Degradation of nonmodified and rhodium modified aluminide coating deposited on CMSX 4 superalloy.
Zagula-Yavorska, Maryana; Wierzbińska, Małgorzata; Gancarczyk, Kamil; Sieniawski, Jan
2016-07-01
The Ni-base superalloy CMSX 4 used in the turbine blades of aircraft engines was coated with rhodium layer (0.5-μm thick). Next coated CMSX 4 superalloy was aluminized by the CVD method. The rhodium modified aluminide coating and nonmodified aluminide coating were oxidized at 1100°C at the air atmosphere. The rhodium modified aluminide coating showed about twice better oxidation resistance than the nonmodified one. The spallation equal 62% of the total area was observed on the surface of the nonmodified coating whereas only 36% spallation area was observed on the surface of the rhodium modified aluminide coating after the oxidation test. The oxide layer formed on the surface of the nonmodified coating was composed of nonprotective (Ni,Cr)Al2 O4 and (Ni,Cr)O phases. Aluminium in the coating reacts with oxygen, forming a protective α-Al2 O3 oxide on the surface of the rhodium modified aluminide coating. When the oxide cracks and spalls due to oxidation, additional aluminium from the coating diffuses to the surface to form the oxide. The presence of protective Al2 O3 oxide on the surface of the rhodium modified aluminide coating slows coating degradation. Therefore, rhodium modified aluminide coating has better oxidation resistance than the nonmodified one. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.
Duan, Haohong; Yan, Ning; Yu, Rong; Chang, Chun-Ran; Zhou, Gang; Hu, Han-Shi; Rong, Hongpan; Niu, Zhiqiang; Mao, Junjie; Asakura, Hiroyuki; Tanaka, Tsunehiro; Dyson, Paul Joseph; Li, Jun; Li, Yadong
2014-01-01
Despite significant advances in the fabrication and applications of graphene-like materials, it remains a challenge to prepare single-layered metallic materials, which have great potential applications in physics, chemistry and material science. Here we report the fabrication of poly(vinylpyrrolidone)-supported single-layered rhodium nanosheets using a facile solvothermal method. Atomic force microscope shows that the thickness of a rhodium nanosheet is <4 Å. Electron diffraction and X-ray absorption spectroscopy measurements suggest that the rhodium nanosheets are composed of planar single-atom-layered sheets of rhodium. Density functional theory studies reveal that the single-layered Rh nanosheet involves a δ-bonding framework, which stabilizes the single-layered structure together with the poly(vinylpyrrolidone) ligands. The poly(vinylpyrrolidone)-supported single-layered rhodium nanosheet represents a class of metallic two-dimensional structures that might inspire further fundamental advances in physics, chemistry and material science.
Vapor deposition of thin films
Smith, David C.; Pattillo, Stevan G.; Laia, Jr., Joseph R.; Sattelberger, Alfred P.
1992-01-01
A highly pure thin metal film having a nanocrystalline structure and a process of preparing such highly pure thin metal films of, e.g., rhodium, iridium, molybdenum, tungsten, rhenium, platinum, or palladium by plasma assisted chemical vapor deposition of, e.g., rhodium(allyl).sub.3, iridium(allyl).sub.3, molybdenum(allyl).sub.4, tungsten(allyl).sub.4, rhenium(allyl).sub.4, platinum(allyl).sub.2, or palladium(allyl).sub.2 are disclosed. Additionally, a general process of reducing the carbon content of a metallic film prepared from one or more organometallic precursor compounds by plasma assisted chemical vapor deposition is disclosed.
Enhanced field emission from hexagonal rhodium nanostructures
DOE Office of Scientific and Technical Information (OSTI.GOV)
Sathe, Bhaskar R.; Kakade, Bhalchandra A.; Mulla, Imtiaz S.
2008-06-23
Shape selective synthesis of nanostructured Rh hexagons has been demonstrated with the help of a modified chemical vapor deposition using rhodium acetate. An ultralow threshold field of 0.72 V/{mu}m is observed to generate a field emission current density of 4x10{sup -3} {mu}A/cm{sup 2}. The high enhancement factor (9325) indicates that the origin of electron emission is from nanostructured features. The smaller size of emitting area, excellent current density, and stability over a period of more than 3 h are promising characteristics for the development of electron sources.
Carneiro, Marcella Lemos Brettas; Peixoto, Raphael C A; Joanitti, Graziela A; Oliveira, Ricardo G S; Telles, Luis A M; Miranda-Vilela, Ana L; Bocca, Anamélia L; Vianna, Leonora M S; da Silva, Izabel C R; de Souza, Aparecido R; Lacava, Zulmira G M; Báo, Sônia N
2013-02-16
Magnetic fluids containing superparamagnetic iron oxide nanoparticles represent an attractive platform as nanocarriers in chemotherapy. Recently, we developed a formulation of maghemite nanoparticles coated with rhodium (II) citrate, which resulted in in vitro cytotoxicity enhanced up to 4.6 times when compared to free rhodium (II) citrate formulation on breast carcinoma cells. In this work, we evaluate the antitumor activity and toxicity induced by these formulations in Balb/c mice bearing orthotopic 4T1 breast carcinoma. Mice were evaluated with regard to the treatments' toxicity through analyses of hemogram, serum levels of alanine aminotransferase, iron, and creatinine; DNA fragmentation and cell cycle of bone marrow cells; and liver, kidney and lung histology. In addition, the antitumor activity of rhodium (II) citrate and maghemite nanoparticles coated with rhodium (II) citrate was verified by tumor volume reduction, histology and immunohistochemistry. Regarding the treatments' toxicity, no experimental groups had alterations in levels of serum ALT or creatinine, and this suggestion was corroborated by the histopathologic examination of liver and kidney of mice. Moreover, DNA fragmentation frequency of bone marrow cells was lower than 15% in all experimental groups. On the other hand, the complexes rhodium (II) citrate-functionalized maghemite and free rhodium (II) citrate led to a marked growth inhibition of tumor and decrease in CD31 and Ki-67 staining. In summary, we demonstrated that both rhodium (II) citrate and maghemite nanoparticles coated with rhodium (II) citrate formulations exhibited antitumor effects against 4T1 metastatic breast cancer cell line following intratumoral administration. This antitumor effect was followed by inhibition of both cell proliferation and microvascularization and by tumor tissue injury characterized as necrosis and fibrosis. Remarkably, this is the first published report demonstrating the therapeutic efficacy of maghemite
2013-01-01
Background Magnetic fluids containing superparamagnetic iron oxide nanoparticles represent an attractive platform as nanocarriers in chemotherapy. Recently, we developed a formulation of maghemite nanoparticles coated with rhodium (II) citrate, which resulted in in vitro cytotoxicity enhanced up to 4.6 times when compared to free rhodium (II) citrate formulation on breast carcinoma cells. In this work, we evaluate the antitumor activity and toxicity induced by these formulations in Balb/c mice bearing orthotopic 4T1 breast carcinoma. Methods Mice were evaluated with regard to the treatments’ toxicity through analyses of hemogram, serum levels of alanine aminotransferase, iron, and creatinine; DNA fragmentation and cell cycle of bone marrow cells; and liver, kidney and lung histology. In addition, the antitumor activity of rhodium (II) citrate and maghemite nanoparticles coated with rhodium (II) citrate was verified by tumor volume reduction, histology and immunohistochemistry. Results Regarding the treatments’ toxicity, no experimental groups had alterations in levels of serum ALT or creatinine, and this suggestion was corroborated by the histopathologic examination of liver and kidney of mice. Moreover, DNA fragmentation frequency of bone marrow cells was lower than 15% in all experimental groups. On the other hand, the complexes rhodium (II) citrate-functionalized maghemite and free rhodium (II) citrate led to a marked growth inhibition of tumor and decrease in CD31 and Ki-67 staining. Conclusions In summary, we demonstrated that both rhodium (II) citrate and maghemite nanoparticles coated with rhodium (II) citrate formulations exhibited antitumor effects against 4T1 metastatic breast cancer cell line following intratumoral administration. This antitumor effect was followed by inhibition of both cell proliferation and microvascularization and by tumor tissue injury characterized as necrosis and fibrosis. Remarkably, this is the first published report
Thermodynamic assessment of the rhodium-ruthenium-oxygen (Rh-Ru-O) system
NASA Astrophysics Data System (ADS)
Gossé, S.; Bordier, S.; Guéneau, C.; Brackx, E.; Domenger, R.; Rogez, J.
2018-03-01
Ruthenium (Ru) and rhodium (Rh) are abundant platinum-group metals formed during burn-up of nuclear fuels. Under normal operating conditions, Rh and Ru accumulate and predominantly form metallic precipitates with other fission products like Mo, Pd and Tc. In the framework of vitrification of high-level nuclear waste, these fission products are poorly soluble in molten glasses. They precipitate as metallic particles and oxide phases. Moreover, these Ru and Rh rich phases strongly depend on temperature and the oxygen fugacity of the glass melt. In case of severe accidental conditions with air ingress, oxidation of the Ru and Rh is possible. At low temperatures (T < 1422 K for rhodium sesquioxide and T < 1815 K for ruthenium dioxide), the formed oxides are relatively stable. On the other hand, at high temperatures (T > 1422 K for rhodium sesquioxide and T > 1815 K for ruthenium dioxide), they may decompose into (Rh)-FCC or (Ru)-HCP metallic phases and radiotoxic volatile gaseous species. A thermodynamic assessment of the Rh-Ru-O system will enable the prediction of: (1) the metallic and oxide phases that form during the vitrification of high-level nuclear wastes and (2) the release of volatile gaseous species during a severe accident. The Calphad method developed herein employs a thermodynamic approach in the investigation of the thermochemistry of rhodium and ruthenium at high temperatures. Current literature on the thermodynamic properties and phase diagram data enables preliminary thermodynamic assessments of the Rh-O and Ru-O systems. Additionally, select compositions in the ternary Rh-Ru-O system underwent experimental tests to complement data found in literature and to establish the phase equilibria in the ternary system.
Rhodium complexes as therapeutic agents.
Ma, Dik-Lung; Wang, Modi; Mao, Zhifeng; Yang, Chao; Ng, Chan-Tat; Leung, Chung-Hang
2016-02-21
The landscape of inorganic medicinal chemistry has been dominated by the investigation of platinum, and to a lesser extent ruthenium, complexes over the past few decades. Recently, complexes based on other metal centers such as rhodium have attracted attention due to their tunable chemical and biological properties as well as distinct mechanisms of action. This perspective highlights recent examples of rhodium complexes that show diverse biological activities against various targets, including enzymes and protein-protein interactions.
NASA Technical Reports Server (NTRS)
Santoro, G. J.; Kohl, F. J.; Stearns, C. A.; Gokoglu, S. A.; Rosner, D. E.
1984-01-01
Deposition rates on platinum-rhodium cylindrical collectors rotating in the cross streams of the combustion gases of a salt-seeded Mach 0.3 burner rig were determined. The collectors were internally air cooled so that their surface temperatures could be widely varied while they were exposed to constant combustion gas temperatures. The deposition rates were compared with those predicted by the chemically frozen boundary layer (CFBL) computer program, which is based on multicomponent vapor transport through the boundary layer. Excellent agreement was obtained between theory and experiment for the NaCl-seeded case, but the agreement lessened as the seed was changed to synthetic sea salt, NaNO3, and K2SO4, respectively, and was particularly poor in the case of Na2SO4. However, when inertial impaction was assumed to be the deposition mechanism for the Na2SO4 case, the predicted rates agreed well with the experimental rates. The former were calculated from a mean particle diameter that was derived from the measured intial droplet size distribution of the solution spray. Critical experiments showed that liquid phase deposits were blown off the smooth surface of the platinum-rhodium collectors by the aerodynamic shear forces of the high-velocity combustion gases but that rough or porous surfaces retained their liquid deposits.
103Rh NMR spectroscopy and its application to rhodium chemistry.
Ernsting, Jan Meine; Gaemers, Sander; Elsevier, Cornelis J
2004-09-01
Rhodium is used for a number of large processes that rely on homogeneous rhodium-catalyzed reactions, for instance rhodium-catalyzed hydroformylation of alkenes, carbonylation of methanol to acetic acid and hydrodesulfurization of thiophene derivatives (in crude oil). Many laboratory applications in organometallic chemistry and catalysis involve organorhodium chemistry and a wealth of rhodium coordination compounds is known. For these and other areas, 103Rh NMR spectroscopy appears to be a very useful analytical tool. In this review, most of the literature concerning 103Rh NMR spectroscopy published from 1989 up to and including 2003 has been covered. After an introduction to several experimental methods for the detection of the insensitive 103Rh nucleus, a discussion of factors affecting the transition metal chemical shift is given. Computational aspects and calculations of chemical shifts are also briefly addressed. Next, the application of 103Rh NMR in coordination and organometallic chemistry is elaborated in more detail by highlighting recent developments in measurement and interpretation of 103Rh NMR data, in relation to rhodium-assisted reactions and homogeneous catalysis. The dependence of the 103Rh chemical shift on the ligands at rhodium in the first coordination sphere, on the complex geometry, oxidation state, temperature, solvent and concentration is treated. Several classes of compounds and special cases such as chiral rhodium compounds are reviewed. Finally, a section on scalar coupling to rhodium is provided. 2004 John Wiley & Sons, Ltd.
Oxidation-promoted activation of a ferrocene C-H bond by a rhodium complex.
Labande, Agnès; Debono, Nathalie; Sournia-Saquet, Alix; Daran, Jean-Claude; Poli, Rinaldo
2013-05-14
The oxidation of a rhodium(I) complex containing a ferrocene-based heterodifunctional phosphine N-heterocyclic carbene (NHC) ligand produces a stable, planar chiral rhodium(III) complex with an unexpected C-H activation on ferrocene. The oxidation of rhodium(I) to rhodium(III) may be accomplished by initial oxidation of ferrocene to ferrocenium and subsequent electron transfer from rhodium to ferrocenium. Preliminary catalytic tests showed that the rhodium(III) complex is active for the Grignard-type arylation of 4-nitrobenzaldehyde via C-H activation of 2-phenylpyridine.
Shu, Xing-Zhong; Li, Xiaoxun; Shu, Dongxu; Huang, Suyu; Schienebeck, Casi M.; Zhou, Xin; Robichaux, Patrick J.; Tang, Weiping
2012-01-01
A new type of rhodium-catalyzed [5+2] cycloaddition was developed for the synthesis of seven-membered rings with diverse functionalities. The ring formation was accompanied by a 1,2-acyloxy migration event. The 5- and 2-carbon components of the cycloaddition are 3-acyloxy-1,4-enynes (ACEs) and alkynes respectively. Cationic rhodium (I) catalysts worked most efficiently for the intramolecular cycloaddition, while only neutral rhodium (I) complexes could facilitate the intermolecular reaction. In both cases, electron-poor phosphite or phosphine ligands often improved the efficiency of the cycloadditions. The scope of ACEs and alkynes was investigated in both intra- and intermolecular reactions. The resulting seven-membered ring products have three double bonds that could be selectively functionalized. PMID:22364320
Cyclopentadiene-mediated hydride transfer from rhodium complexes.
Pitman, C L; Finster, O N L; Miller, A J M
2016-07-12
Attempts to generate a proposed rhodium hydride catalytic intermediate instead resulted in isolation of (Cp*H)Rh(bpy)Cl (1), a pentamethylcyclopentadiene complex, formed by C-H bond-forming reductive elimination from the fleeting rhodium hydride. The hydride transfer ability of diene 1 was explored through thermochemistry and hydride transfer reactions, including the reduction of NAD(+).
Dawande, Sudam Ganpat; Kanchupalli, Vinaykumar; Kalepu, Jagadeesh; Chennamsetti, Haribabu; Lad, Bapurao Sudam; Katukojvala, Sreenivas
2014-04-14
Disclosed herein is the design of an unprecedented electrophilic rhodium enalcarbenoid which results from rhodium(II)-catalyzed decomposition of a new class of enaldiazo compounds. The synthetic utility of these enalcarbenoids has been successfully demonstrated in the first transition-metal-catalyzed [4+2] benzannulation of pyrroles, thus leading to substituted indoles. The new benzannulation has been applied to the efficient synthesis of the natural product leiocarpone as well as a potent adipocyte fatty-acid binding protein inhibitor. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Selective Aliphatic Carbon-Carbon Bond Activation by Rhodium Porphyrin Complexes.
To, Ching Tat; Chan, Kin Shing
2017-07-18
The carbon-carbon bond activation of organic molecules with transition metal complexes is an attractive transformation. These reactions form transition metal-carbon bonded intermediates, which contribute to fundamental understanding in organometallic chemistry. Alternatively, the metal-carbon bond in these intermediates can be further functionalized to construct new carbon-(hetero)atom bonds. This methodology promotes the concept that the carbon-carbon bond acts as a functional group, although carbon-carbon bonds are kinetically inert. In the past few decades, numerous efforts have been made to overcome the chemo-, regio- and, more recently, stereoselectivity obstacles. The synthetic usefulness of the selective carbon-carbon bond activation has been significantly expanded and is becoming increasingly practical: this technique covers a wide range of substrate scopes and transition metals. In the past 16 years, our laboratory has shown that rhodium porphyrin complexes effectively mediate the intermolecular stoichiometric and catalytic activation of both strained and nonstrained aliphatic carbon-carbon bonds. Rhodium(II) porphyrin metalloradicals readily activate the aliphatic carbon(sp 3 )-carbon(sp 3 ) bond in TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxyl) and its derivatives, nitriles, nonenolizable ketones, esters, and amides to produce rhodium(III) porphyrin alkyls. Recently, the cleavage of carbon-carbon σ-bonds in unfunctionalized and noncoordinating hydrocarbons with rhodium(II) porphyrin metalloradicals has been developed. The absence of carbon-hydrogen bond activation in these systems makes the reaction unique. Furthermore, rhodium(III) porphyrin hydroxide complexes can be generated in situ to selectively activate the carbon(α)-carbon(β) bond in ethers and the carbon(CO)-carbon(α) bond in ketones under mild conditions. The addition of PPh 3 promotes the reaction rate and yield of the carbon-carbon bond activation product. Thus, both rhodium
Chemical Posttranslational Modification with Designed Rhodium(II) Catalysts.
Martin, S C; Minus, M B; Ball, Z T
2016-01-01
Natural enzymes use molecular recognition to perform exquisitely selective transformations on nucleic acids, proteins, and natural products. Rhodium(II) catalysts mimic this selectivity, using molecular recognition to allow selective modification of proteins with a variety of functionalized diazo reagents. The rhodium catalysts and the diazo reactivity have been successfully applied to a variety of protein folds, the chemistry succeeds in complex environments such as cell lysate, and a simple protein blot method accurately assesses modification efficiency. The studies with rhodium catalysts provide a new tool to study and probe protein-binding events, as well as a new synthetic approach to protein conjugates for medical, biochemical, or materials applications. © 2016 Elsevier Inc. All rights reserved.
Block copolymer lithography of rhodium nanoparticles for high temperature electrocatalysis.
Boyd, David A; Hao, Yong; Li, Changyi; Goodwin, David G; Haile, Sossina M
2013-06-25
We present a method for forming ordered rhodium nanostructures on a solid support. The approach makes use of a block copolymer to create and assemble rhodium chloride nanoparticles from solution onto a surface; subsequent plasma and thermal processing are employed to remove the polymer and fully convert the nanostructures to metallic rhodium. Films cast from a solution of the triblock copolymer poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) dissolved in toluene with rhodium(III) chloride hydrate were capable of producing a monolayer of rhodium nanoparticles of uniform size and interparticle spacing. The nanostructures were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. The electrocatalytic performance of the nanoparticles was investigated with AC impedance spectroscopy. We observed that the addition of the particles to a model solid oxide fuel cell anode provided up to a 14-fold improvement in the anode activity as evidenced by a decrease in the AC impedance resistance. Examination of the anode after electrochemical measurement revealed that the basic morphology and distribution of the particles were preserved.
Low gravity containerless processing of immiscible gold rhodium alloys
NASA Technical Reports Server (NTRS)
Andrews, J. Barry
1986-01-01
Under normal one-g conditions immiscible alloys segregate extensively during solidification due to sedementation of the more dense of the immiscible liquid phases. However, under low-g conditions it should be possible to form a dispersion of the two immiscible liquids and maintain this dispersed structure during solidification. Immiscible (hypermonotectic) gold-rhodium alloys were processed in the Marshall Space Flight Center 105 meter drop tube in order to investigate the influence of low gravity, containerless solidification on their microstructure. Hypermonotectic alloys composed of 65 atomic % rhodium exhibited a tendency for the gold rich liquid to wet the outer surface of the containerless processed samples. This tendency led to extensive segregation in several cases. However, well dispersed microstructures consisting of 2 to 3 micron diameter rhodium-rich spheres in a gold-rich matrix were produced in 23.4 atomic % rhodium alloys. This is one of the best dispersions obtained in research on immiscible alloy-systems to data.
Local Electric Field Effects on Rhodium-Porphyrin and NHC-Gold Catalysts
2015-01-05
AFRL-OSR-VA-TR-2015-0023 (NII) - Local Electric Field Effects on Rhodium -Porphyrin and NHC-Gold Catalysts MATTHEW KANAN LELAND STANFORD JUNIOR UNIV...Effects on Rhodium -Porphyrin and NHC-Gold Catalysts Principal Investigator: Matthew W. Kanan Project Publications: 1. “An Electric Field–Induced Change...Stanford University Grant/Contract Title The full title of the funded effort. (NII)-Local Electric Field Effects on Rhodium -Porphyrin and NHC-Gold
Blough, M M; Waggener, R G; Payne, W H; Terry, J A
1998-09-01
A model for calculating mammographic spectra independent of measured data and fitting parameters is presented. This model is based on first principles. Spectra were calculated using various target and filter combinations such as molybdenum/molybdenum, molybdenum/rhodium, rhodium/rhodium, and tungsten/aluminum. Once the spectra were calculated, attenuation curves were calculated and compared to measured attenuation curves. The attenuation curves were calculated and measured using aluminum alloy 1100 or high purity aluminum filtration. Percent differences were computed between the measured and calculated attenuation curves resulting in an average of 5.21% difference for tungsten/aluminum, 2.26% for molybdenum/molybdenum, 3.35% for rhodium/rhodium, and 3.18% for molybdenum/rhodium. Calculated spectra were also compared to measured spectra from the Food and Drug Administration [Fewell and Shuping, Handbook of Mammographic X-ray Spectra (U.S. Government Printing Office, Washington, D.C., 1979)] and a comparison will also be presented.
Electronic and magnetic properties of small rhodium clusters
DOE Office of Scientific and Technical Information (OSTI.GOV)
Soon, Yee Yeen; Yoon, Tiem Leong; Lim, Thong Leng
2015-04-24
We report a theoretical study of the electronic and magnetic properties of rhodium-atomic clusters. The lowest energy structures at the semi-empirical level of rhodium clusters are first obtained from a novel global-minimum search algorithm, known as PTMBHGA, where Gupta potential is used to describe the atomic interaction among the rhodium atoms. The structures are then re-optimized at the density functional theory (DFT) level with exchange-correlation energy approximated by Perdew-Burke-Ernzerhof generalized gradient approximation. For the purpose of calculating the magnetic moment of a given cluster, we calculate the optimized structure as a function of the spin multiplicity within the DFT framework.more » The resultant magnetic moments with the lowest energies so obtained allow us to work out the magnetic moment as a function of cluster size. Rhodium atomic clusters are found to display a unique variation in the magnetic moment as the cluster size varies. However, Rh{sub 4} and Rh{sub 6} are found to be nonmagnetic. Electronic structures of the magnetic ground-state structures are also investigated within the DFT framework. The results are compared against those based on different theoretical approaches available in the literature.« less
Merola, Joseph S; Franks, Marion A
2015-02-01
The crystal structures of two solvates of fac-tri-chlorido-tris-(tri-methyl-phosphane-κP)rhodium(III) are reported, i.e. one with water in the crystal lattice, fac-[RhCl3(Me3P)3]·H2O, and one with methanol in the crystal lattice, fac-[RhCl3(Me3P)3]·0.5CH3OH. These rhodium compounds exhibit distorted octahedral coordination spheres at the metal and are isotypic with the analogous iridium compounds previously reported by us [Merola et al. (2013 ▶). Polyhedron, 54, 67-73]. Comparison is made between the rhodium and iridium compounds, highlighting their isostructural relationships.
Rhodium dihydride (RhH2) with high volumetric hydrogen density
Li, Bing; Ding, Yang; Kim, Duck Young; Ahuja, Rajeev; Zou, Guangtian; Mao, Ho-Kwang
2011-01-01
Materials with very high hydrogen density have attracted considerable interest due to a range of motivations, including the search for chemically precompressed metallic hydrogen and hydrogen storage applications. Using high-pressure synchrotron X-ray diffraction technique and theoretical calculations, we have discovered a new rhodium dihydride (RhH2) with high volumetric hydrogen density (163.7 g/L). Compressing rhodium in fluid hydrogen at ambient temperature, the fcc rhodium metal absorbs hydrogen and expands unit-cell volume by two discrete steps to form NaCl-typed fcc rhodium monohydride at 4 GPa and fluorite-typed fcc RhH2 at 8 GPa. RhH2 is the first dihydride discovered in the platinum group metals under high pressure. Our low-temperature experiments show that RhH2 is recoverable after releasing pressure cryogenically to 1 bar and is capable of retaining hydrogen up to 150 K for minutes and 77 K for an indefinite length of time. PMID:22039219
Mesoporous metallic rhodium nanoparticles
NASA Astrophysics Data System (ADS)
Jiang, Bo; Li, Cuiling; Dag, Ömer; Abe, Hideki; Takei, Toshiaki; Imai, Tsubasa; Hossain, Md. Shahriar A.; Islam, Md. Tofazzal; Wood, Kathleen; Henzie, Joel; Yamauchi, Yusuke
2017-05-01
Mesoporous noble metals are an emerging class of cutting-edge nanostructured catalysts due to their abundant exposed active sites and highly accessible surfaces. Although various noble metal (e.g. Pt, Pd and Au) structures have been synthesized by hard- and soft-templating methods, mesoporous rhodium (Rh) nanoparticles have never been generated via chemical reduction, in part due to the relatively high surface energy of rhodium (Rh) metal. Here we describe a simple, scalable route to generate mesoporous Rh by chemical reduction on polymeric micelle templates [poly(ethylene oxide)-b-poly(methyl methacrylate) (PEO-b-PMMA)]. The mesoporous Rh nanoparticles exhibited a ~2.6 times enhancement for the electrocatalytic oxidation of methanol compared to commercially available Rh catalyst. Surprisingly, the high surface area mesoporous structure of the Rh catalyst was thermally stable up to 400 °C. The combination of high surface area and thermal stability also enables superior catalytic activity for the remediation of nitric oxide (NO) in lean-burn exhaust containing high concentrations of O2.
Antagonizing STAT3 dimerization with a rhodium(III) complex.
Ma, Dik-Lung; Liu, Li-Juan; Leung, Ka-Ho; Chen, Yen-Ting; Zhong, Hai-Jing; Chan, Daniel Shiu-Hin; Wang, Hui-Min David; Leung, Chung-Hang
2014-08-25
Kinetically inert metal complexes have arisen as promising alternatives to existing platinum and ruthenium chemotherapeutics. Reported herein, to our knowledge, is the first example of a substitutionally inert, Group 9 organometallic compound as a direct inhibitor of signal transducer and activator of transcription 3 (STAT3) dimerization. From a series of cyclometalated rhodium(III) and iridium(III) complexes, a rhodium(III) complex emerged as a potent inhibitor of STAT3 that targeted the SH2 domain and inhibited STAT3 phosphorylation and dimerization. Significantly, the complex exhibited potent anti-tumor activities in an in vivo mouse xenograft model of melanoma. This study demonstrates that rhodium complexes may be developed as effective STAT3 inhibitors with potent anti-tumor activity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
2011-01-01
Background Rhodium (II) citrate (Rh2(H2cit)4) has significant antitumor, cytotoxic, and cytostatic activity on Ehrlich ascite tumor. Although toxic to normal cells, its lower toxicity when compared to carboxylate analogues of rhodium (II) indicates Rh2(H2cit)4 as a promising agent for chemotherapy. Nevertheless, few studies have been performed to explore this potential. Superparamagnetic particles of iron oxide (SPIOs) represent an attractive platform as carriers in drug delivery systems (DDS) because they can present greater specificity to tumor cells than normal cells. Thus, the association between Rh2(H2cit)4 and SPIOs can represent a strategy to enhance the former's therapeutic action. In this work, we report the cytotoxicity of free rhodium (II) citrate (Rh2(H2cit)4) and rhodium (II) citrate-loaded maghemite nanoparticles or magnetoliposomes, used as drug delivery systems, on both normal and carcinoma breast cell cultures. Results Treatment with free Rh2(H2cit)4 induced cytotoxicity that was dependent on dose, time, and cell line. The IC50 values showed that this effect was more intense on breast normal cells (MCF-10A) than on breast carcinoma cells (MCF-7 and 4T1). However, the treatment with 50 μM Rh2(H2cit)4-loaded maghemite nanoparticles (Magh-Rh2(H2cit)4) and Rh2(H2cit)4-loaded magnetoliposomes (Lip-Magh-Rh2(H2cit)4) induced a higher cytotoxicity on MCF-7 and 4T1 than on MCF-10A (p < 0.05). These treatments enhanced cytotoxicity up to 4.6 times. These cytotoxic effects, induced by free Rh2(H2cit)4, were evidenced by morphological alterations such as nuclear fragmentation, membrane blebbing and phosphatidylserine exposure, reduction of actin filaments, mitochondrial condensation and an increase in number of vacuoles, suggesting that Rh2(H2cit)4 induces cell death by apoptosis. Conclusions The treatment with rhodium (II) citrate-loaded maghemite nanoparticles and magnetoliposomes induced more specific cytotoxicity on breast carcinoma cells than on breast
Rhodium(III)-Catalyzed Amidation of Unactivated C(sp(3) )-H Bonds.
Wang, He; Tang, Guodong; Li, Xingwei
2015-10-26
Nitrogenation by direct functionalization of C-H bonds represents an important strategy for constructing C-N bonds. Rhodium(III)-catalyzed direct amidation of unactivated C(sp(3) )-H bonds is rare, especially under mild reaction conditions. Herein, a broad scope of C(sp(3) )-H bonds are amidated under rhodium catalysis in high efficiency using 3-substituted 1,4,2-dioxazol-5-ones as the amide source. The protocol broadens the scope of rhodium(III)-catalyzed C(sp(3) )-H activation chemistry, and is applicable to the late-stage functionalization of natural products. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
In vitro permeation of platinum and rhodium through Caucasian skin.
Franken, A; Eloff, F C; Du Plessis, J; Badenhorst, C J; Jordaan, A; Du Plessis, J L
2014-12-01
During platinum group metals (PGMs) refining the possibility exists for dermal exposure to PGM salts. The dermal route has been questioned as an alternative route of exposure that could contribute to employee sensitisation, even though literature has been focused on respiratory exposure. This study aimed to investigate the in vitro permeation of platinum and rhodium through intact Caucasian skin. A donor solution of 0.3mg/ml of metal, K2PtCl4 and RhCl3 respectively, was applied to the vertical Franz diffusion cells with full thickness abdominal skin. The receptor solution was removed at various intervals during the 24h experiment, and analysed with high resolution ICP-MS. Skin was digested and analysed by ICP-OES. Results indicated cumulative permeation with prolonged exposure, with a significantly higher mass of platinum permeating after 24h when compared to rhodium. The mass of platinum retained inside the skin and the flux of platinum across the skin was significantly higher than that of rhodium. Permeated and skin retained platinum and rhodium may therefore contribute to sensitisation and indicates a health risk associated with dermal exposure in the workplace. Copyright © 2014 Elsevier Ltd. All rights reserved.
Superconductivity in zirconium-rhodium alloys
NASA Technical Reports Server (NTRS)
Zegler, S. T.
1969-01-01
Metallographic studies and transition temperature measurements were made with isothermally annealed and water-quenched zirconium-rhodium alloys. The results clarify both the solid-state phase relations at the Zr-rich end of the Zr-Rh alloy system and the influence upon the superconducting transition temperature of structure and composition.
Rhodium Phosphine-π-Arene Intermediates in the Hydroamination of Alkenes
Liu, Zhijian; Yamamichi, Hideaki; Madrahimov, Sherzod T.; Hartwig, John F.
2011-01-01
A detailed mechanistic study of the intramolecular hydroamination of alkenes with amines catalyzed by rhodium complexes of a biaryldialkylphosphine are reported. The active catalyst is shown to contain the phosphine ligand bound in a κ1, η6 form in which the arene is π-bound to rhodium. Addition of deuterated amine to an internal olefin showed that the reaction occurs by trans addition of the N-H bond across the C=C bond, and this stereochemistry implies that the reaction occurs by nucleophilic attack of the amine on a coordinated alkene. Indeed, the cationic rhodium fragment binds the alkene over the secondary amine, and the olefin complex was shown to be the catalyst resting state. The reaction was zero-order in substrate, when the concentration of olefin was high, and a primary isotope effect was observed. The primary isotope effect, in combination with the observation of the alkene complex as the resting state, implies that nucleophilic attack of the amine on the alkene is reversible and is followed by turnover-limiting protonation. This mechanism constitutes an unusual pathway for rhodium-catalyzed additions to alkenes and is more closely related to the mechanism for palladium-catalyzed addition of amide N-H bonds to alkenes. PMID:21309512
Rhodium-catalyzed C-H alkynylation of arenes at room temperature.
Feng, Chao; Loh, Teck-Peng
2014-03-03
The rhodium(III)-catalyzed ortho C-H alkynylation of non-electronically activated arenes is disclosed. This process features a straightforward and highly effective protocol for the synthesis of functionalized alkynes and represents the first example of merging a hypervalent iodine reagent with rhodium(III) catalysis. Notably, this reaction proceeds at room temperature, tolerates a variety of functional groups, and more importantly, exhibits high selectivity for monoalkynylation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Rhodium-Catalyzed Dehydrogenative Borylation of Cyclic Alkenes
Kondoh, Azusa; Jamison, Timothy F.
2010-01-01
A rhodium-catalyzed dehydrogenative borylation of cyclic alkenes is described. This reaction provides direct access to cyclic 1-alkenylboronic acid pinacol esters, useful intermediates in organic synthesis. Suzuki-Miyaura cross-coupling applications are also presented. PMID:20107646
Determination of phenolic compounds using spectral and color transitions of rhodium nanoparticles.
Gatselou, Vasiliki; Christodouleas, Dionysios C; Kouloumpis, Antonios; Gournis, Dimitrios; Giokas, Dimosthenis L
2016-08-17
This work reports a new approach for the determination of phenolic compounds based on their interaction with citrate-capped rhodium nanoparticles. Phenolic compounds (i.e., catechins, gallates, cinnamates, and dihydroxybenzoic acids) were found to cause changes in the size and localized surface plasmon resonance of rhodium nanoparticles, and therefore, give rise to analyte-specific spectral and color transitions in the rhodium nanoparticle suspensions. Upon reaction with phenolic compounds (mainly dithydroxybenzoate derivatives, and trihydroxybenzoate derivatives), new absorbance peaks at 350 nm and 450 nm were observed. Upon reaction with trihydroxybenzoate derivatives, however, an additional absorbance peak at 580 nm was observed facilitating the speciation of phenolic compounds in the sample. Both absorbance peaks at 450 nm and 580 nm increased with increasing concentration of phenolic compounds over a linear range of 0-500 μM. Detection limits at the mid-micromolar levels were achieved, depending on the phenolic compound involved, and with satisfactory reproducibility (<7.3%). On the basis of these findings, two rhodium nanoparticles-based assays for the determination of the total phenolic content and total catechin content were developed and applied in tea samples. The obtained results correlated favorably with commonly used methods (i.e., Folin-Ciocalteu and aluminum complexation assay). Not the least, the finding that rhodium nanoparticles can react with analytes and exhibit unique localized surface plasmon resonance bands in the visible region, can open new opportunities for developing new optical and sensing analytical applications. Copyright © 2016 Elsevier B.V. All rights reserved.
Spatial and temporal distribution of platinum, palladium and rhodium in Zagreb air.
Rinkovec, Jasmina; Pehnec, Gordana; Godec, Ranka; Davila, Silvije; Bešlić, Ivan
2018-09-15
Platinum (Pt), palladium (Pd) and rhodium (Rh) are most widely used in the production of automotive catalytic converters that serve to reduce toxic emissions from motor vehicles. The aim of this study was to quantitatively determine the levels of platinum, palladium and rhodium in the PM 10 and PM 2.5 fraction of airborne particle matter and find their spatial and temporal distribution at different polluted areas of the city of Zagreb, Croatia. The method used in this paper included weekly sampling of airborne particle matter on quartz filters, microwave digestion in acid under high pressure and temperature, and analysis by inductively coupled plasma mass spectrometry (ICP MS). The results have shown that the highest mean values at all three sampling stations (North, Center, South) were obtained for palladium (3.856 pg m -3 , 5.396 pg m -3 , 5.600 pg m -3 ) and the lowest for rhodium (0.444 pg m -3 , 0.643 pg m -3 , 0.750 pg m -3 ). The average mass concentrations of platinum group elements (PGE) in PM 10 increased for all three elements in the direction North < Center < South which had to do with the traffic load nearby the monitoring stations. The ratio of measured mass concentrations to all measuring stations was similar to platinum, palladium and rhodium content in automotive catalytic converters. Factor analysis grouped platinum, palladium and rhodium at all of the monitoring stations, and their relation to other metals together with the aforementioned results indicate that their main source of pollution is traffic or precisely automotive catalytic converters. At all three of the monitoring sites, higher values were measured during the colder part of the year. The results of measuring platinum, palladium and rhodium levels in the city of Zagreb are the first results of their kind for this area and will provide insights into the contribution of catalytic converters to the presence of these elements in the environment. Copyright
Zhou, Li-Mei; Guo, Cai-Hong; Fu, Hai-Yan; Jiang, Xiao-Hui; Chen, Hua; Li, Rui-Xiang; Li, Xian-Jun
2012-07-01
The interactions of rhodium complex RhCl(CO)(TPPTS)(2) [TPPTS=P(m-C(6)H(4)SO(3)Na)(3)] with cationic, nonionic, and anionic surfactants have been investigated by UV-vis, fluorescence and (1)H NMR measurements. The presence of four different species of RhCl(CO)(TPPTS)(2) in cationic cetyltrimethylammonium (CTAB) solution has been demonstrated: free rhodium complex, rhodium complex bound to CTAB monomer, rhodium complex bound to CTAB premicelles, rhodium complex bound to CTAB micelles. The spectroscopy data show that RhCl(CO)(TPPTS)(2) can adsorb on the interface of cationic CTAB micelles by strong electrostatic attraction, weakly bind to the nonionic polyoxyethylene (20) sorbitan monolaurate (Tween 20) micelles by hydrophobic interaction, and does not interact with anion sodium dodecyl sulfate (SDS) micelles due to the strong electrostatic repulsion. Copyright © 2012 Elsevier B.V. All rights reserved.
Coughlin, Jane M; Kundu, Rituparna; Cooper, Julian C; Ball, Zachary T
2014-11-15
A small molecule containing a rhodium(II) tetracarboxylate fragment is shown to be a potent inhibitor of the prolyl isomerase FKBP12. The use of small molecules conjugates of rhodium(II) is presented as a general strategy for developing new protein inhibitors based on distinct structural and sequence features of the enzyme active site. Copyright © 2014 Elsevier Ltd. All rights reserved.
Tandem rhodium catalysis:Exploiting sulfoxides for asymmetric transition-metal catalysis
Kou, K. G. M.
2015-01-01
Sulfoxides are uncommon substrates for transition-metal catalysis due to their propensity to inhibit catalyst turnover. In a collaborative effort with Ken Houk, we developed the first dynamic kinetic resolution (DKR) of allylic sulfoxides using asymmetric rhodium-catalyzed hydrogenation. Detailed mechanistic analysis of this transformation using both experimental and theoretical methods revealed rhodium to be a tandem catalyst that promoted both hydrogenation of the alkene and racemization of the allylic sulfoxide. Using a combination of deuterium labelling and DFT studies, a novel mode of allylic sulfoxide racemization via a Rh(III)-π-allyl intermediate was identified. PMID:25940066
Tandem rhodium catalysis: exploiting sulfoxides for asymmetric transition-metal catalysis.
Kou, K G M; Dong, V M
2015-06-07
Sulfoxides are uncommon substrates for transition-metal catalysis due to their propensity to inhibit catalyst turnover. In a collaborative effort with Ken Houk, we developed the first dynamic kinetic resolution (DKR) of allylic sulfoxides using asymmetric rhodium-catalyzed hydrogenation. A detailed mechanistic analysis of this transformation using both experimental and theoretical methods revealed rhodium to be a tandem catalyst that promoted both hydrogenation of the alkene and racemization of the allylic sulfoxide. Using a combination of deuterium labelling and DFT studies, a novel mode of allylic sulfoxide racemization via a Rh(III)-π-allyl intermediate was identified.
DNA Mismatch Binding and Antiproliferative Activity of Rhodium Metalloinsertors
Ernst, Russell J.; Song, Hang; Barton, Jacqueline K.
2009-01-01
Deficiencies in mismatch repair (MMR) are associated with carcinogenesis. Rhodium metalloinsertors bind to DNA base mismatches with high specificity and inhibit cellular proliferation preferentially in MMR-deficient cells versus MMR-proficient cells. A family of chrysenequinone diimine complexes of rhodium with varying ancillary ligands that serve as DNA metalloinsertors has been synthesized, and both DNA mismatch binding affinities and antiproliferative activities against the human colorectal carcinoma cell lines HCT116N and HCT116O, an isogenic model system for MMR deficiency, have been determined. DNA photocleavage experiments reveal that all complexes bind to the mismatch sites with high specificities; DNA binding affinities to oligonucleotides containing single base CA and CC mismatches, obtained through photocleavage titration or competition, vary from 104 to 108 M−1 for the series of complexes. Significantly, binding affinities are found to be inversely related to ancillary ligand size and directly related to differential inhibition of the HCT116 cell lines. The observed trend in binding affinity is consistent with the metalloinsertion mode where the complex binds from the minor groove with ejection of mismatched base pairs. The correlation between binding affinity and targeting of the MMR-deficient cell line suggests that rhodium metalloinsertors exert their selective biological effects on MMR-deficient cells through mismatch binding in vivo. PMID:19175313
The influence of pH on the in vitro permeation of rhodium through human skin.
Jansen Van Rensburg, Sané; Franken, Anja; Du Plessis, Jeanetta; Du Plessis, Johannes Lodewykus
2017-06-01
Workers in precious metals refineries are at risk of exposure to salt compounds of the platinum group metals through inhalation, as well as through the skin. Rhodium salt permeation through the skin has previously been proven using rhodium trichloride (RhCl 3 ) dissolved in synthetic sweat at a pH of 6.5. However, the skin surface pH of refinery workers may be lower than 6.5. The aim of this study was to investigate the influence of pH 6.5 and 4.5 on the in vitro permeation of rhodium through intact Caucasian skin using Franz diffusion cells. A concentration of 0.3 mg mL -1 rhodium was used and analyses were performed using inductively coupled plasma mass spectrometry and inductively coupled plasma optical emission spectrometry. Results indicated a cumulative increase in permeation over 24 h. Rhodium permeation after 12 h was significantly greater at pH 4.5 (1.56 ± 0.24 ng cm -2 ) than at 6.5 (0.85 ± 0.13 ng cm -2 ; p = 0.02). At both pH levels, there was a highly significant difference ( p < 0.01) between the mass of rhodium remaining in the skin (1428.68 ± 224.67 ng cm -2 at pH 4.5 and 1029.90 ± 115.96 ng cm -2 at pH 6.5) and the mass that diffused through (0.88 ± 0.17 ng cm -2 at pH 4.5 and 0.62 ± 0.10 ng cm -2 at pH 6.5). From these findings, it is evident that an acidic working environment or low skin surface pH may enhance permeation of rhodium salts, contributing to sensitization and adverse health effects.
Hepburn, Hamish B; Lam, Hon Wai
2014-10-20
Allylrhodium species generated from potassium allyltrifluoroborates can undergo isomerization by 1,4-rhodium(I) migration to give more complex isomers, which then react with cyclic imines to provide products with up to three new stereochemical elements. High enantioselectivities are obtained using chiral diene-rhodium complexes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Meng, Qingxi; Shen, Wei; Li, Ming
2012-03-01
Density functional theory (DFT) was used to investigate the Rh(I)-catalyzed intermolecular hydroacylation of vinylsilane with benzaldehyde. All intermediates and transition states were optimized completely at the B3LYP/6-31G(d,p) level (LANL2DZ(f) for Rh). Calculations indicated that Rh(I)-catalyzed intermolecular hydroacylation is exergonic, and the total free energy released is -110 kJ mol(-1). Rh(I)-catalyzed intermolecular hydroacylation mainly involves the active catalyst CA2, rhodium-alkene-benzaldehyde complex M1, rhodium-alkene-hydrogen-acyl complex M2, rhodium-alkyl-acyl complex M3, rhodium-alkyl-carbonyl-phenyl complex M4, rhodium-acyl-phenyl complex M5, and rhodium-ketone complex M6. The reaction pathway CA2 + R2 → M1b → T1b → M2b → T2b1 → M3b1 → T4b → M4b → T5b → M5b → T6b → M6b → P2 is the most favorable among all reaction channels of Rh(I)-catalyzed intermolecular hydroacylation. The reductive elimination reaction is the rate-determining step for this pathway, and the dominant product predicted theoretically is the linear ketone, which is consistent with Brookhart's experiments. Solvation has a significant effect, and it greatly decreases the free energies of all species. The use of the ligand Cp' (Cp' = C(5)Me(4)CF(3)) decreased the free energies in general, and in this case the rate-determining step was again the reductive elimination reaction.
NASA Astrophysics Data System (ADS)
Li, Yangfan; Hamada, Yukitaka; Otobe, Katsunori; Ando, Teiichi
2017-02-01
Multi-traverse CS provides a unique means for the production of thick coatings and bulk materials from powders. However, the material along spray and spray-layer boundaries is often poorly bonded as it is laid by the leading and trailing peripheries of the spray that carry powder particles with insufficient kinetic energy. For the same reason, the splats in the very first layer deposited on the substrate may not be bonded well either. A mathematical spray model was developed based on an axisymmetric Gaussian mass flow rate distribution and a stepped deposition yield to predict the thickness of such poorly-bonded layers in multi-traverse CS deposition. The predicted thickness of poorly-bonded layers in a multi-traverse Cu coating falls in the range of experimental values. The model also predicts that the material that contains poorly bonded splats could exceed 20% of the total volume of the coating.
Raoufmoghaddam, Saeed; Drent, Eite; Bouwman, Elisabeth
2013-09-01
A rhodium/xantphos homogeneous catalyst system has been developed for direct chemo- and regioselective mono-N-alkylation of primary amides with 1-alkenes and syngas through catalytic hydroamidomethylation with 1-pentene and acetamide as model substrates. For appropriate catalyst performance, it appears to be essential that catalytic amounts of a strong acid promoter, such as p-toluenesulfonic acid (HOTs), as well as larger amounts of a weakly acidic protic promoter, particularly hexafluoroisopropyl alcohol (HOR(F) ) are applied. Apart from the product N-1-hexylacetamide, the isomeric unsaturated intermediates, hexanol and higher mass byproducts, as well as the corresponding isomeric branched products, can be formed. Under optimized conditions, almost full alkene conversion can be achieved with more than 80% selectivity to the product N-1-hexylamide. Interestingly, in the presence of a relatively high concentration of HOR(F) , the same catalyst system shows a remarkably high selectivity for the formation of hexanol from 1-pentene with syngas, thus presenting a unique example of a selective rhodium-catalyzed hydroformylation-hydrogenation tandem reaction under mild conditions. Time-dependent product formation during hydroamidomethylation batch experiments provides evidence for aldehyde and unsaturated intermediates; this clearly indicates the three-step hydroformylation/condensation/hydrogenation reaction sequence that takes place in hydroamidomethylation. One likely role of the weakly acidic protic promoter, HOR(F) , in combination with the strong acid HOTs, is to establish a dual-functionality rhodium catalyst system comprised of a neutral rhodium(I) hydroformylation catalyst species and a cationic rhodium(III) complex capable of selectively reducing the imide and/or ene-amide intermediates that are in a dynamic, acid-catalyzed condensation equilibrium with the aldehyde and amide in a syngas environment. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Cobalt-rhodium heterobimetallic nanoparticle-catalyzed reactions.
Park, Ji Hoon; Chung, Young Keun
2008-05-14
Transition metal nanoparticles have attracted a great deal of attention. This review discusses the synthesis of heterobimetallic cobalt-rhodium nanoparticles and their use as catalysts in organic transformations. Co-Rh nanoparticles (Co2Rh2) with a fixed stoichiometry (2 : 2) were easily obtained from Co2Rh2(CO)12. These nanoparticles were quite effective catalysts for carbonylation reactions. Particularly, special focus is paid to the Pauson-Khand-type reaction.
NASA Astrophysics Data System (ADS)
Kassem, Mohammed A.; Amin, Alaa S.
2015-02-01
A new method to estimate rhodium in different samples at trace levels had been developed. Rhodium was complexed with 5-(4‧-nitro-2‧,6‧-dichlorophenylazo)-6-hydroxypyrimidine-2,4-dione (NDPHPD) as a complexing agent in an aqueous medium and concentrated by using Triton X-114 as a surfactant. The investigated rhodium complex was preconcentrated with cloud point extraction process using the nonionic surfactant Triton X-114 to extract rhodium complex from aqueous solutions at pH 4.75. After the phase separation at 50 °C, the surfactant-rich phase was heated again at 100 °C to remove water after decantation and the remaining phase was dissolved using 0.5 mL of acetonitrile. Under optimum conditions, the calibration curve was linear for the concentration range of 0.5-75 ng mL-1 and the detection limit was 0.15 ng mL-1 of the original solution. The enhancement factor of 500 was achieved for 250 mL samples containing the analyte and relative standard deviations were ⩽1.50%. The method was found to be highly selective, fairly sensitive, simple, rapid and economical and safely applied for rhodium determination in different complex materials such as synthetic mixture of alloys and environmental water samples.
Kassem, Mohammed A; Amin, Alaa S
2015-02-05
A new method to estimate rhodium in different samples at trace levels had been developed. Rhodium was complexed with 5-(4'-nitro-2',6'-dichlorophenylazo)-6-hydroxypyrimidine-2,4-dione (NDPHPD) as a complexing agent in an aqueous medium and concentrated by using Triton X-114 as a surfactant. The investigated rhodium complex was preconcentrated with cloud point extraction process using the nonionic surfactant Triton X-114 to extract rhodium complex from aqueous solutions at pH 4.75. After the phase separation at 50°C, the surfactant-rich phase was heated again at 100°C to remove water after decantation and the remaining phase was dissolved using 0.5mL of acetonitrile. Under optimum conditions, the calibration curve was linear for the concentration range of 0.5-75ngmL(-1) and the detection limit was 0.15ngmL(-1) of the original solution. The enhancement factor of 500 was achieved for 250mL samples containing the analyte and relative standard deviations were ⩽1.50%. The method was found to be highly selective, fairly sensitive, simple, rapid and economical and safely applied for rhodium determination in different complex materials such as synthetic mixture of alloys and environmental water samples. Copyright © 2014 Elsevier B.V. All rights reserved.
