meanwhile, the binary metal oxides not only inherit the merits of single nickel oxides or cobalt oxides, but also show superior properties to promote the capacitance. The uniform structure of NCO12 (SiO2/NCO=1:2) is obtained through controlling the mass ratio of SiO2 and NCO. Owing to the dual advantages of porous structure and binary system, NCO12 composites exhibit highly enhanced electrochemical performance compared with those of directly prepared NCO, NCO21 (SiO2/NCO=1:0.5) and NCO14 (SiO2/NCO=1:4). The specific capacitance of NCO12 composite is about 1389 Fg(-1) at 1 Ag(-1). At 4 Ag(-1), the capacitance is still as high as 1090 Fg(-1) together with capacitance retention of 80% over 2500 cycles. The capacitance and stability are higher than those of most previously reported pure NCO composites, which make it a very promising electrode material for energy storage. Copyright © 2016 Elsevier Inc. All rights reserved.

Validity of Binary Collision Theory in Ion-Surface Interactions at 50-500 eV

NASA Astrophysics Data System (ADS)

Gordon, Michael; Giapis, Kostas

2003-10-01

Ion-surface interactions in the 50-500 eV regime have become increasingly important in plasma processing. Concerns exist in literature about the validity of the binary collision approximation (BCA) at low impact energies because peculiarities are frequently seen in the scattered ion energy distribution. Sub-surface processes, multiple bouncing, and super-elastic phenomena have all been hypothesized. This talk will explore the usefulness of BCA theory in predicting energy transfer during ion-surface collisions in the 50-500 eV energy range. Well-defined beams of rare gas ions (Ne, Ar, Kr) were scattered off semiconductor (Si, Ge) and metal surfaces (Ag, Au, Ni, Nb) to measure energy loss upon impact. The ion beams were produced from a floating ICP reactor coupled to a small accelerator beamline for transport and mass filtering. Exit channel energies were measured using a 90 gegree electrostatic sector coupled to a quadrupole mass filter with single ion detection capability. Although the BCA presents an over-simplified picture of the collision process, our results demonstrate that it is remarkably accurate in the low energy range for a variety of projectile-target combinations. In addition, reactive ion scattering of O2+ and O+ on inert and reactive surfaces (Au vs. Ag, Pt) suggests there may be rather high energy threshold processes which determine exit channel selectivity.

Phase-field crystal modeling of compositional domain formation in ultrathin films.

PubMed

Muralidharan, Srevatsan; Haataja, Mikko

2010-09-17

Bulk-immiscible binary systems often form stress-induced miscible alloy phases when deposited on a substrate. Both alloying and surface dislocation formation lead to the decrease of the elastic strain energy, and the competition between these two strain-relaxation mechanisms gives rise to the emergence of pseudomorphic compositional nanoscale domains, often coexisting with a partially coherent single phase. In this work, we develop a phase-field crystal model for compositional patterning in monolayer aggregates of binary metallic systems. We first demonstrate that the model naturally incorporates the competition between alloying and misfit dislocations, and quantify the effects of misfit and line tension on equilibrium domain size. Then, we quantitatively relate the parameters of the phase-field crystal model to a specific system, CoAg/Ru(0001), and demonstrate that the simulations capture experimentally observed morphologies.

Antibacterial and biological characteristics of plasma sprayed silver and strontium doped hydroxyapatite coatings

PubMed Central

Fielding, Gary A.; Roy, Mangal; Bandyopadhyay, Amit

2012-01-01

Infection in primary total joint prostheses is estimated to occur in up to 3% of all surgeries. As a measure to improve the antimicrobial properties of implant materials, silver (Ag) was incorporated into plasma sprayed hydroxyapatite (HA) coatings. To offset potential cytotoxic effects of Ag in the coatings, strontium (Sr) was also added as a binary dopant. HA powder were doped with 2.0 wt% Ag2O, 1.0 wt% SrO and the powder was then heat treated at 800° C. Titanium substrates were coated using a 30 kW plasma spray system equipped with a supersonic nozzle. X-ray diffraction (XRD) confirmed the phase purity and high crystallinity of the coatings. Samples were evaluated for mechanical stability by adhesive bond strength testing. Results show that the addition of dopants did not affect the overall bond strength of the coatings. The antibacterial efficacies of the coatings were tested against Pseudomonas aeruginosa. Samples that contained the Ag2O dopant were found to be highly effective against the bacterial colonization. In vitro cell-material interactions using human fetal osteoblast (hFOB) cells were characterized by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for cell viability, field emission scanning electron microscopy (FESEM) for cell morphology and confocal imaging for the important differentiation marker alkaline phosphatase (ALP). Our results showed evidence of cytotoxic effects in the Ag-HA coatings, characterized by poor cellular morphology and cell death and nearly complete impediment of functional ALP activity. The addition of SrO to Ag-HA coatings was able to effectively offset these negative effects and improve the performance when compared to pure HA coated samples. PMID:22487928

Time- and energy-efficient solution combustion synthesis of binary metal tungstate nanoparticles with enhanced photocatalytic activity.

PubMed

Thomas, Abegayl; Janáky, Csaba; Samu, Gergely F; Huda, Muhammad N; Sarker, Pranab; Liu, J Ping; van Nguyen, Vuong; Wang, Evelyn H; Schug, Kevin A; Rajeshwar, Krishnan

2015-05-22

In the search for stable and efficient photocatalysts beyond TiO2 , the tungsten-based oxide semiconductors silver tungstate (Ag2 WO4 ), copper tungstate (CuWO4 ), and zinc tungstate (ZnWO4 ) were prepared using solution combustion synthesis (SCS). The tungsten precursor's influence on the product was of particular relevance to this study, and the most significant effects are highlighted. Each sample's photocatalytic activity towards methyl orange degradation was studied and benchmarked against their respective commercial oxide sample obtained by solid-state ceramic synthesis. Based on the results herein, we conclude that SCS is a time- and energy-efficient method to synthesize crystalline binary tungstate nanomaterials even without additional excessive heat treatment. As many of these photocatalysts possess excellent photocatalytic activity, the discussed synthetic strategy may open sustainable materials chemistry avenues to solar energy conversion and environmental remediation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Destructive Clustering of Metal Nanoparticles in Chalcogenide and Oxide Glassy Matrices.

PubMed

Shpotyuk, M V; Shpotyuk, O I; Cebulski, J; Kozyukhin, S

2016-12-01

The energetic χ-criterion is developed to parameterize difference in the origin of high-order optical non-linearity associated with metallic atoms (Cu, Ag, Au) embedded destructively in oxide- and chalcogenide glasses. Within this approach, it is unambiguously proved that covalent-bonded networks of soft semiconductor chalcogenides exemplified by binary As(Ge)-S(Se) glasses differ essentially from those typical for hard dielectric oxides like vitreous silica by impossibility to accommodate pure agglomerates of metallic nanoparticles. In an excellence according to known experimental data, it is suggested that destructive clustering of nanoparticles is possible in Cu-, Ag-, and Au-ion-implanted dielectric oxide glass media, possessing a strongly negative χ-criterion. Some recent speculations trying to ascribe equally this ability to soft chalcogenide glasses despite an obvious difference in the corresponding bond dissociation energies have been disclosed and criticized as inconclusive.

Optical and photoelectrochemical performance study based on n-ZnO nanorod arrays/p-CuAlO2 laminar films/Ni heterojunction

NASA Astrophysics Data System (ADS)

Ding, Juan; Yang, Haibin; Deng, Weiwen

2014-06-01

A novel ZnO nanorod arrays (NRs)/CuAlO2 laminar films heterojunction nanostructure was grown on the substrate of Ni plates using sol-gel synthesis for laminar films and subsequent hydrothermal reaction for nanorod arrays. The surface morphology, structure, optical and photoelectrochemical behaviors of this heterojunction were considered. Two significant absorption peaks of UV-vis spectra and a favorable forward current to reverse current ratio at applied voltage of -0.7 V to +2 V were observed in this heterojunction. Furthermore, the photoelectrochemical property was indicated that the highest photocurrent of 0.67 mA/cm2 was obtained under AM 1.5 illumination (vs Ag/AgCl). This heterojunction will play an important role in the optoelectronic fields and can be extended to other binary or ternary oxide compositions for optoelectronic applications.

Off-stoichiometric silver antimony telluride: An experimental study of transport properties with intrinsic and extrinsic doping

DOE PAGES

Nielsen, Michele D.; Jaworski, Christopher M.; Heremans, Joseph P.

2015-03-20

AgSbTe 2 is a thermoelectric semiconductor with an intrinsically low thermal conductivity and a valence band structure that is favorable to obtaining a high thermoelectric figure of merit zT. It also has a very small energy gap Eg ~ 7.6 ± 3 meV. As this gap is less than the thermal excitation energy at room temperature, near-intrinsic AgSbTe 2 is a two carrier system having both holes (concentration p) and electrons ( n). Good thermoelectric performance requires heavy p-type doping ( p > > n). This can be achieved with native defects or with extrinsic doping, e.g. with transition metalmore » element. The use of defect doping is complicated by the fact that many of the ternary Ag-Sb-Te and pseudo-binary Sb 2Te 3-Ag 2Te phase diagrams are contradictory. This paper determines the compositional region most favorable to creating a single phase material. Through a combination of intrinsic and extrinsic doping, values of zT > 1 are achieved, though not on single-phased material. In addition, we show that thermal conductivity is not affected by defects, further demonstrating that the low lattice thermal conductivity of I-V-VI 2 materials is due to an intrinsic mechanism, insensitive to changes in defect structure.« less

Predicting the thermodynamic stability of double-perovskite halides from density functional theory

DOE PAGES

Han, Dan; Zhang, Tao; Huang, Menglin; ...

2018-05-24

Recently, a series of double-perovskite halide compounds such as Cs 2AgBiCl 6 and Cs 2AgBiBr 6 have attracted intensive interest as promising alternatives to the solar absorber material CH 3NH 3PbI 3 because they are Pb-free and may exhibit enhanced stability. The thermodynamic stability of a number of double-perovskite halides has been predicted based on density functional theory (DFT) calculations of compound formation energies. In this paper, we found that the stability prediction can be dependent on the approximations used for the exchange-correlation functionals, e.g., the DFT calculations using the widely used Perdew, Burke, Ernzerhof (PBE) functional predict that Csmore » 2AgBiBr 6 is thermodynamically unstable against phase-separation into the competing phases such as AgBr, Cs 2AgBr 3, Cs 3Bi 2Br 9, etc., obviously inconsistent with the good stability observed experimentally. The incorrect prediction by the PBE calculation results from its failure to predict the correct ground-state structures of AgBr, AgCl, and CsCl. By contrast, the DFT calculations based on local density approximation, optB86b-vdW, and optB88-vdW functionals predict the ground-state structures of these binary halides correctly. Furthermore, the optB88-vdW functional is found to give the most accurate description of the lattice constants of the double-perovskite halides and their competing phases. Given these two aspects, we suggest that the optB88-vdW functional should be used for predicting thermodynamic stability in the future high-throughput computational material design or the construction of the Materials Genome database for new double-perovskite halides. As a result, using different exchange-correlation functionals has little influence on the dispersion of the conduction and the valence bands near the electronic bandgap; however, the calculated bandgap can be affected indirectly by the optimized lattice constant, which varies for different functionals.« less

Predicting the thermodynamic stability of double-perovskite halides from density functional theory

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

Han, Dan; Zhang, Tao; Huang, Menglin

Recently, a series of double-perovskite halide compounds such as Cs 2AgBiCl 6 and Cs 2AgBiBr 6 have attracted intensive interest as promising alternatives to the solar absorber material CH 3NH 3PbI 3 because they are Pb-free and may exhibit enhanced stability. The thermodynamic stability of a number of double-perovskite halides has been predicted based on density functional theory (DFT) calculations of compound formation energies. In this paper, we found that the stability prediction can be dependent on the approximations used for the exchange-correlation functionals, e.g., the DFT calculations using the widely used Perdew, Burke, Ernzerhof (PBE) functional predict that Csmore » 2AgBiBr 6 is thermodynamically unstable against phase-separation into the competing phases such as AgBr, Cs 2AgBr 3, Cs 3Bi 2Br 9, etc., obviously inconsistent with the good stability observed experimentally. The incorrect prediction by the PBE calculation results from its failure to predict the correct ground-state structures of AgBr, AgCl, and CsCl. By contrast, the DFT calculations based on local density approximation, optB86b-vdW, and optB88-vdW functionals predict the ground-state structures of these binary halides correctly. Furthermore, the optB88-vdW functional is found to give the most accurate description of the lattice constants of the double-perovskite halides and their competing phases. Given these two aspects, we suggest that the optB88-vdW functional should be used for predicting thermodynamic stability in the future high-throughput computational material design or the construction of the Materials Genome database for new double-perovskite halides. As a result, using different exchange-correlation functionals has little influence on the dispersion of the conduction and the valence bands near the electronic bandgap; however, the calculated bandgap can be affected indirectly by the optimized lattice constant, which varies for different functionals.« less

Durable pd-based alloy and hydrogen generation membrane thereof

DOEpatents

Benn, Raymond C.; Opalka, Susanne M.; Vanderspurt, Thomas Henry

2010-02-02

A durable Pd-based alloy is used for a H.sub.2-selective membrane in a hydrogen generator, as in the fuel processor of a fuel cell plant. The Pd-based alloy includes Cu as a binary element, and further includes "X", where "X" comprises at least one metal from group "M" that is BCC and acts to stabilize the .beta. BCC phase for stability during operating temperatures. The metal from group "M" is selected from the group consisting of Fe, Cr, Nb, Ta, V, Mo, and W, with Nb and Ta being most preferred. "X" may further comprise at least one metal from a group "N" that is non-BCC, preferably FCC, that enhances other properties of the membrane, such as ductility. The metal from group "N" is selected from the group consisting of Ag, Au, Re, Ru, Rh, Y, Ce, Ni, Ir, Pt, Co, La and In. The at. % of Pd in the binary Pd--Cu alloy ranges from about 35 at. % to about 55 at. %, and the at. % of "X" in the higher order alloy, based on said binary alloy, is in the range of about 1 at. % to about 15 at. %. The metals are selected according to a novel process.

TEOA-mediated formation of hollow core-shell structured CoNi2S4 nanospheres as a high-performance electrode material for supercapacitors

NASA Astrophysics Data System (ADS)

Liang, Jun; Li, Meng; Chai, Yao; Luo, Min; Li, Li

2017-09-01

In this study, we report for the first time a cost-effective and general approach for the high-yield synthesis of a hierarchical core-shell and hollow structure of ternary CoNi2S4 in a triethanolamine (TEOA)-assisted hydrothermal system. It is found that a continuous increase in TEOA usages facilitates the formation and transformation of hierarchical CoNi2S4 hollow nanospheres, and the formation mechanism of the unique structure is revealed to be assembly-then-inside-out evacuation and Ostwald ripening mechanism during the sulfidation process. More importantly, when used as faradaic electrode for supercapacitors, the hierarchical hollow CoNi2S4 nanospheres display not only exceptional pseudocapacitve performance with high specific capacitance (2035 Fg-1 at 1 Ag-1) and excellent rate capability (1215 Fg-1 at 20 Ag-1), but also superior cycling stability, with only about 8.7% loss over 3000 cycles at 10 Ag-1. This work can provide some guidance for us in the structural and compositional tuning of mixed binary-metal sulfides toward many desired applications.

Nanoscale diffusive memristor crossbars as physical unclonable functions.

PubMed

Zhang, R; Jiang, H; Wang, Z R; Lin, P; Zhuo, Y; Holcomb, D; Zhang, D H; Yang, J J; Xia, Q

2018-02-08

Physical unclonable functions have emerged as promising hardware security primitives for device authentication and key generation in the era of the Internet of Things. Herein, we report novel physical unclonable functions built upon the crossbars of nanoscale diffusive memristors that translate the stochastic distribution of Ag clusters in a SiO 2 matrix into a random binary bitmap that serves as a device fingerprint. The random dispersion of Ag led to an uneven number of clusters at each cross-point, which in turn resulted in a stochastic ability to switch in the Ag:SiO 2 diffusive memristors in an array. The randomness of the dispersion was a barrier to fingerprint cloning and the unique fingerprints of each device were persistent after fabrication. Using an optimized fabrication procedure, we maximized the randomness and achieved an inter-class Hamming distance of 50.68%. We also discovered that the bits were not flipping after over 10 4 s at 400 K, suggesting superior reliability of our physical unclonable functions. In addition, our diffusive memristor-based physical unclonable functions were easy to fabricate and did not require complicated post-processing for digitization and thus, provide new opportunities in hardware security applications.

Microstructure and Interfacial Reactions During Vacuum Brazing of Stainless Steel to Titanium Using Ag-28 pct Cu Alloy

NASA Astrophysics Data System (ADS)

Laik, A.; Shirzadi, A. A.; Sharma, G.; Tewari, R.; Jayakumar, T.; Dey, G. K.

2015-02-01

Microstructural evolution and interfacial reactions during vacuum brazing of grade-2 Ti and 304L-type stainless steel (SS) using eutectic alloy Ag-28 wt pct Cu were investigated. A thin Ni-depleted zone of -Fe(Cr, Ni) solid solution formed on the SS-side of the braze zone (BZ). Cu from the braze alloy, in combination with the dissolved Fe and Ti from the base materials, formed a layer of ternary compound , adjacent to Ti in the BZ. In addition, four binary intermetallic compounds, CuTi, CuTi, CuTi and CuTi formed as parallel contiguous layers in the BZ. The unreacted Ag solidified as islands within the layers of CuTi and CuTi. Formation of an amorphous phase at certain locations in the BZ could be revealed. The -Ti(Cu) layer, formed due to diffusion of Cu into Ti-based material, transformed to an -Ti + CuTi eutectoid with lamellar morphology. Tensile test showed that the brazed joints had strength of 112 MPa and failed at the BZ. The possible sequence of events that led to the final microstructure and the mode of failure of these joints were delineated.

Investigation of Pd-Modified Ag-CuO Air Braze Filler Metals

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

Darsell, Jens T.; Hardy, John S.; Kim, Jin Yong

2006-01-10

Palladium was added as a ternary component to a series of silver - copper oxide alloys in an effort to increase the use temperature of these materials for potential ceramic air brazing applications. Large portions of the silver component of the Ag-CuO system were substituted by palladium forming the following alloys: (100-y)[(100-z)Pd - (z)Ag] - (y)CuOx where y = 0 - 34 mol% CuOx, z = 50 - 100 mol% silver, and x = 0, 0.5, and 1, denoting copper metal, Cu2O, or CuO. From differential scanning calorimetry, it was determined that the addition of palladium causes an increase inmore » the solidus and liquidus temperatures of the resulting Pd-Ag-CuO brazes. In general, the liquidus was found to increase by approximately 220°C for the (100-y)(25Pd - 75Ag) - (z)CuOx filler metal compositions relative to comparable Ag-CuOx alloys. Likewise, the solidus was found to increase for these alloys, respectively by 185°C and 60°C, respectively for CuOx contents of y = 0 - 1mol% and 4 - 10 mol%. For the (100-y)(50Pd - 50Ag) - (y)CuOx alloys, the solidus increased between 280 - 390°C over a copper oxide compositional range of x = 0 to 8 mol%. It was determined from sessile drop experiments that palladium causes an increase in the wetting angle for all of the samples tested. Alloy compositions of (100-y)(25Pd - 75Ag) - (y)CuOx displayed increased wetting angles of 5-20° relative to comparable binary compositions. (100-y)(50Pd - 50Ag) - (y)CuOx alloys exhibited an increase in contact angle of 10-60° and compositions containing less than 10 mol% CuOx were not able to wet the substrate. Scanning electron microscopy indicates that the microstructure of the braze consists of Ag-Pd solid solution with CuOx precipitates. In general, a reaction layer consisting of CuAlO2 forms adjacent to the alumina substrate. However, the formation of this layer is apparently hindered by the addition of large amounts of palladium, causing poor wetting behavior, as denoted by substantial porosity found along the braze/substrate interface. The reduction in wettability can be compensated by increasing the CuO content slightly.« less

Rotation periods of open-cluster stars, 2

NASA Technical Reports Server (NTRS)

Prosser, Charles F.; Shetrone, Matthew D.; Marilli, Ettore; Catalano, Santo; Williams, Scott D.; Backman, Dana E.; Laaksonen, Bentley D.; Adige, Vikram; Marschall, Laurence A.; Stauffer, John R.

1993-01-01

We present the results from a photometric monitoring program of 21 stars observed during 1992 in the Pleiades and Alpha Persei open clusters. Period determinations for 16 stars are given, 13 of which are the first periods reported for these stars. Brightness variations for an additional five cluster stars are also given. One K dwarf member of the alpha Per cluster is observed to have a period of rotation of only 4.39 hr. perhaps the shortest period currently known among BY Draconis variables. The individual photometric measurements have been deposited with the NSSDC. Combining current X-ray flux determinations with known photometric periods, we illustrate the X-ray activity/rotation relation among Pleiades K dwarfs based on available data.

THE FLARE-ONA OF EK DRACONIS

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

Ayres, Thomas R., E-mail: Thomas.Ayres@Colorado.edu

2015-07-15

EK Draconis (HD 129333: G1.5 V) is a well-known young (50 Myr) solar analog. In 2012, Hubble Space Telescope returned to EK Dra to follow up a far-ultraviolet (FUV) SNAPshot visit by Cosmic Origins Spectrograph (COS) two years earlier. The brief SNAP pointing had found surprisingly redshifted, impulsively variable subcoronal “hot-line” emission of Si iv 1400 Å (T ∼ 8 × 10{sup 4} K). Serendipitously, the 2012 follow-on program witnessed one of the largest FUV flares ever recorded on a sunlike star, which again displayed strong redshifts (downflows) of 30–40 km s{sup −1}, even after compensating for small systematics inmore » the COS velocity scales, uncovered through a cross-calibration by Space Telescope Imaging Spectrograph (STIS). The (now reduced, but still substantial) ∼10 km s{sup −1} hot-line redshifts outside the flaring interval did not vary with rotational phase, so cannot be caused by “Doppler imaging” (bright surface patches near a receding limb). Density diagnostic O iv] 1400 Å multiplet line ratios of EK Dra suggest n{sub e} ∼ 10{sup 11} cm{sup −3}, an order of magnitude larger than in low-activity solar twin α Centauri A, but typical of densities inferred in large stellar soft X-ray events. The self-similar FUV hot-line profiles between the flare decay and the subsequent more quiet periods, and the unchanging but high densities, reinforce a long-standing idea that the coronae of hyperactive dwarfs are flaring all the time, in a scale-free way; a flare-ona if you will. In this picture, the subsonic hot-line downflows probably are a byproduct of the post-flare cooling process, something like “coronal rain” on the Sun. All in all, the new STIS/COS program documents a complex, energetic, dynamic outer atmosphere of the young sunlike star.« less

Screening on binary Ti alloy with excellent mechanical property and castability for dental prosthesis application

PubMed Central

Li, H. F.; Qiu, K. J.; Yuan, W.; Zhou, F. Y.; Wang, B. L.; Li, L.; Zheng, Y. F.; Liu, Y. H.

2016-01-01

In the present study, the microstructure, mechanical property, castability, corrosion behavior and in vitro cytocompatibility of binary Ti–2X alloys with various alloying elements, including Ag, Bi, Ga, Ge, Hf, In, Mo, Nb, Sn and Zr, were systematically investigated, in order to assess their potential applications in dental field. The experimental results showed that all binary Ti‒2X alloys consisted entirely α–Ti phase. The tensile strength and microhardness of Ti were improved by adding alloying elements. The castability of Ti was significantly improved by separately adding 2 wt.% Bi, Ga, Hf, Mo, Nb, Sn and Zr. The corrosion resistance of Ti in both normal artificial saliva solution (AS) and extreme artificial saliva solution (ASFL, AS with 0.2 wt.% NaF and 0.3 wt.% lactic acid) has been improved by separately adding alloying elements. In addition, the extracts of studied Ti‒2X alloys produced no significant deleterious effect to both fibroblasts L929 cells and osteoblast-like MG63 cells, indicating a good in vitro cytocompatibility, at the same level as pure Ti. The combination of enhanced mechanical properties, castability, corrosion behavior, and in vitro cytocompatibility make the developed Ti‒2X alloys have great potential for future stomatological applications. PMID:27874034

Metastable phase in binary and ternary 12-carat gold alloys at low temperature

NASA Astrophysics Data System (ADS)

Lamiri, Imene; Abdelbaky, Mohammed S. M.; Hamana, Djamel; García-Granda, Santiago

2018-04-01

Low temperature phase transitions in 12-carat gold alloys have been investigated for binary Au-Cu and ternary Au-Cu-Ag compositions. The thermal analyses investigations using differential scanning calorimetry (DSC) and the dilatometry were performed in the 50–300 °C temperature range in order to detect the structural transformations. The thermal analyses were carried out on annealed samples at 700 °C for two hour followed by water quenching. They reveal an important new reaction for both used compositions and both thermal techniques confirm each other. This reaction has been assessed as pre-ordering reaction. SEM and STM imaging were performed on annealed samples at 700 °C for two hours and water quenched followed by a heating from room temperature up to the temperature of the new peaks obtained in the thermal study. The imaging reveals the relationship between the pre-ordering reaction and the surface aspect presented in the fact of dendrite precipitates. A series of SEM observation have been performed in order to follow the kinetic of the observed precipitates by the way of several series of heating up, from 140 to 220 °C for the binary composition and from 100 to 180 °C for the ternary composition. Furthermore, this study shows that the silver accelerates the ordering reaction.

Synthesis of the new quaternary sulfides K[sub 2]Y[sub 4]Sn[sub 2]S[sub 11] and BaLnAgS[sub 3] (Ln = Er, Y, Gd) and the structures of K[sub 2]Y[sub 4]Sn[sub 2]S[sub 11] and BaErAgS[sub 3

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

Wu, Ping; Ibers, J.A.

1994-05-01

Several new quarternary sulfides, K[sub 2]Y[sub 4]Sn[sub 2]S[sub 11] and BaLnAgS[sub 3] (Ln = Er, Y, Gd), have been synthesized by the reaction of the constituent binary chalcogenides and elements at 1000[degrees]C. The crystal structures of K[sub 2]Y[sub 4]Sn[sub 2]S[sub 11] and BaErAgS[sub 3] have been determined by single-crystal X-ray diffraction techniques. Crystal data: K[sub 2]Y[sub 4]Sn[sub 2]S[sub 11]-space group D[sup 8][sub 4h] - P4/ncc, M = 1023.88, Z = 4, a = 8.587(1), c = 27.892(4) [angstrom] (T = 115 K), V = 2056.7(4) [angstrom][sup 3], R[sub W](F[sup 2]) = 0.093 for 1965 observations having F[sup 2][sub 0] >more » 2[sigma](F[sup 2][sub 0]); BaEr AgS[sub 3]-space group C[sup 3][sub 2H] - C2/m, M = 508.65, Z = 4, a = 17.340(4), b = 4.014(1), x = 8.509(2) [angstrom], [beta] = 103.23(3)[degrees], (T = 115 K), V = 576.5(2) [angstrom][sup 3], R[sub W](F[sup 2]) = 0.049 for 1404 observations and 48 variables, R(F) = 0.018 for 1299 observations having F[sup 2][sub 0] > 2[sigma](F[sup 2][sub 0]). In both structures, the rare-earth atoms have octahedral coordination and the octahedra form slabs through edge- and corner-sharing. These slabs are separated by K[sup +] Ba[sup 2+] cations, and are crosslinked into three-dimensional frameworks by Sn[sub 2]S[sub 6] units as edge-sharing SnS[sub 4] tetrahedral pairs in K[sub 2]Y[sub 4]Sn[sub 2]S[sub 11], and by Ag[sub 2]S[sub 9] units as corner-sharing trigonal-bipyramidal AgS[sub 5] pairs in BaEr AgS[sub 3]. From their powder diffraction patterns, BaYAgS[sub 3] and Ba GdAgS[sub 3] appear to be isostructural with BaErAgS[sub 3].« less

Antimicrobial properties of ternary eutectic aluminum alloys.

PubMed

Hahn, Claudia; Hans, Michael; Hein, Christina; Dennstedt, Anne; Mücklich, Frank; Rettberg, Petra; Hellweg, Christine Elisabeth; Leichert, Lars Ingo; Rensing, Christopher; Moeller, Ralf

2018-06-27

Several Escherichia coli deletion mutants of the Keio collection were selected for analysis to better understand which genes may play a key role in copper or silver homeostasis. Each of the selected E. coli mutants had a deletion of a single gene predicted to encode proteins for homologous recombination or contained functions directly linked to copper or silver transport or transformation. The survival of these strains on pure copper surfaces, stainless steel, and alloys of aluminum, copper and/or silver was investigated. When exposed to pure copper surfaces, E. coli ΔcueO was the most sensitive, whereas E. coli ΔcopA was the most resistant amongst the different strains tested. However, we observed a different trend in sensitivities in E. coli strains upon exposure to alloys of the system Al-Ag-Cu. While minor antimicrobial effects were detected after exposure of E. coli ΔcopA and E. coli ΔrecA to Al-Ag alloys, no effect was detected after exposure to Al-Cu alloys. The release of copper ions and cell-associated copper ion concentrations were determined for E. coli ΔcopA and the wild-type E. coli after exposure to pure copper surfaces. Altogether, compared to binary alloys, ternary eutectic alloys (Al-Ag-Cu) had the highest antimicrobial effect and thus, warrant further investigation.

Phase equilibria in the quasiternary system Ag2S-Ga2S3-In2S3 and optical properties of (Ga55In45)2S300, (Ga54.59In44.66Er0.75)2S300 single crystals

NASA Astrophysics Data System (ADS)

Ivashchenko, I. A.; Danyliuk, I. V.; Olekseyuk, I. D.; Pankevych, V. Z.; Halyan, V. V.

2015-07-01

The quasiternary system Ag2S-Ga2S3-In2S3 was investigated by differential thermal, X-ray diffraction analyses. The phase diagram of the Ga2S3-In2S3 system and nine polythermal sections, isothermal section at 820 K and the liquidus surface projection were constructed. The existence of the large solid solutions ranges of binary and ternary compounds was established. The range of the existence of the quaternary phase AgGaxIn5-xS8 (2.25≤x≤2.85) at 820 K was determined. The single crystals (Ga55In45)2S300 and (Ga54.59In44.66Er0.75)2S300 were grown by a directional crystallization method from solution-melt. Optical absorption spectra in the 500-1600 nm range were recorded. The luminescence of the (Ga54.59In44.66Er0.75)2S300 single crystal shows a maximum at 1530 nm for the excitation wavelengths of 532 and 980 nm at 80 and 300 K.

Interface structure and contact melting in AgCu eutectic. A molecular dynamics study

NASA Astrophysics Data System (ADS)

Bystrenko, O.; Kartuzov, V.

2017-12-01

Molecular dynamics simulations of the interface structure in binary AgCu eutectic were performed by using the realistic EAM potential. In simulations, we examined the time dependence of the total energy in the process of equilibration, the probability distributions, the composition profiles for the components, and the component diffusivities within the interface zone. It is shown that the relaxation to the equilibrium in the solid state is accompanied by the formation of the steady disordered diffusion zone at the boundary between the crystalline components. At higher temperatures, closer to the eutectic point, the increase in the width of the steady diffusion zone is observed. The particle diffusivities grow therewith to the numbers typical for the liquid metals. Above the eutectic point, the steady zone does not form, instead, the complete contact melting in the system occurs. The results of simulations indicate that during the temperature increase the phenomenon of contact melting is preceded by the similar process spatially localized in the vicinity of the interface.

The influence of gravity on the precise measurement of solute diffusion coefficients in dilute liquid metals and metalloids.

PubMed

Smith, Reginald W; Zhu, Xiaohe; Tunnicliffe, Mark C; Smith, Timothy J N; Misener, Lowell; Adamson, Josee

2002-10-01

It is now well known that the diffusion coefficient (D) measured in a laboratory in low earth orbit (LEO) is less than the corresponding value measured in a terrestrial laboratory. However, all LEO laboratories are subject to transient accelerations (g-jitter) superimposed on the steady reduced gravity environment of the space platform. In measurements of the diffusion coefficients for dilute binary alloys of Pb-(Ag, Au,Sb), Sb-(Ga,In), Bi-(Ag,Au,Sb), Sn-(Au,Sb), Al-(Fe, Ni,Si), and In-Sb in which g-jitter was suppressed, it was found that D proportional to T (temperature) if g-jitter was suppressed, rather than D proportional to T(2) as observed by earlier workers with g-jitter present. Furthermore, when a forced g-jitter was applied to a diffusion couple, the value measured for D increased. The significance of these results is reviewed in the light of recent work in which ab initio molecular dynamics simulations predicted a D proportional to T relationship.

Application of anaerobic granular sludge for competitive biosorption of methylene blue and Pb(II): Fluorescence and response surface methodology.

PubMed

Shi, Li; Wei, Dong; Ngo, Huu Hao; Guo, Wenshan; Du, Bin; Wei, Qin

2015-10-01

This study assessed the biosorption of anaerobic granular sludge (AGS) and its capacity as a biosorbent to remove Pb(II) and methylene blue (MB) from multi-components aqueous solution. It emerged that the biosorption data fitted well to the pseudo-second-order and Langmuir adsorption isotherm models in both single and binary systems. In competitive biosorption systems, Pb(II) and MB will suppress each other's biosorption capacity. Spectroscopic analysis, including Fourier transform infrared spectroscopy (FTIR) and fluorescence spectroscopy were integrated to explain this interaction. Hydroxyl and amine groups in AGS were the key functional groups for sorption. Three-dimensional excitation-emission matrix (3D-EEM) implied that two main protein-like substances were identified and quenched when Pb(II) or MB were present. Response surface methodology (RSM) confirmed that the removal efficiency of Pb(II) and MB reached its peak when the concentration ratios of Pb(II) and MB achieved a constant value of 1. Copyright © 2015 Elsevier Ltd. All rights reserved.

Rotational modulation and flares on RS Canum Venaticorum and BY Draconis-type stars. XV - Observations of Proxima Centauri and solar calibration data

NASA Technical Reports Server (NTRS)

Haisch, B. M.; Butler, C. J.; Foing, B.; Rodono, M.; Giampapa, M. S.

1990-01-01

Results are reported from simultaneous Exosat and IUE observations of flaring in Proxima Cen on March 2, 1985. The data are presented in extensive tables and sample spectra and discussed in detail. The peak emission of the soft-X-ray flare is found to be about 3 x 10 to the 27th erg/sec, with energy about 3 x 10 to the 30th erg and an associated increase in Mg II flux to 17,000-67,000 erg/sq cm sec, or about an order of magnitude lower than the solar value. The presence of flare- and microflare-related processes heating the corona is inferred.

'Marginal' BY Draconis stars

NASA Technical Reports Server (NTRS)

Bopp, Bernard W.

1987-01-01

Spectroscopic observations of 52 dK-dM stars, obtained at 640-665 nm (with spectral resolution 70-90 pm) using CCD detectors on the coude-feed telescope at KPNO since 1982, are reported. Data for four stars found to have diluted absorption or weak emission above continuum at H-alpha are presented in tables and spectra and discussed in detail. These objects (Gliese numbers 256, 425A, 900, and 907.1) are shown to be 'marginal' BY Dra stars, single objects of age 2.5-3 Gyr with activity and rotational velocity (3-5 km/s) between those of normal dM stars and those of true BY Dra stars. An explanation based on evolution from the BY Dra stage through marginal BY Dra to inactive dM is proposed.

Magnetism in icosahedral quasicrystals: current status and open questions

DOE PAGES

Goldman, Alan I.

2014-07-02

Progress in our understanding of the magnetic properties of R-containing icosahedral quasicrystals (R = rare earth element) from over 20 years of experimental effort is reviewed. This includes the much studied R-Mg-Zn and R-Mg-Cd ternary systems, as well as several magnetic quasicrystals that have been discovered and investigated more recently including Sc-Fe-Zn, R-Ag-In, Yb-Au-Al, the recently synthesized R-Cd binary quasicrystals, and their periodic approximants. In many ways, the magnetic properties among these quasicrystals are very similar. However, differences are observed that suggest new experiments and promising directions for future research.

Rhodium/Silver-Cocatalyzed Transannulation of N-Sulfonyl-1,2,3-triazoles with Vinyl Azides: Divergent Synthesis of Pyrroles and 2 H-Pyrazines.

PubMed

Zhang, Lin; Sun, Ge; Bi, Xihe

2016-11-07

The first cyclization reaction between vinyl azides and N-sulfonyl-1,2,3-triazoles is reported. A Rh/Ag binary metal catalyst system proved to be necessary for the successful cyclization. By varying the structure of vinyl azides, such reaction allows the divergent synthesis of pyrroles and 2H-pyrazines. The cyclization reactions feature a broad substrate scope, good functional group tolerance, high reaction efficiency, and good to high product yields. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optical and semiconductive properties of binary and ternary thin films from the Nb-Ti-O system

NASA Astrophysics Data System (ADS)

Aperador, W.; Yate, L.; Pinzón, M. J.; Caicedo, J. C.

2018-06-01

A study has been conducted based on the Mott-Schottky model acquisition by potentiodynamic electrochemical impedance spectroscopy, to determine the physical-chemical properties of binary TiO2, Nb2O5 and ternary Nb-Ti-O thin films (semiconductor type) based on Nb,Ti, O elements. The technique used for the study of optical properties was that of spectral transmittance, measurements were performed using a spectrophotometer. The consistency of the impedance data has been studied by calculating the Kramers-Kronig relations. The structural properties were analyzed by XRD patterns; the chemical composition measurements for all thin films were made by using XPS technique. So, in this research the transmittance values change from 72.74% for Nb2O5 to 59.68% for Ti-Nb-O with wavelength around 355 nm. The absorption coefficients for all films were analyzed from 31823.87 cm-1 for Nb2O5 to 91240.90 cm-1 for Nb-Ti-O with wavelength around 355 nm evidencing thus a 65% reduction. The direct band gap it was found that the photon energy (band gap Eg) changes in all films from 3.56 eV for Nb2O5 to 3.96 eV for Ti-Nb-O evidencing a 10% reduction. The extinction coefficient values change in all films from 0.038 cm-1 for Nb2O5 to 0.277 cm-1 for Ti-Nb-O films with wavelength around 355 nm, exhibiting an 86% increasing. Finally, it was observed by the Mott-Schottky analysis that the reference potential (Ag/AgCl) changes for all films from -2.09 V for Nb2O5 to -0.80 V for Ti-Nb-O material showing a 62% reduction.

Structure of dental gallium alloys.

PubMed

Herø, H; Simensen, C J; Jørgensen, R B

1996-07-01

The interest in gallium alloys as a replacement for amalgam has increased in recent years due to the risk of environmental pollution from amalgam. Alloy powders with compositions close to those for alloys of amalgam are mixed with a liquid gallium alloy. The mix is condensed into a prepared cavity in much the same way as for amalgam. The aim of the present work was to study the structure of: (1) two commercial alloy powders containing mainly silver, tin and copper, and (2) the phases formed by mixing these powders with a liquid alloy of gallium, indium and tin. One of the alloy powders contained 9 wt% palladium. Cross-sections of cylindrical specimens made by these gallium mixes were investigated by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Discrete grains of the following phases were found to be present in both gallium alloys: hexagonal Ag2Ga, tetragonal Cu(Pd)Ga2, cubic Ag9In4 and tetragonal beta-Sn. Indications of hexagonal or orthorhombic Ag2Sn were found in the remaining, unreacted alloy particles. In the palladium-containing alloy the X-ray reflections indicate a minor fraction of cubic Cu9Ga4 in addition to the Cu(Pd)Ga2 phase. Particles of beta-Sn are probably precipitated because Sn-Ga phases cannot be formed according to the binary phase diagram.

DNA-mediated gold nanoparticle signal transducers for combinatorial logic operations and heavy metal ions sensing.

PubMed

Zhang, Yuhuan; Liu, Wei; Zhang, Wentao; Yu, Shaoxuan; Yue, Xiaoyue; Zhu, Wenxin; Zhang, Daohong; Wang, Yanru; Wang, Jianlong

2015-10-15

Herein, the structure of two DNA strands which are complementary except fourteen T-T and C-C mismatches was programmed for the design of the combinatorial logic operation by utilizing the different protective capacities of single chain DNA, part-hybridized DNA and completed-hybridized DNA on unmodified gold nanoparticles. In the presence of either Hg(2+) or Ag(+), the T-Hg(2+)-T or C-Ag(+)-C coordination chemistry could lead to the formation of part-hybridized DNA which keeps gold nanoparticles from clumping after the addition of 40 μL 0.2M NaClO4 solution, but the protection would be screened by 120 μL 0.2M NaClO4 solution. While the coexistence of Hg(2+), Ag(+) caused the formation of completed-hybridized DNA and the protection for gold nanoparticles lost in either 40 μL or 120 μL NaClO4 solutions. Benefiting from sharing of the same inputs of Hg(2+) and Ag(+), OR and AND logic gates were easily integrated into a simple colorimetric combinatorial logic operation in one system, which make it possible to execute logic gates in parallel to mimic arithmetic calculations on a binary digit. Furthermore, two other logic gates including INHIBIT1 and INHIBIT2 were realized to integrated with OR logic gate both for simultaneous qualitative discrimination and quantitative determination of Hg(2+) and Ag(+). Results indicate that the developed logic system based on the different protective capacities of DNA structure on gold nanoparticles provides a new pathway for the design of the combinatorial logic operation in one system and presents a useful strategy for development of advanced sensors, which may have potential applications in multiplex chemical analysis and molecular-scale computer design. Copyright © 2015 Elsevier B.V. All rights reserved.

Optimisation of cosolvent concentration for topical drug delivery III--influence of lipophilic vehicles on ibuprofen permeation.

PubMed

Watkinson, R M; Guy, R H; Oliveira, G; Hadgraft, J; Lane, M E

2011-01-01

Previously, we have reported the effects of water, ethanol, propylene glycol and various binary and ternary mixtures of these solvents on the permeation of ibuprofen in model membranes and in skin. The present study investigates the influence of lipophilic vehicles on the transport of ibuprofen in silicone membrane and in human skin. The permeation of ibuprofen was measured from mineral oil (MO), Miglyol® 812 (MG) and binary mixtures of MO and MG. The solubility of ibuprofen was 5-fold higher in MG than in MO, however, the permeation of ibuprofen from the pure vehicles and combinations of both was comparable in silicone membrane. Additionally, there were no significant differences in skin permeation for MO and MG vehicles. When the permeation of various hydrophilic and lipophilic vehicles is considered, a trend between flux values for the model membrane and skin is evident (r(2) = 0.71). The findings suggest that silicone membrane may provide information on qualitative trends in skin permeation for vehicles of diverse solubility and partition characteristics. Copyright © 2010 S. Karger AG, Basel.

On the effect of stress on nucleation and growth of precipitates in an Al-Cu-Mg-Ag alloy

NASA Astrophysics Data System (ADS)

Skrotzki, B.; Shiflet, G. J.; Starke, E. A.

1996-11-01

A study has been made of the effect of an externally applied tensile stress on Ω and Θ' precipitate nucleation and growth in an Al-Cu-Mg-Ag alloy and a binary Al-Cu alloy which was used as a model system. Both solutionized and solutionized and aged conditions were studied. The mechanical properties have been measured and the microstructures have been characterized by transmission electron microscopy (TEM). The volume fraction and number density, as well as the precipitate size, have been experimentally determined. It was found that for as-solutionized samples aged under stress, precipitation occurs preferentially parallel to the stress axis. A threshold stress has to be exceeded before this effect can be observed. The critical stress for influencing the precipitate habit plane is between 120 and 140 MPa for Ω and between 16 and 19 MPa for Θ' for the aging temperature of 160 °C. The major effect of the applied stress is on the nucleation process. The results are discussed in terms of the role of the lattice misfit between the matrix and the precipitate nucleus.

ZnO nanorod array/CuAlO2 nanofiber heterojunction on Ni substrate: synthesis and photoelectrochemical properties.

PubMed

Ding, Juan; Sui, Yongming; Fu, Wuyou; Yang, Haibin; Zhao, Bo; Li, Minghui

2011-07-22

A novel ZnO nanorod array (NR)/CuAlO(2) nanofiber (NF) heterojunction nanostructure was grown on a substrate of Ni plates using sol-gel synthesis for the NFs and hydrothermal reaction for the NRs. Compared with a traditional ZnO/CuAlO(2) laminar film nanostructure, the photocurrent of this fibrous network heterojunction is significantly increased. A significant blue-shift of the absorption edge and a favorable forward current to reverse current ratio at applied voltages of -2 to +2 V were observed in this heterojunction with the increase of Zn(2+) ion concentration in the hydrothermal reaction. Furthermore, the photoelectrochemical properties were investigated and the highest photocurrent of 3.1 mA cm(-2) was obtained under AM 1.5 illumination with 100 mW cm(-2) light intensity at 0.71 V (versus Ag/AgCl). This novel 3D fibrous network nanostructure plays an important role in the optoelectronic field and can be extended to other binary or ternary oxide compositions for various applications.

ZnO nanorod array/CuAlO2 nanofiber heterojunction on Ni substrate: synthesis and photoelectrochemical properties

NASA Astrophysics Data System (ADS)

Ding, Juan; Sui, Yongming; Fu, Wuyou; Yang, Haibin; Zhao, Bo; Li, Minghui

2011-07-01

A novel ZnO nanorod array (NR)/CuAlO2 nanofiber (NF) heterojunction nanostructure was grown on a substrate of Ni plates using sol-gel synthesis for the NFs and hydrothermal reaction for the NRs. Compared with a traditional ZnO/CuAlO2 laminar film nanostructure, the photocurrent of this fibrous network heterojunction is significantly increased. A significant blue-shift of the absorption edge and a favorable forward current to reverse current ratio at applied voltages of - 2 to + 2 V were observed in this heterojunction with the increase of Zn2 + ion concentration in the hydrothermal reaction. Furthermore, the photoelectrochemical properties were investigated and the highest photocurrent of 3.1 mA cm - 2 was obtained under AM 1.5 illumination with 100 mW cm - 2 light intensity at 0.71 V (versus Ag/AgCl). This novel 3D fibrous network nanostructure plays an important role in the optoelectronic field and can be extended to other binary or ternary oxide compositions for various applications.

A new interferometric study of four exoplanet host stars: θ Cygni, 14 Andromedae, υ Andromedae and 42 Draconis

NASA Astrophysics Data System (ADS)

Ligi, R.; Mourard, D.; Lagrange, A. M.; Perraut, K.; Boyajian, T.; Bério, Ph.; Nardetto, N.; Tallon-Bosc, I.; McAlister, H.; ten Brummelaar, T.; Ridgway, S.; Sturmann, J.; Sturmann, L.; Turner, N.; Farrington, C.; Goldfinger, P. J.

2012-09-01

Context. Since the discovery of the first exoplanet in 1995 around a solar-type star, the interest in exoplanetary systems has kept increasing. Studying exoplanet host stars is of the utmost importance to establish the link between the presence of exoplanets around various types of stars and to understand the respective evolution of stars and exoplanets. Aims: Using the limb-darkened diameter (LDD) obtained from interferometric data, we determine the fundamental parameters of four exoplanet host stars. We are particularly interested in the F4 main-sequence star, θ Cyg, for which Kepler has recently revealed solar-like oscillations that are unexpected for this type of star. Furthermore, recent photometric and spectroscopic measurements with SOPHIE and ELODIE (OHP) show evidence of a quasi-periodic radial velocity of ~150 days. Models of this periodic change in radial velocity predict either a complex planetary system orbiting the star, or a new and unidentified stellar pulsation mode. Methods: We performed interferometric observations of θ Cyg, 14 Andromedae, υ Andromedae and 42 Draconis for two years with VEGA/CHARA (Mount Wilson, California) in several three-telescope configurations. We measured accurate limb darkened diameters and derived their radius, mass and temperature using empirical laws. Results: We obtain new accurate fundamental parameters for stars 14 And, υ And and 42 Dra. We also obtained limb darkened diameters with a minimum precision of ~1.3%, leading to minimum planet masses of Msini = 5.33 ± 0.57, 0.62 ± 0.09 and 3.79 ± 0.29 MJup for 14 And b, υ And b and 42 Dra b, respectively. The interferometric measurements of θ Cyg show a significant diameter variability that remains unexplained up to now. We propose that the presence of these discrepancies in the interferometric data is caused either by an intrinsic variation of the star or an unknown close companion orbiting around it. Based on interferometric observations with the VEGA/CHARA instrument.Appendix A is available in electronic form at http://www.aanda.org

Influence of complex impurity centres on radiation damage in wide-gap metal oxides

NASA Astrophysics Data System (ADS)

Lushchik, A.; Lushchik, Ch.; Popov, A. I.; Schwartz, K.; Shablonin, E.; Vasil'chenko, E.

2016-05-01

Different mechanisms of radiation damage of wide-gap metal oxides as well as a dual influence of impurity ions on the efficiency of radiation damage have been considered on the example of binary ionic MgO and complex ionic-covalent Lu3Al5O12 single crystals. Particular emphasis has been placed on irradiation with ∼2 GeV heavy ions (197Au, 209Bi, 238U, fluence of 1012 ions/cm2) providing extremely high density of electronic excitations within ion tracks. Besides knock-out mechanism for Frenkel pair formation, the additional mechanism through the collapse of mobile discrete breathers at certain lattice places (e.g., complex impurity centres) leads to the creation of complex defects that involve a large number of host atoms. The experimental manifestations of the radiation creation of intrinsic and impurity antisite defects (Lu|Al or Ce|Al - a heavy ion in a wrong cation site) have been detected in LuAG and LuAG:Ce3+ single crystals. Light doping of LuAG causes a small enhancement of radiation resistance, while pair impurity centres (for instance, Ce|Lu-Ce|Al or Cr3+-Cr3+ in MgO) are formed with a rise of impurity concentration. These complex impurity centres as well as radiation-induced intrinsic antisite defects (Lu|Al strongly interacting with Lu in a regular site) tentatively serve as the places for breathers collapse, thus decreasing the material resistance against dense irradiation.

A spectrophotometric method for detecting substellar companions to late-type M stars

NASA Astrophysics Data System (ADS)

Oetiker, Brian Glen

The most common stars in the Galaxy are the main-sequence M stars, yet current techniques are not optimized for detecting companions around the lowest mass stars; those with spectral designations ranging from M6 to M10. Described in this study is a search for companions around such stars using two methods: a unique implementation of the transit method, and a newly designed differential spectrophotometric method. The TEP project focusses on the detection of transits of terrestrial sized and larger companions in the eclipsing binary system CM Draconis. The newly designed spectrophotometric technique combines the strengths of the spectroscopic and photometric methods, while minimizing their inherent weaknesses. This unique method relies on the placement of three narrow band optical filters on and around the Titanium Oxide (TiO) bandhead near 8420 Å, a feature commonly seen in the atmospheres of late M stars. One filter is placed on the slope of the bandhead feature, while the remaining two are located on the adjacent continuum portions of the star's spectrum. The companion-induced motion of the star results in a doppler shifting of the bandhead feature, which in turn causes a change in flux passing through the filter located on the slope of the TiO bandhead. The spectrophotometric method is optimized for detecting compact systems containing brown dwarfs and giant planets. Because of its low dispersion-high photon efficiency design, this method is well suited for surveying large numbers of faint M stars. A small scale survey has been implemented, producing a candidate brown dwarf class companion of the star WX UMa. Applying the spectrophotometric method to a larger scale survey for brown dwarf and giant planet companions, coupled with a photometric transit study addresses two key astronomical issues. By detecting or placing limits on compact late type M star systems, a discrimination among competing theories of planetary formation may be gained. Furthermore, searching for a broad range of companion masses, may result in a better understanding of the substellar mass function.

Hot Accretion Spots and Nitrogen Enhancement in Algol-Type Interacting Binary Systems

NASA Astrophysics Data System (ADS)

Peters, Geraldine J.

2013-07-01

The shock from the impact of a gas stream onto the photosphere of a mass gainer in an Algol system is expected to produce a hot spot and also heat circumstellar material that is splashed from the impact site. Furthermore in some cases we expect the stripped-down mass loser (a late-type subgiant) to be nitrogen rich and carbon poor if CNO-processed material is currently being transferred. I will present observational evidence from the Kepler and FUSE spacecrafts for the presence of hot spots and discuss their behavior. FUSE observations of Algols that convincingly show that the gas stream material from some Algol secondaries is N-enhanced and virtually devoid of carbon is also presented. From Kepler data we have identified a long-term phenomenon in which the relative brightness of the quadrature light varies by a few percent and numerically reverses over a time scale of about a 100-400 days. We call the systems T/L (trailing hemisphere/leading hemisphere) variables. Such behavior has never been identified from ground-based photometry. WX Draconis (A8 + K0 IV, P = 1.80 d), a system whose primary displays delta Scuti-like pulsations, is the prototype. The Kepler light curves are being modeled with the latest version of the Wilson-Devinney program that includes the capability of treating migrating hot/cool spots. I will discuss whether the T/L behavior is likely due to a migrating hot accretion spot on the primary or variability in a large cool-spotted area on the secondary. From archival FUSE data we have confirmed the presence of a hot accretion spot in the Algol system U Cephei and present information on the spot parameters/behavior and conditions in a splash plasma from the impact site. Kepler and archival FUSE observations continue to provide important information on the nature of the component stars in Algol systems and the detailed physics of mass transfer, especially the role of accretion hot spots. We are grateful for support from NASA grants NNX11AC78G and NNX12AE44G.

Investigation of the wett-ability of various pure metals and alloys and beryllium

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

Gilliland, Ralph Gerald

1963-06-13

Thesis submitted to University of Tennessee, Knoxville. Activities in a program to determine the wetting behavior of pure metals such as Au, Ag, Ge, Al, and Cu on solid Be are reported. Results of similar investigations of binary alloys such as Be--Ti, Be-Zr, and Be--Pd are also included. The contact angles of the molten metals on Be as a function of temperature, exposure time, and atmosphere were measured. The solid-liquid interfacial reactions occurring as a function of test temperature and atmosphere were investigated, and the liquid- vapor and internal surface tensions for those systems in which interfacial reactions did notmore » appear to occur were calculated.« less

Calculation of Gallium-metal-Arsenic phase diagrams

NASA Technical Reports Server (NTRS)

Scofield, J. D.; Davison, J. E.; Ray, A. E.; Smith, S. R.

1991-01-01

Electrical contacts and metallization to GaAs solar cells must survive at high temperatures for several minutes under specific mission scenarios. The determination of which metallizations or alloy systems that are able to withstand extreme thermal excursions with minimum degradation to solar cell performance can be predicted by properly calculated temperature constitution phase diagrams. A method for calculating a ternary diagram and its three constituent binary phase diagrams is briefly outlined and ternary phase diagrams for three Ga-As-X alloy systems are presented. Free energy functions of the liquid and solid phase are approximated by the regular solution theory. Phase diagrams calculated using this method are presented for the Ga-As-Ge and Ga-As-Ag systems.

Nitride Conversion: A Novel Approach to c-Si Solar Cell Metallization

NASA Astrophysics Data System (ADS)

Hook, David Henry

Metallization of commercial-grade c-Si solar cells is currently accomplished by screen-printing fine lines of a Ag/PbO-glass paste amalgam (Ag-frit) onto the insulating SiNx antireflective coating (ARC) that lies atop the shallow n-type emitter layer of the cell. Upon annealing, the glass etches SiNx and permits the crystallization of Ag near the electrically-active emitter interface, thus contacting the cell. While entirely functional, the contact interface produced by Ag-frit metallization is non-ideal, and Ag metal itself is expensive; its use adds to overall solar cell costs. The following work explores the use of Ti-containing alloys as metallization media for c-Si solar cells. There is a -176 kJ [mol N]--1 free energy change associated with the conversion of Si3N4 to TiN. By combining Ti with a low-melting point metal, this reaction can take place at temperatures as low as 750°C in the bulk. Combinations of Ti with Cu, Sn, Ag, and Pb ternary and binary systems are investigated. On unmetallized, c-Si textured solar cells it is shown that 900 nm of stoichiometric Ti6Sn 5 is capable of converting the SiNx ARC to TiN and Ti5Si3, both of which are conducting materials with electrically low-barriers to contact with n-type Si. Alongside electron microscopy, specific contact resistivity (rho c) measurements are used to determine the interfacial quality of TiN/Ti5Si3 contacts to n-Si. Circular transmission line model (CTLM) measurements are utilized for the characterization of reacted Ag0.05Cu0.69Ti0.26, Sn0.35 Ag0.27Ti0.38, and Ti6Sn5 contacts. rhoc values as low as 26 muOcm 2 are measured for reacted Ti6Sn5-SiN x on conventional c-Si solar cells. This value is approximately 2-3 orders of magnitude lower than rhoc of contacts produced by traditional Ag-frit metallization. Viable 1x1 cm, Ti6Sn5-metallized solar cells on 5x5 cm substrates were fabricated through a collaboration with the Georgia Institute of Technology (GA Tech). Front-side metallization was performed at NCSU; cells were then shipped to GA Tech for rear-side metallization, Ag-plating to increase the metal thickness, and cell isolation. This collaboration produced a 16.9% efficient, Ti6Sn5-metallized cell compared to a 17.4% efficient Ag frit-metallized control cell that had experienced an identical temperature profile. It was found that the annealing profiles associated with conversion-metallization promote H2 desorption from the SiN x ARC and thus negatively affect cell passivation. Strategies exist for decreasing the heat experienced by conversion-metallized cells, doing so would increase the overall efficiency and improve other relevant metrics. Solar industry analysis indicates that c-Si cells will increase in efficiency by switching to high sheet-resistance p-type emitters; there will be a marked need for a contact mechanism with a near-ideal, low barrier-height interfaces to these next-generation layers. SiN x ARC conversion to TiN/Ti5Si3 represents an economical means of achieving low rhoc contact to both n and p-type Si when compared to metallization by Ag frit.

Metal thin film growth on multimetallic surfaces: From quaternary metallic glass to binary crystal

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

Jing, Dapeng

2010-01-01

The work presented in this thesis mainly focuses on the nucleation and growth of metal thin films on multimetallic surfaces. First, we have investigated the Ag film growth on a bulk metallic glass surface. Next, we have examined the coarsening and decay of bilayer Ag islands on NiAl(110) surface. Third, we have investigated the Ag film growth on NiAl(110) surface using low-energy electron diffraction (LEED). At last, we have reported our investigation on the epitaxial growth of Ni on NiAl(110) surface. Some general conclusions can be drawn as follows. First, Ag, a bulk-crystalline material, initially forms a disordered wetting layermore » up to 4-5 monolayers on Zr-Ni-Cu-Al metallic glass. Above this coverage, crystalline 3D clusters grow, in parallel with the flatter regions. The cluster density increases with decreasing temperature, indicating that the conditions of island nucleation are far-from-equilibrium. Within a simple model where clusters nucleate whenever two mobile Ag adatoms meet, the temperature-dependence of cluster density yields a (reasonable) upper limit for the value of the Ag diffusion barrier on top of the Ag wetting layer of 0.32 eV. Overall, this prototypical study suggests that it is possible to grow films of a bulk-crystalline metal that adopt the amorphous character of a glassy metal substrate, if film thickness is sufficiently low. Next, the first study of coarsening and decay of bilayer islands has been presented. The system was Ag on NiAl(110) in the temperature range from 185 K to 250 K. The coarsening behavior, has some similarities to that seen in the Ag(110) homoepitaxial system studied by Morgenstern and co-workers. At 185 K and 205 K, coarsening of Ag islands follows a Smoluchowski ripening pathway. At 205 K and 250 K, the terrace diffusion limited Ostwald ripening dominants. The experimental observed temperature for the transition from SR to OR is 205 K. The SR exhibits anisotropic island diffusion and the OR exhibits 1D decay of island length while keeping the corresponding island width constant. Third, LEED indicates that, up to about 6 BL (12 ML), the Ag film adopts the (110) structure on lattice matched NiAl(110) surface, supporting the previous assignment based upon island heights measured in STM. Starting at 4.5 to 6 BL, (111) diffraction pattern is detected. This is also in agreement with previous STM study. Careful examinations of the LEED patterns reveal the slight difference in lattice constants between bulk Ag and bulk NiAl. At last, we performed STM studies of Ni deposition on NiAl(110) in the temperature range from 200 K to 400 K. Ni forms 'dense' Ni(100)-like islands on NiAl(110) with a zig-zag shaped stripe feature which is probably due to strain relief. DFT analysis provides insights into the island growth shapes, which are rationalized by the thermodynamics and kinetics of the film growth process. For thick Ni films (coverage exceeding 6 ML), a Ni(111)-like structure developed. Traditional MF theory is applied to analyze island density at 200 K. Deviation from homogeneous nucleation behavior for island size distribution and island density reveals the presence of heterogeneous nucleation mediated by the Ni antisite point defects on NiAl(110) surface.« less

Phase equilibria in the quasiternary system Ag{sub 2}S–Ga{sub 2}S{sub 3}–In{sub 2}S{sub 3} and optical properties of (Ga{sub 55}In{sub 45}){sub 2}S{sub 300}, (Ga{sub 54.59}In{sub 44.66}Er{sub 0.75}){sub 2}S{sub 300} single crystals

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

Ivashchenko, I.A., E-mail: Ivashchenko.Inna@eenu.edu.ua; Danyliuk, I.V.; Olekseyuk, I.D.

The quasiternary system Ag{sub 2}S–Ga{sub 2}S{sub 3}–In{sub 2}S{sub 3} was investigated by differential thermal, X-ray diffraction analyses. The phase diagram of the Ga{sub 2}S{sub 3}–In{sub 2}S{sub 3} system and nine polythermal sections, isothermal section at 820 K and the liquidus surface projection were constructed. The existence of the large solid solutions ranges of binary and ternary compounds was established. The range of the existence of the quaternary phase AgGa{sub x}In{sub 5−x}S{sub 8} (2.25≤x≤2.85) at 820 K was determined. The single crystals (Ga{sub 55}In{sub 45}){sub 2}S{sub 300} and (Ga{sub 54.59}In{sub 44.66}Er{sub 0.75}){sub 2}S{sub 300} were grown by a directional crystallization methodmore » from solution-melt. Optical absorption spectra in the 500–1600 nm range were recorded. The luminescence of the (Ga{sub 54.59}In{sub 44.66}Er{sub 0.75}){sub 2}S{sub 300} single crystal shows a maximum at 1530 nm for the excitation wavelengths of 532 and 980 nm at 80 and 300 K. - Graphical abstract: Isothermal section of the quasiternary system Ag{sub 2}S–Ga{sub 2}S{sub 3}–In{sub 2}S{sub 3} at 820 K and normalized photoluminescence spectra of the single crystal (Ga{sub 54.59}In{sub 44.66}Er{sub 0.75}){sub 2}S{sub 300} at 300 K. - Highlights: • Isothermal section at 820 K, liquidus surface projection were built for Ag{sub 2}S–Ga{sub 2}S{sub 3}–In{sub 2}S{sub 3}. • Optical properties of single crystals were studied.« less

Theoretical study of the noble metals on semiconductor surfaces and Ti-base shape memory alloys

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

Ding, Yungui

1994-07-27

The electronic and structural properties of the (√3 x√3) R30° Ag/Si(111) and (√3 x √3) R30° Au/Si(111) surfaces are investigated using first principles total energy calculations. We have tested almost all experimentally proposed structural models for both surfaces and found the energetically most favorable model for each of them. The lowest energy model structure of the (√3 x √3) R30° Ag/Si(111) surface consists of a top layer of Ag atoms arranged as ``honeycomb-chained-trimers`` lying above a distorted ``missing top layer`` Si(111) substrate. The coverage of Ag is 1 monolayer (ML). We find that the honeycomb structure observed in STM imagesmore » arise from the electronic charge densities of an empty surface band near the Fermi level. The electronic density of states of this model gives a ``pseudo-gap`` around the Fermi level, which is consistent with experimental results. The lowest energy model for the (√3 x √3) R30° Au/Si(111) surface is a conjugate honeycomb-chained-trimer (CHCT-1) configuration which consists of a top layer of trimers formed by 1 ML Au atoms lying above a ``missing top layer`` Si(111) substrate with a honeycomb-chained-trimer structure for its first layer. The structures of Au and Ag are in fact quite similar and belong to the same class of structural models. However, small variation in the structural details gives rise to quite different observed STM images, as revealed in the theoretical calculations. The electronic charge density from bands around the Fermi level for the (√3 x √3) R30°, Au/Si(111) surface also gives a good description of the images observed in STM experiments. First principles calculations are performed to study the electronic and structural properties of a series of Ti-base binary alloys TiFe, TiNi, TiPd, TiMo, and TiAu in the B2 structure.« less

ALMA and GMRT Constraints on the Off-axis Gamma-Ray Burst 170817A from the Binary Neutron Star Merger GW170817

NASA Astrophysics Data System (ADS)

Kim, S.; Schulze, S.; Resmi, L.; González-López, J.; Higgins, A. B.; Ishwara-Chandra, C. H.; Bauer, F. E.; de Gregorio-Monsalvo, I.; De Pasquale, M.; de Ugarte Postigo, A.; Kann, D. A.; Martín, S.; Oates, S. R.; Starling, R. L. C.; Tanvir, N. R.; Buchner, J.; Campana, S.; Cano, Z.; Covino, S.; Fruchter, A. S.; Fynbo, J. P. U.; Hartmann, D. H.; Hjorth, J.; Jakobsson, P.; Levan, A. J.; Malesani, D.; Michałowski, M. J.; Milvang-Jensen, B.; Misra, K.; O’Brien, P. T.; Sánchez-Ramírez, R.; Thöne, C. C.; Watson, D. J.; Wiersema, K.

2017-12-01

Binary neutron-star mergers (BNSMs) are among the most readily detectable gravitational-wave (GW) sources with the Laser Interferometer Gravitational-wave Observatory (LIGO). They are also thought to produce short γ-ray bursts (SGRBs) and kilonovae that are powered by r-process nuclei. Detecting these phenomena simultaneously would provide an unprecedented view of the physics during and after the merger of two compact objects. Such a Rosetta Stone event was detected by LIGO/Virgo on 2017 August 17 at a distance of ∼44 Mpc. We monitored the position of the BNSM with Atacama Large Millimeter/submillimeter Array (ALMA) at 338.5 GHz and the Giant Metrewave Radio Telescope (GMRT) at 1.4 GHz, from 1.4 to 44 days after the merger. Our observations rule out any afterglow more luminous than 3× {10}26 {erg} {{{s}}}-1 {{Hz}}-1 in these bands, probing >2–4 dex fainter than previous SGRB limits. We match these limits, in conjunction with public data announcing the appearance of X-ray and radio emission in the weeks after the GW event, to templates of off-axis afterglows. Our broadband modeling suggests that GW170817 was accompanied by an SGRB and that the γ-ray burst (GRB) jet, powered by {E}{AG,{iso}}∼ {10}50 erg, had a half-opening angle of ∼ 20^\\circ , and was misaligned by ∼ 41^\\circ from our line of sight. The data are also consistent with a more collimated jet: {E}{AG,{iso}}∼ {10}51 erg, {θ }1/2,{jet}∼ 5^\\circ ,{θ }{obs}∼ 17^\\circ . This is the most conclusive detection of an off-axis GRB afterglow and the first associated with a BNSM-GW event to date. We use the viewing angle estimates to infer the initial bulk Lorentz factor and true energy release of the burst.

Liquidus slopes of impurities in ITS-90 fixed points from the mercury point to the copper point in the low concentration limit

NASA Astrophysics Data System (ADS)

Pearce, Jonathan V.; Gisby, John A.; Steur, Peter P. M.

2016-08-01

A knowledge of the effect of impurities at the level of parts per million on the freezing temperature of very pure metals is essential for realisation of ITS-90 fixed points. New information has become available for use with the thermodynamic modelling software MTDATA, permitting calculation of liquidus slopes, in the low concentration limit, of a wider range of binary alloy systems than was previously possible. In total, calculated values for 536 binary systems are given. In addition, new experimental determinations of phase diagrams, in the low impurity concentration limit, have recently appeared. All available data have been combined to provide a comprehensive set of liquidus slopes for impurities in ITS-90 metal fixed points. In total, liquidus slopes for 838 systems are tabulated for the fixed points Hg, Ga, In, Sn, Zn, Al, Ag, Au, and Cu. It is shown that the value of the liquidus slope as a function of impurity element atomic number can be approximated using a simple formula, and good qualitative agreement with the existing data is observed for the fixed points Al, Ag, Au and Cu, but curiously the formula is not applicable to the fixed points Hg, Ga, In, Sn, and Zn. Some discussion is made concerning the influence of oxygen on the liquidus slopes, and some calculations using MTDATA are discussed. The BIPM’s consultative committee for thermometry has long recognised that the sum of individual estimates method is the ideal approach for assessing uncertainties due to impurities, but the community has been largely powerless to use the model due to lack of data. Here, not only is data provided, but a simple model is given to enable known thermophysical data to be used directly to estimate impurity effects for a large fraction of the ITS-90 fixed points.

Atomistic modeling of grain boundary behavior under shear conditions in magnesium and magnesium-based binary alloys

NASA Astrophysics Data System (ADS)

Nahhas, M. K.; Groh, S.

2018-02-01

In this study, the structure, the energetic, and the strength of a { 10 1 bar 1 } < 11 2 bar 0 > symmetric tilt grain boundary in magnesium and magnesium binary alloys were analyzed in the framework of (semi-)empirical potentials. Following a systematic investigation of the transferability and accuracy of the interatomic potentials, atomistic calculations of the grain boundary energy, the grain boundary sliding energy, and the grain boundary strength were performed in pure magnesium and in binary MgX alloys (X = Al, Ca, Gd, Li, Sn, Y, Ag, Nd, and Pb). The data gained in this study were analyzed to identify the most critical material parameters controlling the strength of the grain boundary, and their consequence on atomic shuffling motions occurring at the grain boundary. From the methodology perspective, the role of in-plane and out-of plane relaxation on the grain boundary sliding energy curves was investigated. In pure magnesium, the results showed that in-plane relaxation is critical in activating b2{ 10 1 bar 1 } twinning dislocation resulting in grain boundary migration. In the alloy systems, however, grain boundary migration was disabled as a consequence of the pinning of the grain boundary by segregated elements. Finally, while the grain boundary energy, the shape of the grain boundary sliding energy curves, and the grain boundary sliding energy are critical parameters controlling the grain boundary strength in pure magnesium, only the grain boundary energy and the segregation energy of the alloying elements at the grain boundary were identified as critical material parameters in the alloys system.

