30,326 research outputs found
Ag Class at Uintah High School
No full textUintah High School boys learn weed control in their ag class
U.S. IMPORTS OF CANADIAN WHEAT: ESTIMATING THE EFFECT OF THE U.S. EXPORT ENHANCEMENT PROGRAM
No full textIt is hypothesized that the U.S. Export Enhancement Program (EEP) has had a role in increased U.S. imports of Canadian wheat. Using a set of world wheat models that differentiate wheat according to class and source, several conclusions concerning the role of EEP are reached. Over the period 1986-1993, EEP has been accountable for 40 to 48 percent of the yearly growth in U.S. imports of Canadian wheat. EEP subsidies in 1991/92 to China and Brazil caused significant diversion of Canadian wheat that would have been destined for those markets instead to the U.S. market. Further, it is argued that a quota on imports is not likely to have price-enhancing effects for U.S. wheat.Canada, export enhancement program, wheat, Agricultural and Food Policy, International Relations/Trade,
Polarization dependence of the light coupling to surface plasmons in an Ag nanoparticle & Ag nanowire system
No full textPolarization dependence of the coupling of excitation light to surface plasmon polaritons (SPPs) was investigated in a Ag nanoparticle-nanowire waveguide system (a Ag nanoparticle attached to a Ag nanowire). It was found that under the illumination of excitation light on the nanoparticle-nanowire junction, the coupling efficiency of light to SPPs depends on the polarization of the excitation light. Theoretical simulations revealed that it is the local near-field coupling between the nanoparticle and the nanowire that enhances the incident light to excite the nanowire SPPs. Because the shapes of the Ag nanoparticles differ, the local field intensity, and thus the excitement of the nanowire SPPs, vary with the polarization of the excitation light.Physics, MultidisciplinarySCI(E)EI中国科技核心期刊(ISTIC)中国科学引文数据库(CSCD)[email protected]
Effects of shell thickness on the thermal stability of Cu-Ag core-shell nanoparticles: A molecular dynamics study
No full textCu-Ag core-shell (CS) nanoparticle (NP) is considered as a cost-effective alternative material to nano silver sintering material in die attachment application. To further reduce the cost, the thickness of the Ag shell can be adjusted. Whereas the shell thickness will also affect the thermal stability of the Cu-Ag CSNPs. In this study, molecular dynamics simulation was applied to study the thickness effect on the thermal behavior of Cu-Ag CSNPs. The melting points of CSNPs and Pure NPs can be determined by the evolutions of Potential Energy (PE), and the Lindemann index (LI) of the system. The results indicated that the melting points of CS NPs were lower than monometallic NP and the melting point of CS NP is influenced by the size of the Cu core and the number of lattice mismatches. Moreover, the distribution of atoms’ LI showed that the premelting point is independent of shell thickness. However, the fraction of atoms that occurred premelting is increased with the decrease of the shell thickness. Otherwise, we also simulated the sintering process of double CS NPs with equal size.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic Components, Technology and Material
Voltammetric Detection of Urea on an Ag-Modified Zeolite- Expanded Graphite-Epoxy Composite Electrode
No full textIn this paper, a modified expanded graphite composite electrode based on natural zeolitic volcanic tuff modified with silver (EG-Ag-Z-Epoxy) was developed. Cyclic voltammetry measurements revealed a reasonably fast electron transfer and a good stability of the electrode in 0.1 M NaOH supporting electrolyte. This modified electrode exhibited moderate electrocatalytic effect towards urea oxidation, allowing its determination in aqueous solution. The linear dependence of the current versus urea concentration was reached using square-wave voltammetry in the concentrations range of urea between 0.2 to 1.4 mM, with a relatively low limit of detection of 0.05 mM. A moderate enhancement of electroanalytical sensitivity for the determination of urea at EG-Ag-Z-Epoxy electrode was reached by applying a chemical preconcentration step prior to voltammetric/amperometric quantification.ChemE/Chemical EngineeringApplied Science