Meissner, Antje; König, Anja; Drexler, Hans-Joachim; Thede, Richard; Baumann, Wolfgang; Heller, Detlef
2014-11-03
Dimeric rhodium complexes of the type [Rh(PP)(μ2 -Cl)]2 (PP=diphosphine) are often used as precatalysts and are generated "in situ" from the corresponding diolefin complexes by exchange of the diene with the desired diphosphine. Herein, we report that the "in situ" procedure also leads to unexpected monomeric pentacoordinated neutral complexes of the type [RhCl(PP)(diolefin)], for the first time herein characterized by NMR spectroscopy and X-ray crystallography for the ligands 1,4-bis(diphenylphosphino)propane (DPPP), 1,4-bis(diphenylphosphino)butane (DPPB), and 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP). The pentacoordinated complexes are in equilibrium with the dimeric target compound [Rh(PP)(μ2 -Cl)]2 . The equilibrium is influenced by the rhodium-diolefin precursor, the solvent and the temperature. Based on the results of NMR and UV/Vis spectroscopic analysis (kinetics) it could be shown that the pentacoordinated complex [RhCl(PP)(diolefin)] may arise both from the "in situ"-generated neutral complex [Rh(PP)(μ2 -Cl)] by reaction with the free diolefin and, more surprisingly, directly from [Rh(diolefin)(μ2 -Cl)]2 and the diphosphine. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Hart, Jonathan R.; Glebov, Oleg; Ernst, Russell J.; Kirsch, Ilan R.; Barton, Jacqueline K.
2006-01-01
Mismatch repair (MMR) is critical to maintaining the integrity of the genome, and deficiencies in MMR are correlated with cancerous transformations. Bulky rhodium intercalators target DNA base mismatches with high specificity. Here we describe the application of bulky rhodium intercalators to inhibit cellular proliferation differentially in MMR-deficient cells compared with cells that are MMR-proficient. Preferential inhibition by the rhodium complexes associated with MMR deficiency is seen both in a human colon cancer cell line and in normal mouse fibroblast cells; the inhibition of cellular proliferation depends strictly on the MMR deficiency of the cell. Furthermore, our assay of cellular proliferation is found to correlate with DNA mismatch targeting by the bulky metallointercalators. It is the Δ-isomer that is active both in targeting base mismatches and in inhibiting DNA synthesis. Additionally, the rhodium intercalators promote strand cleavage at the mismatch site with photoactivation, and we observe that the cellular response is enhanced with photoactivation. Targeting DNA mismatches may therefore provide a cell-selective strategy for chemotherapeutic design. PMID:17030786
Komor, Alexis C.; Schneider, Curtis J.; Weidmann, Alyson G.; Barton, Jacqueline K.
2013-01-01
Deficiencies in the mismatch repair (MMR) pathway are associated with several types of cancers, as well as resistance to commonly used chemotherapeutics. Rhodium metalloinsertors have been found to bind DNA mismatches with high affinity and specificity in vitro, and also exhibit cell-selective cytotoxicity, targeting MMR-deficient cells over MMR-proficient cells. Ten distinct metalloinsertors with varying lipophilicities have been synthesized and their mismatch binding affinities and biological activities determined. Although DNA photocleavage experiments demonstrate that their binding affinities are quite similar, their cell-selective antiproliferative and cytotoxic activities vary significantly. Inductively coupled plasma mass spectrometry (ICP-MS) experiments have uncovered a relationship between the subcellular distribution of these metalloinsertors and their biological activities. Specifically, we find that all of our metalloinsertors localize in the nucleus at sufficient concentrations for binding to DNA mismatches. However, the metalloinsertors with high rhodium localization in the mitochondria show toxicity that is not selective for MMR-deficient cells, whereas metalloinsertors with less mitochondrial rhodium show activity that is highly selective for MMR-deficient versus proficient cells. This work supports the notion that specific targeting of the metalloinsertors to nuclear DNA gives rise to their cell-selective cytotoxic and antiproliferative activities. The selectivity in cellular targeting depends upon binding to mismatches in genomic DNA. PMID:23137296
Enantioselective rhodium/ruthenium photoredox catalysis en route to chiral 1,2-aminoalcohols.
Ma, Jiajia; Harms, Klaus; Meggers, Eric
2016-08-09
A rhodium-based chiral Lewis acid catalyst combined with [Ru(bpy)3](PF6)2 as a photoredox sensitizer allows for the visible-light-activated redox coupling of α-silylamines with 2-acyl imidazoles to afford, after desilylation, 1,2-amino-alcohols in yields of 69-88% and with high enantioselectivity (54-99% ee). The reaction is proposed to proceed via an electron exchange between the α-silylamine (electron donor) and the rhodium-chelated 2-acyl imidazole (electron acceptor), followed by a stereocontrolled radical-radical reaction. Substrate scope and control experiments reveal that the trimethylsilyl group plays a crucial role in this reductive umpolung of the carbonyl group.
Zhang, Jing-Jing; Muenzner, Julienne K; Abu El Maaty, Mohamed A; Karge, Bianka; Schobert, Rainer; Wölfl, Stefan; Ott, Ingo
2016-08-16
A rhodium(i) and a ruthenium(ii) complex with a caffeine derived N-heterocyclic carbene (NHC) ligand were biologically investigated as organometallic conjugates consisting of a metal center and a naturally occurring moiety. While the ruthenium(ii) complex was largely inactive, the rhodium(i) NHC complex displayed selective cytotoxicity and significant anti-metastatic and in vivo anti-vascular activities and acted as both a mammalian and an E. coli thioredoxin reductase inhibitor. In HCT-116 cells it increased the reactive oxygen species level, leading to DNA damage, and it induced cell cycle arrest, decreased the mitochondrial membrane potential, and triggered apoptosis. This rhodium(i) NHC derivative thus represents a multi-target compound with promising anti-cancer potential.
Zhang, Liqiu; Liu, Lichun; Wang, Hongdan; Shen, Hongxia; Cheng, Qiong; Yan, Chao; Park, Sungho
2017-01-01
This work reports on the electrodeposition of rhodium (Rh) nanowires with a controlled surface morphology synthesized using an anodic aluminum oxide (AAO) template. Vertically aligned Rh nanowires with a smooth and coarse morphology were successfully deposited by adjusting the electrode potential and the concentration of precursor ions and by involving a complexing reagent in the electrolyte solution. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses were used to follow the morphological evolution of Rh nanowires. As a heterogeneous electrocatalyst for hydrogen evolution reactions (HER), the coarse Rh nanowire array exhibited an enhanced catalytic performance respect to smooth ones due to the larger surface area to mass ratio and the higher density of catalytically active defects, as evidenced by voltammetric measurements and TEM. Results suggest that the morphology of metallic nanomaterials could be readily engineered by electrodeposition. The controlled electrodeposition offers great potential for the development of an effective synthesis tool for heterogeneous catalysts with a superior performance for wide applications. PMID:28467375
High-temperature, long-term drift of platinum-rhodium thermocouples
NASA Technical Reports Server (NTRS)
Szaniszlo, A. J.
1970-01-01
Contamination of thermocouples is minimized by use of pure alumina insulators and a controlled low-impurity-level high-vacuum environment. Average thermal electromotive force change for platinum-rhodium thermocouples was -2.8 deg K after 3700 hours exposure to a mean temperature of 1530 deg K.
A rhodium(III)-based inhibitor of autotaxin with antiproliferative activity.
Kang, Tian-Shu; Wang, Wanhe; Zhong, Hai-Jing; Liang, Jia-Xin; Ko, Chung-Nga; Lu, Jin-Jian; Chen, Xiu-Ping; Ma, Dik-Lung; Leung, Chung-Hang
2017-02-01
Cancer of the skin is by far the most common of all cancers. Melanoma accounts for only about 1% of skin cancers but causes a large majority of skin cancer deaths. Autotaxin (ATX), also known as ectonucleotide pyrophosphatase/phosphodiesterase 2 (ENPP2), regulates physiological and pathological functions of lysophosphatidic acid (LPA), and is thus an important therapeutic target. We synthesized ten metal-based complexes and a novel cyclometalated rhodium(III) complex 1 was identified as an ATX enzymatic inhibitor using multiple methods, including ATX enzymatic assay, thermal shift assay, western immunoblotting and so on. Protein thermal shift assays showed that 1 increased the melting temperature (T m ) of ATX by 3.5°C. 1 also reduced ATX-LPA mediated downstream survival signal pathway proteins such as ERK and AKT, and inhibited the activation of the transcription factor nuclear factor κB (NF-κB) and signal transducer and activator of transcription 3 (STAT3). 1 also exhibited strong anti-proliferative activity against A2058 melanoma cells (IC 50 =0.58μM). Structure-activity relationship indicated that both the rhodium(III) center and the auxiliary ligands of complex 1 are important for bioactivity. 1 represents a promising scaffold for the development of small-molecule ATX inhibitors for anti-tumor applications. To our knowledge, complex 1 is the first metal-based ATX inhibitor reported to date. Rhodium complexes will have the increased attention in therapeutic and bioanalytical applications. Copyright © 2016 Elsevier B.V. All rights reserved.
Joo, Jung Min; David, Ramoncito A.; Yuan, Yu; Lee, Chulbom
2010-01-01
The total synthesis of the erythrina alkaloid 3–demethoxyerythratidinone has been achieved via a strategy based on combined rhodium catalysis. The catalytic tandem cyclization effected by the interplay of alkynyl and vinylidene rhodium species allows for efficient access to the A and B rings of the tetracyclic erythrinane skeleton in a single step. The synthesis also features rapid preparation of the requisite precursor for the double ring closure and thus has been completed in only 7 total steps in 41% overall yield. PMID:21090648
NASA Astrophysics Data System (ADS)
Inb-Elhaj, M.; Guillon, D.; Skoulios, A.; Maldivi, P.; Giroud-Godquin, A. M.; Marchon, J.-C.
1992-12-01
EXAFS was used to investigate the local structure of the polar spines of rhodium (II) soaps in the columnar liquid crystalline state. It was also used to ascertain the degree of blending of the cores in binary mixtures of rhodium (II) and copper (II) soaps. For the pure rhodium soaps, the columns are shown to result from the stacking of binuclear metal-metal bonded dirhodium tetracarboxylate units bonded to one another by apical ligation of the metal atom of each complex with one of the oxygen atoms of the adjacent molecule. Mixtures of rhodium (II) and copper (II) soaps give a hexagonal columnar mesophase in which pure rhodium and pure copper columns are randomly distributed.
Cmoch, Piotr; Głaszczka, Rafał; Jaźwiński, Jarosław; Kamieński, Bohdan; Senkara, Elżbieta
2014-03-01
Complexation of tetrakis(μ2-N,N'-diphenylformamidinato-N,N')-di-rhodium(II) with ligands containing nitrile, isonitrile, amine, hydroxyl, sulfhydryl, isocyanate, and isothiocyanate functional groups has been studied in liquid and solid phases using (1)H, (13)C and (15)N NMR, (13)C and (15)N cross polarisation-magic angle spinning NMR, and absorption spectroscopy in the visible range. The complexation was monitored using various NMR physicochemical parameters, such as chemical shifts, longitudinal relaxation times T1 , and NOE enhancements. Rhodium(II) tetraformamidinate selectively bonded only unbranched amine (propan-1-amine), pentanenitrile, and (1-isocyanoethyl)benzene. No complexation occurred in the case of ligands having hydroxyl, sulfhydryl, isocyanate, and isothiocyanate functional groups, and more expanded amine molecules such as butan-2-amine and 1-azabicyclo[2.2.2]octane. Such features were opposite to those observed in rhodium(II) tetracarboxylates, forming adducts with all kind of ligands. Special attention was focused on the analysis of Δδ parameters, defined as a chemical shift difference between signal in adduct and corresponding signal in free ligand. In the case of (1)H NMR, Δδ values were either negative in adducts of rhodium(II) tetraformamidinate or positive in adducts of rhodium(II) tetracarboxylates. Experimental findings were supported by density functional theory molecular modelling and gauge independent atomic orbitals chemical shift calculations. The calculation of chemical shifts combined with scaling procedure allowed to reproduce qualitatively Δδ parameters. Copyright © 2013 John Wiley & Sons, Ltd.
Asymmetric Synthesis of Hydrocarbazoles Catalyzed by an Octahedral Chiral-at-Rhodium Lewis Acid.
Huang, Yong; Song, Liangliang; Gong, Lei; Meggers, Eric
2015-12-01
A bis-cyclometalated chiral-at-metal rhodium complex catalyzes the Diels-Alder reaction between N-Boc-protected 3-vinylindoles (Boc = tert-butyloxycarbonyl) and β-carboxylic ester-substituted α,β-unsaturated 2-acyl imidazoles with good-to-excellent regioselectivity (up to 99:1) and excellent diastereoselectivity (>50:1 d.r.) as well as enantioselectivity (92-99% ee) under optimized conditions. The rhodium catalyst serves as a chiral Lewis acid to activate the 2-acyl imidazole dienophile by two-point binding and overrules the preferred regioselectivity of the uncatalyzed reaction. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Hurlocker, Brisa; Abascal, Nadia C.; Repka, Lindsay M.; Santizo-Deleon, Elsy; Smenton, Abigail L.; Baranov, Victoria; Gupta, Ritu; Bernard, Sarah E.; Chowdhury, Shenjuti; Rojas, Christian M.
2011-01-01
By using (N-tosyloxy)-3-O-carbamoyl-D-glucal 10, which removes the need for a hypervalent iodine(III) oxidant, we provide evidence for rhodium nitrenoid-mediated ipso C–H activation as the origin of a C3-oxidized dihydropyranone product 3. This system may be especially susceptible to such a pathway due to the ease of forming a cation upon hydride transfer to the rhodium-complexed acyl nitrene. PMID:21381715
Oinen, Mark Emil; Yu, Robert T.; Rovis, Tomislav
2009-01-01
Excess substrate has been identified as an unintended spectator ligand affecting enantioselectivity in the [2+2+2] cycloaddition of alkenyl isocyanates with tolanes. Replacement of excess substrate with an exogenous additive affords products with consistent and higher ee’s. The increase in enantioselectivity is the result of a change in composition of a proposed rhodium(III) intermediate on the catalytic cycle. The net result is a rational probe of a short-lived rhodium(III) intermediate, and gives insight that may have applications in many rhodium catalyzed reactions. PMID:19803471
Munker, Sven; Kilo, Sonja; Röß, Christoph; Jeitner, Peter; Schierl, Rudolf; Göen, Thomas; Drexler, Hans
2016-11-01
In this study the exposure of the general population in Germany to platinum and rhodium and its determinants was investigated in 259 participants (subdivided in three groups) by urine analyses and assessment of the dental status. Complementary, an interview including questions characterising possible exposure to traffic exhaust was conducted. The median excretion was 2.42ng platinum/g creatinine and 7.27ng rhodium/g creatinine. The detailed analysis of the collected data showed significant higher platinum excretion values with increasing number of surfaces covered with restorations containing precious metals (R=0.389; p<0.001), but also higher values for habitants of urban areas (median=3.43ng/g creatinine; 95th percentile=25.2ng/g) compared with those of rural areas (median=2.06ng/g creatinine; 95th percentile=20.0ng/g). Also, participants working in urban areas showed higher platinum excretion values (median=3.27ng/g; 95th percentile=19.6ng/g). Male participants living and working next to highly frequented roads showed higher rhodium excretion values (median=7.27ng/g; 95th percentile=13.5 ng/g). In summary, the study showed that exhaust emissions have an influence on platinum and rhodium excretion, but for platinum this influence is rather low compared to the influence of precious metals containing restorations. Copyright © 2016 Elsevier GmbH. All rights reserved.
Peixoto, Raphael Cândido Apolinário; Miranda-Vilela, Ana Luisa; de Souza Filho, José; Carneiro, Marcella Lemos' Brettas; Oliveira, Ricardo G S; da Silva, Matheus Oliveira; de Souza, Aparecido R; Báo, Sônia Nair
2015-05-01
Breast cancer is one of the most prevalent cancer types among women. The use of magnetic fluids for specific delivery of drugs represents an attractive platform for chemotherapy. In our previous studies, it was demonstrated that maghemite nanoparticles coated with rhodium (II) citrate (Magh-Rh2Cit) induced in vitro cytotoxicity and in vivo antitumor activity, followed by intratumoral administration in breast carcinoma cells. In this study, our aim was to follow intravenous treatment to evaluate the systemic antitumor activity and toxicity induced by these formulations in Balb/c mice bearing orthotopic 4T1 breast carcinoma. Female Balb/c mice were evaluated with regard to toxicity of intravenous treatments through analyses of hemogram, serum levels of alanine aminotransferase, iron, and creatinine and liver, kidney, and lung histology. The antitumor activity of rhodium (II) citrate (Rh2Cit), Magh-Rh2Cit, and maghemite nanoparticles coated with citrate (Magh-Cit), used as control, was evaluated by tumor volume reduction, histology, and morphometric analysis. Magh-Rh2Cit and Magh-Cit promoted a significant decrease in tumor area, and no experimental groups presented hematotoxic effects or increased levels of serum ALT and creatinine. This observation was corroborated by the histopathological examination of the liver and kidney of mice. Furthermore, the presence of nanoparticles was verified in lung tissue with no morphological changes, supporting the idea that our nanoformulations did not induce toxicity effects. No studies about the systemic action of rhodium (II) citrate-loaded maghemite nanoparticles have been carried out, making this report a suitable starting point for exploring the therapeutic potential of these compounds in treating breast cancer.
Rhodium-catalyzed C-H functionalization with N-acylsaccharins.
Wu, Hongxiang; Liu, Tingting; Cui, Ming; Li, Yue; Jian, Junsheng; Wang, Hui; Zeng, Zhuo
2017-01-18
A rhodium-catalyzed C-H functionalization with activated amides by decarbonylation has been developed. Notably, this is the first C-H arylation employing N-acylsaccharins as coupling partners to give biaryls in good to excellent yields. The highlight of the work is the high tolerance of functional groups such as formyl, ester, and vinyl and the use of a removable directing group.
Selective Cytotoxicity of Rhodium Metalloinsertors in Mismatch Repair-Deficient Cells†
Ernst, Russell J.; Komor, Alexis C.; Barton, Jacqueline K.
2011-01-01
Mismatches in DNA occur naturally during replication and as a result of endogenous DNA damaging agents, but the mismatch repair (MMR) pathway acts to correct mismatches before subsequent rounds of replication. Rhodium metalloinsertors bind to DNA mismatches with high affinity and specificity and represent a promising strategy to target mismatches in cells. Here we examine the biological fate of rhodium metalloinsertors bearing dipyridylamine ancillary ligands in cells deficient in MMR versus those that are MMR-proficient. These complexes are shown to exhibit accelerated cellular uptake which permits the observation of various cellular responses, including disruption of the cell cycle, monitored by flow cytometry assays, and induction of necrosis, monitored by dye exclusion and caspase inhibition assays, that occur preferentially in the MMR-deficient cell line. These cellular responses provide insight into the mechanisms underlying the selective activity of this novel class of targeted anti-cancer agents. PMID:22103240
Thermodynamics of Alloys: Studies of Nickel-Gallium, Nickel-Germanium and Nickel-Rhodium Alloys.
NICKEL ALLOYS, *GALLIUM ALLOYS, *GERMANIUM ALLOYS, * RHODIUM ALLOYS, *PHASE STUDIES, THERMODYNAMICS, INTERMETALLIC COMPOUNDS, FREE ENERGY, ENTROPY, HEAT OF FORMATION, CRYSTAL STRUCTURE, UNITED KINGDOM.
Qiu, Youai; Kong, Wei-Jun; Struwe, Julia; Sauermann, Nicolas; Rogge, Torben; Scheremetjew, Alexej; Ackermann, Lutz
2018-05-14
Rhodium(III) catalysis has enabled a plethora of oxidative C-H functionalizations, which predominantly employ stoichiometric amounts of toxic and/or expensive metal oxidants. In contrast, we herein describe the first electrochemical rhodium-catalyzed C-H activation that avoids hazardous chemical oxidants. Environmentally benign twofold C-H/C-H functionalizations were accomplished with weakly coordinating benzoic acids and benzamides, employing electricity as the terminal oxidant and generating H 2 as the sole byproduct. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Itooka, Ryoh; Iguchi, Yuki; Miyaura, Norio
2003-07-25
The effects of ligands and bases in the rhodium(I)-catalyzed 1,4-addition of arylboronic acids to alpha,beta-unsaturated carbonyl compounds were reinvestigated to carry out the reaction under mild conditions. Rhodium(I) complexes possessing a 1,5-cyclooctadiene (cod) and a hydroxo ligand such as [RhOH(cod)](2) exhibited excellent catalyst activities compared to those of the corresponding rhodium-acac or -chloro complexes and their phosphine derivatives. The reaction was further accelerated in the presence of KOH, thus allowing the 1,4-addition even at 0 degrees C. A cationic rhodium(I)-(R)-binap complex, [Rh(R-binap)(nbd)]BF(4), catalyzed the reaction at 25-50 degrees C in the presence of Et(3)N with high enantioselectivities of up to 99% ee for alpha,beta-unsaturated ketones, 92% for aldehydes, 94% for esters, and 92% for amides.
Ring Expansion and Rearrangements of Rhodium(II) Azavinyl Carbenes
Selander, Nicklas; Worrell, Brady T.
2013-01-01
An efficient, regioselective and convergent method for the ring expansion and rearrangement of 1-sulfonyl-1,2,3-triazoles under rhodium(II)-catalyzed conditions is described. These denitrogenative reactions form substituted enaminone and olefin-based products, which in the former case can be further functionalized to unique products rendering the sulfonyl triazole traceless. PMID:23161725
Rhodium(II)-catalyzed enantioselective synthesis of troponoids.
Murarka, Sandip; Jia, Zhi-Jun; Merten, Christian; Daniliuc, Constantin-G; Antonchick, Andrey P; Waldmann, Herbert
2015-06-22
We report a rhodium(II)-catalyzed highly enantioselective 1,3-dipolar cycloaddition reaction between the carbonyl moiety of tropone and carbonyl ylides to afford troponoids in good to high yields with excellent enantioselectivity. We demonstrate that α-diazoketone-derived carbonyl ylides, in contrast to carbonyl ylides derived from diazodiketoesters, undergo [6+3] cycloaddition reactions with tropone to yield the corresponding bridged heterocycles with excellent stereoselectivity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Rhodium-catalyzed Chemo- and Regioselective Cross-dimerization of Two Terminal Alkynes
Xu, Hua-Dong; Zhang, Ren-Wei; Li, Xiaoxun; Huang, Suyu; Tang, Weiping; Hu, Wen-Hao
2013-01-01
Cross-dimerization of terminal arylacetylenes and terminal propargylic alcohols/amides has been achieved in the effect of a rhodium catalyst. This method features high chemo- and regioselectivities rendering convenient and atom economical access to functionalized enynes. PMID:23356993
Sakuma; Sakai; Itooka; Miyaura
2000-09-22
Arylboronic acids underwent the conjugate 1,4-addition to alpha, beta-unsaturated esters to give beta-aryl esters in high yields in the presence of a rhodium(I) catalyst. The addition of arylboronic acids to isopropyl crotonate resulted in high yields and high enantioselectivity exceeding 90% ee in the presence of 3 mol % of Rh(acac)(C(2)H(4))(2) and (S)-binap at 100 degrees C. The rhodium/(S)-binap complex provided (R)-3-phenylbutanoate in the addition of phenylboronic acid to benzyl crotonate. The effects on the enantioselectivity of chiral phosphine ligands, rhodium precursors, and substituents on alpha,beta-unsaturated esters are discussed, as well as the mechanistic aspect of the catalytic cycle.
Jing, Qing; Okrasa, Krzysztof; Kazlauskas, Romas J
2009-01-01
One useful synthetic reaction missing from nature's toolbox is the direct hydrogenation of substrates using hydrogen. Instead nature uses cofactors like NADH to reduce organic substrates, which adds complexity and cost to these reductions. To create an enzyme that can directly reduce organic substrates with hydrogen, researchers have combined metal hydrogenation catalysts with proteins. One approach is an indirect link where a ligand is linked to a protein and the metal binds to the ligand. Another approach is direct linking of the metal to protein, but nonspecific binding of the metal limits this approach. Herein, we report a direct hydrogenation of olefins catalyzed by rhodium(I) bound to carbonic anhydrase (CA-[Rh]). We minimized nonspecific binding of rhodium by replacing histidine residues on the protein surface using site-directed mutagenesis or by chemically modifying the histidine residues. Hydrogenation catalyzed by CA-[Rh] is slightly slower than for uncomplexed rhodium(I), but the protein environment induces stereoselectivity favoring cis- over trans-stilbene by about 20:1. This enzyme is the first cofactor-independent reductase that reduces organic molecules using hydrogen. This catalyst is a good starting point to create variants with tailored reactivity and selectivity. This strategy to insert transition metals in the active site of metalloenzymes opens opportunities to a wider range of enzyme-catalyzed reactions.
Mild partial deoxygenation of esters catalyzed by an oxazolinylborate-coordinated rhodium silylene
Xu, Songchen; Boschen, Jeffery S.; Biswas, Abhranil; ...
2015-08-17
An electrophilic, coordinatively unsaturated rhodium complex supported by borate-linked oxazoline, oxazoline-coordinated silylene, and N-heterocyclic carbene donors [{κ³-N,Si,C-PhB(Ox Me²)(Ox Me²SiHPh)Im Mes}Rh(H)CO][HB(C₆F₅)₃] (2, Ox Me² = 4,4-dimethyl-2-oxazoline; Im Mes = 1-mesitylimidazole) is synthesized from the neutral rhodium silyl {PhB(Ox Me²)₂Im Mes}RhH(SiH 2Ph)CO (1) and B(C 6F 5) 3. The unusual oxazoline-coordinated silylene structure in 2 is proposed to form by rearrangement of an unobserved isomeric cationic rhodium silylene species [{PhB(Ox Me²)₂Im Mes}RhH(SiHPh)CO][HB(C₆F₅)₃] generated by H abstraction. Complex 2 catalyzes reductions of organic carbonyl compounds with silanes to give hydrosilylation products or deoxygenation products. The pathway to these reactions is primarily influenced bymore » the degree of substitution of the organosilane. Reactions with primary silanes give deoxygenation of esters to ethers, amides to amines, and ketones and aldehydes to hydrocarbons, whereas tertiary silanes react to give 1,2-hydrosilylation of the carbonyl functionality. In contrast, the strong Lewis acid B(C₆F₅)₃ catalyzes the complete deoxygenation of carbonyl compounds to hydrocarbons with PhSiH₃ as the reducing agent.« less
Mild partial deoxygenation of esters catalyzed by an oxazolinylborate-coordinated rhodium silylene
DOE Office of Scientific and Technical Information (OSTI.GOV)
Xu, Songchen; Boschen, Jeffery S.; Biswas, Abhranil
An electrophilic, coordinatively unsaturated rhodium complex supported by borate-linked oxazoline, oxazoline-coordinated silylene, and N-heterocyclic carbene donors [{κ³-N,Si,C-PhB(Ox Me²)(Ox Me²SiHPh)Im Mes}Rh(H)CO][HB(C₆F₅)₃] (2, Ox Me² = 4,4-dimethyl-2-oxazoline; Im Mes = 1-mesitylimidazole) is synthesized from the neutral rhodium silyl {PhB(Ox Me²)₂Im Mes}RhH(SiH 2Ph)CO (1) and B(C 6F 5) 3. The unusual oxazoline-coordinated silylene structure in 2 is proposed to form by rearrangement of an unobserved isomeric cationic rhodium silylene species [{PhB(Ox Me²)₂Im Mes}RhH(SiHPh)CO][HB(C₆F₅)₃] generated by H abstraction. Complex 2 catalyzes reductions of organic carbonyl compounds with silanes to give hydrosilylation products or deoxygenation products. The pathway to these reactions is primarily influenced bymore » the degree of substitution of the organosilane. Reactions with primary silanes give deoxygenation of esters to ethers, amides to amines, and ketones and aldehydes to hydrocarbons, whereas tertiary silanes react to give 1,2-hydrosilylation of the carbonyl functionality. In contrast, the strong Lewis acid B(C₆F₅)₃ catalyzes the complete deoxygenation of carbonyl compounds to hydrocarbons with PhSiH₃ as the reducing agent.« less
Chambers, Matthew B; Wang, Xia; Elgrishi, Noémie; Hendon, Christopher H; Walsh, Aron; Bonnefoy, Jonathan; Canivet, Jérôme; Quadrelli, Elsje Alessandra; Farrusseng, David; Mellot-Draznieks, Caroline; Fontecave, Marc
2015-02-01
The first photosensitization of a rhodium-based catalytic system for CO2 reduction is reported, with formate as the sole carbon-containing product. Formate has wide industrial applications and is seen as valuable within fuel cell technologies as well as an interesting H2 -storage compound. Heterogenization of molecular rhodium catalysts is accomplished via the synthesis, post-synthetic linker exchange, and characterization of a new metal-organic framework (MOF) Cp*Rh@UiO-67. While the catalytic activities of the homogeneous and heterogeneous systems are found to be comparable, the MOF-based system is more stable and selective. Furthermore it can be recycled without loss of activity. For formate production, an optimal catalyst loading of ∼10 % molar Rh incorporation is determined. Increased incorporation of rhodium catalyst favors thermal decomposition of formate into H2 . There is no precedent for a MOF catalyzing the latter reaction so far. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Sobolevskiy, Anatoly [Orlando, FL; Rossin, Joseph A [Columbus, OH; Knapke, Michael J [Columbus, OH
2011-07-12
A process for the catalytic reduction of nitrogen oxides (NOx) in a gas stream (29) in the presence of H.sub.2 is provided. The process comprises contacting the gas stream with a catalyst system (38) comprising zirconia-silica washcoat particles (41), a pre-sulfated zirconia binder (44), and a catalyst combination (40) comprising palladium and at least one of rhodium, ruthenium, or a mixture of ruthenium and rhodium.
Correlation between the Stereochemistry and Bioactivity in Octahedral Rhodium Prolinato Complexes.
Rajaratnam, Rajathees; Martin, Elisabeth K; Dörr, Markus; Harms, Klaus; Casini, Angela; Meggers, Eric
2015-08-17
Controlling the relative and absolute configuration of octahedral metal complexes constitutes a key challenge that needs to be overcome in order to fully exploit the structural properties of octahedral metal complexes for applications in the fields of catalysis, materials sciences, and life sciences. Herein, we describe the application of a proline-based chiral tridentate ligand to decisively control the coordination mode of an octahedral rhodium(III) complex. We demonstrate the mirror-like relationship of synthesized enantiomers and differences between diastereomers. Further, we demonstrate, using the established pyridocarbazole pharmacophore ligand as part of the organometallic complexes, the importance of the relative and absolute stereochemistry at the metal toward chiral environments like protein kinases. Protein kinase profiling and inhibition data confirm that the proline-based enantiopure rhodium(III) complexes, despite having all of the same constitution, differ strongly in their selectivity properties despite their unmistakably mutual origin. Moreover, two exemplary compounds have been shown to induce different toxic effects in an ex vivo rat liver model.
Hung, Chang-Mao; Lin, Wei-Bang; Ho, Ching-Lin; Shen, Yun-Hwei; Hsia, Shao-Yi
2010-08-01
This work adopted aqueous solutions of ammonia for use in catalytic liquid-phase reduction in a trickle-bed reactor with a platinum-rhodium bimetallic catalyst, prepared by the co-precipitation of chloroplatinic acid (H2PtCl6) and rhodium nitrate [Rh(NO3)3]. The experimental results demonstrated that a minimal amount of ammonia was removed from the solution by wet oxidation in the absence of any catalyst, while approximately 97.0% of the ammonia was removed by wet oxidation over the platinum-rhodium bimetallic catalyst at 230 degrees C with an oxygen partial pressure of 2.0 MPa. The oxidation of ammonia has been studied as a function of pH, and the main reaction products were determined. A synergistic effect is manifest in the platinum-rhodium bimetallic structure, in which the material has the greatest capacity to reduce ammonia. The reaction pathway linked the oxidizing ammonia to nitric oxide, nitrogen, and water.
Hung, Chang-Mao
2009-04-15
Aqueous solutions of 400-1000 mg/L of ammonia were oxidized in a trickle-bed reactor (TBR) in this study of nanoscale platinum-palladium-rhodium composite oxide catalysts, which were prepared by the co-precipitation of H(2)PtCl(6), Pd(NO(3))(3) and Rh(NO(3))(3). Hardly any of the dissolved ammonia was removed by wet oxidation in the absence of any catalyst, whereas about 99% of the ammonia was reduced during wet oxidation over nanoscale platinum-palladium-rhodium composite oxide catalysts at 503 K in an oxygen partial pressure of 2.0 MPa. A synergistic effect exists in the nanoscale platinum-palladium-rhodium composite structure, which is the material with the highest ammonia reduction activity. The nanometer-sized particles were characterized by TEM, XRD and FTIR. The effect of the initial concentration and reaction temperature on the removal of ammonia from the effluent streams was also studied at a liquid hourly space velocity of under 9 h(-1) in the wet catalytic processes.
Taher, Mohammad Ali; Pourmohammad, Fatemeh; Fazelirad, Hamid
2015-12-01
In the present work, an electrothermal atomic absorption spectrometric method has been developed for the determination of ultra-trace amounts of rhodium after adsorption of its 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol/tetraphenylborate ion associated complex at the surface of alumina. Several factors affecting the extraction efficiency such as the pH, type of eluent, sample and eluent flow rates, sorption capacity of alumina and sample volume were investigated and optimized. The relative standard deviation for eight measurements of 0.1 ng/mL of rhodium was ±6.3%. In this method, the detection limit was 0.003 ng/mL in the original solution. The sorption capacity of alumina and the linear range for Rh(III) were evaluated as 0.8 mg/g and 0.015-0.45 ng/mL in the original solution, respectively. The proposed method was successfully applied for the extraction and determination of rhodium content in some food and standard samples with high recovery values. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Onopchenki, A.; Sabourin, E.T.
1986-02-25
This patent describes a process for the production of a mixture of saturated and unstaurated silahydrocarbons. This process contacts an admixture consisting of (A) at least one alpha-olefin containing from 2 to about 20 carbon atoms per molecule, and (B) at least one alkylsilane selected from the group consisting of (i) a dialkylsilane (ii) a trialkylsilane (iii) mixtures thereof, with a catalyst consisting of a homogeneous monomeric rhodium-containing catalyst having a basicity substantially equal to or less than that provided by a rhodium-containing catalyst having a triphenyl phosphine ligand or a heterogeneous rhodium-containing catalyst in a halogen-free inert solvent. Themore » process conducted at a temperature of from about 30/sup 0/ to about 200/sup 0/C., a weight ratio of olefin to alkylsilane of from about 0.5 to about 20 to one and a catalyst concentration of from about 1 x 10-/sup 5/ to about 1 x 10-/sup 2/ millimoles of catalyst per millimole alkylsilane, to produce a mixture containing saturated silane hydrocarbons and an unsaturated silahydrocarbon. Inclusive with the proviso that the molecular weight of the unsaturated silane hydrocarbon is above 300.« less
Panish, Robert A; Chintala, Srinivasa R; Fox, Joseph M
2016-04-11
A novel, mixed-ligand chiral rhodium(II) catalyst, Rh2(S-NTTL)3(dCPA), has enabled the first enantioselective total synthesis of the natural product piperarborenine B. A crystal structure of Rh2(S-NTTL)3(dCPA) reveals a "chiral crown" conformation with a bulky dicyclohexylphenyl acetate ligand and three N-naphthalimido groups oriented on the same face of the catalyst. The natural product was prepared on large scale using rhodium-catalyzed bicyclobutanation/ copper-catalyzed homoconjugate addition chemistry in the key step. The route proceeds in ten steps with an 8% overall yield and 92% ee. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Arylation of Rhodium(II) Azavinyl Carbenes with Boronic Acids
Selander, Nicklas; Worrell, Brady T.; Chuprakov, Stepan; Velaparthi, Subash; Fokin, Valery V.
2013-01-01
A highly efficient and stereoselective arylation of in situ generated azavinyl carbenes affording 2,2-diaryl enamines at ambient temperatures has been developed. These transition metal carbenes are directly produced from readily available and stable 1-sulfonyl-1,2,3-triazoles in the presence of a rhodium carboxylate catalyst. In several cases, the enamines generated in this reaction can be cyclized into substituted indoles employing copper catalysts. PMID:22913576
Bimetallic poly- and oligo-nuclear complexes based on a rhodium(III) metalloligand
NASA Astrophysics Data System (ADS)
Vasilchenko, Danila B.; Venediktov, Anatoliy B.; Korenev, Sergey V.; Filatov, Evgeniy Yu.; Baidina, Iraida A.; Nadolinnyi, Vladimir A.
2012-10-01
Interaction of trans-[Rh(i-Nic)4Cl2]3- anions (i-Nic- - isonicotinate anion) with Cuaq2+ and Coaq2+ cations in water has afforded complex salts Co3[Rh(i-Nic)4Cl2]2·17H2O (1) and Cu3[Rh(i-Nic)4Cl2]2·14H2O (2). Oligonuclear character of 1 and 2 has been established. A coordination polymer Cu5[Rh(i-Nic)4Cl2]2(i-Nic)2(OH)2·2H2O (3) has been crystallized by hydrothermal treatment of 2 at 160 °C, and its structure was determined by X-ray structural analysis. EPR data for the complexes has been collected and interpreted. Thermal decomposition of the salts was studied by c-DTA. Bimetallic alloys rhodium-copper and rhodium-cobalt have been obtained as final products of thermal decomposition.
Permeation of platinum and rhodium nanoparticles through intact and damaged human skin
NASA Astrophysics Data System (ADS)
Mauro, Marcella; Crosera, Matteo; Bianco, Carlotta; Adami, Gianpiero; Montini, Tiziano; Fornasiero, Paolo; Jaganjac, Morana; Bovenzi, Massimo; Filon, Francesca Larese
2015-06-01
The aim of the study was to evaluate percutaneous penetration of platinum and rhodium nanoparticles (PtNPs: 5.8 ± 0.9 nm, RhNPs: 5.3 ± 1.9 nm) through human skin. Salts compounds of these metals are sensitizers and some also carcinogenic agents. In vitro permeation experiments were performed using Franz diffusion cells with intact and damaged skin. PtNPs and RhNPs, stabilized with polyvinylpyrrolidone, were synthesized by reduction of Na2PtCl6 and RhCl3·3H2O respectively. Suspensions with a concentration of 2.0 g/L of PtNPs and RhNPs were dispersed separately in synthetic sweat at pH 4.5 and applied as donor phases to the outer surface of the skin for 24 h. Measurements of the content of the metals in the receiving solution and in the skin were performed subsequently. Rhodium skin permeation was demonstrated through damaged skin, with a permeation flux of 0.04 ± 0.04 μg cm-2 h-1 and a lag time of 7.9 ± 1.1 h, while no traces of platinum were found in receiving solutions. Platinum and rhodium skin-analysis showed significantly higher concentrations of the metals in damaged skin. Rh and Pt applied as NPs can penetrate the skin barrier and Rh can be found in receiving solutions. These experiments pointed out the need for skin contamination prevention, since even a minor injury to the skin barrier can significantly increase penetration.
Julian, Lisa D.; Hartwig, John F.
2010-01-01
We report a rhodium catalyst that exhibits high reactivity for the hydroamination of primary aminoalkenes that are unbiased toward cyclization and that possess functional groups that would not be tolerated in hydroaminations catalyzed by more electrophilic systems. This catalyst contains an unusual diaminophosphine ligand that binds to rhodium in a κ3-P,O,P mode. The reactions catalyzed by this complex typically proceed at mild temperatures (room temperature to 70 °C), occur with primary aminoalkenes lacking substituents on the alkyl chain that bias the system toward cyclization, occur with primary aminoalkenes containing chloride, ester, ether, enolizable ketone, nitrile, and unprotected alcohol functionality, and occur with primary aminoalkenes containing internal olefins. Mechanistic data imply that these reactions occur with a turnover-limiting step that is different from that of reactions catalyzed by late transition metal complexes of Pd, Pt, and Ir. This change in the turnover-limiting step and resulting high activity of the catalyst stem from favorable relative rates for protonolysis of the M-C bond to release the hydroamination product vs reversion of the aminoalkyl intermediate to regenerate the acyclic precursor. Probes for the origin of the reactivity of the rhodium complex of L1 imply that the aminophosphine groups lead to these favorable rates by effects beyond steric demands and simple electron donation to the metal center. PMID:20839807
Molecular recognition in protein modification with rhodium metallopeptides
Ball, Zachary T.
2015-01-01
Chemical manipulation of natural, unengineered proteins is a daunting challenge which tests the limits of reaction design. By combining transition-metal or other catalysts with molecular recognition ideas, it is possible to achieve site-selective protein reactivity without the need for engineered recognition sequences or reactive sites. Some recent examples in this area have used ruthenium photocatalysis, pyridine organocatalysis, and rhodium(II) metallocarbene catalysis, indicating that the fundamental ideas provide opportunities for using diverse reactivity on complex protein substrates and in complex cell-like environments. PMID:25588960
DOE Office of Scientific and Technical Information (OSTI.GOV)
Carpio, M.M.; Kerr, J.B.
2005-01-01
Biosensing devices are important because they can detect, record, and transmit information regarding the presence of, or physiological changes in, different chemical or biological materials in the environment. The goal of this research is to prepare a biosensing device that is effective, quick, and low cost. This is done by examining which chemicals will work best when placed in a biosensor. The first study involved experimenting on a rhodium catalyst complexed with ligands such as bipyridine and imidazole. The rhodium catalyst is important because it is reduced from RhIII to RhI, forms a hydride by reaction with water and releasesmore » the hydride to react with nicotinamide adenine dinucleotide (NAD+) to selectively produce 1,4-NADH, the reduced form of NAD+. The second study looked at different types of ketones and enzymes for the enzyme-substrate reaction converting a ketone into an alcohol. Preliminary results showed that the rhodium complexed with bipyridine was able to carry out all the reactions, while the rhodium complexed with imidazole was not able to produce and release hydrides. In addition, the most effective ketone to use is benzylacetone with the enzyme alcohol dehydrogenase from baker’s yeast. Future work includes experimenting with bis-imidazole, which mimics the structure of bipyridine to see if it has the capability to reduce and if the reduction rate is comparable to the bipyridine complex. Once all testing is completed, the fastest catalysts will be combined with polymer membranes designed for fuel cells to prepare biosensing devices that can be used in a variety of applications including ones in the medical and environmental fields.« less
Zahmakiran, Mehmet; Ozkar, Saim
2009-09-21
Herein we report the discovery of a superior dimethylamine-borane dehydrogenation catalyst, more active than the prior best heterogeneous catalyst (Jaska, C. A.; Manners, I. J. Am. Chem. Soc. 2004, 126, 9776) reported to date for the dehydrogenation of dimethylamine-borane. The new catalyst system consists of rhodium(0) nanoclusters stabilized by C(5)H(11)COO(-) anions and Me(2)H(2)N(+) cations and can reproducibly be formed from the reduction of rhodium(II) hexanoate during dehydrogenation of dimethylamine-borane at room temperature. Rhodium(0) nanoclusters in an average particle size of 1.9 +/- 0.6 nm Rh(0)(approximately 190) nanoclusters) provide 1040 turnovers over 26 h with a record initial turnover frequency (TOF) of 60 h(-1) (the average TOF value is 40 h(-1)) in the dehydrogenation of dimethylamine-borane, yielding 100% of the cyclic product (Me(2)NBH(2))(2) at room temperature. The work reported here also includes the full experimental details of the following major components: (i) Characterization of dimethylammonium hexanoate stabilized rhodium(0) nanoclusters by using TEM, STEM, EDX, XRD, UV-vis, XPS, FTIR, (1)H, (13)C, and (11)B NMR spectroscopy, and elemental analysis. (ii) Collection of a wealth of previously unavailable kinetic data to determine the rate law and activation parameters for catalytic dehydrogenation of dimethylamine-borane. (iii) Monitoring of the formation kinetics of the rhodium(0) nanoclusters by a fast dimethylamine-borane dehydrogenation catalytic reporter reaction (Watzky, M. A.; Finke, R. G. J. Am. Chem. Soc. 1997, 119, 10382) at various [Me(2)NH.BH(3)]/[Rh] ratios and temperatures. Significantly, sigmoidal kinetics of catalyst formation was found to be well fit to the two-step, slow nucleation and then autocatalytic surface growth mechanism, A --> B (rate constant k(1)) and A + B --> 2B (rate constant k(2)), in which A is [Rh(C(5)H(11)CO(2))(2)](2) and B is the growing, catalytically active rhodium(0) nanoclusters. (iv) Mercury
Watkins, Avery L; Landis, Clark R
2010-08-04
Gas pressure influences the regioselectivity and enantioselectivity of aryl alkene hydroformylation as catalyzed by rhodium complexes of the BisDiazaphos ligand. Deuterioformylation of styrene at 80 degrees C results in extensive deuterium incorporation into the terminal position of the recovered styrene. This result establishes that rhodium hydride addition to form a branched alkyl rhodium occurs reversibly. The independent effect of carbon monoxide and hydrogen partial pressures on regioselectivity and enantioselectivity were measured. From 40 to 120 psi, both regioisomer (b:l) and enantiomer (R:S) ratios are proportional to the carbon monoxide partial pressure but approximately independent of the hydrogen pressure. The absolute rate for linear aldehyde formation was found to be inhibited by carbon monoxide pressure, whereas the rate for branched aldehyde formation is independent of CO pressure up to 80 psi; above 80 psi one observes the onset of inhibition. The carbon monoxide dependence of the rate and enantioselectivity for branched aldehyde indicates that the rate of production of (S)-2-phenyl propanal is inhibited by CO pressure, while the formation rate of the major enantiomer, (R)-2-phenyl propanal, is approximately independent of CO pressure. Hydroformylation of alpha-deuteriostyrene at 80 degrees C followed by conversion to (S)-2-benzyl-4-nitrobutanal reveals that 83% of the 2-phenylpropanal resulted from rhodium hydride addition to the re face of styrene, and 83% of the 3-phenylpropanal resulted from rhodium hydride addition to the si face of styrene. On the basis of these results, kinetic and steric/electronic models for the determination of regioselectivity and enantioselectivity are proposed.
Lee, Sung Woo; Yu, Mi-Yeon; Baek, Seon Ha; Ahn, Shin-Young; Kim, Sejoong; Na, Ki Young; Chae, Dong-Wan; Chin, Ho Jun
2016-01-01
There has been little published information on risk factors for poor long-term outcome in adult biopsy-proven minimal change disease (MCD). Data from sixty-three adult, biopsy-proven primary MCD patients treated at a tertiary university hospital between 2003 and 2013 were analyzed. Baseline clinical and pathologic factors were assessed for the associations with composite outcome of creatinine doubling, end stage renal disease, or all-cause mortality. During a median (interquartile) 5.0 (2.8-5.0) years, the composite outcome occurred in 11.1% (7/63) of patients. The rate of glomerular immune deposits was 23.8% (15/63). Patients with glomerular immune deposits showed a significantly lower urine protein creatinine ratio than those without deposits (P = 0.033). The rate of non-responders was significantly higher in patients with glomerular immune deposits than in those without deposits (P = 0.033). In patients with deposits, 26.7% (4/15) developed the composite outcome, while only 6.3% (3/48) developed the composite outcome among those without deposits (P = 0.049). In multivariate Cox proportional hazards regression analysis, the presence of glomerular immune deposits was the only factor associated with development of the composite outcome (hazard ratio: 2.310, 95% confidence interval: 1.031-98.579, P = 0.047). Glomerular immune deposits were associated with increased risk of a composite outcome in adult MCD patients. The higher rate of non-responders in patients with deposits might be related to the poor outcome. Future study is needed.
Highly selective rhodium catalyzed domino C-H activation/cyclizations.
Trans, Duc N; Cramer, Nicolai
2011-01-01
The direct functionalization of carbon-hydrogen bonds is an emerging tool to establish more sustainable and efficient synthetic methods. We present its implementation in a cascade reaction that provides a rapid assembly of functionalized indanylamines from simple and readily available starting materials. Careful choice of the ancillary ligand---an electron-rich bidentate phosphine ligand--enables highly diastereoselective rhodium(i)-catalyzed intramolecular allylations of unsubstituted ketimines induced by a directed C-H bond activation and allene carbo-metalation sequence.
Rhodium-catalyzed redox-neutral coupling of phenidones with alkynes.
Fan, Zhoulong; Lu, Heng; Li, Wei; Geng, Kaijun; Zhang, Ao
2017-07-21
A switchable synthesis of N-substituted indole derivatives from phenidones via rhodium-catalyzed redox-neutral C-H activation has been achieved. In this protocol, we firstly disclosed that the reactivity of Rh(iii) catalysis could be enhanced through employing palladium acetate as an additive. Some representative features include external oxidant-free, applicable to terminal alkynes, short reaction time and operational simplicity. The utility of this method is further showcased by the economical synthesis of potent anticancer PARP-1 inhibitors.
Divergent Reactivity of Rhodium(I) Carbenes Derived from Indole Annulations.
Li, Xiaoxun; Li, Hui; Song, Wangze; Tseng, Po-Sen; Liu, Lingyan; Guzei, Ilia A; Tang, Weiping
2015-10-26
Rhodium(I) carbenes were generated from propargylic alcohol derivatives as the result of a dehydrative indole annulation. Depending on the choice of the electron-withdrawing group on the aniline nitrogen nucleophile, either a cyclopropanation product or dimerization product was obtained chemoselectively. Intramolecular hydroamidation occurred for the same type of propargylic alcohol derivatives when other transition-metal catalysts were employed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Strayer, Megan E; Binz, Jason M; Tanase, Mihaela; Shahri, Seyed Mehdi Kamali; Sharma, Renu; Rioux, Robert M; Mallouk, Thomas E
2014-04-16
Metal nanoparticles are commonly supported on metal oxides, but their utility as catalysts is limited by coarsening at high temperatures. Rhodium oxide and rhodium metal nanoparticles on niobate and tantalate supports are anomalously stable. To understand this, the nanoparticle-support interaction was studied by isothermal titration calorimetry (ITC), environmental transmission electron microscopy (ETEM), and synchrotron X-ray absorption and scattering techniques. Nanosheets derived from the layered oxides KCa2Nb3O10, K4Nb6O17, and RbTaO3 were compared as supports to nanosheets of Na-TSM, a synthetic fluoromica (Na0.66Mg2.68(Si3.98Al0.02)O10.02F1.96), and α-Zr(HPO4)2·H2O. High surface area SiO2 and γ-Al2O3 supports were also used for comparison in the ITC experiments. A Born-Haber cycle analysis of ITC data revealed an exothermic interaction between Rh(OH)3 nanoparticles and the layered niobate and tantalate supports, with ΔH values in the range -32 kJ·mol(-1) Rh to -37 kJ·mol(-1) Rh. In contrast, the interaction enthalpy was positive with SiO2 and γ-Al2O3 supports. The strong interfacial bonding in the former case led to "reverse" ripening of micrometer-size Rh(OH)3, which dispersed as 0.5 to 2 nm particles on the niobate and tantalate supports. In contrast, particles grown on Na-TSM and α-Zr(HPO4)2·H2O nanosheets were larger and had a broad size distribution. ETEM, X-ray absorption spectroscopy, and pair distribution function analyses were used to study the growth of supported nanoparticles under oxidizing and reducing conditions, as well as the transformation from Rh(OH)3 to Rh nanoparticles. Interfacial covalent bonding, possibly strengthened by d-electron acid/base interactions, appear to stabilize Rh(OH)3, Rh2O3, and Rh nanoparticles on niobate and tantalate supports.