Line identifications in the ultraviolet spectra of Tau Herculis, B5 IV, and Zeta Draconis, B6 III

NASA Technical Reports Server (NTRS)

Underhill, A. B.; Adelman, S. J.

1976-01-01

Tables of the lines found on two tracings each of the ultraviolet spectrum of Tau Her, B5 IV, and Zeta Dra, B6 III, made by the Copernicus satellite and possible identifications are given. The ranges 1025-1451A for Tau Her and 1035 to 1425A for Zeta Dra are covered by the U2 spectrometer at a resolution of 0.2A; the ranges 2028 to 2959A for Tau Her and 2000 to 3000A for Zeta Dra are covered by the V2 spectrometer at a resolution of 0.4A. The observed density of lines in the U2 region is 1.1 lines/A for Tau Her and 1.7 lines/A for Zeta Dra. In the V2 region it is 0.8 lines/A for Tau Her and 0.9 lines/A for Zeta Dra.

Extension of the Peters–Belson method to estimate health disparities among multiple groups using logistic regression with survey data

PubMed Central

Li, Y.; Graubard, B. I.; Huang, P.; Gastwirth, J. L.

2015-01-01

Determining the extent of a disparity, if any, between groups of people, for example, race or gender, is of interest in many fields, including public health for medical treatment and prevention of disease. An observed difference in the mean outcome between an advantaged group (AG) and disadvantaged group (DG) can be due to differences in the distribution of relevant covariates. The Peters–Belson (PB) method fits a regression model with covariates to the AG to predict, for each DG member, their outcome measure as if they had been from the AG. The difference between the mean predicted and the mean observed outcomes of DG members is the (unexplained) disparity of interest. We focus on applying the PB method to estimate the disparity based on binary/multinomial/proportional odds logistic regression models using data collected from complex surveys with more than one DG. Estimators of the unexplained disparity, an analytic variance–covariance estimator that is based on the Taylor linearization variance–covariance estimation method, as well as a Wald test for testing a joint null hypothesis of zero for unexplained disparities between two or more minority groups and a majority group, are provided. Simulation studies with data selected from simple random sampling and cluster sampling, as well as the analyses of disparity in body mass index in the National Health and Nutrition Examination Survey 1999–2004, are conducted. Empirical results indicate that the Taylor linearization variance–covariance estimation is accurate and that the proposed Wald test maintains the nominal level. PMID:25382235

Charging of insulators by multiply-charged-ion impact probed by slowing down of fast binary-encounter electrons

NASA Astrophysics Data System (ADS)

de Filippo, E.; Lanzanó, G.; Amorini, F.; Cardella, G.; Geraci, E.; Grassi, L.; La Guidara, E.; Lombardo, I.; Politi, G.; Rizzo, F.; Russotto, P.; Volant, C.; Hagmann, S.; Rothard, H.

2010-12-01

The interaction of ion beams with insulators leads to charging-up phenomena, which at present are under investigation in connection with guiding phenomena in nanocapillaries with possible application in nanofocused beams. We studied the charging dynamics of insulating foil targets [Mylar, polypropylene (PP)] irradiated with swift ion beams (C, O, Ag, and Xe at 40, 23, 40, and 30 MeV/u, respectively) via the measurement of the slowing down of fast binary-encounter electrons. Also, sandwich targets (Mylar covered with a thin Au layer on both surfaces) and Mylar with Au on only one surface were used. Fast-electron spectra were measured by the time-of-flight method at the superconducting cyclotron of Laboratori Nazionali del Sud (LNS) Catania. The charge buildup leads to target-material-dependent potentials of the order of 6.0 kV for Mylar and 2.8 kV for PP. The sandwich targets, surprisingly, show the same behavior as the insulating targets, whereas a single Au layer on the electron and ion exit side strongly suppresses the charging phenomenon. The accumulated number of projectiles needed for charging up is inversely proportional to electronic energy loss. Thus, the charging up is directly related to emission of secondary electrons.

Defining an additivity framework for mixture research in inducible whole-cell biosensors

NASA Astrophysics Data System (ADS)

Martin-Betancor, K.; Ritz, C.; Fernández-Piñas, F.; Leganés, F.; Rodea-Palomares, I.

2015-11-01

A novel additivity framework for mixture effect modelling in the context of whole cell inducible biosensors has been mathematically developed and implemented in R. The proposed method is a multivariate extension of the effective dose (EDp) concept. Specifically, the extension accounts for differential maximal effects among analytes and response inhibition beyond the maximum permissive concentrations. This allows a multivariate extension of Loewe additivity, enabling direct application in a biphasic dose-response framework. The proposed additivity definition was validated, and its applicability illustrated by studying the response of the cyanobacterial biosensor Synechococcus elongatus PCC 7942 pBG2120 to binary mixtures of Zn, Cu, Cd, Ag, Co and Hg. The novel method allowed by the first time to model complete dose-response profiles of an inducible whole cell biosensor to mixtures. In addition, the approach also allowed identification and quantification of departures from additivity (interactions) among analytes. The biosensor was found to respond in a near additive way to heavy metal mixtures except when Hg, Co and Ag were present, in which case strong interactions occurred. The method is a useful contribution for the whole cell biosensors discipline and related areas allowing to perform appropriate assessment of mixture effects in non-monotonic dose-response frameworks

Thermoelectric transport in Cu7PSe6 with high copper ionic mobility.

PubMed

Weldert, Kai S; Zeier, Wolfgang G; Day, Tristan W; Panthöfer, Martin; Snyder, G Jeffrey; Tremel, Wolfgang

2014-08-27

Building on the good thermoelectric performances of binary superionic compounds like Cu2Se, Ag2Se and Cu2S, a better and more detailed understanding of phonon-liquid electron-crystal (PLEC) thermoelectric materials is desirable. In this work we present the thermoelectric transport properties of the compound Cu7PSe6 as the first representative of the class of argyrodite-type ion conducting thermoelectrics. With a huge variety of possible compositions and high ionic conductivity even at room temperature, the argyrodites represent a very good model system to study structure-property relationships for PLEC thermoelectric materials. We particularly highlight the extraordinary low thermal conductivity of Cu7PSe6 below the glass limit, which can be associated with the molten copper sublattice leading to a softening of phonon modes.

Silver flip chip interconnect technology and solid state bonding

NASA Astrophysics Data System (ADS)

Sha, Chu-Hsuan

In this dissertation, fluxless transient liquid phase (TLP) bonding and solid state bonding between thermal expansion mismatch materials have been developed using Ag-In binary systems, pure Au, Ag, and Cu-Ag composite. In contrast to the conventional soldering process, fluxless bonding technique eliminates any corrosion and contamination problems caused by flux. Without flux, it is possible to fabricate high quality joints in large bonding areas where the flux is difficult to clean entirely. High quality joints are crucial to bonding thermal expansion mismatch materials since shear stress develops in the bonded pair. Stress concentration at voids in joints could increases breakage probability. In addition, intermetallic compound (IMC) formation between solder and underbump metallurgy (UBM) is essential for interconnect joint formation in conventional soldering process. However, the interface between IMC and solder is shown to be the weak interface that tends to break first during thermal cycling and drop tests. In our solid state bonding technique, there is no IMC involved in the bonding between Au to Au, Ag and Cu, and Ag and Au. All the reliability issues related to IMC or IMC growth is not our concern. To sum up, ductile bonding media, such as Ag or Au, and proper metallic layered structure are utilized in this research to produce high quality joints. The research starts with developing a low temperature fluxless bonding process using electroplated Ag/In/Ag multilayer structures between Si chip and 304 stainless steel (304SS) substrate. Because the outer thin Ag layer effectively protects inner In layer from oxidation, In layer dissolves Ag layer and joints to Ag layer on the to-be-bonded Si chip when temperature reaches the reflow temperature of 166ºC. Joints consist of mainly Ag-rich Ag-In solid solution and Ag2In. Using this fluxless bonding technique, two 304SS substrates can be bonded together as well. From the high magnification SEM images taken at cross-section, there is no void or gap observed. The new bonding technique presented should be valuable in packaging high power electronic devices for high temperature operations. It should also be useful to bond two 304SS parts together at low bonding temperature of 190ºC. Solid state bonding technique is then introduced to bond semiconductor chips, such as Si, to common substrates, such as Cu or alumina, using pure Ag and Au at a temperature matching the typical reflow temperature used in packaging industries, 260°C. In bonding, we realize the possibilities of solid state bonding of Au to Au, Au to Ag, and Ag to Cu. The idea comes from that Cu, Ag, and Au are located in the same column on periodic table, meaning that they have similar electronic configuration. They therefore have a better chance to share electrons. Also, the crystal lattice of Cu, Ag, and Au is the same, face-centered cubic. In the project, the detailed bonding mechanism is beyond the scope and here we determine the bonding by the experimental result. Ag is chosen as the joint material because of its superior physical properties. It has the highest electrical and thermal conductivities among all metals. It has low yield strength and is relatively ductile. Au is considered as well because its excellent ductility and fatigue resistance. Thus, the Ag or Au joints can deform to accommodate the shear strain caused by CTE mismatch between Si and Cu. Ag and Au have melting temperatures higher than 950°C, so the pure Ag or Au joints are expected to sustain in high operating temperature. The resulting joints do not contain any intermetallic compound. Thus, all reliability issues associated with intermetallic growth in commonly used solder joints do not exist anymore. We finally move to the applications of solid state Ag bonding in flip chip interconnects design. At present, nearly all large-scale integrated circuit (IC) chips are packaged with flip-chip technology. This means that the chip is flipped over and the active (front) side is connected to the package using a large number of tiny solder joints, which provide mechanical support, electrical connection, and heat conduction. For chip-to-package level interconnects, a challenge is the severe mismatch in coefficient of thermal expansion (CTE) between chips and package substrates. The interconnect material thus needs to be compliant to deal with the CTE mismatch. At present, nearly all flip-chip interconnects in electronic industries are made of lead-free Sn-based solders. Soft solders are chosen due to high ductility, low yield strength, relatively low melting temperature, and reasonably good electrical and thermal conductivities. In the never ending scaling down trend, more and more transistors are placed on the same Si chip size. This results in larger pin-out numbers and smaller solder joints. According to International Technology Roadmap for Semiconductors (ITRS), by 2018, the pitch in flip-chip interconnects will become smaller than 70mum for high performance applications. Two problems occur. The first is increase in shear strain. The aspect ratio of flip-chip joints is constrained to 0.7 because it goes through molten phase in the reflow process. Therefore, smaller joints become shorter as well, resulting in larger shear strain arising from CTE mismatch between Si chips and package substrates. The second is increase in stress in the joints. Since intermetallic (IMC) thickness in the joint does not scale down with joint size, ratio of IMC thickness to joint height increases. This further enlarges the shear stress because the IMC does not deform as the soft solder does to accommodate CTE mismatch. In this research, the smallest dimension we achieve for Ag flip chip interconnect joint is 15mum in diameter. The ten advantages of Ag flip chip interconnect technology can be identified as (a) High electrical conductivity, 7.7 times of that of Pb-free solders, (b) High thermal conductivity, 5.2 times of that of Pb-free solders, (c) Completely fluxless, (d) No IMCs; all reliability issues associated with IMC and IMC growth do not exist, (e) Ag is very ductile and can manage CTE mismatch between chips and packages, (f) Ag joints can sustain at very high operation temperature because Ag has high melting temperature of 961°C, (g) No molten phase involved; the bump can better keep its shape and geometry, (h) No molten phase involved; bridging of adjacent bumps is less likely to occur, i. Aspect ratio of bumps can be made greater than 1, (j) The size of the bumps is only limited by the lithographic process. Cu-Ag composite flip chip interconnect joints is developed based on three reasons. The first is lower material cost. The second is to strengthen the columns because the yield strength of Cu is 6 times of that of Ag. The third is to avoid possible Ag migration between Ag electrodes under voltage at temperatures above 250°C. This Cu-Ag composite design presents a solution in the path to the scale down roadmap.

Phase equilibria in the quasi-ternary system Ag{sub 2}Se–Ga{sub 2}Se{sub 3}–In{sub 2}Se{sub 3} and physical properties of (Ga{sub 0.6}In{sub 0.4}){sub 2}Se{sub 3}, (Ga{sub 0.594}In{sub 0.396}Er{sub 0.01}){sub 2}Se{sub 3} single crystals

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

Ivashchenko, I.A., E-mail: inna.ivashchenko@mail.ru; Danyliuk, I.V.; Olekseyuk, I.D.

2014-02-15

The quasi-ternary system Ag{sub 2}Se–Ga{sub 2}Se{sub 3}–In{sub 2}Se{sub 3} was investigated by differential thermal, X-ray phase, X-ray structure, microstructure analysis and microhardness measurements. Five quasi-binary phase diagrams, six polythermal sections, isothermal section at 820 K and the liquidus surface projection were constructed. The character and temperature of the invariant processes were determined. The specific resistance of the single crystals (Ga{sub 0.6}In{sub 0.4}){sub 2}Se{sub 3}, (Ga{sub 0.594}In{sub 0.396}Er{sub 0.01}){sub 2}Se{sub 3} was measured, 7.5×10{sup 5} and 3.15×10{sup 5} Ω m, respectively, optical absorption spectra in the 600–1050 nm range were recorded at room temperature, and the band gap energy was estimatedmore » which is 1.95±0. 01 eV for both samples. - Graphical abstract: The article reports for the first time the investigated liquidus surface projection of the Ag{sub 2}Se–Ga{sub 2}Se{sub 3}–In{sub 2}Se{sub 3} system and isothermal section at 820 K of the system. Five phase diagrams, six polythermal sections, isothermal section at 820 K and the liquidus surface projection were built at the first time. The existence of the large region of the solid solutions based on AgIn{sub 5}Se{sub 8}, Ga{sub 2}Se{sub 3} and AgGa{sub 1−x}In{sub x}Se{sub 2} was investigated. The existence of two ternary phases was established in the Ga{sub 2}Se{sub 3}–In{sub 2}Se{sub 3} system. Two single crystals (Ga{sub 0.6}In{sub 0.4}){sub 2}Se{sub 3}, (Ga{sub 0.594}In{sub 0.396}Er{sub 0.01}){sub 2}Se{sub 3} were grown and some of optical properties of them were studied at first time. Display Omitted - Highlights: • Liquidus surface projection was built for Ag{sub 2}Se–Ga{sub 2}Se{sub 3}–In{sub 2}Se{sub 3} system. • Solid solution ranges of AgIn{sub 5}Se{sub 8}, Ga{sub 2}Se{sub 3} and AgGa{sub 1−x}In{sub x}Se{sub 2} were investigated. • Two single crystals (Ga{sub 0.6}In{sub 0.4}){sub 2}Se{sub 3}, (Ga{sub 0.594}In{sub 0.396}Er{sub 0.01}){sub 2}Se{sub 3} were grown. • Some optical properties of these single crystals were studied.« less

Nanostructured Ag+-substituted fluorhydroxyapatite-TiO2 coatings for enhanced bactericidal effects and osteoinductivity of Ti for biomedical applications

PubMed Central

Chang, Xiaotong; Wang, Zhenhui; Zhang, Xuejiao; Han, Shuguang; Su, Zhuobin; Yang, Hejie; Yang, Dongdong; Zhang, Xiaojun

2018-01-01

Background Poor mechanical properties, undesirable fast dissolution rate, and lack of antibacterial activity limit the application of hydroxyapatite (HA) as an implant coating material. To overcome these limitations, a hybrid coating of Ag+-substituted fluorhydroxyapatite and titania nanotube (TNT) was prepared. Methods The incorporation of silver into the HA-TiO2 hybrid coating improves its antimicrobial properties. The addition of F as a second binary element increases the structural stability of the coating. The TNT/F-and-Ag-substituted HA (FAgHA) bilayer coating on the Ti substrate was confirmed by X-ray diffraction, scanning electron microscope, energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Results The results indicate that the FAgHA/TNT nanocomposite coating has a dense and uniform morphology with a nano-rod-like structure. The solubility measurement result shows that the substitution of F− ions into the AgHA structure has a positive effect on the dissolution resistance of HA. The adhesion strength of FAgHA/TNT has significantly increased because of the interlocking of the roughened surface with nano-rod-like particles that entered into the voids of the TiO2 nanotubes. Compared with that of the bare Ti, the corrosion current density of FAgHA/TNT-coated Ti substrate decreased from 3.71 to 0.18 μA, and its corrosion resistance increased by almost two orders of magnitude. Moreover, despite pure HA, the FAgHA killed all viable Staphylococcus aureus after 24 hours of incubation. Although the fabricated FAgHA/TNT coating is hydrophobic, it induced deposition of the typical spherical apatite when immersed in a simulated body fluid (SBF); the osteoblasts spread very well on the surface of the coating. In addition, in vitro cell culture tests demonstrated cell viability and alkaline phosphatase (ALP) similar to pure HA, which indicated good cytocompatibility. Interestingly, compared with bare Ti, FAgHA/TNT-coated Ti surface was innocent for cell vitality and even more beneficial for cell osteogenesis in vitro. Conclusion Enhancing the osseointegration and preventing infection in implants, the FAgHA/TNT-coated Ti makes implants more successful. PMID:29760549

Acoustic levitation with self-adaptive flexible reflectors.

PubMed

Hong, Z Y; Xie, W J; Wei, B

2011-07-01

Two kinds of flexible reflectors are proposed and examined in this paper to improve the stability of single-axis acoustic levitator, especially in the case of levitating high-density and high-temperature samples. One kind is those with a deformable reflecting surface, and the other kind is those with an elastic support, both of which are self-adaptive to the change of acoustic radiation pressure. High-density materials such as iridium (density 22.6 gcm(-3)) are stably levitated at room temperature with a soft reflector made of colloid as well as a rigid reflector supported by a spring. In addition, the containerless melting and solidification of binary In-Bi eutectic alloy (melting point 345.8 K) and ternary Ag-Cu-Ge eutectic alloy (melting point 812 K) are successfully achieved by applying the elastically supported reflector with the assistance of a laser beam.

Acoustic levitation with self-adaptive flexible reflectors

NASA Astrophysics Data System (ADS)

Hong, Z. Y.; Xie, W. J.; Wei, B.

2011-07-01

Two kinds of flexible reflectors are proposed and examined in this paper to improve the stability of single-axis acoustic levitator, especially in the case of levitating high-density and high-temperature samples. One kind is those with a deformable reflecting surface, and the other kind is those with an elastic support, both of which are self-adaptive to the change of acoustic radiation pressure. High-density materials such as iridium (density 22.6 gcm-3) are stably levitated at room temperature with a soft reflector made of colloid as well as a rigid reflector supported by a spring. In addition, the containerless melting and solidification of binary In-Bi eutectic alloy (melting point 345.8 K) and ternary Ag-Cu-Ge eutectic alloy (melting point 812 K) are successfully achieved by applying the elastically supported reflector with the assistance of a laser beam.

Nickel-silver alloy electrocatalysts for hydrogen evolution and oxidation in an alkaline electrolyte.

PubMed

Tang, Maureen H; Hahn, Christopher; Klobuchar, Aidan J; Ng, Jia Wei Desmond; Wellendorff, Jess; Bligaard, Thomas; Jaramillo, Thomas F

2014-09-28

The development of improved catalysts for the hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR) in basic electrolytes remains a major technical obstacle to improved fuel cells, water electrolyzers, and other devices for electrochemical energy storage and conversion. Based on the free energy of adsorbed hydrogen intermediates, theory predicts that alloys of nickel and silver are active for these reactions. In this work, we synthesize binary nickel-silver bulk alloys across a range of compositions and show that nickel-silver alloys are indeed more active than pure nickel for hydrogen evolution and, possibly, hydrogen oxidation. To overcome the mutual insolubility of silver and nickel, we employ electron-beam physical vapor codeposition, a low-temperature synthetic route to metastable alloys. This method also produces flat and uniform films that facilitate the measurement of intrinsic catalytic activity with minimal variations in the surface area, ohmic contact, and pore transport. Rotating-disk-electrode measurements demonstrate that the hydrogen evolution activity per geometric area of the most active catalyst in this study, Ni0.75Ag0.25, is approximately twice that of pure nickel and has comparable stability and hydrogen oxidation activity. Our experimental results are supported by density functional theory calculations, which show that bulk alloying of Ni and Ag creates a variety of adsorption sites, some of which have near-optimal hydrogen binding energy.

Statistical physics of multicomponent alloys using KKR-CPA

DOE PAGES

Khan, Suffian N.; Staunton, Julie B.; Stocks, George Malcolm

2016-02-16

We apply variational principles from statistical physics and the Landau theory of phase transitions to multicomponent alloys using the multiple-scattering theory of Korringa-Kohn-Rostoker (KKR) and the coherent potential approximation (CPA). This theory is a multicomponent generalization of the S( 2) theory of binary alloys developed by G. M. Stocks, J. B. Staunton, D. D. Johnson and others. It is highly relevant to the chemical phase stability of high-entropy alloys as it predicts the kind and size of finite-temperature chemical fluctuations. In doing so it includes effects of rearranging charge and other electronics due to changing site occupancies. When chemical fluctuationsmore » grow without bound an absolute instability occurs and a second-order order-disorder phase transition may be inferred. The S( 2) theory is predicated on the fluctuation-dissipation theorem; thus we derive the linear response of the CPA medium to perturbations in site-dependent chemical potentials in great detail. The theory lends itself to a natural interpretation in terms of competing effects: entropy driving disorder and favorable pair interactions driving atomic ordering. Moreover, to further clarify interpretation we present results for representative ternary alloys CuAgAu, NiPdPt, RhPdAg, and CoNiCu within a frozen charge (or band-only) approximation. These results include the so-called Onsager mean field correction that extends the temperature range for which the theory is valid.« less

Discontinuous and continuous hardening processes in calcium and calcium—tin micro-alloyed lead: influence of 'secondary-lead' impurities

NASA Astrophysics Data System (ADS)

Bouirden, L.; Hilger, J. P.; Hertz, J.

Different transformations in leadcalcium and leadcaciumtin alloys are observed with various complementary techniques such as anisothermal microcalorimetry, optical and electronic microscopy, hardness measurements. Three alloy states are studied: as-cast, rehomogenised/water-quenched, rehomogenised/air-cooled. With binary leadcalcium alloys, three successive discontinuous transformations are observed, namely: an initial and complete discontinuous transformation with regular moving of the front of reaction; a second and incomplete discontinuous transformation (puzzle-shaped); a third and incomplete discontinuous transformation with precipitation of Pb 3Ca. The role of secondary-lead impurities is complex: Ag reduces and Bi accelerates the rate of the discontinuous reaction, while Al refines the grain size. Leadcalciumtin are characterized by the Sn/Ca ratio. For very small values of this ratio, the hardening is similar to that of leadcalcium alloys. For high ratio values, the hardening takes place after an incubation period and proceeds via a continuous micro-precipitation of the (PbSn) 3Ca Compound. For intermediate ratios, the different processes are able to operate separately in sequence. Ag increases the rate of the continuous precipitation and reduces the incubation time. No significant effects are observed with Bi or Al. The kinetic laws of the different transformations are presented and values for the energy of activation are determined.

Application of Molecular Interaction Volume Model for Phase Equilibrium of Sn-Based Binary System in Vacuum Distillation

NASA Astrophysics Data System (ADS)

Kong, Lingxin; Yang, Bin; Xu, Baoqiang; Li, Yifu

2014-09-01

Based on the molecular interaction volume model (MIVM), the activities of components of Sn-Sb, Sb-Bi, Sn-Zn, Sn-Cu, and Sn-Ag alloys were predicted. The predicted values are in good agreement with the experimental data, which indicate that the MIVM is of better stability and reliability due to its good physical basis. A significant advantage of the MIVM lies in its ability to predict the thermodynamic properties of liquid alloys using only two parameters. The phase equilibria of Sn-Sb and Sn-Bi alloys were calculated based on the properties of pure components and the activity coefficients, which indicates that Sn-Sb and Sn-Bi alloys can be separated thoroughly by vacuum distillation. This study extends previous investigations and provides an effective and convenient model on which to base refining simulations for Sn-based alloys.

Design, Qualification and Lessons Learned of the Shutter Calibration Mechanism for EnMAP Mission

NASA Astrophysics Data System (ADS)

Schmidt, Tilo; Muller, Silvio; Bergander, Arvid; Zajac, Kai; Seifart, Klaus

2015-09-01

The Shutter Calibration Mechanism (SCM) Assembly is one of three mechanisms which are developed by HTS for the EnMAP instrument in subcontract to OHB System AG Munich. EnMAP is the Environmental Mapping and Analysis Program of the German Space Agency DLR.The binary rotary encoder of the SCM using hall-effect sensors was already presented during ESMATS 2011. This paper summarizes the main functions and design features of the Hardware and focuses on qualification testing which has finished successfully in 2014. Of particular interest is the functional testing of the main drive including the precise hall-effect position sensing system and the test of the fail safe mechanism. In addition to standard test campaign required for QM also a shock emission measurement of the fail safe mechanism activation was conducted.Test conduction and results will be presented with focus on deviations from the expected behaviour, mitigation measures and on lessons learned.

Central nervous system drug consumption depending on the time between symptom onset and the diagnosis of Alzheimer's disease: an analysis by the Registry of Dementias of Girona.

PubMed

Calvó-Perxas, Laia; López-Pousa, Secundino; Vilalta-Franch, Joan; Turró-Garriga, Oriol; Blankenburg, Michael; Febrer, Laia; Flaqué, Margarida; Vallmajó, Natàlia; Aguirregomozcorta, Maria; Genís, David; Casas, Isabel; Perkal, Héctor; Coromina, Joan; Garre-Olmo, Josep

2012-01-01

To describe central nervous system (CNS) drug consumption patterns depending on the time to diagnosis of Alzheimer's disease (AD), and to check whether the cases diagnosed later are associated with greater severity and consuming more CNS drugs. Cross-sectional study using 952 cases of the Registry of Dementias of Girona. A binary logistic regression was used to detect variables associated with the use of CNS drugs depending on the time to diagnosis. CNS drugs were consumed by 95.8% of the AD patients. Only antipsychotics presented a statistically significant increase in the frequency of prescription to patients with longer time elapsed from symptom onset to AD diagnosis. Longer time elapsed from the onset of symptoms to the diagnosis resulted in increased probability of antipsychotic consumption. Copyright © 2012 S. Karger AG, Basel.

Photometry of symbiotic stars. XI. EG And, Z And, BF Cyg, CH Cyg, CI Cyg, V1329 Cyg, TX CVn, AG Dra, RW Hya, AR Pav, AG Peg, AX Per, QW Sge, IV Vir and the LMXB V934 Her

NASA Astrophysics Data System (ADS)

Skopal, A.; Pribulla, T.; Vaňko, M.; Velič, Z.; Semkov, E.; Wolf, M.; Jones, A.

2004-02-01

We present new photometric observations of EG And, Z And, BF Cyg, CH Cyg, CI Cyg, V1329 Cyg, TX CVn, AG Dra, RW Hya, AG Peg, AX Per, IV Vir and the peculiar M giant V934 Her, which were made in the standard Johnson UBV(R) system. QW Sge was measured in the Kron-Cousin B, V, RC, IC system and for AR Pav we present its new visual estimates. The current issue gathers observations of these objects to December 2003. The main results can be summarized as follows: EG And: The primary minimum in the U light curve (LC) occurred at the end of 2002. A 0.2 -- 0.3 mag brightening in U was detected in the autumn of 2003. Z And: At around August 2002 we detected for the first time a minimum, which is due to eclipse of the active object by the red giant. Measurements from 2003.3 are close to those of a quiescent phase. BF Cyg: In February 2003 a short-term flare developed in the LC. A difference in the depth of recent minima was detected. CH Cyg: This star was in a quiescent phase at a rather bright state. A shallow minimum occurred at ˜ JD 2 452 730, close to the position of the inferior conjunction of the giant in the inner binary of the triple-star model of CH Cyg. CI Cyg: Our observations cover the descending branch of a broad minimum. TX CVn: At/around the beginning of 2003 the star entered a bright stage containing a minimum at ˜ JD 2 452 660. AG Dra: New observations revealed two eruptions, which peaked in October 2002 and 2003 at ˜ 9.3 in U. AR Pav: Our new visual estimates showed a transient disappearance of a wave-like modulation in the star's brightness between the minima at epochs E = 66 and E = 68 and its reappearance. AG Peg: Our measurements from the end of 2001 showed rather complex profile of the LC. RW Hya: Observations follow behaviour of the wave-like variability of quiet symbiotics. AX Per: In May 2003 a 0.5 mag flare was detected following a rapid decrease of the light to a minimum. QW Sge: CCD observations in B, V, RC, IC bands cover a period from 1994.5 to 2003.5. An increase in the star's brightness by about 1 mag was observed in all passbands in 1997. Less pronounced brightening was detected in 1999/2000. V934 Her: Our observations did not show any larger variation in the optical as a reaction to its X-ray activity.

In vitro corrosion and biocompatibility of binary magnesium alloys.

PubMed

Gu, Xuenan; Zheng, Yufeng; Cheng, Yan; Zhong, Shengping; Xi, Tingfei

2009-02-01

As bioabsorbable materials, magnesium alloys are expected to be totally degraded in the body and their biocorrosion products not deleterious to the surrounding tissues. It's critical that the alloying elements are carefully selected in consideration of their cytotoxicity and hemocompatibility. In the present study, nine alloying elements Al, Ag, In, Mn, Si, Sn, Y, Zn and Zr were added into magnesium individually to fabricate binary Mg-1X (wt.%) alloys. Pure magnesium was used as control. Their mechanical properties, corrosion properties and in vitro biocompatibilities (cytotoxicity and hemocompatibility) were evaluated by SEM, XRD, tensile test, immersion test, electrochemical corrosion test, cell culture and platelet adhesion test. The results showed that the addition of alloying elements could influence the strength and corrosion resistance of Mg. The cytotoxicity tests indicated that Mg-1Al, Mg-1Sn and Mg-1Zn alloy extracts showed no significant reduced cell viability to fibroblasts (L-929 and NIH3T3) and osteoblasts (MC3T3-E1); Mg-1Al and Mg-1Zn alloy extracts indicated no negative effect on viabilities of blood vessel related cells, ECV304 and VSMC. It was found that hemolysis and the amount of adhered platelets decreased after alloying for all Mg-1X alloys as compared to the pure magnesium control. The relationship between the corrosion products and the in vitro biocompatibility had been discussed and the suitable alloying elements for the biomedical applications associated with bone and blood vessel had been proposed.

Association of Brain-Derived Neurotrophic Factor and Vitamin D with Depression and Obesity: A Population-Based Study.

PubMed

Goltz, Annemarie; Janowitz, Deborah; Hannemann, Anke; Nauck, Matthias; Hoffmann, Johanna; Seyfart, Tom; Völzke, Henry; Terock, Jan; Grabe, Hans Jörgen

2018-06-19

Depression and obesity are widespread and closely linked. Brain-derived neurotrophic factor (BDNF) and vitamin D are both assumed to be associated with depression and obesity. Little is known about the interplay between vitamin D and BDNF. We explored the putative associations and interactions between serum BDNF and vitamin D levels with depressive symptoms and abdominal obesity in a large population-based cohort. Data were obtained from the population-based Study of Health in Pomerania (SHIP)-Trend (n = 3,926). The associations of serum BDNF and vitamin D levels with depressive symptoms (measured using the Patient Health Questionnaire) were assessed with binary and multinomial logistic regression models. The associations of serum BDNF and vitamin D levels with obesity (measured by the waist-to-hip ratio [WHR]) were assessed with binary logistic and linear regression models with restricted cubic splines. Logistic regression models revealed inverse associations of vitamin D with depression (OR = 0.966; 95% CI 0.951-0.981) and obesity (OR = 0.976; 95% CI 0.967-0.985). No linear association of serum BDNF with depression or obesity was found. However, linear regression models revealed a U-shaped association of BDNF with WHR (p < 0.001). Vitamin D was inversely associated with depression and obesity. BDNF was associated with abdominal obesity, but not with depression. At the population level, our results support the relevant roles of vitamin D and BDNF in mental and physical health-related outcomes. © 2018 S. Karger AG, Basel.

A time domain experiment with Swift: monitoring of seven nearby galaxies

NASA Astrophysics Data System (ADS)

Andreoni, I.; D'Avanzo, P.; Campana, S.; Branchesi, M.; Bernardini, M. G.; Della Valle, M.; Mannucci, F.; Melandri, A.; Tagliaferri, G.

2016-03-01

Context. Focused on the study of transient sources, time domain astronomy today is one of the most active and growing areas of research in astronomy. Most of the present and planned surveys aimed at carrying out time domain studies work in the optical band and founded their searching strategies on fixed cadences. Although nothing similar currently exists in the X-ray and ultraviolet (UV) bands, the Swift satellite is certainly the most appropriate available instrument to carry out such surveys. Aims: We aimed to detect a supernova (SN) shock breakout (SBO) in nearby galaxies. The SBO marks the first escape of radiation from the blast wave that breaks through the photosphere of the star and launches the SN ejecta. The detection of an SBO is a diagnostic for the radius of the progenitor star and the ratio of explosion energy to ejecta mass. It also allows us to determine the onset of the explosion with an accuracy of a few hours to a few seconds. Methods: Using the XRT and UVOT instruments onboard the Swift satellite, we carried out a weekly cadenced, six-month monitoring of seven nearby galaxies: NGC 1084, NGC 2207/IC 2163, NGC 2770, NGC 4303/M 61, NGC 3147, NGC 3690, and NGC 6754. We searched for variable or transient sources in the collected data. These galaxies were selected because they are close (distance ≤50 Mpc), small enough to fit in the Swift/UVOT field of view, and are hosts of at least three SNe in the past 20 yr. Results: We found no evidence for an SN SBO event. Five objects located within the light of the sample galaxies were found to be variable in the X-ray and/or in the UV. These include mainly background active galactic nucleus and unresolved ULX in NGC 3690. In addition to these objects, we found two variable Galactic sources: the known nova CP Draconis (which experienced an outburst during our monitoring) and an uncatalogued eclipsing binary. Conclusions: Despite the lack of SBO detections, the results of our explorative study encourage the use of Swift in further time domain studies. Moreover, since our sample galaxies are within the Universe volume that will be reached by the forthcoming advanced gravitational wave (GW) detectors (a-LIGO and a-Virgo), this work provides an example on how to carry out Swift surveys from which the GW signal from SNe can be detected, and to detect counterparts to GW triggers.

Theory and Application of Photoelectron Diffraction for Complex Oxide Systems

NASA Astrophysics Data System (ADS)

Chassé, Angelika; Chassé, Thomas

2018-06-01

X-ray photoelectron diffraction (XPD) has been used to investigate film structures and local sites of surface and dopant atoms in complex oxide materials. We have performed angular-resolved measurements of intensity distribution curves (ADCs) and patterns (ADPs) of elemental core level intensities from binary to quaternary mixed oxide samples and compared them to multiple-scattering cluster (MSC) calculations in order to derive information on structural models and related parameters. MSC calculations permitted to describe both bulk diffraction features of binary oxide MnO(001) and the thickness-dependence of the tetragonal distortion of epitaxial MnO films on Ag(001). XPD was further used to investigate the surface termination of perovskite SrTiO3 and BaTiO3 substrates in order to evaluate influence of different ex situ and in situ preparation procedures on the surface layers, which are crucial for quality of following film growth. Despite the similarity of local environments of Sr (Ba) and Ti atoms in the perovskite film structure an angular region in the ADCs was identified as a fingerprint with the help of MSC simulations which provided clear conclusions on the perovskite oxide surfaces. Dopant sites in quaternary perovskite manganites La1-xCaxMnO3, La1-xSrxMnO3, and La1-xCexMnO3 were studied with polar angle scans of the photoemission intensities of host and dopant atoms. Both direct comparison of experimental ADCs and to the simulations within MSC models confirm the occupation of A sites by the dopants and the structural quality of the complex oxide films.

Biomimetic hydrophobic surface fabricated by chemical etching method from hierarchically structured magnesium alloy substrate

NASA Astrophysics Data System (ADS)

Liu, Yan; Yin, Xiaoming; Zhang, Jijia; Wang, Yaming; Han, Zhiwu; Ren, Luquan

2013-09-01

As one of the lightest metal materials, magnesium alloy plays an important role in industry such as automobile, airplane and electronic product. However, magnesium alloy is hindered due to its high chemical activity and easily corroded. Here, inspired by typical plant surfaces such as lotus leaves and petals of red rose with super-hydrophobic character, the new hydrophobic surface is fabricated on magnesium alloy to improve anti-corrosion by two-step methodology. The procedure is that the samples are processed by laser first and then immersed and etched in the aqueous AgNO3 solution concentrations of 0.1 mol/L, 0.3 mol/L and 0.5 mol/L for different times of 15 s, 40 s and 60 s, respectively, finally modified by DTS (CH3(CH2)11Si(OCH3)3). The microstructure, chemical composition, wettability and anti-corrosion are characterized by means of SEM, XPS, water contact angle measurement and electrochemical method. The hydrophobic surfaces with microscale crater-like and nanoscale flower-like binary structure are obtained. The low-energy material is contained in surface after DTS treatment. The contact angles could reach up to 138.4 ± 2°, which hydrophobic property is both related to the micro-nano binary structure and chemical composition. The results of electrochemical measurements show that anti-corrosion property of magnesium alloy is improved. Furthermore, our research is expected to create some ideas from natural enlightenment to improve anti-corrosion property of magnesium alloy while this method can be easily extended to other metal materials.

Elastic moduli of cast Ti-Au, Ti-Ag, and Ti-Cu alloys.

PubMed

Kikuchi, Masafumi; Takahashi, Masatoshi; Okuno, Osamu

2006-07-01

This study investigated the effect of alloying titanium with gold, silver, or copper on the elastic properties of the alloys. A series of binary titanium alloys was made with four concentrations of gold, silver, or copper (5, 10, 20, and 30 mass%) in an argon-arc melting furnace. The Young's moduli and Poisson's ratios of the alloy castings were determined with an ultrasonic-pulse method. The density of each alloy was previously measured by the Archimedes' principle. Results were analyzed using one-way ANOVA and the Scheffé's test. The densities of Ti-Au, Ti-Ag, and Ti-Cu alloys monotonically increased as the concentration of alloying elements increased. As the concentration of gold or silver increased to 20%, the Young's modulus significantly decreased, followed by a subsequent increase in value. As the concentration of copper increased, the Young's modulus monotonically increased. The Young's moduli of all the Ti-Cu alloys were significantly higher than that of the titanium. The density of all the experimental alloys was virtually independent of the alloy phases, while the Young's moduli and Poisson's ratios of the alloys were dependent. The addition of gold or silver slightly reduced the Young's modulus of the titanium when the alloy phase was single alpha. The increase in the Young's modulus of the Ti-Cu alloys is probably due to the precipitation of intermetallic compound Ti2Cu. Copper turned out to be a moderate stiffener that gains a Young's modulus of titanium up to 20% at the copper concentration of 30 mass%.

[Quantitative surface analysis of Pt-Co, Cu-Au and Cu-Ag alloy films by XPS and AES].

PubMed

Li, Lian-Zhong; Zhuo, Shang-Jun; Shen, Ru-Xiang; Qian, Rong; Gao, Jie

2013-11-01

In order to improve the quantitative analysis accuracy of AES, We associated XPS with AES and studied the method to reduce the error of AES quantitative analysis, selected Pt-Co, Cu-Au and Cu-Ag binary alloy thin-films as the samples, used XPS to correct AES quantitative analysis results by changing the auger sensitivity factors to make their quantitative analysis results more similar. Then we verified the accuracy of the quantitative analysis of AES when using the revised sensitivity factors by other samples with different composition ratio, and the results showed that the corrected relative sensitivity factors can reduce the error in quantitative analysis of AES to less than 10%. Peak defining is difficult in the form of the integral spectrum of AES analysis since choosing the starting point and ending point when determining the characteristic auger peak intensity area with great uncertainty, and to make analysis easier, we also processed data in the form of the differential spectrum, made quantitative analysis on the basis of peak to peak height instead of peak area, corrected the relative sensitivity factors, and verified the accuracy of quantitative analysis by the other samples with different composition ratio. The result showed that the analytical error in quantitative analysis of AES reduced to less than 9%. It showed that the accuracy of AES quantitative analysis can be highly improved by the way of associating XPS with AES to correct the auger sensitivity factors since the matrix effects are taken into account. Good consistency was presented, proving the feasibility of this method.

Generalized stacking fault energies of alloys.

PubMed

Li, Wei; Lu, Song; Hu, Qing-Miao; Kwon, Se Kyun; Johansson, Börje; Vitos, Levente

2014-07-02

The generalized stacking fault energy (γ surface) provides fundamental physics for understanding the plastic deformation mechanisms. Using the ab initio exact muffin-tin orbitals method in combination with the coherent potential approximation, we calculate the γ surface for the disordered Cu-Al, Cu-Zn, Cu-Ga, Cu-Ni, Pd-Ag and Pd-Au alloys. Studying the effect of segregation of the solute to the stacking fault planes shows that only the local chemical composition affects the γ surface. The calculated alloying trends are discussed using the electronic band structure of the base and distorted alloys.Based on our γ surface results, we demonstrate that the previous revealed 'universal scaling law' between the intrinsic energy barriers (IEBs) is well obeyed in random solid solutions. This greatly simplifies the calculations of the twinning measure parameters or the critical twinning stress. Adopting two twinnability measure parameters derived from the IEBs, we find that in binary Cu alloys, Al, Zn and Ga increase the twinnability, while Ni decreases it. Aluminum and gallium yield similar effects on the twinnability.

A thermodynamic database for tellurium-bearing systems relevant to nuclear technology

NASA Astrophysics Data System (ADS)

Chattopadhyay, G.; Juneja, J. M.

1993-06-01

A thermodynamic database for tellurium-bearing condensed phases and gaseous species which are relevant to nuclear technology is presented. It contains phase diagrams of the binary systems, PdTe, RhTe, PuTe, SmTe, CsTe, ZrTe, of the ternary systems, ZrTeO, MoTeO, AgTeO, UTeO, CsTeO, BaTeO as well as thermodynamic data for crystalline and liquid Te, for the solid phases Cs 2Te, Ag 2Te, SnTe, BaTe, CeTe, SmTe, RuTe 2, ZrTe 2, Fe 0.53Te 0.47, Mo 0.43Te 0.57, Cr 0.43Te 0.57, Ni 0.5Te 0.4, Cs 2TeO 3 and for the gaseous species, Te, Te 2, TeO, TeO 2, TeO(OH) 2, H 2Te, TeI, TeI 2, TeI 4, TeOI 2, SnTe, Sn 2Te 2, SnTe 2.

Rapid solidification of high-conductivity copper alloys. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Bloom, Theodore Atlas

1989-01-01

The main objective was to develop improved copper alloys of high strength and high thermal and electric conductivity. Chill block melt spinning was used to produce binary alloys of Cu-Cr and Cu-Zr, and ternary alloys of Cu-Cr-Ag. By quenching from the liquid state, up to 5 atomic percent of Cr and Zr were retained in metastable extended solid solution during the rapid solidification process. Eutectic solidification was avoided and the full strengthening benefits of the large volume fraction of precipitates were realized by subsequent aging treatment. The very low solid solubility of Cr and Zr in Cu result in a high conductivity Cu matrix strengthened by second phase precipitates. Tensile properties on as-cast and aged ribbons were measured at room and elevated temperatures. Precipitate coarsening of Cr in Cu was studied by changes in electrical resistance during aging. X-ray diffraction was used to measure the lattice parameter and the degree of supersaturation of the matrix. The microstructures were characterized by optical and electron microscopy.

On the nature of bonding in binary Be2O2 and Si2O2 clusters: rhombic four-center four-electron π and σ bonds.

PubMed

Wang, Kang; Wang, Ying-Jin; Li, Da-Zhi; Ou, Ting; Zhao, Xiao-Yun; Zhai, Hua-Jin

2016-04-14

The structural and electronic properties and chemical bonding of binary Be2O2 and Si2O2 clusters have been studied using quantum chemical calculations at the B3LYP level. For the Be2O2 cluster, the potential energy surface is probed by unbiased structural searches and the global-minimum structure was established using the B3LYP calculations, complemented by PBE0 and single-point CCSD(T) calculations for top isomers. The perfectly planar D2h Be2O2 ((1)Ag) global minimum is well defined, being at least 3.64 eV lower in energy than alternative structures at the CCSD(T)//B3LYP/aug-cc-pVTZ level. Chemical bonding analyses show that D2h Be2O2 and Si2O2 clusters possess the rhombic four-center four-electron (4c-4e) π bond, that is, the o-bond, a conception derived from electron-deficient boron oxide clusters lately. Furthermore, the Be2O2 and Si2O2 clusters also exhibit rhombic 4c-4e σ bonds, both for the radial and tangential σ frameworks (σr and σt). The σt framework is classified as an o-bond only formally, due to the secondary contribution from the Be/Si s component. The three-fold (π, σr, and σt) o-bonds in Be2O2 and Si2O2 are considered to resemble the three-fold aromaticity in all-metal Al4(2-) dianions. A 4c-4e o-bond makes use of four O 2p electrons, which would otherwise be two lone-pairs, for a delocalized and completely bonding orbital, as well as a residual nonbonding orbital. Three-fold o-bonds thus greatly stabilize the binary Be2O2 and Si2O2 clusters. We anticipate that the bonding concept should be applicable to additional molecular systems, including those with larger heterocyclic rings.

Improved prediction of heat of mixing and segregation in metallic alloys using tunable mixing rule for embedded atom method

NASA Astrophysics Data System (ADS)

Divi, Srikanth; Agrahari, Gargi; Ranjan Kadulkar, Sanket; Kumar, Sanjeet; Chatterjee, Abhijit

2017-12-01

Capturing segregation behavior in metal alloy nanoparticles accurately using computer simulations is contingent upon the availability of high-fidelity interatomic potentials. The embedded atom method (EAM) potential is a widely trusted interatomic potential form used with pure metals and their alloys. When limited experimental data is available, the A-B EAM cross-interaction potential for metal alloys AxB 1-x are often constructed from pure metal A and B potentials by employing a pre-defined ‘mixing rule’ without any adjustable parameters. While this approach is convenient, we show that for AuPt, NiPt, AgAu, AgPd, AuNi, NiPd, PtPd and AuPd such mixing rules may not even yield the correct alloy properties, e.g., heats of mixing, that are closely related to the segregation behavior. A general theoretical formulation based on scaling invariance arguments is introduced that addresses this issue by tuning the mixing rule to better describe alloy properties. Starting with an existing pure metal EAM potential that is used extensively in literature, we find that the mixing rule fitted to heats of mixing for metal solutions usually provides good estimates of segregation energies, lattice parameters and cohesive energy, as well as equilibrium distribution of metals within a nanoparticle using Monte Carlo simulations. While the tunable mixing rule generally performs better than non-adjustable mixing rules, the use of the tunable mixing rule may still require some caution. For e.g., in Pt-Ni system we find that the segregation behavior can deviate from the experimentally observed one at Ni-rich compositions. Despite this the overall results suggest that the same approach may be useful for developing improved cross-potentials with other existing pure metal EAM potentials as well. As a further test of our approach, mixing rule estimated from binary data is used to calculate heat of mixing in AuPdPt, AuNiPd, AuPtNi, AgAuPd and NiPtPd. Excellent agreement with experiments is observed for AuPdPt.

By Draconis Stars

NASA Astrophysics Data System (ADS)

Bopp, Bernard W.

An optical spectroscopic survey of dK-M stars has resulted in the discovery of several new H-alpha emission objects. Available optical data suggest these stars have a level of chromospheric activity midway between active BY Dra stars and quiet dM's. These "marginal" BY Dra stars are single objects that have rotation velocities slightly higher than that of quiet field stars but below that of active flare/BY Dra objects. The marginal BY Dra stars provide us with a class of objects rotating very near a "trigger velocity" (believed to be 5 km/s) which appears to divide active flare/BY Dra stars from quiet dM's. UV data on Mg II emission fluxes and strength of transition region features such as C IV will serve to fix activity levels in the marginal objects and determine chromosphere and transition-region heating rates. Simultaneous optical magnetic field measures will be used to explore the connection between fieldstrength/filling-factor and atmospheric heating. Comparison of these data with published information on active and quiet dM stars will yield information on the character of the stellar dynamo as it makes a transition from "low" to "high" activity.

Tunable plasmon resonance and enhanced second harmonic generation and upconverted fluorescence of hemispheric-like silver core/shell islands

NASA Astrophysics Data System (ADS)

Ding, Si-Jing; Nan, Fan; Yang, Da-Jie; Zhong, Yu-Ting; Hao, Zhong-Hua; Wang, Qu-Quan

2015-09-01

We investigate tunable plasmon resonance and enhanced second harmonic generation (SHG) and up-converted fluorescence (UCF) of the hemispheric-like silver core/shell islands. The Ag, Ag/Ag2O, and Ag/Ag2O/Ag island films are prepared by using a sputtering technique. The SHG and UCF of the Ag/Ag2O/Ag core/shell islands near the percolating regime is enhanced 2.34 and 3.94 times compared to the sum of two individual counterparts of Ag/Ag2O core/shell and Ag shell islands. The ratio of SHG intensity induced by p- and s-polarization is 0.86 for the initial Ag islands and increase to 1.61 for the Ag/Ag2O/Ag core/shell samples. The tunable intensity ratio of SHG to UCF of the Ag islands treated by thermal and laser annealing processes is also observed. The physical mechanism of the enhanced SHG and UCF in the Ag/Ag2O/Ag core/shell islands is discussed. Our observations provide a new approach to fabricate plasmon-enhanced optical nonlinear nanodevices with tunable SHG and UCF.We investigate tunable plasmon resonance and enhanced second harmonic generation (SHG) and up-converted fluorescence (UCF) of the hemispheric-like silver core/shell islands. The Ag, Ag/Ag2O, and Ag/Ag2O/Ag island films are prepared by using a sputtering technique. The SHG and UCF of the Ag/Ag2O/Ag core/shell islands near the percolating regime is enhanced 2.34 and 3.94 times compared to the sum of two individual counterparts of Ag/Ag2O core/shell and Ag shell islands. The ratio of SHG intensity induced by p- and s-polarization is 0.86 for the initial Ag islands and increase to 1.61 for the Ag/Ag2O/Ag core/shell samples. The tunable intensity ratio of SHG to UCF of the Ag islands treated by thermal and laser annealing processes is also observed. The physical mechanism of the enhanced SHG and UCF in the Ag/Ag2O/Ag core/shell islands is discussed. Our observations provide a new approach to fabricate plasmon-enhanced optical nonlinear nanodevices with tunable SHG and UCF. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03627e

AgI/Ag{sub 3}PO{sub 4} hybrids with highly efficient visible-light driven photocatalytic activity

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

Katsumata, Hideyuki, E-mail: hidek@chem.mie-u.ac.jp; Hayashi, Takahiro; Taniguchi, Masanao

Highlights: • AgI/Ag{sub 3}PO{sub 4} hybrid was prepared via an in situ anion-exchange method. • AgI/Ag{sub 3}PO{sub 4} displays the excellent photocatalytic activity under visible light. • AgI/Ag{sub 3}PO{sub 4} readily transforms to be Ag@AgI/Ag{sub 3}PO{sub 4} system. • h{sup +} and O{sub 2}{sup ·−} play the major role in the AO 7 decolorization over AgI/Ag{sub 3}PO{sub 4}. • The activity enhancement is ascribed to a Z-scheme system composed of Ag{sub 3}PO{sub 4}, Ag and AgI. - Abstract: Highly efficient visible-light-driven AgI/Ag{sub 3}PO{sub 4} hybrid photocatalysts with different mole ratios of AgI were prepared via an in situ anion-exchange methodmore » and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) technique. Under visible light irradiation (>420 nm), the AgI/Ag{sub 3}PO{sub 4} photocatalysts displayed the higher photocatalytic activity than pure Ag{sub 3}PO{sub 4} and AgI for the decolorization of acid orange 7 (AO 7). Among the hybrid photocatalysts, AgI/Ag{sub 3}PO{sub 4} with 80% of AgI exhibited the highest photocatalytic activity for the decolorization of AO 7. X-ray photoelectron spectroscopy (XPS) results revealed that AgI/Ag{sub 3}PO{sub 4} readily transformed to be Ag@AgI/Ag{sub 3}PO{sub 4} system while the photocatalytic activity of AgI/Ag{sub 3}PO{sub 4} remained after 5 recycling runs. In addition, the quenching effects of different scavengers displayed that the reactive h{sup +} and O{sub 2}{sup ·−} play the major role in the AO 7 decolorization. The photocatalytic activity enhancement of AgI/Ag{sub 3}PO{sub 4} hybrids can be ascribed to the efficient separation of electron–hole pairs through a Z-scheme system composed of Ag{sub 3}PO{sub 4}, Ag and AgI, in which Ag nanoparticles act as the charge separation center.« less

A visible-light-driven core-shell like Ag2S@Ag2CO3 composite photocatalyst with high performance in pollutants degradation.

PubMed

Yu, Changlin; Wei, Longfu; Zhou, Wanqin; Dionysiou, Dionysios D; Zhu, Lihua; Shu, Qing; Liu, Hong

2016-08-01

A series of Ag2S-Ag2CO3 (4%, 8%, 16%, 32% and 40% Ag2S), Ag2CO3@Ag2S (32%Ag2S) and Ag2S@Ag2CO3 (32%Ag2S) composite photocatalysts were fabricated by coprecipitation or successive precipitation reaction. The obtained catalysts were analyzed by N2 physical adsorption, powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, UV-vis diffuse reflectance spectroscopy and photocurrent test. Under visible light irradiation, the influences of Ag2S content and core-shell property on photocatalytic activity and stability were evaluated in studies focused on the degradation of methyl orange (MO) dye, phenol, and bisphenol A. Results showed that excellent photocatalytic performance was obtained over Ag2S/Ag2CO3 composite photocatalysts with respect to Ag2S and Ag2CO3. With optimal content of Ag2S (32 wt%), the Ag2S-Ag2CO3 showed the highest photocatalytic degradation efficiency. Moreover, the structured property of Ag2S/Ag2CO3 greatly influenced the activity. Compared with Ag2S-Ag2CO3 and Ag2CO3@Ag2S, core-shell like Ag2S@Ag2CO3 demonstrated the highest activity and stability. The main reason for the boosting of photocatalytic performance was due to the formation of Ag2S/Ag2CO3 well contacted interface and unique electron structures. Ag2S/Ag2CO3 interface could significantly increase the separation efficiency of the photo-generated electrons (e(-)) and holes (h(+)), and production of OH radicals. More importantly, the low solubility of Ag2S shell could effectively protect the core of Ag2CO3, which further guarantees the stability of Ag2CO3. Copyright © 2016 Elsevier Ltd. All rights reserved.

Influence of hardness on the bioavailability of silver to a freshwater snail after waterborne exposure to silver nitrate and silver nanoparticles.

PubMed

Stoiber, Tasha; Croteau, Marie-Noële; Römer, Isabella; Tejamaya, Mila; Lead, Jamie R; Luoma, Samuel N

2015-01-01

The release of Ag nanoparticles (AgNPs) into the aquatic environment is likely, but the influence of water chemistry on their impacts and fate remains unclear. Here, we characterize the bioavailability of Ag from AgNO(3) and from AgNPs capped with polyvinylpyrrolidone (PVP AgNP) and thiolated polyethylene glycol (PEG AgNP) in the freshwater snail, Lymnaea stagnalis, after short waterborne exposures. Results showed that water hardness, AgNP capping agents, and metal speciation affected the uptake rate of Ag from AgNPs. Comparison of the results from organisms of similar weight showed that water hardness affected the uptake of Ag from AgNPs, but not that from AgNO(3). Transformation (dissolution and aggregation) of the AgNPs was also influenced by water hardness and the capping agent. Bioavailability of Ag from AgNPs was, in turn, correlated to these physical changes. Water hardness increased the aggregation of AgNPs, especially for PEG AgNPs, reducing the bioavailability of Ag from PEG AgNPs to a greater degree than from PVP AgNPs. Higher dissolved Ag concentrations were measured for the PVP AgNPs (15%) compared to PEG AgNPs (3%) in moderately hard water, enhancing Ag bioavailability of the former. Multiple drivers of bioavailability yielded differences in Ag influx between very hard and deionized water where the uptake rate constants (k(uw), l g(-1) d(-1) ± SE) varied from 3.1 ± 0.7 to 0.2 ± 0.01 for PEG AgNPs and from 2.3 ± 0.02 to 1.3 ± 0.01 for PVP AgNPs. Modeling bioavailability of Ag from NPs revealed that Ag influx into L. stagnalis comprised uptake from the NPs themselves and from newly dissolved Ag.

Influence of hardness on the bioavailability of silver to a freshwater snail after waterborne exposure to silver nitrate and silver nanoparticles

USGS Publications Warehouse

Stoiber, Tasha L.; Croteau, Marie-Noele; Romer, Isabella; Tejamaya, Mila; Lead, Jamie R.; Luoma, Samuel N.

2015-01-01

The release of Ag nanoparticles (AgNPs) into the aquatic environment is likely, but the influence of water chemistry on their impacts and fate remains unclear. Here, we characterize the bioavailability of Ag from AgNO3 and from AgNPs capped with polyvinylpyrrolidone (PVP AgNP) and thiolated polyethylene glycol (PEG AgNP) in the freshwater snail, Lymnaea stagnalis, after short waterborne exposures. Results showed that water hardness, AgNP capping agents, and metal speciation affected the uptake rate of Ag from AgNPs. Comparison of the results from organisms of similar weight showed that water hardness affected the uptake of Ag from AgNPs, but not that from AgNO3. Transformation (dissolution and aggregation) of the AgNPs was also influenced by water hardness and the capping agent. Bioavailability of Ag from AgNPs was, in turn, correlated to these physical changes. Water hardness increased the aggregation of AgNPs, especially for PEG AgNPs, reducing the bioavailability of Ag from PEG AgNPs to a greater degree than from PVP AgNPs. Higher dissolved Ag concentrations were measured for the PVP AgNPs (15%) compared to PEG AgNPs (3%) in moderately hard water, enhancing Ag bioavailability of the former. Multiple drivers of bioavailability yielded differences in Ag influx between very hard and deionized water where the uptake rate constants (kuw, l g-1 d-1 ± SE) varied from 3.1 ± 0.7 to 0.2 ± 0.01 for PEG AgNPs and from 2.3 ± 0.02 to 1.3 ± 0.01 for PVP AgNPs. Modeling bioavailability of Ag from NPs revealed that Ag influx into L. stagnalis comprised uptake from the NPs themselves and from newly dissolved Ag.

Silver bioaccumulation dynamics in a freshwater invertebrate after aqueous and dietary exposures to nanosized and ionic Ag

USGS Publications Warehouse

le Croteau, Marie-Noe; Misra, Superb K.; Luoma, Samuel N.; Valsami-Jones, Eugenia

2011-01-01

We compared silver (Ag) bioavailability and toxicity to a freshwater gastropod after exposure to ionic silver (Ag+) and to Ag nanoparticles (Ag NPs) capped with citrate or with humic acid. Silver form, exposure route, and capping agent influence Ag bioaccumulation dynamics in Lymnaea stagnalis. Snails efficiently accumulated Ag from all forms after either aqueous or dietary exposure. For both exposure routes, uptake rates were faster for Ag+ than for Ag NPs. Snails efficiently assimilated Ag from Ag NPs mixed with diatoms (assimilation efficiency (AE) ranged from 49 to 58%) and from diatoms pre-exposed to Ag+ (AE of 73%). In the diet, Ag NPs damaged digestion. Snails ate less and inefficiently processed the ingested food, which adversely impacted their growth. Loss rates of Ag were faster after waterborne exposure to Ag NPs than after exposure to dissolved Ag+. Once Ag was taken up from diet, whether from Ag+ or Ag NPs, Ag was lost extremely slowly. Large Ag body concentrations are thus expected in L. stagnalis after dietborne exposures, especially to citrate-capped Ag NPs. Ingestion of Ag associated with particulate materials appears as the most important vector of uptake. Nanosilver exposure from food might trigger important environmental risks.

Cropping Systems and Cultural Practices Determine the Rhizoctonia Anastomosis Groups Associated with Brassica spp. in Vietnam

PubMed Central

Soltaninejad, Saman; Höfte, Monica

2014-01-01

Ninety seven Rhizoctonia isolates were collected from different Brassica species with typical Rhizoctonia symptoms in different provinces of Vietnam. The isolates were identified using staining of nuclei and sequencing of the rDNA-ITS barcoding gene. The majority of the isolates were multinucleate R. solani and four isolates were binucleate Rhizoctonia belonging to anastomosis groups (AGs) AG-A and a new subgroup of A-F that we introduce here as AG-Fc on the basis of differences in rDNA-ITS sequence. The most prevalent multinucleate AG was AG 1-IA (45.4% of isolates), followed by AG 1-ID (17.5%), AG 1-IB (13.4%), AG 4-HGI (12.4%), AG 2-2 (5.2%), AG 7 (1.0%) and an unknown AG related to AG 1-IA and AG 1-IE that we introduce here as AG 1-IG (1.0%) on the basis of differences in rDNA-ITS sequence. AG 1-IA and AG 1-ID have not been reported before on Brassica spp. Pathogenicity tests revealed that isolates from all AGs, except AG-A, induced symptoms on detached leaves of several cabbage species. In in vitro tests on white cabbage and Chinese cabbage, both hosts were severely infected by AG 1-IB, AG 2-2, AG 4-HGI, AG 1-IG and AG-Fc isolates, while under greenhouse conditions, only AG 4-HGI, AG 2-2 and AG-Fc isolates could cause severe disease symptoms. The occurrence of the different AGs seems to be correlated with the cropping systems and cultural practices in different sampling areas suggesting that agricultural practices determine the AGs associated with Brassica plants in Vietnam. PMID:25372406

In situ solid-state fabrication of hybrid AgCl/AgI/AgIO3 with improved UV-to-visible photocatalytic performance.

PubMed

Xie, Jing; Cao, Yali; Jia, Dianzeng; Li, Yizhao; Wang, Kun; Xu, Hui

2017-09-28

The AgCl/AgI/AgIO 3 composites were synthesized through a one-pot room-temperature in situ solid-state approach with the feature of convenient and eco-friendly. The as-prepared composites exhibit superior photocatalytic performance than pure AgIO 3 for the degradation of methyl orange (MO) under both UV and visible light irradiation. The photodegradation rate toward MO of the AgCl/AgI/AgIO 3 photocatalyst can reach 100% after 12 min irradiation under UV light, or 85.4% after 50 min irradiation under visible light, being significantly higher than AgCl, AgI, AgIO 3 and AgI/AgIO 3 . In addition, the AgCl/AgI/AgIO 3 photocatalyst possesses strong photooxidation ability for the degradation of rhodamine B (RhB), methylene blue (MB), phenol, bisphenol A (BPA) and tetracycline hydrochloride under visible light irradiation. The reactive species capture experiments confirmed that the h + and •O 2- play an essential role during the photocatalytic process under UV light or visible light irradiation. The enhanced effect may be beneficial from the enhanced light adsorption in full spectrum and increased separation efficiency of photogenerated hole-electron pairs, which can be ascribed to the synergistic effect among AgCl, AgI and AgIO 3 nanoplates in AgCl/AgI/AgIO 3 composites.

Comparative toxicity of silver nanoparticles and silver ions to Escherichia coli.

PubMed

Choi, Yoojin; Kim, Hyun-A; Kim, Kyoung-Woong; Lee, Byung-Tae

2018-04-01

With the increase in silver (Ag)-based products in our lives, it is essential to test the potential toxicity of silver nanoparticles (AgNPs) and silver ions (Ag ions) on living organisms under various conditions. Here, we investigated the toxicity of AgNPs with Ag ions to Escherichia coli K-12 strain under various conditions. We observed that both AgNPs and Ag ions display antibacterial activities, and that Ag ions had higher toxicity to E. coli K-12 strain than AgNPs under the same concentrations. To understand the toxicity of AgNPs at a cellular level, reactive oxygen species (ROS) enzymes were detected for use as antioxidant enzymatic biomarkers. We have also studied the toxicity of AgNPs and Ag ions under various coexistence conditions including: fixed total concentration, with a varied the ratio of AgNPs to Ag ions; fixed the AgNPs concentration and then increased the Ag ions concentration; fixed Ag ions concentration and then increasing the AgNPs concentration. Exposure to AgNPs and Ag ions clearly had synergistic toxicity; however, decreased toxicity (for a fixed AgNPs concentration of 5mg/L, after increasing the Ag ions concentration) to E. coli K-12 strain. AgNPs and Ag ions in the presence of L-cysteine accelerated the bacterial cell growth rate, thereby reducing the bioavailability of Ag ions released from AgNPs under the single and coexistence conditions. Further works are needed to consider this potential for AgNPs and Ag ions toxicity across a range of environmental conditions. As silver nanoparticles (AgNPs)-based products are being broadly used in commercial industries, an ecotoxicological understanding of the AgNPs being released into the environment should be further considered. Here, we investigate the comparative toxicity of AgNPs and silver ions (Ag ions) to Escherichia coli K-12 strain, a representative ecotoxicological bioreporter. This study showed that toxicities of AgNPs and Ag ions to E. coli K-12 strain display different relationships when existing individually or when coexisting, and in the presence of L-cysteine materials. These findings suggest that the toxicology research of nanomaterials should consider conditions when NPs coexist with and without their bioavailable ions. Copyright © 2017. Published by Elsevier B.V.

Digestive cell lysosomes as main targets for Ag accumulation and toxicity in marine mussels, Mytilus galloprovincialis, exposed to maltose-stabilised Ag nanoparticles of different sizes.

PubMed

Jimeno-Romero, A; Bilbao, E; Izagirre, U; Cajaraville, M P; Marigómez, I; Soto, M

2017-03-01

Bioavailability and toxicity of maltose-stabilised AgNPs of different sizes (20, 40 and 100 nm) in mussels were compared with bulk and aqueous forms of the metal through a two-tier experimental approach. In the first tier, mussels were exposed for 3 d to a range of concentrations (0.75, 75, 750 μg Ag/l) in the form of Ag20-Mal, Ag40-Mal, Ag100-Mal, bulk Ag and aqueous Ag (as AgNO 3 ), as well as to the concentrations of maltose used in the formulation of NPs. Mortality, bioaccumulation, tissue and cell distribution and lysosomal responses were investigated. In the second tier, mussels were exposed for 21 d to Ag20-Mal, Ag100-Mal, bulk Ag and aqueous Ag at the lowest effective concentration selected after Tier 1 (0.75 μg Ag/l), biomarkers and toxicopathic effects were investigated. Aqueous Ag was lethal within 3 d at 75 μg Ag/l; Ag NPs or bulk Ag did not produce significant mortality at 750 μg Ag/l. Ag accumulation was limited and metallothionein gene transcription was not regulated although metal accumulation occurred in digestive, brown and stomach epithelial cells and in gut lumen after exposure to AgNPs and aqueous Ag starting at low concentrations after 1 d. Electrondense particles (<10 nm) in lysosomes and residual bodies after exposure to AgNPs contained Ag and S (X-ray). Intralysosomal metal accumulation and lysosomal membrane destabilisation were enhanced after exposure to all the forms of Ag and more marked after exposure to Ag20-Mal than to larger NPs. 21 d exposure to AgNPs provoked digestive cell loss and loss of digestive gland integrity, resulting in atrophy-necrosis in digestive alveoli and oedema/hyperplasia in gills (Ag NP), vacuolisation in digestive cells (aqueous Ag) and haemocyte infiltration of connective tissue (all treatments). Intralysosomal metal accumulation, lysosomal responses and toxicopathic effects are enhanced at decreasing sizes and appear to be caused by Ag +  ions released from NPs, although the metal was not substantially accumulated.

Binary cobalt ferrite nanomesh arrays as the advanced binder-free electrode for applications in oxygen evolution reaction and supercapacitors

NASA Astrophysics Data System (ADS)

Liu, Li; Zhang, Huijuan; Mu, Yanping; Bai, Yuanjuan; Wang, Yu

2016-09-01

The porous CoFe2O4nanomesh arrays are successfully synthesized on nickel foam substrate through a high temperature and pressure hydrothermal method, following by the thermal post-treatment in air. The CoFe2O4 nanomesh arrays own numerous pores and large specific surface area, which is in favor of exposing more active sites. In consideration of the structural preponderances and versatility of the materials, the CoFe2O4 nanomesh arrays have been researched as the binder-free electrode materials for electrocatalysis and supercapacitors. When the CoFe2O4nanomesh arrays on nickel foam (CoFe2O4 NM-As/Ni) directly act as the free-binder catalyst toward catalyzing the oxygen evolution reaction (OER) of electrochemical water splitting, CoFe2O4 NM-As/Ni exhibits an admirable OER property with a low onset potential of 1.47 V(corresponding to the onset overpotential of 240 mV), a minimal overpotential (η10 = 253 mV), a small Tafel slope (44 mV dec-1), large anodic currents and long-term durability for 35 h in alkaline media. In addition, as an electrode of supercapacitors, CoFe2O4 NM-As/Ni obtains a desired specific capacitance (1426 F/g at the current density of 1 A/g), remarkable rate capability (1024 F/g at the current density of 20 A/g) and eminent capacitance retention (92.6% after 3000 cycles). The above results demonstrate the CoFe2O4 NM-As/Ni possesses great potential application in electrocatalysis and supercapacitors.

Results of LA-ICP-MS sulfide mapping from Algoma-type BIF gold systems with implications for the nature of mineralizing fluids, metal sources, and deposit models

NASA Astrophysics Data System (ADS)

Gourcerol, B.; Kontak, D. J.; Thurston, P. C.; Petrus, J. A.