Electron-overdoped Ag(II)F2: mixed-valence fluorides Ag(I)Ag(II)F3 and Ag(I)2Ag(II)F4
No full textWe have successfully prepared two novel mixed-valence compounds of silver, Ag(I)Ag(II)F3 and Ag(I)2Ag(II)F4. They may be considered to be long-sought strongly electron-overdoped Ag(II)F2. Their crystal structures indicate that both belong to the Class I (mixed-valence) family with frozen Ag(I) and Ag(II) valences. The measured Raman spectra are well-correlated with the theoretical ones. Density functional theory calculations reveal their smaller fundamental band gaps as compared to pristine AgF2, due to the presence of Ag(I) states in the valence band.7 pages, 6 figures, 1 table, and a supplement of eight page
Ore mineralogy and trace element (re)distribution at the metamorphosed Lappberget Zn-Pb-Ag-(Cu-Au) deposit, Garpenberg, Sweden
No full textQualitative and quantitative mineralogical and textural investigations were undertaken for the different sulfide minerals in the 1.89 Ga Lappberget deposit, with a focus on sphalerite and pyrite. Three sphalerite types were identified and associated with: (1) main massive sulfide mineralization, (2) Fe-Mn skarn ore, and (3) Ag-rich fissure veins. Sphalerite-1 contained a relatively higher amount of trace elements (Fe, Co, Ge, Cu, Sn, and Au) but is lower in Mn/Fe, Ga, and Hg compared to sphalerite-2. Evidence of tectono-metamorphic modification of sulfides is observed throughout the deposit, such as the formation of growth twins and deformation twins in sulfides, the development of high-angled triple-point junctions in recrystallized pyrite and sphalerite, and the formation of â??ball oreâ?? or â??durchbewegungâ?? textures within mineralized shear zones. The recrystallization of pyrite and galena may have led to the re-distribution of fluid-mobile elements (As, Cu, Zn, Pb, Ag, and Au), some of which were deposited in discordant Ag-rich fissure veins peripheral to the main massive sulfide lenses. Trace element signatures of sulfides in Lappberget are compatible with the other metamorphosed and deformed, subseafloor volcanogenic carbonate replacement (SVALS)-type deposits in the Bergslagen mining district. © 2021 The Author(s)</p
Ore mineralogy and trace element (re)distribution at the metamorphosed Lappberget Zn-Pb-Ag-(Cu-Au) deposit, Garpenberg, Sweden
No full textQualitative and quantitative mineralogical and textural investigations were undertaken for the different sulfide minerals in the 1.89 Ga Lappberget deposit, with a focus on sphalerite and pyrite. Three sphalerite types were identified and associated with: (1) main massive sulfide mineralization, (2) Fe-Mn skarn ore, and (3) Ag-rich fissure veins. Sphalerite-1 contained a relatively higher amount of trace elements (Fe, Co, Ge, Cu, Sn, and Au) but is lower in Mn/Fe, Ga, and Hg compared to sphalerite-2. Evidence of tectono-metamorphic modification of sulfides is observed throughout the deposit, such as the formation of growth twins and deformation twins in sulfides, the development of high-angled triple-point junctions in recrystallized pyrite and sphalerite, and the formation of â??ball oreâ?? or â??durchbewegungâ?? textures within mineralized shear zones. The recrystallization of pyrite and galena may have led to the re-distribution of fluid-mobile elements (As, Cu, Zn, Pb, Ag, and Au), some of which were deposited in discordant Ag-rich fissure veins peripheral to the main massive sulfide lenses. Trace element signatures of sulfides in Lappberget are compatible with the other metamorphosed and deformed, subseafloor volcanogenic carbonate replacement (SVALS)-type deposits in the Bergslagen mining district. © 2021 The Author(s)</p