Yang, Nuoya; Medford, Andrew J.; Liu, Xinyan; ...
2016-01-31
Synthesis gas (CO + H 2) conversion is a promising route to converting coal, natural gas, or biomass into synthetic liquid fuels. Rhodium has long been studied as it is the only elemental catalyst that has demonstrated selectivity to ethanol and other C 2+ oxygenates. However, the fundamentals of syngas conversion over rhodium are still debated. In this work a microkinetic model is developed for conversion of CO and H 2 into methane, ethanol, and acetaldehyde on the Rh (211) and (111) surfaces, chosen to describe steps and close-packed facets on catalyst particles. The model is based on DFT calculationsmore » using the BEEF-vdW functional. The mean-field kinetic model includes lateral adsorbate–adsorbate interactions, and the BEEF-vdW error estimation ensemble is used to propagate error from the DFT calculations to the predicted rates. The model shows the Rh(211) surface to be ~6 orders of magnitude more active than the Rh(111) surface, but highly selective toward methane, while the Rh(111) surface is intrinsically selective toward acetaldehyde. A variety of Rh/SiO 2 catalysts are synthesized, tested for catalytic oxygenate production, and characterized using TEM. The experimental results indicate that the Rh(111) surface is intrinsically selective toward acetaldehyde, and a strong inverse correlation between catalytic activity and oxygenate selectivity is observed. Furthermore, iron impurities are shown to play a key role in modulating the selectivity of Rh/SiO 2 catalysts toward ethanol. The experimental observations are consistent with the structure-sensitivity predicted from theory. As a result, this work provides an improved atomic-scale understanding and new insight into the mechanism, active site, and intrinsic selectivity of syngas conversion over rhodium catalysts and may also guide rational design of alloy catalysts made from more abundant elements.« less
DOE Office of Scientific and Technical Information (OSTI.GOV)
Yang, Nuoya; Medford, Andrew J.; Liu, Xinyan
Synthesis gas (CO + H 2) conversion is a promising route to converting coal, natural gas, or biomass into synthetic liquid fuels. Rhodium has long been studied as it is the only elemental catalyst that has demonstrated selectivity to ethanol and other C 2+ oxygenates. However, the fundamentals of syngas conversion over rhodium are still debated. In this work a microkinetic model is developed for conversion of CO and H 2 into methane, ethanol, and acetaldehyde on the Rh (211) and (111) surfaces, chosen to describe steps and close-packed facets on catalyst particles. The model is based on DFT calculationsmore » using the BEEF-vdW functional. The mean-field kinetic model includes lateral adsorbate–adsorbate interactions, and the BEEF-vdW error estimation ensemble is used to propagate error from the DFT calculations to the predicted rates. The model shows the Rh(211) surface to be ~6 orders of magnitude more active than the Rh(111) surface, but highly selective toward methane, while the Rh(111) surface is intrinsically selective toward acetaldehyde. A variety of Rh/SiO 2 catalysts are synthesized, tested for catalytic oxygenate production, and characterized using TEM. The experimental results indicate that the Rh(111) surface is intrinsically selective toward acetaldehyde, and a strong inverse correlation between catalytic activity and oxygenate selectivity is observed. Furthermore, iron impurities are shown to play a key role in modulating the selectivity of Rh/SiO 2 catalysts toward ethanol. The experimental observations are consistent with the structure-sensitivity predicted from theory. As a result, this work provides an improved atomic-scale understanding and new insight into the mechanism, active site, and intrinsic selectivity of syngas conversion over rhodium catalysts and may also guide rational design of alloy catalysts made from more abundant elements.« less
Bioenvironmental aspects of europium and rhodium: a selected bibliography
DOE Office of Scientific and Technical Information (OSTI.GOV)
Fore, C.S.; Carrier, R.F.; Talmage, S.S.
This bibliography of 428 abstracted references represents a summary of the domestic and foreign literature relevant to the biological and environmental aspects of europium and rhodium. The collected data are organized by current NAEG interests - research highlighting inventory and distribution of the radionulcides, ecological studies covering terrestrial and aquatic systems, and biological studies in both man and animals. Studies that focus directly on research conducted at specific sites (e.g., the Nevada Test Site) are emphasized throughout the bibliography. (ACR)
Lee, Sung Woo; YU, Mi-Yeon; Baek, Seon Ha; Ahn, Shin-Young; Kim, Sejoong; Na, Ki Young; Chae, Dong-Wan; Chin, Ho Jun
2016-01-01
Background and Objectives There has been little published information on risk factors for poor long-term outcome in adult biopsy-proven minimal change disease (MCD). Methods Data from sixty-three adult, biopsy-proven primary MCD patients treated at a tertiary university hospital between 2003 and 2013 were analyzed. Baseline clinical and pathologic factors were assessed for the associations with composite outcome of creatinine doubling, end stage renal disease, or all-cause mortality. Results During a median (interquartile) 5.0 (2.8–5.0) years, the composite outcome occurred in 11.1% (7/63) of patients. The rate of glomerular immune deposits was 23.8% (15/63). Patients with glomerular immune deposits showed a significantly lower urine protein creatinine ratio than those without deposits (P = 0.033). The rate of non-responders was significantly higher in patients with glomerular immune deposits than in those without deposits (P = 0.033). In patients with deposits, 26.7% (4/15) developed the composite outcome, while only 6.3% (3/48) developed the composite outcome among those without deposits (P = 0.049). In multivariate Cox proportional hazards regression analysis, the presence of glomerular immune deposits was the only factor associated with development of the composite outcome (hazard ratio: 2.310, 95% confidence interval: 1.031–98.579, P = 0.047). Conclusion Glomerular immune deposits were associated with increased risk of a composite outcome in adult MCD patients. The higher rate of non-responders in patients with deposits might be related to the poor outcome. Future study is needed. PMID:26799663
Jaźwiński, Jarosław; Sadlej, Agnieszka
2013-10-01
The complexation of rhodium(II) tetraacetate, tetrakistrifluoroaceate and tetrakisoctanoate with a set of diamines (ethane-1,diamine, propane-1,3-diamine and nonane-1,9-diamine) and their N,N'-dimethyl and N,N,N',N'-tetramethyl derivatives in chloroform solution has been investigated by (1) H and (13) C NMR spectroscopy and density functional theory (DFT) modelling. A combination of two bifunctional reagents, diamines and rhodium(II) tetracarboxylates, yielded insoluble coordination polymers as main products of complexation and various adducts in the solution, being in equilibrium with insoluble material. All diamines initially formed the 2 : 1 (blue), (1 : 1)n oligomeric (red) and 1 : 2 (red) axial adducts in solution, depending on the reagents' molar ratio. Adducts of primary and secondary diamines decomposed in the presence of ligand excess, the former via unstable equatorial complexes. The complexation of secondary diamines slowed down the inversion at nitrogen atoms in NH(CH3 ) functional groups and resulted in the formation of nitrogenous stereogenic centres, detectable by NMR. Axial adducts of tertiary diamines appeared to be relatively stable. The presence of long aliphatic chains in molecules (adducts of nonane-1,9-diamines or rhodium(II) tetrakisoctanoate) increased adduct solubility. Hypothetical structures of the equatorial adduct of rhodium(II) tetraacetate with ethane-1,2-diamine and their NMR parameters were explored by means of DFT calculations. Copyright © 2013 John Wiley & Sons, Ltd.
Zientek, Michael L.
2012-01-01
Layered, ultramafic to mafic intrusions are uncommon in the geologic record, but host magmatic ore deposits containing most of the world's economic concentrations of platinum-group elements (PGE) (figs. 1 and 2). These deposits are mined primarily for their platinum, palladium, and rhodium contents (table 1). Magmatic ore deposits are derived from accumulations of crystals of metallic oxides, or immiscible sulfide, or oxide liquids that formed during the cooling and crystallization of magma, typically with mafic to ultramafic compositions. "PGE reefs" are stratabound PGE-enriched lode mineralization in mafic to ultramafic layered intrusions. The term "reef" is derived from Australian and South African literature for this style of mineralization and used to refer to (1) the rock layer that is mineralized and has distinctive texture or mineralogy (Naldrett, 2004), or (2) the PGE-enriched sulfide mineralization that occurs within the rock layer. For example, Viljoen (1999) broadly defined the Merensky Reef as "a mineralized zone within or closely associated with an unconformity surface in the ultramafic cumulate at the base of the Merensky Cyclic Unit." In this report, we will use the term PGE reef to refer to the PGE-enriched mineralization, not the host rock layer. Within a layered igneous intrusion, reef-type mineralization is laterally persistent along strike, extending for the length of the intrusion, typically tens to hundreds of kilometers. However, the mineralized interval is thin, generally centimeters to meters thick, relative to the stratigraphic thickness of layers in an intrusion that vary from hundreds to thousands of meters. PGE-enriched sulfide mineralization is also found near the contacts or margins of layered mafic to ultramafic intrusions (Iljina and Lee, 2005). This contact-type mineralization consists of disseminated to massive concentrations of iron-copper-nickel-PGE-enriched sulfide mineral concentrations in zones that can be tens to hundreds
Tracking the shape-dependent sintering of platinum-rhodium model catalysts under operando conditions
NASA Astrophysics Data System (ADS)
Hejral, Uta; Müller, Patrick; Balmes, Olivier; Pontoni, Diego; Stierle, Andreas
2016-03-01
Nanoparticle sintering during catalytic reactions is a major cause for catalyst deactivation. Understanding its atomic-scale processes and finding strategies to reduce it is of paramount scientific and economic interest. Here, we report on the composition-dependent three-dimensional restructuring of epitaxial platinum-rhodium alloy nanoparticles on alumina during carbon monoxide oxidation at 550 K and near-atmospheric pressures employing in situ high-energy grazing incidence x-ray diffraction, online mass spectrometry and a combinatorial sample design. For platinum-rich particles our results disclose a dramatic reaction-induced height increase, accompanied by a corresponding reduction of the total particle surface coverage. We find this restructuring to be progressively reduced for particles with increasing rhodium composition. We explain our observations by a carbon monoxide oxidation promoted non-classical Ostwald ripening process during which smaller particles are destabilized by the heat of reaction. Its driving force lies in the initial particle shape which features for platinum-rich particles a kinetically stabilized, low aspect ratio.
Synthesis of C60H2 by rhodium-catalyzed hydrogenation of C60
NASA Technical Reports Server (NTRS)
Becker, L.; Evans, T. P.; Bada, J. L.; Miller, S. L. (Principal Investigator)
1993-01-01
Reduction of C60 with rhodium(0) on alumina and hydrogen in deuterated benzene (C6D6) at ambient temperature and pressure yields a mixture of hydrogenated compounds; C60H2 has been characterized as the major product in 14% yield based on 1H NMR.
Rhodium Catalyzed Annulation of N-Benzoylsulfonamide with Isocyanide via C-H Activation
Zhu, Chen; Xie, Weiqing; Falck, John R.
2012-01-01
Isocyanide insertion: the first rhodium-catalyzed annulation of N-benzoylsulfonamide incorporating with isocyanide via C-H activation is described. The transformation is broadly compatible with N-benzoylsulfonamides bearing various electron-properties as well as isocyanides. From practical point of view, this methodology provides the most straightforward approach to a series of 3-(imino)isoindolinones. PMID:21972033
Direct C-H alkylation and indole formation of anilines with diazo compounds under rhodium catalysis.
Mishra, Neeraj Kumar; Choi, Miji; Jo, Hyeim; Oh, Yongguk; Sharma, Satyasheel; Han, Sang Hoon; Jeong, Taejoo; Han, Sangil; Lee, Seok-Yong; Kim, In Su
2015-12-18
The rhodium(III)-catalyzed direct functionalization of aniline C-H bonds with α-diazo compounds is described. These transformations provide a facile construction of ortho-alkylated anilines with diazo malonates or highly substituted indoles with diazo acetoacetates.
Lu, Chong-Dao; Liu, Hui; Chen, Zhi-Yong; Hu, Wen-Hao; Mi, Ai-Qiao
2005-05-28
The rhodium(II)-catalyzed three-component reaction of diazoacetates, titanium alkoxides and aldehydes is shown to give alpha-alkoxyl-beta-hydroxyl acid derivatives; the novel C-C bond formation reaction is proposed to occur through oxonium ylides derived from diazo compounds and titanium alkoxides, and followed by intermolecular trapping by aldehydes.
Kiss, Borbala; Didier, Christophe; Johnson, Timothy; Manning, Troy D; Dyer, Matthew S; Cowan, Alexander J; Claridge, John B; Darwent, James R; Rosseinsky, Matthew J
2014-12-22
A stable visible-light-driven photocatalyst (λ≥450 nm) for water oxidation is reported. Rhodium substitution into the pyrochlore Y2 Ti2 O7 is demonstrated by monitoring Vegard's law evolution of the unit-cell parameters with changing rhodium content, to a maximum content of 3 % dopant. Substitution renders the solid solutions visible-light active. The overall rate of oxygen evolution is comparable to WO3 but with superior light-harvesting and surface-area-normalized turnover rates, making Y2 Ti1.94 Rh0.06 O7 an excellent candidate for use in a Z-scheme water-splitting system. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Kawabata, Hisaya; Koda, Yuki; Sumida, Hirosuke; Shigetsu, Masahiko; Takami, Akihide; Inumaru, Kei
2013-05-11
Rhodium on a La-containing ZrO2 support effectively eliminated NOx from a synthetic auto exhaust gas under fluctuating oxygen conditions. Rhodium particles maintained a low oxidation state on the ZrO2-La2O3 mixed oxide even after treatment with 5% O2 at 773 K, highlighting the significant effect of the La addition.
Park, Kang Hyun; Jung, Il Gu; Kim, So Yeon; Chung, Young Keun
2003-12-25
Reaction of 1,6-enynes with a hydrosilane in the presence of immobilized cobalt/rhodium bimetallic nanoparticles gives 2-methyl-1-silylmethylidene-2-cyclopentanes in the absence of carbon monoxide and 2-formylmethyl-1-silylmethylidene-2-cyclopentanes under 1 atm of carbon monoxide, respectively. [reaction: see text
Atomic-absorption determination of rhodium in chromite concentrates
Schnepfe, M.M.; Grimaldi, F.S.
1969-01-01
Rhodium is determined in chromite concentrates by atomic absorption after concentration either by co-precipitation with tellurium formed by the reduction of tellurite with tin(II) chloride or by fire assay into a gold bead. Interelement interferences in the atomic-absorption determination are removed by buffering the solutions with lanthanum sulphate (lanthanum concentration 1%). Substantial amounts of Ag, Al, Au, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ho, Hg, K, La, Mg, Mn, Mo, Na, Ni, Pb, Te, Ti, V, Y, Zn and platinum metals can be tolerated. A lower limit of approximately 0.07 ppm Rh can be determined in a 3-g sample. ?? 1969.
Rhodium-catalyzed asymmetric aqueous Pauson-Khand-type reaction.
Kwong, Fuk Yee; Li, Yue Ming; Lam, Wai Har; Qiu, Liqin; Lee, Hang Wai; Yeung, Chi Hung; Chan, Kin Shing; Chan, Albert S C
2005-06-20
An interesting rhodium-catalyzed asymmetric aqueous Pauson-Khand-type reaction was developed. A chiral atropisomeric dipyridyldiphosphane ligand was found to be highly effective in this system. This operationally simple protocol allows both catalyst and reactants to be handled under air without precautions. Various enynes were transformed to the corresponding bicyclic cyclopentenones in good yield and enantiomeric excess (up to 95 % ee). A study of the electronic effects of the enyne substrates revealed a correlation between the electronic properties of the substrates and the ee value obtained in the product of the Pauson-Khand-type reaction. A linear free-energy relationship was observed from a Hammett study.
Rhodium-catalysed syn-carboamination of alkenes via a transient directing group.
Piou, Tiffany; Rovis, Tomislav
2015-11-05
Alkenes are the most ubiquitous prochiral functional groups--those that can be converted from achiral to chiral in a single step--that are accessible to synthetic chemists. For this reason, difunctionalization reactions of alkenes (whereby two functional groups are added to the same double bond) are particularly important, as they can be used to produce highly complex molecular architectures. Stereoselective oxidation reactions, including dihydroxylation, aminohydroxylation and halogenation, are well established methods for functionalizing alkenes. However, the intermolecular incorporation of both carbon- and nitrogen-based functionalities stereoselectively across an alkene has not been reported. Here we describe the rhodium-catalysed carboamination of alkenes at the same (syn) face of a double bond, initiated by a carbon-hydrogen activation event that uses enoxyphthalimides as the source of both the carbon and the nitrogen functionalities. The reaction methodology allows for the intermolecular, stereospecific formation of one carbon-carbon and one carbon-nitrogen bond across an alkene, which is, to our knowledge, unprecedented. The reaction design involves the in situ generation of a bidentate directing group and the use of a new cyclopentadienyl ligand to control the reactivity of rhodium. The results provide a new way of synthesizing functionalized alkenes, and should lead to the convergent and stereoselective assembly of amine-containing acyclic molecules.
Shintani, Ryo; Takatsu, Keishi; Hayashi, Tamio
2008-03-20
A nonenzymatic kinetic resolution of tertiary homoallyl alcohols has been developed through a rhodium-catalyzed retro-allylation reaction under simple conditions. Selectivity factors of up to 12 have been achieved by employing (R)-H8-binap as the ligand, and the reaction can be conducted on a preparative scale.
Regioselective syntheses of 1,2-benzothiazines by rhodium-catalyzed annulation reactions.
Cheng, Ying; Bolm, Carsten
2015-10-12
Rhodium-catalyzed directed carbene insertions into aromatic CH bonds of S-aryl sulfoximines lead to intermediates, which upon dehydration provide 1,2-benzothiazines in excellent yields. The domino-type process is regioselective and shows a high functional-group tolerance. It is scalable, and the only by-products are dinitrogen and water. Three illustrative transformations underscore the synthetic value of the products. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
NASA Astrophysics Data System (ADS)
Ibn-Elhaj, M.; Guillon, D.; Skoulios, A.; Giroud-Godquin, A. M.; Marchon, J.-C.
1992-12-01
This paper describes observations of the mesomorphic behaviour of mixtures of rhodium eicosanoate or copper dodecanoate with solvents such as toluene, decahydronaphthalene, and (+) camphene. The mesophase found with these compounds at high temperatures turns from columnar to nematic when the weight fraction of the solvent (toluene, decahydronaphthalene is increased beyond a value of about 50%. The binary phase diagram of the copper compound with toluene was experimentally determined using polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction. The novel feature of the nematic phase is that the basic physical object which align parallel to the nematic director are not individual molecules, but columns of molecules (one-dimensional supramolecular assemblies) which have lost the long-range lateral positional order characteristic of the columnar mesophase. These observations are discussed on the grounds of recent theoretical calculations. Cholesteric-like textures are observed for mixtures of rhodium eicosanoate with the chiral solvent (+) camphene.
Rhodium mediated bond activation: from synthesis to catalysis
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ho, Hung-An
Recently, our lab has developed monoanionic tridentate ligand, To R, showing the corresponding coordination chemistry and catalyst reactivity of magnesium, zirconium, zinc and iridium complexes. This thesis details synthetic chemistry, structural study and catalytic reactivity of the To R-supported rhodium compounds. Tl[To R] has been proved to be a superior ligand transfer agent for synthesizing rhodium complexes. The salt metathesis route of Tl[To M] with [Rh(μ-Cl)(CO)] 2 and [Rh(μ- Cl)(COE)] 2 gives To MRh(CO) 2 (2.2) and To MRhH(β 3-C 8H 13) (3.1) respectively while Tl[To M] with [Rh(μ-Cl)(CO)] 2 affords To PRh(CO) 2 (2.3). 2.2 reacts with both strongmore » and weak electrophiles, resulting in the oxazoline N-attacked and the metal center-attacked compounds correspondingly. Using one of the metal center-attacked electrophiles, 2.3 was demonstrated to give high diastereoselectivity. Parallel to COE allylic C-H activation complex 3.1, the propene and allylbenzene allylic C-H activation products have also been synthesized. The subsequent functionalization attempts have been examined by treating with Brønsted acids, Lewis acids, electrophiles, nucleophiles, 1,3-dipolar reagents and reagents containing multiple bonds able to be inserted. Various related complexes have been obtained under these conditions, in which one of the azide insertion compounds reductively eliminates to give an allylic functionalization product stoichiometrically. 3.1 reacts with various primary alcohols to give the decarbonylation dihydride complex To MRh(H) 2CO (4.1). 4.1 shows catalytic reactivity for primary alcohol decarbonylation under a photolytic condition. Meanwhile, 2.2 has been found to be more reactive than 4.1 for catalytic alcohol decarbonylation under the same condition. Various complexes and primary alcohols have been investigated as well. The proposed mechanism is based on the stochiometric reactions of the possible metal and organic intermediates. Primary amines
Evans, P Andrew; Negru, Daniela E; Shang, Deju
2015-04-13
The development of the stereoselective rhodium-catalyzed [(3+2)+2] carbocyclization of alkynylidenecyclopropanes (ACPs) with substituted allenes is described. This work demonstrates that activated and unactivated allenes preferentially undergo carbometalation at the distal terminus to generate tri- and tetrasubstituted exocyclic olefins with a neutral rhodium catalyst. In addition, this method provides a strategy for the total synthesis of the guaiane family of sesquiterpenes, which are not directly accessible using alkynes as exogenous π-components. Finally, the preparation of the bicyclo[5.4.0]undecane ring system using a homologated ACP tether serves to further illustrate the versatility of this approach. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
NASA Astrophysics Data System (ADS)
Rutkowska, Iwona A.; Koster, Margaretta D.; Blanchard, Gary J.; Kulesza, Pawel J.
2014-12-01
A catalytic material for electrooxidation of ethanol that utilizes PtRu nanoparticles dispersed over thin films of rhodium-free and rhodium-containing zirconia (ZrO2) supports is described here. The enhancement of electrocatalytic activity (particularly in the potential range as low as 0.25-0.5 V vs. RHE), that has been achieved by dispersing PtRu nanoparticles (loading, 100 μg cm-2) over the hybrid Rh-ZrO2 support composed of nanostructured zirconia and metallic rhodium particles, is clearly evident from comparison of the respective voltammetric and chronoamperometric current densities recorded at room temperature (22 °C) in 0.5 mol dm-3 H2SO4 containing 0.5 mol dm-3 ethanol. Porous ZrO2 nanostructures, that provide a large population of hydroxyl groups in acidic medium in the vicinity of PtRu sites, are expected to facilitate the ruthenium-induced removal of passivating CO adsorbates from platinum, as is apparent from the diagnostic experiments with a small organic molecule such as methanol. Although Rh itself does not show directly any activity toward ethanol oxidation, the metal is expected to facilitate C-C bond splitting in C2H5OH. It has also been found during parallel voltammetric and chronoamperometric measurements that the hybrid Rh-ZrO2 support increases activity of the platinum component itself toward ethanol oxidation in the low potential range.
Stereoselective 1,3-Insertions of Rhodium(II) Azavinyl Carbenes
Chuprakov, Stepan; Worrell, Brady T.; Selander, Nicklas; Sit, Rakesh K.; Fokin, Valery V.
2014-01-01
Rhodium(II) azavinyl carbenes, conveniently generated from 1-sulfonyl-1,2,3-triazoles, undergo a facile, mild and convergent formal 1,3-insertion into N–H and O–H bonds of primary and secondary amides, various alcohols, and carboxylic acids to afford a wide range of vicinally bis-functionalized Z-olefins with perfect regio- and stereoselectively. Utilizing the distinctive functionality installed through these reactions, a number of subsequent rearrangements and cyclizations expand the repertoire of valuable organic building blocks constructed by reactions of transition metal carbene complexes, including α-allenyl ketones and amino-substituted heterocycles. PMID:24295389
Chen, Hong-Xue; Kang, Jie; Chang, Rong; Zhang, Yun-Lai; Duan, Hua-Zhen; Li, Yan-Mei; Chen, Yong-Xiang
2018-06-01
A novel and facile synthetic strategy for α,α-difluorinated phosphonate mimetics of phosphoserine/phosphothreonine utilizing rhodium-catalyzed asymmetric hydrogenation was developed. The dehydrogenated substrate β-difluorophosphonomethyl α-(acylamino)acrylates were first prepared from protected serine/threonine followed by asymmetric hydrogenation using the rhodium-DuPhos catalytic system to generate the chiral center(s). These important phosphonate building blocks were successfully incorporated into phosphatase-resistant peptides, which displayed similar inhibition to the 14-3-3 ζ protein as the parent pSer/pThr peptides.
Ureshino, Tomonari; Yoshida, Takuya; Kuninobu, Yoichiro; Takai, Kazuhiko
2010-10-20
The rhodium-catalyzed synthesis of silafluorenes from biphenylhydrosilanes is described. This highly efficient reaction proceeds via both Si-H and C-H bond activation, producing only H(2) as a side product. Using this method, a ladder-type bis-silicon-bridged p-terphenyl could also be synthesized.
Mayr, Monika; Wurst, Klaus; Ongania, Karl-Hans; Buchmeiser, Michael R
2004-03-05
The synthesis of novel 1,3-diaryl- and 1,3-dialkylpyrimidin-2-ylidene-based N-heterocyclic carbenes (NHCs) and their rhodium(i) and palladium(II) complexes is described. The rhodium compounds bromo(cod)[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene]rhodium (7), bromo(cod)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)rhodium (8) (cod=eta(4)-1,5-cyclooctadiene, mesityl=2,4,6-trimethylphenyl), chloro(cod)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)rhodium (9), and chloro(cod)[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene]rhodium (10) were prepared by reaction of [[Rh(cod)Cl](2)] with lithium tert-butoxide followed by addition of 1,3-dimesityl-3,4,5,6-tetrahydropyrimidinium bromide (3), 1,3-dimesityl-3,4,5,6-tetrahydropyrimidinium tetrafluoroborate (4), 1,3-di-2-propyl-3,4,5,6-tetrahydropyrimidinium bromide (6), and 1,3-di-2-propyl-3,4,5,6-tetrahydropyrimidinium tetrafluoroborate, respectively. Complex 7 crystallizes in the monoclinic space group P2(1)/n, and 8 in the monoclinic space group P2(1). Complexes 9 and 10 were used for the synthesis of the corresponding dicarbonyl complexes dicarbonylchloro(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)rhodium (11), and dicarbonylchloro[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene]rhodium (12). The wavenumbers nu(CO I)/nu(CO II) for 11 and 12 were used as a quantitative measure for the basicity of the NHC ligand. The values of 2062/1976 and 2063/1982 cm(-1), respectively, indicate that the new NHCs are among the most basic cyclic ligands reported so far. Compounds 3 and 6 were additionally converted to the corresponding cationic silver(i) bis-NHC complexes [Ag(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(2)]AgBr(2) (13) and [Ag[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene](2)]AgBr(2) (14), which were subsequently used in transmetalation reactions for the synthesis of the corresponding palladium(II) complexes Pd(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2
Yang, Yuan; Zhou, Ming-Bo; Ouyang, Xuan-Hui; Pi, Rui; Song, Ren-Jie; Li, Jin-Heng
2015-05-26
A rhodium(III)-catalyzed [3+2]/[5+2] annulation of 4-aryl 1-tosyl-1,2,3-triazoles with internal alkynes is presented. This transformation provides straightforward access to indeno[1,7-cd]azepine architectures through a sequence involving the formation of a rhodium(III) azavinyl carbene, dual C(sp(2))-H functionalization, and [3+2]/[5+2] annulation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Liu, Li-Juan; Lin, Sheng; Chan, Daniel Shiu-Hin; Vong, Chi Teng; Hoi, Pui Man; Wong, Chun-Yuen; Ma, Dik-Lung; Leung, Chung-Hang
2014-11-01
Metal-containing complexes have arisen as viable alternatives to organic molecules as therapeutic agents. Metal complexes possess a number of advantages compared to conventional carbon-based compounds, such as distinct geometries, interesting electronic properties, variable oxidation states and the ability to arrange different ligands around the metal centre in a precise fashion. Meanwhile, nitric oxide (NO) plays key roles in the regulation of angiogenesis, vascular permeability and inflammation. We herein report a novel cyclometalated rhodium(III) complex as an inhibitor of lipopolysaccharides (LPS)-induced NO production in RAW264.7 macrophages. Experiments suggested that the inhibition of NO production in cells by complex 1 was mediated through the down-regulation of nuclear factor-κB (NF-κB) activity. Furthermore, complex 1 inhibited angiogenesis in human umbilical vein endothelial cells (HUVECs) as revealed by an endothelial tube formation assay. This study demonstrates that kinetically inert rhodium(III) complexes may be potentially developed as effective anti-angiogenic agents. Copyright © 2014 Elsevier Inc. All rights reserved.
Oonishi, Yoshihiro; Yokoe, Takayuki; Hosotani, Akihito; Sato, Yoshihiro
2014-01-20
Rhodium(I)-catalyzed cyclization of allenynes with a tethered carbonyl group was investigated. An unusual insertion of a CO bond into the C(sp(2) )-rhodium bond of a rhodacycle intermediate occurs via a highly strained transition state. Direct reductive elimination from the obtained rhodacyle intermediate proceeds to give a tricyclic product containing an 8-oxabicyclo[3.2.1]octane skeleton, while β-hydride elimination from the same intermediate gives products that contain fused five- and seven-membered rings in high yields. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Altering properties of cerium oxide thin films by Rh doping
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ševčíková, Klára, E-mail: klarak.sevcikova@seznam.cz; NIMS Beamline Station at SPring-8, National Institute for Materials Science, Sayo, Hyogo 679-5148; Nehasil, Václav, E-mail: nehasil@mbox.troja.mff.cuni.cz
2015-07-15
Highlights: • Thin films of ceria doped by rhodium deposited by RF magnetron sputtering. • Concentration of rhodium has great impact on properties of Rh–CeO{sub x} thin films. • Intensive oxygen migration in films with low concentration of rhodium. • Oxygen migration suppressed in films with high amount of Rh dopants. - Abstract: Ceria containing highly dispersed ions of rhodium is a promising material for catalytic applications. The Rh–CeO{sub x} thin films with different concentrations of rhodium were deposited by RF magnetron sputtering and were studied by soft and hard X-ray photoelectron spectroscopies, Temperature programmed reaction and X-ray powder diffractionmore » techniques. The sputtered films consist of rhodium–cerium mixed oxide where cerium exhibits a mixed valency of Ce{sup 4+} and Ce{sup 3+} and rhodium occurs in two oxidation states, Rh{sup 3+} and Rh{sup n+}. We show that the concentration of rhodium has a great influence on the chemical composition, structure and reducibility of the Rh–CeO{sub x} thin films. The films with low concentrations of rhodium are polycrystalline, while the films with higher amount of Rh dopants are amorphous. The morphology of the films strongly influences the mobility of oxygen in the material. Therefore, varying the concentration of rhodium in Rh–CeO{sub x} thin films leads to preparing materials with different properties.« less
Bai, Huiping; Xiong, Caiyun; Wang, Chunqiong; Liu, Peng; Dong, Su; Cao, Qiue
2018-05-01
A rhodium (III) ion carbon paste electrode (CPE) based on an ion imprinted polymer (IIP) as a new modifying agent has been prepared and studied. Rh(III) ion imprinted polymer was synthesized by copolymerization of acrylamide-Rh(III) complex and ethylene glycol dimethacrylate according to the precipitation polymerization. Acrylamide acted as both functional monomer and complexing agent to create selective coordination sites in a cross-linked polymer. The ion imprinted carbon paste electrode (IIP-CPE) was prepared by mixing rhodium IIP-nanoparticles and graphite powder in n-eicosane as an adhesive and then embedding them in a Teflon tube. Amperometric i-t curve method was applied as the determination technique. Several parameters, including the functional monomer, molar ratio of template, monomer and cross-linking agent, the amounts of IIP, the applied potential, the buffer solution and pH have been studied. According to the results, IIP-CPE showed a considerably higher response in comparison with the electrode embedded with non-imprinted polymer (NIP), indicating the formation of suitable recognition sites in the IIP structure during the polymerization stage. The introduced electrode showed a linear range of 1.00×10-8~3.0×10-5 mol·L-1 and detection limit of 6.0 nmol L-1 (S/N = 3). The IIP-CPE was successfully applied for the trace rhodium determination in catalyst and plant samples with RSD of less than 3.3% (n = 5) and recoveries in the range of 95.5~102.5%.
Rhodium-catalyzed asymmetric hydrogenation of unprotected NH imines assisted by a thiourea.
Zhao, Qingyang; Wen, Jialin; Tan, Renchang; Huang, Kexuan; Metola, Pedro; Wang, Rui; Anslyn, Eric V; Zhang, Xumu
2014-08-04
Asymmetric hydrogenation of unprotected NH imines catalyzed by rhodium/bis(phosphine)-thiourea provided chiral amines with up to 97% yield and 95% ee. (1)H NMR studies, coupled with control experiments, implied that catalytic chloride-bound intermediates were involved in the mechanism through a dual hydrogen-bonding interaction. Deuteration experiments proved that the hydrogenation proceeded through a pathway consistent with an imine. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Rhodium doped InGaAs: A superior ultrafast photoconductor
NASA Astrophysics Data System (ADS)
Kohlhaas, R. B.; Globisch, B.; Nellen, S.; Liebermeister, L.; Schell, M.; Richter, P.; Koch, M.; Semtsiv, M. P.; Masselink, W. T.
2018-03-01
The properties of rhodium (Rh) as a deep-level dopant in InGaAs lattice matched to InP grown by molecular beam epitaxy are investigated. When InGaAs:Rh is used as an ultrafast photoconductor, carrier lifetimes as short as 100 fs for optically excited electrons are measured. Rh doping compensates free carriers so that a near intrinsic carrier concentration can be achieved. At the same time, InGaAs:Rh exhibits a large electron mobility of 1000 cm2/V s. Therefore, this material is a very promising candidate for application as a semi-insulating layer, THz antenna, or semiconductor saturable absorber mirror.
Rhodium-catalyzed asymmetric hydroboration of γ,δ-unsaturated amide derivatives: δ-borylated amides.
Hoang, G L; Zhang, S; Takacs, J M
2018-05-08
γ,δ-Unsaturated amides in which the alkene moiety bears an aryl or heteroaryl substituent undergo regioselective rhodium-catalyzed δ-borylation by pinacolborane to afford chiral secondary benzylic boronic esters. The results contrast the γ-borylation of γ,δ-unsaturated amides in which the disubstituted alkene moiety bears only alkyl substituents; the reversal in regiochemistry is coupled with a reversal in the sense of π-facial selectivity.
Hua, Yuanda; Nguyen, Hiep H; Scaggs, William R; Jeon, Junha
2013-07-05
Ligand-controlled, norbornene-mediated, regio- and diastereoselective rhodium-catalyzed intramolecular alkene hydrosilylation of homoallyl silyl ethers (1) exploiting either BINAP or 1,6-bis(diphenylphosphino)hexane (dpph) has been developed. This method permits selective access to either trans-oxasilacyclopentanes (trans-2) or oxasilacyclohexanes (3) at will. A substoichiometric amount of norbornene markedly increased both yield and selectivity. A norbornene-mediated hydride shuttle process is discussed.
Enantioselective Rhodium Enolate Protonations. A New Methodology for the Synthesis of β2-Amino Acids
Sibi, Mukund P.; Tatamidani, Hiroto; Patil, Kalyani
2008-01-01
Rhodium catalyzed conjugate addition of an aryl boronic acid to α-methylamino acrylates followed by enantioselective protonation of the oxa-π-allylrhodium intermediate provides access to aryl substituted β2-amino acids. The impact of the different variables of the reaction on the levels of enantioselectivity has been assessed. PMID:15957893
Andrew Evans, P.; Sawyer, James R.; Lai, Kwong Wah; Huffman, John C.
2006-01-01
The crossed intermolecular rhodium-catalyzed [2 + 2 + 2] carbocyclization of carbon and heteroatom tethered 1,6-enynes can be accomplished with symmetrical and unsymmetrical alkynes, to afford the corresponding bicyclohexadienes in an efficient and highly selective manner. PMID:16075089
Miura, Tomoya; Tanaka, Takamasa; Matsumoto, Kohei; Murakami, Masahiro
2014-12-01
Relay actions of copper, rhodium, and gold formulate a one-pot multistep pathway, which directly gives 2,5-dihydropyrroles starting from terminal alkynes, sulfonyl azides, and propargylic alcohols. Initially, copper-catalyzed 1,3-dipolar cycloaddition of terminal alkynes with sulfonyl azides affords 1-sulfonyl-1,2,3-triazoles, which then react with propargylic alcohols under the catalysis of rhodium. The resulting alkenyl propargyl ethers subsequently undergo the thermal Claisen rearrangement to give α-allenyl-α-amino ketones. Finally, a gold catalyst prompts 5-endo cyclization to produce 2,5-dihydropyrroles. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Shang, Hai; Wang, Yuanhao; Tian, Yu; Feng, Juan; Tang, Yefeng
2014-05-26
The first rhodium(II)-catalyzed aza-[4+3] cycloadditions of 1-sulfonyl 1,2,3-triazoles with 1,3-dienes have been developed, and enable the efficient synthesis of highly functionalized 2,5-dihydroazepines from readily available precursors. In some cases, the reaction pathway could divert to formal aza-[3+2] cycloadditions, thus leading to 2,3-dihydropyrroles. In this context, the titled reaction represents a capable tool for the divergent synthesis of two types of synthetically valuable aza-heterocycles from common rhodium(II) iminocarbene intermediates. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Baik, Mu-Hyun; Mazumder, Shivnath; Ricci, Paolo; Sawyer, James R; Song, Ye-Geun; Wang, Huijun; Evans, P Andrew
2011-05-25
The computational analysis of the rhodium-catalyzed Pauson-Khand reaction indicates that the key transition state is highly charge-polarized, wherein different diastereoisomers have distinctively different charge polarization patterns. Experimental studies demonstrate that chloro-enynes provide the optimal σ-electron-withdrawing group to promote polarization and thereby reduce the activation barrier to provide a highly diastereoselective reaction at room temperature.
Rhodium-catalyzed chemo-, regio-, and enantioselective addition of 2-pyridones to terminal allenes.
Li, Changkun; Kähny, Matthias; Breit, Bernhard
2014-12-08
A rhodium-catalyzed chemo-, regio-, and enantioselective addition of 2-pyridones to terminal allenes to give branched N-allyl 2-pyridones is reported. Preliminary mechanistic studies support the hypothesis that the reaction was initiated from the more acidic 2-hydroxypyridine form, and the initial kinetic O-allylation product was finally converted into the thermodynamically more stable N-allyl 2-pyridones. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Oehninger, Luciano; Küster, Laura Nadine; Schmidt, Claudia; Muñoz-Castro, Alvaro; Prokop, Aram; Ott, Ingo
2013-12-23
Rhodium(I) complexes bearing N-heterocyclic carbene (NHC) ligands have been widely used in catalytic chemistry, but there are very few reports of biological properties of these organometallics. A series of Rh(I)-NHC derivatives with 1,5-cyclooctadiene and CO as secondary ligands were synthesized, characterized, and biologically investigated as prospective antitumor drug candidates. Pronounced antiproliferative effects were noted for all complexes, along with moderate inhibitory activity of thioredoxin reductase (TrxR) and efficient binding to biomolecules (DNA, albumin). Biodistribution studies showed that the presence of albumin lowered the cellular uptake and confirmed the transport of rhodium into the nuclei. Changes in the mitochondrial membrane potential (MMP) were observed as well as DNA fragmentation in wild-type and daunorubicin- or vincristine-resistant Nalm-6 leukemia cells. Overall, these studies indicated that Rh(I)-NHC fragments could be used as partial structures of new antitumor agents, in particular in those drugs designed to address resistant malignant tissues. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Hydrolysis of Letrozole catalyzed by macrocyclic Rhodium (I) Schiff-base complexes.
Reddy, P Muralidhar; Shanker, K; Srinivas, V; Krishna, E Ravi; Rohini, R; Srikanth, G; Hu, Anren; Ravinder, V
2015-03-15
Ten mononuclear Rhodium (I) complexes were synthesized by macrocyclic ligands having N4 and N2O2 donor sites. Square planar geometry is assigned based on the analytical and spectral properties for all complexes. Rh(I) complexes were investigated as catalysts in hydrolysis of Nitrile group containing pharmaceutical drug Letrozole. A comparative study showed that all the complexes are efficient in the catalysis. The percent yields of all the catalytic reaction products viz. drug impurities were determined by spectrophotometric procedures and characterized by spectral studies. Copyright © 2014 Elsevier B.V. All rights reserved.
Methoxy-Directed Aryl-to-Aryl 1,3-Rhodium Migration
Zhang, Jing; Liu, Jun-Feng; Ugrinov, Angel; Pillai, Anthony F. X.; Sun, Zhong-Ming; Zhao, Pinjing
2015-01-01
Through-space metal/hydrogen shift is an important strategy for transition metal-catalyzed C-H bond activation. Here we describe the synthesis and characterization of a Rh(I) 2,6-dimethoxybenzoate complex that underwent stoichiometric rearrangement via a highly unusual 1,3- rhodium migration. This aryl-to-aryl 1,3-Rh/H shift was also demonstrated in a Rh(I)-catalyzed decarboxylative conjugate addition to form a C-C bond at a meta position instead of the ipso-carboxyl position. A deuterium-labeling study under the conditions of Rh(I)-catalyzed protodecarboxylation revealed the involvement of an ortho-methoxy group in a multi-step pathway of consecutive sp3 and sp2 C-H bond activations. PMID:24171626
Choi, Isaac; Chun, Supill; Chung, Young Keun
2017-12-01
A cobalt-rhodium heterobimetallic nanoparticle (Co 2 Rh 2 /C)-catalyzed tandem reductive amination of aldehydes with nitroaromatics to sec-amines has been developed. The tandem reaction proceeds without any additives under mild conditions (1 atm H 2 and 25 °C). This procedure can be scaled up to the gram scale, and the catalyst can be reused more than six times without loss of activity.
The solubility of hydrogen in rhodium, ruthenium, iridium and nickel.
NASA Technical Reports Server (NTRS)
Mclellan, R. B.; Oates, W. A.
1973-01-01
The temperature variation of the solubility of hydrogen in rhodium, ruthenium, iridium, and nickel in equilibrium with H2 gas at 1 atm pressure has been measured by a technique involving saturating the solvent metal with hydrogen, quenching, and analyzing in resultant solid solutions. The solubilities determined are small (atom fraction of H is in the range from 0.0005 to 0.00001, and the results are consistent with the simple quasi-regular model for dilute interstitial solid solutions. The relative partial enthalpy and excess entropy of the dissolved hydrogen atoms have been calculated from the solubility data and compared with well-known correlations between these quantities.
Srivastava, Ravi; Moneuse, Raphaël; Petit, Julien; Pavard, Paul-Alexis; Dardun, Vincent; Rivat, Madleen; Schiltz, Pauline; Solari, Marius; Jeanneau, Erwann; Veyre, Laurent; Thieuleux, Chloé; Quadrelli, Elsje Alessandra; Camp, Clément
2018-03-20
The straightforward synthesis of a new unsymmetrical hydroxy-tethered N-heterocyclic carbene (NHC) ligand, HL, is presented. The free ligand exhibits an unusual OH-carbene hydrogen-bonding interaction. This OH-carbene motif was used to yield 1) the first tantalum complex displaying both a Fischer- and Schrock-type carbene ligand and 2) a unique NHC-based early/late heterobimetallic complex. More specifically, the protonolysis chemistry between the ligand's hydroxy group and imido-alkyl or alkylidene-alkyl tantalum precursor complexes yielded the rare monometallic tantalum-NHC complexes [Ta(XtBu)(L)(CH 2 tBu) 2 ] (X=N, CH), in which the alkoxy-carbene ligand acts as a chelate. In contrast, HL only binds to rhodium through the NHC unit in [Rh(HL)(cod)Cl] (cod=cycloocta-1,5-diene), the hydroxy pendant arm remaining unbound. This bifunctional ligand scaffold successfully promoted the assembly of rhodium/tantalum heterobimetallic complexes upon either 1) the insertion of [Rh(cod)Cl] 2 into the Ta-NHC bond in [Ta(NtBu)(L)(CH 2 tBu) 2 ] or 2) protonolysis between the free hydroxy group in [Rh(HL)(cod)Cl] and one alkyl group in [Ta(NtBu)(CH 2 tBu) 3 ]. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Huang, Ji-Rong; Song, Qiang; Zhu, Yu-Qin; Qin, Liu; Qian, Zhi-Yong; Dong, Lin
2014-12-15
An efficient rhodium(III)-catalyzed tandem three-component reaction of imines, alkynes and aldehydes through CH activation has been developed. High stereo- and regioselectivity, as well as good yields were obtained in most cases. The simple and atom-economical approach offers a broad scope of substrates, providing polycyclic skeletons with potential biological properties. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Podiform chromite deposits--database and grade and tonnage models
Mosier, Dan L.; Singer, Donald A.; Moring, Barry C.; Galloway, John P.
2012-01-01
Chromite ((Mg, Fe++)(Cr, Al, Fe+++)2O4) is the only source for the metallic element chromium, which is used in the metallurgical, chemical, and refractory industries. Podiform chromite deposits are small magmatic chromite bodies formed in the ultramafic section of an ophiolite complex in the oceanic crust. These deposits have been found in midoceanic ridge, off-ridge, and suprasubduction tectonic settings. Most podiform chromite deposits are found in dunite or peridotite near the contact of the cumulate and tectonite zones in ophiolites. We have identified 1,124 individual podiform chromite deposits, based on a 100-meter spatial rule, and have compiled them in a database. Of these, 619 deposits have been used to create three new grade and tonnage models for podiform chromite deposits. The major podiform chromite model has a median tonnage of 11,000 metric tons and a mean grade of 45 percent Cr2O3. The minor podiform chromite model has a median tonnage of 100 metric tons and a mean grade of 43 percent Cr2O3. The banded podiform chromite model has a median tonnage of 650 metric tons and a mean grade of 42 percent Cr2O3. Observed frequency distributions are also given for grades of rhodium, iridium, ruthenium, palladium, and platinum. In resource assessment applications, both major and minor podiform chromite models may be used for any ophiolite complex regardless of its tectonic setting or ophiolite zone. Expected sizes of undiscovered podiform chromite deposits, with respect to degree of deformation or ore-forming process, may determine which model is appropriate. The banded podiform chromite model may be applicable for ophiolites in both suprasubduction and midoceanic ridge settings.
Metallogenic evolution of uranium deposits in the Middle East and North Africa deposits
NASA Astrophysics Data System (ADS)
Howari, Fares; Goodell, Philip; Salman, Abdulaty
2016-02-01
This paper is briefly involved in classification and distributions of the Middle East and North Africa (MENA) uranium deposits. The study of these mineral systems can significantly contribute to our further understanding of the metallogeny of known and poorly explored deposits. This provides contribution to, and further enhancement of, current classifications and metallogenic models of uranium systems, allowing researchers to emphasize on unknown or poorly studied mineral systems found in MENA. The present study identified eight metallogenic types of uranium associated with: 1) the Archean rocks and intra-cratonic basins, 2) the Pan-African granites and rhyolites which are characterized by igneous activity, 3) Phanerozoic (Paleozoic) clastics, these deposits are the sedimentological response to Pan African magmatism, 4) Mesozoic (basal) clastics type e.g. Nubia sandstones which are characterized by uranium minerals, 5) regional sedimentary phosphate deposits which are categorized as geosynclinal, or continental margin deposits, on the shelf of the Tethys Ocean, 6) Cenozoic Intracratonic Felsic Magmatism of the Tibesti and Hoggar, and the sandstone U deposits of adjoining Niger. These are similar to the Pan-African magmatism metallogenic, 7) Calcretes, and 8) Resistate minerals which are often enriched in rare earth elements, sometimes including uranium. They are thus sometimes considered as U resources but poorly explored in the MENA region. These metallogenic types are described and discussed in the current paper.
Guan, Yu-Qing; Gao, Min; Deng, Xu; Lv, Hui; Zhang, Xumu
2017-07-18
A rhodium-catalyzed asymmetric hydrogenation of challenging tetrasubstituted β-acetoxy-α-enamido esters was developed, giving chiral β-acetoxy-α-amido esters in high yields with excellent enantioselectivities (up to >99% ee). The products could be easily transformed to β-hydroxy-α-amino acid derivatives which are valuable chiral building blocks and a novel route for the synthesis of droxidopa was also developed.
Ishida, Naoki; Nečas, David; Masuda, Yusuke; Murakami, Masahiro
2015-06-15
3-Hydroxypiperidine scaffolds were enantioselectively constructed in an atom-economical way by sequential action of light and rhodium upon N-allylglyoxylamides. In a formal sense, the allylic C-H bond was selectively cleaved and enantioselectively added across the ketonic carbonyl group with migration of the double bond (carbonyl-ene-type reaction). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Sambasivan, Ramya; Ball, Zachary T
2012-08-20
Searching with a beady eye: A high-throughput, on-bead screen of rhodium metallopeptide catalysts was developed in a 96-well format for asymmetric cyclopropanation. Different sequences of natural L-amino acids have been identified that produce opposite product enantiomers. In addition to styrene derivatives, high enantioselectivity is observed for vinyl ether and vinyl amine derivatives. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Liu, Huan; Song, Shengjin; Wang, Cheng-Qiang; Feng, Chao; Loh, Teck-Peng
2017-01-10
A synthetic protocol for the expedient construction of 5-methylene-1H-pyrrol-2(5H)-one derivatives through rhodium-catalyzed [4+1] annulation with gem-difluoroacrylate as the C 1 component was reported. By taking advantage of the twofold C-F bond cleavage occurring during the annulation, this reaction not only allows the synthesis of these heterocyclic compounds under overall oxidant-free conditions but also renders the transformation stereospecific. The very mild reaction conditions employed ensure compatibility with a wide variety of synthetically useful functional groups. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Lian, Yajing; Davies, Huw M. L.
2010-01-01
An unusual rhodium-carbenoid approach for introduction of 4-substituted (Z)-pent-2-enoates into sterically encumbered pyrroles and indoles is described. These studies show that (Z)-vinylcarbenoids have a greater tendency than (E)-vinylcarbenoids to react at the vinylogous position of the carbenoid rather than at the carbenoid center. PMID:20121078
Equilenin acetate and dihydroequilenin acetate were oxidized with iodosobenzene and a rhodium(III) porphyrin catalyst. The selectivity of the reactions differs from that with the corresponding Mn(III) catalyst, or from that of free radical chain oxidation.