2018-01-01

Quantitative laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) element distribution maps combined with traverse mode analyses have been acquired on various sulfides (pyrite, pyrrhotite, arsenopyrite) from three Canadian Algoma-type BIF-hosted gold deposits ( 4 Moz Au Meadowbank, ≥ 2.8 Moz Au Meliadine district, 6 Moz Au Musselwhite). These data, in conjunction with detailed petrographic and SEM-EDS observations, provide insight into the nature and relative timing of gold events, the presence and implication of trace element zoning regarding crystallization processes, and elemental associations that fingerprint gold events. Furthermore, the use of an innovative method of processing the LA-ICP-MS data in map and traverse modes, whereby the results are fragmented into time-slice data, to generate various binary plots (Ag versus Ni) provides a means to identify elemental associations (Te, Bi) not otherwise apparent. This integrated means of treating geochemical data, along with petrography, allows multiple gold events and remobilization processes to be recognized and their elemental associations determined. The main gold event in each of these deposits is characterized by the coupling of an As-Se-Te-Ag element association coincident with intense stratabound sulfide-replacement of the Fe-rich host rock. Additionally, the data indicate presence of a later remobilization event, which upgraded the Au tenor, as either non-refractory or refractory type, along fracture networks due to the ingress of subsequent base metal-bearing metamorphic fluids (mainly a Pb-Bi association). Furthermore, the data reveal a stratigraphic influence, as reflected in the elemental associations and the elemental enrichments observed and the nature of the sulfide phase hosting the gold mineralization (arsenopyrite versus pyrite).

A simple route to alloyed quaternary nanocrystals Ag-In-Zn-S with shape and size control.

PubMed

Gabka, Grzegorz; Bujak, Piotr; Giedyk, Kamila; Ostrowski, Andrzej; Malinowska, Karolina; Herbich, Jerzy; Golec, Barbara; Wielgus, Ireneusz; Pron, Adam

2014-05-19

A convenient method of the preparation of alloyed quaternary Ag-In-Zn-S nanocrystals is elaborated, in which a multicomponent mixture of simple and commercially available precursors, namely, silver nitrate, indium(III) chloride, zinc stearate, 1-dodecanethiol, and sulfur, is used with 1-octadecene as a solvent. The formation of quaternary nanocrystals necessitates the use of an auxiliary sulfur precursor, namely, elemental sulfur dissolved in oleylamine, in addition to 1-dodecanethiol. Without this additional precursor binary ZnS nanocrystals are formed. The optimum reaction temperature of 180 °C was also established. In these conditions shape, size, and composition of the resulting nanocrystals can be adjusted in a controlled manner by changing the molar ratio of the precursors in the reaction mixture. For low zinc stearate contents anisotropic rodlike (ca.3 nm x 10 nm) and In-rich nanocrystals are obtained. This is caused by a significantly higher reactivity of the indium precursor as compared to the zinc one. With increasing zinc precursor content the reactivities of both precursors become more balanced, and the resulting nanocrystals are smaller (1.5-4.0 nm) and become Zn-rich as evidenced by transmission electron microscopy, X-ray diffraction, and energy-dispersive spectrometry investigations. Simultaneous increases in the zinc and sulfur precursor content result in an enlargement of nanocrystals (2.5 to 5.0 nm) and further increase in the molar ZnS content (up to 0.76). The prepared nanoparticles show stable photoluminescence with the quantum yield up to 37% for In and Zn-rich nanocrystals. Their hydrodynamic diameter in toluene dispersion, determined by dynamic light scattering, is roughly twice larger than the diameter of their inorganic core.

Preparation and antibacterial activities of Ag/Ag+/Ag3+ nanoparticle composites made by pomegranate (Punica granatum) rind extract

NASA Astrophysics Data System (ADS)

Yang, Hui; Ren, Yan-yu; Wang, Tao; Wang, Chuang

Nano-silver and its composite materials are widely used in medicine, food and other industries due to their strong conductivity, size effect and other special performances. So far, more microbial researches have been applied, but a plant method is rarely reported. In order to open up a new way to prepare AgNP composites, pomegranate peel extract was used in this work to reduce Ag+ to prepare Ag/Ag+/Ag3+ nanoparticle composites. UV-Vis was employed to detect and track the reduction of Ag+ and the forming process of AgNPs. The composition, structure and size of the crystal were analyzed by XRD and TEM. Results showed that, under mild conditions, pomegranate peel extract reacted with dilute AgNO3 solution to produce Ag/Ag+/Ag3+ nanoparticle composites. At pH = 8 and 10 mmol/L of AgNO3 concentration, the size of the achieved composites ranged between 15 and 35 nm with spherical shapes and good crystallinity. The bactericidal experiment indicated that the prepared Ag/Ag+/Ag3+ nanoparticles had strong antibacterial activity against gram positive bacteria and gram negative bacteria. FTIR analysis revealed that biological macromolecules with groups of sbnd NH2, sbnd OH, and others were distributed on the surface of the newly synthesized Ag/Ag+/Ag3+ nanoparticles. This provided a useful clue to further study the AgNP biosynthesis mechanism.

Thermochemical properties of silver tellurides including empressite (AgTe) and phase diagrams for Ag-Te and Ag-Te-O

NASA Astrophysics Data System (ADS)

Voronin, Mikhail V.; Osadchii, Evgeniy G.; Brichkina, Ekaterina A.

2017-10-01

This study compiles original experimental and literature data on the thermodynamic properties (ΔfG°, S°, ΔfH°) of silver tellurides (α-Ag2Te, β-Ag2Te, Ag1.9Te, Ag5Te3, AgTe) obtained by the method of solid-state galvanic cell with the RbAg4I5 and AgI solid electrolytes. The thermodynamic data for empressite (AgTe, pure fraction from Empress Josephine Mine, Colorado USA) have been obtained for the first time by the electrochemical experiment with the virtual reaction Ag + Te = AgTe. The Ag-Te phase diagrams in the T - x and log fTe2 (gas) - 1/ T coordinates have been refined, and the ternary Ag-Te-O diagrams with Ag-Te-TeO2 (paratellurite) composition range have been calculated.

Effect of nano/micro-Ag compound particles on the bio-corrosion, antibacterial properties and cell biocompatibility of Ti-Ag alloys.

PubMed

Chen, Mian; Yang, Lei; Zhang, Lan; Han, Yong; Lu, Zheng; Qin, Gaowu; Zhang, Erlin

2017-06-01

In this research, Ti-Ag alloys were prepared by powder metallurgy, casting and heat treatment method in order to investigate the effect of Ag compound particles on the bio-corrosion, the antibacterial property and the cell biocompatibility. Ti-Ag alloys with different sizes of Ag or Ag-compounds particles were successfully prepared: small amount of submicro-scale (100nm) Ti 2 Ag precipitates with solid solution state of Ag, large amount of nano-scale (20-30nm) Ti 2 Ag precipitates with small amount of solid solution state of Ag and micro-scale lamellar Ti 2 Ag phases, and complete solid solution state of Ag. The mechanical tests indicated that both nano/micro-scale Ti 2 Ag phases had a strong dispersion strengthening ability and Ag had a high solid solution strengthening ability. Electrochemical results shown the Ag content and the size of Ag particles had a limited influence on the bio-corrosion resistance although nano-scale Ti 2 Ag precipitates slightly improved corrosion resistance. It was demonstrated that the nano Ag compounds precipitates have a significant influence on the antibacterial properties of Ti-Ag alloys but no effect on the cell biocompatibility. It was thought that both Ag ions release and Ti 2 Ag precipitates contributed to the antibacterial ability, in which nano-scale and homogeneously distributed Ti 2 Ag phases would play a key role in antibacterial process. Copyright © 2017 Elsevier B.V. All rights reserved.

Bioavailability of silver and silver sulfide nanoparticles to lettuce (Lactuca sativa): Effect of agricultural amendments on plant uptake.

PubMed

Doolette, Casey L; McLaughlin, Michael J; Kirby, Jason K; Navarro, Divina A

2015-12-30

Silver nanoparticles (AgNPs) can enter terrestrial systems as sulfidised AgNPs (Ag2S-NPs) through the application of biosolids to soil. However, the bioavailability of Ag2S-NPs in soils is unknown. The two aims of this study were to investigate (1) the bioavailability of Ag to lettuce (Lactuca sativa) using a soil amended with biosolids containing Ag2S-NPs and (2) the effect of commonly used agricultural fertilisers/amendments on the bioavailability of Ag, AgNPs and Ag2S-NPs to lettuce. The study used realistic AgNP exposure pathways and exposure concentrations. The plant uptake of Ag from biosolids-amended soil containing Ag2S-NPs was very low for all Ag treatments (0.02%). Ammonium thiosulfate and potassium chloride fertilisation significantly increased the Ag concentrations of plant roots and shoots. The extent of the effect varied depending on the type of Ag. Ag2S-NPs, the realistic form of AgNPs in soil, had the lowest bioavailability. The potential risk of AgNPs in soils is low; even in the plants that had the highest Ag concentrations (Ag(+)+thiosulfate), only 0.06% of added Ag was found in edible plant parts (shoots). Results from the study suggest that agricultural practises must be considered when carrying out risk assessments of AgNPs in terrestrial systems; such practises can affect AgNP bioavailability. Copyright © 2015 Elsevier B.V. All rights reserved.

Visible light driven photocatalysis and antibacterial activity of AgVO{sub 3} and Ag/AgVO{sub 3} nanowires

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

Singh, Anamika; Dutta, Dimple P., E-mail: dimpled@barc.gov.in; Ballal, A.

Graphical abstract: - Highlights: • Ag/AgVO{sub 3} and pure AgVO{sub 3} nanowires synthesized by sonochemical process. • Characterization done using XRD, SEM, TEM, EDX and BET analysis. • Visible light degradation of RhB by Ag/AgVO{sub 3} within 45 min. • Antibacterial activity of Ag/AgVO{sub 3} demonstrated. - Abstract: Ag/AgVO{sub 3} nanowires and AgVO{sub 3} nanorods were synthesized in aqueous media via a facile sonochemical route. The as-synthesized products were characterized by X-ray diffraction, Brunauer–Emmett–Teller surface area analysis, scanning electron microscopy together with an energy dispersion X-ray spectrum analysis, transmission electron microscopy and UV–vis diffuse reflectance spectroscopy. The results revealed thatmore » inert atmosphere promotes the formation of Ag/AgVO{sub 3} nanowires. The photocatalytic studies revealed that the Ag/AgVO{sub 3} nanowires exhibited complete photocatalytic degradation of Rhodamine B within 45 min under visible light irradiation. The antibacterial activity of Ag/AgVO{sub 3} nanowires was tested against Escherechia coli and Bacillus subtilis. The minimum growth inhibitory concentration value was found to be 50 and 10 folds lower than for the antibiotic ciprofloxacin for E. coli and B. subtilis, respectively. The antibacterial properties of the β-AgVO{sub 3} nanorods prove that in case of the Ag dispersed Ag/AgVO{sub 3} nanowires, the enhanced antibacterial action is also due to contribution from the AgVO{sub 3} support.« less

One-pot synthesis of ternary Ag₂CO₃/Ag/AgCl photocatalyst in natural geothermal water with enhanced photocatalytic activity under visible light irradiation.

PubMed

Yao, Xiaxi; Liu, Xiaoheng

2014-09-15

Geothermal water is a clean, cheap and renewable resource and it is widely distributed all over the world. In this work, ternary Ag2CO3/Ag/AgCl photocatalyst has been successfully synthesized via a one-pot precipitation method in natural geothermal water at room temperature, wherein the geothermal water serves as the source of chlorine and carbonate. The results suggest that the Ag/AgCl nanoparticles are anchored on the surface of Ag2CO3 and Ag2CO3/Ag/AgCl composite shows strong absorption ability in the visible light region. The evaluation of the photocatalytic activity indicates that the as-synthesized Ag2CO3/Ag/AgCl photocatalyst exhibits higher photocatalytic performance for the degradation of methylene blue (MB) aqueous solution under visible light irradiation than one-component (Ag2CO3), two-component (Ag/AgCl, Ag2CO3/AgCl) and the mechanical mixture of Ag2CO3 and Ag/AgCl. The trapping experiments confirmed that holes (h(+)) and (•)O2(-) were the two main active species in the photocatalytic process. Finally, a possible Z-scheme photocatalytic mechanism of the charge transfer was proposed for the enhanced photocatalytic performance. This work may open up new insights into the application of cheap geothermal water resources in the word and provide new opportunities for facile fabrication of Ag/AgCl-based photocatalysts. Copyright © 2014 Elsevier B.V. All rights reserved.

In Vitro Parallel Evaluation of Antibacterial Activity and Cytotoxicity of Commercially Available Silver-Containing Wound Dressings.

PubMed

Yunoki, Shunji; Kohta, Masushi; Ohyabu, Yoshimi; Iwasaki, Tetsuji

2015-01-01

This study evaluated the in vitro antibacterial activity and cytotoxicity of various commercially available silver-containing dressings (Ag dressing). Biohesive Ag (hydrocolloid, silver sulfadiazine), Aquacel® Ag (nonwoven fabric, ionic silver [Ag]), Algisite™ Ag (nonwoven fabric, Ag), Mepilex® Ag (foam, silver sulfate), and PolyMem® Ag (foam, nanocrystalline silver) were tested for characteristics of Ag release, antibacterial activity, and cytotoxicity. The release of Ag was investigated in cell culture medium at immersion periods of 6, 24, and 48 hours. The antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa were accessed by a disc diffusion test. The cytotoxicity was evaluated using V79 cells, by an extraction method. The cytotoxicity was not a monotonic function of the antibacterial activity among the Ag dressings and could not be simply explained by Ag-release properties. Biohesive Ag was regarded as a slow-release Ag dressing, showing the lowest cytotoxicity, while the antibacterial activity was classified as "strong" or "significant" against the two species of bacteria. Aquacel Ag and Algisite Ag showed higher antibacterial activity and cytotoxic effects, which were supported by the higher Ag release. Mepilex Ag showed the highest release of Ag, and the cytotoxicity was the highest among the Ag dressings. However, the antibacterial activity was classified as "significant" or "no activity" for P. aeruginosa and S. aureus, respectively. PolyMem Ag showed the lowest Ag release, and the antibacterial activity classified as "significant" or "no activity" for S. aureus and P. aeruginosa, respectively, whereas the cytotoxicity was similar to those of Aquacel Ag and Algisite Ag. The efficacy and adverse effects of the Ag dressings revealed differences that should be considered by clinicians during wound management.

Enhanced Visible Light Photocatalytic Degradation of Organic Pollutants over Flower-Like Bi₂O₂CO₃ Dotted with Ag@AgBr.

PubMed

Lin, Shuanglong; Wang, Miao; Liu, Li; Liang, Yinghua; Cui, Wenquan; Zhang, Zisheng; Yun, Nan

2016-10-31

A facile and feasible oil-in-water self-assembly approach was developed to synthesize flower-like Ag@AgBr/Bi₂O₂CO₃ micro-composites. The photocatalytic activities of the samples were evaluated through methylene blue degradation under visible light irradiation. Compared to Bi₂O₂CO₃, flower-like Ag@AgBr/Bi₂O₂CO₃ micro-composites show enhanced photocatalytic activities. In addition, results indicate that both the physicochemical properties and associated photocatalytic activities of Ag@AgBr/Bi₂O₂CO₃ composites are shown to be dependent on the loading quantity of Ag@AgBr. The highest photocatalytic performance was achieved at 7 wt % Ag@AgBr, degrading 95.18% methylene blue (MB) after 20 min of irradiation, which is over 1.52 and 3.56 times more efficient than that of pure Ag@AgBr and pure Bi₂O₂CO₃, respectively. Bisphenol A (BPA) was also degraded to further demonstrate the degradation ability of Ag@AgBr/Bi₂O₂CO₃. A photocatalytic mechanism for the degradation of organic compounds over Ag@AgBr/Bi₂O₂CO₃ was proposed. Results from this study illustrate an entirely new approach to fabricate semiconductor composites containing Ag@AgX/bismuth (X = a halogen).

A m-ary linear feedback shift register with binary logic

NASA Technical Reports Server (NTRS)

Perlman, M. (Inventor)

1973-01-01

A family of m-ary linear feedback shift registers with binary logic is disclosed. Each m-ary linear feedback shift register with binary logic generates a binary representation of a nonbinary recurring sequence, producible with a m-ary linear feedback shift register without binary logic in which m is greater than 2. The state table of a m-ary linear feedback shift register without binary logic, utilizing sum modulo m feedback, is first tubulated for a given initial state. The entries in the state table are coded in binary and the binary entries are used to set the initial states of the stages of a plurality of binary shift registers. A single feedback logic unit is employed which provides a separate feedback binary digit to each binary register as a function of the states of corresponding stages of the binary registers.

Uptake and Distribution of Silver in the Aquatic Plant Landoltia punctata (Duckweed) Exposed to Silver and Silver Sulfide Nanoparticles.

PubMed

Stegemeier, John P; Colman, Benjamin P; Schwab, Fabienne; Wiesner, Mark R; Lowry, Gregory V

2017-05-02

Aquatic ecosystems are expected to receive Ag 0 and Ag 2 S nanoparticles (NPs) through anthropogenic waste streams. The speciation of silver in Ag-NPs affects their fate in ecosystems, but its influence on interactions with aquatic plants is still unclear. Here, the Ag speciation and distribution was measured in an aquatic plant, duckweed (Landoltia punctata), exposed to Ag 0 or Ag 2 S NPs, or to AgNO 3 . The silver distribution in duckweed roots was visualized using synchrotron-based micro X-ray fluorescence (XRF) mapping and Ag speciation was determined using extended X-ray absorption fine structure (EXAFS) spectroscopy. Duckweed exposed to Ag 2 S-NPs or Ag 0 -NPs accumulated similar Ag concentrations despite an order of magnitude smaller dissolved Ag fraction measured in the exposure medium for Ag 2 S-NPs compared to Ag 0 -NPs. By 24 h after exposure, all three forms of silver had accumulated on and partially in the roots regardless of the form of Ag exposed to the plants. Once associated with duckweed tissue, Ag 0 -NPs had transformed primarily into silver sulfide and silver thiol species. This suggests that plant defenses were active within or at the root surface. The Ag 2 S-NPs remained as Ag 2 S, while AgNO 3 exposure led to Ag 0 and sulfur-associated Ag species in plant tissue. Thus, regardless of initial speciation, Ag was readily available to duckweed.

AgCl/Ag3PO4: A stable Ag-Based nanocomposite photocatalyst with enhanced photocatalytic activity for the degradation of parabens.

PubMed

Guo, Jianhao; Shi, Huixian; Huang, Xiaobo; Shi, Huifang; An, Zhongfu

2018-04-01

An AgCl/Ag 3 PO 4 composite has been successfully fabricated by a simple desorption-precipitation method. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible spectroscopy (UV/Vis), and photoluminescence (PL) have been used to study the structural and physicochemical characteristics of the AgCl/Ag 3 PO 4 composite. The photocatalytic activity of the AgCl/Ag 3 PO 4 composite has been tested by the degradation of parabens under visible-light irradiation. 100% of MPB was degraded within 40 min in the AgCl/Ag 3 PO 4 -visible light system. Moreover, the photocatalytic activity of AgCl/Ag 3 PO 4 remained at 94% of the original level after five runs, which was much higher than that of pure Ag 3 PO 4 (25%). The obtained results confirmed that the AgCl/Ag 3 PO 4 composite exhibited significantly higher photocatalytic performance and improved stability compared with bare Ag 3 PO 4 . The enhanced photocatalytic performance of the AgCl/Ag 3 PO 4 composite could be mainly attributed to highly efficient charge separation through a synergistic effect of AgCl, Ag 3 PO 4 , and in situ photo-reduced Ag nanoparticles. Trapping experiments confirmed h + and ·O 2 - to be the two main active species in the photocatalytic process. Finally, a possible photocatalytic mechanism for the charge-transfer process is proposed to account for the enhanced photocatalytic performance of the AgCl/Ag 3 PO 4 composite. Copyright © 2018 Elsevier Inc. All rights reserved.

Ag-bridged Ag2O nanowire network/TiO2 nanotube array p-n heterojunction as a highly efficient and stable visible light photocatalyst.

PubMed

Liu, Chengbin; Cao, Chenghao; Luo, Xubiao; Luo, Shenglian

2015-03-21

A unique Ag-bridged Ag2O nanowire network/TiO2 nanotube array p-n heterojunction (Ag-Ag2O/TiO2 NT) was fabricated by simple electrochemical method. Ag nanoparticles were firstly electrochemically deposited onto the surface of TiO2 NT and then were partly oxidized to Ag2O nanowires while the rest of Ag mother nanoparticles were located at the junctions of Ag2O nanowire network. The Ag-Ag2O/TiO2 NT heterostructure exhibited strong visible-light response, effective separation of photogenerated carriers, and high adsorption capacity. The integration of Ag-Ag2O self-stability structure and p-n heterojunction permitted high and stable photocatalytic activity of Ag-Ag2O/TiO2 NT heterostructure photocatalyst. Under 140-min visible light irradiation, the photocatalytic removal efficiency of both dye acid orange 7 (AO7) and industrial chemical p-nitrophenol (PNP) over Ag-Ag2O/TiO2 NT reached nearly 100% much higher than 17% for AO7 or 13% for PNP over bare TiO2 NT. After 5 successive cycles under 600-min simulated solar light irradiation, Ag-Ag2O/TiO2 NT remained highly stable photocatalytic activity. Copyright © 2014 Elsevier B.V. All rights reserved.

Characterization of the intermediate-range order in new superionic conducting AgI-Ag2S-AgPO3 glasses by neutron diffraction

NASA Astrophysics Data System (ADS)

Kartini, E.; Kennedy, S. J.; Itoh, K.; Fukunaga, T.; Suminta, S.; Kamiyama, T.

Superionic conducting glasses are of considerable technological interest because of their use in batteries, sensors, and displays. We have investigated the new ternary systems AgI-Ag2S-AgPO3 where the ratio AgI:Ag2S is 1:1. The system (AgI)x(Ag2S)x(AgPO3)1-2x, for a AgI+Ag2S fraction less than 82mol%, yields glasses. We have used a neutron-diffraction technique to obtain the total scattering structure factor S(Q) of this system at room temperature by using the HIT spectrometer at the High Energy Accelerator (KEK), Tsukuba, Japan. As for AgI-AgPO3 glasses, S(Q) shows a peak at anomalously low Q in the range from 0.6 to 0.9 Å-1. This peak is not observed in the corresponding glass Ag2S-AgPO3 or pure AgPO3. The peak depends strongly on the dopant salt. Its intensity increases as the amount of (AgI+Ag2S) increases and its position shifts to lower Q, while the number density of the glasses decreases with x. This peak can be associated with an intermediate structure of particles lying inside a continuous host with the characteristic length between 5 and 10 Å [1].

Enhanced Visible Light Photocatalytic Degradation of Organic Pollutants over Flower-Like Bi2O2CO3 Dotted with Ag@AgBr

PubMed Central

Lin, Shuanglong; Wang, Miao; Liu, Li; Liang, Yinghua; Cui, Wenquan; Zhang, Zisheng; Yun, Nan

2016-01-01

A facile and feasible oil-in-water self-assembly approach was developed to synthesize flower-like Ag@AgBr/Bi2O2CO3 micro-composites. The photocatalytic activities of the samples were evaluated through methylene blue degradation under visible light irradiation. Compared to Bi2O2CO3, flower-like Ag@AgBr/Bi2O2CO3 micro-composites show enhanced photocatalytic activities. In addition, results indicate that both the physicochemical properties and associated photocatalytic activities of Ag@AgBr/Bi2O2CO3 composites are shown to be dependent on the loading quantity of Ag@AgBr. The highest photocatalytic performance was achieved at 7 wt % Ag@AgBr, degrading 95.18% methylene blue (MB) after 20 min of irradiation, which is over 1.52 and 3.56 times more efficient than that of pure Ag@AgBr and pure Bi2O2CO3, respectively. Bisphenol A (BPA) was also degraded to further demonstrate the degradation ability of Ag@AgBr/Bi2O2CO3. A photocatalytic mechanism for the degradation of organic compounds over Ag@AgBr/Bi2O2CO3 was proposed. Results from this study illustrate an entirely new approach to fabricate semiconductor composites containing Ag@AgX/bismuth (X = a halogen). PMID:28774002

Enhanced positron trapping by Ag nanoclusters at low temperatures: A challenge of positron sensitivity to quantum dots

NASA Astrophysics Data System (ADS)

Zou, B.; Qi, N.; Liu, Z. W.; Chen, Z. Q.; Liu, H. Q.; Yi, D. Q.; Tang, Z.

2017-03-01

Microstructure evolution of three Al-Ag alloys with different Ag contents (1 wt. % Ag, 5 wt. % Ag, and 15 wt. % Ag) was studied by positron annihilation spectroscopy during the aging process. In situ measurements of the positron lifetime and Doppler broadening of annihilation radiation indicate the fast formation of Ag-rich clusters during natural aging of the alloys. The formation of Ag-rich clusters was further confirmed by coincidence Doppler broadening measurements. The Ag signal reflected by the Coincidence Doppler broadening spectrum increases with increasing Ag content and is further enhanced after subsequent artificial aging at 140 °C. This might be due to the increase in the size of Ag clusters. The temperature dependence of the Doppler broadening spectra between 10 K and 290 K was measured for the Al-Ag alloys after natural and artificial aging. Detrapping of positrons from Ag clusters with increasing temperature was observed for all the three Al-Ag alloys after natural aging and for the Al-1 wt. % Ag after artificial aging. This indicates that Ag clusters act as shallow positron trapping centers. The thermal detrapping of positrons becomes ambiguous with increasing Ag content in the alloy and is nearly invisible in the artificially aged Al-5 wt. % Ag and Al-15 wt. % Ag. The positron binding energy of the Ag cluster is roughly estimated to be about 18.8 meV and 50 meV in the Al-1 wt. % Ag sample after natural aging and artificial aging at 140 °C, respectively, which suggests that the confinement of positrons in the quantum-dot like state depends on the size or chemical composition of clusters. Theoretical calculations confirm positron trapping by Ag nanoclusters, and the confinement of positrons is enhanced with increasing Ag cluster size.

Silver nanoparticles: in vivo toxicity in zebrafish embryos and a comparison to silver nitrate

NASA Astrophysics Data System (ADS)

Mosselhy, Dina A.; He, Wei; Li, Dan; Meng, Yaping; Feng, Qingling

2016-08-01

The wide antimicrobial administration of silver nanoparticles (AgNPs) has raised the risks associated with their exposure. However, there is lack of robust toxicological data for the applied AgNPs to be in line with their wide antimicrobial applications. This study therefore set out to assess the in vivo toxicity of two different sizes of AgNPs using zebrafish embryos ( Danio rerio) as a brilliant in vivo model. The pivotal role of size of AgNPs in the toxicity was highlighted, wherein the smaller AgNPs (Ag-9 nm) exhibited more embryo toxicities than the larger particles (Ag-30 nm). Much uncertainty still exists about whether the cause of in vivo toxicity of AgNPs is the physicochemical properties of AgNPs or the released silver ions (Ag+). Therefore, another purpose of this study is to compare the toxicity of AgNPs with silver nitrate (AgNO3) in terms of mortality, hatchability and cardiac rates, and a series of phenotypic endpoints of zebrafish embryos. Collectively, the present results point towards the remarkable size-dependent toxicity of AgNPs. Wherein, the smaller AgNPs (9 ± 2 nm) induce increased mortality rates and decreased hatchability rates than the larger particles (30 ± 5 nm) in a dose-dependent manner. Besides, AgNPs and AgNO3 induce holistic different toxic mortality and hatchability rates. We have also found striking discrepancies in the phenotypic defects that were induced by AgNPs and AgNO3. The significant phenotypic defect induced by AgNPs is the axial deformity, while it is the deposition of Ag+ on the embryonic chorion for AgNO3. Therefore, it is proposed that AgNPs and AgNO3 induce different in vivo toxicities.

Transformation-Dissolution Reactions Partially Explain Adverse Effects of Metallic Silver Nanoparticles to Soil Nitrification in Different Soils.

PubMed

Bollyn, Jessica; Willaert, Bernd; Kerré, Bart; Moens, Claudia; Arijs, Katrien; Mertens, Jelle; Leverett, Dean; Oorts, Koen; Smolders, Erik

2018-04-25

Risk assessment of metallic nanoparticles (NP) is critically affected by the concern that toxicity goes beyond that of the metallic ion. This study addressed this concern for soils with silver (Ag)-NP using the Ag-sensitive nitrification assay. Three agricultural soils (A,B,C) were spiked with equivalent Ag doses of either Ag-NP (d = 13 nm) or AgNO 3 . Soil solution was isolated and monitored over 97 days with due attention to accurate Ag fractionation at low (∼10 µg L -1 ) Ag concentrations. Truly dissolved (<1 kDa) Ag in the AgNO 3 -amended soils decreased with reaction half-lives of 4 to 22 days depending on the soil, denoting important Ag-ageing reactions. In contrast, truly dissolved Ag in Ag-NP-amended soils first increased by dissolution and subsequently decreased by ageing; the concentration never exceeding that in the AgNO 3 -amended soils. The half-lives of Ag-NP transformation-dissolution were about 4 days (soils A&B) and 36 days (soil C). The Ag toxic thresholds (EC10, mg Ag kg -1 soil) of nitrification, either evaluated at 21 or 35 days after spiking, were similar between the two Ag forms (soils A&B) but were factors 3 to 8 lower for AgNO 3 than for Ag-NP (soil C), largely corroborating with dissolution differences. This fate and bio-assay showed that Ag-NPs are not more toxic than AgNO 3 at equivalent total soil Ag concentrations and that differences in Ag-dissolution at least partially explain toxicity differences between the forms and among soils. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Strong and multi-antigen specific immunity by hepatitis B core antigen (HBcAg)-based vaccines in a murine model of chronic hepatitis B: HBcAg is a candidate for a therapeutic vaccine against hepatitis B virus.

PubMed

Akbar, Sheikh Mohammad Fazle; Chen, Shiyi; Al-Mahtab, Mamun; Abe, Masanori; Hiasa, Yoichi; Onji, Morikazu

2012-10-01

Experimental evidence suggests that hepatitis B core antigen (HBcAg)-specific cytotoxic T lymphocytes (CTL) are essential for the control of hepatitis B virus (HBV) replication and prevention of liver damage in patients with chronic hepatitis B (CHB). However, most immune therapeutic approaches in CHB patients have been accomplished with hepatitis B surface antigen (HBsAg)-based prophylactic vaccines with unsatisfactory clinical outcomes. In this study, we prepared HBsAg-pulsed dendritic cells (DC) and HBcAg-pulsed DC by culturing spleen DC from HBV transgenic mice (HBV TM) and evaluated the immunomodulatory capabilities of these antigens, which may serve as a better therapy for CHB. The kinetics of HBsAg, antibody levels against HBsAg (anti-HBs), proliferation of HBsAg- and HBcAg-specific lymphocytes, production of antigen-specific CTL, and activation of endogenous DC were compared between HBV TM vaccinated with either HBsAg- or HBcAg-pulsed DC. Vaccination with HBsAg-pulsed DC induced HBsAg-specific immunity, but failed to induce HBcAg-specific immunity in HBV TM. However, immunization of HBV TM with HBcAg-pulsed DC resulted in: (1) HBsAg negativity, (2) production of anti-HBs, and (3) development of HBsAg- and HBcAg-specific T cells and CTL in the spleen and the liver. Additionally, significantly higher levels of activated endogenous DC were detected in HBV TM immunized with HBcAg-pulsed DC compared to HBsAg-pulsed DC (p<0.05). The capacity of HBcAg to modulate both HBsAg- and HBcAg-specific immunity in HBV TM, and activation of endogenous DC in HBV TM without inducing liver damage suggests that HBcAg should be an integral component of the therapeutic vaccine against CHB. Copyright © 2012 Elsevier B.V. All rights reserved.

Clinical implications of hepatitis B surface antigen quantitation in the natural history of chronic hepatitis B virus infection.

PubMed

Tan, Zhaoxia; Li, Maoshi; Kuang, Xuemei; Tang, Yu; Fan, Yi; Deng, Guohong; Wang, Yuming; He, Dengming

2014-04-01

HBsAg quantitation may be useful for managing patients with hepatitis B virus (HBV) infection. We explored the clinical implications of HBsAg quantitation for patients with HBsAg levels >250IU/ml (Abbott Diagnostics). Two hundred and thirty-three HBV-infected patients comprising 29 immune tolerance cases, 49 treatment-naïve HBeAg-positive chronic hepatitis B (CHB) cases, 91 inactive HBV carrier cases, and 64 treatment-naïve HBeAg-negative CHB cases were analyzed. HBsAg was quantified by the Architect HBsAg assay (Abbott Diagnostics) after a 1:500 automated dilution. HBsAg (log10IU/ml) was established for immune tolerance (4.50±0.43), HBeAg-positive CHB (4.17±0.66), inactive HBV carrier (3.32±0.44), and HBeAg-negative CHB (3.23±0.40); (p=4.92×10(-35)). No significant difference was observed between inactive HBV carrier and HBeAg-negative CHB (p=0.247). The proportions of HBsAg <2000IU/ml for inactive HBV carrier and HBeAg-negative CHB were 51.6% and 59.3%, respectively (p=0.341). Positive correlations between HBsAg and HBV DNA were observed for immune tolerance (p=1.23×10(-4)) and HBeAg-positive CHB (p=0.003), but not for HBeAg-negative CHB (p=0.432). A negative correlation between HBsAg and age was observed for immune tolerance (p=0.030), HBeAg-positive CHB (p=0.016), and inactive HBV carrier (p=0.001), but not in HBeAg-negative CHB (p=0.249). No significant differences between HBsAg and ALT for HBeAg-positive (p=0.338) or HBeAg-negative CHB (p=0.564) were observed. For patients with HBsAg quantitation >250IU/ml, HBsAg may reflect HBV DNA replication for HBeAg-positive cases. HBsAg is not a suitable marker for evaluating hepatitis activity and distinguishing between cases of HBeAg-negative CHB and inactive HBV carrier state. Copyright © 2014 Elsevier B.V. All rights reserved.

Nano-volcanic Eruption of Silver

NASA Astrophysics Data System (ADS)

Lin, Shih-Kang; Nagao, Shijo; Yokoi, Emi; Oh, Chulmin; Zhang, Hao; Liu, Yu-Chen; Lin, Shih-Guei; Suganuma, Katsuaki

2016-10-01

Silver (Ag) is one of the seven metals of antiquity and an important engineering material in the electronic, medical, and chemical industries because of its unique noble and catalytic properties. Ag thin films are extensively used in modern electronics primarily because of their oxidation-resistance. Here we report a novel phenomenon of Ag nano-volcanic eruption that is caused by interactions between Ag and oxygen (O). It involves grain boundary liquation, the ejection of transient Ag-O fluids through grain boundaries, and the decomposition of Ag-O fluids into O2 gas and suspended Ag and Ag2O clusters. Subsequent coating with re-deposited Ag-O and the de-alloying of O yield a conformal amorphous Ag coating. Patterned Ag hillock arrays and direct Ag-to-Ag bonding can be formed by the homogenous crystallization of amorphous coatings. The Ag “nano-volcanic eruption” mechanism is elaborated, shedding light on a new mechanism of hillock formation and new applications of amorphous Ag coatings.

Nano-volcanic Eruption of Silver.

PubMed

Lin, Shih-Kang; Nagao, Shijo; Yokoi, Emi; Oh, Chulmin; Zhang, Hao; Liu, Yu-Chen; Lin, Shih-Guei; Suganuma, Katsuaki

2016-10-05

Silver (Ag) is one of the seven metals of antiquity and an important engineering material in the electronic, medical, and chemical industries because of its unique noble and catalytic properties. Ag thin films are extensively used in modern electronics primarily because of their oxidation-resistance. Here we report a novel phenomenon of Ag nano-volcanic eruption that is caused by interactions between Ag and oxygen (O). It involves grain boundary liquation, the ejection of transient Ag-O fluids through grain boundaries, and the decomposition of Ag-O fluids into O 2 gas and suspended Ag and Ag 2 O clusters. Subsequent coating with re-deposited Ag-O and the de-alloying of O yield a conformal amorphous Ag coating. Patterned Ag hillock arrays and direct Ag-to-Ag bonding can be formed by the homogenous crystallization of amorphous coatings. The Ag "nano-volcanic eruption" mechanism is elaborated, shedding light on a new mechanism of hillock formation and new applications of amorphous Ag coatings.

Template synthesis of Ag/AgCl microrods and their efficient visible light-driven photocatalytic performance

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

Chen, Hua; Xiao, Liang; Huang, Jianhua, E-mail: jhhuang@zstu.edu.cn

2014-09-15

Highlights: • Preparation ofAg/AgCl microrods by reaction of Ag{sub 2}WO{sub 4} microrods with NaCl solution. • Generation of metallic Ag is induced by the ambient light in the synthesis process. • Ag/AgCl shows excellent visible light-driven photodegradation of organic dyes. - Abstract: Ag/AgCl microrods, aggregated by nanoparticles with a diameter ranging from 100 nm to 2 μm, were prepared by an ion-exchange reaction at 80 °C between Ag{sub 2}WO{sub 4} template and NaCl solution. The existence of metallic Ag species was confirmed by XRD, DRS and XPS measurements. Ag/AgCl microrods showed excellent photocatalytic activity for the degradation of rhodamine Bmore » and methylene blue under visible light irradiation. The degradation rate constants of rhodamine B and methylene blue are 0.176 and 0.114 min{sup −1}, respectively. The cycling photodegradation experiments suggest that Ag/AgCl microds could be employed as stable plasmonic photocatalysts for the degradation of organic dyes under visible light irradiation.« less

Thermodynamic Properties of AgIn2Te3I and AgIn2Te3Br, Determined by EMF Method

NASA Astrophysics Data System (ADS)

Moroz, M. V.; Prokhorenko, M. V.; Prokhorenko, S. V.; Yatskov, M. V.; Reshetnyak, O. V.

2018-01-01

Differential thermal analysis (DTA), X-ray diffraction (XRD), and electromotive force (EMF) are used to triangulate Ag-In-Te-I(Br) systems in the vicinity of compounds AgIn2Te3I and AgIn2Te3Br. The three-dimensional position of the AgIn2Te3I-InTe-Ag2Te-AgI and AgIn2Te3Br-InTe-Ag3TeBr phase areas with respect to the figurative points of silver is used to create equations of potential-determining chemical reactions. The potential-determining reactions are conducted in (-)C|Ag|Ag3GeS3I(Br) glass|D|C(+) electrochemical cells (ECCs), where C stands for inert (graphite) electrodes, Ag and D are ECC electrodes (D denotes alloys of one-, three-, and four-phase areas), and Ag3GeS3I and Ag3GeS3Br glasses are membranes with purely ionic Ag+ conductivity. Linear parts of the temperature dependences of the cell EMFs are used to calculate the standard integral thermodynamic functions of saturated solid solutions based on AgIn2Te3I and AgIn2Te3Br, and the relative partial thermodynamic functions of silver in the stoichiometric quaternary compounds.

Fabrication of PANI/Ag/AgCl/ITO-PET Flexible Film and Its Crystallinity and Electrical Properties

NASA Astrophysics Data System (ADS)

Diantoro, M.; Rohmiani, F.; Mustikasari, A. A.; Sunaryono

2018-05-01

Abstrak. PANI as one of the conductive polymers which have been widely using in electronics or storage devices such as a supercapacitor. PANI has recently become an option because of its potential for a broad area of application. Protonation or introduce a dopant can control the electrical properties of PANI. However, researcher facing a disadvantage since PANI also active in acidic conditions. To control the conductivity and the stability in an acidic environment, the researcher has introduced Ag/AgCl to PANI. We report the synthesis and analyses of silver nanoparticles (AgNPs), PANI, and PANI/Ag/AgCl/ITO-PET films. PANI was synthesized by chemical polymerization, while AgNPs were synthesized via a reductive chemical method using NaBH4 as an AgNO3 reductor. The resulting PANI was characterized using FTIR to determine the functional group, while to obtain the purity of the Ag phase was checked by using XRD. The preparation of PANi/Ag/AgCl solution was carried out by mixing method with the variation of the mass of AgNO3. The precipitate was carried out by using ITOPET substrate. PANI/Ag/AgCl/ITO-PET films were characterized by using FTIR, XRD, SEMEDX, and capacitance meters. It has was found that crystallinity increases with the addition of Ag films to PANI/Ag/AgCl/ITO-PET. The crystallinity reached 29.85 %. It was also revealed that the dielectric constant decreased with increasing Ag in PANi/Ag/AgCl/ITO-PET films.

Facile synthesis of S-Ag nanocomposites and Ag2S short nanorods by the interaction of sulfur with AgNO3 in PEG400

NASA Astrophysics Data System (ADS)

Zhang, Yan-Li; Xie, Xin-Yuan; Liang, Ming; Xie, Shu-Ming; Chen, Jie-Mei; Zheng, Wen-Jie

2016-06-01

A facile, eco-friendly and inexpensive method to prepare Ag2S short nanorods and S-Ag nanocomposites using sublimed sulfur, AgNO3, PVP and PEG400 was studied. According to x-ray diffraction and scanning electron microscopy of the Ag2S, the products are highly crystalline and pure Ag2S nanorods with diameters of 70-160 nm and lengths of 200-360 nm. X-ray diffraction of the S-Ag nanocomposites shows that we obtained cubic Ag and S nanoparticles. Transmission electron microscopy shows that the molar ratio of PVP to Ag+ plays an important role in controlling the size and morphology of the S-Ag nanocomposites. When the molar ratio of PVP to Ag+ was 10:1, smaller sizes, better dispersibility and narrower distribution of S-Ag nanocomposites with diameters of 10-40 nm were obtained. The formation mechanism of the S-Ag nanocomposites was studied by designing a series of experiments using ultraviolet-visible measurement, and it was found that S nanoparticles are produced first and act as seed crystals; then Ag+ becomes Ag nanocrystals on the surfaces of the S nanoparticles by the reduction of PVP. PEG400 acts as a catalyzer, accelerating the reaction rate, and protects the S-Ag nanocomposites from reacting to produce Ag2S. The antimicrobial experiments show that the S-Ag nanocomposites have greater antimicrobial activity on Staphylococcus aureus, Aspergillus niger and blue mold than Ag nanoparticles.

Surface-enhanced Raman scattering of a Ag/oligo(phenyleneethynylene)/Ag sandwich.

PubMed

Fletcher, Melissa; Alexson, D M; Prokes, Sharka; Glembocki, Orest; Vivoni, Alberto; Hosten, Charles

2011-02-01

α,ω-Dithiols are a useful class of compounds in molecular electronics because of their ability to easily adsorb to two metal surfaces, producing a molecular junction. We have prepared Ag nanosphere/oligo(phenyleneethynylene)/Ag sol (AgNS/OPE/Ag sol) and Ag nanowire/oligo(phenyleneethynylene)/Ag sol (AgNW/OPE/Ag sol) sandwiches to simulate the architecture of a molecular electronic device. This was achieved by self-assembly of OPE on the silver nanosurface, deprotection of the terminal sulfur, and deposition of Ag sol atop the monolayer. These sandwiches were then characterized by surface-enhanced Raman scattering (SERS) spectroscopy. The resulting spectra were compared to the bulk spectrum of the dimer and to the Ag nanosurface/OPE SERS spectra. The intensities of the SERS spectra in both systems exhibit a strong dependence on Ag deposition time and the results are also suggestive of intense interparticle coupling of the electromagnetic fields in both the AgNW/OPE/Ag and the AgNS/OPE/Ag systems. Three previously unobserved bands (1219, 1234, 2037 cm(-1)) arose in the SER spectra of the sandwiches and their presence is attributed to the strong enhancement of the electromagnetic field which is predicted from the COSMOL computational package. The 544 cm(-1) disulfide bond which is observed in the spectrum of solid OPE but is absent in the AgNS/OPE/Ag and AgNW/OPE/Ag spectra is indicative of chemisorption of OPE to the nanoparticles through oxidative dissociation of the disulfide bond. Copyright © 2010 Elsevier B.V. All rights reserved.

Microstructure, mechanical properties, bio-corrosion properties and antibacterial properties of Ti-Ag sintered alloys.

PubMed

Chen, Mian; Zhang, Erlin; Zhang, Lan

2016-05-01

In this research, Ag element was selected as an antibacterial agent to develop an antibacterial Ti-Ag alloy by a powder metallurgy. The microstructure, phase constitution, mechanical properties, corrosion resistance and antibacterial properties of the Ti-Ag sintered alloys have been systematically studied by X-ray diffraction (XRD), scanning electron microscope (SEM), compressive test, electrochemical measurements and antibacterial test. The effects of the Ag powder size and the Ag content on the antibacterial property and mechanical property as well as the anticorrosion property have been investigated. The microstructure results have shown that Ti-Ag phase, residual pure Ag and Ti were the mainly phases in Ti-Ag(S75) sintered alloy while Ti2Ag was synthesized in Ti-Ag(S10) sintered alloy. The mechanical test indicated that Ti-Ag sintered alloy showed a much higher hardness and the compressive yield strength than cp-Ti but the mechanical properties were slightly reduced with the increase of Ag content. Electrochemical results showed that Ag powder size had a significant effect on the corrosion resistance of Ti-Ag sintered alloy. Ag content increased the corrosion resistance in a dose dependent way under a homogeneous microstructure. Antibacterial tests have demonstrated that antibacterial Ti-Ag alloy was successfully prepared. It was also shown that the Ag powder particle size and the Ag content influenced the antibacterial activity seriously. The reduction in the Ag powder size was benefit to the improvement in the antibacterial property and the Ag content has to be at least 3wt.% in order to obtain a strong and stable antibacterial activity against Staphylococcus aureus bacteria. The bacterial mechanism was thought to be related to the Ti2Ag and its distribution. Copyright © 2016 Elsevier B.V. All rights reserved.

Microwave-assisted solvothermal synthesis of flower-like Ag/AgBr/BiOBr microspheres and their high efficient photocatalytic degradation for p-nitrophenol

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

Li, Tingting, E-mail: tingtingli1983@hotmail.com; State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha 410082; Department of Environment and Chemical Engineering, Key Laboratory of Jiangxi Province for Ecological Diagnosis, Remediation and Pollution Control, Nanchang Hangkong University, Nanchang 330063

Flower-like Ag/AgBr/BiOBr microspheres were successfully fabricated by the approach of microwave-assisted solvothermal and in situ photo-assisted reduction. A reactive ionic liquid 1-hexadecyl-3-methylimidazolium bromide ([C{sub 16}mim]Br) was employed as Br source in the presence of surfactant polyvinylpyrrolidone (PVP). The photocatalytic activity of Ag/AgBr/BiOBr towards the decomposition of p-nitrophenol under visible light irradiation was evaluated. The results indicated that Ag/AgBr/BiOBr showed enhanced photocatalytic activity towards p-nitrophenol, comparing with P25, BiOBr and Ag/AgBr. More than 96% of p-nitrophenol was decomposed in 3.5 h under visible-light irradation. The excellent photocatalytic activity of flower-like Ag/AgBr/BiOBr microspheres can be attributed to the large specific surface area,more » strong visible-light absorption, suitable energy band structure and surface plasmon resonance effect of Ag nanoparticles. The possible photocatalytic mechanism was proposed based on the active species test and band gap structure analysis. - Graphical abstract: The photocatalytic reaction mechanisms of the as-prepared Ag/AgBr/BiOBr. Display Omitted - Highlights: • Successful synthesis of flower-like Ag/AgBr/BiOBr microspheres. • The Ag/AgBr/BiOBr showed much higher photocatalytic activity towards p-nitrophenol as compared to BiOBr and Ag/AgBr. • The reasons for the excellent photocatalytic activity are the large specific surface area, strong visible-light absorption and surface plasmon resonance effect of Ag nanoparticles. • The O{sub 2}·{sup −}, Br{sup 0} and photogenerated h{sup +} play key roles in the photocatalytic degradation process.« less

Translocation of silver nanoparticles in the ex vivo human placenta perfusion model characterized by single particle ICP-MS.

PubMed

Vidmar, Janja; Loeschner, Katrin; Correia, Manuel; Larsen, Erik H; Manser, Pius; Wichser, Adrian; Boodhia, Kailen; Al-Ahmady, Zahraa S; Ruiz, Jaimé; Astruc, Didier; Buerki-Thurnherr, Tina

2018-06-15

With the extensive use of silver nanoparticles (AgNPs) in various consumer products their potential toxicity is of great concern especially for highly sensitive population groups such as pregnant women and even the developing fetus. To understand if AgNPs are taken up and cross the human placenta, we studied their translocation and accumulation in the human ex vivo placenta perfusion model by single particle ICP-MS (spICP-MS). The impact of different surface modifications on placental transfer was assessed by AgNPs with two different modifications: polyethylene glycol (AgPEG NPs) and sodium carboxylate (AgCOONa NPs). AgNPs and ionic Ag were detected in the fetal circulation in low but not negligible amounts. Slightly higher Ag translocation across the placental barrier for perfusion with AgPEG NPs and higher AgNP accumulation in placental tissue for perfusion with AgCOONa NPs were observed. Since these AgNPs are soluble in water, we tried to distinguish between the translocation of dissolved and particulate Ag. Perfusion with AgNO3 revealed the formation of Ag containing NPs in both circulations over time, of which the amount and their size in the fetal circulation were comparable to those from perfusion experiments with both AgNP types. Although we were not able to clarify whether intact AgNPs and/or Ag precipitates from dissolved Ag cross the placental barrier, our study highlights that uptake of Ag ions and/or dissolution of AgNPs in the tissue followed by re-precipitation in the fetal circulation needs to be considered as an important pathway in studies of AgNP translocation across biological barriers.

Surface coating-modulated toxic responses to silver nanoparticles in Wolffia globosa.

PubMed

Zou, Xiaoyan; Li, Penghui; Lou, Jie; Zhang, Hongwu

2017-08-01

With the omnipresence of silver nanoparticles (AgNPs) in our daily consumer products, their release has raised serious concerns. However, the biochemical mechanisms by which plants counteract the toxicity of nanoparticles are largely unknown. This study investigated the exposure of aquatic Wolffia globosa to ATP-nAg (AgNPs coated with adenosine triphosphate), cit-nAg (AgNPs coated with citrate), and Ag + . Hill reaction activity was basically lost in W. globosa treated with 10mg/L ATP-nAg and Ag + , while the activity was still maintained at 38.7%-38.9% of the respective controls at 10mg/L cit-nAg. The reduction of amounts of chlorophyll and soluble protein were shown in response to the Ag stresses. This was accompanied by the accumulation of sugar in W. globosa treated with cit-nAg. By contrast, the depletion of sugar was recorded after 10mg/L ATP-nAg and Ag + treatments. The superoxide dismutase and peroxidase activities were significantly increased after exposure to 10mg/L ATP-nAg and Ag + , which did not occurred in W. globosa treated with cit-nAg. The ratio between NADPH/NADP + was higher after cit-nAg and Ag + stresses than the respective controls. The accumulation of Ag was found to increase in a concentration-dependent manner. Ag + and ATP-nAg inhibited the uptake of P and K, and promoted the uptake of Fe and Cu. In contrast, cit-nAg only promoted the uptake of Cu. Our results implied that surface coating induced different physiological responses of W. globosa to AgNPs. Based on above results, we speculated that after exposure to cit-nAg, citrate possibly could serve as the substrate for the tricarboxylic acid cycle and accumulated sugar may promote pentose phosphate pathways. For ATP-nAg treatments, ATP would act as an exogenous energy source of plant metabolisms. Our findings demonstrate that surface coating regulates the physiological responses of plants to AgNPs through distinct mechanisms. Copyright © 2017. Published by Elsevier B.V.

A biodynamic understanding of dietborne and waterborne Ag uptake from Ag NPs in the sediment-dwelling oligochaete, Tubifex tubifex

USGS Publications Warehouse

Tangaa, Stine Rosendal; Winther-Nielsen, Margrethe; Selck, Henriette; Croteau, Marie-Noele

2018-01-01

Metal nanoparticles (Me-NPs) are increasingly used in various products, such as inks and cosmetics, enhancing the likelihood of their release into aquatic environments. An understanding of the mechanisms controlling their bioaccumulation and ecotoxicity in aquatic biota will help support environmental risk assessment. Here we characterized unidirectional parameters for uptake and elimination of silver (Ag) in the sediment-dwelling oligochaete Tubifex tubifex after waterborne (0.01–47 nmol Ag/L) and dietborne (0.4–482 nmol Ag/g dw sed.) exposures to Ag NPs and AgNO3, respectively. Worms accumulated Ag from AgNO3more efficiently than from Ag NPs during waterborne exposure. The Ag uptake rate constants from water were 8.2 L/g/d for AgNO3 and 0.34 L/g/d for Ag NPs. Silver accumulated from both forms was efficiently retained in tissues, as no significant loss of Ag was detected after up to 20 days of depuration in clean media. High mortality (~50%) during depuration (i.e. after 17 days) was only observed for worms exposed to waterborne AgNO3 (3 nmol/L). Sediment exposures to both Ag forms resulted in low accumulation, i.e., the uptake rate constants were 0.002 and 0.005 g/g/d for AgNO3 and Ag NPs, respectively. Avoidance was only observed for worms exposed to sediment amended with AgNO3. Incorporation of the estimated rate constants into a biodynamic model predicted that sediment is likely the most important route of uptake for Ag in both forms in ecologically relevant aquatic environments. However, inference of bioavailability from our estimations of Ag assimilation efficiencies (AE) suggests that Ag (AE: 3–12% for AgNO3 and 0.1–0.8% for Ag NPs) is weakly bioavailable from sediment for this species. Thus, Ag amended to sediment as NPs might not pose greater problems than 'conventional' Ag for benthic organisms such as T. tubifex.

Transformation of PVP coated silver nanoparticles in a simulated wastewater treatment process and the effect on microbial communities

PubMed Central

2013-01-01

Background Manufactured silver nanoparticles (AgNPs) are one of the most commonly used nanomaterials in consumer goods and consequently their concentrations in wastewater and hence wastewater treatment plants are predicted to increase. We investigated the fate of AgNPs in sludge that was subjected to aerobic and anaerobic treatment and the impact of AgNPs on microbial processes and communities. The initial identification of AgNPs in sludge was carried out using transmission electron microscopy (TEM) with energy dispersive X-ray (EDX) analysis. The solid phase speciation of silver in sludge and wastewater influent was then examined using X-ray absorption spectroscopy (XAS). The effects of transformed AgNPs (mainly Ag-S phases) on nitrification, wastewater microbial populations and, for the first time, methanogenesis was investigated. Results Sequencing batch reactor experiments and anaerobic batch tests, both demonstrated that nitrification rate and methane production were not affected by the addition of AgNPs [at 2.5 mg Ag L-1 (4.9 g L-1 total suspended solids, TSS) and 183.6 mg Ag kg -1 (2.9 g kg-1 total solids, TS), respectively]. The low toxicity is most likely due to AgNP sulfidation. XAS analysis showed that sulfur bonded Ag was the dominant Ag species in both aerobic (activated sludge) and anaerobic sludge. In AgNP and AgNO3 spiked aerobic sludge, metallic Ag was detected (~15%). However, after anaerobic digestion, Ag(0) was not detected by XAS analysis. Dominant wastewater microbial populations were not affected by AgNPs as determined by DNA extraction and pyrotag sequencing. However, there was a shift in niche populations in both aerobic and anaerobic sludge, with a shift in AgNP treated sludge compared with controls. This is the first time that the impact of transformed AgNPs (mainly Ag-S phases) on anaerobic digestion has been reported. Conclusions Silver NPs were transformed to Ag-S phases during activated sludge treatment (prior to anaerobic digestion). Transformed AgNPs, at predicted future Ag wastewater concentrations, did not affect nitrification or methanogenesis. Consequently, AgNPs are very unlikely to affect the efficient functioning of wastewater treatment plants. However, AgNPs may negatively affect sub-dominant wastewater microbial communities. PMID:23497481

Transformation of nanosilver in oxidized and reduced soils

NASA Astrophysics Data System (ADS)

Hashimoto, Y.; Mitsunobu, S.; Yamaguchi, N.

2013-12-01

A recent development in the manufacturing of consumer products has been the incorporation of nano-sized (< 100 nm) particles. Because of their antimicrobial properties, Ag nanoparticles (NPs) have been used in many purposes including medical devices, foodstorage containers, soaps and sanitizers, wound dressings, and fabrics. Textiles enhanced with AgNPs (e.g., socks) may leach Ag(I) and nanoparticles as they are washed. These nanoparticles are either deposited directly to land or gradually washed away in household wastewater. The AgNPs, similar to Ag(I), will partition to sludge in a wastewater treatment plant, and the sewage sludge may be applied as a land amendment to agricultural fields and urban landscapes. As a consequence, the concentration of Ag in soils can increase gradually for a long period of Ag-containing sludge. Because of their antimicrobial properties, the presence of Ag in the soil adversely affects soil's biologically-mediated functions such as nutrient cycling. In many of previous studies, however, it was not clear if toxicity was caused by the AgNPs themselves or Ag ions released as the result of oxidation and dissolution. Also, mobility and fate of Ag in the environment remain little known. To understand toxicological properties and fate of Ag in soils, chemical speciation of Ag is the critical information. The objective of this study was to determine chemical speciation of Ag derived from AgNP (Ago) and Ag chemicals (AgNO3) in oxidized and reduced soils. We employed X-ray absorption fine structure (XAFS) spectroscopy to identify Ag species and probable hosting phases in soils, and the study was focused on how the soil redox condition transforms AgNP into Ag(I) and vice versa. A soil incubation study was conducted using a volcanic ash soil amended with AgNO3 and AgNPs up to the levels of 1000 mg kg-1 soil. The soil water content was adjusted to the levels of field capacity (oxidized) and saturated (reduced) condition. After 30 days of incubation at 25 C, the soils were collected and analyzed for Ag by sequential extraction and Ag K-edge XAFS spectroscopy. To find probable Ag species in the soils, linear combination fitting was performed on Ag EXAFS data of soils using known reference Ag chemicals and sorption phases. According to the EXAFS analysis, AgNO3 did not exist and was transformed into humus and phyllosilicate-associated phases in the oxidized soil. In the reduced soils, AgNO3 was completely transformed into other compounds including Ago and Ag associated with soil colloids (phyllosilicate and gibbsite). The redox potential of this soil remained oxic levels (457 mV) due to extremely high Ag+ concentration, and the redox condition was not low enough to form sulfide Ag species. About 90% of AgNPs remained persistent in the oxidized soil. In contrast, AgNPs was transformed mainly into Ag2S in the reduced soil. Our study found that AgNPs remained persistent in oxidized soils but can be transformed into sulfide-associated forms in reduced soils.

Thermodynamic assessment of the Sn-Co lead-free solder system

NASA Astrophysics Data System (ADS)

Liu, Libin; Andersson, Cristina; Liu, Johan

2004-09-01

The Sn-Co-Cu eutectic alloy can be a less expensive alternative for the Sn-Ag-Cu alloy. In order to find the eutectic solder composition of the Sn-Co-Cu system, the Sn-Co binary system has been thoroughly assessed with the calculation of phase diagram (CALPHAD) method. The liquid phase, the FCC and HCP Co-rich solid solution, and the BCT Sn-rich solid solution have been described by the Redlich-Kister model. The Hillert-Jarl-Inden model has been used to describe the magnetic contributions to Gibbs energy in FCC and HCP. The CoSn2, CoSn, Co3Sn2_β, and Co3Sn2_α phases have been treated as stoichiometric phases. A series of thermodynamic parameters have been obtained. The calculated phase diagram and thermodynamic properties are in good agreement with the experimental data. The obtained thermodynamic data was used to extrapolate the ternary Sn-Co-Cu phase diagram. The composition of the Sn-rich eutectic point of the Sn-Co-Cu system was found to be 224°C, 0.4% Co, and 0.7% Cu.

Seroprevalence of human hydatidosis using ELISA method in qom province, central iran.

PubMed

Rakhshanpour, A; Harandi, M Fasihi; Moazezi, Ss; Rahimi, Mt; Mohebali, M; Mowlavi, Ghh; Babaei, Z; Ariaeipour, M; Heidari, Z; Rokni, Mb

2012-01-01

The objective of this study was to determine the prevalence of cystic echinococcosis (CE) in Qom Province, central Iran using ELISA test. Overall, 1564 serum samples (800 males and 764 females) were collected from selected subjects by randomized cluster sampling in 2011-2012. Sera were analyzed by ELISA test using AgB. Before sampling, a questionnaire was filled out for each case. Data were analyzed using Chi-square test and multivariate logistic regression for risk factors analysis. Seropositivity was 1.6% (25 cases). Males (2.2%) showed significantly more positivity than females (0.9%) (P= 0.03). There was no significant association between CE seropositivity and age group, occupation, and region. Age group of 30-60 years encompassed the highest rate of positivity. The seropositivity of CE was 2.1% and 1.2% for urban and rural cases respectively. Binary logistic regression showed that males were 2.5 times at higher risk for infection than females. Although seroprevalence of CE is relatively low in Qom Province, yet due to the importance of the disease, all preventive measures should be taken into consideration.

Selective adsorption of Pb(II) from aqueous solution using porous biosilica extracted from marine diatom biomass: Properties and mechanism

NASA Astrophysics Data System (ADS)

Qi, Yarong; Wang, Jingfeng; Wang, Xin; Cheng, Jay Jiayang; Wen, Zhiyou

2017-02-01

Biosilica with a surface area of 143 m2 g-1 derived from marine diatoms was prepared using an easy two-step method involving washing with dilute acid and baking. The extracted biosilica was used to remove divalent lead ions, i.e., Pb(II), from aqueous solution. The effects on Pb(II) adsorption of initial pH, shaking speed, and adsorbent loading were investigated. The adsorption of Pb(II) in the presence of other ions was also investigated. The biosilica showed a high adsorption capacity with high selectivity for Pb(II). The experimental maximum adsorption capacity was 108.2-120.4 mg g-1 at an adsorbent loading of 1 g L-1. The adsorption process was best described by the Langmuir model. The adsorbent selectively adsorbed Pb(II) from binary ion systems in the presence of Cu(II), Cd(II), Ni(II), and Ag(I). The results of this study show that biosilica extracted from fresh marine diatoms is a more efficient and selective adsorbent for Pb(II) than other inorganic adsorbents.

Reaction of YBa2Cu3O(7-beta) with Gold, Silver, Bismuth and Lead: Substitution Chemistry and Composite Fabrication

NASA Technical Reports Server (NTRS)

Hepp, Aloysius F.; Gaier, James R.

1993-01-01

The reaction of YBa2Cu3O(7-beta) with Au, Ag, Bi, and Ph ions or metal is described. Three types of materials were produced: a well-defined series of homogeneous superconductors was obtained for Au ion substitution with little effect on T(sub c); attempted Ag and Bi ion substitution resulted in multi-phase samples with slightly enhanced T(sub c); finally, attempts to produce superconducting metal/superconducting ceramic composites with Pb and Bi powders resulted in multi-phase samples with drastically diminished superconducting properties. For Au- substituted superconductors, YBa2(Cu(l-x)Au(x))3O(7-beta), a substitution series (x = 0 - 0.1) has been synthesized. For x = 0.1 there was no change in the a and b lattice parameters (a = 3.826 A and b = 3.889 A) but a 0.06 A c axis expansion to 11.75 A was observed. The valence of Cu and Au in YBa2Au(0.3)Cu(2.7)O(7-beta) was investigated using X-ray Absorption Near-Edge Structure (XANES). X-ray studies indicate that Au goes into the Cu(l) site and Cu K edge XANES shows that this has little effect on the oxidation state of the remaining copper. A small effect on T(sub c) is observed (T(sub c) = 89 K for x = 0.10). Ag and Bi addition results in a rise in T(sub c) and a decrease in (delta)T(sub c) at low levels (x = 0.10 Ag, T(sub c) = 94 K and (delta)T(sub c) = 0.5 K; x = 0.02 Bi, T(sub c) = 94 K and (delta)T(sub c) = 1K) relative to typical values for YBa2Cu3O(7-beta) (T(sub c) = 91 K, (delta)T(sub c) = 2 K). Attempts at fabrication of Pb- and Pb(1-x)Bi(x)-superconductor composites are described. Cold pressing followed by low temperature (200 C) sintering resulted in a composite which excluded flux below 90 K but did not show zero electrical resistance until the metal (alloy) superconducting transition. X-ray diffraction showed the presence of pervoskite and metal. Processing at moderate (450 C) or high (950 C) temperatures resulted in oxygen-depleted pervoskite and/or metal oxides. These materials displayed greatly degraded superconducting properties. Processing at 800 C resulted in high T(sub c) only for composites containing greater than 90% weight fraction ceramic. Reaction of metal with YBa2Cu3O(7-beta) formed superconducting lead/bismuth-based oxides and other binary oxides.

Polyvinyl polypyrrolidone attenuates genotoxicity of silver nanoparticles synthesized via green route, tested in Lathyrus sativus L. root bioassay.

PubMed

Panda, Kamal K; Achary, V Mohan M; Phaomie, Ganngam; Sahu, Hrushi K; Parinandi, Narasimham L; Panda, Brahma B

2016-08-01

The silver nanoparticles (AgNPs) were synthesized extracellularly from silver nitrate (AgNO3) using kernel extract from ripe mango Mengifera indica L. under four different reaction conditions of the synthesis media such as the (i) absence of the reducing agent, trisodium citrate (AgNPI), (ii) presence of the reducing agent (AgNPII), (iii) presence of the cleansing agent, polyvinyl polypyrrolidone, PVPP (AgNPIII), and (iv) presence of the capping agent, polyvinyl pyrrolidone, PVP (AgNPIV). The synthesis of the AgNPs was monitored by UV-vis spectrophotometry. The AgNPs were characterised by the energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffraction, and small-angle X-ray scattering. Functional groups on the AgNPs were established by the Fourier transform infrared spectroscopy. The AgNPs (AgNPI, AgNPII, AgNPIII and AgNPIV) were spherical in shape with the diameters and size distribution-widths of 14.0±5.4, 19.2±6.6, 18.8±6.6 and 44.6±13.2nm, respectively. Genotoxicity of the AgNPs at concentrations ranging from 1 to 100mgL(-1) was determined by the Lathyrus sativus L. root bioassay and several endpoint assays including the generation of reactive oxygen species and cell death, lipid peroxidation, mitotic index, chromosome aberrations (CA), micronucleus formation (MN), and DNA damage as determined by the Comet assay. The dose-dependent induction of genotoxicity of the silver ion (Ag(+)) and AgNPs was in the order Ag(+)>AgNPII>AgNPI>AgNPIV>AgNPIII that corresponded with their relative potencies of induction of DNA damage and oxidative stress. Furthermore, the findings underscored the CA and MN endpoint-based genotoxicity assay which demonstrated the genotoxicity of AgNPs at concentrations (≤10mgL(-1)) lower than that (≥10mgL(-1)) tested in the Comet assay. This study demonstrated the protective action of PVPP against the genotoxicity of AgNPIII which was independent of the size of the AgNPs in the L. sativus L. root bioassay system. Copyright © 2016 Elsevier B.V. All rights reserved.

Ag{sub 2}O/Ag{sub 3}VO{sub 4}/Ag{sub 4}V{sub 2}O{sub 7} heterogeneous photocatalyst prepared by a facile hydrothermal synthesis with enhanced photocatalytic performance under visible light irradiation

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

Ran, Rong; McEvoy, Joanne Gamage; Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, Ontario, K1N 6N5

Highlights: • The photocatalyst was hydrothermally prepared by adjusting the ratio of Ag to V. • Multi-phase Ag{sub 2}O/Ag{sub 3}VO{sub 4}/Ag{sub 4}V{sub 2}O{sub 7} obtained exhibited multi-morphological features. • The photocatalyst exhibited strong visible light driven photoactivity towards RhB. - Abstract: A novel Ag{sub 2}O/Ag{sub 3}VO{sub 4}/Ag{sub 4}V{sub 2}O{sub 7} photocatalyst was synthesized by adjusting the molar ratio of silver–vanadium (Ag–V) in a facile hydrothermal method to obtain multi-phase Ag{sub 2}O/Ag{sub 3}VO{sub 4}/Ag{sub 4}V{sub 2}O{sub 7} photocatalyst. The photocatalytic activity of the prepared samples was quantified by the degradation of Rhodamine B (RhB) model organic pollutant under visible light irradiation.more » Compared to pure Ag{sub 3}VO{sub 4}, Ag{sub 4}V{sub 2}O{sub 7} and P25 TiO{sub 2}, respectively, the as-synthesized multi-phase Ag{sub 2}O/Ag{sub 3}VO{sub 4}/Ag{sub 4}V{sub 2}O{sub 7} powders gave rise to a significantly higher photocatalytic activity, achieving up to 99% degradation of RhB in 2 h under visible light. This enhanced photocatalytic performance was attributed to the effect of the multi-phase Ag{sub 2}O/Ag{sub 3}VO{sub 4}/Ag{sub 4}V{sub 2}O{sub 7} photocatalyst and the surface plasmon resonance (SPR) of the incorporated metallic silver (Ag{sup 0}) nanoparticles (NPs) generated during the photocatalysis, as evidenced by post-use characterization, resulting in improved visible light absorption and electron-hole (e{sup −}-h{sup +}) separation. A mechanism was proposed for the photocatalytic degradation of RhB on the surface of Ag{sub 2}O/Ag{sub 3}VO{sub 4}/Ag{sub 4}V{sub 2}O{sub 7}.« less

Inactivation, Clearance, and Functional Effects of Lung-Instilled Short and Long Silver Nanowires in Rats

PubMed Central

2017-01-01

There is a potential for silver nanowires (AgNWs) to be inhaled, but there is little information on their health effects and their chemical transformation inside the lungs in vivo. We studied the effects of short (S-AgNWs; 1.5 μm) and long (L-AgNWs; 10 μm) nanowires instilled into the lungs of Sprague–Dawley rats. S- and L-AgNWs were phagocytosed and degraded by macrophages; there was no frustrated phagocytosis. Interestingly, both AgNWs were internalized in alveolar epithelial cells, with precipitation of Ag2S on their surface as secondary Ag2S nanoparticles. Quantitative serial block face three-dimensional scanning electron microscopy showed a small, but significant, reduction of NW lengths inside alveolar epithelial cells. AgNWs were also present in the lung subpleural space where L-AgNWs exposure resulted in more Ag+ve macrophages situated within the pleura and subpleural alveoli, compared with the S-AgNWs exposure. For both AgNWs, there was lung inflammation at day 1, disappearing by day 21, but in bronchoalveolar lavage fluid (BALF), L-AgNWs caused a delayed neutrophilic and macrophagic inflammation, while S-AgNWs caused only acute transient neutrophilia. Surfactant protein D (SP-D) levels in BALF increased after S- and L-AgNWs exposure at day 7. L-AgNWs induced MIP-1α and S-AgNWs induced IL-18 at day 1. Large airway bronchial responsiveness to acetylcholine increased following L-AgNWs, but not S-AgNWs, exposure. The attenuated response to AgNW instillation may be due to silver inactivation after precipitation of Ag2S with limited dissolution. Our findings have important consequences for the safety of silver-based technologies to human health. PMID:28221763

Toxicokinetics and toxicodynamics of differently coated silver nanoparticles and silver nitrate in Enchytraeus crypticus upon aqueous exposure in an inert sand medium.