A comparative study in CCl4 reaction on Ag/Si(111) surfaces: PEEM and PES investigations
No full textA comparative study in CCl4 reaction on Ag/Si(111) surfaces: PEEM and PES investigations
Yunxi Yao, Qiang Fu, Xinhe Bao
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, P.R. China
We report a comparative study in the reactivity of bulk Ag(111), monolayer Ag film on Si(111), and Si(111)-77 surfaces via X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), photoemission electron microscopy (PEEM), and scanning tunneling microscopy (STM). The monolayer Ag film grown on Si(111), which is known as √3×√3-Ag-Si surface structure, was obtained by depositing one monolayer Ag on the Si(111)-77 surface at 550 K. The most simple halogen methane, CCl4, was chosen as the probe molecule to study the surface reactivity of the bulk Ag(111) surface, the monolayer Ag film, and the Si(111) surface. XPS and UPS data indicate that the monolayer Ag film presents unique reactivity to CCl4 in comparison to the other two surfaces. For the PEEM study, a dedicated sample consisting of bulk Ag particles supported on the monolayer Ag film was prepared as shown in the schematics in Fig. 1. In situ PEEM imaging of the surface reaction in presence of CCl4 shows a gradual change in the grey intensity from bright to totally dark on the Ag particles but little change on the √3×√3-Ag-Si surface. The grey intensity decrease is due to local work function increase from the dissociated Cl atoms. The experiments suggest that monolayer Ag is inert toward dissociation of CCl4 compared to the Ag(111) and Si(111) surface. It has proposed that the confinement of 5sp electron of Ag atoms in the √3×√3-Ag-Si surface, which is delocalized in the bulk Ag(111) surface, is decisive to the different reactivity.
Figure 1: (a) Schematic representation of the √3×√3-Ag-Si surface supported Ag islands; (b) PEEM image of the Ag islands/√3×√3-Ag-Si sample before CCl4 exposure. Field of view (FoV) is 27 μm; (c) PEEM image shows the same area in (b) but after 24 L (5.2×10-9 mbar × 6000 s) CCl4 exposure; (d) the work function change (ΔΦ) of the Ag(111) and √3×√3-Ag-Si surfaces when exposed to different amount of CCl4 at RT, measured from PES results.
References:
[1] Y.X. Yao, X. Liu, Q. Fu, W.X. Li, D.L. Tan, X.H. Bao, ChemPhysChem 2008, 9: 975-979.
*Corresponding author: Fax: +86-411-84694447, E-mail: [email protected], [email protected]
EXPRESSION OF A FUNCTIONAL CHIMERIC lg-MHC CLASS II PROTEIN
No full textcomposed of the a- and ß-chains of the MHC class I1
I-E molecule fused to antibody V regions derived
from anti-human CD4 mAb MT310. Expression vectors
were constructed containing the functional,
rearranged gene segments coding for the V region
domains of the antibody H and L chains in place of
the first domains of the complete structural genes
of the I-E a- and ß-chains, respectively. Celltsr ansfected
with both hybrid genes expressed a stable
protein product on the cell surface. The chimeric
molecule exhibited the idiotype of the antibody
MT310 as shown by binding to the anti-idiotypic
mAb 20-46. A protein of the anticipated molecular
mass was immunoprecipitated witha nti-mouse IgG
antiserum. Furthermore, human soluble CD4 did
bind to thetr ansfected cell line, demonstrating that
the chimeric protein possessed the binding capacity
of the original mAb. Thus, the hybrid molecule retained:
1) the properties of a MHC class I1 protein
with regardt o correct chain assembly and transport
to the cell surface: as well as 2) the Ag binding
capacity of the antibody genes used. Thgee neration
of hybrid MHC class I1 molecules with highly specific,
non-MHC-restricted bindingc apacities will be
useful for studying MHC class 11-mediated effector
functions such as selection of the T cell repertoire
in thymus of transgenic mice
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