Conclusive evidence on the mechanism of the rhodium-mediated decyanative borylation.
Esteruelas, Miguel A; Oliván, Montserrat; Vélez, Andrea
2015-09-30
The stoichiometric reactions proposed in the mechanism of the rhodium-mediated decyanative borylation have been performed and all relevant intermediates isolated and characterized including their X-ray structures. Complex RhCl{xant(P(i)Pr2)2} (1, xant(P(i)Pr2)2 = 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene) reacts with bis(pinacolato)diboron (B2pin2), in benzene, to give the rhodium(III) derivative RhHCl(Bpin){xant(P(i)Pr2)2} (4) and PhBpin. The reaction involves the oxidative addition of B2pin2 to 1 to give RhCl(Bpin)2{xant(P(i)Pr2)2}, which eliminates ClBpin generating Rh(Bpin){xant(P(i)Pr2)2} (2). The reaction of the latter with the solvent yields PhBpin and the monohydride RhH{xant(P(i)Pr2)2} (6), which adds the eliminated ClBpin. Complex 4 and its catecholboryl counterpart RhHCl(Bcat){xant(P(i)Pr2)2} (7) have also been obtained by oxidative addition of HBR2 to 1. Complex 2 is the promoter of the decyanative borylation. Thus, benzonitrile and 4-(trifluoromethyl)benzonitrile insert into the Rh-B bond of 2 to form Rh{C(R-C6H4)═NBpin}{xant(P(i)Pr2)2} (R = H (8), p-CF3 (9)), which evolve into the aryl derivatives RhPh{xant(P(i)Pr2)2} (3) and Rh(p-CF3-C6H4){xant(P(i)Pr2)2} (10), as a result of the extrusion of CNBpin. The reactions of 3 and 10 with B2pin2 yield the arylBpin products and regenerate 2.
Best, Daniel; Burns, David J; Lam, Hon Wai
2015-01-01
A commercially available rhodium(II) complex catalyzes the direct arylation of 5-diazobarbituric acids with arenes, allowing straightforward access to 5-aryl barbituric acids. Free N—H groups are tolerated on the barbituric acid, with no complications arising from N—H insertion processes. This method was applied to the concise synthesis of a potent matrix metalloproteinase (MMP) inhibitor. PMID:25959544
Yu, Yue-Na; Xu, Ming-Hua
2013-03-15
Enantioselective synthesis of potentially useful chiral 3-aryl-1-indanones was achieved through a rhodium-catalyzed asymmetric intramolecular 1,4-addition of pinacolborane chalcone derivatives using extraordinary simple MonoPhos as chiral ligand under relatively mild conditions. This novel protocol offers an easy access to a wide variety of enantioenriched 3-aryl-1-indanone derivatives in high yields (up to 95%) with excellent enantioselectivities (up to 95% ee).
In the presence of a rhodium catalyst, ,
-unsaturated est...
Peng, Shiyong; Liu, Suna; Zhang, Sai; Cao, Shengyu; Sun, Jiangtao
2015-10-16
Polyheteroaromatic compounds are potential optoelectronic conjugated materials due to their electro- and photochemical properties. Transition-metal-catalyzed multiple C-H activation and sequential oxidative annulation allows rapidly assembling of those compounds from readily available starting materials. A rhodium-catalyzed cascade oxidative annulation of β-enamino esters or 4-aminocoumarins with internal alkynes is described to access those compounds, featuring multiple C-H/N-H bond cleavages and sequential C-C/C-N bond formations in one pot.
Page, Norman J; Riley, Leonard Benjamin; Haffty, Joseph
1969-01-01
Analyses by a combination fire- assay-solution-optical-emission spectrographic method of 137 rocks from the Stillwater Complex, Mont., indicate that platinum, palladium, and rhodium are preferentially concentrated in chromitite zones. The A chromitite zone (21 samples) has an average of 988.9 ppb (pans per billion, 10-9) Pt, 2290.2 ppb Pd, and 245.9 ppb Rh and reaches a maximum (to date) of 8,000 ppb Pt, 11,000 ppb Pd, and 1,700 ppb Rh.
Kubis, Christoph; Sawall, Mathias; Block, Axel; Neymeyr, Klaus; Ludwig, Ralf; Börner, Armin; Selent, Detlef
2014-09-08
The influence of carbon monoxide concentration on the kinetics of the hydroformylation of 3,3-dimethyl-1-butene with a phosphite-modified rhodium catalyst has been studied for the pressure range p(CO)=0.20-3.83 MPa. Highly resolved time-dependent concentration profiles of the organometallic intermediates were derived from IR spectroscopic data collected in situ for the entire olefin-conversion range. The dynamics of the catalyst and organic components are described by enzyme-type kinetics with competitive and uncompetitive inhibition reactions involving carbon monoxide taken into account. Saturation of the alkyl-rhodium intermediates with carbon monoxide as a cosubstrate occurs between 1.5 and 2 MPa of carbon monoxide pressure, which brings about a convergence of aldehyde regioselectivity. Hydrogenolysis of the acyl intermediate is fast at 30 °C and low pressure of p(CO)=0.2 MPa, but is of minus first order with respect to the solution concentration of carbon monoxide. Resting 18-electron hydrido and acyl complexes that correspond to early and late rate-determining states, respectively, coexist as long as the conversion of the substrate is not complete. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Enantioselective Access to Spirocyclic Sultams by Chiral Cp(x) -Rhodium(III)-Catalyzed Annulations.
Pham, Manh V; Cramer, Nicolai
2016-02-12
Chiral spirocyclic sultams are a valuable compound class in organic and medicinal chemistry. A rapid entry to this structural motif involves a [3+2] annulation of an N-sulfonyl ketimine and an alkyne. Although the directing-group properties of the imino group for C-H activation have been exploited, the developments of related asymmetric variants have remained very challenging. The use of rhodium(III) complexes equipped with a suitable atropchiral cyclopentadienyl ligand, in conjunction with a carboxylic acid additive, enables an enantioselective and high yielding access to such spirocyclic sultams. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Ekengard, Erik; Kumar, Kamlesh; Fogeron, Thibault; de Kock, Carmen; Smith, Peter J; Haukka, Matti; Monari, Magda; Nordlander, Ebbe
2016-03-07
The synthesis and characterization of twenty new pentamethylcyclopentadienyl-rhodium and iridium complexes containing N^N and N^O-chelating chloroquine analogue ligands are described. The in vitro antimalarial activity of the new ligands as well as the complexes was evaluated against the chloroquine sensitive (CQS) NF54 and the chloroquine resistant (CQR) Dd2 strains of Plasmodium falciparum. The antimalarial activity was found to be good to moderate; although all complexes are less active than artesunate, some of the ligands and complexes showed better activity than chloroquine (CQ). In particular, rhodium complexes were found to be considerably more active than iridium complexes against the CQS NF54 strain. Salicylaldimine Schiff base ligands having electron-withdrawing groups (F, Cl, Br, I and NO2) in para position of the salicyl moiety and their rhodium complexes showed good antiplasmodial activity against both the CQS-NF54 and the CQR-Dd2 strains. The crystal structures of (η(5)-pentamethylcyclopentadienyl){N(1)-(7-chloroquinolin-4-yl)-N(2)-(pyridin-2-ylmethyl)ethane-1,2-diamine)} chlororhodium(III) chloride and (η(5)-pentamethylcyclopentadienyl){(4-chloro-2-(((2-((7-chloroquinolin-4-yl)amino)ethyl)imino)methyl)phenolate)}chlororhodium(III) chloride are reported. The crystallization of the amino-pyridyl complex (η(5)-pentamethylcyclopentadienyl){(N(1)-(7-chloroquinolin-4-yl)-N(2)-(pyridin-2-ylmethyl)ethane-1,2-diamine)}chloroiridium(III) chloride in acetone resulted in the formation of the imino-pyridyl derivative (η(5)-pentamethylcyclopentadienyl){(N1-(7-chloroquinolin-4-yl)-N2-(pyridin-2-ylmethylene)ethane-1,2-diamine)}chloroiridium(III) chloride, the crystal structure of which is also reported.
Zheng, Jun; You, Shu-Li
2014-11-24
Enantioselective construction of axially chiral biaryls by direct C-H bond functionalization reactions has been realized. Novel axially chiral biaryls were synthesized by the direct C-H bond olefination of biaryl compounds, using a chiral [Cp*Rh(III)] catalyst, in good to excellent yields and enantioselectivities. The obtained axially chiral biaryls were found as suitable ligands for rhodium-catalyzed asymmetric conjugate additions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Zhang, Lei; Qureshi, Zafar; Sonaglia, Lorenzo; Lautens, Mark
2014-12-08
Compatible combinations of achiral and chiral ligands can be used in rhodium/palladium catalysis to achieve highly enantioselective domino reactions. The difference in rates of catalysis and minimal effects of ligand interference confer control in the domino sequence. The "all-in-one" 1,4-conjugate arylation and C-N cross-coupling through sequential Rh/Pd catalysis provides access to enantioenriched dihydroquinolinone building blocks. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Shintani, Ryo; Duan, Wei-Liang; Hayashi, Tamio
2006-05-03
A rhodium-catalyzed asymmetric 1,4-addition of arylboronic acids to substituted maleimides has been described. The regioselectivity in this reaction is controlled by the choice of ligand (dienes or bisphosphines), and 1,4-adducts with a quaternary stereocenter can be obtained with high regio- and enantioselectivity by the use of (R)-H8-binap.
Leniak, Arkadiusz; Kamieński, Bohdan; Jaźwiński, Jarosław
2015-05-01
Seven new oligomeric complexes of 4,4'-bipyridine; 3,3'-bipyridine; benzene-1,4-diamine; benzene-1,3-diamine; benzene-1,2-diamine; and benzidine with rhodium tetraacetate, as well as 4,4'-bipyridine with molybdenum tetraacetate, have been obtained and investigated by elemental analysis and solid-state nuclear magnetic resonance spectroscopy, (13)C and (15)N CPMAS NMR. The known complexes of pyrazine with rhodium tetrabenzoate, benzoquinone with rhodium tetrapivalate, 4,4'-bipyridine with molybdenum tetrakistrifluoroacetate and the 1 : 1 complex of 2,2'-bipyridine with rhodium tetraacetate exhibiting axial-equatorial ligation mode have been obtained as well for comparison purposes. Elemental analysis revealed 1 : 1 complex stoichiometry of all complexes. The (15)N CPMAS NMR spectra of all new complexes consist of one narrow signal, indicating regular uniform structures. Benzidine forms a heterogeneous material, probably containing linear oligomers and products of further reactions. The complexes were characterized by the parameter complexation shift Δδ (Δδ = δcomplex - δligand). This parameter ranged from around -40 to -90 ppm in the case of heteroaromatic ligands, from around -12 to -22 ppm for diamines and from -16 to -31 ppm for the complexes of molybdenum tetracarboxylates with 4,4'-bipyridine. The experimental results have been supported by a density functional theory computation of (15)N NMR chemical shifts and complexation shifts at the non-relativistic Becke, three-parameter, Perdew-Wang 91/[6-311++G(2d,p), Stuttgart] and GGA-PBE/QZ4P levels of theory and at the relativistic scalar and spin-orbit zeroth order regular approximation/GGA-PBE/QZ4P level of theory. Nucleus-independent chemical shifts have been calculated for the selected compounds. Copyright © 2015 John Wiley & Sons, Ltd.
Arisawa, Mieko; Sawahata, Kyosuke; Yamada, Tomoki; Sarkar, Debayan; Yamaguchi, Masahiko
2018-02-16
Organophosphorus compounds with a phosphorus atom attached to a phenyl group and two organothio/organoseleno groups were synthesized using the rhodium-catalyzed insertion reaction of the PhP group of pentaphenylcyclopentaphosphine (PhP) 5 with acyclic disulfides and diselenides. The method was applied to the synthesis of heterocyclic compounds containing the S-P-S group by the reaction of (PhP) 5 and cyclic disulfides such as 1,2-dithietes, 1,2-dithiocane, 1,4,5-dithiopane, and 1,2-dithiolanes.
Haydl, Alexander M; Xu, Kun; Breit, Bernhard
2015-06-08
The rhodium-catalyzed asymmetric N-selective coupling of pyrazole derivatives with terminal allenes gives access to enantioenriched secondary and tertiary allylic pyrazoles, which can be employed for the synthesis of medicinally important targets. The reaction tolerates a large variety of functional groups and labelling experiments gave insights into the reaction mechanism. This new methodology was further applied in a highly efficient synthesis of JAK 1/2 inhibitor (R)-ruxolitinib. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
NASA Astrophysics Data System (ADS)
Asiry, Moshabab A.; AlShahrani, Ibrahim; Almoammar, Salem; Durgesh, Bangalore H.; Kheraif, Abdulaziz A. Al; Hashem, Mohamed I.
2018-02-01
Aim. To investigate the effect of epoxy, polytetrafluoroethylene (PTFE) and rhodium surface coatings on surface roughness, nano-mechanical properties and biofilm adhesion of nickel titanium (Ni-Ti) archwires Methods. Three different coated (Epoxy, polytetrafluoroethylene (PTFE) and rhodium) and one uncoated Ni-Ti archwires were evaluated in the present study. Surface roughness (Ra) was assessed using a non-contact surface profilometer. The mechanical properties (nano-hardness and elastic modulus) were measured using a nanoindenter. Bacterial adhesion assays were performed using Streptococcus mutans (MS) and streptococcus sobrinus (SS) in an in-vitro set up. The data obtained were analyzed using analyses of variance, Tukey’s post hoc test and Pearson’s correlation coefficient test. Result. The highest Ra values (1.29 ± 0.49) were obtained for epoxy coated wires and lowest Ra values (0.29 ± 0.16) were obtained for the uncoated wires. No significant differences in the Ra values were observed between the rhodium coated and uncoated archwires (P > 0.05). The highest nano-hardness (3.72 ± 0.24) and elastic modulus values (61.15 ± 2.59) were obtained for uncoated archwires and the lowest nano-hardness (0.18 ± 0.10) and elastic modulus values (4.84 ± 0.65) were observed for epoxy coated archwires. No significant differences in nano-hardness and elastic modulus values were observed between the coated archwires (P > 0.05). The adhesion of Streptococcus mutans (MS) to the wires was significantly greater than that of streptococcus sobrinus (SS). The epoxy coated wires demonstrated an increased adhesion of MS and SS and the uncoated wires demonstrated decreased biofilm adhesion. The Spearman correlation test showed that MS and SS adhesion was positively correlated with the surface roughness of the wires. Conclusion. The different surface coatings significantly influence the roughness, nano-mechanical properties and biofilm adhesion parameters of the archwires. The
Guasch, Joan; Giménez-Nueno, Irene; Funes-Ardoiz, Ignacio; Bernús, Miguel; Matheu, M Isabel; Maseras, Feliu; Castillón, Sergio; Díaz, Yolanda
2018-03-26
Regio- and stereoselective oxyamination of dienes through a tandem rhodium-catalysed aziridination-nucleophilic opening affords racemic oxazolidinone derivatives, which undergo a kinetic resolution acylation process with amidine-based catalysts (ABCs) to achieve s values of up to 117. This protocol was applied to the enantioselective synthesis of sphingosine. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Muralidharan, S.; Ferraudi, G.; Schmatz, K.
1982-08-01
Rh(ph)(CH/sub 3/OH)X, X = Cl, Br, or I, has been prepared and characterized. Continuous-wave irradiations of these phthalocyanines in the ultraviolet region of the spectrum, in acetonitrile and acetonitrile-isopropyl alcohol mixtures, result in the redox-induced substitution of the axially coordinated halide ions by the solvent. Even though the overall reaction was photosubstitution, the intermediates observed by conventional and laser flash photolysis were found to be rhodium(II) phthalocyanine and rhodium(III) phthalocyanine ligand radicals. The photoredox processes were attributed to the population of (n..pi..*) ligand-centered excited states that involve the lone electron pair from the bridge nitrogens of the phthalocyanine ligand. 9more » figures, 3 tables.« less
Kaltenbach, Angela; Noordmann, Janine; Görlitz, Volker; Pape, Carola; Richter, Silke; Kipphardt, Heinrich; Kopp, Gernot; Jährling, Reinhard; Rienitz, Olaf; Güttler, Bernd
2015-04-01
Gravimetrically prepared mono-elemental reference solutions having a well-known mass fraction of approximately 1 g/kg (or a mass concentration of 1 g/L) define the very basis of virtually all measurements in inorganic analysis. Serving as the starting materials of all standard/calibration solutions, they link virtually all measurements of inorganic analytes (regardless of the method applied) to the purity of the solid materials (high-purity metals or salts) they were prepared from. In case these solid materials are characterized comprehensively with respect to their purity, this link also establishes direct metrological traceability to The International System of Units (SI). This, in turn, ensures the comparability of all results on the highest level achievable. Several national metrology institutes (NMIs) and designated institutes (DIs) have been working for nearly two decades in close cooperation with commercial producers on making an increasing number of traceable reference solutions available. Besides the comprehensive characterization of the solid starting materials, dissolving them both loss-free and completely under strict gravimetric control is a challenging problem in the case of several elements like molybdenum and rhodium. Within the framework of the European Metrology Research Programme (EMRP), in the Joint Research Project (JRP) called SIB09 Primary standards for challenging elements, reference solutions of molybdenum and rhodium were prepared directly from the respective metals with a relative expanded uncertainty associated with the mass fraction of U rel(w) < 0.05 %. To achieve this, a microwave-assisted digestion procedure for Rh and a hotplate digestion procedure for Mo were developed along with highly accurate and precise inductively coupled plasma optical emission spectrometry (ICP OES) and multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) methods required to assist with the preparation and as dissemination tools.
NASA Astrophysics Data System (ADS)
Ni, P.
2017-12-01
Porphyry deposits are the world most important source of Mo, accounting for more than 95% of world Mo production. Porphyry Mo deposits have been classified into Climax type and Endako type. The Climax type was generally formed in an intra-continental setting, and contain high contents of Mo (0.15-0.45 wt.%) and F (0.5-5 wt.%). In contrast, the Endako type was generated in a continental arc setting and featured by low concentrations of Mo (0.05-0.15 wt.%) and F (0.05-0.15 wt.%). The systematic comparison of ore fluids in two contrasting tectonic environments is still poorly constrained. In this study, the Shapinggou and Zhilingtou Mo deposits in South China were selected to present the contrasting ore-forming fluid features. The fluid inclusion study of Shapinggou Mo deposit suggest: Early barren quartz veins contain fluid inclusions with salinities of 7.9-16.9 wt% NaCl equiv . CO2 contents are high enough to be detected by Raman. Later molybdenite-quartz veins contain vapor-type fluid inclusions with lower salinities (0.1-7.4 wt% NaCl equiv) but higher CO2-contents, coexisting with brine inclusions with 32.9-50.9 wt% NaCl equiv. The fluid inclusion study on Zhilintou Mo deposit suggest : Early barren quartz veins contain mostly intermediate density fluid inclusions with salinities of 5.3-14.1 wt% NaCl equiv, whereas main-stage quartz-molybdenite veins contain vapor-rich fluid inclusions of 0.5-6.2 wt% NaClequiv coexisting with brine inclusions of 38.6-44.8 wt% NaCl equiv. In contrast to the Shapinggou Mo deposit, the fluid inclusions at Shizitou contain only minor amounts of CO2. This study suggests the two porphyry molybdenum deposits experienced a similar fluid evolution trend, from single-phase fluids at the premineralization stage to two-phase fluids at the mineralization stage. Fluid boiling occurred during the ore stage and probably promoted a rapid precipitation of molybdenite. Intensive phyllic alteration, CO2-poor ore-forming fluids, and continental arc
Han, Quan; Huo, Yanyan; Wu, Jiangyan; He, Yaping; Yang, Xiaohui; Yang, Longhu
2017-03-24
A highly sensitive method based on cloud point extraction (CPE) separation/preconcentration and graphite furnace atomic absorption spectrometry (GFAAS) detection has been developed for the determination of ultra-trace amounts of rhodium in water samples. A new reagent, 2-(5-iodo-2-pyridylazo)-5-dimethylaminoaniline (5-I-PADMA), was used as the chelating agent and the nonionic surfactant TritonX-114 was chosen as extractant. In a HAc-NaAc buffer solution at pH 5.5, Rh(III) reacts with 5-I-PADMA to form a stable chelate by heating in a boiling water bath for 10 min. Subsequently, the chelate is extracted into the surfactant phase and separated from bulk water. The factors affecting CPE were investigated. Under the optimized conditions, the calibration graph was linear in the range of 0.1-6.0 ng/mL, the detection limit was 0.023 ng/mL for rhodium and relative standard deviation was 3.67% ( c = 1.0 ng/mL, n = 11).The method has been applied to the determination of trace rhodium in water samples with satisfactory results.
Choo, Ken-Loon; Lautens, Mark
2018-03-02
A rhodium-catalyzed conjugate alkynylation/aldol cyclization cascade was developed. Densely functionalized cyclic α-propargyl-β-hydroxyketones were synthesized with simultaneous formation of a C(sp)-C(sp 3 ) bond, a C(sp 3 )-C(sp 3 ) bond, as well as three new contiguous stereocenters. The transformation was achieved with excellent enantio- and diastereoselectivities using BINAP as the ligand. The synthetic utility of the newly installed alkynyl moiety was exhibited by subjecting the products to an array of derivatizations.
Sediment-Hosted Copper Deposits of the World: Deposit Models and Database
Cox, Dennis P.; Lindsey, David A.; Singer, Donald A.; Diggles, Michael F.
2003-01-01
Introduction This publication contains four descriptive models and four grade-tonnage models for sediment hosted copper deposits. Descriptive models are useful in exploration planning and resource assessment because they enable the user to identify deposits in the field and to identify areas on geologic and geophysical maps where deposits could occur. Grade and tonnage models are used in resource assessment to predict the likelihood of different combinations of grades and tonnages that could occur in undiscovered deposits in a specific area. They are also useful in exploration in deciding what deposit types meet the economic objectives of the exploration company. The models in this report supersede the sediment-hosted copper models in USGS Bulletin 1693 (Cox, 1986, and Mosier and others, 1986) and are subdivided into a general type and three subtypes. The general model is useful in classifying deposits whose features are obscured by metamorphism or are otherwise poorly described, and for assessing regions in which the geologic environments are poorly understood. The three subtypes are based on differences in deposit form and environments of deposition. These differences are described under subtypes in the general model. Deposit models are based on the descriptions of geologic environments and physical characteristics, and on metal grades and tonnages of many individual deposits. Data used in this study are presented in a database representing 785 deposits in nine continents. This database was derived partly from data published by Kirkham and others (1994) and from new information in recent publications. To facilitate the construction of grade and tonnage models, the information, presented by Kirkham in disaggregated form, was brought together to provide a single grade and a single tonnage for each deposit. Throughout the report individual deposits are defined as being more than 2,000 meters from the nearest adjacent deposit. The deposit models are presented here as
AMTEC cell testing, optimization of rhodium/tungsten electrodes, and tests of other components
NASA Technical Reports Server (NTRS)
Williams, Roger M.; Ryan, Margaret A.; Jeffries-Nakamura, Barbara; Underwood, Mark L.; O'Connor, Dennis; Kikkert, Stan
1991-01-01
Electrodes, current collectors, ceramic to metal braze seals, and metallic components exposed to the high 'hot side' temperatures and sodium liquid and vapor environment have been tested and evaluated in laboratory cells running for hundreds of hours at 1100-1200 K. Rhodium/tungsten electrodes have been selected as the optimum electrodes based on performance parameters and durability. Current collectors have been evaluated under simulated and actual operating conditions. The microscopic effects of metal migration between electrode and current collector alloys as well as their thermal and electrical properties determined the suitability of current collector and lead materials. Braze seals suitable for long term application to AMTEC devices are being developed.
NASA Astrophysics Data System (ADS)
Kuo, Yenting; Klabunde, Kenneth J.
2012-07-01
Nanostructured strontium titanate visible-light-driven photocatalysts containing rhodium and ruthenium were synthesized by a modified aerogel synthesis using ruthenium chloride and rhodium nitrate as dopant precursors, and titanium isopropoxide and strontium metal as the metal sources. The well-defined crystalline SrTiO3 structure was confirmed by means of x-ray diffraction. After calcination at 500 °C, diffuse reflectance spectroscopy shows an increase in light absorption at 370 nm due to the presence of Rh3 + ; however an increase of the calcination temperature to 600 °C led to a decrease in intensity, probably due to a loss of surface area. An increase in the rhodium doping level also led to an increase in absorption at 370 nm however, the higher amounts of dopant lowered the photocatalytic activity. The modified aerogel synthesis allows greatly enhanced H2 production performance from an aqueous methanol solution under visible light irradiation compared with lower surface area conventional materials. We believe that this enhanced activity is due to the higher surface areas while high quality nanocrystalline materials are still obtained. Furthermore, the surface properties of these nanocrystalline aerogel materials are different, as exhibited by the higher activities in alkaline solutions, while conventional materials (obtained via high temperature solid-state synthesis methods) only exhibit reasonable hydrogen production in acidic solutions. Moreover, an aerogel synthesis approach gives the possibility of thin-film formation and ease of incorporation into practical solar devices.
Gao, Wenchao; Wang, Qingli; Xie, Yun; Lv, Hui; Zhang, Xumu
2016-01-01
Rhodium/DuanPhos-catalyzed asymmetric hydrogenation of aliphatic α-dehydroamino ketones has been achieved and afforded chiral α-amino ketones in high yields and excellent enantioselectives (up to 99 % ee), which could be reduced further to chiral β-amino alcohols by LiAlH(tBuO)3 with good yields. This protocol provides a readily accessible route for the synthesis of chiral α-amino ketones and chiral β-amino alcohols. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Martin, Timothy J.; Rovis, Tomislav
2013-01-01
An enantioselective rhodium (I) catalyzed [2+2+2] cycloaddition with a cleavable tether has been developed. The reaction proceeds with a variety of alkyne substrates in good yield and high enantioselectivity. Upon reduction of the vinylogous amide in high diastereoselectivity (>19:1) and cleavage of the tether, N-methylpiperidine products with functional group handles can be accessed. PMID:23606664
Yang, Guan-Jun; Zhong, Hai-Jing; Ko, Chung-Nga; Wong, Suk-Yu; Vellaisamy, Kasipandi; Ye, Min; Ma, Dik-Lung; Leung, Chung-Hang
2018-03-06
The rhodium(iii) complex 1 was identified as a potent Wee1 inhibitor in vitro and in cellulo. It decreased Wee1 activity and unscheduled mitotic entry, and induced cell damage and death in TP53-mutated triple-negative breast cancer cells. 1 represents a promising scaffold for further development of more potent metal-based Wee1 antagonists.
Arnold, Jeffrey S; Mwenda, Edward T; Nguyen, Hien M
2014-04-01
Dynamic kinetic asymmetric amination of branched allylic acetimidates has been applied to the synthesis of 2-alkyl-dihydrobenzoazepin-5-ones. These seven-membered-ring aza ketones are prepared in good yield with high enantiomeric excess by rhodium-catalyzed allylic substitution with 2-amino aryl aldehydes followed by intramolecular olefin hydroacylation of the resulting alkenals. This two-step procedure is amenable to varied functionality and proves useful for the enantioselective preparation of these ring systems. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Pannek, Carolin; Tarantik, Karina R; Schmitt, Katrin; Wöllenstein, Jürgen
2018-06-21
The detection of the toxic gas carbon monoxide (CO) in the low ppm range is required in different applications. We present a study of the reactivity of different gasochromic rhodium complexes towards the toxic gas carbon monoxide (CO). Therefore, variations of binuclear rhodium complexes with different ligands were prepared. They were characterized by FTIR spectroscopy, ¹H NMR spectroscopy, and differential scanning calorimetry. All complexes are spectroscopically distinguishable and temperature stable up to at least 187 °C. The gasochromic behavior of all different compounds was tested. Therefore, the compounds were dissolved in toluene and exposed to 100 ppm CO for 10 min to investigate their gas sensitivity and reaction velocity. The changes in the transmission spectra were recorded by UV/vis spectroscopy. Furthermore, a significant influence of the solvent to the color dyes’ gasochromic reaction and behavior was observed. After characterization, one complex was transferred as sensing element into an optical gas sensor. Two different measurement principles (reflection- and waveguide-based) were built up and tested towards their capability as gasochromic CO sensors. Finally, different gas-dependent measurements were carried out.
Ye, Baihua; Cramer, Nicolai
2014-07-21
Directed Cp*Rh(III)-catalyzed carbon-hydrogen (C-H) bond functionalizations have evolved as a powerful strategy for the construction of heterocycles. Despite their high value, the development of related asymmetric reactions is largely lagging behind due to a limited availability of robust and tunable chiral cyclopentadienyl ligands. Rhodium complexes comprising a chiral Cp ligand with an atropchiral biaryl backbone enables an asymmetric synthesis of isoindolones from arylhydroxamates and weakly alkyl donor/acceptor diazo derivatives as one-carbon component under mild conditions. The complex guides the substrates with a high double facial selectivity yielding the chiral isoindolones in good yields and excellent enantioselectivities. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Oppenheimer, Jossian; Johnson, Whitney L.; Figueroa, Ruth; Hayashi, Ryuji; Hsung, Richard P.
2009-01-01
A rhodium(I)-xylyl-BINAP catalyzed asymmetric [2 + 2 + 2] cycloaddition of achiral conjugated aryl ynamides with various diynes is described here. This asymmetric cycloaddition provides a series of structurally interesting chiral N,O-biaryls with excellent enantioselectivity along with a modest diastereoselectivity with respect to both C-C and C-N axial chirality. PMID:20161177
Morphology-Controlled Synthesis of Rhodium Nanoparticles for Cancer Phototherapy.
Kang, Seounghun; Shin, Woojun; Choi, Myung-Ho; Ahn, Minchul; Kim, Young-Kwan; Kim, Seongchan; Min, Dal-Hee; Jang, Hongje
2018-06-22
Rhodium nanoparticles are promising transition metal nanocatalysts for electrochemical and synthetic organic chemistry applications. However, notwithstanding their potential, to date, Rh nanoparticles have not been utilized for biological applications; there has been no cytotoxicity study of Rh reported in the literature. In this regard, the absence of a facile and controllable synthetic strategy of Rh nanostructures with various sizes and morphologies might be responsible for the lack of progress in this field. Herein, we have developed a synthetic strategy for Rh nanostructures with controllable morphology through an inverse-directional galvanic replacement reaction. Three types of Rh-based nanostructures-nanoshells, nanoframes, and porous nanoplates-were successfully synthesized. A plausible synthetic mechanism based on thermodynamic considerations has also been proposed. The cytotoxicity, surface functionalization, and photothermal therapeutic effect of manufactured Rh nanostructures were systematically investigated to reveal their potential for in vitro and in vivo biological applications. Considering the comparable behavior of porous Rh nanoplates to that of gold nanostructures that are widely used in nanomedicine, the present study introduces Rh-based nanostructures into the field of biological research.
Zhang, Qing-Wei; An, Kun; Liu, Li-Chuan; Yue, Yuan; He, Wei
2015-06-01
Reported herein is the rhodium-catalyzed enantioselective C-H bond silylation of the cyclopentadiene rings in Fe and Ru metallocenes. Thus, in the presence of (S)-TMS-Segphos, the reactions took place under very mild conditions to afford metallocene-fused siloles in good to excellent yields and with ee values of up to 97%. During this study it was observed that the steric hindrance of chiral ligands had a profound influence on the reactivity and enantioselectivity of the reaction, and might hold the key to accomplishing conventionally challenging asymmetric C-H silylations. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Lipshutz, Bruce H.; Isley, Nicholas A.; Moser, Ralph; Ghorai, Subir; Leuser, Helena; Taft, Benjamin R.
2013-01-01
Using the newly introduced designer surfactant polyethyleneglycol ubiquinol sebacate (PQS), as the platform for micellar catalysis, nonracemic BINAP has been covalently attached and rhodium(I) inserted to form PQS-BINAP-Rh. This species, the first example of a nonracemically-ligated transition metal catalyst-tethered amphiphile, can be utilized for Rh-catalyzed asymmetric conjugate addition reactions of arylboronic acids to acyclic and cyclic enones. These are performed in water at room temperature, while the catalyst can be recycled without its removal from water in the reaction vessel. PMID:24659941
Mas-Marzá, Elena; Poyatos, Macarena; Sanaú, Mercedes; Peris, Eduardo
2004-03-22
Two tripodal trisimidazolium ligand precursors have been tested in the synthesis of new N-heterocyclic carbene rhodium and iridium complexes. [Tris(3-methylbenzimidazolium-1-yl)]methane sulfate gave products with coordination of the decomposed precursor. [1,1,1-Tris(3-butylimidazolium-1-yl)methyl]ethane trichloride (TIMEH(3)(Bu)) coordinated to the metal in a chelate and bridged-chelate form, depending on the reaction conditions. The crystal structures of two of the products are described. The compounds resulting from the coordination with TIME(Bu) were tested in the catalytic hydrosilylation of terminal alkynes.
Do deposit-feeders compete? Isotopic niche analysis of an invasion in a species-poor system
Karlson, Agnes M. L.; Gorokhova, Elena; Elmgren, Ragnar
2015-01-01
Successful establishment of invasive species is often related to the existence of vacant niches. Competition occurs when invaders use the same limiting resources as members of the recipient community, which will be reflected in some overlap of their trophic niches. The concept of isotopic niche has been used to study trophic niche partitioning among species. Here, we present a two-year field study comparing isotopic niches of the deposit-feeding community in a naturally species-poor system. The isotopic niche analyses showed no overlap between a recent polychaete invader and any of the native species suggesting that it has occupied a vacant niche. Its narrow isotopic niche suggests specialized feeding, however, the high δ15N values compared to natives are most likely due to isotope fractionation effects related to nitrogen recycling and a mismatch between biological stoichiometry of the polychaete and the sediment nitrogen content. Notably, highly overlapping isotopic niches were inferred for the native species, which is surprising in a food-limited system. Therefore, our results demonstrate that invaders may broaden the community trophic diversity and enhance resource utilization, but also raise questions about the congruence between trophic and isotopic niche concepts and call for careful examination of assumptions underlying isotopic niche interpretation. PMID:25988260
Otomaru, Yusuke; Senda, Taichi; Hayashi, Tamio
2004-09-16
[reaction: see text] The axially chiral bisphosphine ligand, 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (binap), was supported on a polystyrene-poly(ethylene glycol) copolymer (PS-PEG) resin and was used successfully for the rhodium-catalyzed asymmetric 1,4-addition of phenylboronic acid to alpha,beta-unsaturated ketones in water.
Dalton, Derek M.; Oberg, Kevin M.; Yu, Robert T.; Lee, Ernest E.; Perreault, Stéphane; Oinen, Mark Emil; Pease, Melissa L.; Malik, Guillaume; Rovis, Tomislav
2009-01-01
This manuscript describes the development and scope of the asymmetric rhodium-catalyzed [2+2+2] cycloaddition of terminal alkynes and alkenyl isocyanates leading to the formation of indolizidine and quinolizidine scaffolds. The use of phosphoramidite ligands proved crucial for avoiding competitive terminal alkyne dimerization. Both aliphatic and aromatic terminal alkynes participate well, with product selectivity a function of both the steric and electronic character of the alkyne. Manipulation of the phosphoramidite ligand leads to tuning of enantio- and product selectivity, with a complete turnover in product selectivity seen with aliphatic alkynes when moving from Taddol-based to biphenol-based phosphoramidites. Terminal and 1,1-disubstituted olefins are tolerated with nearly equal efficacy. Examination of a series of competition experiments in combination with analysis of reaction outcome shed considerable light on the operative catalytic cycle. Through a detailed study of a series of X-ray structures of rhodium(cod)chloride/phosphoramidite complexes, we have formulated a mechanistic hypothesis that rationalizes the observed product selectivity. PMID:19817441
Lu, Xing; Wu, Yi-Ming; Yang, Jing-Mei; Ma, Feng-E; Li, Liang-Ping; Chen, Sheng; Zhang, Ye; Ni, Qing-Ling; Pan, Ying-Ming; Hong, Xue; Peng, Yan
2018-05-10
A series of 2(1H)-quinolinone derivatives and their rhodium (III) complexes were designed and synthesized. All the rhodium (III) complexes exhibited higher in vitro cytotoxicity for Hep G2, HeLa 229, MGC80-3, and NCI-H460 human tumor cell lines than their ligands and cisplatin, and among them complex 9 was found to be selectively cytotoxic to tumor cells. Further investigation revealed that complex 9 caused cell cycle arrest at the G2/M phase and induced apoptosis, and inhibited the proliferation of Hep G2 cells by impeding the phosphorylation of epidermal growth factor receptor (EGFR) and its downstream enzymes. Complex 9 also up-regulated the proapoptotic proteins Bak, Bax, and Bim, which altogether activated caspase-3/9 to initiate cell apoptosis. Notably, complex 9 effectively inhibited tumor growth in the NCI-H460 xenograft mouse model with less adverse effect than cisplatin. Copyright © 2018 Elsevier Masson SAS. All rights reserved.
Aïssa, Christophe; Ho, Kelvin Y T; Tetlow, Daniel J; Pin-Nó, María
2014-01-01
The use of α,ω-dienes as functionalization reagents for olefinic carbon–hydrogen bonds has been rarely studied. Reported herein is the rhodium(I)-catalyzed rearrangement of prochiral 1,6-heptadienes into [2,2,1]-cycloheptane derivatives with concomitant creation of at least three stereogenic centers and complete diastereocontrol. Deuterium-labeling studies and the isolation of a key intermediate are consistent with a group-directed C=H bond activation, followed by two consecutive migratory insertions, with only the latter step being diastereoselective. PMID:24634225
The unending deposit insurance mess.
Kane, E J
1989-10-27
The thrift institution deposit insurance mess is rooted in defects in political and bureaucratic accountability. Under existing incentives, covering up evidence of poor regulatory performance and relaxing binding capital requirements are rational governmental responses to widespread industry insolvency. Similarly, aggressive industry risk taking is a rational response by thrift managers to regulatory forbearances. Far from acknowledging these incentive defects, the Bush plan for cleaning up the mess adopts theories that spotlight other causes: specifically, poor thrift management and the deregulation of thrift institution activities and of deposit interest rates. To end the mess, politicians and regulators must jettison these comfortable theories and surrender discretion that permits them to finesse the need to budget for governmental financial commitments.
Song, Zhiqian; Chang, Hucheng; Zhu, Weiqin; Xu, Chenlong; Feng, Xinjian
2015-01-01
Developing nanostructured electrocatalysts, with low overpotential, high selectivity and activity has fundamental and technical importance in many fields. We report here rhodium nanoparticle and mesoporous silicon nanowire (RhNP@mSiNW) hybrids for hydrogen peroxide (H2O2) detection with high electrocatalytic activity and selectivity. By employing electrodes that loaded with RhNP@mSiNW nanohybrids, interference caused from both many electroactive substances and dissolved oxygen were eliminated by electrochemical assaying at an optimal potential of +75 mV. Furthermore, the electrodes exhibited a high detection sensitivity of 0.53 μA/mM and fast response (< 5 s). This high-performance nanohybrid electrocatalyst has great potential for future practical application in various oxidase-base biosensors. PMID:25588953
Selective rhodium-catalyzed reduction of tertiary amides in amino acid esters and peptides.
Das, Shoubhik; Li, Yuehui; Bornschein, Christoph; Pisiewicz, Sabine; Kiersch, Konstanze; Michalik, Dirk; Gallou, Fabrice; Junge, Kathrin; Beller, Matthias
2015-10-12
Efficient reduction of the tertiary amide bond in amino acid derivatives and peptides is described. Functional group selectivity has been achieved by applying a commercially available rhodium precursor and bis(diphenylphosphino)propane (dppp) ligand together with phenyl silane as a reductant. This methodology allows for specific reductive derivatization of biologically interesting peptides and offers straightforward access to a variety of novel peptide derivatives for chemical biology studies and potential pharmaceutical applications. The catalytic system tolerates a variety of functional groups including secondary amides, ester, nitrile, thiomethyl, and hydroxy groups. This convenient hydrosilylation reaction proceeds at ambient conditions and is operationally safe because no air-sensitive reagents or highly reactive metal hydrides are needed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
NASA Astrophysics Data System (ADS)
Kisielowski, Christian; Wang, Lin-Wang; Specht, Petra; Calderon, Hector A.; Barton, Bastian; Jiang, Bin; Kang, Joo H.; Cieslinski, Robert
2013-07-01
The dynamic responses of a rhodium catalyst and a graphene sheet are investigated upon random excitation with 80 kV electrons. An extraordinary electron microscope stability and resolution allow studying temporary atom displacements from their equilibrium lattice sites into metastable sites across projected distances as short as 60 pm. In the rhodium catalyst, directed and reversible atom displacements emerge from excitations into metastable interstitial sites and surface states that can be explained by single atom trajectories. Calculated energy barriers of 0.13 eV and 1.05 eV allow capturing single atom trapping events at video rates that are stabilized by the Rh [110] surface corrugation. Molecular dynamics simulations reveal that randomly delivered electrons can also reversibly enhance the sp3 and the sp1 characters of the sp2-bonded carbon atoms in graphene. The underlying collective atom motion can dynamically stabilize characteristic atom displacements that are unpredictable by single atom trajectories. We detect three specific displacements and use two of them to propose a path for the irreversible phase transformation of a graphene nanoribbon into carbene. Collectively stabilized atom displacements greatly exceed the thermal vibration amplitudes described by Debye-Waller factors and their measured dose rate dependence is attributed to tunable phonon contributions to the internal energy of the systems. Our experiments suggest operating electron microscopes with beam currents as small as zepto-amperes/nm2 in a weak-excitation approach to improve on sample integrity and allow for time-resolved studies of conformational object changes that probe for functional behavior of catalytic surfaces or molecules.
Surface Finish after Laser Metal Deposition
NASA Astrophysics Data System (ADS)
Rombouts, M.; Maes, G.; Hendrix, W.; Delarbre, E.; Motmans, F.
Laser metal deposition (LMD) is an additive manufacturing technology for the fabrication of metal parts through layerwise deposition and laser induced melting of metal powder. The poor surface finish presents a major limitation in LMD. This study focuses on the effects of surface inclination angle and strategies to improve the surface finish of LMD components. A substantial improvement in surface quality of both the side and top surfaces has been obtained by laser remelting after powder deposition.
Masuda, Kengo; Sakiyama, Norifumi; Tanaka, Rie; Noguchi, Keiichi; Tanaka, Ken
2011-05-11
It has been established that a cationic rhodium(I)/(R)-H(8)-BINAP or (R)-Segphos complex catalyzes two modes of enantioselective cyclizations of γ-alkynylaldehydes with acyl phosphonates via C-P or C-H bond cleavage. The ligands of the Rh(I) complexes and the substitutents of both γ-alkynylaldehydes and acyl phosphonates control these two different pathways. © 2011 American Chemical Society
Steib, Philip; Breit, Bernhard
2018-04-19
Herein, we report on the first enantioselective and atom-efficient catalytic one-step dimerization method to selectively transform ω-allenyl carboxylic acids into C 2 -symmetric 14- to 28-membered bismacrolactones (macrodiolides). This convenient asymmetric access serves as an attractive route towards multiple naturally occuring homodimeric macrocyclic scaffolds and demonstrates excellent efficiency to construct the complex, symmetric core structures. By utilizing a rhodium catalyst with a modified chiral cyclopentylidene-diop ligand, the desired diolides were obtained in good to high yields, high diastereoselectivity, and excellent enantioselectivity. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Chartrand, Daniel; Hanan, Garry S
2014-11-13
The synthesis and characterization of five C-C coupling products obtained from the reaction of a paddlewheel tetrakis 4-bromo-N,N'-diphenylbenzamidinate dirhodium dimer with 4-pyridineboronic acid pinacol ester are reported. The coupling reactions occur on one to four amidinate ligands, leading to rhodium dimers containing [tetrakis, tris, cis-bis, trans-bis, or mono]-N,N'-diphenyl-4-(pyridin-4-yl)benzamidinate ligands, effectively creating new binding sites on the metal complexes. The new compounds were isolated by column chromatography, and the exact conformations were verified by X-ray crystallography. Redox processes showed only a small variation within the coupling products and included two oxidations (1.30 ± 0.02 V, 0.27 ± 0.01 V vs SCE) and one reduction (-1.55 ± 0.02 V vs SCE), all centered on the Rh-Rh core. Time-dependent density functional theory (TD-DFT) was used to analyze this series with four other fully characterized N,N'-diphenyl-aryl-amidinate rhodium dimers that were found in the literature. The two main absorption bands of these nine rhodium dimers were compared to TD-DFT calculations, both giving excellent correlation. The first, a metal-to-metal (MM) transition around 11800 cm(-1) (845 nm) was blue-shifted in the calculation, with an average difference of 1378 cm(-1) but had only a 15 cm(-1) standard deviation, showing a strong correlation despite the energy difference. The second, a metal-to-ligand charge transfer (MLCT) transition around 18900 cm(-1) (530 nm) was a near perfect match with only a 64 cm(-1) average difference and a 35 cm(-1) standard deviation. The electronic transition, redox potentials, and HOMO and LUMO energies of all dimers were plotted versus the Hammett parameter (σ) of the aryl group and Taft's model with 2 components: field effects (σF) and resonance (σR). The properties involving only the Rh-Rh core (MM band, all oxidation potentials, HOMO and LUMO) were fit with a single set of σF and σR contributions (73
Synthesis and structures of a pincer-type rhodium(iii) complex: reactivity toward biomolecules.
Milutinović, Milan M; Bogojeski, Jovana V; Klisurić, Olivera; Scheurer, Andreas; Elmroth, Sofi K C; Bugarčić, Živadin D
2016-10-04
A novel rhodium(iii) complex [Rh III (H 2 L tBu )Cl 3 ] (1) (H 2 L tBu = 2,6-bis(5-tert-butyl-1H-pyrazol-3-yl)pyridine) containing a pincer type, tridentate nitrogen-donor chelate system was synthesized. Single crystal X-ray structure analysis revealed that 1 crystallizes in the orthorhombic space group Pbcn with a = 20.7982(6), b = 10.8952(4), c = 10.9832(4) Å, V = 2488.80(15) Å 3 , and eight molecules in the unit cell. The rhodium center in the complex [Rh III (H 2 L tBu )Cl 3 ] (1) is coordinated in a slightly distorted octahedral geometry by the tridentate N,N,N-donor and three chloro ligands, adopting a mer arrangement with an essentially planar ligand skeleton. Due to the tridentate coordination of the N,N,N-donor, the central nitrogen atom N1 is located closer to the Rh III center. The reactivity of the synthesized complex toward small biomolecules (l-methionine (l-Met), guanosine-5'-monophosphate (5'-GMP), l-histidine (l-His) and glutathione (GSH)) and to a series of duplex DNAs and RNA was investigated. The order of reactivity of the studied small biomolecules is: 5'-GMP > GSH > l-Met > l-His. Duplex RNA reacts faster with the [Rh III (H 2 L tBu )Cl 3 ] complex than duplex DNA, while shorter duplex DNA (15mer GG) reacts faster compared with 22mer GG duplex DNA. In addition, a higher reactivity is achieved with a DNA duplex with a centrally located GG-sequence than with a 22GTG duplex DNA, in which the GG-sequence is separated by a T base. Furthermore, the interaction of this metal complex 1 with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) was examined by absorption (UV-Vis) and emission spectral studies (EthBr displacement studies). Overall, the studied complex exhibited good DNA and BSA interaction ability.
Size effects on rhodium nanoparticles related to hydrogen-storage capability.
Song, Chulho; Yang, Anli; Sakata, Osami; Kumara, L S R; Hiroi, Satoshi; Cui, Yi-Tao; Kusada, Kohei; Kobayashi, Hirokazu; Kitagawa, Hiroshi
2018-06-06
To unveil the origin of the hydrogen-storage properties of rhodium nanoparticles (Rh NPs), we investigated the electronic and crystal structures of the Rh NPs using various synchrotron based X-ray techniques. Electronic structure studies revealed that the hydrogen-storage capability of Rh NPs could be attributed to their more unoccupied d-DOSs than that of the bulk near the Fermi level. Crystal structure studies indicated that lattice distortion and mean-square displacement increase while coordination number decreases with decreasing particle size and the hydrogen-absorption capability of Rh NPs improves to a greater extent with increased structural disorder in the local structure than with that in the mean structure. The smallest Rh NPs, having the largest structural disorder/increased vacancy spaces and the smallest coordination number, exhibited excellent hydrogen-storage capacity. Finally, from the bond-orientational order analysis, we confirmed that the localized disordering is distributed more over the surface part than the core part and hydrogen can be trapped on the surface part of Rh NPs which increases with a decrease in NP diameter.
Biological effects of simple changes in functionality on rhodium metalloinsertors
Weidmann, Alyson G.; Komor, Alexis C.; Barton, Jacqueline K.