PubMed

Topuz, Emel; van Gestel, Cornelis A M

2015-12-01

The aim of the present study was to evaluate the effect of silver nanoparticles (AgNPs) on Enchytraeus crypticus, applying a combined toxicokinetics and toxicodynamics approach to understand the relationship between survival and the development of internal Ag concentrations in the animals over time. Toxicity tests were conducted in medium composed of well-defined aqueous solutions added to inert quartz sand to avoid the complexity of soil conditions. Citrate-coated AgNPs (AgNP-Cit) and polyvinylpyrrolidone-coated AgNPs (AgNP-PVP) were tested and compared with silver nitrate (AgNO3), which was used as a positive control for Ag ion effects. The median lethal concentration (LC50) values based on Ag concentrations in the solution phase of the test medium decreased over time and reached steady state after 7 d, with AgNO3 and AgNP-PVP being more toxic than AgNP-Cit. Slow dissolution may explain the low uptake kinetics and lower toxicity of AgNP-Cit compared with the other 2 Ag forms. The LC50 values based on internal Ag concentrations in the animals were almost stable over time, highlighting the importance of integrating toxicokinetics and toxicodynamics and relating survival with internal Ag concentrations. Neither survival-based elimination rates nor internal LC50s in the organisms showed any significant evidence of nano-specific effects for both AgNPs, although they suggested some uptake of particulate Ag for AgNP-Cit. The authors conclude that the toxicity of both types of AgNP probably is mainly attributable to the release of Ag ions. © 2015 SETAC.

Differential bioaccumulation patterns of nanosized and dissolved silver in a land snail Achatina fulica.

PubMed

Chen, Yuanzhen; Si, Youbin; Zhou, Dongmei; Dang, Fei

2017-03-01

With the increasing application in antimicrobial products, silver nanoparticles (AgNP) are inevitably released into the terrestrial environment, and pose potential risks to invertebrates such as land snails Achatina fulica, which take up AgNP from food and water. Here we differentiate Ag uptake biodynamic between Ag forms (i.e., PVP-AgNP vs. AgNO 3 ) and between exposure pathways. Snails assimilated Ag efficiently from lettuce leaves pre-exposed to AgNP, with assimilation efficiencies (AEs) averaging 62-85% and food ingestion rates of 0.11 ± 0.03 g g -1  d -1 . Dietary Ag bioavailability was independent on Ag forms, as revealed by comparable AEs between AgNP and AgNO 3 . However, the uptake rate constant from water was much lower for AgNP relative to AgNO 3 (2 × 10 -4 vs. 0.12 L g -1  d -1 ). The elimination rate constants were 0.0093 ± 0.0037 d -1 for AgNP and 0.019 ± 0.0077 d -1 for AgNO 3 . Biodynamic modeling further showed that dietary exposure was the dominant uptake pathway for AgNP in most circumstances, while for AgNO 3 the relative importance of waterborne and dietary exposure depended on Ag concentrations in food and water. Our findings highlight the importance of dietary uptake of AgNP during bioaccumulation, which should be considered in the risk assessment of these nanoparticles. Copyright © 2017 Elsevier Ltd. All rights reserved.

Toward full spectrum speciation of silver nanoparticles and ionic silver by on-line coupling of hollow fiber flow field-flow fractionation and minicolumn concentration with multiple detectors.

PubMed

Tan, Zhi-Qiang; Liu, Jing-Fu; Guo, Xiao-Ru; Yin, Yong-Guang; Byeon, Seul Kee; Moon, Myeong Hee; Jiang, Gui-Bin

2015-08-18

The intertransformation of silver nanoparticles (AgNPs) and ionic silver (Ag(I)) in the environment determines their transport, uptake, and toxicity, demanding methods to simultaneously separate and quantify AgNPs and Ag(I). For the first time, hollow fiber flow field-flow fractionation (HF5) and minicolumn concentration were on-line coupled together with multiple detectors (including UV-vis spectrometry, dynamic light scattering, and inductively coupled plasma mass spectrometry) for full spectrum separation, characterization, and quantification of various Ag(I) species (i.e., free Ag(I), weak and strong Ag(I) complexes) and differently sized AgNPs. While HF5 was employed for filtration and fractionation of AgNPs (>2 nm), the minicolumn packed with Amberlite IR120 resin functioned to trap free Ag(I) or weak Ag(I) complexes coming from the radial flow of HF5 together with the strong Ag(I) complexes and tiny AgNPs (<2 nm), which were further discriminated in a second run of focusing by oxidizing >90% of tiny AgNPs to free Ag(I) and trapped in the minicolumn. The excellent performance was verified by the good agreement of the characterization results of AgNPs determined by this method with that by transmission electron microscopy, and the satisfactory recoveries (70.7-108%) for seven Ag species, including Ag(I), the adduct of Ag(I) and cysteine, and five AgNPs with nominal diameters of 1.4 nm, 10 nm, 20 nm, 40 nm, and 60 nm in surface water samples.

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

PubMed

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

2015-12-07

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

Effect of Ag addition to L1{sub 0} FePt and L1{sub 0} FePd films grown by molecular beam epitaxy

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

Tokuoka, Y.; Seto, Y.; Kato, T., E-mail: takeshik@nuee.nagoya-u.ac.jp

2014-05-07

L1{sub 0} ordered FePt-Ag (5 nm) and FePd-Ag (5 nm) films were grown on MgO (001) substrate at temperatures of 250–400 °C by using molecular beam epitaxy method, and their crystal and surface structures, perpendicular magnetic anisotropies and Curie temperatures were investigated. In the case of FePt-Ag, Ag addition with the amount of 10–20 at. % was effective to promote L1{sub 0} ordering and granular growth, resulting in the increase of the perpendicular magnetic anisotropy and coercivity of the FePt-Ag films. On the other hand, in the case of FePd-Ag, Ag addition changed the surface morphology from island to continuous film associated with themore » reductions of its coercivity and perpendicular anisotropy. The variations of lattice constants and Curie temperature with Ag addition were significantly different between FePt-Ag and FePd-Ag. For FePd-Ag, the c and a axes lattice spacings and Curie temperature gradually changed with increasing Ag content, while they unchanged for FePt-Ag. These results suggest the possibility of the formation of FePdAg alloy in FePd-Ag, while Ag segregation in FePt-Ag.« less

AgFNS overexpression increase apigenin and decrease anthocyanins in petioles of transgenic celery.

PubMed

Tan, Guo-Fei; Ma, Jing; Zhang, Xin-Yue; Xu, Zhi-Sheng; Xiong, Ai-Sheng

2017-10-01

Apigenin and anthocyanin biosyntheses share common precursors in plants. Flavone synthase (FNS) converts naringenin into apigenin in higher plants. Celery is an important edible and medical vegetable crop that contains apigenin in its tissues. However, the effect of high AgFNS gene expression on the apigenin and anthocyanins contents of purple celery remains to be elucidated. In this study, the AgFNS gene was cloned from purple celery ('Nanxuan liuhe purple celery') and overexpressed in this purple celery to determine its influence on anthocyanins and apigenin contents. Results showed that the AgFNS gene was 1068bp, which encodes 355 amino acid residues. Evolution analysis showed that the AgFNS protein belongs to the FSN I type. In AgFNS transgenic celery, the anthocyanins content in petioles was lower than that wild-type celery plants. Apigenin content increased in the petioles of AgFNS transgenic celery. The transcript levels of the AgPAL, AgC4H, AgCHS, and AgCHI genes were up-regulated, whereas those of the AgF3H, AgF3'H, AgDFR, AgANS, and Ag3GT genes were down-regulated in the petioles of AgFNS transgenic plants compared with wild-type celery plants. This work provides basic knowledge about the function of the AgFNS gene in the anthocyanin and apigenin biosyntheses of celery. Copyright © 2017 Elsevier B.V. All rights reserved.

Synthesis and characterization of novel plasmonic Ag/AgX-CNTs (X = Cl, Br, I) nanocomposite photocatalysts and synergetic degradation of organic pollutant under visible light.

PubMed

Shi, Huixian; Chen, Jiangyao; Li, Guiying; Nie, Xin; Zhao, Huijun; Wong, Po-Keung; An, Taicheng

2013-08-14

A series of novel well-defined Ag/AgX (X = Cl, Br, I) loaded carbon nanotubes (CNTs) composite photocatalysts (Ag/AgX-CNTs) were fabricated for the first time via a facile ultrasonic assistant deposition-precipitation method at the room temperature (25 ± 1 °C). X-ray diffraction, X-ray photoelectron spectroscopy, nitrogen adsorption-desorption analysis, scanning electron microscopy, and ultraviolet-visible light absorption spectra analysis were used to characterize the structure, morphology, and optical properties of the as-prepared photocatalysts. Results confirmed the existence of the direct interfacial contact between Ag/AgX nanoparticles and CNTs, and Ag/AgX-CNTs nanocomposites exhibit superior absorbance in the visible light (VL) region owing to the surface plasmon resonance (SPR) of Ag nanoparticles. The fabricated composite photocatalysts were employed to remove 2,4,6-tribromophenol (TBP) in aqueous phase. A remarkably enhanced VL photocatalytic degradation efficiency of Ag/AgX-CNTs nanocomposites was observed when compared to that of pure AgX or CNTs. The photocatalytic activity enhancement of Ag/AgX-CNTs was due to the effective electron transfer from photoexcited AgX and plasmon-excited Ag(0) nanoparticles to CNTs. This can effectively decrease the recombination of electron-hole pairs, lead to a prolonged lifetime of the photoholes that promotes the degradation efficiency.

Preparation and Characterization of Gelatin Nanofibers Containing Silver Nanoparticles

PubMed Central

Jeong, Lim; Park, Won Ho

2014-01-01

Ag nanoparticles (NPs) were synthesized in formic acid aqueous solutions through chemical reduction. Formic acid was used for a reducing agent of Ag precursor and solvent of gelatin. Silver acetate, silver tetrafluoroborate, silver nitrate, and silver phosphate were used as Ag precursors. Ag+ ions were reduced into Ag NPs by formic acid. The formation of Ag NPs was characterized by a UV-Vis spectrophotometer. Ag NPs were quickly generated within a few minutes in silver nitrate (AgNO3)/formic acid solution. As the water content of formic acid aqueous solution increased, more Ag NPs were generated, at a higher rate and with greater size. When gelatin was added to the AgNO3/formic acid solution, the Ag NPs were stabilized, resulting in smaller particles. Moreover, gelatin limits further aggregation of Ag NPs, which were effectively dispersed in solution. The amount of Ag NPs formed increased with increasing concentration of AgNO3 and aging time. Gelatin nanofibers containing Ag NPs were fabricated by electrospinning. The average diameters of gelatin nanofibers were 166.52 ± 32.72 nm, but these decreased with the addition of AgNO3. The average diameters of the Ag NPs in gelatin nanofibers ranged between 13 and 25 nm, which was confirmed by transmission electron microscopy (TEM). PMID:24758929

Orchid seed removal by ants in Neotropical ant-gardens.

PubMed

Morales-Linares, J; García-Franco, J G; Flores-Palacios, A; Valenzuela-González, J E; Mata-Rosas, M; Díaz-Castelazo, C

2018-05-01

Most plants that inhabit ant-gardens (AGs) are cultivated by the ants. Some orchids occur in AGs; however, it is not known whether their seeds are dispersed by AG ants because most orchid seeds are tiny and dispersed by wind. We performed in situ seed removal experiments, in which we simultaneously provided Azteca gnava ants with seeds of three AG orchid species and three other AG epiphyte species (Bromeliaceae, Cactaceae and Gesneriaceae), as well as the non-AG orchid Catasetum integerrimum. The seeds most removed were those of the bromeliad Aechmea tillandsioides and the gesneriad Codonanthe uleana, while seeds of AG orchids Coryanthes picturata, Epidendrum flexuosum and Epidendrum pachyrachis were less removed. The non-AG orchid was not removed. Removal values were positively correlated with the frequency of the AG epiphytes in the AGs, and seeds of AG orchids were larger than those of non-AG orchids, which should favour myrmecochory. Our data show that Azt. gnava ants discriminate and preferentially remove seeds of the AG epiphytes. We report for the first time the removal of AG orchid seeds by AG ants in Neotropical AGs. © 2018 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands.

Synthesis of AG@AgCl Core-Shell Structure Nanowires and Its Photocatalytic Oxidation of Arsenic (III) Under Visible Light.

PubMed

Qin, Yanyan; Cui, Yanping; Tian, Zhen; Wu, Yangling; Li, Yilian

2017-12-01

Ag@AgCl core-shell nanowires were synthesized by oxidation of Ag nanowires with moderate FeCl 3 , which exhibited excellent photocatalytic activity for As(III) oxidation under visible light. It was proved that the photocatalytic oxidation efficiency was significantly dependent on the mole ratio of Ag:AgCl. The oxidation rate of As(III) over Ag@AgCl core-shell nanowires first increased with the decrease of Ag 0 percentage, up until the optimized synthesis mole ratio of Ag nanowires:FeCl 3 was 2.32:2.20, with 0.023 mg L -1  min -1 As(III) oxidation rate; subsequently, the oxidation rate dropped with the further decrease of Ag 0 percentage. Effects of the pH, ionic strength, and concentration of humic acid on Ag@AgCl photocatalytic ability were also studied. Trapping experiments using radical scavengers confirmed that h + and ·O 2 - acted as the main active species during the visible-light-driven photocatalytic process for As(III) oxidation. The recycling experiments validated that Ag@AgCl core-shell nanowires were a kind of efficient and stable photocatalyst for As(III) oxidation under visible-light irradiation.

Visualizing Redox Dynamics of a Single Ag/AgCl Heterogeneous Nanocatalyst at Atomic Resolution

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

Wu, Yimin A.; Li, Liang; Li, Zheng

Operando characterization of gas solid reactions at the atomic scale is of great importance for determining the mechanism of catalysis. This is especially true in the study of heterostructures because of structural correlation between the different parts. However, such experiments are challenging and have rarely been accomplished. In this work, atomic scale redox dynamics of Ag/AgCl heterostructures have been studied using in situ environmental transmission electron microscopy (ETEM) in combination with density function theory (DFT) calculations. The reduction of Ag/AgCl to Ag is likely a result of the formation of Cl vacancies while Ag+ ions accept electrons. The oxidation processmore » of Ag/AgCl has been observed: rather than direct replacement of Cl by O, the Ag/AgCl nanocatalyst was first reduced to Ag, and then Ag was oxidized to different phases of silver oxide under different O-2 partial pressures. Ag2O formed at low O-2 partial pressure, whereas AgO formed at atmospheric pressure. By combining in situ ETEM observation and DFT calculations, this structural evolution is characterized in a distinct nanoscale environment.« less

Trojan-horse mechanism in the cellular uptake of silver nanoparticles verified by direct intra- and extracellular silver speciation analysis.

PubMed

Hsiao, I-Lun; Hsieh, Yi-Kong; Wang, Chu-Fang; Chen, I-Chieh; Huang, Yuh-Jeen

2015-03-17

The so-called "Trojan-horse" mechanism, in which nanoparticles are internalized within cells and then release high levels of toxic ions, has been proposed as a behavior in the cellular uptake of Ag nanoparticles (AgNPs). While several reports claim to have proved this mechanism by measuring AgNPs and Ag ions (I) in cells, it cannot be fully proven without examining those two components in both intra- and extracellular media. In our study, we found that even though cells take up AgNPs similarly to (microglia (BV-2)) or more rapidly than (astrocyte (ALT)) Ag (I), the ratio of AgNPs to total Ag (AgNPs+Ag (I)) in both cells was lower than that in outside media. It could be explained that H2O2, a major intracellular reactive oxygen species (ROS), reacts with AgNPs to form more Ag (I). Moreover, the major speciation of Ag (I) in cells was Ag(cysteine) and Ag(cysteine)2, indicating the possible binding of monomer cysteine or vital thiol proteins/peptides to Ag ions. Evidence we found indicates that the Trojan-horse mechanism really exists.

Simple and scalable growth of AgCl nanorods by plasma-assisted strain relaxation on flexible polymer substrates

NASA Astrophysics Data System (ADS)

Park, Jae Yong; Lee, Illhwan; Ham, Juyoung; Gim, Seungo; Lee, Jong-Lam

2017-06-01

Implementing nanostructures on plastic film is indispensable for highly efficient flexible optoelectronic devices. However, due to the thermal and chemical fragility of plastic, nanostructuring approaches are limited to indirect transfer with low throughput. Here, we fabricate single-crystal AgCl nanorods by using a Cl2 plasma on Ag-coated polyimide. Cl radicals react with Ag to form AgCl nanorods. The AgCl is subjected to compressive strain at its interface with the Ag film because of the larger lattice constant of AgCl compared to Ag. To minimize strain energy, the AgCl nanorods grow in the [200] direction. The epitaxial relationship between AgCl (200) and Ag (111) induces a strain, which leads to a strain gradient at the periphery of AgCl nanorods. The gradient causes a strain-induced diffusion of Ag atoms to accelerate the nanorod growth. Nanorods grown for 45 s exhibit superior haze up to 100% and luminance of optical device increased by up to 33%.

The irradiation influence on the properties of silver sulfide (Ag2S) colloidal nanoparticles

NASA Astrophysics Data System (ADS)

Rempel, S. V.; Kuznetsova, Yu. V.; Gerasimov, E. Yu.; Rempel', A. A.

2017-08-01

The aqueous solutions of different stability containing silver sulfide (Ag2S) nanoparticles are studied. The stable, transparent, and turbid solutions have been subjected to daylight for 7 months, to ultraviolet and laser irradiation, as well as to an electron beam. Solar radiation is found to favor the Ag2S reduction to Ag and/or the formation of Ag2S/Ag hybrid nanoparticles in the solution. At a high amount of hybrid nanoparticles, the exciton-plasmon interaction causes asymmetry in the absorption spectra. The exposure of Ag2S particles precipitated from the solution with the electron beam leads to the reversible growth of Ag threads. The possible exciton-plasmon interplay mechanisms in Ag2S/Ag hybrid nanoparticles are considered. The physical mechanisms of the changing Ag2S stoichiometry, the formation of metallic Ag and Ag2S/Ag hybrid nanoparticles are the generation of hot carriers and the energy transfer (exciton-plasmon interaction) in a metal-semiconductor hybrid nanosystem are elucidated, as well.

Inhibitory effect of Ti-Ag alloy on artificial biofilm formation.

PubMed

Nakajo, Kazuko; Takahashi, Masatoshi; Kikuchi, Masafumi; Takada, Yukyo; Okuno, Osamu; Sasaki, Keiichi; Takahashi, Nobuhiro

2014-01-01

Titanium-silver (Ti-Ag) alloy has been improved for machinability and mechanical properties, but its anti-biofilm properties have not been elucidated yet. Thus, this study aimed to evaluate the effects of Ti-Ag alloy on biofilm formation and bacterial viability in comparison with pure Ti, pure Ag and silver-palladium (Ag-Pd) alloy. Biofilm formation on the metal plates was evaluated by growing Streptococcus mutans and Streptococcus sobrinus in the presence of metal plates. Bactericidal activity was evaluated using a film contact method. There were no significant differences in biofilm formation between pure Ti, pure Ag and Ag-Pd alloy, while biofilm amounts on Ti-20% Ag and Ti-25% Ag alloys were significantly lower (p<0.05). In addition, Ti-Ag alloys and pure Ti were not bactericidal, although pure Ag and Ag-Pd alloy killed bacteria. These results suggest that Ti-20% Ag and Ti-25% Ag alloys are suitable for dental material that suppresses biofilm formation without disturbing healthy oral microflora.

Negligible shift of 3Ag- potential in longer-chain carotenoids as revealed by a single persistent peak of 3Ag-→1Ag- stimulated emission followed by 3Ag-←1Ag- transient-absorption

NASA Astrophysics Data System (ADS)

Li, Chunyong; Miki, Takeshi; Kakitani, Yoshinori; Koyama, Yasushi; Nagae, Hiroyoshi

2007-12-01

Upon excitation of lycopene, anhydrorhodovibrin or spirilloxanthin to the 1Bu+(0) state, stimulated emission followed by transient-absorption was observed as a single peak with the 3Ag-(0) energy that had been determined by measurement of resonance-Raman excitation profiles. This observation was explained in terms of negligible shift of the 3Ag- potential, in reference to the 1Ag- potential, where only the 3Ag-(υ)→1Ag-(υ) emission and the 3Ag-(υ)←1Ag-(υ) absorption become allowed during the vibrational relaxation of υ = 2 → 1 → 0, starting from the 3Ag-(2) level generated by diabatic internal conversion from the 1Bu+(0) level, in anhydrorhodovibrin, for example.

Structural and superionic properties of Ag+-rich ternary phases within the AgI-MI2 systems

NASA Astrophysics Data System (ADS)

Hull, S.; Keen, D. A.; Berastegui, P.

2002-12-01

The effects of temperature on the crystal structure and ionic conductivity of the compounds Ag2CdI4, Ag2ZnI4 and Ag3SnI5 have been investigated by powder diffraction and impedance spectroscopy techniques. varepsilon-Ag2CdI4 adopts a tetragonal crystal structure under ambient conditions and abrupt increases in the ionic conductivity are observed at 407(2), 447(3) and 532(4) K, consistent with the sequence of transitions varepsilon-Ag2CdI 4 rightarrow beta-Ag2CdI 4 + beta-AgI + CdI2 rightarrow alpha-AgI + CdI2 rightarrow alpha-Ag2CdI4. Hexagonal beta-Ag2CdI4 is metastable at ambient temperature. The ambient-temperature beta phase of Ag2ZnI4 is orthorhombic and the structures of beta-Ag2CdI4 and beta-Ag2ZnI4 can, respectively, be considered as ordered derivatives of the wurtzite (beta) and zincblende (gamma) phases of AgI. On heating Ag2ZnI4, there is a 12-fold increase in ionic conductivity at 481(1) K and a further eightfold increase at 542(3) K. These changes result from decomposition of beta-Ag2ZnI4 into alpha-AgI + ZnI2, followed by the appearance of superionic alpha-Ag2ZnI4 at the higher temperature. The hexagonal crystal structure of alpha-Ag2ZnI4 is a dynamically disordered counterpart to the beta modification. Ag3SnI5 is only stable at temperatures in excess of 370(3) K and possesses a relatively high ionic conductivity (sigma approx 0.19Omega-1 cm-1 at 420 K) due to dynamic disorder of the Ag+ and Sn2+ within a cubic close packed I- sublattice. The implications of these findings for the wider issue of high ionic conductivity in AgI-MI2 compounds is discussed, with reference to recently published studies of Ag4PbI6 and Ag2HgI4 and new data for the temperature dependence of the ionic conductivity of the latter compound.

Progressive effects of silver nanoparticles on hormonal regulation of reproduction in male rats

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

Dziendzikowska, K., E-mail: k.dziendzikowska@gmail

The growing use of silver nanoparticles (AgNPs) in various applications, including consumer, agriculture and medicine products, has raised many concerns about the potential risks of nanoparticles (NPs) to human health and the environment. An increasing body of evidence suggests that AgNPs may have adverse effects of humans, thus the aim of this study was to investigate the effects of AgNPs on the male reproductive system. Silver particles (20 nm AgNPs (groups Ag I and Ag II) and 200 nm Ag sub-micron particles (SPs) (group Ag III)) were administered intravenously to male Wistar rats at a dose of 5 (groups Agmore » I and Ag III) or 10 (group Ag II) mg/kg of body weight. The biological material was sampled 24 h, 7 days and 28 days after injection. The obtained results revealed that the AgNPs had altered the luteinising hormone concentration in the plasma and the sex hormone concentration in the plasma and testes. Plasma and intratesticular levels of testosterone and dihydrotestosterone were significantly decreased both 7 and 28 days after treatment. No change in the prolactin and sex hormone-binding globulin concentration was observed. Exposure of the animals to AgNPs resulted in a considerable decrease in 5α-reductase type 1 and the aromatase protein level in the testis. Additionally, expression analysis of genes involved in steroidogenesis and the steroids metabolism revealed significant down-regulation of Star, Cyp11a1, Hsd3b1, Hsd17b3 and Srd5a1 mRNAs in AgNPs/AgSPs-exposed animals. The present study demonstrates the potential adverse effect on the hormonal regulation of the male reproductive function following AgNP/AgSP administration, in particular alterations of the sex steroid balance and expression of genes involved in steroidogenesis and the steroids metabolism. - Highlights: • Assessment of the toxic effects of AgNPs/AgSPs on the regulation of male reproductive function • AgNP −/AgSP-induced alterations of sex steroid status in male Wistar rats. • Regulation of male reproductive function is differently modulated by AgNPs and AgSPs. • Endocrine-mediated toxicity of AgNPs/AgSPs increased over time. • AgNPs/AgSPs alter male reproductive function regulation at the transcriptional level.« less

Linearized hepatitis B surface antigen and hepatitis B core-related antigen in the natural history of chronic hepatitis B.

PubMed

Seto, W-K; Wong, D K-H; Fung, J; Huang, F-Y; Liu, K S-H; Lai, C-L; Yuen, M-F

2014-11-01

Changes in two novel HBV serological markers, linearized hepatitis B surface antigen (HQ-HBsAg) and hepatitis B core-related antigen (HBcrAg), in the natural history of chronic hepatitis B (CHB) have not been well characterized. Serum HQ-HBsAg and HBcrAg levels of 404 Asian treatment-naïve CHB patients were analysed in a cross-sectional manner. Patients were categorized into five groups: immune tolerant (IT group, n=52), immune clearance (IC group, n=105), hepatitis B e antigen (HBeAg)-negative hepatitis (ENH group, n=97), HBeAg-negative quiescent group (ENQ group, n=95) and CHB with hepatitis B surface antigen (HBsAg) seroclearance (SC group, n=55). HQ-HBsAg and HBcrAg were measured and correlated with HBV DNA, HBsAg, HBV genotype and clinical parameters. HQ-HBsAg showed good correlation with HBsAg, especially in the ENQ group (r=0.874, p<0.001). Correlation of HQ-HBsAg with HBV DNA was less prominent and weakest in the ENH group (r=0.268, p 0.008). HBcrAg correlated best with HBV DNA in the ENQ group (r=0.537, p<0.001). In the ENQ group, 42.1% of patients had undetectable HBcrAg; this subgroup of patients, when compared with those with detectable HBcrAg, had significantly lower median HBV DNA (3.17/4.48 log IU/mL, p<0.001) and HBsAg (5.05/5.96 log mIU/mL, p<0.001) levels. Forty per cent of the SC group patients had detectable HQ-HBsAg and/or HBcrAg up to 42 months after HBsAg seroclearance. When comparing anti-HBs positivity and median time after HBsAg seroclearance in the SC group with and without detectable HQ-HBsAg/HBcrAg, there was no significant difference (22.7% and 36.4%, respectively, p 0.284, and 76.5 and 93.2 months, respectively, p 0.245). HQ-HBsAg and HBcrAg showed unique patterns of distribution throughout the five disease phases of CHB, including high detectability rates after HBsAg seroclearance, opening up different possibilities for their applicability. © 2014 The Authors Clinical Microbiology and Infection © 2014 European Society of Clinical Microbiology and Infectious Diseases.

Oil-in-Water Self-Assembled Synthesis of Ag@AgCl Nano-Particles on Flower-like Bi2O2CO3 with Enhanced Visible-Light-Driven Photocatalytic Activity

PubMed Central

Lin, Shuanglong; Liu, Li; Liang, Yinghua; Cui, Wenquan; Zhang, Zisheng

2016-01-01

In this work, a series of novel flower-like Ag@AgCl/Bi2O2CO3 were prepared by simple and feasible oil-in-water self-assembly processes. The phase structures of as-prepared samples were examined by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS), X-ray fluorescence spectrometer (XRF), etc. The characterization results indicated that the presence of Ag@AgCl did not affect the crystal structure, but exerted a great influence on the photocatalytic activity of Bi2O2CO3 and enhanced the absorption band of pure Bi2O2CO3. The photocatalytic activities of the Ag@AgCl/Bi2O2CO3 samples were determined by photocatalytic degradation of methylene blue (MB) under visible light irradiation. The Ag@AgCl (10 wt %)/Bi2O2CO3 composite showed the highest photocatalytic activity, degrading 97.9% MB after irradiation for 20 min, which is over 1.64 and 3.66 times faster than that of pure Ag@AgCl (calculated based on the equivalent Ag@AgCl content in Ag@AgCl (10 wt %)/Bi2O2CO3) and pure Bi2O2CO3, respectively. Bisphenol A (BPA) was also degraded to further prove the degradation ability of Ag@AgCl/Bi2O2CO3. Photocurrent studies indicated that the recombination of photo-generated electron–hole pairs was decreased effectively due to the formation of heterojunctions between flower-like Bi2O2CO3 and Ag@AgCl nanoparticles. Trapping experiments indicated that O2−, h+ and Cl° acted as the main reactive species for MB degradation in the present photocatalytic system. Furthermore, the cycling experiments revealed the good stability of Ag@AgCl/Bi2O2CO3 composites. Based on the above, a photocatalytic mechanism for the degradation of organic compounds over Ag@AgCl/Bi2O2CO3 was proposed. PMID:28773607

WIYN OPEN CLUSTER STUDY. XLVIII. THE HARD-BINARY POPULATION OF NGC 188

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

Geller, Aaron M.; Mathieu, Robert D., E-mail: a-geller@northwestern.edu, E-mail: mathieu@astro.wisc.edu

2012-08-15

We present an in-depth study of the hard-binary population of the old (7 Gyr) open cluster NGC 188. Utilizing 85 spectroscopic binary orbits out of a complete sample of 129 detected binary members, we study the cluster binary frequency and the distributions of binary orbital elements among the main-sequence (MS), giant, and blue straggler (BS) populations. The results are derived from our ongoing radial velocity survey of the cluster, which spans in magnitude from the brightest stars in the cluster to V = 16.5 (about 1.1-0.9 M{sub Sun} ), and extends to a projected radius of 17 pc ({approx}13 coremore » radii). Our detectable binaries have periods ranging from a few days to of order 10{sup 4} days, and thus are hard binaries that dynamically power the cluster. The MS solar-type hard binaries in NGC 188 are nearly indistinguishable from similar binaries in the Galactic field. We observe a global solar-type MS hard-binary frequency in NGC 188 of 23% {+-} 2%, which when corrected for incompleteness results in a frequency of 29% {+-} 3% for binaries with periods less than 10{sup 4} days. For MS hard binaries in the cluster, we observe a log-period distribution that rises toward our detection limit, a roughly Gaussian eccentricity distribution centered on e = 0.35 (for binaries with periods longer than the circularization period), and a secondary-mass distribution that rises toward lower-mass companions. Importantly, the NGC 188 BS binaries show significantly different characteristics than the solar-type MS binaries in NGC 188. We observe a BS hard-binary frequency of 76% {+-} 19%, three times that of the MS. The excess of this binary frequency over the normal MS binary frequency is valid at the >99% confidence level. Furthermore, the BS binary eccentricity-log-period distribution is distinct from that of the MS at the 99% confidence level, with the majority of the BS binaries having periods of order 1000 days and lower eccentricities. The secondary-mass distribution for these long-period BS binaries is narrow and peaked with a mean value of about 0.5 M{sub Sun }. Predictions for mass-transfer products are most closely consistent with the binary properties of these NGC 188 BSs, which comprise two-thirds of the BS population. Additionally, we compare the NGC 188 binaries to those evolved within the sophisticated Hurley et al. (2005) N-body open cluster simulation. The MS hard-binary population predicted by the simulation is significantly different from the MS hard-binary population observed in NGC 188, in frequency and distributions of period and eccentricity. Many of these differences result from the adopted initial binary population, while others reflect on the physics used in the simulation (e.g., tidal circularization). Additional simulations with initial conditions that are better motivated by observations are necessary to properly investigate the dynamical evolution of a rich binary population in open clusters like NGC 188.« less

Coevolution of Binaries and Circumbinary Gaseous Disks

NASA Astrophysics Data System (ADS)

Fleming, David; Quinn, Thomas R.

2018-04-01

The recent discoveries of circumbinary planets by Kepler raise questions for contemporary planet formation models. Understanding how these planets form requires characterizing their formation environment, the circumbinary protoplanetary disk, and how the disk and binary interact. The central binary excites resonances in the surrounding protoplanetary disk that drive evolution in both the binary orbital elements and in the disk. To probe how these interactions impact both binary eccentricity and disk structure evolution, we ran N-body smooth particle hydrodynamics (SPH) simulations of gaseous protoplanetary disks surrounding binaries based on Kepler 38 for 10^4 binary orbital periods for several initial binary eccentricities. We find that nearly circular binaries weakly couple to the disk via a parametric instability and excite disk eccentricity growth. Eccentric binaries strongly couple to the disk causing eccentricity growth for both the disk and binary. Disks around sufficiently eccentric binaries strongly couple to the disk and develop an m = 1 spiral wave launched from the 1:3 eccentric outer Lindblad resonance (EOLR). This wave corresponds to an alignment of gas particle longitude of periastrons. We find that in all simulations, the binary semi-major axis decays due to dissipation from the viscous disk.

Functional paper-based SERS substrate for rapid and sensitive detection of Sudan dyes in herbal medicine

NASA Astrophysics Data System (ADS)

Wu, Mianmian; Li, Pan; Zhu, Qingxia; Wu, Meiran; Li, Hao; Lu, Feng

2018-05-01

There has been an increasing demand for rapid and sensitive techniques for the identification of Sudan compounds that emerged as the most often illegally added fat-soluble dyes in herbal medicine. In this report, we have designed and fabricated a functionalized filter paper consisting of gold nanorods (GNRs) and mono-6-thio-cyclodextrin (HS-β-CD) as a surface-enhanced Raman spectroscopy (SERS) substrate, in which the GNR provides sufficient SERS enhancement, and the HS-β-CD with strong chemical affinity toward GNR provides the inclusion compound to capture hydrophobic molecules. Moreover, the CD-GNR were uniformly assembled on filter paper cellulose through the electrostatic adsorption and hydrogen bond, so that the CD-GNR paper-based SERS substrate (CD-GNR-paper) demonstrated higher sensitivity for the determination of Sudan III (0.1 μM) and Sudan IV (0.5 μM) than GNRs paper-based SERS substrate (GNR-paper), with high stability after the storage in the open air for 90 days. Importantly, CD-GNR-paper can effectively collect the Sudan dyes from illegally adulterated onto samples of Resina Draconis with a simple operation, further open up new exciting opportunity for SERS detection of more compounds illegally added with high sensitivity and fast signal responses.

Differential Phytotoxic Impact of Plant Mediated Silver Nanoparticles (AgNPs) and Silver Nitrate (AgNO3) on Brassica sp.

PubMed Central

Vishwakarma, Kanchan; Shweta; Upadhyay, Neha; Singh, Jaspreet; Liu, Shiliang; Singh, Vijay P.; Prasad, Sheo M.; Chauhan, Devendra K.; Tripathi, Durgesh K.; Sharma, Shivesh

2017-01-01

Continuous formation and utilization of nanoparticles (NPs) have resulted into significant discharge of nanosized particles into the environment. NPs find applications in numerous products and agriculture sector, and gaining importance in recent years. In the present study, silver nanoparticles (AgNPs) were biosynthesized from silver nitrate (AgNO3) by green synthesis approach using Aloe vera extract. Mustard (Brassica sp.) seedlings were grown hydroponically and toxicity of both AgNP and AgNO3 (as ionic Ag+) was assessed at various concentrations (1 and 3 mM) by analyzing shoot and root length, fresh mass, protein content, photosynthetic pigments and performance, cell viability, oxidative damage, DNA degradation and enzyme activities. The results revealed that both AgNPs and AgNO3 declined growth of Brassica seedlings due to enhanced accumulation of AgNPs and AgNO3 that subsequently caused severe inhibition in photosynthesis. Further, the results showed that both AgNPs and AgNO3 induced oxidative stress as indicated by histochemical staining of superoxide radical and hydrogen peroxide that was manifested in terms of DNA degradation and cell death. Activities of antioxidants, i.e., ascorbate peroxidase (APX) and catalase (CAT) were inhibited by AgNPs and AgNO3. Interestingly, damaging impact of AgNPs was lesser than AgNO3 on Brassica seedlings which was due to lesser accumulation of AgNPs and better activities of APX and CAT, which resulted in lesser oxidative stress, DNA degradation and cell death. The results of the present study showed differential impact of AgNPs and AgNO3 on Brassica seedlings, their mode of action, and reasons for their differential impact. The results of the present study could be implied in toxicological research for designing strategies to reduce adverse impact of AgNPs and AgNO3 on crop plants. PMID:29075270

Functional Analysis of the α-1,3-Glucan Synthase Genes agsA and agsB in Aspergillus nidulans: AgsB Is the Major α-1,3-Glucan Synthase in This Fungus

PubMed Central

Yoshimi, Akira; Sano, Motoaki; Inaba, Azusa; Kokubun, Yuko; Fujioka, Tomonori; Mizutani, Osamu; Hagiwara, Daisuke; Fujikawa, Takashi; Nishimura, Marie; Yano, Shigekazu; Kasahara, Shin; Shimizu, Kiminori; Yamaguchi, Masashi; Kawakami, Kazuyoshi; Abe, Keietsu

2013-01-01

Although α-1,3-glucan is one of the major cell wall polysaccharides in filamentous fungi, the physiological roles of α-1,3-glucan remain unclear. The model fungus Aspergillus nidulans possesses two α-1,3-glucan synthase (AGS) genes, agsA and agsB. For functional analysis of these genes, we constructed several mutant strains in A. nidulans: agsA disruption, agsB disruption, and double-disruption strains. We also constructed several CagsB strains in which agsB expression was controlled by the inducible alcA promoter, with or without the agsA-disrupting mutation. The agsA disruption strains did not show markedly different phenotypes from those of the wild-type strain. The agsB disruption strains formed dispersed hyphal cells under liquid culture conditions, regardless of the agsA genetic background. Dispersed hyphal cells were also observed in liquid culture of the CagsB strains when agsB expression was repressed, whereas these strains grew normally in plate culture even under the agsB-repressed conditions. Fractionation of the cell wall based on the alkali solubility of its components, quantification of sugars, and 13C-NMR spectroscopic analysis revealed that α-1,3-glucan was the main component of the alkali-soluble fraction in the wild-type and agsA disruption strains, but almost no α-1,3-glucan was found in the alkali-soluble fraction derived from either the agsB disruption strain or the CagsB strain under the agsB-repressed conditions, regardless of the agsA genetic background. Taken together, our data demonstrate that the two AGS genes are dispensable in A. nidulans, but that AgsB is required for normal growth characteristics under liquid culture conditions and is the major AGS in this species. PMID:23365684

Ab initio Study of Ag-Based Fluoroperovskite AgMF3 (M = Co and Ni) Compounds

NASA Astrophysics Data System (ADS)

Mubarak, A. A.

2018-01-01

Ab initio calculations of Ag-based fluoroperovskite AgMF3 (M = Co and Ni) compounds are investigated using the full-potential linearized augmented plane wave method. Wien2k and BoltzTrap codes are used to calculate the different physical properties. The structural parameters of the present compounds are within reasonable agreement with previous calculations. This study shows that AgCoF3 and AgNiF3 are anisotropic, ductile, mechanically and thermodynamically stable compounds, where AgCoF3 is found to be stiffer and less compressible than AgNiF3. The spin-polarized electronic band structure illustrates that AgCoF3 is metallic, while AgNiF3 is a semiconductor with indirect (M-D) band gap energy of 0.43 eV. The bonding force between atoms is found to be mainly ionic with some covalent nature. The total magnetic moment of AgCoF3 (3.04 μ B) is found to be higher than that calculated for AgNiF3 (2.00 μ B). Using the magnetic susceptibility calculations, AgCoF3 is classified as antiferromagnetic, whereas AgNiF3 is a ferromagnetic compound. The calculated static refractive index of AgCoF3 (3.85) and AgNiF3 (3.60) is inversely proportional with the energy band gap. Suitable applications are predicted for AgCoF3 and AgNiF3 based on their absorption and reflection properties. Furthermore, beneficial thermoelectric applications are expected for the present compounds due to their large Seebeck coefficient ( S_{{{{AgCoF}}_{ 3} }} = 2.92 × 103 μ {V/K} {and} S_{{{{AgNiF}}3 }} = 2.84 × 103 μ {V/K} ) and their thermoelectric power factor with respect to relaxation time ( S2 σ /t_{{AgNiF3 }} = 1.11 × 109 {W/K}^{ 2} {and} S2 σ /t_{{AgNiF3 }} = 1.28 × 10^{11} {W/K}^{ 2} ).

Effect of cysteine and humic acids on bioavailability of Ag from Ag nanoparticles to a freshwater snail

USGS Publications Warehouse

Luoma, Samuel N.; Tasha Stoiber,; Croteau, Marie-Noele; Isabelle Romer,; Ruth Merrifeild,; Lead, Jamie

2016-01-01

Metal-based engineered nanoparticles (NPs) will undergo transformations that will affect their bioavailability, toxicity and ecological risk when released to the environment, including interactions with dissolved organic material. The purpose of this paper is to determine how interactions with two different types of organic material affect the bioavailability of silver nanoparticles (AgNPs). Silver uptake rates by the pond snail Lymnaea stagnalis were determined after exposure to 25 nmol l-1 of Ag as PVP AgNPs, PEG AgNPs or AgNO3, in the presence of either Suwannee River humic acid or cysteine, a high-affinity thiol-rich organic ligand. Total uptake rate of Ag from the two NPs was either increased or not strongly affected in the presence of 1 – 10 mg 1-1 humic acid. Humic substances contain relatively few strong ligands for Ag explaining their limited effects on Ag uptake rate. In contrast, Ag uptake rate was substantially reduced by cysteine. Three components of uptake from the AgNPs were quantified in the presence of cysteine using a biodynamic modeling approach: uptake of dissolved Ag released by the AgNPs, uptake of a polymer or large (>3kD) Ag-cysteine complex and uptake of the nanoparticle itself. Addition of 1:1 Ag:cysteine reduced concentrations of dissolved Ag, which contributed to, but did not fully explain the reductions in uptake. A bioavailable Ag-cysteine complex (> 3kD) appeared to be the dominant avenue of uptake from both PVP AgNPs and PEG AgNPs in the presence of cysteine. Quantifying the different avenues of uptake sets the stage for studies to assess toxicity unique to NPs.

W{sub 18}O{sub 49} nanorods decorated with Ag/AgCl nanoparticles as highly-sensitive gas-sensing material and visible-light-driven photocatalyst

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

Sun Shibin; Chang Xueting, E-mail: xuetingchang@yahoo.cn; Dong Lihua

2011-08-15

A novel gas-sensing material and photocatalyst was successfully obtained by decorating Ag/AgCl nanoparticles on the W{sub 18}O{sub 49} nanorods through a clean photochemical route. The as-prepared samples were characterized using combined techniques of X-ray diffractometry, electron microscopy, energy dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy. Gas-sensing measurements indicate that the Ag/AgCl/W{sub 18}O{sub 49} NRs sensors exhibit superior reducing gas-sensing properties to those of bare W{sub 18}O{sub 49} NRs, and they are highly selective and sensitive to NH{sub 3}, acetone, and H{sub 2}S with short response and recovery times. The Ag/AgCl/W{sub 18}O{sub 49} NRs photocatlysts also possess higher photocatalytic performance thanmore » bare W{sub 18}O{sub 49} NRs for degradation of methyl orange under simulated sunlight irradiation. Possible mechanisms concerning the enhancement of gas-sensing and photocatalytic activities of the Ag/AgCl/W{sub 18}O{sub 49} NRs composite were proposed. - Graphical Abstract: The Ag/AgCl nanoparticles adhered well to the W{sub 18}O{sub 49} nanorod. The Ag could act as transfer center of the photoexcited carriers, prohibiting their recombinations in both W{sub 18}O{sub 49} and AgCl. Highlights: > Ag/AgCl/W{sub 18}O{sub 49} NRs were successfully obtained via a clean photochemical route. > The Ag/AgCl nanoparticles decorated on the W{sub 18}O{sub 49} NRs possessed cladding structure. > The Ag/AgCl/W{sub 18}O{sub 49} NRs exhibited excellent gas-sensing and photocatalytic properties.« less

Mussel-inspired green synthesis of polydopamine-Ag-AgCl composites with efficient visible-light-driven photocatalytic activity.

PubMed

Cai, Aijun; Wang, Xiuping; Guo, Aiying; Chang, Yongfang

2016-09-01

Polydopamine-Ag-AgCl composites (PDA-Ag-AgCl) were synthesized using a mussel-inspired method at room temperature, where PDA acts as a reducing agent to obtain the noble Ag nanoparticles from a precursor. The morphologies and structures of the as-prepared PDA-Ag-AgCl were characterized by several techniques including field emission scanning electron microscopy (FESEM), transmission electron microscopy (SEM), Raman spectra, and X-Ray photoelectron spectrum (XPS). The morphological observation depicts formation of nanoparticles with various micrometer size diameters and surface XPS analysis shows presence of various elements including Ag, N, Cl, and O. The enhanced absorbance of the PDA-Ag-AgCl particles in the visible light region is confirmed through UV-Vis diffuse reflectance spectra (DRS), and the charge transfer is demonstrated by photoluminescence (PL) and photocurrent response. The synthesized PDA-Ag-AgCl composites could be used as visible-light-driven photocatalysts for the degradation of Rhodamine B. The elevated photocatalytic activity is ascribed to the effective charge transfer from plasmon-excited Ag to AgCl that can improve the efficiency of the charge separation during the photocatalytic reaction. Furthermore, differences in the photocatalytic performance among the different PDA-Ag-AgCl composites are noticed that could be attributed to the Brunauer-Emmett-Teller (BET) specific surface area, which benefits to capture the visible light efficiently. The PDA-Ag-AgCl exhibits excellent stability without a significant loss in activity after 5cycles. The proposed method is low-cost and environmentally friendly, hence a promising new way to fabricate plasmon photocatalysts. Copyright © 2016. Published by Elsevier B.V.

Incorporation of silver nanoparticles on the surface of orthodontic microimplants to achieve antimicrobial properties

PubMed Central

Venugopal, Adith; Muthuchamy, Nallal; Tejani, Harsh; Gopalan, Anantha-Iyengar; Lee, Kwang-Pill; Lee, Heon-Jin

2017-01-01

Objective Microbial aggregation around dental implants can lead to loss/loosening of the implants. This study was aimed at surface treating titanium microimplants with silver nanoparticles (AgNPs) to achieve antibacterial properties. Methods AgNP-modified titanium microimplants (Ti-nAg) were prepared using two methods. The first method involved coating the microimplants with regular AgNPs (Ti-AgNP) and the second involved coating them with a AgNP-coated biopolymer (Ti-BP-AgNP). The topologies, microstructures, and chemical compositions of the surfaces of the Ti-nAg were characterized by scanning electron microscopy (SEM) equipped with energy-dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS). Disk diffusion tests using Streptococcus mutans, Streptococcus sanguinis, and Aggregatibacter actinomycetemcomitans were performed to test the antibacterial activity of the Ti-nAg microimplants. Results SEM revealed that only a meager amount of AgNPs was sparsely deposited on the Ti-AgNP surface with the first method, while a layer of AgNP-coated biopolymer extended along the Ti-BP-AgNP surface in the second method. The diameters of the coated nanoparticles were in the range of 10 to 30 nm. EDS revealed 1.05 atomic % of Ag on the surface of the Ti-AgNP and an astounding 21.2 atomic % on the surface of the Ti-BP-AgNP. XPS confirmed the metallic state of silver on the Ti-BP-AgNP surface. After 24 hours of incubation, clear zones of inhibition were seen around the Ti-BP-AgNP microimplants in all three test bacterial culture plates, whereas no antibacterial effect was observed with the Ti-AgNP microimplants. Conclusions Titanium microimplants modified with Ti-BP-AgNP exhibit excellent antibacterial properties, making them a promising implantable biomaterial. PMID:28127534

Effects of silver nanoparticles on soil enzyme activities with and without added organic matter.

PubMed

Peyrot, Caroline; Wilkinson, Kevin J; Desrosiers, Mélanie; Sauvé, Sébastien

2014-01-01

The effects of silver nanoparticles (AgNPs) on terrestrial ecosystems need to be better understood and assessed. Cationic silver (Ag+) has well-documented toxicity against bacteria, but it is not clear what will be the effect of nanoscale Ag. In the present study, the potential effects of AgNPs were investigated in soils by measuring activity of the enzymes phosphomonoesterase, arylsulfatase, β-D-glucosidase, and leucine-aminopeptidase. The toxicity of AgNPs was compared with that of ionic Ag, and the ameliorating effects of soil organic matter were evaluated. To this end, 2 soils with different organic matter contents were artificially contaminated with either AgNPs or Ag-acetate at equivalent total Ag concentrations. In general, enzyme activities were inhibited as a function of the Ag concentration in the soil. In the AgNP exposures, only a small fraction of the AgNP was actually truly dissolved (found in the <1-nm fraction), suggesting that the particulate forms of AgNPs resulted in a significant inhibition of soil enzymes. The addition of organic matter to the soils appeared to enhance enzyme activities; however, the mechanism of organic matter action is not clear given that dissolved Ag concentrations were similar in both the organic-matter–amended and unamended soils. The present study shows that the AgNP produces significant negative effects on the soil enzyme activities tested. The Ag chemical speciation measurements suggested that the AgNP caused greater toxic effects to the soil enzymes at the low Ag concentrations. For the larger concentrations of total soil Ag, causes of the negative effects on enzyme activities are less obvious but suggest that colloidal forms of Ag play a role.

Biopolymer mediated nanoparticles synthesized from Adenia hondala for enhanced tamoxifen drug delivery in breast cancer cell line

NASA Astrophysics Data System (ADS)

Varadharajaperumal, Pradeepa; Subramanian, Balakumar; Santhanam, Amutha

2017-09-01

Silver nanoparticles (AgNPs) are an important class of nanomaterials, which have used as antimicrobial and disinfectant agents due to their detrimental effect on target cells. In the present study it was explored to deliver a novel tamoxifen drug system that can be used in breast cancer treatment, based on chitosan coated silver nanoparticles on MCF-7 human breast cancer cells. AgNPs synthesized from Adenia hondala tuber extract were used to make the chitosan coated AgNPs (Ch-AgNPs), in which the drug tamoxifen was loaded on chitosan coated silver nanoparticles (Tam-Ch-AgNPs) to construct drug loaded nanoparticles as drug delivery system. The morphology and characteristics of the Ch-AgNPs were investigated by UV, FTIR, zeta potential and FESEM. Furthermore, the toxicity of AgNPs, Ch-AgNPs, Tam-Ch-AgNPs was evaluated through cell viability, lactate dehydrogenase leakage, reactive oxygen species generation, caspase-3, DNA laddering, and TUNEL assay in human breast cancer cells (MCF-7) and HBL-100 continuous cell line as a control. Treatment of cancer cells with various concentrations of AgNPs, Ch-AgNPs, Tam-Ch-AgNPs for 24 h revealed that Tam-Ch-AgNPs could inhibit cell viability and induce significant membrane leakage in a dose-dependent manner. Cells exposed to Tam-Ch-AgNPs showed increased reactive oxygen species and hydroxyl radical production when compared to AgNPs, Ch-AgNPs. Furthermore, the apoptotic effects of AgNPs, Ch-AgNPs, Tam-Ch-AgNPs were confirmed by activation of caspase-3 and DNA nuclear fragmentation. The present findings suggest that Tam-Ch-AgNPs could contribute to the development of a suitable anticancer drug delivery.

Silver speciation and release in commercial antimicrobial textiles as influenced by washing.

PubMed

Lombi, Enzo; Donner, Erica; Scheckel, Kirk G; Sekine, Ryo; Lorenz, Christiane; Von Goetz, Natalie; Nowack, Bernd

2014-09-01

The use of nanoscale Ag in textiles is one the most often mentioned uses of nano-Ag. It has previously been shown that significant amounts of the Ag in the textiles are released upon washing. However, the form of Ag present in the textiles remains largely unknown as product labelling is insufficient. The aim of this study was therefore to investigate the solid phase speciation of Ag in original and washed silver textiles using XANES. The original Ag speciation in the textiles was found to vary greatly between different materials with Ag(0), AgCl, Ag2S, Ag-phosphate, ionic Ag and other species identified. Furthermore, within the same textile a number of different species were found to coexist. This is likely due to a combination of factors such as the synthesis processes at industrial scale and the possible reaction of Ag with atmospheric gases. Washing with two different detergents resulted in marked changes in Ag-speciation. For some textiles the two detergents induced similar transformation, in other textiles they resulted in very different Ag species. This study demonstrates that in functional Ag textiles a variety of different Ag species coexist before and after washing. These results have important implications for the risk assessment of Ag textiles because they show that the metallic Ag is only one of the many silver species that need to be considered. Copyright © 2014 Elsevier Ltd. All rights reserved.

The Antimicrobial Properties of Silver Nanoparticles in Bacillus subtilis Are Mediated by Released Ag+ Ions

PubMed Central

Hsueh, Yi-Huang; Lin, Kuen-Song; Ke, Wan-Ju; Hsieh, Chien-Te; Chiang, Chao-Lung; Tzou, Dong-Ying; Liu, Shih-Tung

2015-01-01

The superior antimicrobial properties of silver nanoparticles (Ag NPs) are well-documented, but the exact mechanisms underlying Ag-NP microbial toxicity remain the subject of intense debate. Here, we show that Ag-NP concentrations as low as 10 ppm exert significant toxicity against Bacillus subtilis, a beneficial bacterium ubiquitous in the soil. Growth arrest and chromosomal DNA degradation were observed, and flow cytometric quantification of propidium iodide (PI) staining also revealed that Ag-NP concentrations of 25 ppm and above increased membrane permeability. RedoxSensor content analysis and Phag-GFP expression analysis further indicated that reductase activity and cytosolic protein expression decreased in B. subtilis cells treated with 10–50 ppm of Ag NPs. We conducted X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses to directly clarify the valence and fine structure of Ag atoms in B. subtilis cells placed in contact with Ag NPs. The results confirmed the Ag species in Ag NP-treated B. subtilis cells as Ag2O, indicating that Ag-NP toxicity is likely mediated by released Ag+ ions from Ag NPs, which penetrate bacterial cells and are subsequently oxidized intracellularly to Ag2O. These findings provide conclusive evidence for the role of Ag+ ions in Ag-NP microbial toxicity, and suggest that the impact of inappropriately disposed Ag NPs to soil and water ecosystems may warrant further investigation. PMID:26669836

One-step microwave-assisted colloidal synthesis of hybrid silver oxide/silver nanoparticles: characterization and catalytic study

NASA Astrophysics Data System (ADS)

Prakoso, S. P.; Taufik, A.; Saleh, R.

2017-04-01

This study reports the characterization and catalytic activities of silver-oxide/silver nanoparticles (Ag2O/Ag NPs) synthesized by microwave-assisted colloidal method in the presence of anionic sodium dodecyl sulfate (SDS) surfactant. To promote different contents of silver in silver oxide, the volume ratio (VR) of ethylene glycol (EG) was varied (VR: 10% to 14%) in relation to the total volume of distilled water solvent. The plasmonic resonance of Ag2O/Ag NPs could be detected around a wavelength of 350 nm, and it is suggested that Ag2O/Ag NPs were successfully formed in the colloid solution following exposure to microwaves. Additionally, the growth rate for each crystal phase within Ag2O and Ag was influenced by an increase of EG as revealed by x-ray diffraction patterns. The morphology, average diameter, and uniformity of Ag2O/Ag NPs were studied simultaneously by transmission electron microscopy. Infrared absorption measurement of Ag2O/Ag NPs confirmed the existence of SDS surfactant as a protective agent. Based on the characterization data, Ag2O/Ag NPs synthesized using this technique exhibited good properties, with high-yield production of NPs. The photocatalytic experiments demonstrate the key role of the crystal phase of Ag2O/Ag NPs in photocatalytic efficiency.

Comparative synthesis and antimicrobial action of silver nanoparticles and silver nitrate

NASA Astrophysics Data System (ADS)

Mosselhy, Dina A.; El-Aziz, Mohamed Abd; Hanna, Magdy; Ahmed, Mohamed A.; Husien, Mona M.; Feng, Qingling

2015-12-01

The high wave of antibiotic bacterial resistance has addressed an importance for administration of different antibacterial agents, as silver nanoparticles (Ag NPs). However, many investigators still suffer conflict in the mechanistic antimicrobial action of Ag NPs and Ag+ ions. In this regard, our study investigated the comparative antimicrobial action of different sizes of Ag NPs as 8 (nAg1) and 29 (nAg2) nm, in comparison with silver nitrate (AgNO3) against five different bacterial species; Aeromonas hydrophila ( A. hydrophila), Pseudomonas putida ( Ps. putida), Escherichia coli ( E. coli), Staphylococcus aureus ( S. aureus), and Bacillus subtilis ( B. subtilis) using agar diffusion assay and minimum inhibitory concentration (MIC). The key role of the size of nanomaterials was detected, as the smaller Ag NPs (nAg1) showed more antimicrobial action than the larger particles. Transmission electron microscopy (TEM) studies demonstrated the different mechanistic antibacterial actions of Ag NPs and AgNO3. The effect of combining Ag NPs with antibiotics was also investigated. Synergistic effect of combining Ag NPs with ampicillin was detected against S. aureus, in a size-dependent manner as well. To summarize, our results point towards the major role played by the size of Ag NPs in their antimicrobial effects and the different toxic mechanisms of actions induced by Ag NPs and AgNO3.

Effect of Silver Dopants on the ZnO Thin Films Prepared by a Radio Frequency Magnetron Co-Sputtering System

PubMed Central

Liu, Fang-Cheng; Li, Jyun-Yong; Chen, Tai-Hong; Chang, Chun-How; Lee, Ching-Ting; Hsiao, Wei-Hua; Liu, Day-Shan

2017-01-01

Ag-ZnO co-sputtered films at various atomic ratios of Ag (Ag/(Ag + Zn) at.%) were prepared by a radio frequency magnetron cosputtering system, using the co-sputtered targets of Ag and ZnO. The activation of the Ag acceptors (AgZn) and the formation of the Ag aggregations (Ag0) in the ZnO matrix were investigated from XRD, Raman scattering, and XPS measurements. The Ag-ZnO co-sputtered film behaving like a p-type conduction was achievable after annealing at 350 °C under air ambient for 1 h. PMID:28773159

As-synthesis of nanostructure AgCl/Ag/MCM-41 composite

NASA Astrophysics Data System (ADS)

Sohrabnezhad, Sh.; Pourahmad, A.

2012-02-01

In this work, we present the simple synthetic route for silver chloride/silver nanoparticles (AgCl/Ag-NPs) using as-synthesis method. The structure, composition and optical properties of such material were investigated by transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy (UV-vis DRS), X-ray diffraction (XRD) and FTIR. Powder X-ray diffraction showed that when AgNO 3 content is below 0.1 wt.% in synthetic gel, the guest AgCl/Ag-NPs is formed on the silica channel wall, and lower exists in the crystalline state. When AgNO 3 content exceeds this value, AgCl/Ag nanoparticles can be observed in high crystalline state. The absorption at 327 nm ascribed to the characteristic absorption of the AgCl semiconductor. Ag nanoparticles have been shown to exist in the nanocomposite at 375 nm. When AgNO 3 content is above 0.1 wt.% in synthetic gel, spectra exhibited stronger absorption at 450-700 nm that was attributed to the surface plasmonic resonance of silver nanoparticles. The obtained AgCl/Ag/MCM-41 sample exhibit enhanced photocatalytic activity for the degradation of methylene blue under visible-light irradiation.

New, rapid method to measure dissolved silver concentration in silver nanoparticle suspensions by aggregation combined with centrifugation

NASA Astrophysics Data System (ADS)

Dong, Feng; Valsami-Jones, Eugenia; Kreft, Jan-Ulrich

2016-09-01

It is unclear whether the antimicrobial activities of silver nanoparticles (AgNPs) are exclusively mediated by the release of silver ions (Ag+) or, instead, are due to combined nanoparticle and silver ion effects. Therefore, it is essential to quantify dissolved Ag in nanosilver suspensions for investigations of nanoparticle toxicity. We developed a method to measure dissolved Ag in Ag+/AgNPs mixtures by combining aggregation of AgNPs with centrifugation. We also describe the reproducible synthesis of stable, uncoated AgNPs. Uncoated AgNPs were quickly aggregated by 2 mM Ca2+, forming large clusters that could be sedimented in a low-speed centrifuge. At 20,100g, the sedimentation time of AgNPs was markedly reduced to 30 min due to Ca2+-mediated aggregation, confirmed by the measurements of Ag content in supernatants with graphite furnace atomic absorption spectrometry. No AgNPs were detected in the supernatant by UV-Vis absorption spectra after centrifuging the aggregates. Our approach provides a convenient and inexpensive way to separate dissolved Ag from AgNPs, avoiding long ultracentrifugation times or Ag+ adsorption to ultrafiltration membranes.

The True Ultracool Binary Fraction Using Spectral Binaries

NASA Astrophysics Data System (ADS)

Bardalez Gagliuffi, Daniella; Burgasser, Adam J.; Schmidt, Sarah J.; Gagné, Jonathan; Faherty, Jacqueline K.; Cruz, Kelle; Gelino, Chris

2018-01-01

Brown dwarfs bridge the gap between stars and giant planets. While the essential mechanisms governing their formation are not well constrained, binary statistics are a direct outcome of the formation process, and thus provide a means to test formation theories. Observational constraints on the brown dwarf binary fraction place it at 10 ‑ 20%, dominated by imaging studies (85% of systems) with the most common separation at 4 AU. This coincides with the resolution limit of state-of-the-art imaging techniques, suggesting that the binary fraction is underestimated. We have developed a separation-independent method to identify and characterize tightly-separated (< 5 AU) binary systems of brown dwarfs as spectral binaries by identifying traces of methane in the spectra of late-M and early-L dwarfs. Imaging follow-up of 17 spectral binaries yielded 3 (18%) resolved systems, corroborating the observed binary fraction, but 5 (29%) known binaries were missed, reinforcing the hypothesis that the short-separation systems are undercounted. In order to find the true binary fraction of brown dwarfs, we have compiled a volume-limited, spectroscopic sample of M7-L5 dwarfs and searched for T dwarf companions. In the 25 pc volume, 4 candidates were found, three of which are already confirmed, leading to a spectral binary fraction of 0.95 ± 0.50%, albeit for a specific combination of spectral types. To extract the true binary fraction and determine the biases of the spectral binary method, we have produced a binary population simulation based on different assumptions of the mass function, age distribution, evolutionary models and mass ratio distribution. Applying the correction fraction resulting from this method to the observed spectral binary fraction yields a true binary fraction of 27 ± 4%, which is roughly within 1σ of the binary fraction obtained from high resolution imaging studies, radial velocity and astrometric monitoring. This method can be extended to identify giant planet companions to young brown dwarfs.

Synthesis of silver/silver chloride/graphene oxide composite and its surface-enhanced Raman scattering activity and self-cleaning property

NASA Astrophysics Data System (ADS)

Zhao, Nan; Fei, Xiao; Cheng, Xiaonong; Yang, Juan

2017-09-01

Recently, silver nanoparticles decorated with graphene and graphene oxide (GO) sheets can be employed as surface-enhanced Raman scattering (SERS) substrates. However, their SERS activity on macromolecular compound detection is all one-time process. In order to solve this issue and decrease the cost of routine SERS detection, silver/silver chloride (Ag/AgCl) with photocatalytic activity under visible light was introduced. In this study, a novel, simple and clean approach is carried out for synthesis of the Ag/AgCl/GO composite. The Ag/AgCl colloidal solution is obtained by hydrothermal method and then mixed with GO solution to obtain the Ag/AgCl/GO composite using a facile electrostatic self-assembly method. Results showed that the Ag/AgCl/GO composite has the optimized SERS activity to Rhodamine 6G molecules with the maximum enhancement factor value of 3.8×107. Furthermore, the Ag/AgCl particles with high efficient and stable photocatalytic activity under visible light lead to an outstanding self-cleaning property of the Ag/AgCl/GO composite.

Highly reliable Ag/Zn/Ag ohmic reflector for high-power GaN-based vertical light-emitting diode.

PubMed

Yum, Woong-Sun; Jeon, Joon-Woo; Sung, Jun-Suk; Seong, Tae-Yeon

2012-08-13

We report the improved performance of InGaN/GaN-based light-emitting diodes (LEDs) through Ag reflectors combined with a Zn middle layer. It is shown that the Zn middle layer (5 nm thick) suppresses the agglomeration of Ag reflectors by forming ZnO and dissolving into Ag. The Ag/Zn/Ag contacts show a specific contact resistance of 6.2 × 10(-5) Ωcm(2) and reflectance of ~83% at a wavelength of 440 nm when annealed at 500 °C, which are much better than those of Ag only contacts. Blue LEDs fabricated with the 500 °C-annealed Ag/Zn/Ag reflectors show a forward voltage of 2.98 V at an injection current of 20 mA, which is lower than that (3.02 V) of LEDs with the annealed Ag only contacts. LEDs with the 500 °C-annealed Ag/Zn/Ag contacts exhibit 34% higher output power (at 20 mA) than LEDs with the annealed Ag only contacts.

Are silver nanoparticles always toxic in the presence of environmental anions?

PubMed

Guo, Zhi; Chen, Guiqiu; Zeng, Guangming; Yan, Ming; Huang, Zhenzhen; Jiang, Luhua; Peng, Chuan; Wang, Jiajia; Xiao, Zhihua

2017-03-01

Increasing amounts of silver nanoparticles (AgNPs) are expected to enter the ecosystems where their toxicity in the environment is proposed. In this study, we exploited the effect of environmental anions on AgNP toxicity. AgNP were mixed with various environmental anions, and then exposed to Escherichia coli to determine the effect on bacteria growth inhibition. The results demonstrated that AgNP are not always toxic in the presence of sulfide, but can stimulate microbial growth at certain concentrations. Environmental chloride and phosphate anions cannot induce the stimulation because of their weak capacity to control the release of Ag + from AgNP. Ag + that released from AgNP is proven to be responsible for AgNP toxicity. Moreover, we found that AgNP toxicity is dependent on sulfuration rate. At the same sulfuration rate, AgNP shows an identical pattern of toxicity. This study indicates that only sulfide of the tested environmental anions can induce AgNP stimulation to microbial growth in a sulfuration rate dependent pattern and the toxicity originate from Ag + that released from AgNP. Copyright © 2016 Elsevier Ltd. All rights reserved.

Understanding the effect of annealing temperature on crystalline structure, morphology, and photocatalytic activity of silver-loaded TiO2 nanotubes

NASA Astrophysics Data System (ADS)

Viet, Pham Van; Phuong Trang, Duong Dao; Phat, Bui Dai; Hieu, Le Van; Thi, Cao Minh

2018-05-01

In this study, we classified the effect of the annealing temperature on silver-loaded TiO2 nanotubes (Ag/TNTs). X-ray diffraction results demonstrate that TNTs have a tendency of phase transformation owing to silver nanoparticles (Ag NPs). The Brunauer-Emmett-Teller method indicates that Ag/TNTs is a mesopore material and the surface area of Ag/TNTs decreases when the annealing temperature increases. This research concluded that the TNT structure begins to break at high annealing temperatures (>400 °C) and is completely broken at 500 °C. The average diameter of the Ag NPs in Ag/TNTs increases linearly with the annealing temperature. In addition, this study clearly explained the oxidation state transformation of Ag in Ag/TNTs under the impact of the annealing temperature, therein, the Ag0 state is transferred completely to Ag+ at 400 °C, and some Ag+ is oxidized to form Ag2+. The Ag/TNTs and Ag/TNTs annealed at 300 °C provided the good methylene blue photodegradation ability for 150 min under sunlight condition.

Application of a Newly Developed High-Sensitivity HBsAg Chemiluminescent Enzyme Immunoassay for Hepatitis B Patients with HBsAg Seroclearance

PubMed Central

Shinkai, Noboru; Matsuura, Kentaro; Sugauchi, Fuminaka; Watanabe, Tsunamasa; Murakami, Shuko; Iio, Etsuko; Ogawa, Shintaro; Nojiri, Shunsuke; Joh, Takashi

2013-01-01

We modified and automated a highly sensitive chemiluminescent enzyme immunoassay (CLEIA) for surface antigen (HBsAg) detection using a combination of monoclonal antibodies, each for a specific epitope of HBsAg, and by improving an earlier conjugation technique. Of 471 hepatitis B virus (HBV) carriers seen in our hospital between 2009 and 2012, 26 were HBsAg seronegative as determined by the Abbott Architect assay. The Lumipulse HBsAg-HQ assay was used to recheck those 26 patients who demonstrated seroclearance by the Abbott Architect assay. The performance of the Lumipulse HBsAg-HQ assay was compared with that of a quantitative HBsAg detection system (Abbott Architect) and the Roche Cobas TaqMan HBV DNA assay (CTM) (lower limit of detection, 2.1 log copies/ml) using blood serum samples from patients who were determined to be HBsAg seronegative by the Abbott Architect assay. Ten patients had spontaneous HBsAg loss. Of 8 patients treated with nucleotide analogues (NAs), two were HBsAg seronegative after stopping lamivudine therapy and 6 were HBsAg seronegative during entecavir therapy. Eight acute hepatitis B (AH) patients became HBsAg seronegative. Of the 26 patients, 16 were HBsAg positive by the Lumipulse HBsAg-HQ assay but negative by the Abbott Architect assay. The differences between the two assays in terms of detectable HBsAg persisted over the long term in the spontaneous loss group (median, 10 months), the NA-treated group (2.5 months), and the AH group (0.5 months). In 9 patients, the Lumipulse HBsAg-HQ assay detected HBsAg when HBV DNA was negative by the CTM assay. HBsAg was also detected by the Lumipulse HBsAg-HQ assay in 4 patients with an anti-HBs concentration of >10 mIU/ml, 3 of whom had no HBsAg escape mutations. The automatic, highly sensitive HBsAg CLEIA Lumipulse HBsAg-HQ is a convenient and precise assay for HBV monitoring. PMID:23946517

Application of a newly developed high-sensitivity HBsAg chemiluminescent enzyme immunoassay for hepatitis B patients with HBsAg seroclearance.