2013-01-01
DNA mismatch repair (MMR) is crucial to ensuring the fidelity of the genome. The inability to correct single base mismatches leads to elevated mutation rates and carcinogenesis. Using metalloinsertors–bulky metal complexes that bind with high specificity to mismatched sites in the DNA duplex–our laboratory has adopted a new chemotherapeutic strategy through the selective targeting of MMR-deficient cells, that is, those that have a propensity for cancerous transformation. Rhodium metalloinsertors display inhibitory effects selectively in cells that are deficient in the MMR machinery, consistent with this strategy. However, a highly sensitive structure–function relationship is emerging with the development of new complexes that highlights the importance of subcellular localization. We have found that small structural modifications, for example a hydroxyl versus a methyl functional group, can yield profound differences in biological function. Despite similar binding affinities and selectivities for DNA mismatches, only one metalloinsertor shows selective inhibition of cellular proliferation in MMR-deficient versus -proficient cells. Studies of whole-cell, nuclear and mitochondrial uptake reveal that this selectivity depends upon targeting DNA mismatches in the cell nucleus. PMID:23776288
Souillart, Laetitia; Cramer, Nicolai
2014-09-01
The lactone motif is ubiquitous in natural products and pharmaceuticals. The Tishchenko disproportionation of two aldehydes, a carbonyl hydroacylation, is an efficient and atom-economic access to lactones. However, these reaction types are limited to the transfer of a hydride to the accepting carbonyl group. The transfer of alkyl groups enabling the formation of CC bonds during the ester formation would be of significant interest. Reported herein is such asymmetric carbonyl carboacylation of aldehydes and ketones, thus affording complex bicyclic lactones in excellent enantioselectivities. The rhodium(I)-catalyzed transformation is induced by an enantiotopic CC bond activation of a cyclobutanone and the formed rhodacyclic intermediate reacts with aldehyde or ketone groups to give highly functionalized lactones. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
NASA Astrophysics Data System (ADS)
Mitra, Arijeet; Sen, Indra Sekhar
2017-11-01
Anthrobiogeochemical cycles have been a subject of scientific research for many decades as they are important for identifying possible sources, sinks, and pathways of an element in the environment. In this study, we quantified global cycles for the platinum group elements (PGE; platinum (Pt), palladium (Pd) and rhodium (Rh)). We quantified the stocks of Pt, Pd, and Rh in Earth's various reservoirs, such as the core, mantle, consolidated crust, biomass, seawater, unconsolidated sediments, and atmosphere, as well as coal and petroleum deposits. We further quantified their fluxes, both natural and anthropogenic, between each reservoir, by identifying the flows across the hydrosphere, geosphere, biosphere, atmosphere and anthroposphere, including from mining activities, fossil fuel and biomass burning, construction activities, soil erosion, human contributions to net primary productivity, riverine transport, aeolian dust movement, primary production, volcanic eruption, sea-salt spray, crustal subduction, crust formation at mid ocean ridges, PGE recovery from recycling processes, and cosmic dust inputs at the Earth's surface. Stocks of PGEs were quantified by multiplying the mass of the reservoir by the average Pt, Pd and Rh concentration in the reservoir, whereas Pt, Pd and Rh fluxes were calculated by multiplying the rate of mass movement across the reservoirs with the Pt, Pd and Rh concentrations of the material. Uncertainties were explicitly incorporated in stock and flow estimations through Monte Carlo simulations. Our calculations reveal that the total surficial anthropogenic Pt, Pd, and Rh mobilizations were greater than their corresponding natural surficial mobilizations. We show that crustal subduction and crustal formation is the most important natural flow and contributes 21-42% of total PGE mobilization. When Earth's surficial processes are considered, soil erosion is the dominant flow for Rh and Pt mobilization, comprising 33% and 13%, respectively, of the
Fukuzumi, Shunichi; Kobayashi, Takeshi; Suenobu, Tomoyoshi
2008-01-01
Formic acid (HCOOH) decomposes efficiently to afford H2 and CO2 selectively in the presence of a catalytic amount of a water-soluble rhodium aqua complex, [Rh(III)(Cp*)(bpy)(H2O)]2+ (Cp*=pentamethylcyclopentadienyl, bpy=2,2'-bipyridine) in aqueous solution at 298 K. No CO was produced in this catalytic decomposition of HCOOH. The decomposition rate reached a maximum value at pH 3.8. No deterioration of the catalyst was observed during the catalytic decomposition of HCOOH, and the catalytic activity remained the same for the repeated addition of HCOOH. The rhodium-hydride complex was detected as the catalytic active species that undergoes efficient H/D exchange with water. When the catalytic decomposition of HCOOH was performed in D2O, D2 was produced selectively. Such an efficient H/D exchange and the observation of a deuterium kinetic isotope effect in the catalytic decomposition of DCOOH in H2O provide valuable mechanistic insight into this efficient and selective decomposition process.
Son, Seung Uk; Kim, Sang Bok; Reingold, Jeffrey A; Carpenter, Gene B; Sweigart, Dwight A
2005-09-07
The pi-bonded rhodium quinonoid complex, K+[(1,4-benzoquinone)Rh(COD)]-, functions as a good catalyst for the coupling of arylboronic acid and aldehydes to afford diaryl alcohols. The catalysis is heterobimetallic in that both the transition metal and concomitant alkali metal counterion play an integral part in the reaction. In addition, the anionic quinonoid catalyst itself plays a bifunctional role by acting as a ligand to the boronic acid and as a Lewis acid receptor site for the transferring aryl group.
Attanasi, E.D.; DeYoung, J.H.
1988-01-01
Physical measures of mineral deposit characteristics, such as grade and tonnage, long have been used in both subjective and analytic models to predict favorability of areas for the occurrence of mineral deposits of particular types. After a deposit has been identified, however, the explorationist must decide whether to continue data collection, begin an economic feasibility study, or abandon the prospect. The decision maker can estimate the probability that a deposit will be commercial by examining physical measures. The amount of sampling data required before such a probability estimate can be considered reliable can be determined. A logit probability model estimated from onshore titanium-bearing heavy-mineral deposit data identifies and quantifies the relative influence of a deposit's physical measures on the chances of the deposit becoming commercial. A principal conclusion that can be drawn from the analysis is that, along with a measure of deposit size, the characteristics most important in predicting commercial potential are grades of the constituent minerals. Total heavy-mineral-bearing sand grade or even total titanium grade (without data on constituent mineral grades) are poor predictors of the deposit's commercial potential. ?? 1988 International Association for Mathematical Geology.
Best, Daniel; Burns, David J; Lam, Hon Wai
2015-06-15
A commercially available rhodium(II) complex catalyzes the direct arylation of 5-diazobarbituric acids with arenes, allowing straightforward access to 5-aryl barbituric acids. Free N-H groups are tolerated on the barbituric acid, with no complications arising from N-H insertion processes. This method was applied to the concise synthesis of a potent matrix metalloproteinase (MMP) inhibitor. © 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Zhou, Bing; Chen, Zhaoqiang; Yang, Yaxi; Ai, Wen; Tang, Huanyu; Wu, Yunxiang; Zhu, Weiliang; Li, Yuanchao
2015-10-05
An unprecedented rhodium(III)-catalyzed regioselective redox-neutral annulation reaction of 1-naphthylamine N-oxides with diazo compounds was developed to afford various biologically important 1H-benzo[g]indolines. This coupling reaction proceeds under mild reaction conditions and does not require external oxidants. The only by-products are dinitrogen and water. More significantly, this reaction represents the first example of dual functiaonalization of unactivated a primary C(sp(3) )H bond and C(sp(2) )H bond with diazocarbonyl compounds. DFT calculations revealed that an intermediate iminium is most likely involved in the catalytic cycle. Moreover, a rhodium(III)-catalyzed coupling of readily available tertiary aniline N-oxides with α-diazomalonates was also developed under external oxidant-free conditions to access various aminomandelic acid derivatives by an O-atom-transfer reaction. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Shimizu, Masaki; Hirano, Koji; Satoh, Tetsuya; Miura, Masahiro
2009-05-01
The direct oxidative coupling of 2-amino- and 2-hydroxybenzoic acids with internal alkynes proceeds efficiently in the presence of a rhodium/copper catalyst system under air to afford the corresponding 8-substituted isocoumarin derivatives, some of which exhibit solid-state fluorescence. Depending on conditions, 4-ethenylcarbazoles can be synthesized selectively from 2-(arylamino)benzoic acids. The oxidative coupling reactions of heteroarene carboxylic acids as well as aromatic diacids with an alkyne are also described.
Daura-Oller, Elias; Segarra, Anna M; Poblet, Josep M; Claver, Carmen; Fernández, Elena; Bo, Carles
2004-04-16
We studied the hydroboration of vinylarenes using rhodium complexes bearing atropoisomeric ligands. For the first time, an NMR spectroscopy study of the styrene and catecholborane addition to the precursor of catalyst [Rh(COD)(L-L)]BF(4), where L-L = (R)-BINAP and (R)-QUINAP, showed evidence of the structure of intermediates involved in the catalytic cycle. On the basis of this evidence, and using DFT calculations and QM/MM strategies, we investigated the origin of regio- and stereoselectivity. We determined the structure and stability of the key intermediates for several ligands and substrates and found excellent agreement between the relative stability of the intermediates and the experimentally observed trends. Using model systems, we analyzed the role of the steric and electronic features of the ligands and the substrates in detail.
NASA Astrophysics Data System (ADS)
Laurent, B.; Losno, R.; Chevaillier, S.; Vincent, J.; Roullet, P.; Bon Nguyen, E.; Ouboulmane, N.; Triquet, S.; Fornier, M.; Raimbault, P.; Bergametti, G.
2015-07-01
Deposition is one of the key terms of the mineral dust cycle. However, dust deposition remains poorly constrained in transport models simulating the atmospheric dust cycle. This is mainly due to the limited number of relevant deposition measurements. This paper aims to present an automatic collector (CARAGA), specially developed to sample the total (dry and wet) atmospheric deposition of insoluble dust in remote areas. The autonomy of the CARAGA can range from 25 days to almost 1 year depending on the programmed sampling frequency (from 1 day to 2 weeks respectively). This collector is used to sample atmospheric deposition of Saharan dust on the Frioul islands in the Gulf of Lions in the Western Mediterranean. To quantify the mineral dust mass in deposition samples, a weighing and ignition protocol is applied. Almost 2 years of continuous deposition measurements performed on a weekly sampling basis on Frioul Island are presented and discussed with air mass trajectories and satellite observations of dust. Insoluble mineral deposition measured on Frioul Island was 2.45 g m-2 for February to December 2011 and 3.16 g m-2 for January to October 2012. Nine major mineral deposition events, measured during periods with significant MODIS aerosol optical depths, were associated with air masses coming from the southern Mediterranean Basin and North Africa.
Philippopoulos, Athanassios I.; Hadjiliadis, Nick; Hart, Claire E.; Donnadieu, Bruno; Mc Gowan, Patrick C.; Poilblanc, René
1997-04-23
The synthesis of monometallic rhodium(III) and rhodium(I) derivatives of dialkylamino-functionalized cyclopentadienyl using the corresponding cyclopentadiene as starting material is facilitated by the presence of the basic amino group. This procedure affords the chloro salts of the substituted rhodicinium cation [(eta(5)-C(5)H(4)(CH(2))(2)NMe(2)H)(2)Rh(III)](3+) ([1][Cl](3)) from the reaction of the [2-(dimethylamino)ethyl]cyclopentadiene with Na(3)Rh(III)Cl(6). 12H(2)O. Similarly the cationic half-sandwich complexes [(eta(5)-C(5)H(4)(CH(2))(n)()NMe(2)H)Rh(I)(cod)](+) (n = 2, [2][Cl], n = 3, [5][Cl]) are obtained from the reaction of the corresponding dialkylamino cyclopentadiene with [RhCl(cod)](2). These types of cationic complexes, 1, 2, and 5, bear pendant ammonium groups. The most classical procedure, starting from the lithium or more efficiently from the sodium cyclopentadienide salt, was used to synthesize neutral complexes [(eta(5)-C(5)H(4)(CH(2))(n)()NMe(2))Rh(I)(cod)] (n = 2, 3; n = 3, 4). The structure of the chloride bis(hexafluorophosphate) salt, [(eta(5)-C(5)H(4)(CH(2))(2)NMe(2)H)(2)Rh(III)](3+)(Cl(-))(PF(6)(-))(2), ([1][Cl][PF(6)](2)) was solved in the triclinic space group P&onemacr; with one molecule in the unit cell, the dimensions of which are a = 6.617(2) Å, b= 7.436(2) Å, c = 13.965(3) Å, alpha = 76.39(2) degrees, beta = 82.31(3) degrees, gamma = 87.26(2) degrees, and V = 661.8(3) Å(3). The noncentrosymmetric character of this solid is attributed to the chloride ion. The tetrafluoroborate salt [(eta(5)-C(5)H(4)(CH(2))(2)NMe(2)H)Rh(I)(cod)](+)(BF(4)(-)) ([2][BF(4)]) crystallizes in the tetragonal space group P4(2)/n with eight molecules in the unit cell, the dimensions of which are a= 21.183(2) Å, b = 21.179(3) Å, c= 8.324(2) Å, and V = 3734(1) Å(3). Least squares refinement leads to values for the conventional R index of [1][Cl][PF(6)](2) (0.0484 for 2191 reflections used) and of [2][BF(4)] (0.0525 for 1083 reflections used); in both
Schertzinger, Gerhard; Zimmermann, Sonja; Grabner, Daniel; Sures, Bernd
2017-11-01
The aim of this study was to investigate chronic effects of the platinum-group elements (PGE) palladium (Pd), platinum (Pt) and rhodium (Rh) on the nematode Caenorhabditis elegans. Aquatic toxicity testing was carried out according to ISO 10872 by determining 96 h EC 50 values for sublethal endpoints, including growth, fertility and reproduction. Single PGE standard solutions were used as metal source. Based on the EC 50 values for Pt, reproduction (96 h EC 50 = 497 μg/L) was the most sensitive endpoint followed by fertility (96 h EC 50 = 726 μg/L) and growth (96 h EC 50 = 808 μg/L). For Pd, no precise EC 50 values could be calculated due to bell-shaped concentration response curves, but the 96 h EC 50 for reproduction ranged between 10 and 100 μg/L. Pd and Pt had effects on all endpoints. With raising element concentrations reproduction was inhibited first. At a certain concentration, fertility was also affected, which in turn had an additional effect on reproduction. Growth inhibition can also lead to a loss of fertility if the worms do not reach an appropriate body size to become fertile. Rhodium showed no inhibition of any endpoint between concentrations of 100 to 10,000 μg Rh/L. The results of this study allow the following order of PGE with respect to decreasing toxicity to C. elegans: Pd > Pt » Rh. Copyright © 2017 Elsevier Ltd. All rights reserved.
Shu, Xing-Zhong; Shu, Dongxu; Schienebeck, Casi M.
2012-01-01
Transition metal-catalyzed acyloxy migration of propargylic esters offers versatile entries to allene and vinyl carbene intermediates for various fascinating subsequent transformations. Most π-acidic metals (e.g. gold and platinum) are capable of facilitating these acyloxy migration events. However, very few of these processes involve redox chemistry, which are well-known for most other transition metals such as rhodium. The coupling of acyloxy migration of propargylic esters with oxidative addition, migratory insertion, and reductive elimination may lead to ample new opportunities for the design of new reactions. This tutorial review summarizes recent developments in Rh-catalyzed 1,3- and 1,2-acyloxy migration of propargylic esters in a number of cycloaddition reactions. Related Au- and Pt-catalyzed cycloadditions involving acyloxy migration are also discussed. PMID:22895533
Yang, Hongjian; Hou, Shengtai; Tao, Cheng; Liu, Zhao; Wang, Chao; Cheng, Bin; Li, Yun; Zhai, Hongbin
2017-09-18
Rhodium-catalyzed denitrogenative [3+2] cycloaddition of 1-sulfonyl-1,2,3-triazoles with cyclic silyl dienol ethers has been developed for the synthesis of functionalized hydroindolones or their corresponding silyl ethers. The present method has been employed to construct synthetically valuable bicyclo[3.3.1]alkenone derivatives and pyrrolidine-ring-containing bicyclic indole compounds. As a further synthetic application, a stereoselective synthesis of 5,11-methanomorphanthridin-3-one, which shares a key skeleton with montanine-type Amaryllidaceae alkaloids has been achieved by using this chemistry. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Vohidov, Farrukh; Coughlin, Jane M; Ball, Zachary T
2015-04-07
Chemically modified proteins are increasingly important for use in fundamental biophysical studies, chemical biology, therapeutic protein development, and biomaterials. However, chemical methods typically produce heterogeneous labeling and cannot approach the exquisite selectivity of enzymatic reactions. While bioengineered methods are sometimes an option, selective reactions of natural proteins remain an unsolved problem. Here we show that rhodium(II) metallopeptides combine molecular recognition with promiscuous catalytic activity to allow covalent decoration of natural SH3 domains, depending on choice of catalyst but independent of the specific residue present. A metallopeptide catalyst succeeds in modifying a single SH3-containing kinase at endogenous concentrations in prostate cancer (PC-3) cell lysate. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Evans, P Andrew; Leahy, David K
2003-07-30
The transition metal-catalyzed allylic alkylation represents a fundamentally important cross-coupling reaction for the construction of ternary carbon stereogenic centers. We have developed a regioselective and enantiospecific rhodium-catalyzed allylic alkylation of acyclic unsymmetrical allylic alcohol derivatives using copper(I) enolates to prepare beta-substituted ketones. This protocol represents a convenient asymmetric Claisen rearrangement surrogate in which alpha-substituted enolates permit the introduction of an additional stereogenic center. The synthetic utility of this transformation was highlighted in the construction of a trans-1,2-disubstituted cyclohexene and the total synthesis of (-)-sugiresinol dimethyl ether. Finally, we anticipate that copper(I) enolates may prove useful nucleophiles in related metal-catalyzed reactions.
Huang, Xiaolei; Wang, Yan; Lan, Jingbo; You, Jingsong
2015-08-03
Disclosed herein is a Rh(III)-catalyzed chelation-assisted activation of unreactive C(sp3)-H bonds, thus enabling an intermolecular amidation to provide a practical and step-economic route to 2-(pyridin-2-yl)ethanamine derivatives. Substrates with other N-donor groups are also compatible with the amidation. This protocol proceeds at room temperature, has a relatively broad functional-group tolerance and high selectivity, and demonstrates the potential of rhodium(III) in the promotive functionalization of unreactive C(sp3)-H bonds. A rhodacycle having a SbF6(-) counterion was identified as a plausible intermediate. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
On the nature of carbon-hydrogen bond activation at rhodium and related reactions.
Jones, William D
2005-06-27
Over the past 20 years, substantial progress has been made in the understanding of the activation of C-H and other strong bonds by reactive metal complexes in low oxidation states. This paper will present an overview of the use of pentamethylcyclopentadienyl and trispyrazolylborate rhodium complexes for the activation of arene and alkane C-H bonds. Insights into bond strengths, kinetic and thermodynamic selectivities, and the nature of the intermediates involved will be reviewed. The role of eta-2 arene complexes will be shown to be critical to the C-H activation reactions. Some information about the fleeting alkane sigma-complexes will also be presented. In addition, use of these complexes with thiophenes has shown the ability to cleave C-S bonds. Mechanistic information has been obtained indicating coordination through sulfur prior to cleavage. Relevant examples of nickel-based C-S cleavage will also be given.
Li, Yi; Xu, Ming-Hua
2014-05-16
The first Rh-catalyzed asymmetric tandem cyclization of nitrogen- or oxygen-bridged 5-alkynones with arylboronic acids was achieved. The simple catalytic system involving a rhodium(I) complex with readily available chiral BINAP ligand promotes the reaction to proceed in a highly stereocontrolled manner. This protocol provides a very reliable and practical access to a variety of chiral heterocyclic tertiary allylic alcohols possessing a tetrasubstituted carbon stereocenter and an all-carbon tetrasubstituted olefin functionality in good yields with great enantioselectivities up to 99% ee.
NASA Technical Reports Server (NTRS)
Glawe, George E; Shepard, Charles E
1954-01-01
Thermocouples were exposed to exhaust gases from the combustion of propane, 72-octane gasoline, and JP-4 fuel. Exposure increased the emissivity of the thermocouple wire, which increased its radiation error. Two methods are presented for determining the emittance of the wires. The emissivity of a clean platinum rhodium-platinum thermocouple was approximately 0.2 in the temperature range investigated, while the emittance of an exposed thermocouple coated with exhaust residue was about 0.5. The exposure caused negligible change in the thermoelectric power of the thermocouples.
Shintani, Ryo; Yamagami, Takafumi; Kimura, Takahiro; Hayashi, Tamio
2005-11-10
[reaction: see text] The first catalytic asymmetric synthesis of 2-aryl-2,3-dihydro-4-quinolones has been developed by way of a rhodium-catalyzed 1,4-addition of arylzinc reagents to 4-quinolones. These 1,4-adducts can be obtained with high enantioselectivity by the use of (R)-binap as a ligand, and high yields are realized by conducting the reactions in the presence of chlorotrimethylsilane.
Shi, Yi; Gulevich, Anton V; Gevorgyan, Vladimir
2014-12-15
A general and efficient NH insertion reaction of rhodium pyridyl carbenes derived from pyridotriazoles was developed. Various NH-containing compounds, including amides, anilines, enamines, and aliphatic amines, smoothly underwent the NH insertion reaction to afford 2-picolylamine derivatives. The developed transformation was further utilized in a facile one-pot synthesis of imidazo[1,5-a]pyridines. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Lamb, Gareth; Clarke, Matthew; Slawin, Alexandra M Z; Williams, Bruce; Key, Lesley
2007-12-21
The carbonylation of methanol to acetic acid is a hugely important catalytic process, and there are considerable cost and environmental advantages if a process could be designed that was tolerant of hydrogen impurities in the CO feed gas, while eliminating by-products such as propionic acid and acetaldehyde altogether. This paper reports on an investigation into the application of rhodium complexes of several C(4) bridged diphosphines, namely BINAP, 1,4-bis(diphenylphosphino)butane (dppb), bis(diphenylphosphino)xylene (dppx) and 1,4-bis(dicyclohexylphosphino)butane (dcpb) as catalysts for hydrogen tolerant methanol carbonylation. An investigation into the structure, reactivity and stability of pre-catalysts and catalyst resting states of these complexes has also been carried out in order to understand the observations in catalysis. Rh(I) carbonyl halide complexes of each of the ligands have been prepared from both [Rh(2)(CO)(4)Cl(2)] and dimeric mu-Cl-[Rh(L)Cl](2) complexes. These Rh(I) carbonyl complexes are either dimeric with bridging phosphine ligands (dppb, dcpb, dppx) or monomeric chelate complexes. The reaction of the complexes with methyl iodide at 140 degrees C has been studied, which has revealed clear differences in the stability of the corresponding Rh(III) complexes. Surprisingly, the dimeric Rh(I) carbonyls react cleanly with MeI with rearrangement of the diphosphine to a chelate co-ordination mode to give stable Rh(III) acetyl complexes. The Rh acetyls for L=dppb and dppx have been fully characterised by X-ray crystallography. During the catalytic studies, the more rigid dppx and BINAP ligands were found to be nearly 5 times more hydrogen tolerant than [Rh(CO)(2)I(2)](-), as revealed by by-product analysis. The origin of this hydrogen tolerance is explained based on the differing reactivities of the Rh acetyls with hydrogen gas, and by considering the structure of the complexes.
Dynamics and Deposits of Coignimbrite Plumes
NASA Astrophysics Data System (ADS)
Engwell, Samantha; de'Michieli Vitturi, Mattia; Esposti Ongaro, Tomaso; Neri, Augusto
2014-05-01
Fine ash in the atmosphere poses a significant hazard, with potentially disastrous consequences for aviation and, on deposition, health and infrastructure. Fine-grained particles form a large proportion of ejecta in Plinian volcanic clouds. However, another common, but poorly studied phenomena exists whereby large amounts of fine ash are injected into the atmosphere. Coignimbrite plumes form as material is elutriated from the top of pyroclastic density currents. The ash in these plumes is considerably finer grained than that in Plinian plumes and can be distributed over thousands of kilometres in the atmosphere. Despite their significance, very little is known regarding coignimbrite plume formation and dispersion, predominantly due to the poor preservation of resultant deposits. As a result, consequences of coignimbrite plume formation are usually overlooked when conducting hazard and risk analysis. In this study, deposit characteristics and numerical models of plumes are combined to investigate the conditions required for coignimbrite plume formation. Coignimbrite deposits from the Campanian Ignimbrite eruption (Magnitude 7.7, 39 ka) are well sorted and very fine, with a mode of between 30 and 50 microns, and a significant component of respirable ash (less than 10 microns). Analogous distributions are found for coignimbrite deposits from Tungurahua 2006 and Volcan de Colima (2004-2006), amongst others, regardless of magnitude, type or chemistry of eruption. These results indicate that elutriation processes are the dominant control on coignimbrite grainsize distribution. To further investigate elutriation and coignimbrite plume dynamics, the numerical plume model of Bursik (2001) is applied. Model sensitivity analysis demonstrates that neutral buoyancy conditions (required for the formation of the plume) are controlled by a balance between temperature and gas mass flux in the upper most parts of the pyroclastic density current. In addition, results emphasize the
Navarre, Laure; Martinez, Rémi; Genet, Jean-Pierre; Darses, Sylvain
2008-05-14
Conjugate addition of potassium trifluoro(organo)borates 2 to dehydroalanine derivatives 1, mediated by a chiral rhodium catalyst and in situ enantioselective protonation, afforded straightforward access to a variety of protected alpha-amino esters 3 with high yields and enantiomeric excesses up to 95%. Among the tested chiral ligands and proton sources, Binap, in combination with guaiacol (2-methoxyphenol), an inexpensive and nontoxic phenol, afforded the highest asymmetric inductions. Organostannanes have also shown to participate in this reaction. By a fine-tuning of the ester moiety, and using Difluorophos as chiral ligand, increased levels of enantioselectivity, generally close to 95%, were achieved. Deuterium labeling experiments revealed, and DFT calculation supported, an unusual mechanism involving a hydride transfer from the amido substituent to the alpha carbon explaining the high levels of enantioselectivity attained in controlling this alpha chiral center.
The effects of two thick film deposition methods on tin dioxide gas sensor performance.
Bakrania, Smitesh D; Wooldridge, Margaret S
2009-01-01
This work demonstrates the variability in performance between SnO(2) thick film gas sensors prepared using two types of film deposition methods. SnO(2) powders were deposited on sensor platforms with and without the use of binders. Three commonly utilized binder recipes were investigated, and a new binder-less deposition procedure was developed and characterized. The binder recipes yielded sensors with poor film uniformity and poor structural integrity, compared to the binder-less deposition method. Sensor performance at a fixed operating temperature of 330 °C for the different film deposition methods was evaluated by exposure to 500 ppm of the target gas carbon monoxide. A consequence of the poor film structure, large variability and poor signal properties were observed with the sensors fabricated using binders. Specifically, the sensors created using the binder recipes yielded sensor responses that varied widely (e.g., S = 5 - 20), often with hysteresis in the sensor signal. Repeatable and high quality performance was observed for the sensors prepared using the binder-less dispersion-drop method with good sensor response upon exposure to 500 ppm CO (S = 4.0) at an operating temperature of 330 °C, low standard deviation to the sensor response (±0.35) and no signal hysteresis.
The Effects of Two Thick Film Deposition Methods on Tin Dioxide Gas Sensor Performance
Bakrania, Smitesh D.; Wooldridge, Margaret S.
2009-01-01
This work demonstrates the variability in performance between SnO2 thick film gas sensors prepared using two types of film deposition methods. SnO2 powders were deposited on sensor platforms with and without the use of binders. Three commonly utilized binder recipes were investigated, and a new binder-less deposition procedure was developed and characterized. The binder recipes yielded sensors with poor film uniformity and poor structural integrity, compared to the binder-less deposition method. Sensor performance at a fixed operating temperature of 330 °C for the different film deposition methods was evaluated by exposure to 500 ppm of the target gas carbon monoxide. A consequence of the poor film structure, large variability and poor signal properties were observed with the sensors fabricated using binders. Specifically, the sensors created using the binder recipes yielded sensor responses that varied widely (e.g., S = 5 – 20), often with hysteresis in the sensor signal. Repeatable and high quality performance was observed for the sensors prepared using the binder-less dispersion-drop method with good sensor response upon exposure to 500 ppm CO (S = 4.0) at an operating temperature of 330 °C, low standard deviation to the sensor response (±0.35) and no signal hysteresis. PMID:22399977
Sid Kalal, Hossein; Panahi, Homayon Ahmad; Hoveidi, Hassan; Taghiof, Mohammad; Menderjani, Mahnaz Taheri
2012-09-18
A new chelating resin was prepared by coupling Amberlite XAD-4 with alizarin red-s through an azo spacer, characterized by infra-red spectroscopy and thermal analysis and studied for Rh(III) preconcentration using inductively coupled plasma atomic emission spectroscopy (ICP-AES) for rhodium monitoring in the environment. The optimum pH for sorption of the metal ion was 6.5. The sorption capacity was found 2.1 mg/g of resin for Rh(III). A recovery of 88% was obtained for the metal ion with 1.5 M HCl as eluting agent. Kinetic adsorption data were analyzed by adsorption and desorption times of Rh(III) on modified resin. Scat chard analysis revealed that the homogeneous binding sites were formed in the polymers. The linear regression equation was Q/C = -1.3169Q + 27.222 (R2 = 0.9239), for Rh were formed in the SPE sorbent,Kd and Qmax for the affinity binding sites were calculated to be 0.76 μmol/mL and 20.67 μmol/g, respectively. The equilibrium data and parameters of Rh(III) adsorption on modified resin were analyzed by Langmuir, Freundlich, Temkin and Redlich-Peterson models. The experimental adsorption isotherm was in good concordance with Langmuir and Freundlich models (R2 > 0.998) and based on the Langmuir isotherm the maximum amount of adsorption (qmax) was 4.842 mg/g. The method was applied for rhodium ions determination in environmental samples. with high recovery (>80%).
2012-01-01
A new chelating resin was prepared by coupling Amberlite XAD-4 with alizarin red-s through an azo spacer, characterized by infra-red spectroscopy and thermal analysis and studied for Rh(III) preconcentration using inductively coupled plasma atomic emission spectroscopy (ICP-AES) for rhodium monitoring in the environment. The optimum pH for sorption of the metal ion was 6.5. The sorption capacity was found 2.1 mg/g of resin for Rh(III). A recovery of 88% was obtained for the metal ion with 1.5 M HCl as eluting agent. Kinetic adsorption data were analyzed by adsorption and desorption times of Rh(III) on modified resin. Scat chard analysis revealed that the homogeneous binding sites were formed in the polymers. The linear regression equation was Q/C = –1.3169Q + 27.222 (R2 = 0.9239), for Rh were formed in the SPE sorbent,Kd and Qmax for the affinity binding sites were calculated to be 0.76 μmol/mL and 20.67 μmol/g, respectively. The equilibrium data and parameters of Rh(III) adsorption on modified resin were analyzed by Langmuir, Freundlich, Temkin and Redlich–Peterson models. The experimental adsorption isotherm was in good concordance with Langmuir and Freundlich models (R2 > 0.998) and based on the Langmuir isotherm the maximum amount of adsorption (qmax) was 4.842 mg/g. The method was applied for rhodium ions determination in environmental samples. with high recovery (>80%). PMID:23369526
NASA Astrophysics Data System (ADS)
Tada, Kazuya; Onoda, Mitsuyoshi
2009-09-01
The material efficiency of electrophoretic deposition of a fluorene-based conjugated polymer, poly[(9,9-dioctyl-2,7-divinylenefluorenylene)-alt-{2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene}] (PDOF-MEHPV), from suspensions with a mixture of acetonitrile and toluene as dispersant is studied. It has been found that the recovery rate of the electrophoretic deposition from a suspension containing 90% of the poor solvent acetonitrile reaches 98%. Although the recovery rate decreases with decreasing acetonitrile content, almost 70% of the polymer can be deposited on the substrates from the suspension containing equivalent volumes of the good and poor solvents by electrophoretic deposition, from which smooth and transparent films suitable for electronic devices are obtained.
Yamano, Ryota; Shibata, Yu; Tanaka, Ken
2018-04-25
Dibenzo[7]helicenes were synthesized with up to 99 % ee by rhodium(I)/binap-catalyzed enantioselective intramolecular [2+2+2] cycloaddition of 2-phenylnaphthalene-linked triynes. Additionally, [2+1+2+1] cycloaddition products, that is, twisted anthracenes, were also synthesized by using difluorphos as ligand. Although these compounds are not configurationally stable at elevated temperature, their Scholl reactions afforded configurationally stable double dibenzo[6]helicenes. The thus-obtained dibenzo[7]helicene exhibited good circularly polarized luminescence property and the double dibenzo[6]helicene showed high fluorescence quantum yield. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Yang, Chao; Wang, Wanhe; Liang, Jia-Xin; Li, Guodong; Vellaisamy, Kasipandi; Wong, Chun-Yuen; Ma, Dik-Lung; Leung, Chung-Hang
2017-03-23
We report herein a novel rhodium(III) complex 1 as a new LSD1 targeting agent and epigenetic modulator. Complex 1 disrupted the interaction of LSD1-H3K4me2 in human prostate carcinoma cells and enhanced the amplification of p21, FOXA2, and BMP2 gene promoters. Complex 1 was selective for LSD1 over other histone demethylases, such as KDM2b, KDM7, and MAO activities, and also showed antiproliferative activity toward human cancer cells. To date, complex 1 is the first metal-based inhibitor of LSD1 activity.
Minus, Matthew B.; Liu, Wei; Vohidov, Farrukh; Kasembeli, Moses M.; Long, Xin; Krueger, Michael; Stevens, Alexandra; Kolosov, Mikhail I.; Sison, Edward Allen R.; Ball, Zachary T.
2015-01-01
Nearly 40% of children with acute myeloid leukemia (AML) suffer relapse due to chemoresistance, often involving upregulation of the oncoprotein STAT3 (signal transducer and activator of transcription 3). In this paper, rhodium(II)-catalyzed, proximity-driven modification identifies the STAT3 coiled-coil domain (CCD) as a novel ligand-binding site, and we describe a new naphthalene sulfonamide inhibitor that targets the CCD, blocks STAT3 function, and halts its disease-promoting effects in vitro, in tumor growth models, and in a leukemia mouse model, validating this new therapeutic target for resistant AML. PMID:26480340
Schultz, Erica E; Lindsay, Vincent N G; Sarpong, Richmond
2014-09-08
A general method for the formation of fused dihydroazepine derivatives from 1-sulfonyl-1,2,3-triazoles bearing a tethered diene is reported. The process involves an intramolecular cyclopropanation of an α-imino rhodium(II) carbenoid, leading to a transient 1-imino-2-vinylcyclopropane intermediate which rapidly undergoes a 1-aza-Cope rearrangement to generate fused dihydroazepine derivatives in moderate to excellent yields. The reaction proceeds with similar efficiency on gram scale. The use of catalyst-free conditions leads to the formation of a novel [4.4.0] bicyclic heterocycle. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Schäfer, Philipp; Palacin, Thomas; Sidera, Mireia; Fletcher, Stephen P.
2017-01-01
Using asymmetric catalysis to simultaneously form carbon–carbon bonds and generate single isomer products is strategically important. Suzuki-Miyaura cross-coupling is widely used in the academic and industrial sectors to synthesize drugs, agrochemicals and biologically active and advanced materials. However, widely applicable enantioselective Suzuki-Miyaura variations to provide 3D molecules remain elusive. Here we report a rhodium-catalysed asymmetric Suzuki-Miyaura reaction with important partners including aryls, vinyls, heteroaromatics and heterocycles. The method can be used to couple two heterocyclic species so the highly enantioenriched products have a wide array of cores. We show that pyridine boronic acids are unsuitable, but they can be halogen-modified at the 2-position to undergo reaction, and this halogen can then be removed or used to facilitate further reactions. The method is used to synthesize isoanabasine, preclamol, and niraparib—an anticancer agent in several clinical trials. We anticipate this method will be a useful tool in drug synthesis and discovery. PMID:28607510
NASA Astrophysics Data System (ADS)
Schäfer, Philipp; Palacin, Thomas; Sidera, Mireia; Fletcher, Stephen P.
2017-06-01
Using asymmetric catalysis to simultaneously form carbon-carbon bonds and generate single isomer products is strategically important. Suzuki-Miyaura cross-coupling is widely used in the academic and industrial sectors to synthesize drugs, agrochemicals and biologically active and advanced materials. However, widely applicable enantioselective Suzuki-Miyaura variations to provide 3D molecules remain elusive. Here we report a rhodium-catalysed asymmetric Suzuki-Miyaura reaction with important partners including aryls, vinyls, heteroaromatics and heterocycles. The method can be used to couple two heterocyclic species so the highly enantioenriched products have a wide array of cores. We show that pyridine boronic acids are unsuitable, but they can be halogen-modified at the 2-position to undergo reaction, and this halogen can then be removed or used to facilitate further reactions. The method is used to synthesize isoanabasine, preclamol, and niraparib--an anticancer agent in several clinical trials. We anticipate this method will be a useful tool in drug synthesis and discovery.
Rhodium(I)-Complexes Catalyzed 1,4-Conjugate Addition of Arylzinc Chlorides to N-Boc-4-pyridone.
Guo, Fenghai; McGilvary, Matthew A; Jeffries, Malcolm C; Graves, Briana N; Graham, Shekinah A; Wu, Yuelin
2017-05-01
Rhodium(I)-complexes catalyzed the 1,4-conjugate addition of arylzinc chlorides to N -Boc-4-pyridone in the presence of chlorotrimethylsilane (TMSCl). A combination of [RhCl(C₂H₄)₂]₂ and BINAP was determined to be the most effective catalyst to promote the 1,4-conjugate addition reactions of arylzinc chlorides to N -Boc-4-pyridone. A broad scope of arylzinc reagents with both electron-withdrawing and electron-donating substituents on the aromatic ring successfully underwent 1,4-conjugate addition to N -Boc-4-pyridone to afford versatile 1,4-adducts 2-substituted-2,3-dihydropyridones in good to excellent yields (up to 91%) and excellent ee (up to 96%) when ( S )-BINAP was used as chiral ligand.
NASA Astrophysics Data System (ADS)
Barte, Ellie Floyd; Hara, Hiroyuki; Tamura, Toshiki; Gisuji, Takuya; Chen, When-Bo; Lokasani, Ragava; Hatano, Tadashi; Ejima, Takeo; Jiang, Weihua; Suzuki, Chihiro; Li, Bowen; Dunne, Padraig; O'Sullivan, Gerry; Sasaki, Akira; Higashiguchi, Takeshi; Limpouch, Jiří
2018-05-01
We have characterized the soft x-ray and extreme ultraviolet (XUV) emission of rhodium (Rh) plasmas produced using dual pulse irradiation by 150-ps or 6-ns pre-pulses, followed by a 150-ps main pulse. We have studied the emission enhancement dependence on the inter-pulse time separation and found it to be very significant for time separations less than 10 ns between the two laser pulses when using 6-ns pre-pulses. The behavior using a 150-ps pre-pulse was consistent with such plasmas displaying only weak self-absorption effects in the expanding plasma. The results demonstrate the advantage of using dual pulse irradiation to produce the brighter plasmas required for XUV applications.
Deposition Rates and Characterization of Arabian Mineral Dust
NASA Astrophysics Data System (ADS)
Puthan Purakkal, J.; Stenchikov, G. L.; Engelbrecht, J. P.
2015-12-01
Airborne mineral dust directly and indirectly impacts on global climate, continental and marine biochemistry, human and animal health, agriculture, equipment, and visibility. Annual global dust emissions are poorly known with estimates differing by a factor of at least two. Local dust emission and deposition rates are even less quantified. Dust deposition rate is a key parameter, which helps to constrain the modeled dust budget of the atmosphere. However, dust deposition remains poorly known, due to the limited number of reliable measurements. Simulations and satellite observations suggest that coastal dusts contribute substantially to the total deposition flux into the Red Sea. Starting December 2014, deposition samplers, both the "frisbee" type, and passive samplers for individual particle scanning electron microscopy were deployed at King Abdullah University of Science and Technology (KAUST), along the Red Sea in Saudi Arabia. Sampling periods of one month were adopted. The deposition rates range from 3 g m-2 month-1 for fair weather conditions to 23 g m-2 month-1 for high dust events. The X-ray diffraction (XRD) analyses of deposited dust samples show mineralogical compositions different from any of the parent soils, the former consisting mainly of gypsum, calcite, and smaller amounts of albite, montmorillonite, chlorite, quartz and biotite. The deposited dust samples on the other hand contain more gypsum and less quartz than the previously collected soil samples. This presentation discusses the results from XRD, chemical analysis and SEM-based individual particle analysis of the soils and the deposited dust samples. The monthly dust accumulation rates and their seasonal and spatial variability are compared with the regional model predictions. Data from this study provide an observational basis for validating the regional dust mass balance along the Arabian Red Sea coastal plain.
Relationship between geomorphology and lithotypes of lahar deposit from Chokai volcano, Japan
NASA Astrophysics Data System (ADS)
Minami, Y.; Ohba, T.; Hayashi, S.; Kataoka, K.
2013-12-01
Chokai volcano, located in the northern Honshu arc in Japan, is an andesitic stratovolcano that collapsed partly at ca. 2500 years ago. A post collapse lahar deposit (Shirayukigawa lahar deposit) is distributed in the northern foot of the volcanic edifice. The deposit consists of 16 units of debris flow, hyperconcentrated flow and streamflow deposits. The Shirayukigawa lahar deposit has a total thickness of 30 m and overlies the 2.5-ka Kisakata debris avalanche deposit. Shirayukigawa lahar deposit forms volcanic fan and volcanic apron. The volcanic fan is subdivided into four areas on the basis of slope angles and of geomorphological features: 1) steeply sloped area, 2) moderately sloped area, 3) gently sloped area and 4) horizontal area. From sedimentary facies and structures, each unit of the Shirayukigawa lahar deposit is classified into one of four lithotypes: clast-supported debris flow deposit (Cc), matrix-supported debris flow deposit (Cm1), hyperconcentrated flow deposit (Cm2) and streamflow deposit (Sl). Each type has the following lithological characteristics. The lithotypes are well correlated with the geomorphology of the volcanic fan. The steeply-sloped and the moderately-sloped areas are dominated by Cc, Cm1, and Cm2, and The horizontal area are dominated by Sl. Debris flow deposit (Cc) is massive, very poorly sorted, partly graded, and clast-supported with polymictic clasts dominated by subrounded to rounded volcanic clasts. Matrix is sandy to muddy. Preferred clast orientation are present. Debris flow deposit (Cm1) is massive, very poorly sorted, and matrix-supported with polymictic clasts dominated by subrounded to rounded volcanic clasts. Matrix is sandy to muddy. Some layers exhibit coarse-tail normal/inverse grading. Most clasts are oriented. Hyperconcentrated flow deposit (Cm2) is massive to diffusely laminated, very poorly sorted and matrix-supported with polymictic clasts dominated by subrounded to rounded volcanic rocks. Matrix is sandy. The
Classification of Broken Hill-Type Pb-Zn-Ag Deposits: A Refinement
NASA Astrophysics Data System (ADS)
Spry, P. G.; Teale, G. S.; Steadman, J. A.
2009-05-01
Broken Hill Hill-type Pb-Zn-Ag (BHT) deposits constitute some of the largest ore deposits in the world. The Broken Hill deposit is the largest accumulation of Pb, Zn, and Ag on Earth and the Cannington deposit is currently the largest silver deposit. Characteristic features of BHT deposits include: 1. high Pb+Zn+Ag values with Pb > Zn; 2. Metamorphism to amphibolite-granulite facies; 3. Paleo-to Mesoprotoerozoic clastic metasedimentary host rocks; 4. Sulfides that are spatially associated with bimodal (felsic and mafic) volcanic rocks, and stratabound gahnite- and garnet-bearing rocks and iron formations, 5. Stacked orebodies with characteristic Pb:Zn:Ag ratios and skarn-like Fe-Mn-Ca-F gangue assemblages, and the presence of Cu, Au, Bi, As, and Sb; and 6. Sulfur-poor assemblages. Broken Hill (Australia) has a prominent footwall feeder zone whereas other BHT deposits have less obvious alteration zones (footwall garnet spotting and stratabound alteration haloes). Deposits previously regarded in the literature as BHT deposits are Broken Hill, Cannington, Oonagalabie, Menninie Dam, and Pegmont (Australia), Broken Hill, Swartberg, Big Syncline, and Gamsberg (South Africa), Zinkgruvan (Sweden), Sullivan, Cottonbelt, and Foster River (Canada), and Boquira (Brazil). Of these deposits, only the Broken Hill (Australia, South Africa), Pinnacles, Cannington, Pegmont, and Swartberg deposits are BHT deposits. Another BHT deposit includes the Green Parrot deposit, Jervois Ranges (Northern Territory). The Foster River, Gamsberg, and Sullivan deposits are considered to be "SEDEX deposits with BHT affinities", and the Oonagalabie, Green Mountain (Colorado), and Zinkgruvan are "VMS deposits with BHT affinities". In the Broken Hill area (Australia), Corruga-type Pb-Zn-Ag deposits occur in calc-silicate rocks and possess some BHT characteristics; the Big Syncline, Cottonbelt, Menninie Dam, and Saxberget deposits are Corruga-type deposits. SEDEX deposits with BHT affinities, VMS
Long term response of acid-sensitive Vermont Lakes to sulfate deposition
Atmospheric deposition of sulfur can negatively affect the health of lakes and streams, particularly in poorly buffered catchments. In response to the Clean Air Act Amendments, wet deposition of sulfate decreased more than 35% in Vermont between 1990 and 2008. However, most of ...
Deposited films with improved microstructures
Patten, James W.; Moss, Ronald W.; McClanahan, Edwin D.
1984-01-01
Methods for improving microstructures of line-of-sight deposited films are described. Columnar growth defects ordinarily produced by geometrical shadowing during deposition of such films are eliminated without resorting to post-deposition thermal or mechanical treatments. The native, as-deposited coating qualities, including homogeneity, fine grain size, and high coating-to-substrate adherence, can thus be retained. The preferred method includes the steps of emitting material from a source toward a substrate to deposit a coating non-uniformly on the substrate surface, removing a portion of the coating uniformly over the surface, again depositing material onto the surface, but from a different direction, and repeating the foregoing steps. The quality of line-of-sight deposited films such as those produced by sputtering, progressively deteriorates as the angle of incidence between the flux and the surface becomes increasingly acute. Depositing non-uniformly, so that the coating becomes progressively thinner as quality deteriorates, followed by uniformly removing some of the coating, such as by resputtering, eliminates the poor quality portions, leaving only high quality portions of the coating. Subsequently sputtering from a different direction applies a high quality coating to other regions of the surface. Such steps can be performed either simultaneously or sequentially to apply coatings of a uniformly high quality, closed microstructure to three-dimensional or large planar surfaces.
Sun, Run; Jiang, Yu; Tang, Xiang-Ying; Shi, Min
2016-04-11
New rhodium(II)-catalyzed or thermally induced intramolecular alkoxy group migration of N-sulfonyl-1,2,3-triazoles has been developed, affording divergent synthesis of 1,2-dihydroisoquinoline and 1-indanone derivatives according to different conditions. N-Sulfonyl keteneimine is the key intermediate for the synthesis of dihydroisoquinoline, whereas the aza-vinyl carbene intermediate results in the formation of 1-indanone. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Zhou, Yirong; Breit, Bernhard
2017-12-22
An unprecedented asymmetric N-H functionalization of quinazolinones with allenes and allylic carbonates was successfully achieved by rhodium catalysis with the assistance of chiral bidentate diphosphine ligands. The high efficiency and practicality of this method was demonstrated by a low catalyst loading of 1 mol % as well as excellent chemo-, regio-, and enantioselectivities with broad functional group compatibility. Furthermore, this newly developed strategy was applied as key step in the first enantioselective formal total synthesis of (-)-chaetominine. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Hapfty, J.; Riley, L.B.
1968-01-01
A method is described for the determination of palladium down to 4ppb (parts per billion, 109), platinum down to 10 ppb and rhodium down to 5 ppb in 15 g of sample. Fire-assay techniques are used to preconcentrate the platinum metals into a gold bead, then the bead is dissolved in aqua regia and diluted to volume with 1M hydrochloric acid. The solution is analysed by optical emission spectrography of the residue from 200 ??l of it evaporated on a pair of flat-top graphite electrodes. This method requires much less sample handling than most published methods for these elements. Data are presented for G-1, W-1, and six new standard rocks of the U.S. Geological Survey. The values for palladium in W-1 are in reasonable agreement with previously published data. ?? 1968.
Chaves, Natalia L; Estrela-Lopis, Irina; Böttner, Julia; Lopes, Cláudio Ap; Guido, Bruna C; de Sousa, Aparecido R; Báo, Sônia N
2017-01-01
Nanocarriers have the potential to improve the therapeutic index of currently available drugs by improving their efficacy and achieving therapeutic steady-state levels over an extended period. The association of maghemite-rhodium citrate (MRC) nanoparticles (NPs) has the potential to increase specificity of the cytotoxic action. However, the interaction of these NPs with cells, their uptake mechanism, and subcellular localization need to be elucidated. This work evaluates the uptake mechanism of MRC NPs in metastatic and nonmetastatic breast cancer-cell models, comparing them to a nontumor cell line. MRC NPs uptake in breast cancer cells was more effective than in normal cells, with regard to both the amount of internalized material and the achievement of more strategic intracellular distribution. Moreover, this process occurred through a clathrin-dependent endocytosis pathway with different basal expression levels of this protein in the cell lines tested.
Aerosol Deposition in Health and Disease
2012-01-01
Abstract The success of inhalation therapy is not only dependent upon the pharmacology of the drugs being inhaled but also upon the site and extent of deposition in the respiratory tract. This article reviews the main mechanisms affecting the transport and deposition of inhaled aerosol in the human lung. Aerosol deposition in both the healthy and diseased lung is described mainly based on the results of human studies using nonimaging techniques. This is followed by a discussion of the effect of flow regime on aerosol deposition. Finally, the link between therapeutic effects of inhaled drugs and their deposition pattern is briefly addressed. Data show that total lung deposition is a poor predictor of clinical outcome, and that regional deposition needs to be assessed to predict therapeutic effectiveness. Indeed, spatial distribution of deposited particles and, as a consequence, drug efficiency is strongly affected by particle size. Large particles (>6 μm) tend to mainly deposit in the upper airway, limiting the amount of drugs that can be delivered to the lung. Small particles (<2 μm) deposit mainly in the alveolar region and are probably the most apt to act systemically, whereas the particle in the size range 2–6 μm are be best suited to treat the central and small airways. PMID:22686623
Mitsumi, Minoru; Ezaki, Kazunari; Komatsu, Yuuki; Toriumi, Koshiro; Miyatou, Tatsuya; Mizuno, Motohiro; Azuma, Nobuaki; Miyazaki, Yuji; Nakano, Motohiro; Kitagawa, Yasutaka; Hanashima, Takayasu; Kiyanagi, Ryoji; Ohhara, Takashi; Nakasuji, Kazuhiro
2015-06-26
A newly synthesized one-dimensional (1D) hydrogen-bonded (H-bonded) rhodium(II)-η(5)-semiquinone complex, [Cp*Rh(η(5)-p-HSQ-Me4)]PF6 ([1]PF6; Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl; HSQ = semiquinone) exhibits a paraelectric-antiferroelectric second-order phase transition at 237.1 K. Neutron and X-ray crystal structure analyses reveal that the H-bonded proton is disordered over two sites in the room-temperature (RT) phase. The phase transition would arise from this proton disorder together with rotation or libration of the Cp* ring and PF6(-) ion. The relative permittivity εb' along the H-bonded chains reaches relatively high values (ca., 130) in the RT phase. The temperature dependence of (13)C CP/MAS NMR spectra demonstrates that the proton is dynamically disordered in the RT phase and that the proton exchange has already occurred in the low-temperature (LT) phase. Rate constants for the proton exchange are estimated to be 10(-4)-10(-6) s in the temperature range of 240-270 K. DFT calculations predict that the protonation/deprotonation of [1](+) leads to interesting hapticity changes of the semiquinone ligand accompanied by reduction/oxidation by the π-bonded rhodium fragment, producing the stable η(6)-hydroquinone complex, [Cp*Rh(3+)(η(6)-p-H2Q-Me4)](2+) ([2](2+)), and η(4)-benzoquinone complex, [Cp*Rh(+)(η(4)-p-BQ-Me4)] ([3]), respectively. Possible mechanisms leading to the dielectric response are discussed on the basis of the migration of the protonic solitons comprising of [2](2+) and [3], which would be generated in the H-bonded chain. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Study of activation cross-sections of deuteron induced reactions on rhodium up to 40 MeV
NASA Astrophysics Data System (ADS)
Ditrói, F.; Tárkányi, F.; Takács, S.; Hermanne, A.; Yamazaki, H.; Baba, M.; Mohammadi, A.; Ignatyuk, A. V.
2011-09-01
In the frame of a systematic study of the activation cross-sections of deuteron induced nuclear reactions, excitation functions of the 103Rh(d,x) 100,101,103Pd, 100g,101m,101g,102m,102gRh and 103gRu reactions were determined up to 40 MeV. Cross-sections were measured with the activation method using a stacked foil irradiation technique. Excitation functions of the contributing reactions were calculated using the ALICE-IPPE, EMPIRE-II and TALYS codes. From the measured cross-section data integral production yields were calculated and compared with experimental integral yield data reported in the literature. From the measured cross-sections and previous data, activation curves were deduced to support thin layer activation (TLA) on rhodium and Rh containing alloys.
Minus, Matthew B; Liu, Wei; Vohidov, Farrukh; Kasembeli, Moses M; Long, Xin; Krueger, Michael J; Stevens, Alexandra; Kolosov, Mikhail I; Tweardy, David J; Sison, Edward Allan R; Redell, Michele S; Ball, Zachary T
2015-10-26
Nearly 40 % of children with acute myeloid leukemia (AML) suffer relapse arising from chemoresistance, often involving upregulation of the oncoprotein STAT3 (signal transducer and activator of transcription 3). Herein, rhodium(II)-catalyzed, proximity-driven modification identifies the STAT3 coiled-coil domain (CCD) as a novel ligand-binding site, and we describe a new naphthalene sulfonamide inhibitor that targets the CCD, blocks STAT3 function, and halts its disease-promoting effects in vitro, in tumor growth models, and in a leukemia mouse model, validating this new therapeutic target for resistant AML. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Aïssa, Christophe; Ho, Kelvin Y T; Tetlow, Daniel J; Pin-Nó, María
2014-04-14
The use of α,ω-dienes as functionalization reagents for olefinic carbon-hydrogen bonds has been rarely studied. Reported herein is the rhodium(I)-catalyzed rearrangement of prochiral 1,6-heptadienes into [2,2,1]-cycloheptane derivatives with concomitant creation of at least three stereogenic centers and complete diastereocontrol. Deuterium-labeling studies and the isolation of a key intermediate are consistent with a group-directed C-H bond activation, followed by two consecutive migratory insertions, with only the latter step being diastereoselective. © 2014 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Haydl, Alexander M; Hilpert, Lukas J; Breit, Bernhard
2016-05-04
The rhodium-catalyzed asymmetric N-selective coupling of pyrazole derivatives with internal and terminal alkynes features an utmost chemo-, regio-, and enantioselective access to enantiopure allylic pyrazoles, readily available for incorporation in small-molecule pharmaceuticals. This methodology is distinguished by a broad substrate scope, resulting in a remarkable compatability with a variety of different functional groups. It furthermore exhibits an intriguing case of regio-, position-, and enantioselectivity in just one step, underscoring the sole synthesis of just one out of up to six possible products in a highly flexible approach to allylated pyrazoles by emanating from various internal and terminal alkynes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Pettinari, Riccardo; Marchetti, Fabio; Pettinari, Claudio; Condello, Francesca; Petrini, Agnese; Scopelliti, Rosario; Riedel, Tina; Dyson, Paul J
2015-12-21
A series of half-sandwich cyclopentadienyl rhodium(III) and iridium(III) complexes of the type [Cp*M(curc/bdcurc)Cl] and [Cp*M(curc/bdcurc)(PTA)][SO3CF3], in which Cp* = pentamethylcyclopentadienyl, curcH = curcumin and bdcurcH = bisdemethoxycurcumin as O^O-chelating ligands, and PTA = 1,3,5-triaza-7-phosphaadamantane, is described. The X-ray crystal structures of three of the complexes, i.e. [Cp*Rh(curc)(PTA)][SO3CF3] (5), [Cp*Rh(bdcurc)(PTA)][SO3CF3] (6) and [Cp*Ir(bdcurc)(PTA)][SO3CF3] (8), confirm the expected "piano-stool" geometry. With the exception of 5, the complexes are stable under pseudo-physiological conditions and are moderately cytotoxic to human ovarian carcinoma (A2780 and A2780cisR) cells and also to non-tumorigenic human embryonic kidney (HEK293) cells, but lack the cancer cell selectivity observed for related arene ruthenium(II) complexes.
MgF2 prism/rhodium/graphene: efficient refractive index sensing structure in optical domain
NASA Astrophysics Data System (ADS)
Mishra, Akhilesh Kumar; Mishra, Satyendra Kumar
2017-04-01
A theoretical study of a noble surface plasmon resonance (SPR) based sensing probe has been carried out. The sensing probe consists of a magnesium fluoride (MgF2) prism with its base coated with rarely used noble metal rhodium (Rh) and a bio-compatible layer of graphene. The refractive indices (RIs) of the sensing medium vary from 1.33 to 1.36 refractive index unit (RIU). The thickness of Rh and the number of graphene layers have been optimized for maximum sensitivity in a constraint set by the detection accuracy (DA). For the operating wavelength of 632 nm, the optimized sensing probe Rh (12 nm)/graphene (single layer) demonstrates sensitivity of ~259 degree/RIU with corresponding DA of ~0.32 degree-1 while for 532 nm of excitation, the optimized sensing probe Rh (12 nm)/graphene (three layer) exhibits sensitivity of ~240 degree/RIU and DA of ~0.27 degree-1.
MgF2 prism/rhodium/graphene: efficient refractive index sensing structure in optical domain.
Mishra, Akhilesh Kumar; Mishra, Satyendra Kumar
2017-04-12
A theoretical study of a noble surface plasmon resonance (SPR) based sensing probe has been carried out. The sensing probe consists of a magnesium fluoride (MgF 2 ) prism with its base coated with rarely used noble metal rhodium (Rh) and a bio-compatible layer of graphene. The refractive indices (RIs) of the sensing medium vary from 1.33 to 1.36 refractive index unit (RIU). The thickness of Rh and the number of graphene layers have been optimized for maximum sensitivity in a constraint set by the detection accuracy (DA). For the operating wavelength of 632 nm, the optimized sensing probe Rh (12 nm)/graphene (single layer) demonstrates sensitivity of ~259 degree/RIU with corresponding DA of ~0.32 degree -1 while for 532 nm of excitation, the optimized sensing probe Rh (12 nm)/graphene (three layer) exhibits sensitivity of ~240 degree/RIU and DA of ~0.27 degree -1 .
Wang, Yi; Yu, Zhi-Xiang
2015-08-18
Practical syntheses of natural products and their analogues with eight-membered carbocyclic skeletons are important for medicinal and biological investigations. However, methods and strategies to construct the eight-membered carbocycles are limited. Therefore, developing new methods to synthesize the eight-membered carbocycles is highly desired. In this Account, we describe our development of three rhodium-catalyzed cycloadditions for the construction of the eight-membered carbocycles, which have great potential in addressing the challenges in the synthesis of medium-sized ring systems. The first reaction described in this Account is our computationally designed rhodium-catalyzed two-component [5 + 2 + 1] cycloaddition of ene-vinylcyclopropanes (ene-VCPs) and CO for the diastereoselective construction of bi- and tricyclic cyclooctenones. The design of this reaction is based on the hypothesis that the C(sp(3))-C(sp(3)) reductive elimination of the eight-membered rhodacycle intermediate generated from the rhodium-catalyzed cyclopropane cleavage and alkene insertion, giving Wender's [5 + 2] cycloadduct, is not easy. Under CO atmosphere, CO insertion may occur rapidly, converting the eight-membered rhodacycle into a nine-membered rhodacycle, which then undergoes an easy C(sp(2))-C(sp(3)) reductive elimination process and furnishes the [5 + 2 + 1] product. This hypothesis was supported by our preliminary DFT studies and also served as inspiration for the development of two [7 + 1] cycloadditions: the [7 + 1] cycloaddition of buta-1,3-dienylcyclopropanes (BDCPs) and CO for the construction of cyclooctadienones, and the benzo/[7 + 1] cycloaddition of cyclopropyl-benzocyclobutenes (CP-BCBs) and CO to synthesize the benzocyclooctenones. The efficiency of these rhodium-catalyzed cycloadditions can be revealed by the application in natural product synthesis. Two eight-membered ring-containing natural products, (±)-asterisca-3(15),6-diene and (+)-asteriscanolide, have been
Marsh, Erin; Hitzman, Murray W.; Leach, David L.
2016-01-01
Some sediment-hosted base metal deposits, specifically the clastic-dominated (CD) Zn-Pb deposits, carbonate-hosted Mississippi Valley-type (MVT) deposits, sedimentary-rock hosted stratiform copper deposits, and carbonate-hosted polymetallic (“Kipushi type”) deposits, are or have been important sources of critical elements including Co, Ga, Ge, and Re. The generally poor data concerning trace element concentrations in these types of sediment-hosted ores suggest that there may be economically important concentrations of critical elements yet to be recognized.
THE IMMIGRANT POOR AND THE RESIDUAL POOR.
ERIC Educational Resources Information Center
SEGALMAN, RALPH
AN ANALYSIS OF THE LIVES OF THE POOR IN AMERICA WILL SHOW DIFFERENCES BETWEEN THE IMMIGRANT (AND REFUGEE) POOR AND THE RESIDUAL POOR (NEGROES, PUERTO RICANS, LATIN AMERICANS, INDIANS, AND OTHERS). THE IMMIGRANT POOR WERE ACCULTURATED AND ABSORBED INTO THE MAINSTREAM OF AMERICAN LIFE WITHIN THREE GENERATIONS, WHEREAS THE RESIDUAL POOR HAVE BEEN…
Reactivity Control of Rhodium Cluster Ions by Alloying with Tantalum Atoms.
Mafuné, Fumitaka; Tawaraya, Yuki; Kudoh, Satoshi
2016-02-18
Gas phase, bielement rhodium and tantalum clusters, RhnTam(+) (n + m = 6), were prepared by the double laser ablation of Rh and Ta rods in He carrier gas. The clusters were introduced into a reaction gas cell filled with nitric oxide (NO) diluted with He and were subjected to collisions with NO and He at room temperature. The product species were observed by mass spectrometry, demonstrating that the NO molecules were sequentially adsorbed on the RhnTam(+) clusters to form RhnTam(+)NxOx (x = 1, 2, 3, ...) species. In addition, oxide clusters, RhnTam(+)O2, were also observed, suggesting that the NO molecules were dissociatively adsorbed on the cluster, the N atoms migrated on the surface to form N2, and the N2 molecules were released from RhnTam(+)N2O2. The reactivity, leading to oxide formation, was composition dependent: oxide clusters were dominantly formed for the bielement clusters containing both Rh and Ta atoms, whereas such clusters were hardly formed for the single-element Rhn(+) and Tam(+) clusters. DFT calculations indicated that the Ta atoms induce dissociation of NO on the clusters by lowering the dissociation energy, whereas the Rh atoms enable release of N2 by lowering the binding energy of the N atoms on the clusters.
Preetz, Angelika; Drexler, Hans-Joachim; Fischer, Christian; Dai, Zhenya; Börner, Armin; Baumann, Wolfgang; Spannenberg, Anke; Thede, Richard; Heller, Detlef
2008-01-01
The use of diolefin-containing rhodium precatalysts leads to induction periods in asymmetric hydrogenation of prochiral olefins. Consequently, the reaction rate increases in the beginning. The induction period is caused by the fact that some of the catalyst is blocked by the diolefin and thus not available for hydrogenation of the prochiral olefin. Therefore, the maximum reaction rate cannot be reached initially. Due to the relatively slow hydrogenation of cyclooctadiene (cod) the share of active catalysts increases at first, and this leads to typical induction periods. The aim of this work is to quantify the hydrogenation of the diolefins cyclooctadiene (cod) and norborna-2,5-diene (nbd) for cationic complexes of the type [Rh(ligand)(diolefin)]BF(4) for the ligands Binap (1,1'-binaphthalene-2,2'-diylbis(phenylphosphine)), Me-Duphos (1,2-bis(2,5-dimethylphospholano)benzene, and Catasium in the solvents methanol, THF, and propylene carbonate. Furthermore, an approach is presented to determine the desired rate constant and the resulting respective pre-hydrogenation time from stoichiometric hydrogenations of the diolefin complexes via UV/Vis spectroscopy. This method is especially useful for very slow diolefin hydrogenations (e.g., cod hydrogenation with the ligands Me-Duphos, Et-Duphos (1,2-bis(2,5-diethylphospholano)benzene), and dppe (1,2-bis(diphenylphosphino)ethane).
Parr, Brendan T.; Davies, Huw M. L.
2014-01-01
Stereoselective synthesis of a cyclopentane nucleus by convergent annulations constitutes a significant challenge for synthetic chemists. Though a number of biologically relevant cyclopentane natural products are known, more often than not, the cyclopentane core is assembled in a stepwise fashion due to lack of efficient annulation strategies. Herein, we report the rhodium-catalyzed reactions of vinyldiazoacetates with (E)-1,3-disubstituted 2-butenols generate cyclopentanes, containing four new stereogenic centers with very high levels of stereoselectivity (99% ee, >97 : 3 dr). The reaction proceeds by a carbene–initiated domino sequence consisting of five distinct steps: rhodium–bound oxonium ylide formation, [2,3]-sigmatropic rearrangement, oxy-Cope rearrangement, enol–keto tautomerization, and finally an intramolecular carbonyl ene reaction. A systematic study is presented detailing how to control chirality transfer in each of the four stereo-defining steps of the cascade, consummating in the development of a highly stereoselective process. PMID:25082301
Chaves, Natalia L; Estrela-Lopis, Irina; Böttner, Julia; Lopes, Cláudio AP; Guido, Bruna C; de Sousa, Aparecido R; Báo, Sônia N
2017-01-01
Nanocarriers have the potential to improve the therapeutic index of currently available drugs by improving their efficacy and achieving therapeutic steady-state levels over an extended period. The association of maghemite–rhodium citrate (MRC) nanoparticles (NPs) has the potential to increase specificity of the cytotoxic action. However, the interaction of these NPs with cells, their uptake mechanism, and subcellular localization need to be elucidated. This work evaluates the uptake mechanism of MRC NPs in metastatic and nonmetastatic breast cancer-cell models, comparing them to a nontumor cell line. MRC NPs uptake in breast cancer cells was more effective than in normal cells, with regard to both the amount of internalized material and the achievement of more strategic intracellular distribution. Moreover, this process occurred through a clathrin-dependent endocytosis pathway with different basal expression levels of this protein in the cell lines tested. PMID:28814867
He, Qijie; So, Chau Ming; Bian, Zhaoxiang; Hayashi, Tamio; Wang, Jun
2015-03-01
Chromone has been noted to be one of the most challenging substrates in the asymmetric 1,4-addition of α,β-unsaturated carbonyl compounds. By employing the rhodium complex associated with a chiral diene ligand, (R,R)-Ph-bod*, the 1,4-addition of a variety of arylboronic acids was realized to give high yields of the corresponding flavanones with excellent enantioselectivities (≥97% ee, 99% ee for most substrates). Ring-opening side products, which would lead to erosion of product enantioselectivity, were not observed under the stated reaction conditions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
NASA Technical Reports Server (NTRS)
Dellacorte, Christhopher; Steinetz, Bruce M.; Brindley, Pamela K.
1990-01-01
Tribological properties of Ti3Al-Nb intermetallic disks sliding against alumina-boria-silicate fabric were ascertained in air at temperatures from 25 to 700 C. These materials are candidates for sliding seal applications for the National AeroSpace Plane. The tests were done using a pin on disk tribometer. Sliding was unidirectional at 0.27 m/sec under a nominal contact stress of 340 kPa. Gold sputter or ion plating deposited films were used to reduce friction and wear. Rhodium and palladium films were used beneath the gold lubricating films to prevent diffusion of the substrate into the gold at high temperature. The friction and wear of the unlubricated specimens was unacceptable. Friction coefficients were generally greater than 1.0. The ion plated gold films, when used with a rhodium diffusion barrier reduced friction by almost a factor of 2. Wear was also substantially reduced. The sputter deposited films were not adherent unless the substrate was sputter cleaned immediately prior to film deposition. Palladium did not function as a diffusion barrier.
NASA Technical Reports Server (NTRS)
Dellacorte, Christopher; Steinetz, Bruce M.; Brindley, Pamela K.
1989-01-01
Tribological properties of Ti3Al-Nb intermetallic disks sliding against alumina-boria-silicate fabric were ascertained in air at temperatures from 25 to 700 C. These materials are candidates for sliding seal applications for the National AeroSpace Plane. The tests were done using a pin on disk tribometer. Sliding was unidirectional at 0.27 m/sec under a nominal contact stress of 340 kPa. Gold sputter or ion plating deposited films were used to reduce friction and wear. Rhodium and palladium films were used beneath the gold lubricating films to prevent diffusion of the substrate into the gold at high temperature. The friction and wear of the unlubricated specimens was unacceptable. Friction coefficients were generally greater than 1.0. The ion plated gold films, when used with a rhodium diffusion barrier reduced friction by almost a factor of 2. Wear was also substantially reduced. The sputter deposited films were not adherent unless the substrate was sputter cleaned immediately prior to film deposition. Palladium did not function as a diffusion barrier.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Fernandez, M.J.; Bailey, P.M.; Bentz, P.O.
1984-09-19
Reaction of (C/sub 5/ qentamethyl Rh)/sub 2/Cl/sub 4/) (1) with triethylsilane leads to the novel rhodium(V) complex (eta/sup 5/-C/sub 5/Me/sub 5/Rh(H)/sub 2/(SiE-triethyl/sub 3/)/sub 2/) (2) characterized by NMR spectra (/sup 1/H, /sup 13/C, /sup 29/Si, and /sup 103/Rh), X-ray diffraction, and neutron diffraction at 20 K. The complex shows a four-legged piano stool geometry with the pentamethylcyclopentadienyl eta/sub 5/-bonded to the rhodium (average Rh-C, 2.283 (9) A) on top and the two triethylsilyl ligands trans in the basal plane (Rh-Si, 2.379 (2) A). The neutron diffraction analysis located the two hydrides, which are trans to each other and cis tomore » the triethylsilyls in the basal plane. The mean Rh-H distance is 1.581 (3) A, and the H-Rh-H angle is 94.8 (2)/sup 0/. Complex 2 is rather stable, but it reacts under forcing conditions with neutral ligands (triphenylphosphine, CO, or maleic anhydride) to give (C/sub 5/Me/sub 5/Rh(PPh/sub 3/)H(SiEt/sub 3/)), (C/sub 5/Me/sub 5/Rh(CO)/sub 2/), or (C/sub 5/M3/5Rh(maleic anhydride)/sup 2/). It reacts more easily with electrophiles such as HBF/sub 4/ to give (C/sub 5/Me/sub 5/Rh)/sub 4/H/sub 4/)/sup 2 +/, with HCl to give 1, with AgBF/sub 4/ in MeCN to give (C/sub 5/Me/sub 5/Rh(MeCN)/sub 3/)/sup 2 +/, and with I/sub 2/ to give ((C/sub 5/Me/sub 5/Rh)/sub 2/I/sub 4/). The predominant mode of reaction involves reductive elimination of Et/sub 3/Si-H, which can be strongly promoted by an electrophile. 43 references, 3 figures, 3 tables.« less
Chen, Mingyang; Serna, Pedro; Lu, Jing; ...
2015-09-28
The chemistry of zeolite-supported site-isolated cobalt, rhodium, and iridium complexes that are essentially molecular was investigated with density functional theory (DFT) and the results compared with experimentally determined spectra characterizing rhodium and iridium species formed by the reactions of Rh(C 2H 4) 2(acac) and Ir(C 2H 4) 2(acac) (acac = acetylacetonate) with acidic zeolites such as dealuminated HY zeolite. The experimental results characterize ligand exchange reactions and catalytic reactions of adsorbed ligands, including olefin hydrogenation and dimerization. Two molecular models were used to characterize various binding sites of the metal complexes in the zeolites, and the agreement between experimental andmore » calculated infrared frequencies and metal-ligand distances determined by extended X-ray absorption fine structure spectroscopy was generally very good. The calculated structures and energies indicate a metal-support-oxygen (M(I)-O) coordination number of two for most of the supported complexes and a value of three when the ligands include the radicals C 2H 5 or H. The results characterizing various isomers of the supported metal complexes incorporating hydrocarbon ligands indicate that some carbene and carbyne ligands could form. Ligand bond dissociation energies (LDEs) are reported to explain the observed reactivity trends. The experimental observations of a stronger M-CO bond than M-(C 2H 4) bond for both Ir and Rh match the calculated LDEs, which show that the single-ligand LDEs of the mono and dual-ligand complexes for CO are similar to 12 and similar to 15 kcal/mol higher in energy (when the metal is Rh) and similar to 17 and similar to 20 kcal/mol higher (when the metal is Ir) than the single-ligand LDEs of the mono and dual ligand complexes for C 2H 4, respectively. The results provide a foundation for the prediction of the catalytic properties of numerous supported metal complexes, as summarized in detail here.« less
Choleva, Tatiana G; Gatselou, Vasiliki A; Tsogas, George Z; Giokas, Dimosthenis L
2017-12-05
The intrinsic peroxidase-like activity of rhodium nanoparticles (RhNPs) and their use as catalytic labels for sensitive colorimetric assays is presented. RhNPs catalyze the oxidation of the peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H 2 O 2 to produce a blue reaction product with a maximum absorbance at 652 nm. Kinetic studies show catalysis to follow Michaelis-Menten kinetics and a "ping-pong" mechanism. The calculated kinetic parameters indicate high affinity of RhNPs for both the substrate TMB and H 2 O 2 . In fact, they are better than other peroxidase mimicking nanomaterials and even the natural enzyme horseradish peroxidase. On the other hand, RhNPs exhibit no reactivity towards saccharides, thiols, amino acids and ascorbic acid. Based on these findings, a sensitive and selective colorimetric method was worked out for the determination of H 2 O 2 in real samples with a linear response in the 1-100 μM concentration range. By employing glucose oxidase, the glucose assay has a linear range that covers the 5 to 125 μM glucose concentration range. The detection limits are <0.75 μM for both species. The methods were applied to the determination of H 2 O 2 in spiked pharmaceutical formulations, and of glucose in soft drinks and blood plasma. Figures of merit include (a) good accuracy (with errors of <6%), (b) high recoveries (96.5-103.7%), and (c) satisfactory reproducibility (<6.3%). Graphical abstract Rhodium nanoparticles catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H 2 O 2 to produce a blue reaction product. The effect is exploited in photometric assays for hydrogen peroxide and glucose.
Tan, Yuqi; Yuan, Wei; Gong, Lei; Meggers, Eric
2015-10-26
A sustainable C-C bond formation is merged with the catalytic asymmetric generation of one or two stereocenters. The introduced catalytic asymmetric cross-coupling of two C(sp3)-H groups with molecular oxygen as the oxidant profits from the oxidative robustness of a chiral-at-metal rhodium(III) catalyst and exploits an autoxidation mechanism or visible-light photosensitized oxidation. In the latter case, the catalyst serves a dual function, namely as a chiral Lewis acid for catalyzing enantioselective enolate chemistry and at the same time as a visible-light-driven photoredox catalyst. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Zhong, Hai-Jing; Wang, Wanhe; Kang, Tian-Shu; Yan, Hui; Yang, Yali; Xu, Lipeng; Wang, Yuqiang; Ma, Dik-Lung; Leung, Chung-Hang
2017-01-12
We report herein the identification of the rhodium(III) complex [Rh(phq) 2 (MOPIP)] + (1) as a potent and selective ATP-competitive neural precursor cell expressed, developmentally down-regulated 8 (NEDD8)-activating enzyme (NAE) inhibitor. Structure-activity relationship analysis indicated that the overall organometallic design of complex 1 was important for anti-inflammatory activity. Complex 1 showed promising anti-inflammatory activity in vivo for the potential treatment of inflammatory bowel disease.
Soil-like deposits observed by Sojourner, the Pathfinder rover
Moore, Henry J.; Bickler, Donald B.; Crisp, Joy A.; Eisen, Howard J.; Gensler, Jeffrey A.; Haldemann, Albert F.C.; Matijevic, Jacob R.; Reid, Lisa K.; Pavlics, Ferenc
1999-01-01
Most of the soil-like materials at the Pathfinder landing site behave like moderately dense soils on Earth with friction angles near 34°-39° and are called cloddy deposits. Cloddy deposits appear to be poorly sorted with dust-sized to granule-sized mineral or rock grains; they may contain pebbles, small rock fragments, and clods. Thin deposits of porous, compressible drifts with friction angles near 26°-28° are also present. Drifts are fine grained. Cohesions of both types of deposits are small. There may be indurated soil-like deposits and/or coated or crusted rocks. Cloddy deposits may be fluvial sediments of the Ares-Tiu floods, but other origins, such as ejecta from nearby impact craters, should be considered. Drifts are probably dusts that settled from the Martian atmosphere. Remote-sensing signatures of the deposits inferred from rover observations are consistent with those observed from orbit and Earth.
Formation of thin-film resistors on silicon substrates
Schnable, George L.; Wu, Chung P.
1988-11-01
The formation of thin-film resistors by the ion implantation of a metallic conductive layer in the surface of a layer of phosphosilicate glass or borophosphosilicate glass which is deposited on a silicon substrate. The metallic conductive layer materials comprise one of the group consisting of tantalum, ruthenium, rhodium, platinum and chromium silicide. The resistor is formed and annealed prior to deposition of metal, e.g. aluminum, on the substrate.
Bailis, Julie M; Weidmann, Alyson G; Mariano, Natalie F; Barton, Jacqueline K
2017-07-03
The DNA mismatch repair (MMR) pathway recognizes and repairs errors in base pairing and acts to maintain genome stability. Cancers that have lost MMR function are common and comprise an important clinical subtype that is resistant to many standard of care chemotherapeutics such as cisplatin. We have identified a family of rhodium metalloinsertors that bind DNA mismatches with high specificity and are preferentially cytotoxic to MMR-deficient cells. Here, we characterize the cellular mechanism of action of the most potent and selective complex in this family, [Rh(chrysi)(phen)(PPO)] 2+ (Rh-PPO). We find that Rh-PPO binding induces a lesion that triggers the DNA damage response (DDR). DDR activation results in cell-cycle blockade and inhibition of DNA replication and transcription. Significantly, the lesion induced by Rh-PPO is not repaired in MMR-deficient cells, resulting in selective cytotoxicity. The Rh-PPO mechanism is reminiscent of DNA repair enzymes that displace mismatched bases, and is differentiated from other DNA-targeted chemotherapeutics such as cisplatin by its potency, cellular mechanism, and selectivity for MMR-deficient cells.
NASA Astrophysics Data System (ADS)
Larmola, Tuula; Kiheri, Heikki; Bubier, Jill L.; van Dijk, Netty; Dise, Nancy; Fritze, Hannu; Hobbie, Erik A.; Juutinen, Sari; Laiho, Raija; Moore, Tim R.; Pennanen, Taina
2017-04-01
Peatlands store one third of the global soil carbon (C) pool. Long-term fertilization experiments in nutrient-poor peatlands showed that simulated atmospheric nitrogen (N) deposition does not enhance ecosystem C uptake but reduces C sink potential. Recent studies have shown that a significant proportion of C input to soil in low-fertility forests entered the soil through mycorrhizal fungi, rather than as plant litter. Is atmospheric N deposition diminishing peatland C sink potential due to the suppression of ericoid mycorrhizal fungi? We studied how nutrient addition influences plant biomass allocation and the extent to which plants rely on mycorrhizal N uptake at two of the longest-running nutrient addition experiments on peatlands, Whim Bog, United Kingdom, and Mer Bleue Bog, Canada. We determined the peak growing season aboveground biomass production and coverage of vascular plants using the point intercept method. We also analyzed isotopic δ15N patterns and nutrient contents in leaves of dominant ericoid mycorrhizal shrubs as well as the non-mycorrhizal sedge Eriophorum vaginatum under different nutrient addition treatments. The treatments receive an additional load of 1.6-6.4 N g m-2 y-1 either as ammonium (NH4) nitrate (NO3) or NH4NO3 and with or without phosphorus (P) and potassium (K), alongside unfertilized controls. After 11-16 years of nutrient addition, the vegetation structure had changed remarkably. Ten of the eleven nutrient addition treatments showed an increase of up to 60% in total vascular plant abundance. Only three (NH4Cl, NH4ClPK, NaNO3PK) of the nutrient addition treatments showed a concurrent decrease of down to 50% in the relative proportion of ericoid mycorrhizal shrubs to total vascular plant abundance. The response to nutrient load may be explained by the water table depth, the form of N added and whether N was added with PK. Shrubs were strong competitors at the dry Mer Bleue bog while sedges gained in abundance at the wetter Whim bog
Pierre, Valérie C.; Kaiser, Jens T.; Barton, Jacqueline K.
2007-01-01
We report the 1.1-Å resolution crystal structure of a bulky rhodium complex bound to two different DNA sites, mismatched and matched in the oligonucleotide 5′-(dCGGAAATTCCCG)2-3′. At the AC mismatch site, the structure reveals ligand insertion from the minor groove with ejection of both mismatched bases and elucidates how destabilized mispairs in DNA may be recognized. This unique binding mode contrasts with major groove intercalation, observed at a matched site, where doubling of the base pair rise accommodates stacking of the intercalator. Mass spectral analysis reveals different photocleavage products associated with the two binding modes in the crystal, with only products characteristic of mismatch binding in solution. This structure, illustrating two clearly distinct binding modes for a molecule with DNA, provides a rationale for the interrogation and detection of mismatches. PMID:17194756
de Carvalho, Renato L; Jardim, Guilherme A M; Santos, Augusto; Araujo, Maria H; Oliveira, Willian X C; Bombaça, Ana Cristina; Menna-Barreto, Rubem F S; Gopi, Elumalai; Gravel, Edmond; Doris, Eric; da Silva Júnior, Eufrânio Nunes
2018-06-14
We report a combination of aryl diselenides/hydrogen peroxide and carbon nanotube-rhodium nanohybrid for naphthols oxidation towards synthesis of 1,4-naphthoquinones and evaluation of their relevant trypanocidal activity. Under a combination of (PhSe)2/H2O2 in the presence of O2 in i-PrOH/Hexane, several benzenoid (A-ring) substituted quinones were prepared in moderate to high yields. We also studied the contribution of RhCNT as co-catalyst in this process and, in some cases, yields were improved. This method provides an efficient and versatile alternative for preparing A-ring modified naphthoquinonoid compounds with relevant biological profile. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
The effects of rhodium on the renal function of female Wistar rats.
Iavicoli, Ivo; Leso, Veruscka; Fontana, Luca; Marinaccio, Alessandro; Bergamaschi, Antonio; Calabrese, Edward J
2014-06-01
In recent years, the increased use of rhodium (Rh) as an active catalyst material in modern three-way automobile catalytic converters has led to a parallel rise in environmental levels of this metal. In spite of this, the literature contains few studies of the effects of Rh on human health. The aim of this study is to assess the effects of Rh on the renal function of female Wistar rats. Our findings show that sub-acute exposure to six increasing concentrations, ranging from 0.001 to 1 mg L(-1), of Rh (III) chloride hydrate in drinking water does not induce alterations in urinary albumin levels, while, at concentrations from 0.1 to 1 mg L(-1), a significant rise in urinary levels of Retinol Binding Protein is evident and an increasing trend in urinary β2-microglobulin, which becomes significant at 1 mg L(-1), is observed. These results therefore demonstrate a nephrotoxic action of Rh at tubular level in a wide range of doses. Interestingly, because of the recent increase in environmental Rh levels, these findings may have relevant implications both for occupationally exposed subjects and for the general population, especially children. Copyright © 2013 Elsevier Ltd. All rights reserved.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Chen, F.; Shao, K.-J.; Xiao, Y.-C.
2015-12-15
The rhodium(I) cyclooctadiene complex with the bis(3-tert-butylimidazol-2-ylidene)borate ligand [H{sub 2}B(Im{sup t}Bu){sup 2}]Rh(COD) C{sup 22}H{sup 36}BN{sup 4}Rh, has been prepared, and its crystal structure is determined by X-ray diffraction. Complex exhibits slightly distorted square planar configurations around the metal center, which is coordinated by the bidentate H{sup 2}B(Im{sup t}Bu){sub 2} and one cyclooctadiene group. The Rh–C{sub carbene} bond lengths are 2.043(4) and 2.074(4) Å, and the bond angle C–Rh1–C is 82.59°. The dihedral angle between two imidazol-2-ylidene rings is 67.30°.
Depositional processes in large-scale debris-flow experiments
Major, J.J.
1997-01-01
This study examines the depositional process and characteristics of deposits of large-scale experimental debris flows (to 15 m3) composed of mixtures of gravel (to 32 mm), sand, and mud. The experiments were performed using a 95-m-long, 2-m-wide debris-flow flume that slopes 31??. Following release, experimental debris flows invariably developed numerous shallow (???10 cm deep) surges. Sediment transported by surges accumulated abruptly on a 3?? runout slope at the mouth of the flume. Deposits developed in a complex manner through a combination of shoving forward and shouldering aside previously deposited debris and through progressive vertical accretion. Progressive accretion by the experimental flows is contrary to commonly assumed en masse sedimentation by debris flows. Despite progressive sediment emplacement, deposits were composed of unstratified accumulations of generally unsorted debris; hence massively textured, poorly sorted debris-flow deposits are not emplaced uniquely en masse. The depositional process was recorded mainly by deposit morphology and surface texture and was not faithfully registered by interior sedimentary texture; homogeneous internal textures could be misinterpreted as the result of en masse emplacement by a single surge. Deposition of sediment by similar, yet separate, debris flows produced a homogenous, massively textured composite deposit having little stratigraphic distinction. Similar deposit characteristics and textures are observed in natural debris-flow deposits. Experimental production of massively textured deposits by progressive sediment accretion limits interpretations that can be drawn from deposit characteristics and casts doubt on methods of estimating flow properties from deposit thickness or from relations between particle size and bed thickness.
Hansley, P.L.; Spirakis, C.S.
1992-01-01
Interstitial, epigenetic amorphous organic matter is intimately associated with uranium in the Grants uranium region and is considered essential to genetic models for these deposits. In contrast, uranium minerals are intimately associated with authigenic vanadium chlorite and vanadium oxides in amorphous organic matter-poor ores of the Slick Rock and Henry Mountains mining districts and therefore, in some genetic models amorphous organic matter is not considered crucial to the formation of these deposits. Differences in organic matter content can be explained by recognizing that amorphous organic matter-poor deposits have been subjected to more advanced stages of diagenesis than amorphous organic matter-rich deposits. Evidence that amorphous organic matter was involved in the genesis of organic matter-poor, as well as organic matter-rich, deposits is described. -from Authors
Wet Dust Deposition Across Texas, USA
NASA Astrophysics Data System (ADS)
Collins, J. D., Jr.; Ponette-González, A.; Gill, T. E.; Glass, G. A.; Weathers, K. C.
2016-12-01
Atmospheric dust deposition is of critical importance in terrestrial biogeochemical cycles, supplying essential limiting nutrients, such as calcium and phosphorus as well as pollutants, such as lead, to ecosystems. Dust particles are delivered to terrestrial ecosystems directly as dry deposition or in precipitation (wet deposition) as a result of rainout (particles incorporated into cloud droplets) and washout (particles that collide with raindrops as they fall). Compared to dry deposition, wet dust deposition (dissolved + particulate) is a poorly understood yet potentially significant pathway for dust input, especially in humid regions. We quantified wet dust deposition to two National Atmospheric Deposition Monitoring (NADP) sites across Texas-one in west (Guadalupe Mountains) and one in east (near Houston) Texas-with contrasting climate/dust regimes and land cover. We focused on 2012 during one of the most severe droughts in Texas since 1895. Dust event days (DEDs) were identified using meteorological data for stations within 150 km of the NADP sites where wet deposition was sampled weekly. DEDs were defined using the following criteria: visibility <10 km, <30% relative humidity, and wind speed >50 km, supplemented with other Saharan dust incursion and dust observations. A total of 34 DEDs (20 sample weeks) were identified for the west and 5 DEDs (4 sample weeks) for the east Texas sites. Bulk elemental composition of washout particles is analyzed using Particle Induced X-ray Emission (PIXE) spectroscopy and X-ray Fluorescence (XRF) spectroscopy. Using these data, we will examine differences in the chemical composition of rainwater and aerosol particles filtered from rain samples for dust versus non-dust event days at each study site. Deposition fluxes for dust and non-dust event weeks are also compared. Quantifying the magnitude of wet dust deposition is necessary to improve evaluation of dust impacts on biogeochemical cycles.
Weidmann, Alyson G; Barton, Jacqueline K
2015-10-05
We report the synthesis and characterization of a bimetallic complex derived from a new family of potent and selective metalloinsertors containing an unusual Rh-O axial coordination. This complex incorporates a monofunctional platinum center containing only one labile site for coordination to DNA, rather than two, and coordinates DNA nonclassically through adduct formation in the minor groove. This conjugate displays bifunctional, interdependent binding of mismatched DNA via metalloinsertion at a mismatch as well as covalent platinum binding. DNA sequencing experiments revealed that the preferred site of platinum coordination is not the traditional N7-guanine site in the major groove, but rather N3-adenine in the minor groove. The complex also displays enhanced cytotoxicity in mismatch repair-deficient and mismatch repair-proficient human colorectal carcinoma cell lines compared to the chemotherapeutic cisplatin, and it triggers cell death via an apoptotic pathway, rather than the necrotic pathway induced by rhodium metalloinsertors.
Mineral resource of the month: Chromium
Schulte, Ruth
2018-01-01
Although chromium is a metal, it does not occur naturally in metallic form. Chromium can be found in many minerals, but the only economically significant chromium-bearing mineral is chromite. Chromite has been mined from four different deposit types: stratiform chromite, podiform chromite, placer chromite, and laterite deposits. Most of the world's resources, however, are located in stratiform chromite deposits, such as the Bushveld Complex in South Africa. The economic potential of chromite resources depends on the thickness and continuity of the deposit and on the grade of the ore. Many of the major stratiform chromite deposits also contain economic levels of platinum, paladium, rhodium, osmium, iridium, and ruthenium.
Methods for making deposited films with improved microstructures
Patten, James W.; Moss, Ronald W.; McClanahan, Edwin D.
1982-01-01
Methods for improving microstructures of line-of-sight deposited films are described. Columnar growth defects ordinarily produced by geometrical shadowing during deposition of such films are eliminated without resorting to post-deposition thermal or mechanical treatments. The native, as-deposited coating qualities, including homogeneity, fine grain size, and high coating-to-substrate adherence, can thus be retained. The preferred method includes the steps of emitting material from a source toward a substrate to deposit a coating non-uniformly on the substrate surface, removing a portion of the coating uniformly over the surface, again depositing material onto the surface, but from a different direction, and repeating the foregoing steps. The quality of line-of-sight deposited films such as those produced by sputtering, progressively deteriorates as the angle of incidence between the flux and the surface becomes increasingly acute. Depositing non-uniformly, so that the coating becomes progressively thinner as quality deteriorates, followed by uniformly removing some of the coating, such as by resputtering, eliminates the poor quality portions, leaving only high quality portions of the coating. Subsequently sputtering from a different direction applies a high quality coating to other regions of the surface. Such steps can be performed either simultaneously or sequentially to apply coatings of a uniformly high quality, closed microstructure to three-dimensional or larger planar surfaces.
Schulz, Klaus J.; Chandler, Val W.; Nicholson, Suzanne W.; Piatak, Nadine M.; Seal, Robert R.; Woodruff, Laurel G.; Zientek, Michael L.
2010-01-01
Magmatic sulfide deposits containing nickel (Ni) and copper (Cu), with or without (?) platinum-group elements (PGEs), account for approximately 60 percent of the world's Ni production and are active exploration targets in the United States and elsewhere. On the basis of their principal metal production, magmatic sulfide deposits in mafic rocks can be divided into two major types: those that are sulfide-rich, typically with 10 to 90 percent sulfide minerals, and have economic value primarily because of their Ni and Cu contents; and those that are sulfide-poor, typically with 0.5 to 5 percent sulfide minerals, and are exploited principally for PGE. Because the purpose of this deposit model is to facilitate the assessment for undiscovered, potentially economic magmatic Ni-Cu?PGE sulfide deposits in the United States, it addresses only those deposits of economic significance that are likely to occur in the United States on the basis of known geology. Thus, this model focuses on deposits hosted by small- to medium-sized mafic and (or) ultramafic dikes and sills that are related to picrite and tholeiitic basalt magmatic systems generally emplaced in continental settings as a component of large igneous provinces (LIPs). World-class examples (those containing greater than 1 million tons Ni) of this deposit type include deposits at Noril'sk-Talnakh (Russia), Jinchuan (China), Pechenga (Russia), Voisey's Bay (Canada), and Kabanga (Tanzania). In the United States, this deposit type is represented by the Eagle deposit in northern Michigan, currently under development by Kennecott Minerals.
Marsh, Erin; Anderson, Eric J.; Gray, Floyd
2013-01-01
Nickel-cobalt (Ni-Co) laterite deposits are supergene enrichments of Ni±Co that form from intense chemical and mechanical weathering of ultramafic parent rocks. These regolith deposits typically form within 26 degrees of the equator, although there are a few exceptions. They form in active continental margins and stable cratonic settings. It takes as little as one million years for a laterite profile to develop. Three subtypes of Ni-Co laterite deposits are classified according to the dominant Ni-bearing mineralogy, which include hydrous magnesium (Mg)-silicate, smectite, and oxide. These minerals form in weathering horizons that begin with the unweathered protolith at the base, saprolite next, a smectite transition zone only in profiles where drainage is very poor, followed by limonite, and then capped with ferricrete at the top. The saprolite contains Ni-rich hydrous Mg-silicates, the Ni-rich clays occur in the transition horizon, and Ni-rich goethite occurs in the limonite. Although these subtypes of deposits are the more widely used terms for classification of Ni-Co laterite deposits, most deposits have economic concentrations of Ni in more than one horizon. Because of their complex mineralogy and heterogeneous concentrations, mining of these metallurgically complex deposits can be challenging. Deposits range in size from 2.5 to about 400 million tonnes, with Ni and Co grades of 0.66–2.4 percent (median 1.3) and 0.01–0.15 percent (median 0.08), respectively. Modern techniques of ore delineation and mineralogical identification are being developed to aid in streamlining the Ni-Co laterite mining process, and low-temperature and low-pressure ore processing techniques are being tested that will treat the entire weathered profile. There is evidence that the production of Ni and Co from laterites is more energy intensive than that of sulfide ores, reflecting the environmental impact of producing a Ni-Co laterite deposit. Tailings may include high levels of
NASA Astrophysics Data System (ADS)
Mueller, W. U.; Dingwell, D. B.; Downey, W. S.; Mastin, L. G.
2008-12-01
Recognizing pyroclastic deposits that originate directly from magmatic and phreatomagmatic explosions in a subaqueous setting is based upon sedimentary structures, such as massive, stratified, and graded beds as well as (pyro)clast size. Ideally such deposits form ordered fining-and thinning-upward sequences. Pumice, scoria, glass shards, euhedral and broken crystals, and lithic fragments are constituents that support an explosive heritage. Recent deep-sea ROV and submersible dives have retrieved non-vesicular to vesicle- poor, mm-scale, mafic shards in 5-15 cm-thick massive and/or graded (stratified) deposits, for which a subaqueous explosive origin has been inferred. These sheet hyaloclastites with variable shard shapes were first documented on Seamount 6 as deep-sea Limu O Pele at water depths > 1000 m. We identified in Seamount 6 samples equant to blocky shards with angular to subrounded terminations, but also subordinate hair-like and contorted glassy filaments, warped shards and irregular shards. Shards display internal laminations (flow-banding?) and have local perlitic fractures. Bubble wall shards derived from scoria burst were rare. In combination with all the above and a poor shard vesicularity (< 2%), a magmatic explosive origin seems improbable. Such small-volume deposits have been reported from seamounts and summit calderas associated with subaqueous drainage tubes and ponded magma in depths > 1000 m. We envision that hydrostatic pressure commensurate with water depth played a significant role. The deposits can be readily explained by a hydroclastic process whereby fragmentation occurred at the milli-second (Limu) to second scale (hyaloclastite). Hence, hyperquenched glass shards or thread-like glass filaments need not require magmatic explosivity. Constant surface interaction between aphyric, low-viscosity, high temperature, magma-lava at depth with seawater causes fragmentation (granulation) that can generate such delicate shards. The transfer of
Weidmann, Alyson G.; Barton, Jacqueline K.
2015-01-01
We report the synthesis and characterization of a bimetallic complex derived from a new family of potent and selective metalloinsertors containing an unusual Rh—O axial coordination. This complex incorporates a monofunctional platinum center containing only one labile site for coordination to DNA, rather than two, and coordinates DNA non-classically through adduct formation in the minor groove. This conjugate displays bifunctional, interdependent binding of mismatched DNA via metalloinsertion at a mismatch as well as covalent platinum binding. DNA sequencing experiments revealed that the preferred site of platinum coordination is not the traditional N7-guanine site in the major groove, but rather N3-adenine in the minor groove. The complex also displays enhanced cytotoxicity in mismatch repair-deficient and mismatch repair-proficient human colorectal carcinoma cell lines compared to the chemotherapeutic cisplatin, and triggers cell death via an apoptotic pathway, rather than the necrotic pathway induced by rhodium metalloinsertors. PMID:26397309
NASA Astrophysics Data System (ADS)
Jochum, K. P.; Seufert, H. M.
1995-09-01
We have developed new spark source mass spectrometric (SSMS) techniques for simultaneous analysis of platinum-group elements (PGE) together with other trace elements in stony meteorites. We have measured elemental abundances of Rh, Ru, Os, Ir, Pt, Au in carbonaceous chondrites of different types including the two CI chondrites Orgueil and Ivuna. These data are relevant for the determination of solar-system abundances. Whereas the solar-system abundances of most PGE are well known, this is not the case for Rh, and no literature data exist for carbonaceous chondrites, mainly because of analytical difficulties. The SSMS techniques include new calibration procedures and the use of a recently developed multi-ion counting (MIC) system [1]. The mono-isotopic element Rh and the other PGE were determined by using internal standard elements (e.g., Nd, U) that were measured by isotope dilution in the same sample electrode material. The data were calibrated with certified standard solutions of PGE which were doped on trace-element poor rock samples. Ion abundances were measured using both the conventional photoplate detection and the ion-counting techniques. The new MIC technique that uses up to 20 small channeltrons for ion counting measurements has the advantage of improved precision, detection limits and analysis time compared to photoplate detection. Tab. 1 shows the Rh analyses for the meteorites Orgueil, Ivuna, Murchison, Allende and Karoonda obtained by conventional photoplate detection. These are the first Rh results for carbonaceous chondrites. The data for the two CI chondrites Orgueil and Ivuna are identical and agree within 4 % with the CI estimate of Anders and Grevesse [2] which was derived indirectly from analyses for H-chondrites. The PGE Os, Ir, Pt, Au and W, Re, Th, U concentrations were determined by both detection systems. Data obtained with the MIC system are more precise (about 4% for concentrations in the ppb range) compared to the photoplate detection
NASA Astrophysics Data System (ADS)
Kashi, N. N.; Wieder, R.; Vile, M. A.
2013-12-01
Emissions of NOx associated with Alberta oil sands (AOS) development are leading to locally elevated atmospheric N deposition, in a region where background N deposition has been historically quite low (< 1 kg/ha/yr). This elevated N deposition has the potential to alter the ecosystem structure and function of nutrient-poor boreal peatlands. Nitrogen enrichment may alter soil microbial activity, which could be manifested in changes in extracellular enzyme activities. Since 2011, we have been experimentally adding N as NH4NO3 in simulated precipitation at 0, 5, 10, 15, 20, and 25 kg N ha/yr/ plus no-water controls to a boreal bog and a poor fen (3 replicate plots per treatment). In 2013, acid phosphatase activities in living plant capitulum of Sphagnum angustifolium, Sphagnum fuscum, and Sphagnum magellanicum were quantified in June and July using 4-methyumbelliferylphosphate and fluorescence detection of the enzymatically released methylumbelliferone (MUF). Phosphatase activities did not differ with N treatment for S. angustifolium in the bog (p=0.3409) or the poor fen (p=0.0629), or for S. fuscum in the bog (p=0.1950), averaging 35.0 × 0.7, 61.6 × 1.2, and 41.6 × 0.9 μmol MUF/g DWT/hr, respectively. For S. fuscum in the poor fen, phosphatase activities differed between N treatments (p=0.0275), ranging 40.6 × 1.1 μmol MUF/g DWT/hr in the control plots to 73.7 × 2.0 μmol MUF/g DWT/hr in the 5 kg/ha/yr N treatment plots; increasing N deposition did not result in a gradual change in enzyme activity. On the other hand, S. magellanicum phosphatase activities differed between N treatments (p=0.0189) and showed a pattern of generally increasing activity with increasing N deposition (37.4 × 0.5 μmol MUF/g DWT/hr in control plots; 97.9 × 4.5 μmol MUF/g DWT/hr in the 25 kg/ha/yr N treatment plots). The differing phosphatase responses between these dominant Sphagnum species suggest unique differences in nutrient balance and/or microbial activity. Combining the
Iron deposition and inflammation in multiple sclerosis. Which one comes first?
2011-01-01
Whether iron deposition is an epiphenomenon of the multiple sclerosis (MS) disease process or may play a primary role in triggering inflammation and disease development remains unclear at this time, and should be studied at the early stages of disease pathogenesis. However, it is difficult to study the relationship between iron deposition and inflammation in early MS due to the delay between the onset of symptoms and diagnosis, and the poor availability of tissue specimens. In a recent article published in BMC Neuroscience, Williams et al. investigated the relationship between inflammation and iron deposition using an original animal model labeled as "cerebral experimental autoimmune encephalomyelitis", which develops CNS perivascular iron deposits. However, the relative contribution of iron deposition vs. inflammation in the pathogenesis and progression of MS remains unknown. Further studies should establish the association between inflammation, reduced blood flow, iron deposition, microglia activation and neurodegeneration. Creating a representative animal model that can study independently such relationship will be the key factor in this endeavor. PMID:21699686
Mineralogy and chemistry of massive sulfide deposits from the Juan de Fuca Ridge.
Koski, R.A.; Clague, D.A.; Oudin, E.
1984-01-01
Two types of massive sulphide were dredged from one of the six vent sites located in the axial valley of the southern Juan de Fuca ridge. Type A samples are angular slabs of dark grey Zn-rich sulphide with interlayers and a thin, partly-oxidized crust of Fe-sulphide. These layered sulphide aggregates appear to be fragments of a sulphide wall enclosing an active hydrothermal vent. The outer sulphide wall is composed of colloform Fe sulphide and Fe-poor sphalerite deposited under low-T conditions when sea-water and hydrothermal fluid mix above the discharge point. Inside the wall the intensifying hydrothermal sytem deposits a higher-T assemblage of granular Fe-rich sphalerite, wurtzite, pyrite and minor Cu-Fe sulphide. Type B sulphide samples are sub-rounded, spongy-textured fragments composed almost entirely of dendritic aggregates of pale Fe-poor colloform sphalerite and opaline silica. This type of sulphide is deposited in settings peripheral to sites of focused discharge and in open spaces by moderate- to low-T fluid discharging at a slow but variable rate; the fluid becomes increasingly oxidizing, resulting in late-stage deposits of hematite, baryte and sulphur.-L.di H.
Subretinal Drusenoid Deposits AKA Pseudodrusen.