PubMed

Shinkai, Noboru; Matsuura, Kentaro; Sugauchi, Fuminaka; Watanabe, Tsunamasa; Murakami, Shuko; Iio, Etsuko; Ogawa, Shintaro; Nojiri, Shunsuke; Joh, Takashi; Tanaka, Yasuhito

2013-11-01

We modified and automated a highly sensitive chemiluminescent enzyme immunoassay (CLEIA) for surface antigen (HBsAg) detection using a combination of monoclonal antibodies, each for a specific epitope of HBsAg, and by improving an earlier conjugation technique. Of 471 hepatitis B virus (HBV) carriers seen in our hospital between 2009 and 2012, 26 were HBsAg seronegative as determined by the Abbott Architect assay. The Lumipulse HBsAg-HQ assay was used to recheck those 26 patients who demonstrated seroclearance by the Abbott Architect assay. The performance of the Lumipulse HBsAg-HQ assay was compared with that of a quantitative HBsAg detection system (Abbott Architect) and the Roche Cobas TaqMan HBV DNA assay (CTM) (lower limit of detection, 2.1 log copies/ml) using blood serum samples from patients who were determined to be HBsAg seronegative by the Abbott Architect assay. Ten patients had spontaneous HBsAg loss. Of 8 patients treated with nucleotide analogues (NAs), two were HBsAg seronegative after stopping lamivudine therapy and 6 were HBsAg seronegative during entecavir therapy. Eight acute hepatitis B (AH) patients became HBsAg seronegative. Of the 26 patients, 16 were HBsAg positive by the Lumipulse HBsAg-HQ assay but negative by the Abbott Architect assay. The differences between the two assays in terms of detectable HBsAg persisted over the long term in the spontaneous loss group (median, 10 months), the NA-treated group (2.5 months), and the AH group (0.5 months). In 9 patients, the Lumipulse HBsAg-HQ assay detected HBsAg when HBV DNA was negative by the CTM assay. HBsAg was also detected by the Lumipulse HBsAg-HQ assay in 4 patients with an anti-HBs concentration of >10 mIU/ml, 3 of whom had no HBsAg escape mutations. The automatic, highly sensitive HBsAg CLEIA Lumipulse HBsAg-HQ is a convenient and precise assay for HBV monitoring.

Low prevalence of hepatitis B and C among tuberculosis patients in Duhok Province, Kurdistan: Are HBsAg and anti-HCV prerequisite screening parameters in tuberculosis control program?

PubMed

Merza, Muayad A; Haji, Safer M; Alsharafani, Abid Mohialdeen Hasan; Muhammed, Shivan U

2016-09-01

Viral hepatitis, particularly hepatitis B virus (HBV) and hepatitis C virus (HCV), infections and tuberculosis (TB) are a global public health concern. Co-infection with HBV or HCV among TB patients may potentiate the risk of hepatotoxicity induced by anti-TB drugs. Hence, the aim of this study was to identify the prevalence of HBV and HCV among TB patients included in the Duhok National Tuberculosis Program (NTP). The Duhok NTP Center is a specialized institution in Duhok City, Iraq, concerned with management and follow-up of TB patients. A cross-sectional study was conducted at the center between June 2015 and May 2016. All documented TB patients were analyzed on the basis of socio-demographic and other characteristics. Thereafter, all patients underwent screening for hepatitis B surface antigen (HBsAg), anti-HCV, and anti-HIV using enzyme-linked immunosorbent assay (ELISA). The results obtained were analyzed by entering the data in binary format into a Microsoft Excel spreadsheet. A p value of <.05 was considered to be statistically significant. Two-hundred fourteen documented TB patients were recruited in this study, with 127 (59.3%) males and 87 (40.7%) females. The mean age of the patients was 40.34years (±20.29). Of the total number of patients, four cases (1.8%) were HBsAg-positive and one case (0.9%) was positive for anti-HCV. The variables significantly associated with HBV were history of surgical dental procedure [odds ratio (OR), 0.04; 95% confidence interval (CI), -0.01 to 0.04; p=.03], and nationality (OR, 13.67; 95% CI, 0.46-210.85; p=.007). The prevalence of HBV and HCV co-infection among TB patients in this study was low. This may be explained by the low rate of blood transfusion among the patients, the very low prevalence of HIV infections in Kurdistan, the negative history of injection drug use, and adherence to universal infection-control measures, including vaccination for HBV. Both history of dental intervention and belonging to a Syrian population were independent risk factors for HBV/TB co-infection. Copyright © 2016 Asian-African Society for Mycobacteriology. Published by Elsevier Ltd. All rights reserved.

Oligocene shoshonitic rocks of the Rogozna Mts. (Central Balkan Peninsula): Evidence of petrogenetic links to the formation of Pb-Zn-Ag ore deposits

NASA Astrophysics Data System (ADS)

Borojević Šoštarić, S.; Cvetković, V.; Neubauer, F.; Palinkaš, L. A.; Bernroider, M.; Genser, J.

2012-09-01

This study focuses on age and evolution of the Oligocene quartz latite of the Rogozna Mts. (Central Balkan Peninsula), in order to better understand the link between magmatism and formation of Pb-Zn ± Ag mineralization. New 40Ar/39Ar biotite and amphibole plateau ages suggest that the Rogozna Mts. quartz latite originated through a continuous volcanic episode from 27.3 ± 0.1 to 29.5 ± 0.1 Ma which was immediately followed by a hydrothermal phase. The quartz latites are hypocrystalline porphyritic with phenocrysts and microphenocrysts (~ 60 vol.%) of plagioclase (An37-49), biotite Mg# [100 × Mg / (Mg + Fetot)] < 50, calcic amphibole, quartz, sanidine clinopyroxene and phlogopite (Mg# = 79 to 84). The rocks display numerous disequilibrium textures, such as: sieved plagioclase phenocrysts, dissolution effects on quartz, phlogopitized biotite and amphibole crystals, and phlogopite microphenocrysts showing effects of incomplete growth (or dissolution?) and biotitization. The Rogozna Mts. quartz latites are shoshonitic in character with Na2O/K2O < 1, high LILE/HFSE ratios, strong depletions at Nb and Ti and K, Pb and U peaks on primitive mantle-normalized diagrams. They are similar to other potassic/ultrapotassic rocks in this region, in particular to those of Veliki Majdan and Rudnik (West Serbia), which are also related to Pb-Zn deposits. The evolution of the Rogozna Mts. quartz latite is modeled using a trace element binary mixing model adopting a lamproite magma and a dacite-like calc-alkaline melt as end-members. The model implies that a fractionating magma chamber (~ 4.5-9.5 km) undergoes cooling in the range of > 850 °C-~720 °C and injection of lamproite-like melts. The injection causes an increase of temperature and a decrease of viscosity of the resulting hybrid magma, facilitating its upwelling and triggering pyroclastic eruptions. The addition of new volatiles by lamproitic melts most probably established the conditions for a hydrothermal phase above the magma chamber that was previously degassed explosively. This implies that magma mixing processes can be of great importance for the formation of Pb-Zn deposits. Similar processes are likely to have occurred in other areas with economically significant Pb-Zn-Ag ± other metal mineralization in the region of the Central Balkan Peninsula (Veliki Majdan, Rudnik, Golija, Kopaonik, Avala, etc.).

Synthesis of High Valence Silver-Loaded Mesoporous Silica with Strong Antibacterial Properties

PubMed Central

Chen, Chun-Chi; Wu, Hsin-Hsien; Huang, Hsin-Yi; Liu, Chen-Wei; Chen, Yi-Ning

2016-01-01

A simple chemical method was developed for preparing high valence silver (Ag)-loaded mesoporous silica (Ag-ethylenediaminetetraacetic acid (EDTA)-SBA-15), which showed strong antibacterial activity. Ag-EDTA-SBA-15 exhibited stronger and more effective antibacterial activity than commercial Ag nanoparticles did, and it offered high stability of high valence silver in the porous matrix and long-lasting antibacterial activity. The synthesized materials were characterized using Fourier transform infrared spectroscopy, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) analysis, and transmission electron microscopy (TEM). Ag existed in both surface complexation and Ag particles. EDTA anchored within a porous structure chelated Ag ions in higher oxidation states and prevented their agglomeration and oxidation reduction. The XRD results showed that most Ag in the Ag-EDTA-SBA-15 existed in higher oxidation states such as Ag(II) and Ag(III). However, the XPS and TEM results showed that Ag easily reduced in lower oxidation states and agglomerated as Ag particles on the exterior layer of the SBA-15. PMID:26742050

Rapid water disinfection over a Ag/AgBr/covalent triazine-based framework composite under visible light.

PubMed

Li, Liuyi; Li, Xiaofen; Cheng, Zhi; Bi, Jinhong; Liang, Shijing; Zhang, Zizhong; Yu, Yan; Wu, Ling

2018-05-22

Development of visible-light-induced and rapid water disinfection is of significant importance. Covalent triazine-based frameworks (CTFs) with pre-designable structures and favorable semiconductive behaviors hold great promise for photocatalytic water disinfection. Here, we report an Ag/AgBr/CTF composite with a layered structure, which serves as an efficient photocatalyst for rapid water disinfection. Water disinfection with >99.99% inactivation of Escherichia coli within 12 min was achieved by using a small amount of Ag/AgBr/CTF under visible light irradiation. The inactivation efficiency of Ag/AgBr/CTF was ∼10 times better than that of bare Ag/AgBr. Rapid water disinfection by the Ag/AgBr/CTF composite mainly results from the greatly improved generation of reactive oxygen species through the synergistic effects among the three components and the affinity of CTF to the cell wall of bacteria.

Ferromagnetic signal in nanosized Ag particles.

PubMed

Jo, Younghun; Jung, Myung-Hwa; Kyum, Myung-Chul; Lee, Sung-Ik

2007-11-01

A new technique using an inductively coupled plasma reactor equipped with a liquid-nitrogen cooling system was developed to prepare Ag nanoparticles. The magnetic signal from these Ag particles with diameters of 4 nm showed, surprisingly, a signal with combined ferromagnetic and diamagnetic components, in contrast to the signal with only one diamagnetic component from bulk Ag. The same technique was used to prepare the Ag/Cu nanoparticles, which are Ag nanoparticles coated with a Cu layer. Compared to the Ag nanoparticles, these showed a greatly enhanced superparamagnetic signal in addition to the same value of the ferromagnetism. The comparison between the Ag and the Ag/Cu nanoparticles indicated that the ferromagnetic components are a common feature of Ag nanoparticles while the greatly enhanced paramagnetic component of Ag/Cu, which dominates over the background diamagnetic component from the Ag core, is from the outer Cu shell.

Research on the Orbital Period of Massive Binaries

NASA Astrophysics Data System (ADS)

Zhao, E.; Qain, S.

2011-12-01

Massive binary is the kind of binary, whose spectral type is earlier than B5. Research on massive binary plays an important role in the mass and angular momentum transfer or loss between the components, and the evolution of binary. Some massive binaries are observed and analyzed, including O-type binary LY Aur, B-type contact binary RZ Pyx and B-type semi-detached binary AI Cru. It is found that all of their periods have a long-term increasing, which indicates that the system is undergoing a Case A slow mass transfer stage on the nuclear time-scale of the secondary. Moreover, analysis show a cyclic change of orbital period, which can be explained by the light-travel effect time of the third body.

The effect of chronic silver nanoparticles on aquatic system in microcosms.

PubMed

Jiang, Hong Sheng; Yin, Liyan; Ren, Na Na; Xian, Ling; Zhao, Suting; Li, Wei; Gontero, Brigitte

2017-04-01

Silver nanoparticles (AgNPs) inevitably discharge into aquatic environments due to their abundant use in antibacterial products. It was reported that in laboratory conditions, AgNPs display dose-dependent toxicity to aquatic organisms, such as bacteria, algae, macrophytes, snails and fishes. However, AgNPs could behave differently in natural complex environments. In the present study, a series of microcosms were established to investigate the distribution and toxicity of AgNPs at approximately 500 μg L -1 in aquatic systems. As a comparison, the distribution and toxicity of the same concentration of AgNO 3 were also determined. The results showed that the surface layer of sediment was the main sink of Ag element for both AgNPs and AgNO 3 . Both aquatic plant (Hydrilla verticillata) and animals (Gambusia affinis and Radix spp) significantly accumulated Ag. With short-term treatment, phytoplankton biomass was affected by AgNO 3 but not by AgNPs. Chlorophyll content of H. verticillata increased with both AgNPs and AgNO 3 short-term exposure. However, the biomass of phytoplankton, aquatic plant and animals was not significantly different between control and samples treated with AgNPs or AgNO 3 for 90 d. The communities, diversity and richness of microbes were not significantly affected by AgNPs and AgNO 3 ; in contrast, the nitrification rate and its related microbe (Nitrospira) abundance significantly decreased. AgNPs and AgNO 3 may affect the nitrogen cycle and affect the environment and, since they might be also transferred to food web, they represent a risk for health. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ag@AgHPW as a plasmonic catalyst for visible-light photocatalytic degradation of environmentally harmful organic pollutants

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

Zhou, Wenhui; Cao, Minhua, E-mail: caomh@bit.edu.cn; Li, Na

2013-06-01

Graphical abstract: Ag@Ag{sub x}H{sub 3−x}PW12O40 (Ag@AgHPW) nanoparticles (NPs), a new visible-light driven plasmonic photocatalyst, are prepared by a green photoreduction strategy without the addition of any surfactant, which show a high activity and stability for the degradation of methyl blue (MB) under visible light irradiation. - Highlights: • A new visible-light driven photocatalyst Ag@Ag{sub x}H{sub 3−x}PW{sub 12}O{sub 40} was designed. • The photocatalyst shows a high activity for the degradation of methyl blue. • The high activity can be ascribed to the synergy of photoexcited AgHPW and Ag. - Abstract: Ag@Ag{sub x}H{sub 3−x}PW{sub 12}O{sub 40} (Ag@AgHPW) nanoparticles (NPs), a newmore » visible-light driven plasmonic photocatalyst, are prepared by a green photoreduction strategy without the addition of any surfactant. They show strong absorption in the visible region because of the localized surface plasmon resonance (LSPR) of Ag NPs. This plasmonic photocatalyst shows a high activity and stability for the degradation of methyl blue (MB) under visible light irradiation, which could be attributed to the highly synergy of photoexcited Ag{sub x}H{sub 3−x}PW{sub 12}O{sub 40} (AgHPW) and plasmon-excited Ag NPs and the confinement effects at interfaces between polyoxometalates (POMs) and silver. POM anions have redox ability and high photocatalytic activity, whereas Ag NPs could effectively accelerate the separation of electrons and holes, both of which contribute to their high activity.« less

Uptake pathway for Ag bioaccumulation in three benthic invertebrates exposed to contaminated sediments

USGS Publications Warehouse

Yoo, H.; Lee, J.-S.; Lee, B.-G.; Lee, I.T.; Schlekat, C.E.; Koh, C.-H.; Luoma, S.N.

2004-01-01

We exposed 3 benthic invertebrates, the clam Macoma balthica, the polychaete Neanthes arenaceodentata and the amphipod Leptocheirus plumulosus, to Ag-contaminated sediments to evaluate the relative importance of various uptake routes (sediments, porewater or overlying water, and supplementary food) for Ag bioaccumulation. Silver bioaccumulation was evaluated at 4 levels of sediment Ag (0.1, 0,3, 1,2 and 3.3 ??mol Ag g-1) and 2 levels of acid-volatile sulfide (AVS), <0.5 or ???40 ??mol g-1, and compared among food treatments with or without Ag contamination, or with different food rations. L. plumulosus were incubated for 35 d in the Ag-contaminated sediments after 3 mo of Ag-sediment equilibration, and M. balthica and N. arenaceodentata for 19 d after 5 mo equilibration. Ag bioaccumulation in the 3 organisms was significantly correlated with 1N HCl-extractable Ag concentrations (Ag-SEM: simultaneously extracted Ag with AVS) in sediments. The Ag concentrations in porewater and overlying water were greatest in the sediments with least AVS, consistent with previous studies. Nevertheless, the amphipod and clam exposed to oxic sediments (<0.5 ??mol AVS g-1) accumulated amounts of Ag similar to those accumulated by organisms exposed to anoxic sediments (???40 ??mol AVS g-1), when Ag-SEM levels were comparable. The dissolved Ag source was important for bioaccumulation in the polychaete N. arenaceodentata. Amphipods fed Ag-contaminated food contained ???1.8-fold more tissue Ag concentrations than those fed uncontaminated food. As suggested in kinetic (DYMBAM) modeling studies, ingestion of contaminated sediments and food were the principle routes of Ag bioaccumulation by the benthic invertebrates during chronic exposure, but the relative importance of each uptake route differed among species.

Demonstrating approaches to chemically modify the surface of Ag nanoparticles in order to influence their cytotoxicity and biodistribution after single dose acute intravenous administration.

PubMed

Pang, Chengfang; Brunelli, Andrea; Zhu, Conghui; Hristozov, Danail; Liu, Ying; Semenzin, Elena; Wang, Wenwen; Tao, Wuqun; Liang, Jingnan; Marcomini, Antonio; Chen, Chunying; Zhao, Bin

2016-01-01

With the advance in material science and the need to diversify market applications, silver nanoparticles (AgNPs) are modified by different surface coatings. However, how these surface modifications influence the effects of AgNPs on human health is still largely unknown. We have evaluated the uptake, toxicity and pharmacokinetics of AgNPs coated with citrate, polyethylene glycol, polyvinyl pyrolidone and branched polyethyleneimine (Citrate AgNPs, PEG AgNPs, PVP AgNPs and BPEI AgNPs, respectively). Our results demonstrated that the toxicity of AgNPs depends on the intracellular localization that was highly dependent on the surface charge. BPEI AgNPs (ζ potential = +46.5 mV) induced the highest cytotoxicity and DNA fragmentation in Hepa1c1c7. In addition, it showed the highest damage to the nucleus of liver cells in the exposed mice, which is associated with a high accumulation in liver tissues. The PEG AgNPs (ζ potential = -16.2 mV) showed the cytotoxicity, a long blood circulation, as well as bioaccumulation in spleen (34.33 µg/g), which suggest better biocompatibility compared to the other chemically modified AgNPs. Moreover, the adsorption ability with bovine serum albumin revealed that the PEG surface of AgNPs has an optimal biological inertia and can effectively resist opsonization or non-specific binding to protein in mice. The overall results indicated that the biodistribution of AgNPs was significantly dependent on surface chemistry: BPEI AgNPs > Citrate AgNPs = PVP AgNPs > PEG AgNPs. This toxicological data could be useful in supporting the development of safe AgNPs for consumer products and drug delivery applications.

Involvement of lysosomal dysfunction in silver nanoparticle-induced cellular damage in A549 human lung alveolar epithelial cells.

PubMed

Miyayama, Takamitsu; Matsuoka, Masato

2016-01-01

While silver nanoparticles (AgNPs) are widely used in consumer and medical products, the mechanism by which AgNPs cause pulmonary cytotoxicity is not clear. AgNP agglomerates are found in endo-lysosomal structures within the cytoplasm of treated cells. In this study, the functional role of lysosomes in AgNP-induced cellular damage was examined in A549 human lung alveolar epithelial cells. We evaluated the intracellular distribution of AgNPs, lysosomal pH, cellular viability, Ag dissolution, and metallothionein (MT) mRNA levels in AgNP-exposed A549 cells that were treated with bafilomycin A1, the lysosomal acidification inhibitor. Exposure of A549 cells to citrate-coated AgNPs (20 nm diameter) for 24 h induced cellular damage and cell death at 100 and 200 μg Ag/ml, respectively. Confocal laser microscopic examination of LysoTracker-stained cells showed that AgNPs colocalized with lysosomes and their agglomeration increased in a dose-dependent manner (50-200 μg Ag/ml). In addition, the fluorescence signals of LysoTracker were reduced following exposure to AgNPs, suggesting the elevation of lysosomal pH. Treatment of A549 cells with 200 nM bafilomycin A1 and AgNPs (50 μg Ag/ml) further reduced the fluorescence signals of LysoTracker. AgNP-induced cell death was also increased by bafilomycin A1 treatment. Finally, treatment with bafilomycin A1 suppressed the dissolution of Ag and decreased the mRNA expression levels of MT-I and MT-II following exposure to AgNPs. The perturbation of lysosomal pH by AgNP exposure may play a role in AgNP agglomeration and subsequent cellular damage in A549 cells.

Tidal disruption of inclined or eccentric binaries by massive black holes

NASA Astrophysics Data System (ADS)

Brown, Harriet; Kobayashi, Shiho; Rossi, Elena M.; Sari, Re'em

2018-07-01

Binary stars that are on close orbits around massive black holes (MBHs) such as Sgr A* in the centre of the Milky Way are liable to undergo tidal disruption and eject a hypervelocity star. We study the interaction between such an MBH and circular binaries for general binary orientations and penetration depths (i.e. binaries penetrate into the tidal radius around the BH). We show that for very deep penetrators, almost all binaries are disrupted when the binary rotation axis is roughly oriented towards the BH or it is in the opposite direction. The surviving chance becomes significant when the angle between the binary rotation axis and the BH direction is between 0.15π and 0.85π. The surviving chance is as high as ˜20 per cent when the binary rotation axis is perpendicular to the BH direction. However, for shallow penetrators, the highest disruption chance is found in such a perpendicular case, especially in the prograde case. This is because the dynamics of shallow penetrators is more sensitive to the relative orientation of the binary and orbital angular momenta. We provide numerical fits to the disruption probability and energy gain at the BH encounter as a function of the penetration depth. The latter can be simply rescaled in terms of binary masses, their initial separation, and the binary-to-BH mass ratio to evaluate the ejection velocity of a binary members in various systems. We also investigate the disruption of coplanar, eccentric binaries by an MBH. It is shown that for highly eccentric binaries retrograde orbits have a significantly increased disruption probability and ejection velocities compared to the circular binaries.

Tidal Disruption of Inclined or Eccentric Binaries by Massive Black Holes

NASA Astrophysics Data System (ADS)

Brown, Harriet; Kobayashi, Shiho; Rossi, Elena M.; Sari, Re'em

2018-04-01

Binary stars that are on close orbits around massive black holes (MBH) such as Sgr A* in the centre of the Milky Way are liable to undergo tidal disruption and eject a hypervelocity star. We study the interaction between such a MBH and circular binaries for general binary orientations and penetration depths (i.e. binaries penetrate into the tidal radius around the BH). We show that for very deep penetrators, almost all binaries are disrupted when the binary rotation axis is roughly oriented toward the BH or it is in the opposite direction. The surviving chance becomes significant when the angle between the binary rotation axis and the BH direction is between 0.15π and 0.85π. The surviving chance is as high as ˜20% when the binary rotation axis is perpendicular to the BH direction. However, for shallow penetrators, the highest disruption chance is found in such a perpendicular case, especially in the prograde case. This is because the dynamics of shallow penetrators is more sensitive to the relative orientation of the binary and orbital angular momenta. We provide numerical fits to the disruption probability and energy gain at the the BH encounter as a function of the penetration depth. The latter can be simply rescaled in terms of binary masses, their initial separation and the binary-to-BH mass ratio to evaluate the ejection velocity of a binary members in various systems. We also investigate the disruption of coplanar, eccentric binaries by a MBH. It is shown that for highly eccentric binaries retrograde orbits have a significantly increased disruption probability and ejection velocities compared to the circular binaries.

The effect of soil properties on the toxicity and bioaccumulation of Ag nanoparticles and Ag ions in Enchytraeus crypticus.

PubMed

Topuz, Emel; van Gestel, Cornelis A M

2017-10-01

Standard natural Lufa soils (2.2, 2.3 and 5M) with different organic carbon contents (0.67-1.61%) and pH CaCl2 (5.5-7.3) were spiked with ionic Ag (AgNO 3 ) and polyvinyl pyrrolidone (AgNP-PVP) and citrate (AgNP-Cit) coated Ag nanoparticles (NPs). Enchytraeus crypticus were exposed for 21 days to assess effects on survival and reproduction. Soil, pore water and animals were analyzed for Ag. AgNP-Cit had a strong increasing effect on soil pH, leading to high enchytraeid mortality at concentrations higher than 60-100mg Ag/kg dry soil which made it impossible to determine the influence of soil properties on its toxicity. LC50s were lower for AgNO 3 than for AgNP-PVP (92-112 and 335-425mg Ag/kg dry soil, respectively) and were not affected by soil properties. AgNO 3 and AgNP-PVP had comparable reproductive toxicity with EC50s of 26.9-75.2 and 28.2-92.3mg Ag/kg dry soil, respectively; toxicity linearly increased with decreasing organic carbon content of the soils but did not show a clear effect of soil pH. Ag uptake in the enchytraeids was higher at higher organic carbon content, but could not explain differences in toxicity between soils. This study indicates that the bioavailability of both ionic and nanoparticulate Ag is mainly affected by soil organic carbon, with little effect of soil pH. Copyright © 2017. Published by Elsevier Inc.

Preparation of Ag@AgCl-doped TiO2/sepiolite and its photocatalytic mechanism under visible light.

PubMed

Liu, Shaomin; Zhu, Dinglong; Zhu, Jinglin; Yang, Qing; Wu, Huijun

2017-10-01

A cube-like Ag@AgCl-doped TiO 2 /sepiolite (denoted Ag@AgCl-TiO 2 /sepiolite) was successfully synthesized via a novel method. X-ray diffraction, scanning electron microscopy, energy dispersion X-ray fluorescence, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and diffuse reflectance ultraviolet-visible spectroscopy were performed to determine the structure and physicochemical properties of Ag@AgCl-TiO 2 /sepiolite. SEM micrographs revealed that Ag@AgCl nanoparticles and TiO 2 film are well deposited on the surface of tube-like sepiolite. As a result, Ag@AgCl-TiO 2 /sepiolite exhibits a red shift relative to TiO 2 /sepiolite. Photocatalytic experiments demonstrated that the dosage of catalysts plays an important role during photocatalysis. The photoelectrochemical activities of Ag@AgCl-TiO 2 /sepiolite and TiO 2 /sepiolite were also investigated. Photocurrent responses confirmed that the ability of Ag@AgCl-TiO 2 /sepiolite to separate photo-generated electron-hole pairs is stronger than that of TiO 2 /sepiolite. Methylene Blue degradation is also improved under alkaline conditions and visible light irradiation because more OH is produced by visible light excitation. This excellent catalytic ability is mainly attributed to the formed Ag nanoparticles and the Schottky barrier at the Ag/TiO 2 interface. Active species analysis indicated that O 2 - and h + are implicated as active species in photocatalysis. Therefore, catalysts are excited to produce abundant electron-hole pairs after they absorb photons in photocatalysis. Copyright © 2017. Published by Elsevier B.V.

New Results on Contact Binary Stars

NASA Astrophysics Data System (ADS)

He, J.; Qian, S.; Zhu, L.; Liu, L.; Liao, W.

2014-08-01

Contact binary star is a kind of close binary with the strongest interaction binary system. Their formations and evolutions are unsolved problems in astrophysics. Since 2000, our groups have observed and studied more than half a hundred of contact binaries. In this report, I will summarize our new results of some contact binary stars (e.g. UZ CMi, GSC 03526-01995, FU Dra, GSC 0763-0572, V524 Mon, MR Com, etc.). They are as follow: (1) We discovered that V524 Mon and MR Com are shallow-contact binaries with their period decreasing; (2) GSC 03526-01995 is middle-contact binary without a period increasing or decreasing continuously; (3) UZ CMi, GSC 0763-0572 and FU Dra are middle-contact binaries with the period increasing continuously; (4) UZ CMi, GSC 03526-01995, FU Dra and V524 Mon show period oscillation which may imply the presence of additional components in these contact binaries.

Characterisation of Antigen B Protein Species Present in the Hydatid Cyst Fluid of Echinococcus canadensis G7 Genotype

PubMed Central

Folle, Ana Maite; Kitano, Eduardo S.; Lima, Analía; Gil, Magdalena; Cucher, Marcela; Mourglia-Ettlin, Gustavo; Iwai, Leo K.; Rosenzvit, Mara; Batthyány, Carlos

2017-01-01

The larva of cestodes belonging to the Echinococcus granulosus sensu lato (s.l.) complex causes cystic echinococcosis (CE). It is a globally distributed zoonosis with significant economic and public health impact. The most immunogenic and specific Echinococcus-genus antigen for human CE diagnosis is antigen B (AgB), an abundant lipoprotein of the hydatid cyst fluid (HF). The AgB protein moiety (apolipoprotein) is encoded by five genes (AgB1-AgB5), which generate mature 8 kDa proteins (AgB8/1-AgB8/5). These genes seem to be differentially expressed among Echinococcus species. Since AgB immunogenicity lies on its protein moiety, differences in AgB expression within E. granulosus s.l. complex might have diagnostic and epidemiological relevance for discriminating the contribution of distinct species to human CE. Interestingly, AgB2 was proposed as a pseudogene in E. canadensis, which is the second most common cause of human CE, but proteomic studies for verifying it have not been performed yet. Herein, we analysed the protein and lipid composition of AgB obtained from fertile HF of swine origin (E. canadensis G7 genotype). AgB apolipoproteins were identified and quantified using mass spectrometry tools. Results showed that AgB8/1 was the major protein component, representing 71% of total AgB apolipoproteins, followed by AgB8/4 (15.5%), AgB8/3 (13.2%) and AgB8/5 (0.3%). AgB8/2 was not detected. As a methodological control, a parallel analysis detected all AgB apolipoproteins in bovine fertile HF (G1/3/5 genotypes). Overall, E. canadensis AgB comprised mostly AgB8/1 together with a heterogeneous mixture of lipids, and AgB8/2 was not detected despite using high sensitivity proteomic techniques. This endorses genomic data supporting that AgB2 behaves as a pseudogene in G7 genotype. Since recombinant AgB8/2 has been found to be diagnostically valuable for human CE, our findings indicate that its use as antigen in immunoassays could contribute to false negative results in areas where E. canadensis circulates. Furthermore, the presence of anti-AgB8/2 antibodies in serum may represent a useful parameter to rule out E. canadensis infection when human CE is diagnosed. PMID:28045899

Characterisation of Antigen B Protein Species Present in the Hydatid Cyst Fluid of Echinococcus canadensis G7 Genotype.

PubMed

Folle, Ana Maite; Kitano, Eduardo S; Lima, Analía; Gil, Magdalena; Cucher, Marcela; Mourglia-Ettlin, Gustavo; Iwai, Leo K; Rosenzvit, Mara; Batthyány, Carlos; Ferreira, Ana María

2017-01-01

The larva of cestodes belonging to the Echinococcus granulosus sensu lato (s.l.) complex causes cystic echinococcosis (CE). It is a globally distributed zoonosis with significant economic and public health impact. The most immunogenic and specific Echinococcus-genus antigen for human CE diagnosis is antigen B (AgB), an abundant lipoprotein of the hydatid cyst fluid (HF). The AgB protein moiety (apolipoprotein) is encoded by five genes (AgB1-AgB5), which generate mature 8 kDa proteins (AgB8/1-AgB8/5). These genes seem to be differentially expressed among Echinococcus species. Since AgB immunogenicity lies on its protein moiety, differences in AgB expression within E. granulosus s.l. complex might have diagnostic and epidemiological relevance for discriminating the contribution of distinct species to human CE. Interestingly, AgB2 was proposed as a pseudogene in E. canadensis, which is the second most common cause of human CE, but proteomic studies for verifying it have not been performed yet. Herein, we analysed the protein and lipid composition of AgB obtained from fertile HF of swine origin (E. canadensis G7 genotype). AgB apolipoproteins were identified and quantified using mass spectrometry tools. Results showed that AgB8/1 was the major protein component, representing 71% of total AgB apolipoproteins, followed by AgB8/4 (15.5%), AgB8/3 (13.2%) and AgB8/5 (0.3%). AgB8/2 was not detected. As a methodological control, a parallel analysis detected all AgB apolipoproteins in bovine fertile HF (G1/3/5 genotypes). Overall, E. canadensis AgB comprised mostly AgB8/1 together with a heterogeneous mixture of lipids, and AgB8/2 was not detected despite using high sensitivity proteomic techniques. This endorses genomic data supporting that AgB2 behaves as a pseudogene in G7 genotype. Since recombinant AgB8/2 has been found to be diagnostically valuable for human CE, our findings indicate that its use as antigen in immunoassays could contribute to false negative results in areas where E. canadensis circulates. Furthermore, the presence of anti-AgB8/2 antibodies in serum may represent a useful parameter to rule out E. canadensis infection when human CE is diagnosed.

Comparative Study of Antimicrobial Activity of AgBr and Ag Nanoparticles (NPs)

PubMed Central

Suchomel, Petr; Kvitek, Libor; Panacek, Ales; Prucek, Robert; Hrbac, Jan; Vecerova, Renata; Zboril, Radek

2015-01-01

The diverse mechanism of antimicrobial activity of Ag and AgBr nanoparticles against gram-positive and gram-negative bacteria and also against several strains of candida was explored in this study. The AgBr nanoparticles (NPs) were prepared by simple precipitation of silver nitrate by potassium bromide in the presence of stabilizing polymers. The used polymers (PEG, PVP, PVA, and HEC) influence significantly the size of the prepared AgBr NPs dependently on the mode of interaction of polymer with Ag+ ions. Small NPs (diameter of about 60–70 nm) were formed in the presence of the polymer with low interaction as are PEG and HEC, the polymers which interact with Ag+ strongly produce nearly two times bigger NPs (120–130 nm). The prepared AgBr NPs were transformed to Ag NPs by the reduction using NaBH4. The sizes of the produced Ag NPs followed the same trends – the smallest NPs were produced in the presence of PEG and HEC polymers. Prepared AgBr and Ag NPs dispersions were tested for their biological activity. The obtained results of antimicrobial activity of AgBr and Ag NPs are discussed in terms of possible mechanism of the action of these NPs against tested microbial strains. The AgBr NPs are more effective against gram-negative bacteria and tested yeast strains while Ag NPs show the best antibacterial action against gram-positive bacteria strains. PMID:25781988

Interactions of aqueous Ag+ with fulvic acids: mechanisms of silver nanoparticle formation and investigation of stability.

PubMed

Adegboyega, Nathaniel F; Sharma, Virender K; Siskova, Karolina; Zbořil, Radek; Sohn, Mary; Schultz, Brian J; Banerjee, Sarbajit

2013-01-15

This study investigated the possible natural formation of silver nanoparticles (AgNPs) in Ag(+)-fulvic acid (FA) solutions under various environmentally relevant conditions (temperature, pH, and UV light). Increase in temperature (24-90 °C) and pH (6.1-9.0) of Ag(+)-Suwannee River fulvic acid (SRFA) solutions accelerated the appearance of the characteristic surface plasmon resonance (SPR) of AgNPs. The rate of AgNP formation via reduction of Ag(+) in the presence of different FAs (SRFA, Pahokee Peat fulvic acid, PPFA, Nordic lake fulvic acid, NLFA) and Suwannee River humic acid (SRHA) followed the order NLFA > SRHA > PPFA > SRFA. This order was found to be related to the free radical content of the acids, which was consistent with the proposed mechanism. The same order of AgNP growth was seen upon UV light illumination of Ag(+)-FA and Ag(+)-HA mixtures in moderately hard reconstituted water (MHRW). Stability studies of AgNPs, formed from the interactions of Ag(+)-SRFA, over a period of several months showed that these AgNPs were highly stable with SPR peak reductions of only ~15%. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements revealed bimodal particle size distributions of aged AgNPs. The stable AgNPs formed through the reduction of Ag(+) by fulvic and humic acid fractions of natural organic matter in the environment may be transported over significant distances and might also influence the overall bioavailability and ecotoxicity of AgNPs.

Predicting kinetic nanocrystal shapes through multi-scale theory and simulation: Polyvinylpyrrolidone-mediated growth of Ag nanocrystals

NASA Astrophysics Data System (ADS)

Balankura, Tonnam; Qi, Xin; Zhou, Ya; Fichthorn, Kristen A.

2016-10-01

In the shape-controlled synthesis of colloidal Ag nanocrystals, structure-directing agents, particularly polyvinylpyrrolidone (PVP), are known to be a key additive in making nanostructures with well-defined shapes. Although many Ag nanocrystals have been successfully synthesized using PVP, the mechanism by which PVP actuates shape control remains elusive. Here, we present a multi-scale theoretical framework for kinetic Wulff shape predictions that accounts for the chemical environment, which we used to probe the kinetic influence of the adsorbed PVP film. Within this framework, we use umbrella-sampling molecular dynamics simulations to calculate the potential of mean force and diffusion coefficient profiles of Ag atom deposition onto Ag(100) and Ag(111) in ethylene glycol solution with surface-adsorbed PVP. We use these profiles to calculate the mean-first passage times and implement extensive Brownian dynamics simulations, which allows the kinetic effects to be quantitatively evaluated. Our results show that PVP films can regulate the flux of Ag atoms to be greater towards Ag(111) than Ag(100). PVP's preferential binding towards Ag(100) over Ag(111) gives PVP its flux-regulating capabilities through the lower free-energy barrier of Ag atoms to cross the lower-density PVP film on Ag(111) and enhanced Ag trapping by the extended PVP film on Ag(111). Under kinetic control, {100}-faceted nanocrystals will be formed when the Ag flux is greater towards Ag(111). The predicted kinetic Wulff shapes are in agreement with the analogous experimental system.

Silver-Loaded Aluminosilicate Aerogels As Iodine Sorbents.

PubMed

Riley, Brian J; Kroll, Jared O; Peterson, Jacob A; Matyáš, Josef; Olszta, Matthew J; Li, Xiaohong; Vienna, John D

2017-09-27

In this paper, aluminosilicate aerogels were used as scaffolds for silver nanoparticles to capture I 2 (g). The starting materials for these scaffolds included Na-Al-Si-O and Al-Si-O aerogels, both synthesized from metal alkoxides. The Ag 0 particles were added by soaking the aerogels in aqueous AgNO 3 solutions followed by drying and Ag + reduction under H 2 /Ar to form Ag 0 crystallites within the aerogel matrix. In some cases, aerogels were thiolated with 3-(mercaptopropyl)trimethoxysilane as an alternative method for binding Ag + . During the Ag + -impregnation steps, for the Na-Al-Si-O aerogels, Na was replaced with Ag, and for the Al-Si-O aerogels, Si was replaced with Ag. The Ag-loading of thiolated versus nonthiolated Na-Al-Si-O aerogels was comparable at ∼35 atomic %, whereas the Ag-loading in unthiolated Al-Si-O aerogels was significantly lower at ∼7 atomic % after identical treatment. Iodine loadings in both thiolated and unthiolated Ag 0 -functionalized Na-Al-Si-O aerogels were >0.5 m I m s -1 (denoting the mass of iodine captured per starting mass of the sorbent) showing almost complete utilization of the Ag through chemisorption to form AgI. Iodine loading in the thiolated and Ag 0 -functionalized Al-Si-O aerogel was 0.31 m I m s -1 . The control of Ag uptake over solution residence time and [Ag] demonstrates the ability to customize the Ag-loading in the base sorbent to regulate the loading capacity of iodine.

Structural and Solar Cell Properties of a Ag-Containing Cu2ZnSnS4 Thin Film Derived from Spray Pyrolysis.

PubMed

Nguyen, Thi Hiep; Kawaguchi, Takato; Chantana, Jakapan; Minemoto, Takashi; Harada, Takashi; Nakanishi, Shuji; Ikeda, Shigeru

2018-02-14

A silver (Ag)-incorporated kesterite Cu 2 ZnSnS 4 (CZTS) thin film was fabricated by a facile spray pyrolysis method. Crystallographic analyses indicated successful incorporation of various amounts of Ag up to a Ag/(Ag + Cu) ratio of ca. 0.1 into the crystal lattice of CZTS in a homogeneous manner without formation of other impurity compounds. From the results of morphological investigations, Ag-incorporated films had larger crystal grains than the CZTS film. The sample with a relatively low Ag content (Ag/(Ag + Cu) of ca. 0.02) had a compact morphology without appreciable voids and pinholes. However, an increase in the Ag content in the CZTS film (Ag/(Ag + Cu) ca. 0.10) induced the formation of a large number of pinholes. As can be expected from these morphological properties, the best sunlight conversion efficiency was obtained by the solar cell based on the film with Ag/(Ag + Cu) of ca. 0.02. Electrostructural analyses of the devices suggested that the Ag-incorporated film in the device achieved reduction in the amounts of unfavorable copper on zinc antisite defects compared to the bare CZTS film. Moreover, the use of a Ag-incorporated film improved band alignment at the CdS(buffer)-CZTS interface. These alterations should also contribute to enhancement of device properties.

A research on shape-controllable synthesis of Ag3PO4/AgBr and its degradation of ciprofloxacin.

PubMed

Chen, Jingran; Yang, Xingyu; Zhu, Chenyu; Xie, Xin; Lin, Cuiping; Zhao, Yalei; Yan, Qishe

2018-03-01

Antibiotic ciprofloxacin is one of the commonly used broad spectrum fluoroquinolone human and veterinary drugs. Because of the overuse of human beings, the presence of ciprofloxacin has been detected in a variety of environmental matrices. To solve this problem, a facile, environmentally-friendly Ag 3 PO 4 /AgBr composite photocatalyst was synthesized by a simple precipitation method at room temperature in the presence of cetyltrimethyl ammonium bromide (CTAB). CTAB was served as surfactant and the source of bromide ions. The as-prepared Ag 3 PO 4 /AgBr microspheres were characterized by means of powder X-ray diffraction (XRD), scanning electron microscope (SEM) and UV-visible diffuse reflectance spectroscopy (UV-vis DRS). The results revealed that the Ag 3 PO 4 /AgBr sample (synthesized with CTAB, 0.8 g) exhibited the highest photocatalytic activity to the photodegradation rate of 96.36%. Moreover, mechanism detection experiment indicated that h + was the major active species in the degradation process. So the enhanced photocatalytic activity of Ag 3 PO 4 /AgBr composites is attributed to its excellent separation of photogenerated electron-hole pairs through Ag 3 PO 4 /AgBr heterojunction. Also, Ag 3 PO 4 /AgBr heterojunction has a lower band gap compared to pure Ag 3 PO 4 and pure AgBr, so higher efficiency of light harvesting is equipped.

Synthesis and characterization of Ag+ ion conducting glassy electrolytes

NASA Astrophysics Data System (ADS)

Chandra, Angesh; Bhatt, Alok; Chandra, Archana

2013-07-01

Synthesis and characterization of new Ag+ ion conducting glassy systems: x[0.75AgI:0.25AgC1]: (1 - x)[Ag2O:P2O5], where 0.1 < x < 1 in molar weight fraction, are reported. The present glassy electrolytes have been synthesized by melt-quench technique using a high-speed twin roller-quencher. An alternate host salt: "quenched [0.75AgI:0.25AgC1] mixed system/solid solution", has been used in place of the traditional host AgI. The compositional dependence conductivity studies on the glassy systems: x[0.75AgI:0.25AgC1]:(1 - x)[Ag2O:P2O5] as well as xAgI:(1 - x)[Ag2O:P2O5] prepared identically, indicated that the composition at x = 0.75 exhibited the highest room temperature conductivity (σ ~ 5.5 x 10-3 S cm-1). The composition: 0.75[0.75AgI:0.25AgC1]:0.25[Ag2O:P2O5] has been referred to as optimum conducting composition (OCC). The some basic ion transport parameters viz. ionic conductivity (σ), ionic mobility (μ), mobile ion concentration (n), ionic drift velocity (vd), ion transference number (tion) and activation energy (Ea) values have been characterized with the help of various experimental techniques. A solid state battery was fabricated and its basic cell parameters calculated.

Photovoltaic Properties and Ultrafast Plasmon Relaxation Dynamics of Diamond-Like Carbon Nanocomposite Films with Embedded Ag Nanoparticles.

PubMed

Meškinis, Šarūnas; Peckus, Domantas; Vasiliauskas, Andrius; Čiegis, Arvydas; Gudaitis, Rimantas; Tamulevičius, Tomas; Yaremchuk, Iryna; Tamulevičius, Sigitas

2017-12-01

Ultrafast relaxation dynamics of diamond-like carbon (DLC) films with embedded Ag nanoparticles (DLC:Ag) and photovoltaic properties of heterojunctions consisting of DLC:Ag and crystalline silicon (DLC:Ag/Si) were investigated by means of transient absorption (TAS) spectroscopy and photovoltaic measurements. The heterojunctions using both p type and n type silicon were studied. It was found that TAS spectra of DLC:Ag films were dependent on the used excitation wavelength. At wavelengths where Ag nanoparticles absorbed light most intensively, only DLC signal was registered. This result is in good accordance with an increase of the DLC:Ag/Si heterojunction short circuit current and open circuit voltage with the excitation wavelength in the photovoltaic measurements. The dependence of the TAS spectra of DLC:Ag films and photovoltaic properties of DLC:Ag/Si heterostructures on the excitation wavelength was explained as a result of trapping of the photoexcited hot charge carriers in DLC matrix. The negative photovoltaic effect was observed for DLC:Ag/p-Si heterostructures and positive ("conventional") for DLC:Ag/n-Si ones. It was explained by the excitation of hot plasmonic holes in the Ag nanoparticles embedded into DLC matrix. Some decrease of DLC:Ag/Si heterostructures photovoltage as well as photocurrent with DLC:Ag film thickness was observed, indicating role of the interface in the charge transfer process of photocarriers excited in Ag nanoparticles.

Photovoltaic Properties and Ultrafast Plasmon Relaxation Dynamics of Diamond-Like Carbon Nanocomposite Films with Embedded Ag Nanoparticles

NASA Astrophysics Data System (ADS)

Meškinis, Šarūnas; Peckus, Domantas; Vasiliauskas, Andrius; Čiegis, Arvydas; Gudaitis, Rimantas; Tamulevičius, Tomas; Yaremchuk, Iryna; Tamulevičius, Sigitas

2017-04-01

Ultrafast relaxation dynamics of diamond-like carbon (DLC) films with embedded Ag nanoparticles (DLC:Ag) and photovoltaic properties of heterojunctions consisting of DLC:Ag and crystalline silicon (DLC:Ag/Si) were investigated by means of transient absorption (TAS) spectroscopy and photovoltaic measurements. The heterojunctions using both p type and n type silicon were studied. It was found that TAS spectra of DLC:Ag films were dependent on the used excitation wavelength. At wavelengths where Ag nanoparticles absorbed light most intensively, only DLC signal was registered. This result is in good accordance with an increase of the DLC:Ag/Si heterojunction short circuit current and open circuit voltage with the excitation wavelength in the photovoltaic measurements. The dependence of the TAS spectra of DLC:Ag films and photovoltaic properties of DLC:Ag/Si heterostructures on the excitation wavelength was explained as a result of trapping of the photoexcited hot charge carriers in DLC matrix. The negative photovoltaic effect was observed for DLC:Ag/p-Si heterostructures and positive ("conventional") for DLC:Ag/n-Si ones. It was explained by the excitation of hot plasmonic holes in the Ag nanoparticles embedded into DLC matrix. Some decrease of DLC:Ag/Si heterostructures photovoltage as well as photocurrent with DLC:Ag film thickness was observed, indicating role of the interface in the charge transfer process of photocarriers excited in Ag nanoparticles.

Magnetic susceptibility, artifact volume in MRI, and tensile properties of swaged Zr-Ag composites for biomedical applications.

PubMed

Imai, Haruki; Tanaka, Yoji; Nomura, Naoyuki; Doi, Hisashi; Tsutsumi, Yusuke; Ono, Takashi; Hanawa, Takao

2017-02-01

Zr-Ag composites were fabricated to decrease the magnetic susceptibility by compensating for the magnetic susceptibility of their components. The Zr-Ag composites with a different Zr-Ag ratio were swaged, and their magnetic susceptibility, artifact volume, and mechanical properties were evaluated by magnetic balance, three-dimensional (3-D) artifact rendering, and a tensile test, respectively. These properties were correlated with the volume fraction of Ag using the linear rule of mixture. We successfully obtained the swaged Zr-Ag composites up to the reduction ratio of 96% for Zr-4, 16, 36, 64Ag and 86% for Zr-81Ag. However, the volume fraction of Ag after swaging tended to be lower than that before swaging, especially for Ag-rich Zr-Ag composites. The magnetic susceptibility of the composites linearly decreased with the increasing volume fraction of Ag. No artifact could be estimated with the Ag volume fraction in the range from 93.7% to 95.4% in three conditions. Young's modulus, ultimate tensile strength (UTS), and 0.2% yield strength of Zr-Ag composites showed slightly lower values compared to the estimated values using a linear rule of mixture. The decrease in magnetic susceptibility of Zr and Ag by alloying or combining would contribute to the decrease of the Ag fraction, leading to the improvement of mechanical properties. Copyright © 2016 Elsevier Ltd. All rights reserved.

Preparation and structure of Na2Ag5Fe3(P2O7)4 -Ag metal composite: Insights on electrochemistry

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

Zhang, Yiman; Marschilok, Amy C.; Takeuchi, Esther S.

ABSTRACT Ag 7Fe 3(P 2O 7) 4is a 3D structured material which has been recently studied as a possible cathode material for lithium batteries. Notably, Na 7Fe 3(P 2O 7) 4is reported to be a fast-ion conductor, yet poor electrical conductor. Here, partial replacement of Na +for Ag +yielded Na 2Ag 5Fe 3(P 2O 7) 4pyrophosphate framework where the formation of Ag metal is proposed to increase the intrinsic low electrical conductivity of this polyanion electrode. Specifically, the Ag 5Na 2Fe 3(P 2O 7) 4-Ag composite is synthesized via chemical reduction of Ag 7Fe 3(P 2O 7) 4using NaBH 4.more » The occupancy of Ag +and Na +in each site was determined via Rietveld analysis of the diffraction pattern. Electrochemistry of the Ag 5Na 2Fe 3(P 2O 7) 4-Ag metal composite was explored with voltammetry and galvanostatic charge/discharge cycling. The Ag 5Na 2Fe 3(P 2O 7) 4-Ag metal composite electrodes displayed good rate capability assisted by the presence of Ag metal from the chemical reduction and in-situ electrochemical formation of a Ag conductive network.« less

The isotopic composition and concentration of Ag in iron meteorites and the origin of exotic silver

NASA Technical Reports Server (NTRS)

Kaiser, T.; Wasserburg, G. J.

1983-01-01

The isotopic composition of Ag and the concentration of Ag and Pd in Canyon Diablo (IA), Grant (IIIB), Santa Clara, Tlacotepec and Warburton Range (IVB), Pinon and Deep Springs (anom) were analyzed. Troilite from Santa Clara and from Grant was also studied. With the exception of IA, all the meteorites were enriched in Ag-107 by about 2%-212% and the ratio of Ag-107/Ag-109 in the metal phase was found to be greater than the terrestrial value. Ag of anomalous isotopic composition was found to be common in all IVB and anomalous meteorites. A correlation of Ag-107/Ag-109 with Pd/Ag was established except for the iron meteorite of Santa Clara. The excess Ag-107 is thought to result from the decay of Pd-107. The Grant data appear to represent a Pd-107-Ag-107 isochron and indicate that the cooling rate at elevated temperatures was rapid enough to preserve the isotopic differences between metal and troilite. The data suggest that Ag in Santa Clara is made up of almost pure Ag-107 produced from Pd-107 decay and Ag-109 produced by nuclear reactions with only a small amount of 'normal' Ag. This indicates an intense energetic particle bombardment history in the early solar system which occurred after the formation of small planetary bodies.

Interactions between cauliflower and Rhizoctonia anastomosis groups with different levels of aggressiveness

PubMed Central

Pannecoucque, Joke; Höfte, Monica

2009-01-01

Background The soil borne fungus Rhizoctonia is one of the most important plant pathogenic fungi, with a wide host range and worldwide distribution. In cauliflower (Brassica oleracea var. botrytis), several anastomosis groups (AGs) including both multinucleate R. solani and binucleate Rhizoctonia species have been identified showing different levels of aggressiveness. The infection and colonization process of Rhizoctonia during pathogenic interactions is well described. In contrast, insights into processes during interactions with weak aggressive or non-pathogenic isolates are limited. In this study the interaction of cauliflower with seven R. solani AGs and one binucleate Rhizoctonia AG differing in aggressiveness, was compared. Using microscopic and histopathological techniques, the early steps of the infection process, the colonization process and several host responses were studied. Results For aggressive Rhizoctonia AGs (R. solani AG 1-1B, AG 1-1C, AG 2-1, AG 2-2 IIIb and AG 4 HGII), a higher developmental rate was detected for several steps of the infection process, including directed growth along anticlinal cell walls and formation of T-shaped branches, infection cushion formation and stomatal penetration. Weak or non-aggressive AGs (R. solani AG 5, AG 3 and binucleate Rhizoctonia AG K) required more time, notwithstanding all AGs were able to penetrate cauliflower hypocotyls. Histopathological observations indicated that Rhizoctonia AGs provoked differential host responses and pectin degradation. We demonstrated the pronounced deposition of phenolic compounds and callose against weak and non-aggressive AGs which resulted in a delay or complete block of the host colonization. Degradation of pectic compounds was observed for all pathogenic AGs, except for AG 2-2 IIIb. Ranking the AGs based on infection rate, level of induced host responses and pectin degradation revealed a strong correlation with the disease severity caused by the AGs. Conclusion The differences in aggressiveness towards cauliflower observed among Rhizoctonia AGs correlated with the infection rate, induction of host defence responses and pectin breakdown. All Rhizoctonia AGs studied penetrated the plant tissue, indicating all constitutive barriers of cauliflower were defeated and differences in aggressiveness were caused by inducible defence responses, including cell wall fortifications with phenolic compounds and callose. PMID:19622152

Reducing Strength Prevailing at Root Surface of Plants Promotes Reduction of Ag+ and Generation of Ag0/Ag2O Nanoparticles Exogenously in Aqueous Phase

PubMed Central

Pardha-Saradhi, Peddisetty; Yamal, Gupta; Peddisetty, Tanuj; Sharmila, Peddisetty; Nagar, Shilpi; Singh, Jyoti; Nagarajan, Rajamani; Rao, Kottapalli S.

2014-01-01

Potential of root system of plants from wide range of families to effectively reduce membrane impermeable ferricyanide to ferrocyanide and blue coloured 2,6-dichlorophenol indophenol (DCPIP) to colourless DCPIPH2 both under non-sterile and sterile conditions, revealed prevalence of immense reducing strength at root surface. As generation of silver nanoparticles (NPs) from Ag+ involves reduction, present investigations were carried to evaluate if reducing strength prevailing at surface of root system can be exploited for reduction of Ag+ and exogenous generation of silver-NPs. Root system of intact plants of 16 species from 11 diverse families of angiosperms turned clear colorless AgNO3 solutions, turbid brown. Absorption spectra of these turbid brown solutions showed silver-NPs specific surface plasmon resonance peak. Transmission electron microscope coupled with energy dispersive X-ray confirmed the presence of distinct NPs in the range of 5–50 nm containing Ag. Selected area electron diffraction and powder X-ray diffraction patterns of the silver NPs showed Bragg reflections, characteristic of crystalline face-centered cubic structure of Ag0 and cubic structure of Ag2O. Root system of intact plants raised under sterile conditions also generated Ag0/Ag2O-NPs under strict sterile conditions in a manner similar to that recorded under non-sterile conditions. This revealed the inbuilt potential of root system to generate Ag0/Ag2O-NPs independent of any microorganism. Roots of intact plants reduced triphenyltetrazolium to triphenylformazon and impermeable ferricyanide to ferrocyanide, suggesting involvement of plasma membrane bound dehydrogenases in reduction of Ag+ and formation of Ag0/Ag2O-NPs. Root enzyme extract reduced triphenyltetrazolium to triphenylformazon and Ag+ to Ag0 in presence of NADH, clearly establishing potential of dehydrogenases to reduce Ag+ to Ag0, which generate Ag0/Ag2O-NPs. Findings presented in this manuscript put forth a novel, simple, economically viable and green protocol for synthesis of silver-NPs under ambient conditions in aqueous phase, using root system of intact plants. PMID:25184239

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

NASA Astrophysics Data System (ADS)

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

2015-01-01

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

The role of exopolymeric substances in the bioaccumulation and toxicity of Ag nanoparticles to algae

NASA Astrophysics Data System (ADS)

Zhou, Kaijun; Hu, Yi; Zhang, Luqing; Yang, Kun; Lin, Daohui

2016-09-01

Exopolymeric substances (EPS) have an important role in bioaccumulation and toxicity of nanoparticles (NPs) to algae, which warrants specific studies. The interaction of EPS with citrate and polyvinyl pyrrolidone (PVP) coated AgNPs (C-AgNPs and P-AgNPs, respectively) and its roles in bioaccumulation and toxicity of the AgNPs to Chlorella pyrenoidosa were investigated. The amino and aromatic carboxylic groups in the EPS were involved in the EPS-AgNP interactions. Compared with Ag+, C-AgNPs had comparable total bioaccumulation but greater absorption by intact algae with EPS; P-AgNPs had the smallest total bioaccumulation and were mainly adsorbed on algal surfaces. With EPS removed, the total bioaccumulations and surface adsorptions for the three Ag species decreased but the cell internalizations increased; the 96 h half growth inhibition concentrations decreased, indicating EPS alleviated the algal toxicity of Ag. The cell-internalized but not the adsorbed AgNPs could contribute to the nanotoxicity. The EPS could bind both AgNPs and Ag+, and thus inhibited the cell internalization and the nanotoxicity. However, the EPS-bound Ag on the cell surfaces would migrate along with the algae and be biologically amplified in the aquatic food chains, presenting ecological risks. These results are helpful for understanding the fate and ecological effects of NPs.

Silver(i) complexes with 1'-(diphenylphosphino)-1-cyanoferrocene: the art of improvisation in coordination.

PubMed

Škoch, Karel; Uhlík, Filip; Císařová, Ivana; Štěpnička, Petr

2016-06-28

1'-(Diphenylphosphino)-1-cyanoferrocene () reacts with silver(i) halides at a 1 : 1 metal-to-ligand ratio to afford the heterocubane complexes [Ag(μ3-X)(-κP)]4, where X = Cl (), Br (), and I (). In addition, the reaction with AgCl with 2 equiv. of leads to chloride-bridged dimer [(μ-Cl)2{Ag(-κP)2}2] () and, presumably, also to [(μ(P,N)-){AgCl(-κP)}]2 (). While similar reactions with AgCN furnished only the insoluble coordination polymer [(-κP)2Ag(NC)Ag(CN)]n (), those with AgSCN afforded the heterocubane [Ag(-κP)(μ-SCN-S,S,N)]4 () and the thiocyanato-bridged disilver(i) complex [Ag(-κP)2(μ-SCN-S,N)]2 (), thereby resembling reactions in the AgCl- system. Attempted reactions with AgF led to ill-defined products, among which [Ag(-κP)2(μ-HF2)]2 () and [(μ-SiF6){Ag(-κP)2}2] () could be identified. The latter compound was prepared also from Ag2[SiF6] and . Reactions between and AgClO4 or Ag[BF4] afforded disilver complexes [(μ(P,N)-)Ag(ClO4-κO)]2 () and [(μ(P,N)-)Ag(BF4-κF)]2 () featuring pseudolinear Ag(i) centers that are weakly coordinated by the counter anions. A similar reaction with Ag[SbF6] followed by crystallization from ethyl acetate produced an analogous complex, albeit with coordinated solvent, [(μ(P,N)-)Ag(AcOEt-κO)]2[SbF6]2 (). Ultimately, a compound devoid of any additional ligands at the Ag(i) centers, [(μ(P,N)-)Ag]2[B(C6H3(CF3)2-3,5)4]2 (), was obtained from the reaction of with silver(i) tetrakis[3,5-bis(trifluoromethyl)phenyl]borate. The reaction of Ag[BF4] with two equivalents of produced unique coordination polymer [Ag(-κP)(μ(P,N)-)]n[BF4]n (), the structure of which contained one of the phosphinoferrocene ligands coordinated as a P,N-chelate and the other forming a bridge to an adjacent Ag(i) center. All of these compounds were structurally characterized by single-crystal X-ray crystallography, revealing that the lengths of the bonds between silver and its anionic ligand(s) typically exceed the sum of the respective covalent radii, which is in line with the results of theoretical calculations at the density-functional theory (DFT) level, suggesting that standard covalent dative bonds are formed between silver and phosphorus (soft acid/soft base interactions) while the interactions between silver and the ligand's nitrile group (if coordinated) or the supporting anion are of predominantly electrostatic nature.

Profile of von Willebrand factor antigen and von Willebrand factor propeptide in an overall TIA and ischaemic stroke population and amongst subtypes.

PubMed

Tobin, W O; Kinsella, J A; Kavanagh, G F; O'Donnell, J S; McGrath, R T; Tierney, S; Egan, B; Feeley, T M; Coughlan, T; Collins, D R; O'Neill, D; Murphy, Sjx; Lim, S J; Murphy, R P; McCabe, Djh

2017-04-15

Von Willebrand factor propeptide (VWF:Ag II) is proposed to be a more sensitive marker of acute endothelial activation than von Willebrand factor antigen (VWF:Ag). Simultaneous data on VWF:Ag and VWF:Ag II profiles are very limited following TIA and ischaemic stroke. In this prospective, observational, case-control study, plasma VWF:Ag and VWF:Ag II levels were quantified in 164 patients≤4weeks of TIA or ischaemic stroke (baseline), and then ≥14days (14d) and ≥90days (90d) later, and compared with those from 27 healthy controls. TIA and stroke subtyping was performed according to the TOAST classification. The relationship between VWF:Ag and VWF:Ag II levels and platelet activation status was assessed. 'Unadjusted' VWF:Ag and VWF:Ag II levels were higher in patients at baseline, 14d and 90d than in controls (p≤0.03). VWF:Ag levels remained higher in patients than controls at baseline (p≤0.03), but not at 14d or 90d after controlling for differences in age or hypertension, and were higher in patients at baseline and 90d after controlling for smoking status (p≤0.04). 'Adjusted' VWF:Ag II levels were not higher in patients than controls after controlling for age, hypertension or smoking (p≥0.1). Patients with symptomatic carotid stenosis (N=46) had higher VWF:Ag and VWF:Ag II levels than controls at all time-points (p≤0.002). There was no significant correlation between platelet activation status and VWF:Ag or VWF:Ag II levels. VWF:Ag and VWF:Ag II levels are increased in an overall TIA and ischaemic stroke population, especially in patients with recently symptomatic carotid stenosis. VWF:Ag II was not superior to VWF:Ag at detecting acute endothelial activation in this cohort and might reflect timing of blood sampling in our study. Copyright © 2017 Elsevier B.V. All rights reserved.

XPS and Ag L3-edge XANES characterization of silver and silver-gold sulfoselenides

NASA Astrophysics Data System (ADS)

Mikhlin, Yuri L.; Pal'yanova, Galina A.; Tomashevich, Yevgeny V.; Vishnyakova, Elena A.; Vorobyev, Sergey A.; Kokh, Konstantin A.

2018-05-01

Gold and silver sulfoselenides are of interest as materials with high ionic conductivity and promising magnetoresistive, thermoelectric, optical, and other physico-chemical properties, which are strongly dependent on composition and structure. Here, we applied X-ray photoelectron spectroscopy and Ag L3 X-ray absorption near-edge structure (XANES) to study the electronic structures of low-temperature compounds and solid solutions Ag2SxSe1-x (0 < x < 1), AgAuS, and Ag3AuSxSe2-x (x = 0, 1, 2). Upon substitution of Se with S, a steady increase in the positive charge at Ag(I) sites and only minor changes in the local charge at chalcogen atoms were found from the photoelectron Ag 3d, S 2p, Se 3d, and Ag M4,5VV Auger spectra. The intensity of the Ag L3-edge peak, which is known to correlate with hole counts in the Ag 4d shell having a formal d10 configuration, was enhanced by 20-25% from Ag2Se to Ag2S and from Ag3AuSe2 to Ag3AuS2. The effect of gold is more pronounced, and the number of Ag d holes and the negative charge of S and Se notably decreased for Au-containing compounds; in particular, the Ag L3-edge peak is about 35% lower for AgAuS relative to Ag2S. At the same time, the Au 4f binding energy and, therefore, charge at Au(I) sites increase with increasing S content due to the transfer of electron density from Au to Ag atoms. It was concluded that the effects mainly originate from shortening of the metal-chalcogen and especially the Ausbnd Ag interatomic distances in substances having similar coordination geometry.

Ethylene sensing by silver(I) salt-impregnated luminescent films

USDA-ARS?s Scientific Manuscript database

Luminescent oligomer /polymer films impregnated with Ag(I) salts are effective sensors for small gas molecules such as ethylene. Films composed of various Ag(I) salts (i.e. AgBF4, AgSbF6, AgB(C6F5)4, AgClO4 and AgOTf) and polymers (i.e. poly(vinylphenylketone) (PVPK), polystyrene (PS) or oligomers (...

How I Learned to Stop Worrying and Love Eclipsing Binaries

NASA Astrophysics Data System (ADS)

Moe, Maxwell Cassady

Relatively massive B-type stars with closely orbiting stellar companions can evolve to produce Type Ia supernovae, X-ray binaries, millisecond pulsars, mergers of neutron stars, gamma ray bursts, and sources of gravitational waves. However, the formation mechanism, intrinsic frequency, and evolutionary processes of B-type binaries are poorly understood. As of 2012, the binary statistics of massive stars had not been measured at low metallicities, extreme mass ratios, or intermediate orbital periods. This thesis utilizes large data sets of eclipsing binaries to measure the physical properties of B-type binaries in these previously unexplored portions of the parameter space. The updated binary statistics provide invaluable insight into the formation of massive stars and binaries as well as reliable initial conditions for population synthesis studies of binary star evolution. We first compare the properties of B-type eclipsing binaries in our Milky Way Galaxy and the nearby Magellanic Cloud Galaxies. We model the eclipsing binary light curves and perform detailed Monte Carlo simulations to recover the intrinsic properties and distributions of the close binary population. We find the frequency, period distribution, and mass-ratio distribution of close B-type binaries do not significantly depend on metallicity or environment. These results indicate the formation of massive binaries are relatively insensitive to their chemical abundances or immediate surroundings. Second, we search for low-mass eclipsing companions to massive B-type stars in the Large Magellanic Cloud Galaxy. In addition to finding such extreme mass-ratio binaries, we serendipitously discover a new class of eclipsing binaries. Each system comprises a massive B-type star that is fully formed and a nascent low-mass companion that is still contracting toward its normal phase of evolution. The large low-mass secondaries discernibly reflect much of the light they intercept from the hot B-type stars, thereby producing sinusoidal variations in perceived brightness as they orbit. These nascent eclipsing binaries are embedded in the hearts of star-forming emission nebulae, and therefore provide a unique snapshot into the formation and evolution of massive binaries and stellar nurseries. We next examine a large sample of B-type eclipsing binaries with intermediate orbital periods. To achieve such a task, we develop an automated pipeline to classify the eclipsing binaries, measure their physical properties from the observed light curves, and recover the intrinsic binary statistics by correcting for selection effects. We find the population of massive binaries at intermediate separations differ from those orbiting in close proximity. Close massive binaries favor small eccentricities and have correlated component masses, demonstrating they coevolved via competitive accretion during their formation in the circumbinary disk. Meanwhile, B-type binaries at slightly wider separations are born with large eccentricities and are weighted toward extreme mass ratios, indicating the components formed relatively independently and subsequently evolved to their current configurations via dynamical interactions. By using eclipsing binaries as accurate age indicators, we also reveal that the binary orbital eccentricities and the line-of-sight dust extinctions are anticorrelated with respect to time. These empirical relations provide robust constraints for tidal evolution in massive binaries and the evolution of the dust content in their surrounding environments. Finally, we compile observations of early-type binaries identified via spectroscopy, eclipses, long-baseline interferometry, adaptive optics, lucky imaging, high-contrast photometry, and common proper motion. We combine the samples from the various surveys and correct for their respective selection effects to determine a comprehensive nature of the intrinsic binary statistics of massive stars. We find the probability distributions of primary mass, secondary mass, orbital period, and orbital eccentricity are all interrelated. These updated multiplicity statistics imply a greater frequency of low-mass X-ray binaries, millisecond pulsars, and Type Ia supernovae than previously predicted.

Templated Atom-Precise Galvanic Synthesis and Structure Elucidation of a [Ag24Au(SR)18](-) Nanocluster.

PubMed

Bootharaju, Megalamane S; Joshi, Chakra P; Parida, Manas R; Mohammed, Omar F; Bakr, Osman M

2016-01-18

Synthesis of atom-precise alloy nanoclusters with uniform composition is challenging when the alloying atoms are similar in size (for example, Ag and Au). A galvanic exchange strategy has been devised to produce a compositionally uniform [Ag24Au(SR)18](-) cluster (SR: thiolate) using a pure [Ag25(SR)18](-) cluster as a template. Conversely, the direct synthesis of Ag24Au cluster leads to a mixture of [Ag(25-x)Au(x)(SR)18](-), x=1-8. Mass spectrometry and crystallography of [Ag24Au(SR)18](-) reveal the presence of the Au heteroatom at the Ag25 center, forming Ag24Au. The successful exchange of the central Ag of Ag25 with Au causes perturbations in the Ag25 crystal structure, which are reflected in the absorption, luminescence, and ambient stability of the particle. These properties are compared with those of Ag25 and Ag24Pd clusters with same ligand and structural framework, providing new insights into the modulation of cluster properties with dopants at the single-atom level. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Correlation between the size and the magnetic properties of Ag2+ clusters loaded on ceria surface and their catalytic performance in the total oxidation of propylene. EPR study

NASA Astrophysics Data System (ADS)

Hany, Sara; Skaf, Mira; Aouad, Samer; Gennequin, Cédric; Labaki, Madona; Abi-Aad, Edmond; Aboukaïs, Antoine

2018-03-01

Three different types of Ag2+ ions ("a", "b", and "c") have been identified and examined by electron paramagnetic resonance (EPR) on 10% wt Ag/CeO2 prepared by impregnation method. One of them, Ag2+(b), behaves differently than the two others, Ag2+(a) and Ag2+(c), under redox atmospheres. The fact that, in reducing conditions (vacuum, propylene, hydrogen, and carbon black), Ag2+(a) and Ag2+(c) species were more easily reduced than Ag2+(b) ones, could not explain the catalytic performance and stability of this latter species compared to the first ones in the reaction of total oxidation of propylene. The EPR technique evidenced that Ag2+(b) species form, upon propene oxidation, a cluster. This cluster is composed of two parallel electron spins (dimer) and three nuclear spins (trimer). It seems that before propylene oxidation, Ag2+(b) clusters were ferromagnetic. This ferromagnetic character of Ag2+(b) species may explain their better catalytic performance, in propylene oxidation, than those of Ag2+(a) and Ag2+(c) ones.

Synthesis of β-AgVO3 nanowires decorated with Ag2CrO4, with improved visible light photocatalytic performance

NASA Astrophysics Data System (ADS)

Ouyang, Qi; Li, Zhonghua; Liu, Jiawen

2018-05-01

Silver chromate‑silver vanadate (Ag2CrO4/β-AgVO3) heterojunction composites are synthesized through a facile precipitation process. The Ag2CrO4/β-AgVO3 hybrids obtained exhibit better photocatalytic activity in degradation of RhB than both pure Ag2CrO4 and β-AgVO3 under visible light irradiation. The 20 wt% Ag2CrO4/β-AgVO3 heterojunction possesses the best photocatalytic ability for degrading RhB: 24.4 times that of pristine β-AgVO3 nanowires and 3.2 times that of individual Ag2CrO4 particles. The phase of the nanocomposites was analyzed using x-ray diffraction as well as x-ray photoelectron spectroscopy. Their morphology was observed via scanning electron microscopy and transmission electron microscopy. The improvement in photocatalytic performance is chiefly ascribed to the synergies between Ag2CrO4/β-AgVO3 heterostructure, which can enhance the light absorbance ability and also accelerate the separation and transfer of photoinduced electrons and holes under visible light irradiation; this is also confirmed by UV–vis diffuse reflection spectrometry and fluorescence emission spectra.

A variable Ag-Cr-Oxalate channel lattice: [M(x)Ag(0.5)(-)(x)(H(2)O)(3)]@[Ag(2.5)Cr(C(2)O(4))(3)], M = K, Cs, Ag.

PubMed

Dean, Philip A W; Craig, Don; Dance, Ian; Russell, Vanessa; Scudder, Marcia

2004-01-26

Reaction of aqueous AgNO(3) with aqueous M(3)[Cr(ox)(3)] in >or=3:1 molar ratio causes the rapid growth of large, cherry-black, light-stable crystals which are not Ag(3)[Cr(ox)(3)], but [M(0.5)(H(2)O)(3)]@[Ag(2.5)Cr(ox)(3)] (ox(2)(-) = oxalate, C(2)O(4)(2)(-); M = Na, K, Cs, Ag, or mixtures of Ag and a group 1 element). The structure of these crystals contains an invariant channeled framework, with composition [[Ag(2.5)Cr(ox)(3)](-)(0.5)]( infinity ), constructed with [Cr(ox)(3)] coordination units linked by Ag atoms through centrosymmetric [Cr-O(2)C(2)O(2)-Ag](2) double bridges. The framework composition [Ag(2.5)Cr(ox)(3)](-)(0.5) occurs because one Ag is located on a 2-fold axis. Within the channels there is a well-defined and ordered set of six water molecules, strongly hydrogen bonded to each other and some of the oxalate O atoms. This invariant channel plus water structure accommodates group 1 cations, and/or Ag cations, in different locations and in variable proportions, but always coordinated by channel water and some oxalate O atoms. The general formulation of these crystals is therefore [M(x)Ag(0.5-x)(H(2)O)(3)]@[Ag(2.5)Cr(ox)(3)]. Five different crystals with this structure are reported, with compositions 1 Ag(0.5)[Ag(2.5)Cr(ox)(3)](H(2)O)(3), 2 Cs(0.19)Ag(0.31)[Ag(2.5)Cr(ox)(3)](H(2)O)(3), 3 K(0.28)Ag(0.22)[Ag(2.5)Cr(ox)(3)](H(2)O)(3), 4 Cs(0.41)Ag(0.09)[Ag(2.5)Cr(ox)(3)](H(2)O)(3), and 5 Cs(0.43)Ag(0.07) [Ag(2.5)Cr(ox)(3)](H(2)O)(3). All crystallize in space group C2/c, with a approximately 18.4, b approximately 14.6, c approximately 12.3 A, beta approximately 113 degrees. Pure Ag(3)[Cr(ox)(3)](H(2)O)(3), which has the same crystal structure (1), was obtained from water by treating Li(3)[Cr(ox)(3)] with excess AgNO(3). Complete dehydration of all of these compounds occurs between 30 and 100 degrees C, with loss of diffraction, but rehydration by exposure to H(2)O(g) at ambient temperature leads to recovery of the original diffraction pattern. In single crystals, this reversible dehydration-hydration occurs without visually evident crystal change, but with loss of mechanical strength. We postulate a general mechanism for transport of water molecules along the channels, associated with local partial collapses of the channel framework, with concomitant bending but little breaking of the host Ag-O and Cr-O bonds, which is readily reversed.

Real-time monitoring of the Trojan-horse effect of silver nanoparticles by using a genetically encoded fluorescent cell sensor.

PubMed

You, Fang; Tang, Wenqin; Yung, Lin-Yue Lanry

2018-04-26

Silver nanoparticles (AgNPs) are widely incorporated into commercial products due to their antimicrobial properties. As a consequence, concerns about the adverse effects induced by AgNPs to humans and the environment need to be carefully examined. The existing literature reveals that AgNPs exhibit certain toxic effects, but it remains to be proved whether AgNPs or the ionic silver (Ag+) released from AgNPs are the main toxic species. Here, a genetically encoded fluorescent protein sensor with high affinity to Ag+ was developed. The resulting sensor, MT2a-FRET, was found to be ratiometric, sensitive and selective toward only Ag+ but inert against AgNPs. This makes this sensor a potential useful tool for monitoring the real-time intracellular dissolutions of AgNPs. Our data supported that AgNPs display the "Trojan-horse" mechanism, where AgNPs are internalized by cells and undergo dissolution intracellularly. We further found that cells exhibited a detoxification ability to remove active Ag+ from cells in 48 hours.

One-pot electrodeposition of cobalt flower-decorated silver nanotrees for oxygen reduction reaction

NASA Astrophysics Data System (ADS)

Cho, Yun-Bin; Moon, Sinyoung; Lee, Chongmok; Lee, Youngmi

2017-02-01

In this paper, we demonstrate a simple fabrication of bimetallic silver (Ag) and cobalt (Co) nanostructures (AgCo) with various Ag to Co relative contents via electrochemical co-deposition. A series of AgCo catalysts was electrodeposited on glassy carbon (GC) electrodes at -0.57 V vs. SCE in the deposition solutions, containing Ag precursor, Co precursor, Triton X-100, and 0.3 M KNO3 aqueous solution, with various Ag to Co precursor concentration ratios (1:x, x was varied from 3 to 11). The films, deposited with the total deposition charge of 0.042C, were denoted as Ag1Cox. SEM and TEM analyses showed that Ag1Cox formed a structure consisted of flower-like Co grown on tree-like Ag backbones while it had more Co flowers with a greater x. The ORR activities were examined in 0.1 M NaOH solution with rotating disk electrode (RDE) voltammetry and Ag1Co7 showed the best catalytic activity. The co-deposition mechanism was further investigated by varying the deposition time of Ag1Co7. At the early stage of deposition, Ag-tree branches were formed predominantly, followed by the growth of flower-like Co nanostructures on the Ag nanotrees: More Co flowers were produced on Ag backbones with longer deposition time, being attributed to both a less negative reduction potential of Ag+ to Ag than Co2+ to Co and promoted Co2+ reduction on the initially formed Ag surface. Ag1Co7 electrodeposited for 200 s, consisted of ∼14% Co, showed the greatest ORR catalytic activity which was better or comparable to noble metal Pt.

SERS-activating effect of chlorides on borate-stabilized silver nanoparticles: formation of new reduced adsorption sites and induced nanoparticle fusion.

PubMed

Sloufová, Ivana; Sisková, Karolína; Vlcková, Blanka; Stepánek, Josef

2008-04-28

Changes in morphology, surface reactivity and surface-enhancement of Raman scattering induced by modification of borate-stabilized Ag nanoparticles by adsorbed chlorides have been explored using TEM, EDX analysis and SERS spectra of probing adsorbate 2,2'-bipyridine (bpy) excited at 514.5 nm and evaluated by factor analysis. At fractional coverages of the parent Ag nanoparticles by adsorbed chlorides <0.6, the Ag colloid/Cl(-)/bpy systems were found to be constituted by fractal aggregates of Ag nanoparticles fairly uniform in size (10 +/- 2 nm) and SERS spectra of Ag(+)-bpy surface species were detected. The latter result was interpreted in terms of the presence of oxidized Ag(+) and/or Ag(n)(+) adsorption sites, which have been encountered also in systems with the chemically untreated Ag nanoparticles. At chloride coverages >0.6, a fusion of fractal aggregates into the compact aggregates of touching and/or interpenetrating Ag nanoparticles has been observed and found to be accompanied by the formation of another surface species, Ag-bpy, as well as by the increase of the overall SERS enhancement of bpy by factor of 40. The same Ag-bpy surface species has been detected under the strongly reducing conditions of reduction of silver nitrate by sodium borohydride in the presence of bpy. The formation of Ag-bpy is thus interpreted in terms of the stabilization of reduced Ag(0) adsorption sites by adsorbed bpy. The formation of reduced adsorption sites on Ag nanoparticle surfaces at chloride coverages >0.6 is discussed in terms of local changes in the work function of Ag. Finally, the SERS spectral detection of Ag-bpy species is proposed as a tool for probing the presence of reduced Ag(0) adsorption sites in systems with chemically modified Ag nanoparticles.

Defects responsible for abnormal n-type conductivity in Ag-excess doped PbTe thermoelectrics

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

Ryu, Byungki, E-mail: byungkiryu@keri.re.kr; Lee, Jae Ki; Lee, Ji Eun

Density functional calculations have been performed to investigate the role of Ag defects in PbTe thermoelectric materials. Ag-defects can be either donor, acceptor, or isovalent neutral defect. When Ag is heavily doped in PbTe, the neutral (Ag-Ag) dimer defect at Pb-site is formed and the environment changes to the Pb-rich/Te-poor condition. Under Pb-rich condition, the ionized Ag-interstitial defect (Ag{sub I}{sup +}) becomes the major donor. The formation energy of Ag{sub I}{sup +} is smaller than other native and Ag-related defects. Also it is found that Ag{sub I}{sup +} is an effective dopant. There is no additional impurity state near themore » band gap and the conduction band minimum. The charge state of Ag{sub I}{sup +} defect is maintained even when the Fermi level is located above the conduction band minimum. The diffusion constant of Ag{sub I}{sup +} is calculated based on the temperature dependent Fermi level, formation energy, and migration energy. When T > 550 K, the diffusion length of Ag within a few minutes is comparable to the grain size of the polycrystalline PbTe, implying that Ag is dissolved into PbTe and this donor defect is distributed over the whole lattice in Ag-excess doped polycrystalline PbTe. The predicted solubility of Ag{sub I}{sup +} well explains the increased electron carrier concentration and electrical conductivity reported in Ag-excess doped polycrystalline PbTe at T = 450–750 K [Pei et al., Adv. Energy Mater. 1, 291 (2011)]. In addition, we suggest that this abnormal doping behavior is also found for Au-doped PbTe.« less

The structural conversion from α-AgVO3 to β-AgVO3: Ag nanoparticle decorated nanowires with application as cathode materials for Li-ion batteries.

PubMed

McNulty, David; Ramasse, Quentin; O'Dwyer, Colm

2016-09-15

The majority of electrode materials in batteries and related electrochemical energy storage devices are fashioned into slurries via the addition of a conductive additive and a binder. However, aggregation of smaller diameter nanoparticles in current generation electrode compositions can result in non-homogeneous active materials. Inconsistent slurry formulation may lead to inconsistent electrical conductivity throughout the material, local variations in electrochemical response, and the overall cell performance. Here we demonstrate the hydrothermal preparation of Ag nanoparticle (NP) decorated α-AgVO 3 nanowires (NWs) and their conversion to tunnel structured β-AgVO 3 NWs by annealing to form a uniform blend of intercalation materials that are well connected electrically. The synthesis of nanostructures with chemically bound conductive nanoparticles is an elegant means to overcome the intrinsic issues associated with electrode slurry production, as wire-to-wire conductive pathways are formed within the overall electrode active mass of NWs. The conversion from α-AgVO 3 to β-AgVO 3 is explained in detail through a comprehensive structural characterization. Meticulous EELS analysis of β-AgVO 3 NWs offers insight into the true β-AgVO 3 structure and how the annealing process facilitates a higher surface coverage of Ag NPs directly from ionic Ag content within the α-AgVO 3 NWs. Variations in vanadium oxidation state across the surface of the nanowires indicate that the β-AgVO 3 NWs have a core-shell oxidation state structure, and that the vanadium oxidation state under the Ag NP confirms a chemically bound NP from reduction of diffused ionic silver from the α-AgVO 3 NWs core material. Electrochemical comparison of α-AgVO 3 and β-AgVO 3 NWs confirms that β-AgVO 3 offers improved electrochemical performance. An ex situ structural characterization of β-AgVO 3 NWs after the first galvanostatic discharge and charge offers new insight into the Li + reaction mechanism for β-AgVO 3 . Ag + between the van der Waals layers of the vanadium oxide is reduced during discharge and deposited as metallic Ag, the vacant sites are then occupied by Li + .

WIYN OPEN CLUSTER STUDY. XXXVI. SPECTROSCOPIC BINARY ORBITS IN NGC 188

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

Geller, Aaron M.; Mathieu, Robert D.; Harris, Hugh C.

2009-04-15

We present 98 spectroscopic binary orbits resulting from our ongoing radial velocity survey of the old (7 Gyr) open cluster NGC 188. All but 13 are high-probability cluster members based on both radial velocity and proper motion membership analyses. Fifteen of these member binaries are double lined. Our stellar sample spans a magnitude range of 10.8 {<=}V{<=} 16.5 (1.14-0.92 M {sub sun}) and extends spatially to 17 pc ({approx}13 core radii). All of our binary orbits have periods ranging from a few days to on the order of 10{sup 3} days, and thus are hard binaries that dynamically power themore » cluster. For each binary, we present the orbital solutions and place constraints on the component masses. Additionally, we discuss a few binaries of note from our sample, identifying a likely blue straggler-blue straggler binary system (7782), a double-lined binary with a secondary star which is underluminous for its mass (5080), two potential eclipsing binaries (4705 and 5762), and two binaries which are likely members of a quadruple system (5015a and 5015b)« less

Renal evaluation of Aotus azarai infulatus by ultrasonography and serum chemistry profile.

PubMed

Lins, Fernanda Luiza de Miranda Lins e; Monteiro, Frederico Ozanan Barros; Takeshita, Rafaela Sayuri Cicalise; da Silva, Gilmara Abreu; Faturi, Cristian; Palha, Maria das Dores Correia; Monteiro, Maria Vivina Barros; Coutinho, Leandro Nassar; Kugelmeier, Tatiana; de Castro, Paulo Henrique Gomes

2012-05-01

This study aimed to characterize anatomical and biochemical properties of owl monkey kidneys in order to provide normal reference values. Sixty-nine Aotus azarai infulatus (45 males and 24 females) were divided into four different age groups (AG1: 3 months-1 year; AG2: 2-3 years; AG3: 4-6 years; and AG4: over 7 years old). The monkeys were evaluated with a serum chemistry profile, focusing on serum creatinine (SCr) and blood urea nitrogen (BUN) and with ultrasound. Mean body mass differed among the age groups. This significance was attributed to AG1 body mass being significantly lower than in AG2 and that in both AG2 and AG3 being significantly lower than in the two older age groups (AG3 and AG4). SCr and BUN concentrations differed significantly between the sexes and SCr level correlated positively with age. In contrast, renal measurements did not differ between males and females. Left and right renal volumes did not differ significantly within age groups, or among AG2, AG3, and AG4. Renal volumes in AG1, however, while not differing from those in AG2, did differ significantly from those in AG3 and AG4. In conclusion, this study provides ultrasonographic reference values for the morphology the kidneys in A. a. infulatus. Evidence is also provided that SCr and BUN levels in owl monkeys are influenced by the sex and age of the individual, factors that should be considered when interpreting test results. © 2012 Wiley Periodicals, Inc.

Effect of variation in the glass-former network structure on the relaxation properties of conductive Ag+ ions in AgI-based fast ion conducting glasses

NASA Astrophysics Data System (ADS)

Hanaya, Minoru; Nakayama, Michiko; Hatate, Atsuo; Oguni, Masaharu

1995-08-01

Heat capacities and ac conductivities of AgI-based fast ion conducting glasses of AgI-Ag2O-P2O5 and AgI-Ag2O-B2O3 systems with different P-O or B-O network structures but with the same AgI concentration of 1.55×104 mol m-3 were measured in the temperature range 14-400 K and in the temperature and frequency ranges 100-200 K and 10 Hz-1 MHz, respectively. The β-glass transition due to a freezing-in of the rearrangement of Ag+ ions was observed by adiabatic calorimetry for the glasses in the liquid-nitrogen temperature region, and the conductometry was suggested to see the same mode of Ag+-ion motion as the calorimetry. It was found that the development of the network structure of the glass former at constant AgI concentration resulted in the decrease of the β-glass transition temperature and the activation energy for the diffusional motion of Ag+ ions and in the increase of the heat-capacity jump associated with the glass transition. The results support the amorphous AgI aggregate model for the structure of the conductive region in the glasses with relatively high AgI compositions, indicating that Ag+-ion conductivity is mainly dominated by the degree of development of the AgI aggregate region dependent on the glass-former network structure as well as the AgI composition.

Silver-Loaded Aluminosilicate Aerogels As Iodine Sorbents

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

Riley, Brian J.; Kroll, Jared O.; Peterson, Jacob A.

This paper discusses the development of aluminosilicates aerogels as scaffolds for Ag0 nanoparticles used for chemisorption of I2(g). The starting materials for these scaffolds included both Na-Al-Si-O and Al-Si-O aerogels, both synthesized from metal alkoxides. The Ag0 particles are added by soaking the aerogels in AgNO3 followed by drying and flowing under H2/Ar to reduce Ag+ → Ag0. In some cases, samples were soaked in 3-(mercaptopropyl)trimethoxysilane under supercritical CO2 to add –SH tethers to the aerogel surfaces for more effective binding of Ag+. During the Ag+-impregnation steps, for the Na-Al-Si-O aerogels, Na was replaced with Ag, and for the Al-Si-Omore » aerogel, Si was replaced with Ag. The Ag-loading of thiolated versus non-thiolated Na-Al-Si-O aerogels was comparable at ~35 at% whereas the Ag-loading in unthiolated Al-Si-O aerogels was significantly lower at ~ 7 at% after identical treatment. Iodine loadings in both thiolated and unthiolated Ag0-functionalized Na-Al-Si-O aerogels were > 0.5 g g-1 showing almost complete utilization of the Ag through chemisorption to form AgI. Iodine loading in the thiolated Al-Si-O aerogel was 0.31 g g-1. The control of Ag uptake over solution residence time and [AgNO3] demonstrates the ability to customize the Ag-loading in the base sorbent to regulate the capacity of iodine chemisorption. Consolidation experimental results are also presented.« less

Automated Assume-Guarantee Reasoning for Omega-Regular Systems and Specifications

NASA Technical Reports Server (NTRS)

Chaki, Sagar; Gurfinkel, Arie

2010-01-01

We develop a learning-based automated Assume-Guarantee (AG) reasoning framework for verifying omega-regular properties of concurrent systems. We study the applicability of non-circular (AGNC) and circular (AG-C) AG proof rules in the context of systems with infinite behaviors. In particular, we show that AG-NC is incomplete when assumptions are restricted to strictly infinite behaviors, while AG-C remains complete. We present a general formalization, called LAG, of the learning based automated AG paradigm. We show how existing approaches for automated AG reasoning are special instances of LAG.We develop two learning algorithms for a class of systems, called infinite regular systems, that combine finite and infinite behaviors. We show that for infinity-regular systems, both AG-NC and AG-C are sound and complete. Finally, we show how to instantiate LAG to do automated AG reasoning for infinite regular, and omega-regular, systems using both AG-NC and AG-C as proof rules

Silver behaviour along the salinity gradient of the Gironde Estuary.

PubMed

Lanceleur, Laurent; Schäfer, Jörg; Blanc, Gérard; Coynel, Alexandra; Bossy, Cécile; Baudrimont, Magalie; Glé, Corine; Larrose, Aurélie; Renault, Sophie; Strady, Emilie

2013-03-01

Dissolved and particulate Ag concentrations (Ag(D) and Ag(P), respectively) were measured in surface water and suspended particulate matter (SPM) along the salinity gradient of the Gironde Estuary, South West France, during three cruises (2008-2009) covering contrasting hydrological conditions, i.e. two cruises during intermediate and one during high freshwater discharge (~740 and ~2,300 m(3)/s). Silver distribution reflected non-conservative behaviour with 60-70 % of Ag(P) in freshwater particles being desorbed by chlorocomplexation. The amount of Ag(P) desorbed was similar to the so-called reactive, potentially bioavailable Ag(P) fraction (60 ± 4 %) extracted from river SPM by 1 M HCl. Both Ag(P) (0.22 ± 0.05 mg/kg) and Ag(P)/Th(P) (0.025-0.028) in the residual fraction of fluvial and estuarine SPM were similar to those in SPM from the estuary mouth and in coastal sediments from the shelf off the Gironde Estuary, indicating that chlorocomplexation desorbs the reactive Ag(P). The data show that desorption of reactive Ag(P) mainly occurs inside the estuary during low and intermediate discharge, whereas expulsion of partially Ag(P)-depleted SPM (Ag(P)/Th(P) ~0.040) during the flood implies ongoing desorption in the coastal ocean, e.g. in the nearby oyster production areas (Marennes-Oléron Bay). The highest Ag(D) levels (6-8 ng/L) occurred in the mid-salinity range (15-20) of the Gironde Estuary and were decoupled from freshwater discharge. In the maximum turbidity zone, Ag(D) were at minimum, showing that high SPM concentrations (a) induce Ag(D) adsorption in estuarine freshwater and (b) counterbalance Ag(P) desorption in the low salinity range (1-3). Accordingly, Ag behaviour in turbid estuaries appears to be controlled by the balance between salinity and SPM levels. The first estimates of daily Ag(D) net fluxes for the Gironde Estuary (Boyle's method) showed relatively stable theoretical Ag(D) at zero salinity (Ag (D) (0) = 25-30 ng/L) for the contrasting hydrological situations. Accordingly, Ag(D) net fluxes were very similar for the situations with intermediate discharge (1.7 and 1.6 g/day) and clearly higher during the flood (5.0 g/day) despite incomplete desorption. Applying Ag (D) (0) to the annual freshwater inputs provided an annual net Ag(D) flux (0.64-0.89 t/year in 2008 and 0.56-0.77 t/year in 2009) that was 12-50 times greater than the Ag(D) gross flux. This estimate was consistent with net Ag(D) flux estimates obtained from gross Ag(P) flux considering 60 % desorption in the estuarine salinity gradient.

Learning Rotation-Invariant Local Binary Descriptor.

PubMed

Duan, Yueqi; Lu, Jiwen; Feng, Jianjiang; Zhou, Jie

2017-08-01

In this paper, we propose a rotation-invariant local binary descriptor (RI-LBD) learning method for visual recognition. Compared with hand-crafted local binary descriptors, such as local binary pattern and its variants, which require strong prior knowledge, local binary feature learning methods are more efficient and data-adaptive. Unlike existing learning-based local binary descriptors, such as compact binary face descriptor and simultaneous local binary feature learning and encoding, which are susceptible to rotations, our RI-LBD first categorizes each local patch into a rotational binary pattern (RBP), and then jointly learns the orientation for each pattern and the projection matrix to obtain RI-LBDs. As all the rotation variants of a patch belong to the same RBP, they are rotated into the same orientation and projected into the same binary descriptor. Then, we construct a codebook by a clustering method on the learned binary codes, and obtain a histogram feature for each image as the final representation. In order to exploit higher order statistical information, we extend our RI-LBD to the triple rotation-invariant co-occurrence local binary descriptor (TRICo-LBD) learning method, which learns a triple co-occurrence binary code for each local patch. Extensive experimental results on four different visual recognition tasks, including image patch matching, texture classification, face recognition, and scene classification, show that our RI-LBD and TRICo-LBD outperform most existing local descriptors.

Non-labile silver species in biosolids remain stable throughout ...

EPA Pesticide Factsheets

Increasing commercial use of nanosilver has focussed attention on the fate of silver (Ag) in the wastewater release pathway. This paper reports the speciation and lability of Ag in archived, stockpiled, and contemporary biosolids from the UK, USA and Australia, and indicates that biosolids Ag concentrations have decreased significantly over recent decades. XANES revealed the importance of reduced-sulfur binding environments for Ag speciation in materials ranging from freshly produced sludge to biosolids weathered under ambient environmental conditions for more than 50 years. Isotopic dilution with 110mAg showed that Ag was predominantly non-labile in both fresh and aged biosolids (13.7% mean lability), with E-values ranging from 0.3 to 60 mg/kg and 5 mM CaNO3 extractable Ag from 1.2 to 609 µg/kg (0.002 - 3.4% of the total Ag). This study indicates that at the time of soil application, biosolids Ag will be predominantly Ag-sulfides and characterised by low isotopic lability. This paper presents an overview of biosolids Ag chemistry in historic and contemporary biosolids sourced from the UK, USA and Australia from the 1950s until today by drawing on a unique collection of archived, stockpiled and contemporary biosolids samples. Characteristics of biosolids Ag chemistry determined in this study included total Ag measurement by neutron activation analysis (NAA); the assessment of Ag lability by 110mAg isotopic dilution (E-values); and Ag speciation by X-ray Absorp

Templated-synthesis of hierarchical Ag-AgBr hollow cubes with enhanced visible-light-responsive photocatalytic activity

NASA Astrophysics Data System (ADS)

Kong, Chuncai; Ma, Bo; Liu, Ke; Pu, Fangzhao; Yang, Zhimao; Yang, Sen

2018-06-01

A facile Cu2O-templated approach is demonstrated for the synthesis of hierarchical Ag-AgBr hollow nanucubes. The structural and morphological characterizations show that the as-prepared hollow Ag-AgBr nanocubes consist of dense nanotips, which exhibited an excellent photocatalytic activity under visible light due to the strong surface plasmon resonance (SPR) of Ag nanosturctures and the synergistic effect between Ag and AgBr. The photodegradation ability was evaluated by the degradation of the methyl orange (MO) dye under visible-light irradiation, showing that more than 90% of the MO could be decomposed in 20 min.

Characterisation of biosynthesised silver nanoparticles by scanning electrochemical microscopy (SECM) and voltammetry.

PubMed

Battistel, Dario; Baldi, Franco; Gallo, Michele; Faleri, Claudia; Daniele, Salvatore

2015-01-01

Silver nanoparticles (AgNPs) were biosynthesised by a Klebsiella oxytoca strain BAS-10, which, during its growth, is known to produce a branched exopolysaccharide (EPS). Klebsiella oxytoca cultures, treated with AgNO3 and grown under either aerobic or anaerobic conditions, produced silver nanoparticles embedded in EPS (AgNPs-EPS) containing different amounts of Ag(0) and Ag(I) forms. The average size of the AgNPs-EPS was determined by transmission electron microscopy, while the relative abundance of Ag(0)- or Ag(I)-containing AgNPs-EPS was established by scanning electrochemical microscopy (SECM). Moreover, the release of silver(I) species from the various types of AgNPs-EPS was investigated by combining SECM with anodic stripping voltammetry. These measurements allowed obtaining information on the kinetic of silver ions release from AgNPs-EPS and their concentration profiles at the substrate/water interface. Copyright © 2014 Elsevier B.V. All rights reserved.

Enhancing the ag precipitation by surface mechanical attrition treatment on Cu-Ag alloys

NASA Astrophysics Data System (ADS)

Liu, Jiabin; Zhang, Lehao; Liu, Jingjing; Huang, Liuyi; Gu, Hao; Fang, Youtong; Meng, Liang; Zhang, Jian

2016-09-01

The influence of surface mechanical attrition treatment (SMAT) on Ag precipitation in Cu-Ag alloys was investigated. Cu-6 wt% Ag was melt, cold rolled and solution treated to be Cu-Ag solid solution, which was either aged at 250 and 350 °C for 24 h directly or SMAT-ed before aging. Ag precipitates were hard be found in the directly aged Cu-Ag sample while they were observed clearly in the SMAT-ed counterpart at 250 °C. The Ag precipitates formed in the surface layer by SMAT are much coarser than those in the un-SMAT-ed sample. It is obvious that the precipitating behavior of Ag was promoted significantly by SMAT approach. A large number of defects were generated by SMAT and they were acting as fast atomic diffusion channels that facilitated the atomic diffusion of Ag.

Binary interaction dominates the evolution of massive stars.

PubMed

Sana, H; de Mink, S E; de Koter, A; Langer, N; Evans, C J; Gieles, M; Gosset, E; Izzard, R G; Le Bouquin, J-B; Schneider, F R N

2012-07-27

The presence of a nearby companion alters the evolution of massive stars in binary systems, leading to phenomena such as stellar mergers, x-ray binaries, and gamma-ray bursts. Unambiguous constraints on the fraction of massive stars affected by binary interaction were lacking. We simultaneously measured all relevant binary characteristics in a sample of Galactic massive O stars and quantified the frequency and nature of binary interactions. More than 70% of all massive stars will exchange mass with a companion, leading to a binary merger in one-third of the cases. These numbers greatly exceed previous estimates and imply that binary interaction dominates the evolution of massive stars, with implications for populations of massive stars and their supernovae.

Performance evaluation of new automated hepatitis B viral markers in the clinical laboratory: two quantitative hepatitis B surface antigen assays and an HBV core-related antigen assay.

PubMed

Park, Yongjung; Hong, Duck Jin; Shin, Saeam; Cho, Yonggeun; Kim, Hyon-Suk

2012-05-01

We evaluated quantitative hepatitis B surface antigen (qHBsAg) assays and a hepatitis B virus (HBV) core-related antigen (HBcrAg) assay. A total of 529 serum samples from patients with hepatitis B were tested. HBsAg levels were determined by using the Elecsys (Roche Diagnostics, Indianapolis, IN) and Architect (Abbott Laboratories, Abbott Park, IL) qHBsAg assays. HBcrAg was measured by using Lumipulse HBcrAg assay (Fujirebio, Tokyo, Japan). Serum aminotransferases and HBV DNA were respectively quantified by using the Hitachi 7600 analyzer (Hitachi High-Technologies, Tokyo, Japan) and the Cobas AmpliPrep/Cobas TaqMan test (Roche). Precision of the qHBsAg and HBcrAg assays was assessed, and linearity of the qHBsAg assays was verified. All assays showed good precision performance with coefficients of variation between 4.5% and 5.3% except for some levels. Both qHBsAg assays showed linearity from 0.1 to 12,000.0 IU/mL and correlated well (r = 0.9934). HBsAg levels correlated with HBV DNA (r = 0.3373) and with HBcrAg (r = 0.5164), and HBcrAg also correlated with HBV DNA (r = 0.5198; P < .0001). This observation could provide impetus for further research to elucidate the clinical usefulness of the qHBsAg and HBcrAg assays.

Both acyl and des-acyl ghrelin regulate adiposity and glucose metabolism via central nervous system ghrelin receptors.

PubMed

Heppner, Kristy M; Piechowski, Carolin L; Müller, Anne; Ottaway, Nickki; Sisley, Stephanie; Smiley, David L; Habegger, Kirk M; Pfluger, Paul T; Dimarchi, Richard; Biebermann, Heike; Tschöp, Matthias H; Sandoval, Darleen A; Perez-Tilve, Diego

2014-01-01

Growth hormone secretagogue receptors (GHSRs) in the central nervous system (CNS) mediate hyperphagia and adiposity induced by acyl ghrelin (AG). Evidence suggests that des-AG (dAG) has biological activity through GHSR-independent mechanisms. We combined in vitro and in vivo approaches to test possible GHSR-mediated biological activity of dAG. Both AG (100 nmol/L) and dAG (100 nmol/L) significantly increased inositol triphosphate formation in human embryonic kidney-293 cells transfected with human GHSR. As expected, intracerebroventricular infusion of AG in mice increased fat mass (FM), in comparison with the saline-infused controls. Intracerebroventricular dAG also increased FM at the highest dose tested (5 nmol/day). Chronic intracerebroventricular infusion of AG or dAG increased glucose-stimulated insulin secretion (GSIS). Subcutaneously infused AG regulated FM and GSIS in comparison with saline-infused control mice, whereas dAG failed to regulate these parameters even with doses that were efficacious when delivered intracerebroventricularly. Furthermore, intracerebroventricular dAG failed to regulate FM and induce hyperinsulinemia in GHSR-deficient (Ghsr(-/-)) mice. In addition, a hyperinsulinemic-euglycemic clamp suggests that intracerebroventricular dAG impairs glucose clearance without affecting endogenous glucose production. Together, these data demonstrate that dAG is an agonist of GHSR and regulates body adiposity and peripheral glucose metabolism through a CNS GHSR-dependent mechanism.

Humoral Immunity Provides Resident Intestinal Eosinophils Access to Luminal Antigen via Eosinophil-Expressed Low-Affinity Fcγ Receptors.

PubMed

Smith, Kalmia M; Rahman, Raiann S; Spencer, Lisa A

2016-11-01

Eosinophils are native to the healthy gastrointestinal tract and are associated with inflammatory diseases likely triggered by exposure to food allergens (e.g., food allergies and eosinophilic gastrointestinal disorders). In models of allergic respiratory diseases and in vitro studies, direct Ag engagement elicits eosinophil effector functions, including degranulation and Ag presentation. However, it was not known whether intestinal tissue eosinophils that are separated from luminal food Ags by a columnar epithelium might similarly engage food Ags. Using an intestinal ligated loop model in mice, in this study we determined that resident intestinal eosinophils acquire Ag from the lumen of Ag-sensitized but not naive mice in vivo. Ag acquisition was Ig-dependent; intestinal eosinophils were unable to acquire Ag in sensitized Ig-deficient mice, and passive immunization with immune serum or Ag-specific IgG was sufficient to enable intestinal eosinophils in otherwise naive mice to acquire Ag in vivo. Intestinal eosinophils expressed low-affinity IgG receptors, and the activating receptor FcγRIII was necessary for Ig-mediated acquisition of Ags by isolated intestinal eosinophils in vitro. Our combined data suggest that intestinal eosinophils acquire lumen-derived food Ags in sensitized mice via FcγRIII Ag focusing and that they may therefore participate in Ag-driven secondary immune responses to oral Ags. Copyright © 2016 by The American Association of Immunologists, Inc.

Oral vaccination with salmonella simultaneously expressing Yersinia pestis F1 and V antigens protects against bubonic and pneumonic plague.

PubMed

Yang, Xinghong; Hinnebusch, B Joseph; Trunkle, Theresa; Bosio, Catharine M; Suo, Zhiyong; Tighe, Mike; Harmsen, Ann; Becker, Todd; Crist, Kathryn; Walters, Nancy; Avci, Recep; Pascual, David W

2007-01-15

The gut provides a large area for immunization enabling the development of mucosal and systemic Ab responses. To test whether the protective Ags to Yersinia pestis can be orally delivered, the Y. pestis caf1 operon, encoding the F1-Ag and virulence Ag (V-Ag) were cloned into attenuated Salmonella vaccine vectors. F1-Ag expression was controlled under a promoter from the caf1 operon; two different promoters (P), PtetA in pV3, PphoP in pV4, as well as a chimera of the two in pV55 were tested. F1-Ag was amply expressed; the chimera in the pV55 showed the best V-Ag expression. Oral immunization with Salmonella-F1 elicited elevated secretory (S)-IgA and serum IgG titers, and Salmonella-V-Ag(pV55) elicited much greater S-IgA and serum IgG Ab titers than Salmonella-V-Ag(pV3) or Salmonella-V-Ag(pV4). Hence, a new Salmonella vaccine, Salmonella-(F1+V)Ags, made with a single plasmid containing the caf1 operon and the chimeric promoter for V-Ag allowed the simultaneous expression of F1 capsule and V-Ag. Salmonella-(F1+V)Ags elicited elevated Ab titers similar to their monotypic derivatives. For bubonic plague, mice dosed with Salmonella-(F1+V)Ags and Salmonella-F1-Ag showed similar efficacy (>83% survival) against approximately 1000 LD(50) Y. pestis. For pneumonic plague, immunized mice required immunity to both F1- and V-Ags because the mice vaccinated with Salmonella-(F1+V)Ags protected against 100 LD(50) Y. pestis. These results show that a single Salmonella vaccine can deliver both F1- and V-Ags to effect both systemic and mucosal immune protection against Y. pestis.

Learning to assign binary weights to binary descriptor

NASA Astrophysics Data System (ADS)

Huang, Zhoudi; Wei, Zhenzhong; Zhang, Guangjun

2016-10-01

Constructing robust binary local feature descriptors are receiving increasing interest due to their binary nature, which can enable fast processing while requiring significantly less memory than their floating-point competitors. To bridge the performance gap between the binary and floating-point descriptors without increasing the computational cost of computing and matching, optimal binary weights are learning to assign to binary descriptor for considering each bit might contribute differently to the distinctiveness and robustness. Technically, a large-scale regularized optimization method is applied to learn float weights for each bit of the binary descriptor. Furthermore, binary approximation for the float weights is performed by utilizing an efficient alternatively greedy strategy, which can significantly improve the discriminative power while preserve fast matching advantage. Extensive experimental results on two challenging datasets (Brown dataset and Oxford dataset) demonstrate the effectiveness and efficiency of the proposed method.

Primordial main equence binary stars in the globular cluster M71

NASA Technical Reports Server (NTRS)

Yan, Lin; Mateo, Mario

1994-01-01

We report the identification of five short-period variables near the center of the metal-rich globular cluster M71. Our observations consist of multiepoch VI charge coupled device (CCD) images centered on the cluster and covering a 6.3 min x 6.3 min field. Four of these variables are contact eclipsing binaries with periods between 0.35 and 0.41 days; one is a detached or semidetached eclipsing binary with a period of 0.56 days. Two of the variables were first identified as possible eclipsing binaries in an earlier survey by Hodder et al. (1992). We have used a variety of arguments to conclude that all five binary stars are probable members of M71, a result that is consistent with the low number (0.15) of short-period field binaries expected along this line of sight. Based on a simple model of how contact binaries evolve from initially detached binaries, we have determined a lower limit of 1.3% on the frequency of primordial binaries in M71 with initial orbital periods in the range 2.5 - 5 days. This implies that the overall primordial binary frequency, f, is 22(sup +26)(sub -12)% assuming df/d log P = const ( the 'flat' distribution), or f = 57(sup +15)(sub -8)% for df/d log P = 0.032 log P + const as observed for G-dwarf binaries in the solar neighborhood (the 'sloped' distribution). Both estimates of f correspond to binaries with initial periods shorter than 800 yr since any longer-period binaries would have been disrupted over the lifetime of the cluster. Our short-period binary frequency is in excellent agreement with the observed frequency of red-giant binaries observed in globulars if we adopt the flat distribution. For the sloped distribution, our results significantly overestimate the number of red-giant binaries. All of the short-period M71 binaries lie within 1 mag of the luminosity of the cluster turnoff in the color-magnitude diagram despite the fact we should have easily detected similar eclipsing binaries 2 - 2.5 mag fainter than this. We discuss the implications of this on our estimates of the binary frequency in M71 and on the formation of blue stragglers.

Phase Equilibria and Thermodynamic Descriptions of Ag-Ge and Ag-Ge-Ni Systems

NASA Astrophysics Data System (ADS)

Rajkumar, V. B.; Chen, Sinn-Wen

2018-07-01

Gibbs energy modeling of Ag-Ge and Ag-Ge-Ni systems was done using the calculation of the phase diagram method with associated data from this work and relevant literature information. In the Ag-Ge system, the solidus temperatures of Ag-rich alloys are measured using differential thermal analysis, and the energy of mixing for the FCC_A1 phase is calculated using the special quasi-random structures technique. The isothermal sections of the Ag-Ge-Ni system at 1023 K and 673 K are also experimentally determined. These data and findings in the relevant literature are used to model the Gibbs energy of the Ag-Ge and Ag-Ge- Ni systems. A reaction scheme and a liquidus projection of the Ag-Ge-Ni system are determined.

Dependence of Ag/Ga composition ratio in AgGaSe2 thin film

NASA Astrophysics Data System (ADS)

Matsuo, H.; Yoshino, K.; Ikari, T.

2006-09-01

AgGaSe2 thin film was deposited on glass substrates by vacuum evaporation method. The starting material was mixed Ag2Se and Ga2Se3 powders. Ag/Ga ratios of the samples were 1.5, 1.2, 1.0, 0.8, 0.7 and 0.4. The samples were annealed from 100 to 600 °C for 10 min. After these processes, single phase AgGaSe2 thin films could be obtained except Ag/Ga ratio of 0.4 at annealing temperature of 600 °C. Ag-rich samples had large grain. On the other hand, Ga-rich samples had small grain. Furthermore, Ga-rich and Ag-rich samples indicated p- and n-types because of Ag- and/or Ga-vacancy and Se-vacancy, respectively.

Preparation of silver nanoparticles fabrics against multidrug-resistant bacteria

NASA Astrophysics Data System (ADS)

Hanh, Truong Thi; Thu, Nguyen Thi; Hien, Nguyen Quoc; An, Pham Ngoc; Loan, Truong Thi Kieu; Hoa, Phan Thi

2016-04-01

The silver nanoparticles (AgNPs)/peco fabrics were prepared by immobilization of AgNPs on fabrics in which AgNPs were synthesized by γ-irradiation of the 10 mM AgNO3 chitosan solution at the dose of 17.6 kGy. The AgNPs size has been estimated to be about 11 nm from TEM image. The AgNPs content onto peco fabrics was of 143±6 mg/kg at the initial AgNPs concentration of 100 ppm. The AgNPs colloidal solution was characterized by UV-vis spectroscopy and TEM image. The antibacterial activity of AgNPs/peco fabrics after 60 washings against Staphylococcus aureus and Klebsiella pneumoniae was found to be over 99%. Effects of AgNPs fabics on multidrug-resistant pathogens from the clinical specimens were also tested.

Reversible emission evolution from Ag activated zeolite Na-A upon dehydration/hydration

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

Lin, Hui, E-mail: linh8112@163.com, E-mail: fujii@eedept.kobe-u.ac.jp; Imakita, Kenji; Fujii, Minoru, E-mail: linh8112@163.com, E-mail: fujii@eedept.kobe-u.ac.jp

2014-11-24

Reversible emission evolution of thermally treated Ag activated zeolite Na-A upon dehydration/hydration in vacuum/water vapor was observed. The phenomenon was observed even for the sample with low Ag{sup +}-Na{sup +} exchanging (8.3%), indicating that the emission from Ag activated zeolites may not come from Ag clusters while from the surrounding coordinated Ag{sup +} ions or Ag{sup 0} atoms. It was disclosed that the characteristic yellow-green emission at ∼560 ± 15 nm is strongly associated with the coordinating water molecules to the Ag{sup +} ions or Ag{sup 0} atoms, which is clear evidence for that the efficient emission from Ag activated zeolites may notmore » originate from the quantum confinement effect.« less

HBsAg quantification to predict natural history and treatment outcome in chronic hepatitis B patients.

PubMed

Martinot-Peignoux, Michelle; Asselah, Tarik; Marcellin, Patrick

2013-08-01

There is a growing interest in serum HBsAg quantification (qHbsAg). HBsAg titers are negatively correlated with liver fibrosis in HBeAg(+) patients. In HBeAg(-) HBsAg level <1000 IU/ml and HBV-DNA titer <2000 IU/ml accurately identify inactive carriers. During PEG-IFN treatment qHBsAg identifies patients with no benefit from therapy at week 12, allowing stopping or switched- "week 12 stopping rule". During nucleos(t)ide analogues the role of qHBsAg need to be clarified. In clinical practice qHBsAg is a simple and reproducible tool that may be used in association with HBV-DNA to classify patients during the natural history of HBV and to monitor therapy. Copyright © 2013 Elsevier Inc. All rights reserved.

Effects of Bi Addition on the Microstructure and Mechanical Properties of Nanocrystalline Ag Coatings.

PubMed

Wang, Yuxin; Cheng, Guang; Tay, See Leng; Guo, Yunxia; Sun, Xin; Gao, Wei

2017-08-10

In this study we investigated the effects of Bi addition on the microstructure and mechanical properties of an electrodeposited nanocrystalline Ag coating. Microstructural features were investigated with transmission electron microscopy (TEM). The results indicate that the addition of Bi introduced nanometer-scale Ag-Bi solid solution particles and more internal defects to the initial Ag microstructures. The anisotropic elastic-plastic properties of the Ag nanocrystalline coating with and without Bi addition were examined with nanoindentation experiments in conjunction with the recently-developed inverse method. The results indicate that the as-deposited nanocrystalline Ag coating contained high mechanical anisotropy. With the addition of 1 atomic percent (at%) Bi, the anisotropy within Ag-Bi coating was very small, and yield strength of the nanocrystalline Ag-Bi alloy in both longitudinal and transverse directions were improved by over 100% compared to that of Ag. On the other hand, the strain-hardening exponent of Ag-Bi was reduced to 0.055 from the original 0.16 of the Ag coating. Furthermore, the addition of Bi only slightly increased the electrical resistivity of the Ag-Bi coating in comparison to Ag. Results of our study indicate that Bi addition is a promising method for improving the mechanical and physical performances of Ag coating for electrical contacts.

Nafion-coating of the electrodes improves the flow-stability of the Ag/SiO2/Ag2O electroosmotic pump.

PubMed

Shin, Woonsup; Zhu, Enhua; Nagarale, Rajaram Krishna; Kim, Chang Hwan; Lee, Jong Myung; Shin, Samuel Jaeho; Heller, Adam

2011-06-15

When a current or a voltage is applied across the ceramic membrane of the nongassing Ag/Ag(2)O-SiO(2)-Ag/Ag(2)O pump, protons produced in the anodic reaction 2Ag(s) + H(2)O → Ag(2)O(s) + 2H(+) + 2e(-) are driven to the cathode, where they are consumed by the reaction Ag(2)O(s) + H(2)O + 2e(-) → 2Ag(s) + 2 OH(-). The flow of water is induced by momentum transfer from the electric field-driven proton-sheet at the surface of the ceramic membrane. About 10(4) water molecules flowed per reacted electron. Because dissolved ions decrease the field at the membrane surface, the flow decreases upon increasing the ionic strength. For this reason Ag(+) ions introduced through the anodic reaction and by dissolution of Ag(2)O decrease the flow. Their accumulation is reduced by applying Nafion-films to the electrodes. The 20 μL min(-1) flow rate of 6 mm i.d. pumps with Nafion coated electrodes operate daily for 5 min at 1 V for 1 month, for 70 h when the pump is pulsed for 30 s every 30 min, and for 2 h when operating continuously.

Short-term soil bioassays may not reveal the full toxicity potential for nanomaterials; bioavailability and toxicity of silver ions (AgNO₃) and silver nanoparticles to earthworm Eisenia fetida in long-term aged soils.

PubMed

Diez-Ortiz, Maria; Lahive, Elma; George, Suzanne; Ter Schure, Anneke; Van Gestel, Cornelis A M; Jurkschat, Kerstin; Svendsen, Claus; Spurgeon, David J

2015-08-01

This study investigated if standard risk assessment hazard tests are long enough to adequately provide the worst case exposure for nanomaterials. This study therefore determined the comparative effects of the aging on the bioavailability and toxicity to earthworms of soils dosed with silver ions and silver nanoparticles (Ag NP) for 1, 9, 30 & 52 weeks, and related this to the total Ag in the soil, Ag in soil pore water and earthworm tissue Ag concentrations. For ionic Ag, a classical pattern of reduced bioavailability and toxicity with time aged in the soil was observed. For the Ag NP, toxicity increased with time apparently driven by Ag ion dissolution from the added Ag NPs. Internal Ag in the earthworms did not always explain toxicity and suggested the presence of an internalised, low-toxicity Ag fraction (as intact or transformed NPs) after shorter aging times. Our results indicate that short-term exposures, without long-term soil aging, are not able to properly assess the environmental risk of Ag NPs and that ultimately, with aging time, Ag ion and Ag NP effect will merge to a common value. Copyright © 2015 Elsevier Ltd. All rights reserved.

Phytotoxicity, accumulation and transport of silver nanoparticles by Arabidopsis thaliana.

PubMed

Geisler-Lee, Jane; Wang, Qiang; Yao, Ying; Zhang, Wen; Geisler, Matt; Li, Kungang; Huang, Ying; Chen, Yongsheng; Kolmakov, Andrei; Ma, Xingmao

2013-05-01

The widespread availability of nano-enabled products in the global market may lead to the release of a substantial amount of engineered nanoparticles in the environment, which frequently display drastically different physiochemical properties than their bulk counterparts. The purpose of the study was to evaluate the impact of citrate-stabilised silver nanoparticles (AgNPs) on the plant Arabidopsis thaliana at three levels, physiological phytotoxicity, cellular accumulation and subcellular transport of AgNPs. The monodisperse AgNPs of three different sizes (20, 40 and 80 nm) aggregated into much larger sizes after mixing with quarter-strength Hoagland solution and became polydisperse. Immersion in AgNP suspension inhibited seedling root elongation and demonstrated a linear dose-response relationship within the tested concentration range. The phytotoxic effect of AgNPs could not be fully explained by the released silver ions. Plants exposed to AgNP suspensions bioaccumulated higher silver content than plants exposed to AgNO3 solutions (Ag(+) representative), indicating AgNP uptake by plants. AgNP toxicity was size and concentration dependent. AgNPs accumulated progressively in this sequence: border cells, root cap, columella and columella initials. AgNPs were apoplastically transported in the cell wall and found aggregated at plasmodesmata. In all the three levels studied, AgNP impacts differed from equivalent dosages of AgNO3.

Template-free synthesis of cube-like Ag/AgCl nanostructures via a direct-precipitation protocol: highly efficient sunlight-driven plasmonic photocatalysts.

PubMed

Zhu, Mingshan; Chen, Penglei; Ma, Wanhong; Lei, Bin; Liu, Minghua

2012-11-01

In this paper, we report that cube-like Ag/AgCl nanostructures could be facilely fabricated in a one-pot manner through a direct-precipitation protocol under ambient conditions, wherein no additional issues such as external energy (e.g., high temperature or high pressure), surfactants, or reducing agents are required. In terms of using sodium chloride (NaCl) as chlorine source and silver acetate (CH₃COOAg) as silver source, it is disclosed that simply by adding an aqueous solution of NaCl into an aqueous solution of CH₃COOAg, Ag/AgCl nanostructures with a cube-like geometry, could be successfully formulated. We show that thus-formulated cube-like Ag/AgCl nanospecies could be used as high-performance yet durable visible-light-driven or sunlight-driven plasmonic photocatalysts for the photodegradation of methyl orange (MO) and 4-chlorophenol (4-CP) pollutants. Compared with the commercially available P25-TiO₂, and the Ag/AgCl nanospheres previously fabricated via a surfactant-assisted method, our current cube-like Ag/AgCl nanostructures could exhibit much higher photocatalytic performance. Our template free protocol might open up new and varied opportunities for an easy synthesis of cube-like Ag/AgCl-based high-performance sunlight-driven plasmonic photocatalysts for organic pollutant elimination.

Isomorphism and solid solutions among Ag- and Au-selenides

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

Palyanova, Galina A.; Seryotkin, Yurii V.; Novosibirsk State University

Au-Ag selenides were synthesized by heating stoichiometric mixtures of elementary substances of initial compositions Ag{sub 2−x}Au{sub x}Se with a step of x=0.25 (0≤x≤2) to 1050 °C and annealing at 500 °C. Scanning electron microscopy, optical microscopy, electron microprobe analysis and X-ray powder diffraction methods have been applied to study synthesized samples. Results of studies of synthesized products revealed the existence of three solid solutions with limited isomorphism Ag↔Au: naumannite Ag{sub 2}Se – Ag{sub 1.94}Au{sub 0.06}Se, fischesserite Ag{sub 3}AuSe{sub 2} - Ag{sub 3.2}Au{sub 0.8}Se{sub 2} and gold selenide AuSe - Au{sub 0.94}Ag{sub 0.06}Se. Solid solutions and AgAuSe phases were added tomore » the phase diagram of Ag-Au-Se system. Crystal-chemical interpretation of Ag-Au isomorphism in selenides was made on the basis of structural features of fischesserite, naumannite, and AuSe. - Highlights: • Au-Ag selenides were synthesized. • Limited Ag-Au isomorphism in the selenides is affected by structural features. • Some new phases were introduced to the phase diagram Ag-Au-Se.« less

Interaction between Silver Nanoparticles and Spinach Leaf

NASA Astrophysics Data System (ADS)

Tian, Y.; Li, H.; Zhang, Y.; Riser, E.; He, S.; Zhang, W.

2013-12-01

Interactions of engineered nanoparticles (ENPs) with plant surfaces are critical to assessing the bioavailability of ENPs to edible plants and to further evaluating impacts of ENPs on ecological health and food safety. Silver nanoparticles (i.e., nanoAg) could enter the agroecosystems either as an active ingredient in pesticides or from other industrial and consumer applications. Thus, in the events of pesticide application, rainfall, and irrigation, vegetable leaves could become in contact and then interact with nanoAg. The present study was to assess whether the interaction of nanoAg with spinach leaves can be described by classical sorption models and to what extent it depends on and varies with dispersion methods, environmental temperature, and ion release. We investigated the stability and ion release of nanoAg dispersed by sodium dodecyl sulfate (SDS, 1%) and humic acid (HA, 10 mg C/L) solutions, as well as sorption and desorption of nanoAg on and from the fresh spinach leaf. Results showed SDS-nanoAg released about 2%-8% more Ag ion than HA-nanoAg. The sorption of Ag ion, described by the Freundlich model in the initial concentration range of 0.6-50 mg/L, was 2-4 times higher than that of nanoAg. The sorption of nanoAg on spinach leaf can be fitted by the Langmuir model, and the maximum sorption amount of HA-nanoAg and SDS-nanoAg was 0.21 and 0.41 mg/g, respectively. The higher sorption of SDS-nanoAg relative to that of HA-nanoAg could be partially resulted from the higher release of Ag ion from the former. The maximum desorption amount of HA-nanoAg and SDS-nanoAg in 1% SDS solution was 0.08 and 0.10 mg/g, respectively. NanoAg attachment on and its penetration to the spinach leaf was visualized by the Scanning Electron Microscope equipped with an Energy Dispersive Spectrometer (SEM-EDS). It is equally important that the less sorption of nanoAg under low environmental temperature could be partially due to the closure of stomata, as verified by SEM-EDS. CytoViva Hyperspectral Imaging System was also employed to map the distribution of nanoAg in the leaf profile. Significant sorption of nanoAg on spinach leaf should urge the precaution with potential widespread use of ENPs in agriculture.

COSMIC probes into compact binary formation and evolution

NASA Astrophysics Data System (ADS)

Breivik, Katelyn

2018-01-01

The population of compact binaries in the galaxy represents the final state of all binaries that have lived up to the present epoch. Compact binaries present a unique opportunity to probe binary evolution since many of the interactions binaries experience can be imprinted on the compact binary population. By combining binary evolution simulations with catalogs of observable compact binary systems, we can distill the dominant physical processes that govern binary star evolution, as well as predict the abundance and variety of their end products.The next decades herald a previously unseen opportunity to study compact binaries. Multi-messenger observations from telescopes across all wavelengths and gravitational-wave observatories spanning several decades of frequency will give an unprecedented view into the structure of these systems and the composition of their components. Observations will not always be coincident and in some cases may be separated by several years, providing an avenue for simulations to better constrain binary evolution models in preparation for future observations.I will present the results of three population synthesis studies of compact binary populations carried out with the Compact Object Synthesis and Monte Carlo Investigation Code (COSMIC). I will first show how binary-black-hole formation channels can be understood with LISA observations. I will then show how the population of double white dwarfs observed with LISA and Gaia could provide a detailed view of mass transfer and accretion. Finally, I will show that Gaia could discover thousands black holes in the Milky Way through astrometric observations, yielding view into black-hole astrophysics that is complementary to and independent from both X-ray and gravitational-wave astronomy.

Inhalable Andrographolide-β-cyclodextrin Inclusion Complexes for Treatment of Staphylococcus aureus Pneumonia by Regulating Immune Responses.

PubMed

Zhang, Tongtong; Zhu, Lifei; Li, Miao; Hu, Yuzhen; Zhang, Erfeng; Jiang, Qingcheng; Han, Guang; Jin, Yiguang

2017-05-01

Bacterial pneumonia is a serious disease with high mortality if no appropriate and immediate therapy is available. Andrographolide (AG) is an anti-inflammatory agent extracted from a traditional Chinese herb andrographis paniculata. Oral AG tablets and pills are clinically applied for treatment of upper respiratory tract infections. However, the low solubility and bioavailability of AG lead to high doses and long-term therapy. Here we developed an andrographolide-β-cyclodextrin inclusion complex (AG-β-CD) for inhalation therapy of Staphylococcus aureus pneumonia. AG-β-CD was identified with X-ray diffraction and FT-IR. Surprisingly, both AG-β-CD and AG showed little in vitro anti-S. aureus activity. However, pulmonary delivery of AG, AG-β-CD, or penicillin had significant anti-S. aureus pneumonia effects. Leukocytes, neutrophils, white blood cells, total proteins, TNF-α, IL-6, NF-κB p65 expression, and bacterial colonies in the bronchoalveolar lavage fluids were detected. Pulmonary delivery of AG and AG-β-CD led to bacterial inhibition and inflammation alleviation by regulating immune responses, while penicillin only killed bacteria without significant immune regulation. Moreover, the antipneumonia activity of AG-β-CD was much higher than that of AG, probably resulting from locally accelerated AG dissolution due to β-CD inclusion. The aerodynamic diameter of AG-β-CD powders was 2.03 μm, suitable for pulmonary delivery. Inhalable AG-β-CD is a promising antibacterial and anti-inflammatory medicine for the treatment of S. aureus pneumonia by regulating immune responses, and the effect is enhanced by β-CD inclusion. AG and its formulations might be potent weapons against the resistant bacterial pneumonia due to their specific mechanism in the future.

Determination of the anastomosis grouping and virulence of Rhizoctonia spp. associated with potato tubers grown in Lincoln, New Zealand.

PubMed

Farrokhi-Nejad, Reza; Cromey, Matthew G; Moosawi-Jorf, S Ali

2007-11-01

A total of 58 isolates of Rhizoctonia spp. (46 R. solani and 12 binucleate Rhizoctonia) were recovered from potato tubers showing black scurf disease symptom during the 2004 growing season in Lincoln, New Zealand. The isolates were assigned to 5 Anastomosis Groups (AG) ofR. solani AG-3 (54.34%), AG-5 (28.26%), AG-8 (8.69%), AG-4 (6.52%) and AG-2-2 IIIB (2.17%) and six anastomosis groups ofbinucleate Rhizoctonia, AG-K (25%), AG-Bi (25%), AG-Ba (8.33%), AG-C (8.33%), AG-D (8.33%) and AG-E (8.33%). Two isolates of BNR did not anastomose with any of the tester strains and remain unidentified. In pathogenicity tests that were carried out on radish, carrot, lettuce, onion, tomato and hemp, it was found that all the isolates of both R. solani and binucleate Rhizoctonia to be virulent at varying degrees to these 6 plants species from different families. In these tests, isolates of AG-3 and AG-8 from R. solani population caused the highest and lowest disease severity on all 6 plant species, respectively. In population of binucleate Rhizoctonia, on the other hand, the highest and lowest disease severities were caused by the isolates of AG-D and AG-Ba on all test plants, respectively. When the results of the pathogenicity tests were examined in terms of the susceptibility levels of the plants, the most resistant plant was tomato against different AGs of R. solani and BNR. On the other hand, radish was the most susceptible plant species tested in this study against both R. solani and BNR isolates.

Electrodes for high-definition transcutaneous DC stimulation for applications in drug delivery and electrotherapy, including tDCS.

PubMed

Minhas, Preet; Bansal, Varun; Patel, Jinal; Ho, Johnson S; Diaz, Julian; Datta, Abhishek; Bikson, Marom

2010-07-15

Transcutaneous electrical stimulation is applied in a range of biomedical applications including transcranial direct current stimulation (tDCS). tDCS is a non-invasive procedure where a weak direct current (<2 mA) is applied across the scalp to modulate brain function. High-definition tDCS (HD-tDCS) is a technique used to increase the spatial focality of tDCS by passing current across the scalp using <12 mm diameter electrodes. The purpose of this study was to design and optimize "high-definition" electrode-gel parameters for electrode durability, skin safety and subjective pain. Anode and cathode electrode potential, temperature, pH and subjective sensation over time were assessed during application of 2 mA direct current, for up to 22 min on agar gel or subject forearms. A selection of five types of solid-conductors (Ag pellet, Ag/AgCl pellet, rubber pellet, Ag/AgCl ring and Ag/AgCl disc) and seven conductive gels (Signa, Spectra, Tensive, Redux, BioGel, Lectron and CCNY-4) were investigated. The Ag/AgCl ring in combination with CCNY-4 gel resulted in the most favorable outcomes. Under anode stimulations, electrode potential and temperature rises were generally observed in all electrode-gel combinations except for Ag/AgCl ring and disc electrodes. pH remained constant for all solid-conductors except for both Ag and rubber pellet electrodes with Signa and CCNY-4 gels. Sensation ratings were independent of stimulation polarity. Ag/AgCl ring electrodes were found to be the most comfortable followed by Ag, rubber and Ag/AgCl pellet electrodes across all gels. Copyright 2010 Elsevier B.V. All rights reserved.

Role of Secondary Particle Formation in the Persistence of Silver Nanoparticles in Humic Acid Containing Water under Light Irradiation.

PubMed

Zhang, Tuoya; Lu, Dawei; Zeng, Lixi; Yin, Yongguang; He, Yujian; Liu, Qian; Jiang, Guibin

2017-12-19

The wide use of silver nanoparticles (AgNPs) leads to the increasing release of AgNPs into the environment. Dissolved organic matter (DOM) is a key factor affecting the behaviors and fate of AgNPs in the aquatic environment. However, the mechanisms for the DOM-mediated transformations of AgNPs are still not fully understood. In this study, we investigated the persistence of AgNPs in the aquatic environment in the presence of different concentrations of humic acid (HA) over periods of time up to 14 days. The Ag species were monitored and characterized by absorption spectrometry, transmission electron microscopy (TEM), inductively coupled plasma mass spectrometry (ICP-MS), and multicollector ICP-MS (MC-ICP-MS). Results showed that the long-term persistence of AgNPs in HA-containing water was determined by two critical concentrations of HA. When the HA concentration exceeded a lower critical value, AgNPs could be persistent in the solution, and a large number of AgNPs were formed secondarily from the HA-induced reduction of the Ag + ions released from the primary AgNPs, causing a redistribution of the particle size. With the HA concentration above a higher critical value, AgNPs could persist in the solution without a significant change in particle size. Notably, we used Ag isotope fractionation to investigate the transformation mechanism of AgNPs. The natural isotopic analysis by MC-ICP-MS revealed that the size redistribution of AgNPs caused significant Ag isotope fractionation, which gave additional evidence for the proposed mechanisms. This study provides new insights into the environmental fate of engineered AgNPs and highlights the usefulness of stable isotope fractionation in environmental nanotechnology.

Electrodes for high-definition transcutaneous DC stimulation for applications in drug-delivery and electrotherapy, including tDCS

PubMed Central

Minhas, Preet; Bansal, Varun; Patel, Jinal; Ho, Johnson S.; Diaz, Julian; Datta, Abhishek; Bikson, Marom

2010-01-01

Transcutaneous electrical stimulation is applied in a range of biomedical applications including Transcranial Direct Current Stimulation (tDCS). tDCS is a non-invasive procedure where a weak direct current (<2 mA) is applied across the scalp to modulate brain function. High-Definition tDCS (HD-tDCS) is a technique used to increase the spatial focality of tDCS by passing current across the scalp using <12 mm diameter electrodes. The purpose of this study was to design and optimize “high-definition” electrode-gel parameters for electrode durability, skin safety, and subjective pain. Anode and cathode electrode potential, temperature, pH, and subjective sensation over time were assessed during application of 2 mA direct current, for up to 22 minutes on agar gel or subject forearms. A selection of 5 types of solid-conductors (Ag pellet, Ag/AgCl pellet, Rubber pellet, Ag/AgCl ring, and Ag/AgCl disc) and 7 conductive gels (Signa, Spectra, Tensive, Redux, BioGel, Lectron, and CCNY-4) were investigated. The Ag/AgCl ring in combination with CCNY-4 gel resulted in the most favorable outcomes. Under anode stimulations, electrode potential and temperature rises were generally observed in all electrode-gel combinations except for Ag/AgCl ring and disc electrodes. pH remained constant for all solid-conductors except for both Ag and Rubber pellet electrodes with Signa and CCNY-4 gels. Sensation ratings were independent of stimulation polarity. Ag/AgCl ring electrodes were found to be the most comfortable followed by Ag, Rubber, and Ag/AgCl pellet electrodes across all gels. PMID:20488204

Using nuclear microscopy to characterize the interaction of textile-used silver nanoparticles with a biological wastewater treatment system

NASA Astrophysics Data System (ADS)

Bento, J. B.; Franca, R. D. G.; Pinheiro, T.; Alves, L. C.; Pinheiro, H. M.; Lourenço, N. D.

2017-08-01

The use of engineered nanoparticles in the textile industry has been rapidly increasing but their fate during biological wastewater treatment is largely unknown. The goal of the current study was to characterize the interaction of silver nanoparticles (AgNPs), used in the textile industry, with a biological wastewater treatment system based on aerobic granular sludge (AGS). The exposure tests were performed using a laboratory-scale sequencing batch reactor (SBR) system with AGS. The behavior and fate of textile AgNPs in the AGS system was studied with nuclear microscopy techniques. Elemental maps of AGS samples collected from the SBR showed that AgNPs typically clustered in agglomerates of small dimensions (<10 μm), which were preferentially associated with extracellular polymeric substances (EPS). This preliminary study highlights the potential application of nuclear microscopy for the characterization of the behavior and fate of AgNPs in AGS. The detailed compartmentalization of AgNPs in AGS components obtained with nuclear microscopy provides new and relevant information concerning AgNPs retention. This will be important in biotechnological terms to delineate strategies for AgNPs removal from textile wastewater.

Synthesis of silver nanoparticles by solar irradiation of cell-free Bacillus amyloliquefaciens extracts and AgNO3.

PubMed

Wei, Xuetuan; Luo, Mingfang; Li, Wei; Yang, Liangrong; Liang, Xiangfeng; Xu, Lin; Kong, Peng; Liu, Huizhou

2012-01-01

Silver nanoparticles (AgNPs) were obtained by solar irradiation of cell-free extracts of Bacillusamyloliquefaciens and AgNO3. Light intensity, extract concentration, and NaCl addition influenced the synthesis of AgNPs. Under optimized conditions (solar intensity 70,000 lx, extract concentration 3 mg/mL, and NaCl content 2 mM), 98.23±0.06% of the Ag+ (1 mM) was reduced to AgNPs within 80 min, and the ζ-potential of AgNPs reached -70.84±0.66 mV. TEM (Transmission electron microscopy) and XRD (X-ray diffraction) analysis confirmed that circular and triangular crystalline AgNPs with mean diameter of 14.6 nm were synthesized. Since heat-inactivated extracts also mediated the formation of AgNPs, enzymatic reactions are likely not involved in AgNPs formation. A high absolute ζ-potential value of the AgNPs, possibly caused by interaction with proteins likely explains the high stability of AgNPs suspensions. AgNPs showed antimicrobial activity against Bacillussubtilis and Escherichiacoli in liquid and solid medium. Copyright © 2011 Elsevier Ltd. All rights reserved.

Using Ag/Ag2O/SnO2 Nanocomposites to Remove Malachite Green by a Photocatalytic Process

NASA Astrophysics Data System (ADS)

Taufik, A.; Paramarta, V.; Prakoso, S. P.; Saleh, R.

2017-03-01

Silver/silver oxide/tin oxide nanocomposites of various weight ratios were synthesized using a microwave-assisted method. The Ag/Ag2O:SnO2 nanoparticle weight ratios used were 25:75, 50:50, and 75:25. All samples were characterized using X-ray diffraction, UV-Vis spectroscopy, Differential Scanning Calorimetry and Thermogravimetric Analysis (TGA). The Ag/Ag2O/SnO2 nanocomposites contained cubic structures provided by the Ag and Ag2O and tetragonal structures provided by the SnO2. The silver resulted in surface plasmon resonance (SPR) at a wavelength of about 435 nm. The silver oxide material was transformed into pure Ag at a temperature of about 370 °C The photocatalytic activity was tested on the degradation of malachite green (MG) from an aqueous solution. The results showed that Ag/Ag2O/SnO2 at a ratio of 50:50 exhibited the best photocatalytic performance for degrading MG under visible-light irradiation. The degradation of MG using Ag/Ag2O/SnO2 nanocomposites followed pseudo first-order kinetic reactions, and electron holes were found to be the main species acting on the degradation process.

A Chemical, High-Temperature Way to Ag1.9Te via Quasi-Topotactic Reaction of Stuetzite-type Ag1.54Te: Structural and Thermoelectric Properties.

PubMed

Baumer, Franziska; Nilges, Tom

2017-11-20

Semiconducting silver tellurides gained reasonable interest in the past years due to its thermoelectric, magneto-caloric, and nonlinear optic properties. Nanostructuring has been frequently used to address quantum-confinement effects of minerals and synthetic compounds in the Ag-Te system. Here, we report on the structural, thermal, and thermoelectric properties of stuetzite-like Ag 1.54 Te (or Ag 4.63 Te 3 ) and Ag 1.9 Te. By a quasi-topotactic reaction upon tellurium evaporation Ag 1.54 Te can be transferred to Ag 1.9 Te after heat treatment. Crystal structures, thermal and thermoelectric properties of stuetzite-like Ag 1.54 Te (or Ag 4.63 Te 3 ) and Ag 1.9 Te were determined by ex situ and in situ experiments. This method represents an elegant chemical way to Ag 1.9 Te, which was so far only accessible electrochemically via electrochemical removal of silver from the mineral hessite (Ag 2 Te). The mixed conductors show reasonable high total electric conductivities, very low thermal conductivities, and large Seebeck coefficients, which result in a significant high thermoelectric figure of 0.57 at 680 K.