Spaide, Richard F; Ooto, Sotaro; Curcio, Christine A
2018-05-30
A distinction between conventional drusen and pseudodrusen was first made in 1990, and more recently knowledge of pseudodrusen, more accurately called subretinal drusenoid deposits (SDD), has expanded. Pseudodrusen have a bluish-white appearance by biomicroscopy and color fundus photography. Using optical coherence tomography, pseudodrusen were found to be accumulations of material internal to the retinal pigment epithelium (RPE) that could extend internally through the ellipsoid zone. These deposits are more commonly seen in older eyes with thinner choroids. Histologic evaluation of these deposits revealed aggregations of material in the subretinal space between photoreceptors and RPE. SDD contain some proteins in common with soft drusen, but differ in lipid composition. Many studies reported that SDD are strong independent risk factors for late age-related macular degeneration (AMD). Geographic atrophy and Type 3 neovascularization are particularly associated with SDD. Unlike conventional drusen, eyes with SDD show slowed dark adaptation and poor contrast sensitivity. Eyes with regression of SDD develop outer retinal atrophy, which is a newly recognized form of late AMD. Advances in imaging technology have enabled many insights into this condition, including associated photoreceptor, RPE, and underlying choroidal changes. Copyright © 2018. Published by Elsevier Inc.
Empirical Determination of Dark Matter Velocities Using Metal-Poor Stars.
Herzog-Arbeitman, Jonah; Lisanti, Mariangela; Madau, Piero; Necib, Lina
2018-01-26
The Milky Way dark matter halo is formed from the accretion of smaller subhalos. These sub-units also harbor stars-typically old and metal-poor-that are deposited in the Galactic inner regions by disruption events. In this Letter, we show that the dark matter and metal-poor stars in the Solar neighborhood share similar kinematics due to their common origin. Using the high-resolution eris simulation, which traces the evolution of both the dark matter and baryons in a realistic Milky Way analog galaxy, we demonstrate that metal-poor stars are indeed effective tracers for the local, virialized dark matter velocity distribution. The local dark matter velocities can therefore be inferred from observations of the stellar halo made by the Sloan Digital Sky Survey within 4 kpc of the Sun. This empirical distribution differs from the standard halo model in important ways and suggests that the bounds on the spin-independent scattering cross section may be weakened for dark matter masses below ∼10 GeV. Data from Gaia will allow us to further refine the expected distribution for the smooth dark matter component, and to test for the presence of local substructure.
Thin Film Electrodes with an Integral Current Collection Grid for Use with Solid Electrolytes
NASA Technical Reports Server (NTRS)
Ryan, M. A.; Kisor, A.; Williams, R. M.; Jeffries-Nakamura, B.; O'Connor, D.
1994-01-01
Thin film, high performance electrodes which can operate in high temperature environments are necessary for many devices which use a solid electrolyte. Electrodes of rhodium-tungsten alloy have been deposited on solid electrolyte using photolytic chemical vapor deposition (PCVD). A technique for depositing electrodes and current collection grids simultaneously has been developed using the prenucleation characteristics of PCVD. This technique makes it possible to fabricate electrodes which allow vapor transport through the thin (<1 (micro)m) portions of the electrode while integral thick grid lines improve the electronic conductivity of the electrode, thus improving overall performance.
NASA Astrophysics Data System (ADS)
Ostapenko, N. S.; Neroda, O. N.
2016-05-01
The paper discusses factors in the deposition and concentration of native gold and the spatial distribution of its individuals within the sufide-poor gold-quartz veins at the mesoabyssal Tokur deposit. The major factors in deposition of gold were sealing of the hydrothermal system, a sudden drop in fluid pressure, and repeated immiscibility in the fluid. Native gold was deposited in relation to initial acts of prolonged and discrete opening and preopening of cavities in three mineral assemblages of the productive association II. Most native gold individuals with a visible size of 0.1-1.5 mm were together with the early generation of quartz 2 on cavity walls adjacent to altered rocks. This is caused by the high content of Au complexes in initial hydrothermal solutions favoring rapid oversaturation during cavity formation. Gold fills interstices between grains of quartz 2 throughout the deposit and mineral assemblages. The vertical-flow distribution of gold has been established in economic veins; the upper and middle levels are enriched in gold, and samples with the greatest gold grade of 100-500 g/t or higher are concentrated there. This is caused both by the predominance of mineral association II at these levels and probable natural flotation of gold grains contained in the gold-gas associate for immiscibility of the hydrothermal fluid at the second stage of the ore-forming process.
Pennington-Boggio, Megan K; Conley, Brian L; Richmond, Michael G; Williams, Travis J
2014-12-14
Rhodium(I) and Iridium(I) borate complexes of the structure [Me 2 B(2-py) 2 ]ML 2 (L 2 = (tBuNC) 2 , (CO) 2 , (C 2 H 4 ) 2 , cod, dppe) were prepared and structurally characterized (cod = 1,5-cyclooctadiene; dppe = 1,2-diphenylphosphinoethane). Each contains a boat-configured chelate ring that participates in a boat-to-boat ring flip. Computational evidence shows that the ring flip proceeds through a transition state that is near planarity about the chelate ring. We observe an empirical, quantitative correlation between the barrier of this ring flip and the π acceptor ability of the ancillary ligand groups on the metal. The ring flip barrier correlates weakly to the Tolman and Lever ligand parameterization schemes, apparently because these combine both σ and π effects while we propose that the ring flip barrier is dominated by π bonding. This observation is consistent with metal-ligand π interactions becoming temporarily available only in the near-planar transition state of the chelate ring flip and not the boat-configured ground state. Thus, this is a first-of-class observation of metal-ligand π bonding governing conformational dynamics.
Pennington-Boggio, Megan K.; Conley, Brian L.; Richmond, Michael G.; Williams, Travis J.
2014-01-01
Rhodium(I) and Iridium(I) borate complexes of the structure [Me2B(2-py)2]ML2 (L2 = (tBuNC)2, (CO)2, (C2H4)2, cod, dppe) were prepared and structurally characterized (cod = 1,5-cyclooctadiene; dppe = 1,2-diphenylphosphinoethane). Each contains a boat-configured chelate ring that participates in a boat-to-boat ring flip. Computational evidence shows that the ring flip proceeds through a transition state that is near planarity about the chelate ring. We observe an empirical, quantitative correlation between the barrier of this ring flip and the π acceptor ability of the ancillary ligand groups on the metal. The ring flip barrier correlates weakly to the Tolman and Lever ligand parameterization schemes, apparently because these combine both σ and π effects while we propose that the ring flip barrier is dominated by π bonding. This observation is consistent with metal-ligand π interactions becoming temporarily available only in the near-planar transition state of the chelate ring flip and not the boat-configured ground state. Thus, this is a first-of-class observation of metal-ligand π bonding governing conformational dynamics. PMID:25435645
NASA Technical Reports Server (NTRS)
Ahmed, Shaffiq; Germain, Edward F.; Daryabeigi, Kamran; Alderfer, David W.; Wright, Robert E.
1987-01-01
An iridium versus iridium-40% rhodium thermocouple was studied. Problems associated with the use of this thermocouple for high temperature applications (up to 2000 C) were investigated. The metallurgical studies included X-ray, macroscopic, resistance, and metallographic studies. The thermocouples in the as-received condition from the manufacturer revealed large amounts of internal stress caused by cold working during manufacturing. The thermocouples also contained a large amount of inhomogeneities and segregations. No phase transformations were observed in the alloy up to 1100 C. It was found that annealing the thermocouple at 1800 C for two hours, and then at 1400 C for 2 to 3 hours yielded a fine grain structure, relieving some of the strains, and making the wire more ductile. It was also found that the above annealing procedure stabilized the thermal emf behavior of the thermocouple for application below 1800 C (an improvement from + or - 1% to + or - 0.02% within the range of the test parameters used).
Murai, Masahito; Takeuchi, Yutaro; Yamauchi, Kanae; Kuninobu, Yoichiro; Takai, Kazuhiko
2016-04-18
Mechanistic insight into the construction of quaternary silicon chiral centers by rhodium-catalyzed synthesis of spiro-9-silabifluorenes through dehydrogenative silylation is reported. The C2 -symmetric bisphosphine ligand, BINAP, was effective in controlling enantioselectivity, and axially chiral spiro-9-silabifluorenes were obtained in excellent yields with high enantiomeric excess. Monitoring of the reaction revealed the presence of a monohydrosilane intermediate as a mixture of two constitutional isomers. The reaction proceeded through two consecutive dehydrogenative silylations, and the absolute configuration was determined in the first silylative cyclization. Competitive reactions with electron-rich and electron-deficient dihydrosilanes indicated that the rate of silylative cyclization increased with decreasing electron density on the silicon atom of the starting dihydrosilane. Further investigation disclosed a rare interconversion between the two constitutional isomers of the monohydrosilane intermediate with retention of the absolute configuration. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Dias, V M C; Cardoso, A S B
2006-05-01
Reference methods for determining lead in food are usually time-consuming. This paper reports a straightforward procedure using electrothermal atomic absorption spectrometry (ETAAS), to determine lead (Pb) in fat-free sweets. Several chemical modifiers were examined and results showed that it is not necessary to digest the samples, when a rhodium (Rh) modifier was used. The samples were dissolved in nitric acid and the determination of Pb was performed by ETAAS, using Rh chemical modifier at a pyrolysis temperature of 900 degrees C and an atomization temperature of 1,500 degrees C. No ashing step was employed and aqueous standards were used, in the range 2-10 microg l(-1). The limit of quantification was 0.095 mg kg(-1), and the accuracy of the method was verified by analysing certified reference materials.
Zhou, Ming-Bo; Pi, Rui; Hu, Ming; Yang, Yuan; Song, Ren-Jie; Xia, Yuanzhi; Li, Jin-Heng
2014-10-13
This study describes a new rhodium(III)-catalyzed [3+2] annulation of 5-aryl-2,3-dihydro-1H-pyrroles with internal alkynes using a Cu(OAc)2 oxidant for building a spirocyclic ring system, which includes the functionalization of an aryl C(sp(2))-H bond and addition/protonolysis of an alkene C=C bond. This method is applicable to a wide range of 5-aryl-2,3-dihydro-1H-pyrroles and internal alkynes, and results in the assembly of the spiro[indene-1,2'-pyrrolidine] architectures in good yields with excellent regioselectivities. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Poor Americans: How the Poor White Live.
ERIC Educational Resources Information Center
Pilisuk, Marc; Pilisuk, Phyllis
Contents of this book include the following essays which originally appeared in "Transaction" magazine: (1) "Poor Americans: an introduction," Marc Pilisuk and Phyllis Pilisuk; (2) "How the white poor live," Marc Pilisuk and Phyllis Pilisuk; (3) "The culture of poverty," Oscar Lewis; (4) "Life in Appalachia--the case of Hugh McCaslin," Robert…
NASA Astrophysics Data System (ADS)
Haas, Tjalling; Braat, Lisanne; Leuven, Jasper R. F. W.; Lokhorst, Ivar R.; Kleinhans, Maarten G.
2015-09-01
Predicting debris flow runout is of major importance for hazard mitigation. Apart from topography and volume, runout distance and area depends on debris flow composition and rheology, but how is poorly understood. We experimentally investigated effects of composition on debris flow runout, depositional mechanisms, and deposit geometry. The small-scale experimental debris flows were largely similar to natural debris flows in terms of flow behavior, deposit morphology, grain size sorting, channel width-depth ratio, and runout. Deposit geometry (lobe thickness and width) in our experimental debris flows is largely determined by composition, while the effects of initial conditions of topography (i.e., outflow plain slope and channel slope and width) and volume are negligible. We find a clear optimum in the relations of runout with coarse-material fraction and clay fraction. Increasing coarse-material concentration leads to larger runout. However, excess coarse material results in a large accumulation of coarse debris at the flow front and enhances diffusivity, increasing frontal friction and decreasing runout. Increasing clay content initially enhances runout, but too much clay leads to very viscous flows, reducing runout. Runout increases with channel slope and width, outflow plain slope, debris flow volume, and water fraction. These results imply that debris flow runout depends at least as much on composition as on topography. This study improves understanding of the effects of debris flow composition on runout and may aid future debris flow hazard assessments.
NASA Astrophysics Data System (ADS)
Berghuijs, Jaap F.; Mattsson, Hannes B.
2013-02-01
, sufficiently large to drive magmatic fragmentation. Both eruptions were pulsating in intensity and relatively short-lived, with estimated durations of 23 and 10 h for Loolmurwak and Eledoi, respectively. The depositional characteristics of these maars, including the abundant occurrence of mantle xenoliths in the deposits, as well as their envisaged mode of emplacement show a strong similarity to the often poorly preserved vent-facies of kimberlitic diatremes. Therefore, future research on well-preserved melilititic maar-diatreme deposits may provide valuable insights into kimberlite emplacement processes.
Factors associated with the deposition of Cladophora on Lake Michigan beaches in 2012
Riley, Stephen C.; Tucker, Taaja R.; Adams, Jean V.; Fogarty, Lisa R.; Lafrancois, Brenda Moraska
2015-01-01
Deposition of the macroalgae Cladophora spp. was monitored on 18 beaches around Lake Michigan during 2012 at a high temporal frequency. We observed a high degree of spatial variability in Cladophora deposition among beaches on Lake Michigan, even within local regions, with no clear regional pattern in the intensity of Cladophora deposition. A strong seasonal pattern in Cladophora deposition was observed, with the heaviest deposition occurring during mid-summer. Several beaches exhibited high temporal variability in Cladophora deposition over short time scales, suggesting that drifting algal mats may be extremely dynamic in nearshore environments of the Great Lakes. Cladophora deposition on Lake Michigan beaches was primarily related to the presence of nearshore structures, local population density, and nearshore bathymetry. There was relatively little evidence that waves, winds, or currents were associated with Cladophora deposition on beaches, but this may be due to the relatively poor resolution of existing nearshore hydrodynamic data. Developing a predictive understanding of beach-cast Cladophora dynamics in Great Lakes environments may require both intensive Cladophora monitoring and fine-scale local hydrodynamic modeling efforts.
Aerodynamics and deposition effects of inhaled submicron drug aerosol in airway diseases.
Faiyazuddin, Md; Mujahid, Md; Hussain, Talib; Siddiqui, Hefazat H; Bhatnagar, Aseem; Khar, Roop K; Ahmad, Farhan J
2013-01-01
Particle engineering is the prime focus to improve pulmonary drug targeting with the splendor of nanomedicines. In recent years, submicron particles have emerged as prettyful candidate for improved fludisation and deposition. For effective deposition, the particle size must be in the range of 0.5-5 μm. Inhalers design for the purpose of efficient delivery of powders to lungs is again a crucial task for pulmonary scientists. A huge number of DPI devices exist in the market, a significant number are awaiting FDA approval, some are under development and a large number have been patented or applied for patent. Even with superior design, the delivery competence is still deprived, mostly due to fluidisation problems which cause poor aerosol generation and deposition. Because of the cohesive nature and poor flow characteristics, they are difficult to redisperse upon aerosolization with breath. These problems are illustrious in aerosol research, much of which is vastly pertinent to pulmonary therapeutics. A technical review is presented here of advances that have been utilized in production of submicron drug particles, their in vitro/in vivo evaluations, aerosol effects and pulmonary fate of inhaled submicron powders.
Jardim, Guilherme A M; Silva, Thaissa L; Goulart, Marilia O F; de Simone, Carlos A; Barbosa, Juliana M C; Salomão, Kelly; de Castro, Solange L; Bower, John F; da Silva Júnior, Eufrânio N
2017-08-18
Thirty four halogen and selenium-containing quinones, synthesized by rhodium-catalyzed C-H bond activation and palladium-catalyzed cross-coupling reactions, were evaluated against bloodstream trypomastigotes of T. cruzi. We have identified fifteen compounds with IC 50 /24 h values of less than 2 μM. Electrochemical studies on A-ring functionalized naphthoquinones were also performed aiming to correlate redox properties with trypanocidal activity. For instance, (E)-5-styryl-1,4-naphthoquinone 59 and 5,8-diiodo-1,4-naphthoquinone 3, which are around fifty fold more active than the standard drug benznidazole, are potential derivatives for further investigation. These compounds represent powerful new agents useful in Chagas disease therapy. Copyright © 2017 Elsevier Masson SAS. All rights reserved.
Do Middle-Class Students Perceive Poor Women and Poor Men Differently?
ERIC Educational Resources Information Center
Cozzarelli, Catherine; Tagler, Michael J.; Wilkinson, Anna V.
2002-01-01
Examined college students' attitudes and stereotypes regarding poor women, attributions for their poverty, and whether those thoughts and feelings differed from those about poor men. Attitudes and stereotypes were significantly more positive regarding poor women than poor men. Participants endorsed internal attributions for both women's and men's…
A rhodium(III) complex for high-affinity DNA base-pair mismatch recognition
Junicke, Henrik; Hart, Jonathan R.; Kisko, Jennifer; Glebov, Oleg; Kirsch, Ilan R.; Barton, Jacqueline K.
2003-01-01
A rhodium(III) complex, rac-[Rh(bpy)2phzi]3+ (bpy, 2,2′-bipyridine; phzi, benzo[a]phenazine-5,6-quinone diimine) has been designed as a sterically demanding intercalator targeted to destabilized mismatched sites in double-helical DNA. The complex is readily synthesized by condensation of the phenazine quinone with the corresponding diammine complex. Upon photoactivation, the complex promotes direct strand scission at single-base mismatch sites within the DNA duplex. As with the parent mismatch-specific reagent, [Rh(bpy)2(chrysi)]3+ [chrysene-5,6-quinone diimine (chrysi)], mismatch selectivity depends on the helix destabilization associated with mispairing. Unlike the parent chrysi complex, the phzi analogue binds and cleaves with high affinity and efficiency. The specific binding constants for CA, CC, and CT mismatches within a 31-mer oligonucleotide duplex are 0.3, 1, and 6 × 107 M−1, respectively; site-specific photocleavage is evident at nanomolar concentrations. Moreover, the specificity, defined as the ratio in binding affinities for mispaired vs. well paired sites, is maintained. The increase in affinity is attributed to greater stability in the mismatched site associated with stacking by the heterocyclic aromatic ligand. The high-affinity complex is also applied in the differential cleavage of DNA obtained from cell lines deficient in mismatch repair vs. those proficient in mismatch repair. Agreement is found between photocleavage by the mismatch-specific probes and deficiency in mismatch repair. This mismatch-specific targeting, therefore, offers a potential strategy for new chemotherapeutic design. PMID:12610209
Longitudinal Stability and Predictors of Poor Oral Comprehenders and Poor Decoders
Elwér, Åsa; Keenan, Janice M.; Olson, Richard K.; Byrne, Brian; Samuelsson, Stefan
2012-01-01
Two groups of 4th grade children were selected from a population sample (N= 926) to either be Poor Oral Comprehenders (poor oral comprehension but normal word decoding), or Poor Decoders (poor decoding but normal oral comprehension). By examining both groups in the same study with varied cognitive and literacy predictors, and examining them both retrospectively and prospectively, we could assess how distinctive and stable the predictors of each deficit are. Predictors were assessed retrospectively at preschool, at the end of kindergarten, 1st, and 2nd grades. Group effects were significant at all test occasions, including those for preschool vocabulary (worse in poor oral comprehenders) and rapid naming (RAN) (worse in poor decoders). Preschool RAN and Vocabulary prospectively predicted grade 4 group membership (77–79% correct classification) within the selected samples. Reselection in preschool of at-risk poor decoder and poor oral comprehender subgroups based on these variables led to significant but relatively weak prediction of subtype membership at grade 4. Implications of the predictive stability of our results for identification and intervention of these important subgroups are discussed. PMID:23528975
Deposition and properties of cobalt- and ruthenium-based ultra-thin films
NASA Astrophysics Data System (ADS)
Henderson, Lucas Benjamin
Future copper interconnect systems will require replacement of the materials that currently comprise both the liner layer(s) and the capping layer. Ruthenium has previously been considered as a material that could function as a single material liner, however its poor ability to prevent copper diffusion makes it incompatible with liner requirements. A recently described chemical vapor deposition route to amorphous ruthenium-phosphorus alloy films could correct this problem by eliminating the grain boundaries found in pure ruthenium films. Bias-temperature stressing of capacitor structures using 5 nm ruthenium-phosphorus film as a barrier to copper diffusion and analysis of the times-to-failure at accelerated temperature and field conditions implies that ruthenium-phosphorus performs acceptably as a diffusion barrier for temperatures above 165°C. The future problems associated with the copper capping layer are primarily due to the poor adhesion between copper and the current Si-based capping layers. Cobalt, which adheres well to copper, has been widely proposed to replace the Si-based materials, but its ability to prevent copper diffusion must be improved if it is to be successfully implemented in the interconnect. Using a dual-source chemistry of dicobaltoctacarbonyl and trimethylphosphine at temperatures from 250-350°C, amorphous cobalt-phosphorus can be deposited by chemical vapor deposition. The films contain elemental cobalt and phosphorus, plus some carbon impurity, which is incorporated in the film as both graphitic and carbidic (bonded to cobalt) carbon. When deposited on copper, the adhesion between the two materials remains strong despite the presence of phosphorus and carbon at the interface, but the selectivity for growth on copper compared to silicon dioxide is poor and must be improved prior to consideration for application in interconnect systems. A single molecule precursor containing both cobalt and phosphorus atoms, tetrakis
Cheemalapati, Srikanth; Chen, Shen-Ming; Ali, M Ajmal; Al-Hemaid, Fahad M A
2014-09-01
A simple and sensitive electrochemical method has been proposed for the determination of isoniazid (INZ). For the first time, rhodium (Rh) modified glassy carbon electrode (GCE) has been employed for the determination of INZ by linear sweep voltammetry technique (LSV). Compared with the unmodified electrode, the proposed Rh modified electrode provides strong electrocatalytic activity toward INZ with significant enhancement in the anodic peak current. Scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM) results reveal the morphology of Rh particles. With the advantages of wide linearity (70-1300μM), good sensitivity (0.139μAμM(-1)cm(-2)) and low detection limit (13μM), this proposed sensor holds great potential for the determination of INZ in real samples. The practicality of the proposed electrode for the detection of INZ in human urine and blood plasma samples has been successfully demonstrated using LSV technique. Through the determination of INZ in commercially available pharmaceutical tablets, the practical applicability of the proposed method has been validated. The recovery results are found to be in good agreement with the labeled amounts of INZ in tablets, thus showing its great potential for use in clinical and pharmaceutical analysis. Copyright © 2014 Elsevier B.V. All rights reserved.
Oxidation-Resistant Surfaces For Solar Reflectors
NASA Technical Reports Server (NTRS)
Gulino, Daniel A.; Egger, Robert A.; Banholzer, William F.
1988-01-01
Thin films on silver provide highly-reflective, corrosion-resistant mirrors. Study evaluated variety of oxidation-resistant reflective materials for use in solar dynamic power system, one that generates electricity by focusing Sunlight onto reciever of heat engine. Thin films of platinum and rhodium deposited by ion-beam sputtering on various substrate materials. Solar reflectances measured as function of time of exposure to radio-frequency-generated air plasma. Several protective coating materials deposited on silver-coated substrates and exposed to plasma. Analyzed before and after exposure by electon spectroscopy for chemical analysis and by Auger spectroscopy.
Constraining global dry deposition of ozone: observations and modeling
NASA Astrophysics Data System (ADS)
Silva, S. J.; Heald, C. L.
2016-12-01
Ozone loss through dry deposition to vegetation is a critically important process for both air quality and ecosystem health. Current estimates are that nearly 25% of all surface ozone is destroyed through dry deposition, and billions of dollars are lost annually due to losses of ecosystem services and agricultural yield associated with ozone damage. However there are still substantial uncertainties regarding the spatial distribution and magnitude of the global depositional flux. As land cover change continues throughout this century, dry deposition of ozone will change in ways that are yet still poorly understood. Nearly every major atmospheric chemistry model uses a variation of the "resistor in series parameterization" for the calculation of dry deposition. By far the most commonly implemented parameterization is of the form presented in Wesely (1989), and is dependent on many variables, including land type look up tables, solar radiation, leaf area index, temperature, and more. The uncertainties contained within the various parts of this parameterization have to date not been fully explored. A lack of understanding of these uncertainties, coupled with a dearth of routine measurements of ozone deposition, ultimately challenges our ability to understand the impacts of land cover change on surface ozone. In this work, we use a suite of globally-distributed observations from the past two decades and the GEOS-Chem chemical transport model to constrain global dry deposition, improve our understanding of these uncertainties, and contextualize the impact of land cover change on ozone concentrations.
Carnacina, Iacopo; Larrarte, Frédérique; Leonardi, Nicoletta
2017-04-01
The performance of sewer networks has important consequences from an environmental and social point of view. Poor functioning can result in flood risk and pollution at a large scale. Sediment deposits forming in sewer trunks might severely compromise the sewer line by affecting the flow field, reducing cross-sectional areas, and increasing roughness coefficients. In spite of numerous efforts, the morphological features of these depositional environments remain poorly understood. The interface between water and sediment remains inefficiently identified and the estimation of the stock of deposit is frequently inaccurate. In part, this is due to technical issues connected to difficulties in collecting accurate field measurements without disrupting existing morphologies. In this paper, results from an extensive field campaign are presented; during the campaign a new survey methodology based on acoustic techniques has been tested. Furthermore, a new algorithm for the detection of the soil-water interface, and therefore for the correct esteem of sediment stocks is proposed. Finally, results in regard to bed topography, and morphological features at two different field sites are presented and reveal that a large variability in bed forms is present along sewer networks. Copyright © 2017 Elsevier Ltd. All rights reserved.
Azari, Abbas; Nikzad, Sakineh; Yazdani, Arash; Atri, Faezeh; Fazel Anvari-Yazdi, Abbas
2017-07-01
The poor bonding strength of zirconia to different dental substrates is one of the challenging issues in restorative dentistry. Hydroxyapatite is an excellent biocompatible material with fine bonding properties. In this study, it was hypothesized that hydroxyapatite coating on zirconia would improve its bond strength. Forty-five zirconia blocks were prepared and randomly divided into three groups: hydroxyapatite coating, sandblasting, and no preparation (control). The blocks were bonded to cement and the micro-shear bond strength was measured following load application. The bond strength values were analyzed with the Kruskal-Wallis test in 3 groups and paired comparisons were made using the Mann-Whitney U test. The failure patterns of the specimens were studied by a stereomicroscope and a scanning electron microscope and then analyzed by the chi-square test (significance level = 0.05). Deposition of hydroxyapatite on the zirconia surface significantly improved its bond strength to the resin cement in comparison with the control specimens (p < 0.0001). Also, the bond strength was similar to the sandblasted group (p = 0.34). The sandblasted and control group only showed adhesive failure, but the hydroxyapatite coated group had mixed failures, indicating the better quality of bonding (p < 0.0001). As a final point, hydroxyapatite coating on the zirconia surface improved the bond strength quality and values.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Baumgartner, F.; Bedmar, A.P.
1961-01-01
BS>Ru and Rh isotopes with mass numbers 107 and 108 and Rh/sup 109/ were obtained from fission products. Ru/sup 107/ was also prepared by the nuclear process Pd/sup 110/ (n, alpha ) Ru/sup 107/. Beta and gamma energies of these nuclides were studied spectrometrically and the gamma lines found for Ru/sup 107/ and Ru/sup 108/ (and daughter) were useful for the precise determination of their half lives. Rh/sup 109/ was identified through its daughter Pd/sup 109/ in the mixture of rhodium isotopes from fission products. lrradiation of natural paladium with fast neutrons led to an activity that may only bemore » attributed to Rh/ sup 110/. Neither its half life nor its decay energy was determined accurately. (auth)« less
NASA Astrophysics Data System (ADS)
Sakamoto, Ryota L.; Morinaga, Shin-Ichi
2013-09-01
Pollinators deposit pollen grains on stigmas and remove pollen grains from anthers. The mechanics of these transfers can now be quantified with the use of high-speed video. We videoed hawkmoths, carpenter bees, and swallowtail butterflies pollinating Clerodendrum trichotomum. The number of grains deposited on stigmas did not vary significantly with the number of times pollinators contacted stigmas. In contrast, pollen removal from the anthers increased significantly with the number of contacts to anthers. Pollen removal varied among the three types of pollinators. Also, the three types carried pollen on different parts of their bodies. In hawkmoths and carpenter bees, a large number of contacted body part with anthers differed significantly from the body part that attached a large number of pollen grains. Our results indicate that a large number of contacts by pollinators does not increase either the male or female reproductive success of plants compared to a small number of contacts during a visit.
Deposit model for volcanogenic uranium deposits
Breit, George N.; Hall, Susan M.
2011-01-01
The International Atomic Energy Agency's tabulation of volcanogenic uranium deposits lists 100 deposits in 20 countries, with major deposits in Russia, Mongolia, and China. Collectively these deposits are estimated to contain uranium resources of approximately 500,000 tons of uranium, which amounts to 6 percent of the known global resources. Prior to the 1990s, these deposits were considered to be small (less than 10,000 tons of uranium) with relatively low to moderate grades (0.05 to 0.2 weight percent of uranium). Recent availability of information on volcanogenic uranium deposits in Asia highlighted the large resource potential of this deposit type. For example, the Streltsovskoye district in eastern Russia produced more than 100,000 tons of uranium as of 2005; with equivalent resources remaining. Known volcanogenic uranium deposits within the United States are located in Idaho, Nevada, Oregon, and Utah. These deposits produced an estimated total of 800 tons of uranium during mining from the 1950s through the 1970s and have known resources of 30,000 tons of uranium. The most recent estimate of speculative resources proposed an endowment of 200,000 tons of uranium.
Distribution of soil selenium in China is potentially controlled by deposition and volatilization?
Sun, Guo-Xin; Meharg, Andrew A.; Li, Gang; Chen, Zheng; Yang, Lei; Chen, Song-Can; Zhu, Yong-Guan
2016-01-01
Elucidating the environmental drivers of selenium (Se) spatial distribution in soils at a continental scale is essential to better understand it’s biogeochemical cycling to improve Se transfer into diets. Through modelling Se biogeochemistry in China we found that deposition and volatilization are key factors controlling distribution in surface soil, rather than bedrock-derived Se (<0.1 mg/kg). Wet deposition associated with the East Asian summer monsoon, and dry deposition associated with the East Asian winter monsoon, are responsible for dominant Se inputs into northwest and southeast China, respectively. In Central China the rate of soil Se volatilization is similar to that of Se deposition, suggesting that Se volatilization offsets it’s deposition, resulting in negligible net Se input in soil. Selenium in surface soil at Central China is roughly equal to low petrogenic Se, which is the main reason for the presence of the Se poor belt. We suggest that both deposition and volatilization of Se could play a key role in Se balance in other terrestrial environments worldwide. PMID:26883576
NASA Astrophysics Data System (ADS)
Wang, Linlin; Wang, Zhenqi; Yu, Shui; Ngia, Ngong Roger
2016-08-01
The Miocene deepwater gravity-flow sedimentary system in Block A of the southwestern part of the Lower Congo Basin was identified and interpreted using high-resolution 3-D seismic, drilling and logging data to reveal development characteristics and main controlling factors. Five types of deepwater gravity-flow sedimentary units have been identified in the Miocene section of Block A, including mass transport, deepwater channel, levee, abandoned channel and sedimentary lobe deposits. Each type of sedimentary unit has distinct external features, internal structures and lateral characteristics in seismic profiles. Mass transport deposits (MTDs) in particular correspond to chaotic low-amplitude reflections in contact with mutants on both sides. The cross section of deepwater channel deposits in the seismic profile is in U- or V-shape. The channel deposits change in ascending order from low-amplitude, poor-continuity, chaotic filling reflections at the bottom, to high-amplitude, moderate to poor continuity, chaotic or sub-parallel reflections in the middle section and to moderate-weak amplitude, good continuity, parallel or sub-parallel reflections in the upper section. The sedimentary lobes are laterally lobate, which corresponds to high-amplitude, good-continuity, moundy reflection signatures in the seismic profile. Due to sediment flux, faults, and inherited terrain, few mass transport deposits occur in the northeastern part of the study area. The front of MTDs is mainly composed of channel-levee complex deposits, while abandoned-channel and lobe-deposits are usually developed in high-curvature channel sections and the channel terminals, respectively. The distribution of deepwater channel, levee, abandoned channel and sedimentary lobe deposits is predominantly controlled by relative sea level fluctuations and to a lesser extent by tectonism and inherited terrain.
NASA Astrophysics Data System (ADS)
Xie, Chao
2011-12-01
The present work was conducted to develop a better understanding on the catalyst deactivation in steam reforming of sulfur-containing liquid hydrocarbon fuels for hydrogen production. Steam reforming of Norpar13 (a liquid hydrocarbon fuel from Exxon Mobile) without and with sulfur was performed on various metal catalysts (Rh, Ru, Pt, Pd, and Ni) supported on different materials (Al2O3, CeO2, SiO2, MgO, and CeO2- Al2O3). A number of characterization techniques were applied to study the physicochemical properties of these catalysts before and after the reactions. Especially, X-ray absorption near edge structure (XANES) spectroscopy was intensively used to investigate the nature of sulfur and carbon species in the used catalysts to reveal the catalyst deactivation mechanism. Among the tested noble metal catalysts (Rh, Ru, Pt, and Pd), Rh catalyst is the most sulfur tolerant. Al2O3 and CeO2 are much better than SiO2 and MgO as the supports for the Rh catalyst to reform sulfur-containing hydrocarbons. The good sulfur tolerance of Rh/Al2O3 can be attributed to the acidic nature of the Al2O3 support and its small Rh crystallites (1-3 nm) as these characteristics facilitate the formation of electron-deficient Rh particles with high sulfur tolerance. The good catalytic performance of Rh/CeO2 in the presence of sulfur can be ascribed to the promotion effect of CeO2 on carbon gasification, which significantly reduced the carbon deposition on the Rh/CeO2catalyst. Steam reforming of Norpar13 in the absence and presence of sulfur was further carried out over CeO2-Al2O3 supported monometallic Ni and Rh and bimetallic Rh-Ni catalysts at 550 and 800 °C. Both monometallic catalysts rapidly deactivated at 550 °C, iv and showed poor sulfur tolerance. Although ineffective for the Ni catalyst, increasing the temperature to 800 °C dramatically improved the sulfur tolerance of the Rh catalyst. Sulfur K-edge XANES revealed that metal sulfide and organic sulfide are the dominant sulfur
Appraisal of iron deposits in southern and western Turkey
Gair, Jacob Eugene; Capan, Ussal Z.
1972-01-01
Between May 20 and June 17, 1969, previously known iron deposits were examined widely at eight separate localities in western Turkey. The object of the examinations was to learn the, nature, geologic setting, and approximate size of each deposit, to review prior estimates of size, and possibly recommend additional exploratory work.. The full extent of each deposit is poorly known at the present time, so recommended additional work entails drilling, digging trenches or pits, geologic mapping or, combinations of these activities. On Qaldagi Mountain an area of about 1 sq km is capped by bredciated chert under which may be a continuous zone of mixed iron oxides and chert fragments. The thickness of the ferruginous zone is poorly known but is as much as 12 meters, in at least one place. The- ferruginous material and chert appear to have formed by the weathering of serpentine, bun this concept needs further testing. Drilling is recommended to determine the grade, thickness, and extent-of the ferruginous zone beneath the cherty cap. Inasmuch as mining by hand sorting is in progress, part of the deposit can be considered to be marginally in the category of iron reserves. The Keceborlu iron deposit consists of earthy to slightly compacted hematite and limonite mixed with small chert fragments. The surface area underlain by ferruginous rock is about 5,000 to 7,500 sq meters. The maximum known thickness of the deposit is about 7 meters. Iron appears to have been concentrated by weathering and oxidation of cherty limestone. The deposit is probably either a remnant of a once more extensive weathered cap, or a sink hole filling. The Keceborlu area warrants a low priority for further exploration, but one drill hole is recommended to test the thickness of the deposit. The iron deposits at Mellec are layered and vein-magnetite replacements of limestone. The six known deposits are discontinuous. No additional. work is recommended. ' The Gilindire Iron deposit consists of irregular
NITROGEN OUTPUTS FROM FECAL AND URINE DEPOSITION OF SMALL MAMMALS: IMPLICATIONS FOR NITROGEN CYCLING
The contribution of small mammals to nitrogen cycling is poorly understood, but it could have reverberations back to the producer community by maintaining or perhaps magnifying nitrogen availability. Our objective was to model nitrogen outputs (deposition of feces and urine) of ...
NITROGEN OUTPUTS OF SMALL MAMMALS FROM FECAL AND URINE DEPOSITION: IMPLICATIONS FOR NITROGEN CYCLING
The contribution of small mammals in nitrogen cycling is poorly understood and could have reverberations back to the producer community by maintaining or even magnifying increased nitrogen availability. Our objective was to model nitrogen outputs (deposition of feces and urine) ...
Towards the definition of AMS facies in the deposits of pyroclastic density currents
Ort, M.H.; Newkirk, T.T.; Vilas, J.F.; Vazquez, J.A.; Ort, M.H.; Porreca, Massimiliano; Geissman, J.W.
2014-01-01
Anisotropy of magnetic susceptibility (AMS) provides a statistically robust technique to characterize the fabrics of deposits of pyroclastic density currents (PDCs). AMS fabrics in two types of pyroclastic deposits (small-volume phreatomagmatic currents in the Hopi Buttes volcanic field, Arizona, USA, and large-volume caldera-forming currents, Caviahue Caldera, Neuquén, Argentina) show similar patterns. Near the vent and in areas of high topographical roughness, AMS depositional fabrics are poorly grouped, with weak lineations and foliations. In a densely welded proximal ignimbrite, this fabric is overprinted by a foliation formed as the rock compacted and deformed. Medial deposits have moderate–strong AMS lineations and foliations. The most distal deposits have strong foliations but weak lineations. Based on these facies and existing models for pyroclastic density currents, deposition in the medial areas occurs from the strongly sheared, high-particle-concentration base of a density-stratified current. In proximal areas and where topography mixes this denser base upwards into the current, deposition occurs rapidly from a current with little uniformity to the shear, in which particles fall and collide in a chaotic fashion. Distal deposits are emplaced by a slowing or stalled current so that the dominant particle motion is vertical, leading to weak lineation and strong foliation.
NASA Astrophysics Data System (ADS)
Stepien, Z.
2016-09-01
Generally, ethanol fuel emits less pollutants than gasoline, it is completely renewable product and has the potential to reduce greenhouse gases emission but, at the same time can present a multitude of technical challenges to engine operation conditions including creation of very adverse engine deposits. These deposits increasing fuel consumption and cause higher exhaust emissions as well as poor performance in drivability. This paper describes results of research and determination the various factors influencing injector deposits build-up of ethanol-gasoline blends operated engine. The relationship between ethanol-gasoline fuel blends composition, their treatment, engine construction as well as its operation conditions and fuel injectors deposit formation has been investigated. Simulation studies of the deposit formation endanger proper functioning of fuel injection system were carried out at dynamometer engine testing. As a result various, important factors influencing the deposit creation process and speed formation were determined. The ability to control of injector deposits by multifunctional detergent-dispersant additives package fit for ethanol-gasoline blends requirements was also investigated.
Persistence of soil organic matter in eroding versus depositional landform positions
Berhe, Asmeret Asefaw; Harden, Jennifer W.; Torn, Margaret S.; Kleber, Markus; Burton, Sarah D.; Harte, John
2012-01-01
Soil organic matter (SOM) processes in dynamic landscapes are strongly influenced by soil erosion and sedimentation. We determined the contribution of physical isolation of organic matter (OM) inside aggregates, chemical interaction of OM with soil minerals, and molecular structure of SOM in controlling storage and persistence of SOM in different types of eroding and depositional landform positions. By combining density fractionation with elemental and spectroscopic analyses, we showed that SOM in depositional settings is less transformed and better preserved than SOM in eroding landform positions. However, which environmental factors exert primary control on storage and persistence of SOM depended on the nature of the landform position considered. In an annual grassland watershed, protection of SOM by physical isolation inside aggregates and chemical association of organic matter (complexation) with soil minerals, as assessed by correlation with radiocarbon concentration, were more effective in the poorly drained, lowest-lying depositional landform positions, compared to well-drained landform positions in the upper parts of the watershed. Results of this study demonstrated that processes of soil erosion and deposition are important mechanisms of long-term OM stabilization.
Evaporite deposits of Bogota area, Cordillera Oriental, Colombia
McLaughlin, Donald H.
1972-01-01
Four evaporite-bearing stratigraphic zones are known in Cretaceous strata of the Cordillera Oriental of Colombia north and east of Bogota. The easternmost and oldest zone is probably of Berriasian to Valanginian age. The next oldest is probably late Barremian to early Aptian in age. The third appears to be Aptian. The westernmost and best known sequence in the Sabana de Bogota is Turonian to early Coniacian in age. This youngest sequence contains the thickest salt deposits known in Colombia and is probably the most widespread geographically.Most of the rock salt exposed in the three accessible mines (at Zipaquira, Nemocon, and Upin) has a characteristic lamination of alternating slightly argillaceous and highly argillaceous salt layers of varied but moderate thickness. Black, calcareous claystone, commonly very pyritic, is interbedded conformably with the laminated salt in many places throughout the deposits. Fragments of black claystone derived from the thinner interbeds are ubiquitous in all deposits, both as concordant breccia zones and as isolated clasts.Anhydrite is scarce at Zipaquira and apparently even rarer at Nemocon and Upin. Gypsum is produced at three small deposits in the oldest evaporite zone where it probably was concentrated by leaching of salt initially associated with it.The two intervening evaporite zones are not exposed, but their existence and distribution are indicated by brine springs and locally by "rute," a distinctive black, calcareous mud formed by the leaching of salt beds.Fossils show that the youngest salt-claystone zone, in the Sabana de Bogota, is contemporary with associated hematitic sandstone and siltstone, and with carbonaceous and locally coaly claystone. Although evidence is poor, this same facies relation probably exists within the other three evaporite zones.All salt deposits in this study probably are associated with anticlines, a relation best exemplified by the deposits on the Sabana de Bogota. Within these anticlines the
Rapid Deposition of Oxidized Biogenic Compounds to a Temperate Forest
NASA Technical Reports Server (NTRS)
Nguyen, Tran B.; Crounse, John D.; Teng, Alex P.; St. Clair, Jason M.; Paulot, Fabien; Wolfe, Glenn M.; Wennberg, Paul O.
2015-01-01
We report fluxes and dry deposition velocities for 16 atmospheric compounds above a southeastern United States forest, including: hydrogen peroxide (H2O2), nitric acid (HNO3), hydrogen cyanide (HCN), hydroxymethyl hydroperoxide, peroxyacetic acid, organic hydroxy nitrates, and other multifunctional species derived from the oxidation of isoprene and monoterpenes. The data suggest that dry deposition is the dominant daytime sink for small, saturated oxygenates. Greater than 6 wt %C emitted as isoprene by the forest was returned by dry deposition of its oxidized products. Peroxides account for a large fraction of the oxidant flux, possibly eclipsing ozone in more pristine regions. The measured organic nitrates comprise a sizable portion (15%) of the oxidized nitrogen input into the canopy, with HNO3 making up the balance. We observe that water-soluble compounds (e.g., strong acids and hydroperoxides) deposit with low surface resistance whereas compounds with moderate solubility (e.g., organic nitrates and hydroxycarbonyls) or poor solubility (e.g., HCN) exhibited reduced uptake at the surface of plants. To first order, the relative deposition velocities of water-soluble compounds are constrained by their molecular diffusivity. From resistance modeling, we infer a substantial emission flux of formic acid at the canopy level (approx. 1 nmol m(exp.-2)·s(exp.-1)). GEOS-Chem, awidely used atmospheric chemical transport model, currently underestimates dry deposition for most molecules studied in this work. Reconciling GEOS-Chem deposition velocities with observations resulted in up to a 45% decrease in the simulated surface concentration of trace gases.
Rapid deposition of oxidized biogenic compounds to a temperate forest
Nguyen, Tran B.; Crounse, John D.; Teng, Alex P.; St. Clair, Jason M.; Paulot, Fabien; Wolfe, Glenn M.; Wennberg, Paul O.
2015-01-01
We report fluxes and dry deposition velocities for 16 atmospheric compounds above a southeastern United States forest, including: hydrogen peroxide (H2O2), nitric acid (HNO3), hydrogen cyanide (HCN), hydroxymethyl hydroperoxide, peroxyacetic acid, organic hydroxy nitrates, and other multifunctional species derived from the oxidation of isoprene and monoterpenes. The data suggest that dry deposition is the dominant daytime sink for small, saturated oxygenates. Greater than 6 wt %C emitted as isoprene by the forest was returned by dry deposition of its oxidized products. Peroxides account for a large fraction of the oxidant flux, possibly eclipsing ozone in more pristine regions. The measured organic nitrates comprise a sizable portion (15%) of the oxidized nitrogen input into the canopy, with HNO3 making up the balance. We observe that water-soluble compounds (e.g., strong acids and hydroperoxides) deposit with low surface resistance whereas compounds with moderate solubility (e.g., organic nitrates and hydroxycarbonyls) or poor solubility (e.g., HCN) exhibited reduced uptake at the surface of plants. To first order, the relative deposition velocities of water-soluble compounds are constrained by their molecular diffusivity. From resistance modeling, we infer a substantial emission flux of formic acid at the canopy level (∼1 nmol m−2⋅s−1). GEOS−Chem, a widely used atmospheric chemical transport model, currently underestimates dry deposition for most molecules studied in this work. Reconciling GEOS−Chem deposition velocities with observations resulted in up to a 45% decrease in the simulated surface concentration of trace gases. PMID:25605913
The Grainsize Characteristics of Coignimbrite Deposits
NASA Astrophysics Data System (ADS)
Engwell, Samantha; Eychenne, Julia
2015-04-01
. The deposits are very fine grained (< 100 microns), have unimodal grain size distributions skewed towards the fines, and are more poorly sorted in medial to distal areas than tephra fall deposits from vent-derived plumes at the same distance. Deposits from a single eruption show constant grain size over hundreds to thousands of kilometres, except for a slight coarsening close to source in some cases. In intermediate size eruptions, co-ignimbrite ash often settles synchronously to vent-derived tephra, leading to bimodal grain size fallout deposits. These observations highlight the propensity of the ash to remain in the atmosphere for extended periods of time, and pose important questions regarding how the ash is deposited, and especially the role of aggregation. The uniformity of co-ignimbrite ash means that, with regards to real-time dispersion modelling during an eruption, few assumptions are required for the initial grain size, however depositional assumptions utilised when modelling vent-derived plume dispersion, may not be able to accurately reproduce co-ignimbrite depositional patterns.
Empirical Determination of Dark Matter Velocities Using Metal-Poor Stars
NASA Astrophysics Data System (ADS)
Herzog-Arbeitman, Jonah; Lisanti, Mariangela; Madau, Piero; Necib, Lina
2018-01-01
The Milky Way dark matter halo is formed from the accretion of smaller subhalos. These sub-units also harbor stars—typically old and metal-poor—that are deposited in the Galactic inner regions by disruption events. In this Letter, we show that the dark matter and metal-poor stars in the Solar neighborhood share similar kinematics due to their common origin. Using the high-resolution eris simulation, which traces the evolution of both the dark matter and baryons in a realistic Milky Way analog galaxy, we demonstrate that metal-poor stars are indeed effective tracers for the local, virialized dark matter velocity distribution. The local dark matter velocities can therefore be inferred from observations of the stellar halo made by the Sloan Digital Sky Survey within 4 kpc of the Sun. This empirical distribution differs from the standard halo model in important ways and suggests that the bounds on the spin-independent scattering cross section may be weakened for dark matter masses below ˜10 GeV . Data from Gaia will allow us to further refine the expected distribution for the smooth dark matter component, and to test for the presence of local substructure.
Haydl, Alexander M; Breit, Bernhard
2015-12-14
Natural products of polyketide origin with a high level of symmetry, in particular C2 -symmetric diolides as a special macrolactone-based product class, often possess a broad spectrum of biological activity. An efficient route to this important structural motif was developed as part of a concise and highly convergent synthesis of clavosolide A. This strategy features an atom-economic "head-to-tail" dimerization by the stereoselective rhodium-catalyzed addition of carboxylic acids to terminal allenes with the simultaneous construction of two new stereocenters. The excellent efficiency and selectivity with which the C2 -symmetric core structures were obtained are remarkable considering the outcome under classical dimerization conditions. Furthermore, this approach facilitates late-stage modification and provides ready access to potential new lead structures. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Han, Sejin; Li, Yuk Yin; Chan, Barbara Pui
2015-10-15
Collagen is a widely used naturally occurring biomaterial for scaffolding, whereas mesenchymal stem cells (MSCs) represent a promising cell source in tissue engineering and regenerative medicine. It is generally known that cells are able to remodel their environment by simultaneous degradation of the scaffolds and deposition of newly synthesized extracellular matrix. Nevertheless, the interactions between MSCs and collagen biomaterials are poorly known, and the strategies enhancing the extracellular matrix deposition are yet to be defined. In this study, we aim to investigate the fate of collagen when it is in contact with MSCs and hypothesize that protease inhibition will enhance their extracellular deposition of collagen fibrils. Specifically, human MSCs (hMSCs) were exposed to fluorescence-labeled collagen with and without intracellular or extracellular protease inhibitors (or both) before tracing the collagen at both intracellular and extracellular spaces. Collagen were internalized by hMSCs and degraded intracellularly in lysosomes. In the presence of protease inhibitors, both intracellular collagen fibril growth and extracellular deposition of collagen fibrils were enhanced. Moreover, protease inhibitors work synergistically with ascorbic acid, a well-known matrix deposition-enhancing reagent, in further enhancing collagen fibril deposition at the extracellular space. These findings provide a better understanding of the interactions between hMSCs and collagen biomaterials and suggest a method to manipulate matrix remodeling and deposition of hMSCs, contributing to better scaffolding for tissue engineering and regenerative medicine.
Granath, Gustaf; Strengbom, Joachim; Breeuwer, Angela; Heijmans, Monique M P D; Berendse, Frank; Rydin, Håkan
2009-04-01
Increased N deposition in Europe has affected mire ecosystems. However, knowledge on the physiological responses is poor. We measured photosynthetic responses to increasing N deposition in two peatmoss species (Sphagnum balticum and Sphagnum fuscum) from a 3-year, north-south transplant experiment in northern Europe, covering a latitudinal N deposition gradient ranging from 0.28 g N m(-2) year(-1) in the north, to 1.49 g N m(-2) year(-1) in the south. The maximum photosynthetic rate (NP(max)) increased southwards, and was mainly explained by tissue N concentration, secondly by allocation of N to the photosynthesis, and to a lesser degree by modified photosystem II activity (variable fluorescence/maximum fluorescence yield). Although climatic factors may have contributed, these results were most likely attributable to an increase in N deposition southwards. For S. fuscum, photosynthetic rate continued to increase up to a deposition level of 1.49 g N m(-2) year(-1), but for S. balticum it seemed to level out at 1.14 g N m(-2) year(-1). The results for S. balticum suggested that transplants from different origin (with low or intermediate N deposition) respond differently to high N deposition. This indicates that Sphagnum species may be able to adapt or physiologically adjust to high N deposition. Our results also suggest that S. balticum might be more sensitive to N deposition than S. fuscum. Surprisingly, NP(max) was not (S. balticum), or only weakly (S. fuscum) correlated with biomass production, indicating that production is to a great extent is governed by factors other than the photosynthetic capacity.