[Characteristics of HBV transmission in families with HBsAg-positive fathers and familial clustering of HBV infection].

PubMed

Yang, Y; Jin, L; He, Y L; Liu, J F; Wang, J; Wang, K; Ma, X H; Li, Q; Feng, Y L; Yan, Z; Yi, R T; Chen, T Y; Zhao, Y R

2016-04-01

To investigate the characteristics of hepatitis B virus (HBV) transmission among family members in families with familial clustering of HBV infection and poor outcomes, as well as the prevalence and distribution characteristics of HBsAg in offspring with different parental HBsAg status. The general information of each member in families with poor outcomes were collected from 2007 to 2010, and serological test was performed to analyze the prevalence and distribution of HBsAg in family members. The chi-square test or Fisher's exact test was used to analyze and compare the sex of offspring and the prevalence of HBsAg in them in 266 nuclear families with different paternal and maternal HBsAg status. The positive rates of HBsAg in parents, siblings, children, and spouses of the probands were 20%, 88.2%, 76.8%, and 9.5%, respectively. The nuclear families with HBsAg-positive fathers and HBsAg-negative mothers had a significantly increased proportion of male offspring (male/female ratio = 2.02) compared with those with HBsAg-positive mothers and HBsAg-negative fathers (1.22) or those with HBsAg-negative fathers and mothers (0.96). In addition, in the nuclear families with HBsAg-positive fathers and HBsAg-negative mothers, the male offspring had a significantly higher HBsAg positive rate than female offspring (37.4% vs 13.8%), while in those with HBsAg-positive mothers and HBsAg-negative fathers or those with HBsAg-negative fathers and mothers, HBsAg positive rate showed no significant difference between male and female offspring. In families with familial clustering of HBV infection and poor outcomes, mother-to-child transmission is still the major route of HBV transmission, but father-to-child transmission also plays a role in HBV transmission in this special population. Positive HBsAg in fathers is associated with the increased proportion of male offspring, and father-to-son transmission of HBV is higher than father-to-daughter transmission.

Low molecular weight chitosan-coated silver nanoparticles are effective for the treatment of MRSA-infected wounds.

PubMed

Peng, Yinbo; Song, Chenlu; Yang, Chuanfeng; Guo, Qige; Yao, Min

2017-01-01

Silver nanoparticles (AgNPs) are being widely applied as topical wound materials; however, accumulated deposition of silver in the liver, spleen, and other main organs may lead to organ damage and dysfunction. We report here that low molecular weight chitosan-coated silver nanoparticles (LMWC-AgNPs) are effective against methicillin-resistant Staphylococcus aureus (MRSA), have better biocompatibility, and have lower body absorption characteristics when compared with polyvinylpyrrolidone-coated silver nanoparticles (PVP-AgNPs) and silver nanoparticles without surface stabilizer (uncoated-AgNPs) in a dorsal MRSA wound infection mouse model. LMWC-AgNPs were synthesized by reducing silver nitrate with low molecular weight chitosan as a stabilizer and reducing agent, while PVP-AgNPs were synthesized using polyvinylpyrrolidone as a stabilizer and ethanol as a reducing agent. AgNPs with different surface stabilizers were identified by UV-visible absorption spectrometry, and particle size was determined by transmission electron microscopy. UV-visible absorption spectra of LMWC-AgNPs, PVP-AgNPs and uncoated-AgNPs were similar and their sizes were in the range of 10-30 nm. In vitro experiments showed that the three types of AgNPs had similar MRSA-killing effects, with obvious effect at 4 μg/mL and 100% effect at 8 μg/mL. Bacteriostatic annulus experiments also showed that all the three types of AgNPs had similar antibacterial inhibitory effect at 10 μg/mL. Cell counting kit-8 assay and Hoechst/propidium iodide (PI) staining showed that LMWC-AgNPs were significantly less toxic to human fibroblasts than PVP-AgNPs and uncoated-AgNPs. Treatment of mice with MRSA wound infection demonstrated that the three types of AgNPs effectively controlled MRSA wound infection and promoted wound healing. After continuous application for 14 days, LMWC-AgNPs-treated mice showed significantly reduced liver dysfunction as demonstrated by the reduced alanine aminotransferase and aspartate aminotransferase levels and liver deposition of silver, in comparison to mice treated with uncoated-AgNPs or PVP-AgNPs. Our results demonstrated that LMWC-AgNPs had good anti-MRSA effects, while harboring a better biocompatibility and lowering the body's absorption characteristics.

Biochemical and behavioural responses of the endobenthic bivalve Scrobicularia plana to silver nanoparticles in seawater and microalgal food.

PubMed

Buffet, Pierre-Emmanuel; Pan, Jin-Fen; Poirier, Laurence; Amiard-Triquet, Claude; Amiard, Jean-Claude; Gaudin, Pierre; Risso-de Faverney, Christine; Guibbolini, Marielle; Gilliland, Douglas; Valsami-Jones, Eugenia; Mouneyrac, Catherine

2013-03-01

Because of their bactericidal effects, Ag nanoparticles (Ag NPs) have promising industrial development but could lead to potential ecological risks. The aim of this study was to examine the uptake and effect of silver (soluble or as lactate Ag NPs of 40 nm) at low concentrations (10 μg L(-1)) in the endobenthic bivalve Scrobicularia plana exposed, for 14 days, directly (water) or via the diet (microalgae). The stability of Ag NPs in seawater was examined using dynamic light scattering. Release of soluble Ag from Ag NPs in the experimental media was quantified by using diffusive gradient in thin film. Bioaccumulation of Ag in bivalves was measured by electrothermal atomic absorption spectrometry. Behavioural and biochemical biomarkers were determined in bivalves. Aggregation of Ag NPs and the release of soluble Ag from Ag NPs were observed in the experimental media. For both forms of Ag, bioaccumulation was much more important for waterborne than for dietary exposure. The response of oxidative stress biomarkers (catalase, glutathion S-transferase, superoxide dismutase) was more important after dietary than waterborne exposure to Ag (soluble and NPs). These defences were relatively efficient since they led to a lack of response of damage biomarkers. Burrowing was not affected for bivalves exposed directly or through the diet to both Ag forms but feeding behaviour was impaired after 10 days of dietary exposure. Since no differences of responses to Ag either soluble or nanoparticulate were observed, it seems that labile Ag released from Ag NPs was mainly responsible for toxicity. Copyright © 2012 Elsevier Inc. All rights reserved.

Re-examining the differential familial liability of agoraphobia and panic disorder.

PubMed

Knappe, Susanne; Beesdo-Baum, Katja; Nocon, Agnes; Wittchen, Hans-Ulrich

2012-11-01

Controversy surrounds the question of whether agoraphobia (AG) exists as an independent diagnostic entity apart from panic. In favor of this position, AG without panic disorder (PD) in parents was found being unrelated to offsprings' risk for AG or PD, albeit it may enhance the familial transmission of PD (Nocon et al., Depress Anxiety 2008;25:422-434). However, a recent behavioral genetic analysis (Mosing et al., Depress Anxiety 2009;26:1004-1011) found an increased risk for both PD and AG in siblings of those with AG without PD, casting doubt on whether AG exists independently of PD. Convincing evidence for either position notably requires considering also other anxiety disorders to establish the position of AG relative to the panic/anxiety spectrum. Familial transmission of panic attacks (PAs), PD, and AG was examined in a 10-year prospective-longitudinal community study of 3,021 adolescents and young adults including completed direct and indirect information on parental psychopathology. Standardized diagnostic assessments using the Munich-Composite International Diagnostic Interview allowed generating exclusive diagnostic groups independent from diagnostic hierarchy rules. Parental PD without AG was associated with an increased risk for PA and PD+AG, but not for PD without AG or AG without PD in offspring. Parental AG without PD was unrelated to the offsprings' risk for PA, exclusive PD or AG, or PD+AG. Findings were largely unaffected by adjustment for other offspring or parental anxiety disorders. Findings provide further evidence for the independence of AG apart from the PD spectrum. © 2012 Wiley Periodicals, Inc.

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

Kim, Bojeong; Miller, Jennifer H.; Monsegue, Niven

Physical and chemical transformations and biological responses of silver nanoparticles (AgNPs) in wastewater treatment systems are of particular interest because of the extensive existing and continually growing uses of AgNPs in consumer products. In this study, we investigated the transformation of AgNPs and AgNO 3 during thermophilic anaerobic digestion and effects on selection or transfer of antibiotic resistance genes (ARGs). Ag 2S-NPs, sulfidation products of both AgNPs and AgNO 3, were recovered from raw and digested sludges and were analyzed by analytical transmission electron microscopy (TEM) and X-ray absorption spectroscopy (XAS). TEM and XAS revealed rapid (≤20 min) Ag sulfidationmore » for both Ag treatments. Once transformed, Ag 2S-NPs (as individual NPs or an NP aggregate) persisted for the duration of the batch digestion. The digestion process produced Ag 2S-NPs that were strongly associated with sludge organics and/or other inorganic precipitates. Ag treatments (up to 1,000 mg Ag/kg) did not have an impact on the performance of thermophilic anaerobic digesters or ARG response, as indicated by quantitative polymerase chain reaction measurements of sul1, tet(W), and tet(O) and also intI1, an indicator of horizontal gene transfer of ARGs. Thus, rapid Ag sulfidation and stabilization with organics effectively sequester Ag and prevent biological interactions with the digester microbial community that could induce horizontal gene transfer or adversely impact digester performance through antimicrobial activity. This finding suggests that sulfide-rich anaerobic environments, such as digesters, likely have a high buffer capacity to mitigate the biological effects of AgNPs.« less

Probing the Structural, Electronic, and Magnetic Properties of Ag n V (n = 1-12) Clusters.

PubMed

Xiong, Ran; Die, Dong; Xiao, Lu; Xu, Yong-Gen; Shen, Xu-Ying

2017-12-16

The structural, electronic, and magnetic properties of Ag n V (n = 1-12) clusters have been studied using density functional theory and CALYPSO structure searching method. Geometry optimizations manifest that a vanadium atom in low-energy Ag n V clusters favors the most highly coordinated location. The substitution of one V atom for an Ag atom in Ag n + 1 (n ≥ 5) cluster modifies the lowest energy structure of the host cluster. The infrared spectra, Raman spectra, and photoelectron spectra of Ag n V (n = 1-12) clusters are simulated and can be used to determine the most stable structure in the future. The relative stability, dissociation channel, and chemical activity of the ground states are analyzed through atomic averaged binding energy, dissociation energy, and energy gap. It is found that V atom can improve the stability of the host cluster, Ag 2 excepted. The most possible dissociation channels are Ag n V = Ag + Ag n - 1 V for n = 1 and 4-12 and Ag n V = Ag 2  + Ag n - 2 V for n = 2 and 3. The energy gap of Ag n V cluster with odd n is much smaller than that of Ag n + 1 cluster. Analyses of magnetic property indicate that the total magnetic moment of Ag n V cluster mostly comes from V atom and varies from 1 to 5 μ B . The charge transfer between V and Ag atoms should be responsible for the change of magnetic moment.

Antibacterial activity of nitric oxide releasing silver nanoparticles

NASA Astrophysics Data System (ADS)

Seabra, Amedea B.; Manosalva, Nixson; de Araujo Lima, Bruna; Pelegrino, Milena T.; Brocchi, Marcelo; Rubilar, Olga; Duran, Nelson

2017-06-01

Silver nanoparticles (AgNPs) are well known potent antimicrobial agents. Similarly, the free radical nitric oxide (NO) has important antibacterial activity, and due to its instability, the combination of NO and nanomaterials has been applied in several biomedical applications. The aim of this work was to synthesize, characterize and evaluate the antibacterial activity of a new NO-releasing AgNPs. Herein, AgNPs were synthesized by the reduction of silver ions (Ag+) by catechin, a natural polyphenol and potent antioxidant agent, derived from green tea extract. Catechin acts as a reducing agent and as a capping molecule on the surface of AgNPs, minimizing particle agglomeration. The as-synthesized nanoparticles were characterized by different techniques. The results showed the formation of AgNPs with average hydrodynamic size of 44 nm, polydispersity index of 0.21, and zeta potential of -35.9 mV. X-ray diffraction and Fourier transform infrared spectroscopy revealed the presence of the AgNP core and cathecin as capping agent. The low molecular weight mercaptosuccinic acid (MSA), which contain free thiol group, was added on the surface of catechin-AgNPs, leading to the formation of MSA-catechin-AgNPs (the NO precursor nanoparticle). Free thiol groups of MSA-catechin-AgNPs were nitrosated leading to the formation of S-nitroso-mercaptosuccinic acid (S-nitroso-MSA), the NO donor. The amount of 342 ± 16 µmol of NO was released per gram of S-nitroso-MSA-catechin-AgNPs. The antibacterial activities of catechin-AgNPs, MSA-catechin-AgNPs, and S-nitroso-MSA-catechin-AgNPs were evaluated towards different resistant bacterial strains. The results demonstrated an enhanced antibacterial activity of the NO-releasing AgNP. For instance, the minimal inhibitory concentration values for Pseudomonas aeruginosa (ATCC 27853) incubated with AgNPs-catechin, AgNPs-catechin-MSA, and AgNPs-catechin-S-nitroso-MSA were found to be 62, 125 and 3 µg/mL, respectively. While in the case of Klebsiella pneumoniae (ATCC 700603) the minimum bactericidal concentration values for treatments with AgNPs-catechin, AgNPs-catechin-MSA, and AgNPs-catechin-S-nitroso-MSA were found to be 1000, 500, and 125 µg/mL, respectively. The antibacterial actions of the NO-releasing nanoparticle were superior in comparison with the antibacterial effects of AgNPs, in most of the tested antibiotic resistant bacteria strains. These results highlight the promising uses of NO-releasing AgNPs against resistant bacteria in several biomedical applications.

An interlaboratory comparison of nanosilver characterisation and hazard identification: Harmonising techniques for high quality data.

PubMed

Jemec, Anita; Kahru, Anne; Potthoff, Annegret; Drobne, Damjana; Heinlaan, Margit; Böhme, Steffi; Geppert, Mark; Novak, Sara; Schirmer, Kristin; Rekulapally, Rohit; Singh, Shashi; Aruoja, Villem; Sihtmäe, Mariliis; Juganson, Katre; Käkinen, Aleksandr; Kühnel, Dana

2016-02-01

Within the FP7 EU project NanoValid a consortium of six partners jointly investigated the hazard of silver nanoparticles (AgNPs) paying special attention to methodical aspects that are important for providing high-quality ecotoxicity data. Laboratories were supplied with the same original stock dispersion of AgNPs. All partners applied a harmonised procedure for storage and preparation of toxicity test suspensions. Altogether ten different toxicity assays with a range of environmentally relevant test species from different trophic levels were conducted in parallel to AgNP characterisation in the respective test media. The paper presents a comprehensive dataset of toxicity values and AgNP characteristics like hydrodynamic sizes of AgNP agglomerates and the share (%) of Ag(+)-species (the concentration of Ag(+)-species in relation to the total measured concentration of Ag). The studied AgNP preparation (20.4±6.8 nm primary size, mean total Ag concentration 41.14 mg/L, 46-68% of soluble Ag(+)-species in stock, 123.8±12.2 nm mean z-average value in dH2O) showed extreme toxicity to crustaceans Daphnia magna, algae Pseudokirchneriella subcapitata and zebrafish Danio rerio embryos (EC50<0.01 mg total Ag/L), was very toxic in the in vitro assay with rainbow trout Oncorhynchus mykiss gut cells (EC50: 0.01-1 mg total Ag/L); toxic to bacteria Vibrio fischeri, protozoa Tetrahymena thermophila (EC50: 1-10 mg total Ag/L) and harmful to marine crustaceans Artemia franciscana (EC50: 10-100 mg total Ag/L). Along with AgNPs, also the toxicity of AgNO3 was analyzed. The toxicity data revealed the same hazard ranking for AgNPs and AgNO3 (i.e. the EC50 values were in the same order of magnitude) proving the importance of soluble Ag(+)-species analysis for predicting the hazard of AgNPs. The study clearly points to the need for harmonised procedures for the characterisation of NMs. Harmonised procedures should consider: (i) measuring the AgNP properties like hydrodynamic size and metal ions species in each toxicity test medium at a range of concentrations, and (ii) including soluble metal salt control both in toxicity testing as well as in Ag(+)-species measurements. The present study is among the first nanomaterial interlaboratory comparison studies with the aim to improve the hazard identification testing protocols. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

One-Pot Synthesis of Biocompatible Silver Nanoparticle Composites from Cellulose and Keratin: Characterization and Antimicrobial Activity.

PubMed

Tran, Chieu D; Prosenc, Franja; Franko, Mladen; Benzi, Gerald

2016-12-21

A novel, simple method was developed to synthesize biocompatible composites containing 50% cellulose (CEL) and 50% keratin (KER) and silver in the form of either ionic (Ag + ) or Ag 0 nanoparticles (Ag + NPs or Ag 0 NPs). In this method, butylmethylimmidazolium chloride ([BMIm + Cl - ]), a simple ionic liquid, was used as the sole solvent and silver chloride was added to the [BMIm + Cl - ] solution of [CEL+KER] during the dissolution process. The silver in the composites can be maintained as ionic silver (Ag + ) or completely converted to metallic silver (Ag 0 ) by reducing it with NaBH 4 . The results of spectroscopy [Fourier transform infrared and X-ray diffraction (XRD)] and imaging [scanning electron microscopy (SEM)] measurements confirm that CEL and KER remain chemically intact and homogeneously distributed in the composites. Powder XRD and SEM results show that the silver in the [CEL+KER+Ag + ] and [CEL+KER+Ag 0 ] composites is homogeneously distributed throughout the composites in either Ag + (in the form of AgClNPs) or Ag 0 NPs form with sizes of 27 ± 2 or 9 ± 1 nm, respectively. Both composites were found to exhibit excellent antibacterial activity against many bacteria including Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, methicillin-resistant S. aureus (MRSA), and vancomycin-resistant Enterococus faecalis (VRE). The antibacterial activity of both composites increases with the Ag + or Ag 0 content in the composites. More importantly, for the same bacteria and the same silver content, the [CEL+KER+AgClNPs] composite is relatively more toxic than [CEL+KER+Ag 0 NPs] composite. Experimental results confirm that there was hardly any Ag 0 NPs release from the [CEL+KER+Ag 0 NPs] composite, and hence its antimicrobial activity and biocompatibility is due not to any released Ag 0 NPs but rather entirely to the Ag 0 NPs embedded in the composite. Both AgClNPs and Ag 0 NPs were found to be toxic to human fibroblasts at higher concentration (>0.72 mmol), and for the same silver content, the [CEL+KER+AgClNPs] composite is relatively more toxic than the [CEL+KER+Ag 0 NPs] composite. As expected, by lowering the Ag 0 NPs concentration to 0.48 mmol or less, the [CEL+KER+Ag 0 NPs] composite can be made biocompatible while still retaining its antimicrobial activity against bacteria such as E. coli, S. aureus, P. aeruginosa, MRSA, and VRE. These results, together with our previous finding that [CEL+KER] composites can be used for the controlled delivery of drugs such as ciprofloxacin, clearly indicate that the [CEL+KER+Ag 0 NPs] composite possesses all of the required properties for it to be successfully used as a high-performance dressing to treat chronic ulcerous infected wounds.

Transformation of Four Silver/Silver Chloride Nanoparticles during Anaerobic Treatment of Wastewater and Post-processing of Sewage Sludge

EPA Science Inventory

The increasing use of silver (Ag) nanoparticles [containing either elemental Ag (Ag-NPs) or AgCl (AgCl-NPs)] in commercial products such as textiles will most likely result in these materials reaching wastewater treatment plants. Previous studies indicate that a conversion of Ag-...

Characterization and device performance of (AgCu)(InGa)Se2 absorber layers

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

Hanket, Gregory; Boyle, Jonathan H.; Shafarman, William N.

The study of (AgCu)(InGa)Se2 absorber layers is of interest in that Ag-chalcopyrites exhibit both wider bandgaps and lower melting points than their Cu counterparts. (AgCu)(InGa)Se2 absorber layers were deposited over the composition range 0 < Ag/(Ag+Cu) < 1 and 0.3 < Ga/(In+Ga) < 1.0 using a variety of elemental co-evaporation processes. Films were found to be singlephase over the entire composition range, in contrast to prior studies. Devices with Ga content 0.3 < Ga/(In+Ga) <0.5 tolerated Ag incorporation up to Ag/(Ag+Cu) = 0.5 without appreciable performance loss. Ag-containing films with Ga/(In+Ga) = 0.8 showed improved device characteristics over Cu-only controlmore » samples, in particular a 30-40% increase in short-circuit current. An absorber layer with composition Ag/(Ag+Cu) = 0.75 and Ga/(In+Ga) = 0.8 yielded a device with VOC = 890 mV, JSC = 20.5mA/cm2, fill factor = 71.3%, and η = 13.0%.« less

Metallurgical characterization of experimental Ag-based soldering alloys.

PubMed

Ntasi, Argyro; Al Jabbari, Youssef S; Silikas, Nick; Al Taweel, Sara M; Zinelis, Spiros

2014-10-01

To characterize microstructure, hardness and thermal properties of experimental Ag-based soldering alloys for dental applications. Ag12Ga (AgGa) and Ag10Ga5Sn (AgGaSn) were fabricated by induction melting. Six samples were prepared for each alloy and microstructure, hardness and their melting range were determined by, scanning electron microscopy, energy dispersive X-ray (EDX) microanalysis, X-ray diffraction (XRD), Vickers hardness testing and differential scanning calorimetry (DSC). Both alloys demonstrated a gross dendritic microstructure while according to XRD results both materials consisted predominately of a Ag-rich face centered cubic phase The hardness of AgGa (61 ± 2) was statistically lower than that of AgGaSn (84 ± 2) while the alloys tested showed similar melting range of 627-762 °C for AgGa and 631-756 °C for AgGaSn. The experimental alloys tested demonstrated similar microstructures and melting ranges. Ga and Sn might be used as alternative to Cu and Zn to modify the selected properties of Ag based soldering alloys.

Metallurgical characterization of experimental Ag-based soldering alloys

PubMed Central

Ntasi, Argyro; Al Jabbari, Youssef S.; Silikas, Nick; Al Taweel, Sara M.; Zinelis, Spiros

2014-01-01

Aim To characterize microstructure, hardness and thermal properties of experimental Ag-based soldering alloys for dental applications. Materials and methods Ag12Ga (AgGa) and Ag10Ga5Sn (AgGaSn) were fabricated by induction melting. Six samples were prepared for each alloy and microstructure, hardness and their melting range were determined by, scanning electron microscopy, energy dispersive X-ray (EDX) microanalysis, X-ray diffraction (XRD), Vickers hardness testing and differential scanning calorimetry (DSC). Results Both alloys demonstrated a gross dendritic microstructure while according to XRD results both materials consisted predominately of a Ag-rich face centered cubic phase The hardness of AgGa (61 ± 2) was statistically lower than that of AgGaSn (84 ± 2) while the alloys tested showed similar melting range of 627–762 °C for AgGa and 631–756 °C for AgGaSn. Conclusion The experimental alloys tested demonstrated similar microstructures and melting ranges. Ga and Sn might be used as alternative to Cu and Zn to modify the selected properties of Ag based soldering alloys. PMID:25382945

Biosynthesis of silver nanoparticles by using Ganoderma-mushroom extract

NASA Astrophysics Data System (ADS)

Ekar, S. U.; Khollam, Y. B.; Koinkar, P. M.; Mirji, S. A.; Mane, R. S.; Naushad, M.; Jadhav, S. S.

2015-03-01

Present study reports the biochemical synthesis of silver nanoparticles (Ag-NPs) from aqueous medium by using the extract of medicinal mushroom Ganoderma, as a reducing and stabilizing agents. The Ag-NPs are prepared at room temperature by the reduction of Ag+ to Ag in aqueous solution of AgNO3. The resultant particles are characterized by using UV-visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM) measurement techniques. The formation of Ag-NPs is confirmed by recording the UV-visible absorption spectra for surface plasmon resonance (SPR) where peak around 427 nm. The prominent changes observed in FTIR spectra supported the reduction of Ag+ to Ag. The morphological features of Ag-NPs are evaluated from HRTEM. The spherical Ag-NPs are observed in transmission electron microscopy (TEM) studies. The particle size distribution is found to be nearly uniform with average particle size of 2 nm. The Ag-NPs aged for 15, 30, 60 and 120 days showed no profound effect on the position of SPR peak in UV-visible studies, indicating the protecting/capping ability of medicinal mushroom Ganoderma in the synthesis of Ag-NPs.

Binary Systems and the Initial Mass Function

NASA Astrophysics Data System (ADS)

Malkov, O. Yu.

2017-07-01

In the present paper we discuss advantages and disadvantages of binary stars, which are important for star formation history determination. We show that to make definite conclusions of the initial mass function shape, it is necessary to study binary population well enough to correct the luminosity function for unresolved binaries; to construct the mass-luminosity relation based on wide binaries data, and to separate observational mass functions of primaries, of secondaries, and of unresolved binaries.

Simulating Gravitational Radiation from Binary Black Holes Mergers as LISA Sources

NASA Technical Reports Server (NTRS)

Baker, John

2005-01-01

A viewgraph presentation on the simulation of gravitational waves from Binary Massive Black Holes with LISA observations is shown. The topics include: 1) Massive Black Holes (MBHs); 2) MBH Binaries; 3) Gravitational Wavws from MBH Binaries; 4) Observing with LISA; 5) How LISA sees MBH binary mergers; 6) MBH binary inspirals to LISA; 7) Numerical Relativity Simulations; 8) Numerical Relativity Challenges; 9) Recent Successes; 10) Goddard Team; 11) Binary Black Hole Simulations at Goddard; 12) Goddard Recent Advances; 13) Baker, et al.:GSFC; 13) Starting Farther Out; 14) Comparing Initial Separation; 15) Now with AMR; and 16) Conclusion.

Polar alignment of a protoplanetary disc around an eccentric binary II: Effect of binary and disc parameters

NASA Astrophysics Data System (ADS)

Martin, Rebecca G.; Lubow, Stephen H.

2018-06-01

In a recent paper Martin & Lubow showed that a circumbinary disc around an eccentric binary can undergo damped nodal oscillations that lead to the polar (perpendicular) alignment of the disc relative to the binary orbit. The disc angular momentum vector aligns to the eccentricity vector of the binary. We explore the robustness of this mechanism for a low mass disc (0.001 of the binary mass) and its dependence on system parameters by means of hydrodynamic disc simulations. We describe how the evolution depends upon the disc viscosity, temperature, size, binary mass ratio, orbital eccentricity and inclination. We compare results with predictions of linear theory. We show that polar alignment of a low mass disc may occur over a wide range of binary-disc parameters. We discuss the application of our results to the formation of planetary systems around eccentric binary stars.

KEPLER ECLIPSING BINARIES WITH STELLAR COMPANIONS

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

Gies, D. R.; Matson, R. A.; Guo, Z.

2015-12-15

Many short-period binary stars have distant orbiting companions that have played a role in driving the binary components into close separation. Indirect detection of a tertiary star is possible by measuring apparent changes in eclipse times of eclipsing binaries as the binary orbits the common center of mass. Here we present an analysis of the eclipse timings of 41 eclipsing binaries observed throughout the NASA Kepler mission of long duration and precise photometry. This subset of binaries is characterized by relatively deep and frequent eclipses of both stellar components. We present preliminary orbital elements for seven probable triple stars amongmore » this sample, and we discuss apparent period changes in seven additional eclipsing binaries that may be related to motion about a tertiary in a long period orbit. The results will be used in ongoing investigations of the spectra and light curves of these binaries for further evidence of the presence of third stars.« less

Radial Velocities of 41 Kepler Eclipsing Binaries

NASA Astrophysics Data System (ADS)

Matson, Rachel A.; Gies, Douglas R.; Guo, Zhao; Williams, Stephen J.

2017-12-01

Eclipsing binaries are vital for directly determining stellar parameters without reliance on models or scaling relations. Spectroscopically derived parameters of detached and semi-detached binaries allow us to determine component masses that can inform theories of stellar and binary evolution. Here we present moderate resolution ground-based spectra of stars in close binary systems with and without (detected) tertiary companions observed by NASA’s Kepler mission and analyzed for eclipse timing variations. We obtain radial velocities and spectroscopic orbits for five single-lined and 35 double-lined systems, and confirm one false positive eclipsing binary. For the double-lined spectroscopic binaries, we also determine individual component masses and examine the mass ratio {M}2/{M}1 distribution, which is dominated by binaries with like-mass pairs and semi-detached classical Algol systems that have undergone mass transfer. Finally, we constrain the mass of the tertiary component for five double-lined binaries with previously detected companions.

Search for Gravitational Waves from Low Mass Compact Binary Coalescence in LIGO's Sixth Science Run and Virgo's Science Runs 2 and 3

NASA Technical Reports Server (NTRS)

Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M.; Accadia, T.; Acernese, F.; Adams, C.; Adhikari, R.; Affeldt, C.;

Search for gravitational waves from low mass compact binary coalescence in LIGO's sixth science run and Virgo's science runs 2 and 3

NASA Astrophysics Data System (ADS)

Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M.; Accadia, T.; Acernese, F.; Adams, C.; Adhikari, R.; Affeldt, C.; Agathos, M.; Ajith, P.; Allen, B.; Allen, G. S.; Amador Ceron, E.; Amariutei, D.; Amin, R. S.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Arain, M. A.; Araya, M. C.; Aston, S. M.; Astone, P.; Atkinson, D.; Aufmuth, P.; Aulbert, C.; Aylott, B. E.; Babak, S.; Baker, P.; Ballardin, G.; Ballmer, S.; Barker, D.; Barone, F.; Barr, B.; Barriga, P.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Bastarrika, M.; Basti, A.; Batch, J.; Bauchrowitz, J.; Bauer, Th. S.; Bebronne, M.; Behnke, B.; Beker, M. G.; Bell, A. S.; Belletoile, A.; Belopolski, I.; Benacquista, M.; Berliner, J. M.; Bertolini, A.; Betzwieser, J.; Beveridge, N.; Beyersdorf, P. T.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Biswas, R.; Bitossi, M.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Blom, M.; Bock, O.; Bodiya, T. P.; Bogan, C.; Bondarescu, R.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Boschi, V.; Bose, S.; Bosi, L.; Bouhou, B.; Braccini, S.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Breyer, J.; Briant, T.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Brummit, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Burguet–Castell, J.; Burmeister, O.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Calloni, E.; Camp, J. B.; Campsie, P.; Cannizzo, J.; Cannon, K.; Canuel, B.; Cao, J.; Capano, C. D.; Carbognani, F.; Caride, S.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chaibi, O.; Chalermsongsak, T.; Chalkley, E.; Charlton, P.; Chassande-Mottin, E.; Chelkowski, S.; Chen, Y.; Chincarini, A.; Chiummo, A.; Cho, H.; Christensen, N.; Chua, S. S. Y.; Chung, C. T. Y.; Chung, S.; Ciani, G.; Clara, F.; Clark, D. E.; Clark, J.; Clayton, J. H.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colacino, C. N.; Colas, J.; Colla, A.; Colombini, M.; Conte, A.; Conte, R.; Cook, D.; Corbitt, T. R.; Cordier, M.; Cornish, N.; Corsi, A.; Costa, C. A.; Coughlin, M.; Coulon, J.-P.; Couvares, P.; Coward, D. M.; Coyne, D. C.; Creighton, J. D. E.; Creighton, T. D.; Cruise, A. M.; Cumming, A.; Cunningham, L.; Cuoco, E.; Cutler, R. M.; Dahl, K.; Danilishin, S. L.; Dannenberg, R.; D'Antonio, S.; Danzmann, K.; Dattilo, V.; Daudert, B.; Daveloza, H.; Davier, M.; Davies, G.; Daw, E. J.; Day, R.; Dayanga, T.; De Rosa, R.; DeBra, D.; Debreczeni, G.; Degallaix, J.; Del Pozzo, W.; del Prete, M.; Dent, T.; Dergachev, V.; DeRosa, R.; DeSalvo, R.; Dhurandhar, S.; Di Fiore, L.; Di Lieto, A.; Di Palma, I.; Di Paolo Emilio, M.; Di Virgilio, A.; Díaz, M.; Dietz, A.; DiGuglielmo, J.; Donovan, F.; Dooley, K. L.; Dorsher, S.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Dumas, J.-C.; Dwyer, S.; Eberle, T.; Edgar, M.; Edwards, M.; Effler, A.; Ehrens, P.; Endrőczi, G.; Engel, R.; Etzel, T.; Evans, K.; Evans, M.; Evans, T.; Factourovich, M.; Fafone, V.; Fairhurst, S.; Fan, Y.; Farr, B. F.; Farr, W.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Ferrante, I.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Fisher, R. P.; Flaminio, R.; Flanigan, M.; Foley, S.; Forsi, E.; Forte, L. A.; Fotopoulos, N.; Fournier, J.-D.; Franc, J.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Friedrich, D.; Fritschel, P.; Frolov, V. V.; Fulda, P. J.; Fyffe, M.; Galimberti, M.; Gammaitoni, L.; Ganija, M. R.; Garcia, J.; Garofoli, J. A.; Garufi, F.; Gáspár, M. E.; Gemme, G.; Geng, R.; Genin, E.; Gennai, A.; Gergely, L. Á.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Giazotto, A.; Gill, C.; Goetz, E.; Goggin, L. M.; González, G.; Gorodetsky, M. L.; Goßler, S.; Gouaty, R.; Graef, C.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Gray, N.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Greverie, C.; Grosso, R.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guido, C.; Gupta, R.; Gustafson, E. K.; Gustafson, R.; Ha, T.; Hage, B.; Hallam, J. M.; Hammer, D.; Hammond, G.; Hanks, J.; Hanna, C.; Hanson, J.; Hardt, A.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Hartman, M. T.; Haughian, K.; Hayama, K.; Hayau, J.-F.; Heefner, J.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hendry, M. A.; Heng, I. S.; Heptonstall, A. W.; Herrera, V.; Hewitson, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Holt, K.; Hong, T.; Hooper, S.; Hosken, D. J.; Hough, J.; Howell, E. J.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Izumi, K.; Jacobson, M.; Jang, H.; Jaranowski, P.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kamaretsos, I.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Katsavounidis, E.; Katzman, W.; Kaufer, H.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kells, W.; Keppel, D. G.; Keresztes, Z.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, B.; Kim, C.; Kim, D.; Kim, H.; Kim, K.; Kim, N.; Kim, Y.-M.; King, P. J.; Kinsey, M.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kokeyama, K.; Kondrashov, V.; Kopparapu, R.; Koranda, S.; Korth, W. Z.; Kowalska, I.; Kozak, D.; Kringel, V.; Krishnamurthy, S.; Krishnan, B.; Królak, A.; Kuehn, G.; Kumar, R.; Kwee, P.; Lam, P. K.; Landry, M.; Lang, M.; Lantz, B.; Lastzka, N.; Lawrie, C.; Lazzarini, A.; Leaci, P.; Lee, C. H.; Lee, H. M.; Leindecker, N.; Leong, J. R.; Leonor, I.; Leroy, N.; Letendre, N.; Li, J.; Li, T. G. F.; Liguori, N.; Lindquist, P. E.; Lockerbie, N. A.; Lodhia, D.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Luan, J.; Lubinski, M.; Lück, H.; Lundgren, A. P.; Macdonald, E.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Mageswaran, M.; Mailand, K.; Majorana, E.; Maksimovic, I.; Man, N.; Mandel, I.; Mandic, V.; Mantovani, M.; Marandi, A.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A.; Maros, E.; Marque, J.; Martelli, F.; Martin, I. W.; Martin, R. M.; Marx, J. N.; Mason, K.; Masserot, A.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McIntyre, G.; McIver, J.; McKechan, D. J. A.; Meadors, G. D.; Mehmet, M.; Meier, T.; Melatos, A.; Melissinos, A. C.; Mendell, G.; Menendez, D.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miao, H.; Michel, C.; Milano, L.; Miller, J.; Minenkov, Y.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Miyakawa, O.; Moe, B.; Moesta, P.; Mohan, M.; Mohanty, S. D.; Mohapatra, S. R. P.; Moraru, D.; Moreno, G.; Morgado, N.; Morgia, A.; Mori, T.; Mosca, S.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Müller-Ebhardt, H.; Munch, J.; Murphy, D.; Murray, P. G.; Mytidis, A.; Nash, T.; Naticchioni, L.; Nawrodt, R.; Necula, V.; Nelson, J.; Newton, G.; Nishizawa, A.; Nocera, F.; Nolting, D.; Nuttall, L.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Oldenburg, R. G.; O'Reilly, B.; O'Shaughnessy, R.; Osthelder, C.; Ott, C. D.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Page, A.; Pagliaroli, G.; Palladino, L.; Palomba, C.; Pan, Y.; Pankow, C.; Paoletti, F.; Papa, M. A.; Parisi, M.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patel, P.; Pedraza, M.; Peiris, P.; Pekowsky, L.; Penn, S.; Peralta, C.; Perreca, A.; Persichetti, G.; Phelps, M.; Pickenpack, M.; Piergiovanni, F.; Pietka, M.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Plissi, M. V.; Poggiani, R.; Pöld, J.; Postiglione, F.; Prato, M.; Predoi, V.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Quetschke, V.; Raab, F. J.; Rabeling, D. S.; Rácz, I.; Radkins, H.; Raffai, P.; Rakhmanov, M.; Ramet, C. R.; Rankins, B.; Rapagnani, P.; Raymond, V.; Re, V.; Redwine, K.; Reed, C. M.; Reed, T.; Regimbau, T.; Reid, S.; Reitze, D. H.; Ricci, F.; Riesen, R.; Riles, K.; Robertson, N. A.; Robinet, F.; Robinson, C.; Robinson, E. L.; Rocchi, A.; Roddy, S.; Rodriguez, C.; Rodruck, M.; Rolland, L.; Rollins, J.; Romano, J. D.; Romano, R.; Romie, J. H.; Rosińska, D.; Röver, C.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Ryll, H.; Sainathan, P.; Sakosky, M.; Salemi, F.; Samblowski, A.; Sammut, L.; Sancho de la Jordana, L.; Sandberg, V.; Sankar, S.; Sannibale, V.; Santamaría, L.; Santiago-Prieto, I.; Santostasi, G.; Sassolas, B.; Sathyaprakash, B. S.; Sato, S.; Saulson, P. R.; Savage, R. L.; Schilling, R.; Schlamminger, S.; Schnabel, R.; Schofield, R. M. S.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Searle, A. C.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sergeev, A.; Shaddock, D. A.; Shaltev, M.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sibley, A.; Siemens, X.; Sigg, D.; Singer, A.; Singer, L.; Sintes, A. M.; Skelton, G.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Smith, N. D.; Smith, R. J. E.; Somiya, K.; Sorazu, B.; Soto, J.; Speirits, F. C.; Sperandio, L.; Stefszky, M.; Stein, A. J.; Steinert, E.; Steinlechner, J.; Steinlechner, S.; Steplewski, S.; Stochino, A.; Stone, R.; Strain, K. A.; Strigin, S.; Stroeer, A. S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sung, M.; Susmithan, S.; Sutton, P. J.; Swinkels, B.; Tacca, M.; Taffarello, L.; Talukder, D.; Tanner, D. B.; Tarabrin, S. P.; Taylor, J. R.; Taylor, R.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Thüring, A.; Titsler, C.; Tokmakov, K. V.; Toncelli, A.; Tonelli, M.; Torre, O.; Torres, C.; Torrie, C. I.; Tournefier, E.; Travasso, F.; Traylor, G.; Trias, M.; Tseng, K.; Tucker, E.; Ugolini, D.; Urbanek, K.; Vahlbruch, H.; Vajente, G.; Vallisneri, M.; van den Brand, J. F. J.; Van Den Broeck, C.; van der Putten, S.; van Veggel, A. A.; Vass, S.; Vasuth, M.; Vaulin, R.; Vavoulidis, M.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Veltkamp, C.; Verkindt, D.; Vetrano, F.; Viceré, A.; Villar, A. E.; Vinet, J.-Y.; Vitale, S.; Vitale, S.; Vocca, H.; Vorvick, C.; Vyatchanin, S. P.; Wade, A.; Waldman, S. J.; Wallace, L.; Wan, Y.; Wang, X.; Wang, Z.; Wanner, A.; Ward, R. L.; Was, M.; Wei, P.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Wen, S.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D.; Whiting, B. F.; Wilkinson, C.; Willems, P. A.; Williams, H. R.; Williams, L.; Willke, B.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wiseman, A. G.; Wittel, H.; Woan, G.; Wooley, R.; Worden, J.; Yablon, J.; Yakushin, I.; Yamamoto, H.; Yamamoto, K.; Yang, H.; Yeaton-Massey, D.; Yoshida, S.; Yu, P.; Yvert, M.; Zadroźny, A.; Zanolin, M.; Zendri, J.-P.; Zhang, F.; Zhang, L.; Zhang, W.; Zhang, Z.; Zhao, C.; Zotov, N.; Zucker, M. E.; Zweizig, J.

2012-04-01

We report on a search for gravitational waves from coalescing compact binaries using LIGO and Virgo observations between July 7, 2009, and October 20, 2010. We searched for signals from binaries with total mass between 2 and 25M⊙; this includes binary neutron stars, binary black holes, and binaries consisting of a black hole and neutron star. The detectors were sensitive to systems up to 40 Mpc distant for binary neutron stars, and further for higher mass systems. No gravitational-wave signals were detected. We report upper limits on the rate of compact binary coalescence as a function of total mass, including the results from previous LIGO and Virgo observations. The cumulative 90% confidence rate upper limits of the binary coalescence of binary neutron star, neutron star-black hole, and binary black hole systems are 1.3×10-4, 3.1×10-5, and 6.4×10-6Mpc-3yr-1, respectively. These upper limits are up to a factor 1.4 lower than previously derived limits. We also report on results from a blind injection challenge.

HNO₃-assisted polyol synthesis of ultralarge single-crystalline Ag microplates and their far propagation length of surface plasmon polariton.

PubMed

Chang, Cheng-Wei; Lin, Fan-Cheng; Chiu, Chun-Ya; Su, Chung-Yi; Huang, Jer-Shing; Perng, Tsong-Pyng; Yen, Ta-Jen

2014-07-23

We developed a HNO3-assisted polyol reduction method to synthesize ultralarge single-crystalline Ag microplates routinely. The edge length of the synthesized Ag microplates reaches 50 μm, and their top facets are (111). The mechanism for dramatically enlarging single-crystalline Ag structure stems from a series of competitive anisotropic growths, primarily governed by carefully tuning the adsorption of Ag(0) by ethylene glycol and the desorption of Ag(0) by a cyanide ion on Ag(100). Finally, we measured the propagation length of surface plasmon polaritons along the air/Ag interface under 534 nm laser excitation. Our single-crystalline Ag microplate exhibited a propagation length (11.22 μm) considerably greater than that of the conventional E-gun deposited Ag thin film (5.27 μm).

Epitaxial-Growth-Induced Junction Welding of Silver Nanowire Network Electrodes.

PubMed

Kang, Hyungseok; Song, Sol-Ji; Sul, Young Eun; An, Byeong-Seon; Yin, Zhenxing; Choi, Yongsuk; Pu, Lyongsun; Yang, Cheol-Woong; Kim, Youn Sang; Cho, Sung Min; Kim, Jung-Gu; Cho, Jeong Ho

2018-05-22

In this study, we developed a roll-to-roll Ag electroplating process for metallic nanowire electrodes using a galvanostatic mode. Electroplating is a low-cost and facile method for deposition of metal onto a target surface with precise control of both the composition and the thickness. Metallic nanowire networks [silver nanowires (AgNWs) and copper nanowires (CuNWs)] coated onto a polyethylene terephthalate (PET) film were immersed directly in an electroplating bath containing AgNO 3 . Solvated silver ions (Ag + ions) were deposited onto the nanowire surface through application of a constant current via an external circuit between the nanowire networks (cathode) and a Ag plate (anode). The amount of electroplated Ag was systematically controlled by changing both the applied current density and the electroplating time, which enabled precise control of the sheet resistance and optical transmittance of the metallic nanowire networks. The optimized Ag-electroplated AgNW (Ag-AgNW) films exhibited a sheet resistance of ∼19 Ω/sq at an optical transmittance of 90% (550 nm). A transmission electron microscopy study confirmed that Ag grew epitaxially on the AgNW surface, but a polycrystalline Ag structure was formed on the CuNW surface. The Ag-electroplated metallic nanowire electrodes were successfully applied to various electronic devices such as organic light-emitting diodes, triboelectric nanogenerators, and a resistive touch panel. The proposed roll-to-roll Ag electroplating process provides a simple, low-cost, and scalable method for the fabrication of enhanced transparent conductive electrode materials for next-generation electronic devices.

Coordination Chemistry of Diiodine and Implications for the Oxidation Capacity of the Synergistic Ag(+) /X2 (X=Cl, Br, I) System.

PubMed

Malinowski, Przemysław J; Himmel, Daniel; Krossing, Ingo

2016-08-01

The synergistic Ag(+) /X2 system (X=Cl, Br, I) is a very strong, but ill-defined oxidant-more powerful than X2 or Ag(+) alone. Intermediates for its action may include [Agm (X2 )n ](m+) complexes. Here, we report on an unexpectedly variable coordination chemistry of diiodine towards this direction: (A)Ag-I2 -Ag(A), [Ag2 (I2 )4 ](2+) (A(-) )2 and [Ag2 (I2 )6 ](2+) (A(-) )2 ⋅(I2 )x≈0.65 form by reaction of Ag(A) (A=Al(OR(F) )4 ; R(F) =C(CF3 )3 ) with diiodine (single crystal/powder XRD, Raman spectra and quantum-mechanical calculations). The molecular (A)Ag-I2 -Ag(A) is ideally set up to act as a 2 e(-) oxidant with stoichiometric formation of 2 AgI and 2 A(-) . Preliminary reactivity tests proved this (A)Ag-I2 -Ag(A) starting material to oxidize n-C5 H12 , C3 H8 , CH2 Cl2 , P4 or S8 at room temperature. A rough estimate of its electron affinity places it amongst very strong oxidizers like MF6 (M=4d metals). This suggests that (A)Ag-I2 -Ag(A) will serve as an easily in bulk accessible, well-defined, and very potent oxidant with multiple applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photobiosynthesis of stable and functional silver/silver chloride nanoparticles with hydrolytic activity using hyperthermophilic β-glucosidases with industrial potential.

PubMed

Araújo, Juscemácia N; Tofanello, Aryane; da Silva, Viviam M; Sato, Juliana A P; Squina, Fabio M; Nantes, Iseli L; Garcia, Wanius

2017-09-01

The β-glucosidases are important enzymes employed in a large number of processes and industrial applications, including biofuel production from biomass. Therefore, in this study, we reported for the first time the photobiosynthesis of stable and functional silver/silver chloride nanoparticles (Ag/AgCl-NPs) using two hyperthermostable bacterial β-glucosidases with industrial potential. The syntheses were straightforward and rapid processes carried out by mixing β-glucosidase and silver nitrate (in buffer 10mM Tris-HCl, pH 8) under irradiation with light (over a wavelength range of 450-600nm), therefore, compatible with the green chemistry procedure. Synthesized Ag/AgCl-NPs were characterized using a series of physical techniques. Absorption spectroscopy showed a strong absorption band centered at 460nm due to surface plasmon resonance of the Ag-NPs. X-ray diffraction analysis revealed that the Ag/AgCl-NPs were purely crystalline in nature. Under electron microscopy, Ag/AgCl-NPs of variable diameter ranging from 10 to 100nm can be visualized. Furthermore, electron microscopy, zeta potential and Fourier transform infrared spectroscopy results confirmed the presence of β-glucosidases coating and stabilizing the Ag/AgCl-NPs. Finally, the results showed that the enzymatic activities were maintained in the β-glucosidases assisted Ag/AgCl-NPs. The information described here should provide a useful basis for future studies of β-glucosidases assisted Ag/AgCl-NPs, including biotechnological applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Antibacterial abilities and biocompatibilities of Ti-Ag alloys with nanotubular coatings.

PubMed

Liu, Xingwang; Tian, Ang; You, Junhua; Zhang, Hangzhou; Wu, Lin; Bai, Xizhuang; Lei, Zeming; Shi, Xiaoguo; Xue, Xiangxin; Wang, Hanning

To endow implants with both short- and long-term antibacterial activities without impairing their biocompatibility, novel Ti-Ag alloy substrates with different proportions of Ag (1, 2, and 4 wt% Ag) were generated with nanotubular coverings (TiAg-NT). Unlike commercial pure Ti and titania nanotube, the TiAg-NT samples exhibited short-term antibacterial activity against Staphylococcus aureus ( S. aureus ), as confirmed by scanning electron microscopy and double staining with SYTO 9 and propidium iodide. A film applicator coating assay and a zone of inhibition assay were performed to investigate the long-term antibacterial activities of the samples. The cellular viability and cytotoxicity were evaluated through a Cell Counting Kit-8 assay. Annexin V-FITC/propidium iodide double staining was used to assess the level of MG63 cell apoptosis on each sample. All of the TiAg-NT samples, particularly the nanotube-coated Ti-Ag alloy with 2 wt% Ag (Ti2%Ag-NT), could effectively inhibit bacterial adhesion and kill the majority of adhered S. aureus on the first day of culture. Additionally, the excellent antibacterial abilities exhibited by the TiAg-NT samples were sustained for at least 30 days. Although Ti2%Ag-NT had less biocompatibility than titania nanotube, its performance was satisfactory, as demonstrated by the higher cellular viability and lower cell apoptosis rate obtained with it compared with those achieved with commercial pure Ti. The Ti1%Ag-NT and Ti4%Ag-NT samples did not yield good cell viability. This study indicates that the TiAg-NT samples can prevent biofilm formation and maintain their antibacterial ability for at least 1 month. Ti2%Ag-NT exhibited better antibacterial ability and biocompatibility than commercial pure Ti, which could be attributed to the synergistic effect of the presence of Ag (2 wt%) and the morphology of the nanotubes. Ti2%Ag-NT may offer a potential implant material that is capable of preventing implant-related infection.

Antibacterial abilities and biocompatibilities of Ti–Ag alloys with nanotubular coatings

PubMed Central

Liu, Xingwang; Tian, Ang; You, Junhua; Zhang, Hangzhou; Wu, Lin; Bai, Xizhuang; Lei, Zeming; Shi, Xiaoguo; Xue, Xiangxin; Wang, Hanning

2016-01-01

Purpose To endow implants with both short- and long-term antibacterial activities without impairing their biocompatibility, novel Ti–Ag alloy substrates with different proportions of Ag (1, 2, and 4 wt% Ag) were generated with nanotubular coverings (TiAg-NT). Methods Unlike commercial pure Ti and titania nanotube, the TiAg-NT samples exhibited short-term antibacterial activity against Staphylococcus aureus (S. aureus), as confirmed by scanning electron microscopy and double staining with SYTO 9 and propidium iodide. A film applicator coating assay and a zone of inhibition assay were performed to investigate the long-term antibacterial activities of the samples. The cellular viability and cytotoxicity were evaluated through a Cell Counting Kit-8 assay. Annexin V-FITC/propidium iodide double staining was used to assess the level of MG63 cell apoptosis on each sample. Results All of the TiAg-NT samples, particularly the nanotube-coated Ti–Ag alloy with 2 wt% Ag (Ti2%Ag-NT), could effectively inhibit bacterial adhesion and kill the majority of adhered S. aureus on the first day of culture. Additionally, the excellent antibacterial abilities exhibited by the TiAg-NT samples were sustained for at least 30 days. Although Ti2%Ag-NT had less biocompatibility than titania nanotube, its performance was satisfactory, as demonstrated by the higher cellular viability and lower cell apoptosis rate obtained with it compared with those achieved with commercial pure Ti. The Ti1%Ag-NT and Ti4%Ag-NT samples did not yield good cell viability. Conclusion This study indicates that the TiAg-NT samples can prevent biofilm formation and maintain their antibacterial ability for at least 1 month. Ti2%Ag-NT exhibited better antibacterial ability and biocompatibility than commercial pure Ti, which could be attributed to the synergistic effect of the presence of Ag (2 wt%) and the morphology of the nanotubes. Ti2%Ag-NT may offer a potential implant material that is capable of preventing implant-related infection. PMID:27843315

Retention of silver nano-particles and silver ions in calcareous soils: Influence of soil properties.

PubMed

Rahmatpour, Samaneh; Shirvani, Mehran; Mosaddeghi, Mohammad R; Bazarganipour, Mehdi

2017-05-15

The rapid production and application of silver nanoparticles (AgNPs) have led to significant release of AgNPs into the terrestrial environments. Once released into the soil, AgNPs could enter into different interactions with soil particles which play key roles in controlling the fate and transport of these nanoparticles. In spite of that, experimental studies on the retention of AgNPs in soils are very scarce. Hence, the key objective of this research was to find out the retention behavior of AgNPs and Ag(I) ions in a range of calcareous soils. A second objective was to determine the extent to which the physico-chemical properties of the soils influence the Ag retention parameters. To this end, isothermal batch experiments were used to determine the retention of Poly(vinylpyrrolidinone)-capped AgNPs (PVP-AgNPs) and Ag(I) ions by nine calcareous soils with a diversity of physico-chemical properties. The results revealed that the retention data for both PVP-AgNPs and Ag(I) ions were well described by the classical Freundlich and Langmuir isothermal equations. The retention of PVP-AgNPs and Ag(I) ions was positively correlated to clay and organic carbon (OC) contents as well as electrical conductivity (EC), pH, and cation exchange capacity (CEC) of the soils. Due to multicolinearity among the soil properties, principal component analysis (PCA) was used to group the soil properties which affect the retention of PVP-AgNPs and Ag(I) ions. Accordingly, we identified two groups of soil properties controlling retention of PVP-AgNPs and Ag(I) ions in the calcareous soils. The first group comprised soil solid phase parameters like clay, OC, and CEC, which generally control hetero-aggregation and adsorption reactions and the second group included soil solution variables such as EC and pH as well as Cl - and Ca 2+ concentrations, which are supposed to mainly affect homo-aggregation and precipitation reactions. Copyright © 2017. Published by Elsevier Ltd.

Hepatitis B core-related antigen (HBcrAg) levels in the natural history of hepatitis B virus infection in a large European cohort predominantly infected with genotypes A and D.

PubMed

Maasoumy, B; Wiegand, S B; Jaroszewicz, J; Bremer, B; Lehmann, P; Deterding, K; Taranta, A; Manns, M P; Wedemeyer, H; Glebe, D; Cornberg, M

2015-06-01

Hepatitis B core-related antigen (HBcrAg) has been suggested as an additional marker of hepatitis B virus (HBV) infection. HBcrAg combines the antigenic reactivity resulting from denatured hepatitis B e antigen (HBeAg), HBV core antigen and an artificial core-related protein (p22cr). In Asian patients, high levels of HBcrAg have been suggested to be an independent risk factor for hepatocellular carcinoma, while low levels could guide safe cessation of treatment with nucleos(t)ide analogues. We here studied HBcrAg levels in different phases of HBV infection in a large European cohort predominantly infected with genotypes A and D: HBeAg-positive immune tolerance (n = 30), HBeAg-positive immune clearance (IC) (n = 60), HBeAg-negative hepatitis (ENH) (n = 50), HBeAg-negative inactive/quiescent carrier phase (c) (n = 109) and acute hepatitis B (n = 8). Median HBcrAg levels were high in the immune tolerance and immune clearance phases (8.41 and 8.11 log U/mL, respectively), lower in ENH subjects (4.82 log U/mL) but only 2.00 log U/mL in ENQ subjects. Correlation between HBcrAg and HBV DNA varied among the different phases of HBV infection, while HBcrAg moderately correlated with hepatitis B surface antigen in all phases. ENQ patients had HBcrAg levels <3 log U/mL in 79%, in contrast to only 12% in the ENH group. HBcrAg levels vary significantly during the different phases of HBV infection. HBcrAg may serve as valuable marker for virus replication and reflect the transcriptional activity of intrahepatic cccDNA. In HBeAg-negative patients, HBcrAg may help to distinguish between inactive carriers (ENQ) and those with active disease (ENH). Copyright © 2015 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

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

Zhang, Shiyan; Mei, Dajiang, E-mail: meidajiang718@pku.edu.cn; Du, Xin

Ag{sub 1−x}Ga{sub 1−x}Si{sub x}Se{sub 2} solutions with high Si doping level (x=1/2) are considered and new compound AgGaSiSe{sub 4} has been synthesized. It crystallizes in space group Aea2 and possesses very long axis of a=63.06(1)Å. The three-dimensional framework in AgGaSiSe{sub 4} is composed of AgSe{sub 3} trigonal planar units, AgSe{sub 4} tetrahedra and MSe{sub 4}(M=Si, Ga) tetrahedra. AgGaSiSe{sub 4} is a congruently melting compound with the melt temperature of 759 °C. The diffuse reflectance measurements reveal the band gap of 2.63 eV in AgGaSiSe{sub 4} and the value is 0.33 eV larger than that of Ag{sub 3}Ga{sub 3}SiSe{sub 8} (2.30more » eV). - Graphical abstract: The Ag{sub 1−x}Ga{sub 1−x}Si{sub x}Se{sub 2} with high Si doping level (x=1/2) has been studied and the new compound AgGaSiSe{sub 4} was synthesized for the first time. AgGaSiSe{sub 4} crystallizes in a new structure type in space group Aea2 and adopts a three-dimensional framework consisting of AgSe{sub 3} trigonal planar units, AgSe{sub 4} tetrahedra and MSe{sub 4} (M=Si, Ge) tetrahedra. Display Omitted - Highlights: • Study of Ag{sub 1−x}Ga{sub 1−x}Si{sub x}Se{sub 2} with high Si doping level (x=1/2). • Successful synthesis of new compound named AgGaSiSe{sub 4}. • AgGaSiSe{sub 4} crystallizes in space group Aea2 and adopts a three-dimensional framework. • The energy band gap of AgGaSiSe{sub 4} is enlarged compared with Ag{sub 3}Ga{sub 3}SiSe{sub 8}.« less

Shape-dependent antibacterial activity of silver nanoparticles on Escherichia coli and Enterococcus faecium bacterium

NASA Astrophysics Data System (ADS)

Alshareef, A.; Laird, K.; Cross, R. B. M.

2017-12-01

Silver nanoparticles (AgNPs) have been shown to exhibit strong antibacterial activity against both Gram-positive bacteria and Gram-negative bacteria including antibiotic resistant strains. This study aims to compare the bactericidal effect of different shaped AgNPs (spherical and truncated octahedral) against Escherichia coli and Enterococcus faecium. The antimicrobial activity of a range of concentrations (50, 100, 1000 μg/ml) was determined over 24 h using both optical density and viable counts. Truncated octahedral AgNPs (AgNOct) were found to be more active when compared with spherical AgNPs (AgNS). The difference in shape resulted in differences in efficacy which may be due to the higher surface area of AgNOct compared to AgNS, and differences in active facets and surface energies, with AgNPs having a bacteriostatic effect and AgNOct being bactericidal after 4 h. The results suggest that AgNPs can be used as effective growth inhibitors in different microorganisms, rendering them applicable to various medical devices and antimicrobial control systems.

Agoraphobia With and Without Panic Disorder: A 20-Year Follow-up of Integrated Exposure and Psychodynamic Therapy.

PubMed

Hoffart, Asle; Hedley, Liv M; Svanøe, Karol; Langkaas, Tomas Formo; Sexton, Harold

2016-02-01

The aim of the current study was to compare the 20-year outcome in panic disorder with agoraphobia (PD with AG) and agoraphobia without panic disorder (AG without PD) patients after inpatient psychological treatment. Of 53 eligible patients having completed a medication-free integrated exposure and psychodynamic treatment, 38 (71.7%)-25 PD with AG and 13 AG without PD patients-attended 20-year follow-up. AG without PD patients improved less than PD with AG patients did on primary outcome measures. In the PD with AG group, there were large uncontrolled effect sizes (<-2.30). More of the AG without PD patients had avoidant personality disorder at pretreatment, but the presence of this disorder did not predict outcome. The follow-up results support that PD with AG and AG without PD are two different disorders. The results also suggest that the very long-term outcome in PD with AG patients is excellent for this integrated treatment.

Isomorphism and solid solutions among Ag- and Au-selenides

NASA Astrophysics Data System (ADS)

Palyanova, Galina A.; Seryotkin, Yurii V.; Kokh, Konstantin A.; Bakakin, Vladimir V.

2016-09-01

Au-Ag selenides were synthesized by heating stoichiometric mixtures of elementary substances of initial compositions Ag2-xAuxSe with a step of х=0.25 (0≤х≤2) to 1050 °С and annealing at 500 °C. Scanning electron microscopy, optical microscopy, electron microprobe analysis and X-ray powder diffraction methods have been applied to study synthesized samples. Results of studies of synthesized products revealed the existence of three solid solutions with limited isomorphism Ag↔Au: naumannite Ag2Se - Ag1.94Au0.06Se, fischesserite Ag3AuSe2 - Ag3.2Au0.8Se2 and gold selenide AuSe - Au0.94Ag0.06Se. Solid solutions and AgAuSe phases were added to the phase diagram of Ag-Au-Se system. Crystal-chemical interpretation of Ag-Au isomorphism in selenides was made on the basis of structural features of fischesserite, naumannite, and AuSe.

Effect of Ag nanoparticles deposition on photocatalytic activity of Ag{sub 2}SO{sub 3}

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

Zhang, Xuan, E-mail: xzhang@dhu.edu.cn; Wang, Qi; Hu, Jin-Wen

Highlights: • Ag{sub 2}SO{sub 3} was developed as novel photocatalyst. • The effect of Ag nanoparticles deposition on photocatalytic activity was investigated. • The activation and deactivation mechanism was proposed. - Abstract: A novel photocatalyst Ag{sub 2}SO{sub 3} was prepared and the effect of Ag nanoparticles, photo-deposited on the surface of Ag{sub 2}SO{sub 3}, on its photocatalytic activity was investigated. The as-prepared photocatalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–vis diffuse reflection spectroscopy (DRS). The photocatalytic activity was evaluated by photo-degradation of rhodamine B dye under UV light irradiation. It was found that the photocatalyticmore » activity of Ag{sub 2}SO{sub 3} was initially enhanced with deposition of Ag nanoparticles, but subsequently declined with Ag nanoparticles overloaded. The possible mechanism was proposed based on experimental results. These findings may contribute to developing novel photocatalysts and understanding of fundamentals of Ag-based photocatalytic materials.« less

Nanoporous Ag prepared from the melt-spun Cu-Ag alloys

NASA Astrophysics Data System (ADS)

Li, Guijing; Song, Xiaoping; Sun, Zhanbo; Yang, Shengchun; Ding, Bingjun; Yang, Sen; Yang, Zhimao; Wang, Fei

2011-07-01

Nanoporous Ag ribbons with different morphology and porosity were achieved by the electrochemical corrosion of the melt-spun Cu-Ag alloys. The Cu-rich phase in the alloys was removed, resulting in the formation of the nanopores distributed across the whole ribbon. It is found that the structures, morphology and porosity of the nanoporous Ag ribbons were dependent on the microstructures of the parent alloys. The most of ligaments presented a rod-like shape due to the formation of pseudoeutectic microstructure in the melt-spun Cu 55Ag 45 and Cu 70Ag 30 alloys. For nanoporous Ag prepared from Cu 85Ag 15 alloys, the ligaments were camber-like because of the appearance of the divorced microstructures. Especially, a novel bamboo-grove-like structure could be observed at the cross-section of the nanoporous Ag ribbons. The experiment reveals that nanoporous Ag ribbons exhibited excellent enhancement of surface-enhanced Raman scattering (SERS) effect, but a slight difference existed due to the discrepancy of their morphology.

Silver nanoparticles reduce brain inflammation and related neurotoxicity through induction of H2S-synthesizing enzymes

NASA Astrophysics Data System (ADS)

Gonzalez-Carter, Daniel A.; Leo, Bey Fen; Ruenraroengsak, Pakatip; Chen, Shu; Goode, Angela E.; Theodorou, Ioannis G.; Chung, Kian Fan; Carzaniga, Raffaella; Shaffer, Milo S. P.; Dexter, David T.; Ryan, Mary P.; Porter, Alexandra E.

2017-03-01

Silver nanoparticles (AgNP) are known to penetrate into the brain and cause neuronal death. However, there is a paucity in studies examining the effect of AgNP on the resident immune cells of the brain, microglia. Given microglia are implicated in neurodegenerative disorders such as Parkinson’s disease (PD), it is important to examine how AgNPs affect microglial inflammation to fully assess AgNP neurotoxicity. In addition, understanding AgNP processing by microglia will allow better prediction of their long term bioreactivity. In the present study, the in vitro uptake and intracellular transformation of citrate-capped AgNPs by microglia, as well as their effects on microglial inflammation and related neurotoxicity were examined. Analytical microscopy demonstrated internalization and dissolution of AgNPs within microglia and formation of non-reactive silver sulphide (Ag2S) on the surface of AgNPs. Furthermore, AgNP-treatment up-regulated microglial expression of the hydrogen sulphide (H2S)-synthesizing enzyme cystathionine-γ-lyase (CSE). In addition, AgNPs showed significant anti-inflammatory effects, reducing lipopolysaccharide (LPS)-stimulated ROS, nitric oxide and TNFα production, which translated into reduced microglial toxicity towards dopaminergic neurons. Hence, the present results indicate that intracellular Ag2S formation, resulting from CSE-mediated H2S production in microglia, sequesters Ag+ ions released from AgNPs, significantly limiting their toxicity, concomitantly reducing microglial inflammation and related neurotoxicity.

Anaerobic Toxicity of Cationic Silver Nanoparticles | Science ...

EPA Pesticide Factsheets

The microbial toxicity of silver nanoparticles (AgNPs) stabilized with different capping agents was compared to that of Ag+ under anaerobic conditions. Three AgNPs were investigated: (1) negatively charged citrate-coated AgNPs (citrate-AgNPs), (2) minimally charged polyvinylpyrrolidone coated AgNPs (PVP-AgNps) and (3) positively charged branched polyethyleneimine coated AgNPs (BPEI-AgNPs). The AgNPs investigated in this experiment were similar in size (10-15 nm), spherical in shape, but varied in surface charge which ranged from highly negative to highly positive. While, at AgNPs concentrations lower than 5 mg L-1, the anaerobic decomposition process was not influenced by the presence of the nanoparticles, there was an observed impact on the diversity of the microbial community. At elevated concentrations (100 mg L-1 as silver), only the cationic BPEI-AgNPs demonstrated toxicity similar in magnitude to that of Ag+. Both citrate and PVP-AgNPs did not exhibit toxicity at the 100 mg L-1 as measured by biogas evolution. These findings further indicate the varying modes of action for nanoparticle toxicity and represent one of the few studies that evaluate end-of-life management concerns with regards to the increasing use of nanomaterials in our everyday life. These findings also highlight some of the concerns with a one size fits all approach to the evaluation of environmental health and safety concerns associated with the use of nanoparticles. The current

Enhanced electron transfer and silver-releasing suppression in Ag-AgBr/titanium-doped Al2O3 suspensions with visible-light irradiation.

PubMed

Zhou, Xuefeng; Hu, Chun; Hu, Xuexiang; Peng, Tianwei

2012-06-15

Ag-AgBr was deposited onto mesoporous alumina (MA) and titanium-doped MA by a deposition-precipitation method. The photocatalytic activity and the dissolution of Ag(+) from different catalysts were investigated during the photodegradation of 2-chlorophenol (2-CP) and phenol in ultrapure water and tap water with visible-light irradiation. With the increase in doped titanium, the Ag(+) dissolution decreased with a decrease in the photocatalytic activity. Ag-AgBr/MA-Ti1 was considered the better catalyst for practical applications because its Ag(+) dissolution was minimal (0.4 mg L(-1) in ultrapure water and 5 μg L(-1) in tap water), although its photoactivity was slightly less than that of Ag-AgBr/MA. The dissolution of Ag(+) was related to a charge-transfer process based on the study of cyclic voltammetry analyses under a variety of experimental conditions. The results suggested that several types of anions in the water, including CO(3)(2-), SO(4)(2-), and Cl(-), could act as electron donors that trap the photogenerated holes on Ag nanoparticles to facilitate electron circulation; this would decrease the release of Ag(+). Our studies indicated that the catalyst had a higher activity and stability in water purification. Copyright © 2012. Published by Elsevier B.V.

Effects of Bi Addition on the Microstructure and Mechanical Properties of Nanocrystalline Ag Coatings

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

Wang, Yuxin; Cheng, Guang; Tay, See Leng

Here in this study we investigated the effects of Bi addition on the microstructure and mechanical properties of an electrodeposited nanocrystalline Ag coating. Microstructural features were investigated with transmission electron microscopy (TEM). The results indicate that the addition of Bi introduced nanometer-scale Ag-Bi solid solution particles and more internal defects to the initial Ag microstructures. The anisotropic elastic-plastic properties of the Ag nanocrystalline coating with and without Bi addition were examined with nanoindentation experiments in conjunction with the recently-developed inverse method. The results indicate that the as-deposited nanocrystalline Ag coating contained high mechanical anisotropy. With the addition of 1 atomicmore » percent (at%) Bi, the anisotropy within Ag-Bi coating was very small, and yield strength of the nanocrystalline Ag-Bi alloy in both longitudinal and transverse directions were improved by over 100% compared to that of Ag. On the other hand, the strain-hardening exponent of Ag-Bi was reduced to 0.055 from the original 0.16 of the Ag coating. Furthermore, the addition of Bi only slightly increased the electrical resistivity of the Ag-Bi coating in comparison to Ag. Lastly, results of our study indicate that Bi addition is a promising method for improving the mechanical and physical performances of Ag coating for electrical contacts.« less

Integrating AgI/AgBr biphasic heterostructures encased by few layer h-BN with enhanced catalytic activity and stability.

PubMed

Wu, Wen; Lv, Xiaomeng; Wang, Jiaxi; Xie, Jimin

2017-06-15

Using freshly prepared water-soluble KBr crystal as facile, low-cost sacrificial template, AgBr nanocubes were synthesized through one-pot precipitation method, then navy bean shaped AgI/AgBr biphasic heterostructures were synthesized through anion-exchange reaction and encased within few-layer h-BN to obtain final product. The obtained heterostructured AgI/AgBr/h-BN composite without plasmonic noble metal nanoparticles was used as stable and high active photocatalyst for dye degradation under visible light irradiation, comparing both with self-prepared normal AgBr, AgBr cubes, AgI/AgBr navy beans and other related catalysts reported in the literature. The significant boosting of activity was attributed to the formation of AgI/AgBr interface and the coupling of few-layer h-BN, the latter of which not only effectively suppresses the reduction of silver ions but greatly enhance the charge separation. Furthermore, it was suggested that the photogenerated holes and superoxide radical were the main active species according to photoelectron chemical measurements, electron spin resonance spin-trap analysis and radical trapping experiments. Finally, the possible mechanism of enhanced photocatalytic activity and stability was discussed and proposed. The work demonstrates that engineering Ag-based semiconductor coupling with h-BN would profit the design strategy for low-cost, solar-driven photocatalysts. Copyright © 2017 Elsevier Inc. All rights reserved.

Tailoring the surface chemical bond states of the NbN films by doping Ag: Achieving hard hydrophobic surface

NASA Astrophysics Data System (ADS)

Ren, Ping; Zhang, Kan; Du, Suxuan; Meng, Qingnan; He, Xin; Wang, Shuo; Wen, Mao; Zheng, Weitao

2017-06-01

Robust hydrophobic surfaces based on ceramics capable of withstanding harsh conditions such as abrasion, erosion and high temperature, are required in a broad range of applications. The metal cations with coordinative saturation or low electronegativity are commonly chosen to achieve the intrinsically hydrophobic ceramic by reducing Lewis acidity, and thus the ceramic systems are limited. In this work, we present a different picture that robust hydrophobic surface with high hardness (≥20 GPa) can be fabricated through doping Ag atoms into intrinsically hydrophilic ceramic film NbN by reactive co-sputtering. The transition of wettability from hydrophilic to hydrophobic of Nb-Ag-N films induced by Ag doping results from the appearance of Ag2O groups on the films surfaces through self-oxidation, because Ag cations (Ag+) in Ag2O are the filled-shell (4d105S0) electronic structure with coordinative saturation that have no tendency to interact with water. The results show that surface Ag2O benefited for hydrophobicity comes from the solute Ag atoms rather than precipitate metal Ag, in which the more Ag atoms incorporated into Nb-sublattice are able to further improve the hydrophobicity, whereas the precipitation of Ag nanoclusters would worsen it. The present work opens a window for fabricating robust hydrophobic surface through tailoring surface chemical bond states by doping Ag into transition metal nitrides.

Effects of Bi Addition on the Microstructure and Mechanical Properties of Nanocrystalline Ag Coatings

DOE PAGES

Wang, Yuxin; Cheng, Guang; Tay, See Leng; ...

2017-08-10

Here in this study we investigated the effects of Bi addition on the microstructure and mechanical properties of an electrodeposited nanocrystalline Ag coating. Microstructural features were investigated with transmission electron microscopy (TEM). The results indicate that the addition of Bi introduced nanometer-scale Ag-Bi solid solution particles and more internal defects to the initial Ag microstructures. The anisotropic elastic-plastic properties of the Ag nanocrystalline coating with and without Bi addition were examined with nanoindentation experiments in conjunction with the recently-developed inverse method. The results indicate that the as-deposited nanocrystalline Ag coating contained high mechanical anisotropy. With the addition of 1 atomicmore » percent (at%) Bi, the anisotropy within Ag-Bi coating was very small, and yield strength of the nanocrystalline Ag-Bi alloy in both longitudinal and transverse directions were improved by over 100% compared to that of Ag. On the other hand, the strain-hardening exponent of Ag-Bi was reduced to 0.055 from the original 0.16 of the Ag coating. Furthermore, the addition of Bi only slightly increased the electrical resistivity of the Ag-Bi coating in comparison to Ag. Lastly, results of our study indicate that Bi addition is a promising method for improving the mechanical and physical performances of Ag coating for electrical contacts.« less

SECULAR EVOLUTION OF BINARIES NEAR MASSIVE BLACK HOLES: FORMATION OF COMPACT BINARIES, MERGER/COLLISION PRODUCTS AND G2-LIKE OBJECTS

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

Prodan, Snezana; Antonini, Fabio; Perets, Hagai B., E-mail: sprodan@cita.utoronto.ca, E-mail: antonini@cita.utoronto.ca

2015-02-01

Here we discuss the evolution of binaries around massive black holes (MBHs) in nuclear stellar clusters. We focus on their secular evolution due to the perturbation by the MBHs, while simplistically accounting for their collisional evolution. Binaries with highly inclined orbits with respect to their orbits around MBHs are strongly affected by secular processes, which periodically change their eccentricities and inclinations (e.g., Kozai-Lidov cycles). During periapsis approach, dissipative processes such as tidal friction may become highly efficient, and may lead to shrinkage of a binary orbit and even to its merger. Binaries in this environment can therefore significantly change theirmore » orbital evolution due to the MBH third-body perturbative effects. Such orbital evolution may impinge on their later stellar evolution. Here we follow the secular dynamics of such binaries and its coupling to tidal evolution, as well as the stellar evolution of such binaries on longer timescales. We find that stellar binaries in the central parts of nuclear stellar clusters (NSCs) are highly likely to evolve into eccentric and/or short-period binaries, and become strongly interacting binaries either on the main sequence (at which point they may even merge), or through their later binary stellar evolution. The central parts of NSCs therefore catalyze the formation and evolution of strongly interacting binaries, and lead to the enhanced formation of blue stragglers, X-ray binaries, gravitational wave sources, and possible supernova progenitors. Induced mergers/collisions may also lead to the formation of G2-like cloud-like objects such as the one recently observed in the Galactic center.« less

Ultrasound-assisted microwave preparation of Ag-doped CdS nanoparticles.

PubMed

Ma, Jun; Tai, Guo'an; Guo, Wanlin

2010-03-01

Ag-doped CdS nanoparticles were synthesized by an ultrasound-assisted microwave synthesis method. The X-ray diffraction patterns reveal a structural evolution from cubic to hexagonal with increasing molar ratios of Ag(+)/Cd(2+) from 0% to 5%. It shows that the Ag-doped hexagonal CdS nanoparticles are polycrystal. The X-ray photoelectron spectroscopy of the CdS nanoparticles doping with 5% Ag(+) shows that the doped Ag in CdS is metallic. Simultaneously, the characteristic Raman peaks of the CdS nanoparticles enhance with increasing Ag(+) concentrations. The photocatalytic activity of different Ag-doped samples show a reasonable change due to different ratios of Ag which doped into CdS. Copyright 2009 Elsevier B.V. All rights reserved.

Metastable Se6 as a ligand for Ag+: from isolated molecular to polymeric 1D and 2D structures.

PubMed

Aris, Damian; Beck, Johannes; Decken, Andreas; Dionne, Isabelle; Schmedt auf der Günne, Jörn; Hoffbauer, Wilfried; Köchner, Tobias; Krossing, Ingo; Passmore, Jack; Rivard, Eric; Steden, Folker; Wang, Xinping

2011-06-14

Attempts to prepare the hitherto unknown Se(6)(2+) cation by the reaction of elemental selenium and Ag[A] ([A](-) = [Sb(OTeF(5))(6)](-), [Al(OC(CF(3))(3))(4)](-)) in SO(2) led to the formation of [(OSO)Ag(Se(6))Ag(OSO)][Sb(OTeF(5))(6)](2)1 and [(OSO)(2)Ag(Se(6))Ag(OSO)(2)][Al(OC(CF(3))(3))(4)](2)2a. 1 could only be prepared by using bromine as co-oxidant, however, bulk 2b (2a with loss of SO(2)) was accessible from Ag[Al(OC(CF(3))(3))(4)] and grey Se in SO(2) (chem. analysis). The reactions of Ag[MF(6)] (M = As, Sb) and elemental selenium led to crystals of 1/∞{[Ag(Se(6))](∞)[Ag(2)(SbF(6))(3)](∞)} 3 and {1/∞[Ag(Se(6))Ag](∞)}[AsF(6)](2)4. Pure bulk 4 was best prepared by the reaction of Se(4)[AsF(6)](2), silver metal and elemental selenium. Attempts to prepare bulk 1 and 3 were unsuccessful. 1-4 were characterized by single-crystal X-ray structure determinations, 2b and 4 additionally by chemical analysis and 4 also by X-ray powder diffraction, FT-Raman and FT-IR spectroscopy. Application of the PRESTO III sequence allowed for the first time (109)Ag MAS NMR investigations of 4 as well as AgF, AgF(2), AgMF(6) and {1/∞[Ag(I(2))](∞)}[MF(6)] (M = As, Sb). Compounds 1 and 2a/b, with the very large counter ions, contain isolated [Ag(Se(6))Ag](2+) heterocubane units consisting of a Se(6) molecule bicapped by two silver cations (local D(3d) sym). 3 and 4, with the smaller anions, contain close packed stacked arrays of Se(6) rings with Ag(+) residing in octahedral holes. Each Ag(+) ion coordinates to three selenium atoms of each adjacent Se(6) ring. 4 contains [Ag(Se(6))(+)](∞) stacks additionally linked by Ag(2)(+) into a two dimensional network. 3 features a remarkable 3-dimensional [Ag(2)(SbF(6))(3)](-) anion held together by strong Sb-FAg contacts between the component Ag(+) and [SbF(6)](-) ions. The hexagonal channels formed by the [Ag(2)(SbF(6))(3)](-) anions are filled by stacks of [Ag(Se(6))(+)](∞) cations. Overall 1-4 are new members of the rare class of metal complexes of neutral main group elemental clusters, in which the main group element is positively polarized due to coordination to a metal ion. Notably, 1 to 4 include the commonly metastable Se(6) molecule as a ligand. The structure, bonding and thermodynamics of 1 to 4 were investigated with the help of quantum chemical calculations (PBE0/TZVPP and (RI-)MP2/TZVPP, in part including COSMO solvation) and Born-Fajans-Haber-cycle calculations. From an analysis of all the available data it appears that the formation of the usually metastable Se(6) molecule from grey selenium is thermodynamically driven by the coordination to the Ag(+) ions.

Influence of Biological Macromolecules and Aquatic Chemistries on the Inhibition of Nitrifying Bacteria by Silver Nanoparticles

NASA Astrophysics Data System (ADS)

Radniecki, T. S.; Anderson, J. W.; Schneider, M. C.; Stankus, D. P.; Nason, J. A.; Semprini, L.

2010-12-01

The use of silver nanoparticles (Ag-NP) as a broad spectrum biocide in a wide range of consumer goods has grown exponentially since 2006 (1), which may result in an increased release of Ag-NP into wastewater streams and ultimately the receiving bodies of water. Ammonia oxidizing bacteria (AOB) play a critical role in the global nitrogen cycle through the oxidation of ammonia (NH3) to nitrite (NO2-) and are widely considered to be the most sensitive microbial fauna in the environment being readily inhibited by contaminants, including Ag-NP (2). This research used physiological techniques in combination with physical/chemical assays to characterize the inhibition of Nitrosomonas europaea, the model AOB, by silver ions (Ag+), 3-5 nm Ag-NP, 20 nm Ag-NP and 80 nm Ag-NP under a variety of aqueous chemistries. In addition, the stability of Ag-NP suspensions was examined under a variety of aqueous chemistries including in the presences of divalent cations, chloride anions, natural organic matter (NOM), proteins (BSA) and lipopolysaccharides (alginate). Using the stable Ag-NP/test media suspensions, N. europaea was found to be extremely sensitive to Ag+, 3-5 nm Ag-NP, 20 nm Ag-NP and 80 nm Ag-NP with concentrations of 0.1, 0.12, 0.5 and 1.5 ppm, respectively, resulting in a 50% decrease in nitrification rates. The inhibition was correlated with the amount of Ag+ released into solution. It is suspected that the inhibition observed from Ag-NP exposure is caused by the liberated Ag+. The aquatic chemistry of the test media was found to have a profound influence on the stability of Ag-NP suspensions. The presence of Ag ligands (e.g. EDTA and Cl-) reduced toxicity of Ag-NP through the formation of Ag-ligand complexes with the liberated Ag+. The presence of divalent cations (e.g. Ca2+ or Mg2+) resulted in the rapid aggregation of Ag-NP leading to a decrease in Ag+ liberation and thus a decrease in N. europaea inhibition. The presence of 5 ppm NOM resulted in a highly stable Ag-NP solution even in the presence of divalent cations. This stable Ag-NP/NOM dispersion resulted in higher toxicity in the presence of divalent cations than Ag-NP alone. This work also examined the effect of the presence of biological macromolecules, including proteins and lipopolysaccharides, on Ag-NP stability and toxicity. Acknowledgements We would like to thank nanoComposix, Inc. for donating the Ag-NPs. This research was funded through an Oregon Nanoscience and Microtechnologies Institute/United State Air Force Research Labs grant # 235271B, Amend. No. 5. References (1) Wijnhoven, S.; Peijnenburg, W.; Herberts, C.; Hagens, W.; Werner, I.; Oomen, A.; Heugens, E.; Roszek, B.; Bisschops, J.; Gosens, I.; van de Meent, D.; Kekkers, S.; de Jong, W.; van Zijverden, M.; Sips, A.; Geertsma, R., Nano-silver - a review of available data and knowledge gaps in human and environmental risk assessment. Nanotoxicology 2009 1:1-30. (2) Choi, O.; Cleuenger, T. E.; Deng, B. L.; Surampalli, R. Y.; Ross, L.; Hu, Z. Q., Role of sulfide and ligand strength in controlling nanosilver toxicity. Water Research 2009 43(7):1879-1886.

Facile assembly of 3D binary colloidal crystals from soft microgel spheres.

PubMed

Liu, Yang; Guan, Ying; Zhang, Yongjun

2014-03-01

It still remains a big challenge to fabricate binary colloidal crystals (binary CCs) from hard colloidal spheres, although a lot of efforts have been made. Here, for the first time, binary CCs are assembled from soft hydrogel spheres, PNIPAM microgels, instead of hard spheres. Different from hard spheres, microgel binary CCs can be facilely fabricated by simply heating binary microgel dispersions to 37 °C and then allowing them to cool back to room temperature. The formation of highly ordered structure is indicated by the appearance of an iridescent color and a sharp Bragg diffraction peak. Compared with hard sphere binary CCs, the assembly of PNIPAM microgel binary CCs is much simpler, faster and with a higher "atom" economy. The easy formation of PNIPAM microgel binary CC is attributed to the thermosensitivity and soft nature of the PNIPAM microgel spheres. In addition, PNIPAM microgel binary CCs can respond to temperature change, and their stop band can be tuned by changing the concentration of the dispersion. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Improving geothermal power plants with a binary cycle

NASA Astrophysics Data System (ADS)

Tomarov, G. V.; Shipkov, A. A.; Sorokina, E. V.

2015-12-01

The recent development of binary geothermal technology is analyzed. General trends in the introduction of low-temperature geothermal sources are summarized. The use of single-phase low-temperature geothermal fluids in binary power plants proves possible and expedient. The benefits of power plants with a binary cycle in comparison with traditional systems are shown. The selection of the working fluid is considered, and the influence of the fluid's physicochemical properties on the design of the binary power plant is discussed. The design of binary power plants is based on the chemical composition and energy potential of the geothermal fluids and on the landscape and climatic conditions at the intended location. Experience in developing a prototype 2.5 MW Russian binary power unit at Pauzhetka geothermal power plant (Kamchatka) is outlined. Most binary systems are designed individually for a specific location. Means of improving the technology and equipment at binary geothermal power plants are identified. One option is the development of modular systems based on several binary systems that employ the heat from the working fluid at different temperatures.

Subdwarf B Stars: Tracers Of Binary Evolution

NASA Astrophysics Data System (ADS)

Morales-Rueda, L.; Maxted, P. F. L.; Marsh, T. R.

2007-08-01

Subdwarf B stars are a superb stellar population to study binary evolution. In 2001, Maxted et al. (MNRAS, 326, 1391) found that 21 out of the 36 subdwarf B stars they studied were in short period binaries. These observations inspired new theoretical work that suggests that up to 90 per cent of subdwarf B stars are in binary systems with the remaining apparently single stars being the product of merging pairs. This high binary fraction added to the fact that they are detached binaries that have not changed significantly since they came out of the common envelope, make subdwarf B stars a perfect population to study binary evolution. By comparing the observed orbital period distribution of subdwarf B stars with that obtained from population synthesis calculations we can determine fundamental parameters of binary evolution such as the common envelope ejection efficiency. Here we give an overview of the fraction of short period binaries found from different surveys as well as the most up to date orbital period distribution determined observationally. We also present results from a recent search for subdwarf B stars in long period binaries.

Contact Binaries on Their Way Towards Merging

NASA Astrophysics Data System (ADS)

Gazeas, K.

2015-07-01

Contact binaries are the most frequently observed type of eclipsing star system. They are small, cool, low-mass binaries belonging to a relatively old stellar population. They follow certain empirical relationships that closely connect a number of physical parameters with each other, largely because of constraints coming from the Roche geometry. As a result, contact binaries provide an excellent test of stellar evolution, specifically for stellar merger scenarios. Observing campaigns by many authors have led to the cataloging of thousands of contact binaries and enabled statistical studies of many of their properties. A large number of contact binaries have been found to exhibit extraordinary behavior, requiring follow-up observations to study their peculiarities in detail. For example, a doubly-eclipsing quadruple system consisting of a contact binary and a detached binary is a highly constrained system offering an excellent laboratory to test evolutionary theories for binaries. A new observing project was initiated at the University of Athens in 2012 in order to investigate the possible lower limit for the orbital period of binary systems before coalescence, prior to merging.

Survival of planets around shrinking stellar binaries

PubMed Central

Muñoz, Diego J.; Lai, Dong

2015-01-01

The discovery of transiting circumbinary planets by the Kepler mission suggests that planets can form efficiently around binary stars. None of the stellar binaries currently known to host planets has a period shorter than 7 d, despite the large number of eclipsing binaries found in the Kepler target list with periods shorter than a few days. These compact binaries are believed to have evolved from wider orbits into their current configurations via the so-called Lidov–Kozai migration mechanism, in which gravitational perturbations from a distant tertiary companion induce large-amplitude eccentricity oscillations in the binary, followed by orbital decay and circularization due to tidal dissipation in the stars. Here we explore the orbital evolution of planets around binaries undergoing orbital decay by this mechanism. We show that planets may survive and become misaligned from their host binary, or may develop erratic behavior in eccentricity, resulting in their consumption by the stars or ejection from the system as the binary decays. Our results suggest that circumbinary planets around compact binaries could still exist, and we offer predictions as to what their orbital configurations should be like. PMID:26159412

Survival of planets around shrinking stellar binaries.

PubMed

Muñoz, Diego J; Lai, Dong

2015-07-28

The discovery of transiting circumbinary planets by the Kepler mission suggests that planets can form efficiently around binary stars. None of the stellar binaries currently known to host planets has a period shorter than 7 d, despite the large number of eclipsing binaries found in the Kepler target list with periods shorter than a few days. These compact binaries are believed to have evolved from wider orbits into their current configurations via the so-called Lidov-Kozai migration mechanism, in which gravitational perturbations from a distant tertiary companion induce large-amplitude eccentricity oscillations in the binary, followed by orbital decay and circularization due to tidal dissipation in the stars. Here we explore the orbital evolution of planets around binaries undergoing orbital decay by this mechanism. We show that planets may survive and become misaligned from their host binary, or may develop erratic behavior in eccentricity, resulting in their consumption by the stars or ejection from the system as the binary decays. Our results suggest that circumbinary planets around compact binaries could still exist, and we offer predictions as to what their orbital configurations should be like.

Loss-of-function and gain-of-function phenotypes of stomatocytosis mutant RhAG F65S

PubMed Central

Stewart, Andrew K.; Shmukler, Boris E.; Vandorpe, David H.; Rivera, Alicia; Heneghan, John F.; Li, Xiaojin; Hsu, Ann; Karpatkin, Margaret; O'Neill, Allison F.; Bauer, Daniel E.; Heeney, Matthew M.; John, Kathryn; Kuypers, Frans A.; Gallagher, Patrick G.; Lux, Samuel E.; Brugnara, Carlo; Westhoff, Connie M.

2011-01-01

Four patients with overhydrated cation leak stomatocytosis (OHSt) exhibited the heterozygous RhAG missense mutation F65S. OHSt erythrocytes were osmotically fragile, with elevated Na and decreased K contents and increased cation channel-like activity. Xenopus oocytes expressing wild-type RhAG and RhAG F65S exhibited increased ouabain and bumetanide-resistant uptake of Li+ and 86Rb+, with secondarily increased 86Rb+ influx sensitive to ouabain and to bumetanide. Increased RhAG-associated 14C-methylammonium (MA) influx was severely reduced in RhAG F65S-expressing oocytes. RhAG-associated influxes of Li+, 86Rb+, and 14C-MA were pharmacologically distinct, and Li+ uptakes associated with RhAG and RhAG F65S were differentially inhibited by NH4+ and Gd3+. RhAG-expressing oocytes were acidified and depolarized by 5 mM bath NH3/NH4+, but alkalinized and depolarized by subsequent bath exposure to 5 mM methylammonium chloride (MA/MA+). RhAG F65S-expressing oocytes exhibited near-wild-type responses to NH4Cl, but MA/MA+ elicited attenuated alkalinization and strong hyperpolarization. Expression of RhAG or RhAG F65S increased steady-state cation currents unaltered by bath Li+ substitution or bath addition of 5 mM NH4Cl or MA/MA+. These oocyte studies suggest that 1) RhAG expression increases oocyte transport of NH3/NH4+ and MA/MA+; 2) RhAG F65S exhibits gain-of-function phenotypes of increased cation conductance/permeability, and loss-of-function phenotypes of decreased and modified MA/MA+ transport, and decreased NH3/NH4+-associated depolarization; and 3) RhAG transports NH3/NH4+ and MA/MA+ by distinct mechanisms, and/or the substrates elicit distinct cellular responses. Thus, RhAG F65S is a loss-of-function mutation for amine transport. The altered oocyte intracellular pH, membrane potential, and currents associated with RhAG or RhAG F65S expression may reflect distinct transport mechanisms. PMID:21849667

Longitudinal profiles of highly sensitive hepatitis B surface antigen levels: re-evaluation of HBsAg seroclearance.

PubMed

Seto, Wai-Kay; Tanaka, Yasuhito; Wong, Danny K-H; Shinkai, Noboru; Cheung, Ka-Shing; Liu, Kevin S-H; Fung, James; Lai, Ching-Lung; Yuen, Man-Fung

2016-05-01

Serologic profiles after hepatitis B surface antigen (HBsAg) seroclearance in chronic hepatitis B (CHB) have not been well-studied. We employed a highly sensitive HBsAg (hs-HBsAg) assay (lower detection limit 0.5 mIU/ml), 100 times more sensitive than conventional HBsAg measurements. CHB patients achieving HBsAg seroclearance defined by conventional assays were followed up for serum hs-HBsAg, HBV DNA and antibody to HBsAg (anti-HBs) levels at 0 months, 6-12 months and 3-5 years after HBsAg seroclearance. Factors associated with hs-HBsAg detectability were determined. One hundred and nine patients were recruited; 94 (86.2%) were followed up to years 3-5; and 25 patients (22.9%) were on nucleoside analogue therapy for a median duration of 6.0 (range 1.5-12.7) years before HBsAg seroclearance. Detectable hs-HBsAg was noted in 88 (80.7%), 60 (55.0%) and 20 (21.3%) patients at 0 months, 6-12 months and 3-5 years respectively. At years 3-5, genotype B patients, when compared to genotype C patients, had a higher anti-HBs positive rate (63.2% and 41.1% respectively, P = 0.036). Serum anti-HBs positivity, when compared to persistent anti-HBs negativity, was associated with a lower rate of hs-HBsAg detection (7.4% and 40% respectively, P < 0.001). Multivariate analysis showed anti-HBs negativity at years 3-5 to be independently associated with persistently positive hs-HBsAg (P = 0.007, odds ratio 7.1, 95% confidence interval 1.7-29.3). Serum hs-HBsAg could detect HBsAg presence in a substantial proportion of CHB after HBsAg seroclearance defined by conventional assays, especially among anti-HBs negative individuals. Serum hs-HBsAg could potentially assist differentiating HBsAg-negative CHB from individuals with only past HBV exposure without carrier state. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Stability of single dispersed silver nanoparticles in natural and synthetic freshwaters: Effects of dissolved oxygen.

PubMed

Zou, Xiaoyan; Li, Penghui; Lou, Jie; Fu, Xiaoyan; Zhang, Hongwu

2017-11-01

Silver nanoparticles (AgNPs) are increasingly used in various commercial products. This increased use raises ecological concerns because of the large release of AgNPs into the environment. Once released, the local water chemistry has the potential to influence the environmental fates and behaviors of AgNPs. The impacts of dissolved oxygen and natural organic matter (NOM) on the dissolution and stability of AgNPs were investigated in synthetic and natural freshwaters for 7 days. In synthetic freshwater, the aggregation of AgNPs occurred due to the compression of the electric double layer, accompanied by the dissolution of AgNPs. However, once oxygen was removed, the highest dissolved Ag (Ag dis ) concentration decreased from 356.5 μg/L to 272.1 μg/L, the pH of the AgNP suspensions increased from less than 7.6 to more than 8.4, and AgNPs were regenerated by the reduction of released Ag + by citrate. The addition of NOM mitigated aggregation, inhibited oxidative dissolution and induced the transformation of AgNPs into Ag 2 S due to the formation of NOM-adsorbed layers, the reduction of Ag + by NOM, and the high affinity of sulfur-enriched species in NOM for Ag. Likewise, in oxygen-depleted natural freshwaters, the inhibition of oxidative dissolution was obtained in comparison with oxygenated freshwaters, showing a decrease in the maximum Ag dis concentration from 137.6 and 57.0 μg/L to 83.3 and 42.4 μg/L from two natural freshwater sites. Our results suggested that aggregation and dissolution of AgNPs in aquatic environments depend on the chemical composition, where oxygen-depleted freshwaters more significantly increase the colloidal stability. In comparison with oxic conditions, anoxic conditions were more favorable to the regeneration of AgNPs by reducing species (e.g., citrate and NOM) and enhanced the stability of nanoparticles. This indicates that some AgNPs will be more stable for long periods in oxygen-deprived freshwaters, and pose more serious environmental risks than that in oxygenated freshwaters. Copyright © 2017 Elsevier Ltd. All rights reserved.

Facile solvothermal synthesis of cube-like Ag@AgCl: a highly efficient visible light photocatalyst

NASA Astrophysics Data System (ADS)

Han, Lei; Wang, Ping; Zhu, Chengzhou; Zhai, Yueming; Dong, Shaojun

2011-07-01

In this paper, a stable and highly efficient plasmonic photocatalyst, Ag@AgCl, with cube-like morphology, has been successfully prepared via a simple hydrothermal method. Using methylene dichloride as chlorine source in the synthesis can efficiently control the morphology of Ag@AgCl, due to the low release rate of chloride ions. Scanning electron microscopy (SEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectra were used to characterize the obtained product. The photocatalytic activity of the obtained product was evaluated by the photodegradation of methyl orange (MO) under visible light irradiation, and it was found, interestingly, that Ag@AgCl exhibits high visible light photocatalytic activity and good stability.In this paper, a stable and highly efficient plasmonic photocatalyst, Ag@AgCl, with cube-like morphology, has been successfully prepared via a simple hydrothermal method. Using methylene dichloride as chlorine source in the synthesis can efficiently control the morphology of Ag@AgCl, due to the low release rate of chloride ions. Scanning electron microscopy (SEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectra were used to characterize the obtained product. The photocatalytic activity of the obtained product was evaluated by the photodegradation of methyl orange (MO) under visible light irradiation, and it was found, interestingly, that Ag@AgCl exhibits high visible light photocatalytic activity and good stability. Electronic supplementary information (ESI) available: SEM images of the AgCl samples synthesized by changing the addition amount of PVP and AgNO3. See DOI: 10.1039/c1nr10247h

Thidiazuron-enhanced biosynthesis and antimicrobial efficacy of silver nanoparticles via improving phytochemical reducing potential in callus culture of Linum usitatissimum L.

PubMed Central

Anjum, Sumaira; Abbasi, Bilal Haider

2016-01-01

Green synthesis of silver nanoparticles (AgNPs) by using plants is an emerging class of nanobiotechnology. It revolutionizes all domains of medical sciences by synthesizing chemical-free AgNPs for various biomedical applications. In this report, AgNPs were successfully synthesized by using whole plant extract (WPE) and thidiazuron-induced callus extract (CE) of Linum usitatissimum. The phytochemical analysis revealed that the total phenolic and flavonoid contents were higher in CE than that in WPE. Ultraviolet-visible spectroscopy of synthesized AgNPs showed a characteristic surface plasmon band in the range of 410–426 nm. Bioreduction of CE-mediated AgNPs was completed in a shorter time than that of WPE-mediated AgNPs. Scanning electron microscopy showed that both types of synthesized AgNPs were spherical in shape, but CE-mediated AgNPs were smaller in size (19–24 nm) and more scattered in distribution than that of WPE-mediated AgNPs (49–54 nm). X-ray diffraction analysis confirmed crystalline nature (face-centered cubic) of both types of AgNPs. Fourier-transform infrared spectroscopy revealed that the polyphenols and flavonoids were mainly responsible for reduction and capping of synthesized AgNPs. Energy dispersive X-ray analysis further confirmed the successful synthesis of AgNPs. Moreover, the synthesized AgNPs were found to be stable over months with no change in the surface plasmon bands. More importantly, CE-mediated AgNPs displayed significantly higher bactericidal activity against multiple drug-resistant human pathogens than WPE-mediated AgNPs. The present work highlighted the potent role of thidiazuron in in vitro-derived cultures for enhanced biosynthesis of chemical-free AgNPs, which can be used as nanomedicines in many biomedical applications. PMID:26955271

One-pot, facile fabrication of a Ag3PO4-based ternary Z-scheme photocatalyst with excellent visible-light photoactivity and anti-photocorrosion performance

NASA Astrophysics Data System (ADS)

Xie, Mingyuan; Zhang, Tailiang

2018-04-01

Ag3PO4 can-not be widely used as an efficient photocatalyst in practical applications because of its susceptibility to photocorrosion. In this study, a novel, ternary Z-scheme photocatalytic system containing graphene oxide (GO), Ag3PO4 and SnS2 was fabricated by a one-pot, mild, in-situ precipitation method successfully. Using Rhodamine B (RhB) as the target of elimination, GO/Ag3PO4/SnS2 exhibited outstanding photocatalytic and anti-photocorrosion properties compared with those of Ag3PO4, Ag3PO4/SnS2 and GO/Ag3PO4. RhB was thoroughly degraded over the optimized GO/Ag3PO4/SnS2 nanocomposite after only 15 min under visible-light irradiation; this result is approximately 2.14, 3.33 and 5.83 times faster than that of GO/Ag3PO4, Ag3PO4/SnS2 and Ag3PO4, respectively. After three reuses, the photocatalytic activity of the ternary composite slightly decreased but remained 2.36, 4.08 and 12.70 times higher than those of the reused GO/Ag3PO4, Ag3PO4/SnS2 and Ag3PO4, respectively. In this system, the efficient separation and migration of the photoinduced current carriers in Ag3PO4 was realized through a double Z-scheme electron-transfer mechanism in which the GO nanosheets acted as the photocatalyst and electron mediator, thereby enhancing the photoactivity and stability of Ag3PO4. The present study provides a new perspective for enhancing photocatalytic and anti-photocorrosion performances in perishable photocatalysts for organic sewage and other environmental contamination treatments.

In situ green synthesis of antimicrobial carboxymethyl chitosan-nanosilver hybrids with controlled silver release.

PubMed

Huang, Siqi; Yu, Zhiming; Zhang, Yang; Qi, Chusheng; Zhang, Shifeng

2017-01-01

In order to fabricate antimicrobial carboxymethyl chitosan-nanosilver (CMC-Ag) hybrids with controlled silver release, this study demonstrated comparable formation via three synthetic protocols: 1) carboxymethyl chitosan (CMC) and glucose (adding glucose after AgNO 3 ), 2) CMC and glucose (adding glucose before AgNO 3 ), and 3) CMC only. Under principles of green chemistry, the synthesis was conducted in an aqueous medium exposed to microwave irradiation for 10 minutes with nontoxic chemicals. The structure and formation mechanisms of the three CMC-Ag hybrids were explored using X-ray diffraction, ultraviolet-visible spectroscopy, transmission electron microscopy, and Fourier-transform infrared analyses. Additionally, antimicrobial activity and in vitro silver release of the three synthesized hybrids were investigated in detail. The results revealed that a large number of stable, uniform, and small silver nanoparticles (AgNPs) were synthesized in situ on CMC chains via protocol 1. AgNPs were well dispersed with narrow size distribution in the range of 6-20 nm, with mean diameter only 12.22±2.57 nm. The addition of glucose resulted in greater AgNP synthesis. The order of addition of glucose and AgNO 3 significantly affected particle size and size distribution of AgNPs. Compared to CMC alone and commercially available AgNPs, the antimicrobial activities of three hybrids were significantly improved. Of the three hybrids, CMC-Ag1 synthesized via protocol 1 exhibited better antimicrobial activity than CMC-Ag2 and CMC-Ag3, and showed more effective inhibition of Staphylococcus aureus than Escherichia coli . Due to strong coordination and electrostatic interactions between CMC and silver and good steric protection provided by CMC, CMC-Ag1 displayed stable and continuous silver release and better performance in retaining silver for prolonged periods than CMC-Ag2 and CMC-Ag3.

Enhancing the photoelectrochemical response of TiO2 nanotubes through their nanodecoration by pulsed-laser-deposited Ag nanoparticles

NASA Astrophysics Data System (ADS)

Trabelsi, K.; Hajjaji, A.; Gaidi, M.; Bessais, B.; El Khakani, M. A.

2017-08-01

We report on the pulsed laser deposition (PLD) based nanodecoration of titanium dioxide (TiO2) nanotube arrays (NTAs) by Ag nanoparticles (NPs). We focus here on the investigation of the effect of the number of laser ablation pulses (NLP) of the silver target on both the average size of the Ag-NPs and the photoelectrochemical conversion efficiency of the Ag-NP decorated TiO2-NT based photoanodes. By varying the NLP, we were able to not only control the size of the PLD-deposited Ag nanoparticles from 20 to ˜50 nm, but also to increase concomitantly the surface coverage of the TiO2 NTAs by Ag-NPs. The red-shifting of the surface plasmon resonance peak of the PLD-deposited Ag-NPs deposited onto quartz substrates confirmed the increase of their size as the NLP is increased from 500 to 10 000. By investigating the photo-electrochemical properties of Ag-NP decorated TiO2-NTAs, by means of linear sweep cyclic voltammetry under UV-Vis illumination, we found that the generated photocurrent is sensitive to the size of the Ag-NPs and reaches a maximum value at NLP =500 (i.e.,; Ag-NP size of ˜20 nm). For NLP = 500, the photoconversion efficiency of the Ag-NP decorated TiO2-NTAs is shown to reach a maximum of 4.5% (at 0.5 V vs Ag/AgCl). The photocurrent enhancement of Ag-NP decorated TiO2-NTAs is believed to result from the additional light harvesting enabled by the ability of Ag-NPs to absorb visible irradiation caused by various localized surface plasmon resonances, which in turn depend on the size and interdistance of the Ag nanoparticles.

Silver-Doped Calcium Phosphate Bone Cements with Antibacterial Properties

PubMed Central

Rau, J. V.; Fosca, M.; Graziani, V.; Egorov, A. A.; Zobkov, Yu. V.; Fedotov, A. Yu.; Ortenzi, M.; Caminiti, R.; Baranchikov, A. E.; Komlev, V. S.

2016-01-01

Calcium phosphate bone cements (CPCs) with antibacterial properties are demanded for clinical applications. In this study, we demonstrated the use of a relatively simple processing route based on preparation of silver-doped CPCs (CPCs-Ag) through the preparation of solid dispersed active powder phase. Real-time monitoring of structural transformations and kinetics of several CPCs-Ag formulations (Ag = 0 wt %, 0.6 wt % and 1.0 wt %) was performed by the Energy Dispersive X-ray Diffraction technique. The partial conversion of β-tricalcium phosphate (TCP) phase into the dicalcium phosphate dihydrate (DCPD) took place in all the investigated cement systems. In the pristine cement powders, Ag in its metallic form was found, whereas for CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt % cements, CaAg(PO3)3 was detected and Ag (met.) was no longer present. The CPC-Ag 0 wt % cement exhibited a compressive strength of 6.5 ± 1.0 MPa, whereas for the doped cements (CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt %) the reduced values of the compressive strength 4.0 ± 1.0 and 1.5 ± 1.0 MPa, respectively, were detected. Silver-ion release from CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt % cements, measured by the Atomic Emission Spectroscopy, corresponds to the average values of 25 µg/L and 43 µg/L, respectively, rising a plateau after 15 days. The results of the antibacterial test proved the inhibitory effect towards pathogenic Escherichia coli for both CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt % cements, better performances being observed for the cement with a higher Ag-content. PMID:27096874

Thidiazuron-enhanced biosynthesis and antimicrobial efficacy of silver nanoparticles via improving phytochemical reducing potential in callus culture of Linum usitatissimum L.

PubMed

Anjum, Sumaira; Abbasi, Bilal Haider

2016-01-01

Green synthesis of silver nanoparticles (AgNPs) by using plants is an emerging class of nanobiotechnology. It revolutionizes all domains of medical sciences by synthesizing chemical-free AgNPs for various biomedical applications. In this report, AgNPs were successfully synthesized by using whole plant extract (WPE) and thidiazuron-induced callus extract (CE) of Linum usitatissimum. The phytochemical analysis revealed that the total phenolic and flavonoid contents were higher in CE than that in WPE. Ultraviolet-visible spectroscopy of synthesized AgNPs showed a characteristic surface plasmon band in the range of 410-426 nm. Bioreduction of CE-mediated AgNPs was completed in a shorter time than that of WPE-mediated AgNPs. Scanning electron microscopy showed that both types of synthesized AgNPs were spherical in shape, but CE-mediated AgNPs were smaller in size (19-24 nm) and more scattered in distribution than that of WPE-mediated AgNPs (49-54 nm). X-ray diffraction analysis confirmed crystalline nature (face-centered cubic) of both types of AgNPs. Fourier-transform infrared spectroscopy revealed that the polyphenols and flavonoids were mainly responsible for reduction and capping of synthesized AgNPs. Energy dispersive X-ray analysis further confirmed the successful synthesis of AgNPs. Moreover, the synthesized AgNPs were found to be stable over months with no change in the surface plasmon bands. More importantly, CE-mediated AgNPs displayed significantly higher bactericidal activity against multiple drug-resistant human pathogens than WPE-mediated AgNPs. The present work highlighted the potent role of thidiazuron in in vitro-derived cultures for enhanced biosynthesis of chemical-free AgNPs, which can be used as nanomedicines in many biomedical applications.

Size-selective reactivity of subnanometer Ag 4 and Ag 16 clusters on a TiO 2 surface

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

Chen, Po-Tuan; Tyo, Eric C.; Hayashi, Michitoshi

Size-selected Ag 4 and Ag 16 clusters on a titania surface have been studied for their potential in CO oxidation using theoretical calculations and X-ray absorption near edge spectroscopy. The first peak at the measured Ag K-edge of Ag 16@TiO 2 is more prominent in air than in carbon monoxide environment, but no variation was found between the spectra of Ag 4@TiO 2 in air and in carbon monoxide environments. Density functional theory calculations show a preference for molecular oxygen adsorption for Ag 4@TiO 2 and that for a dissociative one on Ag 16@TiO 2, while carbon monoxide reactions withmore » adsorbed oxygen reduced the Ag 16@TiO 2 cluster. The dissociated oxygen atoms increased the oxidation state of Ag 16 cluster and resulted in the prominent first peak in Ag K-edge spectrum in quasi-particle theory calculations, with the subsequent carbon monoxide oxidation reversing the character of Ag K-edge spectrum associated with the reduction of the cluster. Finally, the results provide insight into the size selectivity of supported subnanometer silver clusters in their interactions with oxygen and carbon monoxide, with implications on the cluster catalytic properties in oxidative reactions.« less

New frontiers in water purification: highly stable amphopolycarboxyglycinate-stabilized Ag-AgCl nanocomposite and its newly discovered potential

NASA Astrophysics Data System (ADS)

Krutyakov, Yurii A.; Zherebin, Pavel M.; Kudrinskiy, Alexey A.; Zubavichus, Yan V.; Presniakov, Mikhail Yu; Yapryntsev, Alexey D.; Karabtseva, Anastasia V.; Mikhaylov, Dmitry M.; Lisichkin, Georgii V.

2016-09-01

A simple synthetic procedure for high-stable dispersions of porous composite Ag/AgCl nanoparticles stabilized with amphoteric surfactant sodium tallow amphopolycarboxyglycinate has been proposed for the first time. The prepared samples were characterized by UV-vis spectroscopy, x-ray powder diffraction (XRD), x-ray photoelectron spectroscopy, small area electron diffraction (SAED), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and electron probe micro-analysis. In addition, measurements (carried out at the Kurchatov synchrotron radiation source stations) of the Ag K-edge extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge structure (XANES) spectra and XRD of the prepared nanoparticles have been performed. The obtained results suggest that small-sized Ag clusters are homogeneously distributed in the mass of the AgCl nanoparticle (~80 nm) formed during the synthesis. The Ag/AgCl dispersion demonstrates photocatalytic activity (with respect to methyl orange) and high bactericidal activity against E. coli. This activity is superior to the activity of both Ag and AgCl nanoparticles stabilized by the same surfactant. Thus, porous composite Ag/AgCl nanoparticles can be used as a multifunctional agent that is able to remove both pollutants and bacterium from water.

Sequestration of Ag(I) from aqueous solution as Ag(0) nanostructures by nanoscale zero valent iron (nZVI)

NASA Astrophysics Data System (ADS)

Zhang, Yalei; Yan, Jing; Dai, Chaomeng; Li, Yuting; Zhu, Yan; Zhou, Xuefei

2015-11-01

This study investigates the application of nanoparticle zero valent iron (nZVI) to sequester Ag(I) as Ag(0) nanostructures from aqueous solution. Batch experiments were performed with nZVI exposed to aqueous Ag(I) to investigate the effects of environmental parameters, including nZVI dose, temperature and pH. High temperature facilitates Ag(I) sequestration, and the rate constants are determined to be 0.02, 0.12, and 0.31 mg L/m2 at 30, 50, and 60 °C, respectively. Ag(I) sequestration was adversely affected by adding nitric acid to the solution due to significant acid washing, decreasing the available nZVI active sites. Characterization techniques including TEM, XRD, and HR-XPS revealed that nZVI is oxidized to lepidocrocite and magnetite/maghemite and confirmed the formation of nanocrystalline silver. HR-XPS analysis indicated that Ag2O forms rapidly as an intermediate due to Ag(I) adsorption onto the FeOOH layer. The Ag(0) nanostructures that are formed are fractal, spherical, and dendritic or rod-like, respectively, in morphology by FE-TEM images at different Ag/Fe mass ratios. A general reaction model for the interaction Ag(I) with nZVI is proposed. Our results suggest that nZVI is effective for Ag(I) removal.

Size-selective reactivity of subnanometer Ag 4 and Ag 16 clusters on a TiO 2 surface

DOE PAGES

Chen, Po-Tuan; Tyo, Eric C.; Hayashi, Michitoshi; ...

2017-03-08

Size-selected Ag 4 and Ag 16 clusters on a titania surface have been studied for their potential in CO oxidation using theoretical calculations and X-ray absorption near edge spectroscopy. The first peak at the measured Ag K-edge of Ag 16@TiO 2 is more prominent in air than in carbon monoxide environment, but no variation was found between the spectra of Ag 4@TiO 2 in air and in carbon monoxide environments. Density functional theory calculations show a preference for molecular oxygen adsorption for Ag 4@TiO 2 and that for a dissociative one on Ag 16@TiO 2, while carbon monoxide reactions withmore » adsorbed oxygen reduced the Ag 16@TiO 2 cluster. The dissociated oxygen atoms increased the oxidation state of Ag 16 cluster and resulted in the prominent first peak in Ag K-edge spectrum in quasi-particle theory calculations, with the subsequent carbon monoxide oxidation reversing the character of Ag K-edge spectrum associated with the reduction of the cluster. Finally, the results provide insight into the size selectivity of supported subnanometer silver clusters in their interactions with oxygen and carbon monoxide, with implications on the cluster catalytic properties in oxidative reactions.« less

Enhanced photocatalytic performances and magnetic recovery capacity of visible-light-driven Z-scheme ZnFe2O4/AgBr/Ag photocatalyst

NASA Astrophysics Data System (ADS)

He, Jie; Cheng, Yahui; Wang, Tianzhao; Feng, Deqiang; Zheng, Lingcheng; Shao, Dawei; Wang, Weichao; Wang, Weihua; Lu, Feng; Dong, Hong; Zheng, Rongkun; Liu, Hui

2018-05-01

High efficiency, high stability and easy recovery are three key factors for practical photocatalysts. Z-scheme heterostructure is one of the most promising photocatalytic systems to meet all above requirements. However, efficient Z-scheme photocatalysts which could absorb visible light are still few and difficult to implement at present. In this work, the composite photocatalysts ZnFe2O4/AgBr/Ag were prepared through a two-step method. A ∼92% photodegradation rate on methyl orange was observed within 30 min under visible light, which is much better than that of individual ZnFe2O4 or AgBr/Ag. The stability was also greatly improved compared with AgBr/Ag. The increased performance is resulted from the suitable band alignment of ZnFe2O4 and AgBr, and it is defined as Z-scheme mechanism which was demonstrated by detecting active species and electrochemical impedance spectroscopy. Besides, ZnFe2O4/AgBr/Ag is ferromagnetic and can be recycled by magnet. These results show that ZnFe2O4/AgBr/Ag is a potential magnetically recyclable photocatalyst which can be driven by visible light.

Gut Dysbiosis and Neurobehavioral Alterations in Rats Exposed to Silver Nanoparticles.

PubMed

Javurek, Angela B; Suresh, Dhananjay; Spollen, William G; Hart, Marcia L; Hansen, Sarah A; Ellersieck, Mark R; Bivens, Nathan J; Givan, Scott A; Upendran, Anandhi; Kannan, Raghuraman; Rosenfeld, Cheryl S

2017-06-06

Due to their antimicrobial properties, silver nanoparticles (AgNPs) are being used in non-edible and edible consumer products. It is not clear though if exposure to these chemicals can exert toxic effects on the host and gut microbiome. Conflicting studies have been reported on whether AgNPs result in gut dysbiosis and other changes within the host. We sought to examine whether exposure of Sprague-Dawley male rats for two weeks to different shapes of AgNPs, cube (AgNC) and sphere (AgNS) affects gut microbiota, select behaviors, and induces histopathological changes in the gastrointestinal system and brain. In the elevated plus maze (EPM), AgNS-exposed rats showed greater number of entries into closed arms and center compared to controls and those exposed to AgNC. AgNS and AgNC treated groups had select reductions in gut microbiota relative to controls. Clostridium spp., Bacteroides uniformis, Christensenellaceae, and Coprococcus eutactus were decreased in AgNC exposed group, whereas, Oscillospira spp., Dehalobacterium spp., Peptococcaeceae, Corynebacterium spp., Aggregatibacter pneumotropica were reduced in AgNS exposed group. Bacterial reductions correlated with select behavioral changes measured in the EPM. No significant histopathological changes were evident in the gastrointestinal system or brain. Findings suggest short-term exposure to AgNS or AgNC can lead to behavioral and gut microbiome changes.

Spontaneous and Selective Nanowelding of Silver Nanowires by Electrochemical Ostwald Ripening and High Electrostatic Potential at the Junctions for High-Performance Stretchable Transparent Electrodes.

PubMed

Lee, Hyo-Ju; Oh, Semi; Cho, Ki-Yeop; Jeong, Woo-Lim; Lee, Dong-Seon; Park, Seong-Ju

2018-04-25

Metal nanowires have been gaining increasing attention as the most promising stretchable transparent electrodes for emerging field of stretchable optoelectronic devices. Nanowelding technology is a major challenge in the fabrication of metal nanowire networks because the optoelectronic performances of metal nanowire networks are mostly limited by the high junction resistance between nanowires. We demonstrate the spontaneous and selective welding of Ag nanowires (AgNWs) by Ag solders via an electrochemical Ostwald ripening process and high electrostatic potential at the junctions of AgNWs. The AgNWs were welded by depositing Ag nanoparticles (AgNPs) on the conducting substrate and then exposing them to water at room temperature. The AgNPs were spontaneously dissolved in water to form Ag + ions, which were then reduced to single-crystal Ag solders selectively at the junctions of the AgNWs. Hence, the welded AgNWs showed higher optoelectronic and stretchable performance compared to that of as-formed AgNWs. These results indicate that electrochemical Ostwald ripening-based welding can be used as a promising method for high-performance metal nanowire electrodes in various next-generation devices such as stretchable solar cells, stretchable displays, organic light-emitting diodes, and skin sensors.

Nanoscale coupling of photons to vibrational excitation of Ag nanoparticle 2D array studied by scanning tunneling microscope light emission spectroscopy.

PubMed

Katano, Satoshi; Toma, Koji; Toma, Mana; Tamada, Kaoru; Uehara, Yoichi

2010-11-28

Scanning tunneling microscope light emission (STM-LE) spectroscopy has been utilized to elucidate the luminescence phenomena of Ag nanoparticles capped with myristate (myristate-capped AgNP) and 2-methyl-1-propanethiolate (C(4)S-capped AgNP) on the dodecanethiol-precovered Au substrate. The STM imaging revealed that myristate-capped AgNPs form an ordered hexagonal array whereas C(4)S-capped AgNPs show imperfect ordering, indicating that a shorter alkyl chain of C(4)S-capped AgNP is not sufficient to form rigid interdigitation. It should be noted that such a nanoparticle ordering affects the luminescence properties of the Ag nanoparticle. We found that the STM-LE is only detected from the Ag nanoparticles forming the two-dimensional superlattice. This indicates that the STM-LE of the Ag nanoparticle is radiated via the collective excitation of the local surface plasmon resonance (LSPR) spread over the Ag nanoparticles. Note that the STM-LE spectra of the Ag nanoparticles exhibit spike-like peaks superimposed on the broad light emission peak. Using Raman spectroscopy, we concluded that the spike-like structure appearing in the STM-LE spectra is associated with the vibrational excitation of the molecule embedded between Ag nanoparticles.

Stabilizing subnanometer Ag(0) nanoclusters by thiolate and diphosphine ligands and their crystal structures

NASA Astrophysics Data System (ADS)

Yang, Huayan; Wang, Yu; Zheng, Nanfeng

2013-03-01

The combined use of thiolate and diphosphine as surface ligands helps to stabilize subnanometer Ag(0) nanoclusters, resulting in the successful crystallization of two Ag(0)-containing nanoclusters (Ag16 and Ag32) for X-ray single crystal analysis. Both clusters have core-shell structures with Ag86+ and Ag2212+ as their cores, which are not simply either fragments of face-centered cubic metals or their five-fold twinned counterparts. The clusters display UV-Vis absorption spectra consisting of molecule-like optical transitions.The combined use of thiolate and diphosphine as surface ligands helps to stabilize subnanometer Ag(0) nanoclusters, resulting in the successful crystallization of two Ag(0)-containing nanoclusters (Ag16 and Ag32) for X-ray single crystal analysis. Both clusters have core-shell structures with Ag86+ and Ag2212+ as their cores, which are not simply either fragments of face-centered cubic metals or their five-fold twinned counterparts. The clusters display UV-Vis absorption spectra consisting of molecule-like optical transitions. Electronic supplementary information (ESI) available: Experimental details, more pictures of the structure and XPS spectra of the clusters. CCDC 916463 and 916464. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c3nr34328f

Aniline chlorination by in situ formed Ag-Cl complexes under simulated solar light irradiation.

PubMed

Hu, Xuefeng; Wang, Xiaowen; Dong, Liuliu; Chang, Fei; Luo, Yongming

2015-01-01

Ag speciation in a chloride medium was dependent upon the Cl/Ag ratio after releasing into surface water. In this study, the photoreaction of in situ formed Ag-Cl species and their effects on aniline photochlorination were systematically investigated. Our results suggested that formation of chloroaniline was strongly relevant to the Cl/Ag ratio and could be interpreted using the thermodynamically expected speciation of Ag in the presence of Cl-. AgCl was the main species responsible for the photochlorination of aniline. Both photoinduced hole and •OH drove the oxidation of Cl- to radical •Cl, which promoted the chlorination of aniline. Ag0 formation was observed from the surface plasmon resonance absorption during AgCl photoreaction. This study revealed that Ag+ released into Cl--containing water may result in the formation of chlorinated intermediates of organic compounds under solar light irradiation.

Electrolytic Migration of Ag-Pd Alloy Wires with Various Pd Contents

NASA Astrophysics Data System (ADS)

Lin, Yan-Cheng; Chen, Chun-Hao; He, Yu-Zhen; Chen, Sheng-Chi; Chuang, Tung-Han

2018-07-01

During Ag ion migration in an aqueous water drop covering a pair of parallel Ag-Pd wires under current stressing, hydrogen bubbles form first from the cathode, followed by the appearance of pure Ag dendrites on the cathodic wire. In this study, Ag dendrites with a diameter of 0.2-0.4 μm grew toward the anodic wire. The growth rate ( v) of these dendrites decreased with the Pd content ( c) with a linear relationship of: v = 10.02 - 0.43 c . Accompanying the growth of pure Ag dendrites was the formation of a continuous layer of crystallographic Ag2O particles on the surface of the anodic wire. The deposition of such insulating Ag2O products did not prevent the contact of Ag dendrites with the anodic Ag-Pd wire or the short circuit of the wire couple.

Surface-supported Ag islands stabilized by a quantum size effect: Their interaction with small molecules relevant to ethylene epoxidation

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

Shao, Dahai

2013-05-15

This dissertation focuses on how QSE-stabilized, surface-supported Ag nanoclusters will interact with ethylene or oxygen. Experiments are performed to determine whether the QSE-mediated Ag islands react differently toward adsorption of ethylene or oxygen, or whether the adsorption of these small molecules will affect the QSE-mediated stability of Ag islands. Studies of the interaction of oxygen with Ag/Si(111)-7×7 were previously reported, but these studies were performed at a low Ag coverage where 3D Ag islands were not formed. So the study of such a system at a higher Ag coverage will be a subject of this work. The interaction of ethylenemore » with Ag/Si(111)-7×7, as well as the interaction of oxygen with Ag/NiAl(110) are also important parts of this study.« less

Electrolytic Migration of Ag-Pd Alloy Wires with Various Pd Contents

NASA Astrophysics Data System (ADS)

Lin, Yan-Cheng; Chen, Chun-Hao; He, Yu-Zhen; Chen, Sheng-Chi; Chuang, Tung-Han

2018-03-01

During Ag ion migration in an aqueous water drop covering a pair of parallel Ag-Pd wires under current stressing, hydrogen bubbles form first from the cathode, followed by the appearance of pure Ag dendrites on the cathodic wire. In this study, Ag dendrites with a diameter of 0.2-0.4 μm grew toward the anodic wire. The growth rate (v) of these dendrites decreased with the Pd content (c) with a linear relationship of: v = 10.02 - 0.43 c . Accompanying the growth of pure Ag dendrites was the formation of a continuous layer of crystallographic Ag2O particles on the surface of the anodic wire. The deposition of such insulating Ag2O products did not prevent the contact of Ag dendrites with the anodic Ag-Pd wire or the short circuit of the wire couple.

Eclipsing Stellar Binaries in the Galactic Center

NASA Astrophysics Data System (ADS)

Li, Gongjie; Ginsburg, Idan; Naoz, Smadar; Loeb, Abraham

2017-12-01

Compact stellar binaries are expected to survive in the dense environment of the Galactic center. The stable binaries may undergo Kozai–Lidov oscillations due to perturbations from the central supermassive black hole (Sgr A*), yet the general relativistic precession can suppress the Kozai–Lidov oscillations and keep the stellar binaries from merging. However, it is challenging to resolve the binary sources and distinguish them from single stars. The close separations of the stable binaries allow higher eclipse probabilities. Here, we consider the massive star SO-2 as an example and calculate the probability of detecting eclipses, assuming it is a binary. We find that the eclipse probability is ∼30%–50%, reaching higher values when the stellar binary is more eccentric or highly inclined relative to its orbit around Sgr A*.

Pulsars in binary systems: probing binary stellar evolution and general relativity.

PubMed

Stairs, Ingrid H

2004-04-23

Radio pulsars in binary orbits often have short millisecond spin periods as a result of mass transfer from their companion stars. They therefore act as very precise, stable, moving clocks that allow us to investigate a large set of otherwise inaccessible astrophysical problems. The orbital parameters derived from high-precision binary pulsar timing provide constraints on binary evolution, characteristics of the binary pulsar population, and the masses of neutron stars with different mass-transfer histories. These binary systems also test gravitational theories, setting strong limits on deviations from general relativity. Surveys for new pulsars yield new binary systems that increase our understanding of all these fields and may open up whole new areas of physics, as most spectacularly evidenced by the recent discovery of an extremely relativistic double-pulsar system.

Chimeric rabbit/human Fab antibodies against the hepatitis Be-antigen and their potential applications in assays, characterization, and therapy.

PubMed

Zhuang, Xiaolei; Watts, Norman R; Palmer, Ira W; Kaufman, Joshua D; Dearborn, Altaira D; Trenbeath, Joni L; Eren, Elif; Steven, Alasdair C; Rader, Christoph; Wingfield, Paul T

2017-10-06

Hepatitis B virus (HBV) infection afflicts millions worldwide, causing cirrhosis and liver cancer. HBV e-antigen (HBeAg), a clinical marker for disease severity, is a soluble variant of the viral capsid protein. HBeAg is not required for viral replication but is implicated in establishing immune tolerance and chronic infection. The structure of recombinant e-antigen (rHBeAg) was recently determined, yet to date, the exact nature and quantitation of HBeAg still remain uncertain. Here, to further characterize HBeAg, we used phage display to produce a panel of chimeric rabbit/human monoclonal antibody fragments (both Fab and scFv) against rHBeAg. Several of the Fab/scFv, expressed in Escherichia coli , had unprecedentedly high binding affinities ( K d ∼10 -12 m) and high specificity. We used Fab/scFv in the context of an enzyme-linked immunosorbent assay (ELISA) for HBeAg quantification, which we compared with commercially available kits and verified with seroconversion panels, the WHO HBeAg standard, rHBeAg, and patient plasma samples. We found that the specificity and sensitivity are superior to those of existing commercial assays. To identify potential fine differences between rHBeAg and HBeAg, we used these Fabs in microscale immunoaffinity chromatography to purify HBeAg from individual patient plasmas. Western blotting and MS results indicated that rHBeAg and HBeAg are essentially structurally identical, although HBeAg from different patients exhibits minor carboxyl-terminal heterogeneity. We discuss several potential applications for the humanized Fab/scFv.

An improved catalog of halo wide binary candidates

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

Allen, Christine; Monroy-Rodríguez, Miguel A., E-mail: chris@astro.unam.mx

2014-08-01

We present an improved catalog of halo wide binaries compiled from an extensive literature search. Most of our binaries stem from the common proper motion binary catalogs by Allen et al. and Chanamé and Gould, but we have also included binaries from the lists of Ryan and Zapatero-Osorio and Martín. All binaries were carefully checked and their distances and systemic radial velocities are included when available. Probable membership to the halo population was tested by means of reduced proper motion diagrams for 251 candidate halo binaries. After eliminating obvious disk binaries, we ended up with 211 probable halo binaries, 150more » of which have radial velocities available. We compute galactic orbits for these 150 binaries and calculate the time they spend within the galactic disk. Considering the full sample of 251 candidate halo binaries as well as several subsamples, we find that the distribution of angular separations (or expected major semiaxes) follows a power law f(a) ∼ a {sup –1} (Oepik's relation) up to different limits. For the 50 most disk-like binaries, those that spend their entire lives within z = ±500 pc, this limit is found to be 19,000 AU (0.09 pc), while for the 50 most halo-like binaries, those that spend on average only 18% of their lives within z = ±500 pc, the limit is 63,000 AU (0.31 pc). In a companion paper, we employ this catalog to establish limits on the masses of the halo massive perturbers (massive compact halo objects).« less

Thermal conductivity enhancements and viscosity properties of water based Nanofluid containing carbon nanotubes decorated with ag nanoparticles

NASA Astrophysics Data System (ADS)

Gu, Yanni; Xu, Sheng; Wu, Xiaoshan

2018-01-01

The water based nanofluid containing carbon nanotube (CNT) decorated with Ag nanoparticles (Ag/CNT) is prepared. Its thermal conductivity (k) enhancement increases with the thermal filler loading and the decoration quantity of Ag nanoparticles. The low absolute CNT content will decrease the tangles or aggregations among the CNTs, and it will be good at the Brownian motion of CNTs in the water. It has positive effects on the thermal conductivity of nanofluid. With the increase of Ag loading, the average size of Ag nanoparticles increased, and further results in the decrease of dispersing amount of Ag/CNT as the weight of Ag/CNT is fixed. Little dispersing quantity of Ag/CNT makes it possible that the Ag/CNT particles disperse well in the fluid. So it is not easy for CNTs to form aggregation. The high intrinsic k of CNT and the effective thermal conductive networks forming by CNTs and Ag nanoparticles are good at the k enhancement. With temperature increase the k of Ag/CNT nanofluid appears improvement. The study results make it possible to develop high-efficiency nanofluid for advanced thermal management regions.

Optical properties of Ag- and AgI-doped Ge-Ga-Te far-infrared chalcogenide glasses

NASA Astrophysics Data System (ADS)

Cheng, Ci; Wang, Xunsi; Xu, Tiefeng; Sun, Lihong; Pan, Zhanghao; Liu, Shuo; Zhu, Qingde; Liao, Fangxing; Nie, Qiuhua; Dai, Shixun; Shen, Xiang; Zhang, Xianghua; Chen, Wei

2016-05-01

Te-based glasses are ideal material for life detection and infrared-sensing applications because of their excellent far-infrared properties. In this study, the influence of Ag- and AgI- doped Te-based glasses were discussed. Thermal and optical properties of the prepared glasses were evaluated using X-ray diffraction, differential scanning calorimetry, and Fourier transform infrared spectroscopy. Results show that these glass samples have good amorphous state and thermal stability. However, Ge-Ga-Te-Ag and Ge-Ga-Te-AgI glass systems exhibit completely different in optical properties. With an increase of Ag content, the absorption cut-off edge of Ge-Ga-Te-Ag glass system has a red shift. On the contrary, a blue shift appears in Ge-Ga-Te-AgI glass system with an increase of AgI content. Moreover, the transmittance of Ge-Ga-Te-Ag glass system deteriorates while that of Ge-Ga-Te-AgI glass system ameliorates. All glass samples have wide infrared transmission windows and the far-infrared cut-off wavelengths of these glasses are beyond 25 μm. The main absorption peaks of these glasses are eliminated through a purifying method.

Coating stainless steel plates with Ag/TiO2 for chlorpyrifos decontamination

NASA Astrophysics Data System (ADS)

Abdel Fattah, Wafa I.; Gobara, Mohammed M.; El-Hotaby, Walid; Mostafa, Sherif F. M.; Ali, Ghareib W.

2016-05-01

Spray coatings of either nanosilver (Ag), titanium (TiO2) or nanosilver titanium (Ag/TiO2) on stainless steel substrates prepared by sol-gel process were successfully achieved. The efficiency of the Ag/TiO2 coat onto 316 stainless steel surface towards cloropyrifos degradation as a chemical warfare agent (CWA) was proved. The crystalline structure and morphological characterization, as well as surface roughness measurements, were assessed. X-ray diffraction results proved the crystalline TiO2 anatase phase. The uniform distribution of Ag along with TiO2 nanoparticles was evidenced through transmission electron microscopy and scanning electron microscopy mapping. The hydrophilic nature of individual Ag, TiO2 and Ag/TiO2 coats was proved by contact angle measurements. The loading of Ag nanoparticles influenced positively the Ag/TiO2 coats surface roughness. The photocatalytic cloropyrifos degradation achieved about 50% within one-hour post UV treatment proving, therefore, the promising Ag/TiO2 continued decontamination efficiency. In conclusion, tuning the physical and morphological properties of TiO2 coated on stainless steel surface could be significantly enhanced by Ag nanoparticles incorporation. The developed Ag/TiO2 coat could be conveniently applied as CWA decontaminant.

Developmental toxicity of Japanese medaka embryos by silver nanoparticles and released ions in the presence of humic acid.

PubMed

Kim, Jun Y; Kim, Ki-Tae; Lee, Byeong G; Lim, Byung J; Kim, Sang D

2013-06-01

The final destination point of nanoparticles is the environment, where they remain a long period; therefore, a deep understanding of the relationship between nanoparticles and the environmental factors is required. Japanese medaka embryos were exposed to two differently prepared AgNPs: freshly prepared AgNPs and aged AgNPs. With these two AgNP preparations, we studied the impacts of humic acid in terms of embryonic toxicity, as well as the behavior of AgNPs. Aged AgNPs exhibited a lower lethal concentration (LC50) value (1.44mg/L) compared to fresh AgNPs (3.53mg/L) through 96h acute toxicity tests, due to the release of silver ions, as confirmed by kinetic analysis. The presence of humic acids considerably reduced the toxicity of aged AgNPs due to complexation with silver ions. Agglomeration, induced by interactions with humic acid, might reduce the bioavailability of AgNPs to Japanese medaka embryos. This study demonstrates that aged AgNPs releasing more silver ions are more toxic than fresh AgNPs, and humic acids play a role in reducing the toxicity of aged AgNPs. Copyright © 2013 Elsevier Inc. All rights reserved.

Direct nucleation of silver nanoparticles on graphene sheet.

PubMed

Singh, Manoj K; Titus, E; Krishna, R; Hawaldar, R R; Goncalves, G; Marques, P A A P; Gracio, J

2012-08-01

Silver (Ag) nanoparticles were synthesized on the surface of graphene sheet by the simultaneous reduction of Ag+ and graphene oxide (GO) in the presence of simple reducing agent, hydrazine hydrate (N2H4 x H2O). Both the Ag+ and GO were reduced and Ag+ was nucleated onto graphene. GO flakes were prepared by conventional chemical exfoliation method and in the presence of strong acidic medium of potassium chlorate. Silver nanoparticles were prepared using 0.01 M AgNO3 solution. The reduced GO sheet decorated with Ag is referred as G-Ag sample. G-Ag was characterized by FTIR (Fourier transform infrared) spectroscopy using GO as standard. An explicit alkene peak appeared around 1625 cm(-1) was observed in G-Ag sample. Besides, the characteristic carbonyl and hydroxyl peaks shows well reduction of GO. The FTIR therefore confirms the direct interaction of Ag into Graphene. SEM (scanning electron microscopy) and TEM (transmission electron microscopy) analysis were performed for morphological probing. The average size of Ag nanoparticles was confirmed by around 5-10 nm by the high-resolution TEM (HRTEM). The Ag quantum dots incorporated nanocomposite material could become prominent candidate for diverse applications including photovoltaic, catalysis, and biosensors etc.

Preparation of Ag deposited TiO2 (Ag/TiO2) composites and investigation on visible-light photocatalytic degradation activity in magnetic field

NASA Astrophysics Data System (ADS)

Zhang, L.; Ma, C. H.; Wang, J.; Li, S. G.; Li, Y.

2014-12-01

In this study, Ag deposited TiO2 (Ag/TiO2) composites were prepared by three different methods (Ultraviolet Irradiation Deposition (UID), Vitamin C Reduction (VCR) and Sodium Borohydride Reduction (SBR)) for the visible-light photocatalytic degradation of organic dyes in magnetic field. And then the prepared Ag deposited TiO2 (Ag/TiO2) composites were characterized physically by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The visible-light photocatalytic activities of these three kinds of Ag deposited TiO2 (Ag/TiO2) composites were examined and compared through the degradation of several organic dyes under visible-light irradiation in magnetic field. In addition, some influence factors such as visible-light irradiation time, organic dye concentration, revolution speed, magnetic field intensity and organic dye kind on the visible-light photocatalytic activity of Ag deposited TiO2 (Ag/TiO2) composite were reviewed. The research results showed that the presence of magnetic field significantly enhanced the visible-light photocatalytic activity of Ag deposited TiO2 (Ag/TiO2) composites and then contributed to the degradation of organic dyes.

Iron layer-dependent surface-enhanced raman scattering of hierarchical nanocap arrays

NASA Astrophysics Data System (ADS)

Chen, Lei; Sun, Huanhuan; Zhao, Yue; Gao, Renxian; Wang, Yaxin; Liu, Yang; Zhang, Yongjun; Hua, Zhong; Yang, Jinghai

2017-11-01

In this report, we fabricated the multi-layer Ag/Fe/Ag sandwich cap-shaped films on monolayer non-closed packed (ncp) polystyrene colloidal particle (PSCP) templates through a layer-by-layer (LBL) depositing method. This research focused on the surface-enhanced Raman scattering (SERS) effect of the thickness of the deposited Fe film which was controlled by the sputtering time. The SERS intensities were increased firstly, and then decreased as the thickness of Fe layer grows gradually, which is attributed to the charge transition from the Fermi level of the Ag NPs to Fe layer. The use of multi-layer Ag/Fe/Ag sandwich cap-shaped films enables us to evaluate the contribution of surface plasmon resonance and charge distribution between Ag and Fe to SERS enhancement. Our work introduced a novel system (Ag/Fe/Ag) for high performance SERS and extended the SERS application of Fe. Furthermore, we have designed the Ag/Fe/Ag SERS-active substrate as the immunoassay chip for quantitative determination of AFP-L3 which is the biomarker of hepatocellular carcinoma (HCC). The proposed research demonstrates that the SERS substrates with Ag/Fe/Ag sandwich cap-shaped arrays have a high sensitivity for bioassay.