ERIC Educational Resources Information Center
Rothman, Sheila M.
1977-01-01
Suggests that freedom for the middle classes may mean vulnerability for the poor. The enthusiasm for sterilization may be so intense as to deprive the poor of their right not to be sterilized. (Author/AM)
2014-01-01
A 2,2′-bipyridyl-containing poly(arylene-ethynylene)-alt-poly(arylene-vinylene) polymer, acting as a light-harvesting ligand system, was synthesized and coupled to an organometallic rhodium complex designed for photocatalytic NAD+/NADH reduction. The material, which absorbs over a wide spectral range, was characterized by using various analytical techniques, confirming its chemical structure and properties. The dielectric function of the material was determined from spectroscopic ellipsometry measurements. Photocatalytic reduction of nucleotide redox cofactors under visible light irradiation (390–650 nm) was performed and is discussed in detail. The new metal-containing polymer can be used to cover large surface areas (e.g. glass beads) and, due to this immobilization step, can be easily separated from the reaction solution after photolysis. Because of its high stability, the polymer-based catalyst system can be repeatedly used under different reaction conditions for (photo)chemical reduction of NAD+. With this concept, enzymatic, photo-biocatalytic systems for solar energy conversion can be facilitated, and the precious metal catalyst can be recycled. PMID:25130570
Surface properties of Mars' polar layered deposits and polar landing sites
Vasavada, Ashwin R.; Williams, Jean-Pierre; Paige, David A.; Herkenhoff, Ken E.; Bridges, Nathan T.; Greeley, Ronald; Murray, Bruce C.; Bass, Deborah S.; McBride, Karen S.
2000-01-01
On December 3, 1999, the Mars Polar Lander and Mars Microprobes will land on the planet's south polar layered deposits near (76°S, 195°W) and conduct the first in situ studies of the planet's polar regions. The scientific goals of these missions address several poorly understood and globally significant issues, such as polar meteorology, the composition and volatile content of the layered deposits, the erosional state and mass balance of their surface, their possible relationship to climate cycles, and the nature of bright and dark aeolian material. Derived thermal inertias of the southern layered deposits are very low (50-100 J m-2 s-1/2 K-1), suggesting that the surface down to a depth of a few centimeters is generally fine grained or porous and free of an appreciable amount of rock or ice. The landing site region is smoother than typical cratered terrain on ∼1 km pixel-1 Viking Orbiter images but contains low-relief texture on ∼5 to 100 m pixel-1 Mariner 9 and Mars Global Surveyor images. The surface of the southern deposits is older than that of the northern deposits and appears to be modified by aeolian erosion or ablation of ground ice.
UV photofunctionalization promotes nano-biomimetic apatite deposition on titanium
Saita, Makiko; Ikeda, Takayuki; Yamada, Masahiro; Kimoto, Katsuhiko; Lee, Masaichi Chang-Il; Ogawa, Takahiro
2016-01-01
Background Although biomimetic apatite coating is a promising way to provide titanium with osteoconductivity, the efficiency and quality of deposition is often poor. Most titanium implants have microscale surface morphology, and an addition of nanoscale features while preserving the micromorphology may provide further biological benefit. Here, we examined the effect of ultraviolet (UV) light treatment of titanium, or photofunctionalization, on the efficacy of biomimetic apatite deposition on titanium and its biological capability. Methods and results Micro-roughed titanium disks were prepared by acid-etching with sulfuric acid. Micro-roughened disks with or without photofunctionalization (20-minute exposure to UV light) were immersed in simulated body fluid (SBF) for 1 or 5 days. Photofunctionalized titanium disks were superhydrophilic and did not form surface air bubbles when immersed in SBF, whereas non-photofunctionalized disks were hydrophobic and largely covered with air bubbles during immersion. An apatite-related signal was observed by X-ray diffraction on photofunctionalized titanium after 1 day of SBF immersion, which was equivalent to the one observed after 5 days of immersion of control titanium. Scanning electron microscopy revealed nodular apatite deposition in the valleys and at the inclines of micro-roughened structures without affecting the existing micro-configuration. Micro-roughened titanium and apatite-deposited titanium surfaces had similar roughness values. The attachment, spreading, settling, proliferation, and alkaline phosphate activity of bone marrow-derived osteoblasts were promoted on apatite-coated titanium with photofunctionalization. Conclusion UV-photofunctionalization of titanium enabled faster deposition of nanoscale biomimetic apatite, resulting in the improved biological capability compared to the similarly prepared apatite-deposited titanium without photofunctionalization. Photofunctionalization-assisted biomimetic apatite
Abu Bakar, Norhayati; Mat Salleh, Muhamad; Ali Umar, Akrajas; Shapter, Joseph George
2017-01-01
Silver nanoparticles deposited on quartz substrates are widely used as SERS substrates. The nanoparticles can be deposited directly from colloidal solution by dipping technique. However, the adhesion of the particles on the quartz surface is very poor. Normally the substrate is pre-treated with hydroxylation or silanisation process. In this paper, we have demonstrated that the application of the sequence pre-treatment hydroxylation and silanisation have improved the density of silver nanoplates desposited on the quartz surface. •Sequence hydroxylation and silanisation pre-treatment assists the deposition of the nanoplate on the surface.•Various immersion times of the quartz surface into the colloidal nanoplates determined size distributions and density surface of the nanoplates on the surface.
Gardner, C.A.; Neal, C.A.; Waitt, R.B.; Janda, R.J.
1994-01-01
More than 20 eruptive events during the 1989-1990 eruption of Redoubt Volcano emplaced a complex sequence of lithic pyroclastic-flow, -surge, -fall, ice-diamict, and lahar deposits mainly on the north side of the volcano. The deposits record the changing eruption dynamics from initial gas-rich vent-clearing explosions to episodic gas-poor lava-dome extrusions and failures. The repeated dome failures produced lithic pyroclastic flows that mixed with snow and glacial ice to generate lahars that were channelled off Drift glacier into the Drift River valley. Some of the dome failures occurred without precursory seismic warning and appeared to result solely from gravitational instability. Material from the disrupted lava domes avalanched down a steep, partly ice-filled canyon incised on the north flank of the volcano and came to rest on the heavily crevassed surface of the piedmont lobe of Drift glacier. Most dome-collapse events resulted in single, monolithologic, massive to reversely graded, medium- to coarse-grained, sandy pyroclastic-flow deposits containing abundant dense dome clasts. These deposits vary in thickness, grain size, and texture depending on distance from the vent and local topography; deposits are finer and better sorted down flow, thinner and finer on hummocks, and thicker and coarser where ponded in channels cut through the glacial ice. The initial vent-clearing explosions emplaced unusual deposits of glacial ice, snow, and rock in a frozen matrix on the north and south flanks of the volcano. Similar deposits were described at Nevado del Ruiz, Columbia and have probably been emplaced at other snow-and-ice-clad volcanoes, but poor preservation makes them difficult to recognize in the geologic record. In a like fashion, most deposits from the 1989-1990 eruption of Redoubt Volcano may be difficult to recognize and interpret in the future because they were emplaced in an environment where glacio-fluvial processes dominate and quickly obscure the primary
Zhang, Lei; Kundu, Soumi; Feenstra, Tjerk; Li, Xiujuan; Jin, Chuan; Laaniste, Liisi; El Hassan, Tamador Elsir Abu; Ohlin, K Elisabet; Yu, Di; Olofsson, Tommie; Olsson, Anna-Karin; Pontén, Fredrik; Magnusson, Peetra U; Nilsson, Karin Forsberg; Essand, Magnus; Smits, Anja; Dieterich, Lothar C; Dimberg, Anna
2015-12-08
Glioblastomas are aggressive astrocytomas characterized by endothelial cell proliferation and abnormal vasculature, which can cause brain edema and increase patient morbidity. We identified the heparin-binding cytokine pleiotrophin as a driver of vascular abnormalization in glioma. Pleiotrophin abundance was greater in high-grade human astrocytomas and correlated with poor survival. Anaplastic lymphoma kinase (ALK), which is a receptor that is activated by pleiotrophin, was present in mural cells associated with abnormal vessels. Orthotopically implanted gliomas formed from GL261 cells that were engineered to produce pleiotrophin showed increased microvessel density and enhanced tumor growth compared with gliomas formed from control GL261 cells. The survival of mice with pleiotrophin-producing gliomas was shorter than that of mice with gliomas that did not produce pleiotrophin. Vessels in pleiotrophin-producing gliomas were poorly perfused and abnormal, a phenotype that was associated with increased deposition of vascular endothelial growth factor (VEGF) in direct proximity to the vasculature. The growth of pleiotrophin-producing GL261 gliomas was inhibited by treatment with the ALK inhibitor crizotinib, the ALK inhibitor ceritinib, or the VEGF receptor inhibitor cediranib, whereas control GL261 tumors did not respond to either inhibitor. Our findings link pleiotrophin abundance in gliomas with survival in humans and mice, and show that pleiotrophin promotes glioma progression through increased VEGF deposition and vascular abnormalization. Copyright © 2015, American Association for the Advancement of Science.
Geochemical signatures of tsunami deposits - what do they tell us?
NASA Astrophysics Data System (ADS)
Chague-Goff, Catherine; Goff, James R.
2010-05-01
In the last two and half decades, but even more since the 2004 Indian Ocean Tsunami (IOT), there has been a significant increase in the amount of literature dealing with recent, historical and palaeotsunamis. Much has been written and debated about the diagnostic criteria of historical and palaeotsunami deposits. Most of the diagnostic criteria or proxies used reflect the expertise of the researchers involved and thus tend to be biased towards sedimentology, stratigraphy and micropalaeontology, with some reference to geomorphology, archaeology, anthropology and palynology. It should however be noted that all criteria have never been reported from one site, and neither are they all found in one single deposit. Thus, the lack of one or more proxies should not be taken as unique evidence to refute the tsunamigenic origin of a specific deposit. Although geochemical signatures have long been used as indicators for palaeosalinity in sedimentary sequences, there appears to have been some reluctance to use them to help in the identification of historical and palaeotsunami deposits. Like other proxies, geochemistry alone may not provide a definite answer to the origin of a deposit. Furthermore, poor preservation due to environmental conditions or as a result of post-diagenetic processes, might complicate the interpretation of geochemical signatures left by tsunami inundation. Similar taphonomic problems are also faced for microfossil proxies. However, geochemistry provides another piece to the puzzle, and together with other proxies, it can help identify palaeotsunami deposits. Geochemical signatures can also provide clues about the landward limit of runup of a tsunami, beyond the area of sediment deposition. This was recently documented following the 2004 IOT and the 2009 South Pacific tsunami. A summary of examples of geochemical signatures recorded in interstitial water and sediment of recent, historical and palaeotsunami deposits is presented.
Oligocene Fluvio-Deltaic Depositional Environments Salin Sub-Basin, Central Myanmar
NASA Astrophysics Data System (ADS)
Gough, A.; Hall, R.
2017-12-01
A recent increase in accessibility for research in Myanmar has allowed rapid advancements in the understanding of the geology of the country. Evolving depositional environments can be reconstructed in largely unstudied Oligocene deposits of the Salin sub-basin, of the Central Myanmar Basin. Data has been collected through a fieldwork campaign to target well-exposed sediments along the western margin of the basin. The studied outcrops span approximately one hundred kilometres from north to south, and a series of sedimentary logs, palaeocurrent data, 2D panel diagrams, and samples for petrographical analysis have been collected and interpreted. The Oligocene formations studied include the Shwezetaw, Paduang, and Okhmintaung, each of which show a broadly southwards-trending fluvio-deltaic environment of deposition. Towards the north, the lower Rupelian Shwezetaw Formation comprises thick fluviatile sandstones which grade southwards through macrotidal-dominated fluvio-deltaic interbedded siltstones and rare sandstones, into marine sandstones. Overlying this, the upper Rupelian Paduang Formation grades rapidly from rare fluvial sandstones towards the north of the basin into deltaic and marine interbedded sandstones and siltstones to the south. This formation is more marine in nature, suggesting a minor transgression throughout the lower Oligocene. By the time of deposition of the Okhmintaung Formation in the Chattian the observed deposits solely represent a tidally-influenced deltaic depositional environment, with very little temporal variation, suggesting a stable sea level. Despite the relatively unchanging depositional environment, the formations are approximately 4000 m thick, suggesting that sedimentation kept pace with relatively rapid subsidence. This current study, which will combine depositional environment reconstruction, provenance, and sediment routing analysis, will provide important insights into both the tectonic setting and the huge sediment accumulation
Granite-related Yangjiashan tungsten deposit, southern China
NASA Astrophysics Data System (ADS)
Xie, Guiqing; Mao, Jingwen; Li, Wei; Fu, Bin; Zhang, Zhiyuan
2018-04-01
The Yangjiashan scheelite-bearing deposit (38,663 metric tons of WO3 with an average ore grade of 0.70% WO3) is hosted in quartz veins in a biotite monzogranite intrusion and surrounding slate in the Xiangzhong Metallogenic Province of southern China. The monzogranite has a zircon SHRIMP U-Pb age of 406.6 ± 2.8 Ma (2σ, n = 20, MSWD = 1.4). Cassiterite coexisting with scheelite yields a weighted mean 206Pb/238U age of 409.8 ± 5.9 Ma (2σ, n = 30, MSWD = 0.20), and molybdenite intergrown with scheelite yields a weighted mean Re-Os age of 404.2 ± 3.2 Ma (2σ, n = 3, MSWD = 0.10). These results suggest that the Yangjiashan tungsten deposit is temporally related to the Devonian intrusion. The δD and calculated δ18OH2O values of quartz intergrown with scheelite range from - 87 to - 68‰, and - 1.2 to 3.4‰, respectively. Sulfides have a narrow range of δ34S values of - 2.9 to - 0.7‰ with an average value of - 1.6‰ (n = 16). The integration of geological, stable isotope, and geochronological data, combined with the quartz-muscovite greisen style of ore, supports a magmatic-hydrothermal origin for the tungsten mineralization. Compared to the more common tungsten skarn, quartz-wolframite vein, and porphyry tungsten deposits, as well as orogenic gold deposits worldwide, the Yangjiashan tungsten deposit is an unusual example of a granite-related, gold-poor, scheelite-bearing quartz vein type of deposit. The calcium needed for the formation of scheelite is derived from the sericitization of calcic plagioclase in the monzogranite and Ca-bearing psammitic country rocks, and the relatively high pH, reduced and Ca-rich mineralizing fluid may be the main reasons for the formation of scheelite rather than wolframite at Yangjiashan.
Differences in Nutrient Adequacy among Poor and Non-Poor Children.
ERIC Educational Resources Information Center
Cook, John T.; Martin, Katie S.
This study compared the proportion of 1- to 5-year-olds in poor and non-poor households whose intakes of key nutrients were inadequate. Data were obtained from the 1986 United States Department of Agriculture Nationwide Food Consumption Survey and Continuing Survey of Food Intakes by Individuals. An intake below 70 percent of the Recommended Daily…
Reconstructing Tsunami Flow Speed from Sedimentary Deposits
NASA Astrophysics Data System (ADS)
Jaffe, B. E.; Gelfenbaum, G. R.
2014-12-01
Paleotsunami deposits contain information about the flow that created them that can be used to reconstruct tsunami flow speed and thereby improving assessment of tsunami hazard. We applied an inverse tsunami sediment transport model to sandy deposits near Sendai Airport, Japan, that formed during the 11 March 2011 Tohoku-oki tsunami to test model performance and explore the spatial variations in tsunami flow speed. The inverse model assumes the amount of suspended sediment in the water column is in equilibrium with local flow speed and that sediment transport convergences, primarily from bedload transport, do not contribute significantly to formation of the portion of the deposit we identify as formed by sediment settling out of suspension. We interpret massive or inversely graded intervals as forming from sediment transport convergences and do not model them. Sediment falling out of suspension forms a specific type of normal grading, termed 'suspension' grading, where the entire grain size distribution shifts to finer sizes higher up in a deposit. Suspension grading is often observed in deposits of high-energy flows, including turbidity currents and tsunamis. The inverse model calculates tsunami flow speed from the thickness and bulk grain size of a suspension-graded interval. We identified 24 suspension-graded intervals from 7 trenches located near the Sendai Airport from ~250-1350 m inland from the shoreline. Flow speeds were highest ~500 m from the shoreline, landward of the forested sand dunes where the tsunami encountered lower roughness in a low-lying area as it traveled downslope. Modeled tsunami flow speeds range from 2.2 to 9.0 m/s. Tsunami flow speeds are sensitive to roughness, which is unfortunately poorly constrained. Flow speed calculated by the inverse model was similar to those calculated from video taken from a helicopter about 1-2 km inland. Deposit reconstructions of suspension-graded intervals reproduced observed upward shifts in grain size
Heat-Flux Sensor For Hot Engine Cylinders
NASA Technical Reports Server (NTRS)
Kim, Walter S.; Barrows, Richard F.; Smith, Floyd A.; Koch, John
1989-01-01
Heat-flux sensor includes buried wire thermocouple and thin-film surface thermocouple, made of platinum and platinum with 13 percent rhodium. Sensor intended for use in ceramic-insulated, low-heat-rejection diesel engine at temperatures of about 1,000 K. Thermocouple junction resists environment in cylinder of advanced high-temperature diesel engine created by depositing overlapping films of Pt and 0.87 Pt/0.13 Rh on iron plug. Plug also contains internal thermocouple.
NASA Astrophysics Data System (ADS)
Christianson, E. M.; Keeler, G. J.; Landis, M. S.
2008-12-01
Mercury (Hg) is a bioaccumulative neurotoxin that has been shown to enter water bodies, and consequently the food chain, via atmospheric deposition to the earth's surface. Anthropogenic emissions of the pollutant play a significant role in contributing to the atmospheric pool of Hg, but the near filed impact from point source on surface deposition has been poorly defined to date. An intensive study during July-September 2006 established eight networked precipitation collection sites in northeastern Ohio, U.S.A., located at varying proximities to coal combustion facilities to evaluate the spatial scale of Hg wet deposition concentration enhancement about the sources. It was found that an average of 42% of the Hg wet deposited at sites in the immediate vicinity (<1 km) of coal fired utilities could be attributed to that adjacent source. Several meteorological variables were shown to account for the degree to which Hg concentration in precipitation was enhanced. A detailed meteorological analysis of the individual precipitation events as well as overall implications of local deposition gradients will be discussed.
Aizawa, Sen-Ichi; Tsubosaka, Soshi
2016-01-01
The optically active mixed-ligand fac(S)-tris(thiolato)rhodium(III) complexes, ΔL -fac(S)-[Rh(aet)2 (L-cys-N,S)](-) (aet = 2-aminoethanethiolate, L-cys = L-cysteinate) () and ΔLL -fac(S)-[Rh(aet)(L-cys-N,S)2 ](2-) were newly prepared by the equatorial preference of the carboxyl group in the coordinated L-cys ligand. The amide formation reaction of with 1,10-diaminodecane and polyallylamine gave the diamine-bridged dinuclear Rh(III) complex and the single-chain polymer-supported Rh(III) complex with retention of the ΔL configuration of , respectively. These Rh(III) complexes reacted with Co(III) or Co(II) to give the linear-type trinuclear structure with the S-bridged Co(III) center and the two Δ-Rh(III) terminal moieties. The polymer-supported Rh(III) complex was applied not only to the CD spectropolarimetric detection and determination of a trace of precious metal ions such as Au(III), Pt(II), and Pd(II) but also to concentration and extraction of these metal ions into the solid polymer phase. Chirality 28:85-91, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.
Atmospherically deposited contaminants in the Sierra Nevada mountains of California have been implicated as adversely affecting amphibians and fish, yet the distributions of contaminants within the mountains are poorly known, particularly at high elevation. We tested the hypothe...
Atmospherically deposited contaminants in the Sierra Nevada mountains of California have been implicated as a factor adversely affecting biological resources such as amphibians and fish, yet the distributions of contaminants within the mountains are poorly known, particularly at...
Do Uric Acid Deposits in Zooxanthellae Function as Eye-Spots?
Yamashita, Hiroshi; Kobiyama, Atsushi; Koike, Kazuhiko
2009-01-01
The symbiosis between zooxanthellae (dinoflagellate genus Symbiodinium) and corals is a fundamental basis of tropical marine ecosystems. However the physiological interactions of the hosts and symbionts are poorly understood. Recently, intracellular crystalline deposits in Symbiodinium were revealed to be uric acid functioning for nutrient storage. This is the first exploration of these enigmatic crystalline materials that had previously been misidentified as oxalic acid, providing new insights into the nutritional strategies of Symbiodinium in oligotrophic tropical waters. However, we believe these deposits also function as eye-spots on the basis of light and electron microscopic observations of motile cells of cultured Symbiodinium. The cells possessed crystalline deposit clusters in rows with each row 100–150 nm thick corresponding to 1/4 the wavelength of light and making them suitable for maximum wave interference and reflection of light. Crystalline clusters in cells observed with a light microscope strongly refracted and polarized light, and reflected or absorbed short wavelength light. The facts that purines, including uric acid, have been identified as the main constituents of light reflectors in many organisms, and that the photoreceptor protein, opsin, was detected in our Symbiodinium strain, support the idea that uric acid deposits in Symbiodinium motile cells may function as a component of an eye-spot. PMID:19609449
Do uric acid deposits in zooxanthellae function as eye-spots?
Yamashita, Hiroshi; Kobiyama, Atsushi; Koike, Kazuhiko
2009-07-17
The symbiosis between zooxanthellae (dinoflagellate genus Symbiodinium) and corals is a fundamental basis of tropical marine ecosystems. However the physiological interactions of the hosts and symbionts are poorly understood. Recently, intracellular crystalline deposits in Symbiodinium were revealed to be uric acid functioning for nutrient storage. This is the first exploration of these enigmatic crystalline materials that had previously been misidentified as oxalic acid, providing new insights into the nutritional strategies of Symbiodinium in oligotrophic tropical waters. However, we believe these deposits also function as eye-spots on the basis of light and electron microscopic observations of motile cells of cultured Symbiodinium. The cells possessed crystalline deposit clusters in rows with each row 100-150 nm thick corresponding to 1/4 the wavelength of light and making them suitable for maximum wave interference and reflection of light. Crystalline clusters in cells observed with a light microscope strongly refracted and polarized light, and reflected or absorbed short wavelength light. The facts that purines, including uric acid, have been identified as the main constituents of light reflectors in many organisms, and that the photoreceptor protein, opsin, was detected in our Symbiodinium strain, support the idea that uric acid deposits in Symbiodinium motile cells may function as a component of an eye-spot.
Ion-substituted calcium phosphate coatings deposited by plasma-assisted techniques: A review.
Graziani, Gabriela; Bianchi, Michele; Sassoni, Enrico; Russo, Alessandro; Marcacci, Maurilio
2017-05-01
One of the main critical aspects behind the failure or success of an implant resides in its ability to fast bond with the surrounding bone. To boost osseointegration, the ideal implant material should exhibit composition and structure similar to those of biological apatite. To this aim, the most common approach is to coat the implant surface with a coating of hydroxyapatite (HA), resembling the main component of mineralized tissues. However, bone apatite is a non-stoichiometric, multi-substituted poorly-crystalline apatite, containing significant amounts of foreign ions, with high biological relevance. Ion-substituted HAs can be deposited by so called "wet methods", which are however poorly reproducible and hardly industrially feasible; at the same time bioactive coatings realized by plasma assisted method, interesting for industrial applications, are generally made of stoichiometric (i.e. un-substituted) HA. In this work, the literature concerning plasma-assisted deposition methods used to deposit ion-substituted HA was reviewed and the last advances in this field discussed. The ions taken into exam are those present in mineralized tissues and possibly having biological relevance. Notably, literature about this topic is scarce, especially relating to in vivo animal and clinical trials; further on, available studies evaluate the performance of substituted coatings from different points of view (mechanical properties, bone growth, coating dissolution, etc.) which hinders a proper evaluation of the real efficacy of ion-doped HA in promoting bone regeneration, compared to stoichiometric HA. Moreover, results obtained for plasma sprayed coatings (which is the only method currently employed for deposition at the industrial scale) were collected and compared to those of novel plasma-assisted techniques, that are expected to overcome its limitations. Data so far available on the topic were discussed to highlight advantages, limitations and possible perspectives of these
Poor Smokers, Poor Quitters, and Cigarette Tax Regressivity
Remler, Dahlia K.
2004-01-01
The traditional view that excise taxes are regressive has been challenged. I document the history of the term regressive tax, show that traditional definitions have always found cigarette taxes to be regressive, and illustrate the implications of the greater price responsiveness observed among the poor. I explain the different definitions of tax burden: accounting, welfare-based willingness to pay, and welfare-based time inconsistent. Progressivity (equity across income groups) is sensitive to the way in which tax burden is assessed. Analysis of horizontal equity (fairness within a given income group) shows that cigarette taxes heavily burden poor smokers who do not quit, no matter how tax burden is assessed. PMID:14759931
Croft, M.G.
1972-01-01
trending anticlines and synclines. The C clay, of Pleistocene age, is a fine-grained lacustrine or paludal deposit occurring 220-300 feet beneath Tulare Lake bed and parts of Fresno Slough. The beds consist of bluish-gray silty clay. Structural contours indicate that the C clay has been extensively warped and folded. The A clay of Pleistocene and Holocene (?) age is a fine-grained lacustrine or paludal deposit occurring 10-60 feet beneath Buena Vista, Kern, and Tulare Lake beds, and parts of Fresno Slough. The clay is mainly blue or dark greenish gray, plastic, and highly organic. In some areas the unit is separated into an upper and a lower stratum by several feet of sand. A radiocarbon date of 26,780 ? 600 years was obtained from wood cored 3 feet beneath the clay. Continental deposits are arkosic beds of late Pliocene and Pleistocene (?) age and were derived from the Sierra Nevada, Tehachapi, and San Emigdio Mountains. In places, a reduced-oxidized contact transgresses the deposits derived from the Sierra Nevada. The reduced deposits consist of moderately permeable bluish-green or bluish-gray fine to medium sand, silt, and clay. The oxidized deposits consist mainly of poorly permeable yellowish-brown silt and fine sand. Deposits derived from the Tehachapi and the San Emigdio Mountains consist of poorly to moderately permeable yellowish-brown sand and silt. Continental and alluvial deposits of Tertiary and Quaternary age that were derived from the Coast Ranges consist mainly of poorly to moderately permeable yellowish-brown gravel, sand, silt, and clay. They include the Tulare Formation and overlying alluvial deposits. Alluvium is composed of coarse arkosic deposits derived from the Sierra Nevada, Tehachapi, and San Emigdio Mountains. A reduced-oxidized contact also transgresses the alluvial deposits derived from the Sierra Nevada. The oxidized deposits consist of poorly to highly permeable yellowish-brown gravel, sand, silt, and clay. The reduc
De novo immune complex deposition in kidney allografts: a series of 32 patients.
Lloyd, Isaac E; Ahmed, Faris; Revelo, Monica P; Khalighi, Mazdak A
2018-01-01
Immune complex deposition in kidney allografts can include both recurrent and de novo processes. Recurrent glomerulonephritis is a well-recognized phenomenon and has been shown to be a common cause of allograft failure. De novo immune complex-mediated disease remains relatively poorly characterized, likely owing to the less frequent use of immunofluorescence and electron microscopy in the transplant setting. We performed a retrospective review of kidney allograft biopsies showing glomerular immune complex deposition. Cases with de novo deposits were identified and further organized into two groups depending on whether the immune complex deposition could be clinically and/or histologically classified. Thirty-two patients with de novo immune complex deposition were identified over a 7-year period. A broad range of immune complex-mediated injuries were observed, the majority (63%) of which could be readily classified either clinically or histologically. These included cases of membranous glomerulonephropathy, IgA nephropathy, infection-related glomerulonephritis and glomerulonephritis related to an underlying autoimmune process. A smaller subset of patients (37%) demonstrated immune complex deposition that was difficult to histologically or clinically classify. These patients typically showed mild mesangial immune complex deposition with co-dominant IgG and IgM staining by immunofluorescence microscopy. The presence of concurrent antibody-mediated rejection and donor-specific antibody positivity was significantly higher in the unclassifiable group. The significance of these deposits and their possible relationship to allograft rejection deserves further investigation. Copyright © 2017 Elsevier Inc. All rights reserved.
NASA Technical Reports Server (NTRS)
Rampino, M. R.; Ernstson, K.; Anguita, F.; Claudin F.
1997-01-01
Proximal ejecta deposits related to three large terrestrial impacts, the 14.8-Ma Ries impact structure in Germany (the Bunte Breccia), the 65-Ma Chicxulub impact structure in the Yucatan (the Albion and Pook's Hill Diamictites in Belize) and the mid-Tertiary Azuara impact structure in Spain (the Pelarda Fm.) occur in the form of widespread debris-flow deposits most likely originating from ballistic processes. These impact-related diamictites typically are poorly sorted, containing grain sizes from clay to large boulders and blocks, and commonly display evidence of mass flow, including preferred orientation of long axes of clasts, class imbrication, flow noses, plugs and pods of coarse debris, and internal shear planes. Clasts of various lithologies show faceting, various degrees of rounding, striations (including nailhead striae), crescentic chattermarks, mirror-like polish, percussion marks, pitting, and penetration features. Considering the impact history of the Earth, it is surprising that so few ballistic ejecta, deposits have been discovered, unless the preservation potential is extremely low, or such materials exist but have been overlooked or misidentified as other types of geologic deposits . Debris-flow diamictites of various kinds have been reported in the geologic record, but these are commonly attributed to glaciation based on the coarse and poorly sorted nature of the deposits and, in many cases, on the presence of clasts showing features considered diagnostic of glacial action, including striations of various kinds, polish, and pitting. These diamictites are the primary evidence for ancient ice ages. We present evidence of the surface features on clasts from known proximal ejecta debris-flow deposits and compare these features with those reported in diamictites. interpreted as ancient glacial deposits (tillites). Our purpose is to document the types of features seen on clasts in diamictites of ejecta origin in order to help in the interpretation of
Decomposing the gap in childhood undernutrition between poor and non-poor in urban India, 2005-06.
Kumar, Abhishek; Singh, Aditya
2013-01-01
Despite the growing evidence from other developing countries, intra-urban inequality in childhood undernutrition is poorly researched in India. Additionally, the factors contributing to the poor/non-poor gap in childhood undernutrition have not been explored. This study aims to quantify the contribution of factors that explain the poor/non-poor gap in underweight, stunting, and wasting among children aged less than five years in urban India. We used cross-sectional data from the third round of the National Family Health Survey conducted during 2005-06. Descriptive statistics were used to understand the gap in childhood undernutrition between the urban poor and non-poor, and across the selected covariates. Blinder-Oaxaca decomposition technique was used to explain the factors contributing to the average gap in undernutrition between poor and non-poor children in urban India. Considerable proportions of urban children were found to be underweight (33%), stunted (40%), and wasted (17%) in 2005-06. The undernutrition gap between the poor and non-poor was stark in urban India. For all the three indicators, the main contributing factors were underutilization of health care services, poor body mass index of the mothers, and lower level of parental education among those living in poverty. The findings indicate that children belonging to poor households are undernourished due to limited use of health care services, poor health of mothers, and poor educational status of their parents. Based on the findings the study suggests that improving the public services such as basic health care and the education level of the mothers among urban poor can ameliorate the negative impact of poverty on childhood undernutrition.
A novel Mo-W interlayer approach for CVD diamond deposition on steel
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kundrát, Vojtěch; Sullivan, John; Ye, Haitao, E-mail: h.ye@aston.ac.uk
Steel is the most widely used material in engineering for its cost/performance ratio and coatings are routinely applied on its surface to further improve its properties. Diamond coated steel parts are an option for many demanding industrial applications through prolonging the lifetime of steel parts, enhancement of tool performance as well as the reduction of wear rates. Direct deposition of diamond on steel using conventional chemical vapour deposition (CVD) processes is known to give poor results due to the preferential formation of amorphous carbon on iron, nickel and other elements as well as stresses induced from the significant difference inmore » the thermal expansion coefficients of those materials. This article reports a novel approach of deposition of nanocrystalline diamond coatings on high-speed steel (M42) substrates using a multi-structured molybdenum (Mo) – tungsten (W) interlayer to form steel/Mo/Mo-W/W/diamond sandwich structures which overcome the adhesion problem related to direct magnetron sputtering deposition of pure tungsten. Surface, interface and tribology properties were evaluated to understand the role of such an interlayer structure. The multi-structured Mo-W interlayer has been proven to improve the adhesion between diamond films and steel substrates by acting as an effective diffusion barrier during the CVD diamond deposition.« less
A novel Mo-W interlayer approach for CVD diamond deposition on steel
NASA Astrophysics Data System (ADS)
Kundrát, Vojtěch; Zhang, Xiaoling; Cooke, Kevin; Sun, Hailin; Sullivan, John; Ye, Haitao
2015-04-01
Steel is the most widely used material in engineering for its cost/performance ratio and coatings are routinely applied on its surface to further improve its properties. Diamond coated steel parts are an option for many demanding industrial applications through prolonging the lifetime of steel parts, enhancement of tool performance as well as the reduction of wear rates. Direct deposition of diamond on steel using conventional chemical vapour deposition (CVD) processes is known to give poor results due to the preferential formation of amorphous carbon on iron, nickel and other elements as well as stresses induced from the significant difference in the thermal expansion coefficients of those materials. This article reports a novel approach of deposition of nanocrystalline diamond coatings on high-speed steel (M42) substrates using a multi-structured molybdenum (Mo) - tungsten (W) interlayer to form steel/Mo/Mo-W/W/diamond sandwich structures which overcome the adhesion problem related to direct magnetron sputtering deposition of pure tungsten. Surface, interface and tribology properties were evaluated to understand the role of such an interlayer structure. The multi-structured Mo-W interlayer has been proven to improve the adhesion between diamond films and steel substrates by acting as an effective diffusion barrier during the CVD diamond deposition.
Gómez-Gutiérrez, Claudia M; Luque, P A; Castro-Beltran, A; Vilchis-Nestor, A R; Lugo-Medina, Eder; Carrillo-Castillo, A; Quevedo-Lopez, M A; Olivas, A
2015-01-01
In this work, the influence of substrate on the morphology of ZnS thin films by chemical bath deposition is studied. The materials used were zinc acetate, tri-sodium citrate, thiourea, and ammonium hydroxide/ammonium chloride solution. The growth of ZnS thin films on different substrates showed a large variation on the surface, presenting a poor growth on SiO2 and HfO2 substrates. The thin films on ITO substrate presented a uniform and compact growth without pinholes. The optical properties showed a transmittance of about 85% in the visible range of 300-800 nm with band gap of 3.7 eV. © Wiley Periodicals, Inc.
Groves, David I.; Goldfarb, Richard J.; Santosh, M.
2016-01-01
In contrast to their province scale similarities, the different giant gold deposit styles show contrasting critical controls at the district to deposit scale. For orogenic gold deposits, the giants appear to have formed by conjunction of a greater number of parameters to those that control smaller deposits, with resultant geometrical and lithostratigraphic complexity as a guide to their location. There are few giant IRGS due to their inferior fluid-flux systems relative to orogenic gold deposits, and those few giants are essentially preservational exceptions. Many Carlin-type deposits are giants due to the exceptional conjunction of both structural and lithological parameters that caused reactive and permeable rocks, enriched in syngenetic gold, to be located below an impermeable cap along antiformal “trends”. Hydrocarbons probably played an important role in concentrating metal. The supergiant Post-Betze deposit has additional ore zones in strain heterogeneities surrounding the pre-gold Goldstrike stock. All unequivocal IOCG deposits are giant or near-giant deposits in terms of gold-equivalent resources, partly due to economic factors for this relatively poorly understood, low Cu-Au grade deposit type. The supergiant Olympic Dam deposit, the most shallowly formed deposit among the larger IOCGs, probably owes its origin to eruption of volatile-rich hybrid magma at surface, with formation of a large maar and intense and widespread brecciation, alteration and Cu-Au-U deposition in a huge rock volume.
Variation of the hydraulic properties within gravity-driven deposits in basinal carbonates
NASA Astrophysics Data System (ADS)
Jablonska, D.; Zambrano, M.; Emanuele, T.; Di Celma, C.
2017-12-01
Deepwater gravity-driven deposits represent important stratigraphic heterogeneities within basinal sedimentary successions. A poor understanding of their distribution, internal architecture (at meso- and micro-scale) and hydraulic properties (porosity and permeability), may lead to unexpected compartmentalization issues in reservoir analysis. In this study, we examine gravity-driven deposits within the basinal-carbonate Maiolica Formation adjacent to the Apulian Carbonate Plaftorm, southern Italy. Maiolica formation is represented by horizontal layers of thin-bedded cherty pelagic limestones often intercalated by mass-transport deposits (slumps, debris-flow deposits) and calcarenites of diverse thickness (0.1 m - 40 m) and lateral extent (100 m - >500 m). Locally, gravity-driven deposits compose up to 60 % of the exposed succession. These deposits display broad array of internal architectures (from faulted and folded strata to conglomerates) and various texture. In order to further constrain the variation of the internal architectures and fracture distribution within gravity-driven deposits, field sedimentological and structural analyses were performed. To examine the texture and hydraulic properties of various lithofacies, the laboratory porosity measurements of suitable rock samples were undertaken. These data were supported by 3D pore network quantitative analysis of X-ray Computed microtomography (MicroCT) images performed at resolutions 1.25 and 2.0 microns. This analysis helped to describe the pores and grains geometrical and morphological properties (such as size, shape, specific surface area) and the hydraulic properties (porosity and permeability) of various lithofacies. The integration of the analyses allowed us to show how the internal architecture and the hydraulic properties vary in different types of gravity-driven deposits within the basinal carbonate succession.
Poor Schools, Poor Students, Successful Teachers
ERIC Educational Resources Information Center
Gehrke, Rebecca Swanson
2005-01-01
Today, one out of four American children attends school in an urban district; one out of every six American children lives in poverty; and, in urban schools where most of the students are poor, two-thirds or more of the children fail to reach even the "basic" level of achievement on national tests. Urban schools are where most states face the…
Code of Federal Regulations, 2010 CFR
2010-04-01
... amount fixed by the Office under the regulations in this part shall deposit any negotiable securities... deposited; conditions of deposit; acceptance of deposits. 703.207 Section 703.207 Employees' Benefits... AND RELATED STATUTES INSURANCE REGULATIONS Insurance Carrier Security Deposit Requirements § 703.207...
NASA Astrophysics Data System (ADS)
Evans, Guy N.; Tivey, Margaret K.; Seewald, Jeffrey S.; Wheat, C. Geoff
2017-10-01
This study investigates the morphology, mineralogy, and geochemistry of seafloor massive sulfide (SMS) deposits from six back-arc hydrothermal vent fields along the Eastern Lau Spreading Center (ELSC) and Valu Fa Ridge (VFR) in the context of endmember vent fluid chemistry and proximity to the Tonga Subduction Zone. To complement deposit geochemistry, vent fluid analyses of Cu, Zn, Ba, Pb and H2,(aq) were completed to supplement existing data and enable thermodynamic calculations of mineral saturation states at in situ conditions. Results document southward increases in the abundance of mantle-incompatible elements in hydrothermal fluids (Ba and Pb) and SMS deposits (Ba, Pb, As, and Sb), which is also expressed in the abundance of barite (BaSO4) and galena (PbS) in SMS deposits. These increases correspond to a decrease in distance between the ELSC/VFR and the Tonga Subduction Zone that correlates with a change in crustal lithology from back-arc basin basalt in the north to mixed andesite, rhyolite, and dacite in the south. Barite influences deposit morphology, contributing to the formation of horizontal flanges and squat terraces. Results are also consistent with a regional-scale lowering of hydrothermal reaction zone temperatures from north to south (except at the southernmost Mariner vent field) that leads to lower-temperature, higher-pH vent fluids relative to mid-ocean ridges of similar spreading rates (Mottl et al., 2011). These fluids are Cu- and Zn-poor and the deposits formed from these fluids are Cu-poor but Zn-rich. In contrast, at the Mariner vent field, higher-temperature and lower pH vent fluids are hypothesized to result from higher reaction zone temperatures and the localized addition of acidic magmatic volatiles (Mottl et al., 2011). The Mariner fluids are Cu- and Zn-rich and vent from SMS deposits that are rich in Cu but poor in Zn with moderate amounts of Pb. Thermodynamic calculations indicate that the contrasting metal contents of vent fluids
Optimal control of build height utilizing optical profilometry in cold spray deposits
NASA Astrophysics Data System (ADS)
Chakraborty, Abhijit; Shishkin, Sergey; Birnkrant, Michael J.
2017-04-01
Part-to-part variability and poor part quality due to failure to maintain geometric specifications pose a challenge for adopting Additive Manufacturing (AM) as a viable manufacturing process. In recent years, In-process Monitoring and Control (InPMC) has received a lot of attention as an approach to overcome these obstacles. The ability to sense geometry of the deposited layers accurately enables effective process monitoring and control of AM application. This paper demonstrates an application of geometry sensing technique for the coating deposition Cold Spray process, where solid powders are accelerated through a nozzle, collides with the substrate and adheres to it. Often the deposited surface has shape irregularities. This paper proposes an approach to suppress the iregularities by controlling the deposition height. An analytical control-oriented model is developed that expresses the resulting height of deposit as an integral function of nozzle velocity and angle. In order to obtain height information at each layer, a Micro-Epsilon laser line scanner was used for surface profiling after each deposition. This surface profile information, specifically the layer height, was then fed back to an optimal control algorithm which manipulated the nozzle speed to control the layer height to a pre specified height. While the problem is heavily nonlinear, we were able to transform it into equivalent Optimal Control problem linear w.r.t. input. That enabled development of two solution methods: one is fast and approximate, while another is more accurate but still efficient.
Li, Xiaobao; Chopp, David L.; Russin, William A.; Brannon, Paul T.; Parsek, Matthew R.
2016-01-01
Microbial biofilms and mineral precipitation commonly co-occur in engineered water systems, such as cooling towers and water purification systems, and both decrease process performance. Microbial biofilms are extremely challenging to control and eradicate. We previously showed that in situ biomineralization and the precipitation and deposition of abiotic particles occur simultaneously in biofilms under oversaturated conditions. Both processes could potentially alter the essential properties of biofilms, including susceptibility to biocides. However, the specific interactions between mineral formation and biofilm processes remain poorly understood. Here we show that the susceptibility of biofilms to chlorination depends specifically on internal transport processes mediated by biomineralization and the accumulation of abiotic mineral deposits. Using injections of the fluorescent tracer Cy5, we show that Pseudomonas aeruginosa biofilms are more permeable to solutes after in situ calcite biomineralization and are less permeable after the deposition of abiotically precipitated calcite particles. We further show that biofilms are more susceptible to chlorine killing after biomineralization and less susceptible after particle deposition. Based on these observations, we found a strong correlation between enhanced solute transport and chlorine killing in biofilms, indicating that biomineralization and particle deposition regulate biofilm susceptibility by altering biocide penetration into the biofilm. The distinct effects of in situ biomineralization and particle deposition on biocide killing highlight the importance of understanding the mechanisms and patterns of biomineralization and scale formation to achieve successful biofilm control. PMID:26944848
Decomposing the Gap in Childhood Undernutrition between Poor and Non–Poor in Urban India, 2005–06
Kumar, Abhishek; Singh, Aditya
2013-01-01
Background Despite the growing evidence from other developing countries, intra-urban inequality in childhood undernutrition is poorly researched in India. Additionally, the factors contributing to the poor/non-poor gap in childhood undernutrition have not been explored. This study aims to quantify the contribution of factors that explain the poor/non-poor gap in underweight, stunting, and wasting among children aged less than five years in urban India. Methods We used cross-sectional data from the third round of the National Family Health Survey conducted during 2005–06. Descriptive statistics were used to understand the gap in childhood undernutrition between the urban poor and non-poor, and across the selected covariates. Blinder–Oaxaca decomposition technique was used to explain the factors contributing to the average gap in undernutrition between poor and non-poor children in urban India. Result Considerable proportions of urban children were found to be underweight (33%), stunted (40%), and wasted (17%) in 2005–06. The undernutrition gap between the poor and non-poor was stark in urban India. For all the three indicators, the main contributing factors were underutilization of health care services, poor body mass index of the mothers, and lower level of parental education among those living in poverty. Conclusions The findings indicate that children belonging to poor households are undernourished due to limited use of health care services, poor health of mothers, and poor educational status of their parents. Based on the findings the study suggests that improving the public services such as basic health care and the education level of the mothers among urban poor can ameliorate the negative impact of poverty on childhood undernutrition. PMID:23734231
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.
Atmospheric Deposition of Indium in the Northeastern United States: Flux and Historical Trends.
White, Sarah Jane O; Keach, Carrie; Hemond, Harold F
2015-11-03
The metal indium is an example of an increasingly important material used in electronics and new energy technologies, whose environmental behavior and toxicity are poorly understood despite increasing evidence of detrimental health impacts and human-induced releases to the environment. In the present work, the history of indium deposition from the atmosphere is reconstructed from its depositional record in an ombrotrophic bog in Massachusetts. A novel freeze-coring technique is used to overcome coring difficulties posed by woody roots and peat compressibility, enabling retrieval of relatively undisturbed peat cores dating back more than a century. Results indicate that long-range atmospheric transport is a significant pathway for the transport of indium, with peak concentrations of 69 ppb and peak fluxes of 1.9 ng/cm2/yr. Atmospheric deposition to the bog began increasing in the late 1800s/early 1900s, and peaked in the early 1970s. A comparison of deposition data with industrial production and emissions estimates suggests that both coal combustion and the smelting of lead, zinc, copper, and tin sulfides are sources of indium to the atmosphere in this region. Deposition appears to have decreased considerably since the 1970s, potentially a visible effect of particulate emissions controls instated in North America during that decade.
Sedimentary deposits study of the 2006 Java tsunami, in Pangandaran, West Java (preliminary result)
DOE Office of Scientific and Technical Information (OSTI.GOV)
Maemunah, Imun, E-mail: imun-m2001@yahoo.com; Institute Technology of Bandung; Suparka, Emmy, E-mail: emmy@gc.itb.ac.id
The 2006 Java Earthquake (Mw 7.2) has generated a tsunami that reached Pangandaran coastal plain with 9.7 m above sea level height of wave. In 2014 we examined the tsunami deposit exposed in shallow trenches along a∼300 m at 5 transect from shoreline to inland on Karapyak and Madasari, Pangandaran. We documented stratigraphically and sedimentologically, the characteristics of Java Tsunami deposit on Karapyak and Madasari and compared both sediments. In local farmland a moderately-sorted, brown soil is buried by a poorly-sorted, grey, medium-grained sand-sheet. The tsunami deposit was distinguished from the underlying soil by a pronounced increase in grain size that becomesmore » finner upwards and landwards. Decreasing concentration of coarse size particles with distance toward inland are in agreement with grain size analysis. The thickest tsunami deposit is about 25 cm found at 84 m from shoreline in Madasari and about 15 cm found at 80 m from shoreline in Karapyak. The thickness of tsunami deposits in some transect become thinner landward but in some other transect lack a consistent suggested strongly affected by local topography. Tsunami deposits at Karapyak and Madasari show many similarities. Both deposits consist of coarse sand that sharply overlies a finer sandy soil. The presence mud drapes and other sedimentary structure like graded bedding, massive beds, mud clasts in many locations shows a dynamics process of tsunami waves. The imbrication coarse and shell fragments of the 2006 Java, tsunami deposits also provide information about the curent direction, allowing us to distinguish run up deposits from backwash deposits.« less
Cobalt—Styles of deposits and the search for primary deposits
Hitzman, Murray W.; Bookstrom, Arthur A.; Slack, John F.; Zientek, Michael L.
2017-11-30
Cobalt (Co) is a potentially critical mineral. The vast majority of cobalt is a byproduct of copper and (or) nickel production. Cobalt is increasingly used in magnets and rechargeable batteries. More than 50 percent of primary cobalt production is from the Central African Copperbelt. The Central African Copperbelt is the only sedimentary rock-hosted stratiform copper district that contains significant cobalt. Its presence may indicate significant mafic-ultramafic rocks in the local basement. The balance of primary cobalt production is from magmatic nickel-copper and nickel laterite deposits. Cobalt is present in several carbonate-hosted lead-zinc and copper districts. It is also variably present in Besshi-type volcanogenic massive sulfide and siliciclastic sedimentary rock-hosted deposits in back arc and rift environments associated with mafic-ultramafic rocks. Metasedimentary cobalt-copper-gold deposits (such as Blackbird, Idaho), iron oxide-copper-gold deposits, and the five-element vein deposits (such as Cobalt, Ontario) contain different amounts of cobalt. None of these deposit types show direct links to mafic-ultramafic rocks; the deposits may result from crustal-scale hydrothermal systems capable of leaching and transporting cobalt from great depths. Hydrothermal deposits associated with ultramafic rocks, typified by the Bou Azzer district of Morocco, represent another type of primary cobalt deposit.In the United States, exploration for cobalt deposits may focus on magmatic nickel-copper deposits in the Archean and Proterozoic rocks of the Midwest and the east coast (Pennsylvania) and younger mafic rocks in southeastern and southern Alaska; also, possibly basement rocks in southeastern Missouri. Other potential exploration targets include—The Belt-Purcell basin of British Columbia (Canada), Idaho, Montana, and Washington for different styles of sedimentary rock-hosted cobalt deposits;Besshi-type VMS deposits, such as the Greens Creek (Alaska) deposit and
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ferraudi, G.; Muralidharan, S.
1983-04-01
The ultraviolet photochemistry of the rhodium(II) phthalocyanines Rh(ph)(CH/sub 3/OH)X with X = Cl/sup -/, Br/sup -/, and I/sup -/ was investigated at different wavelengths. The same action spectrum for the photoinduced hydrogen abstraction was obtained for the three compounds. The photonic energy of the excitation is degraded in part by emission at short wavelengths, e.g. lambda/sub max/ approx. = 420 nm. Such a violet emission, observed with phthalocyanines of Al(III), Rh(III), Co(III), and Ru(II), has been attributed to the relaxation of an upper /sup 3/par. deltapar. delta* excited state. The emissions spectra at 77 K exhibited vibronic components with amore » separation between successive peaks ..delta nu.. approx. = 1.3 x 10/sup 3/ cm/sup -1/. A comparison between the excitation and action spectra shows the difference in the paths that populate the reactive npar. delta* and upper emissive par. deltapar. delta* states. An investigation of the time dependence of the upper /sup 3/par. deltapar. delta* emission and lowest /sup 3/par. deltapar. delta* absorptions reveals the participation of triplet sublevels in the degradation of the excitation energy. The relationship between photoemissive and photoreactive states is discussed.« less
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ferraudi, G.; Muralidharan, S.
1983-01-01
The ultraviolet photochemistry of the rhodium(III) phthalocyanines Rh(ph)(CH/sub 3/OH)X with X = Cl/sup -/, Br/sup -/, and I/sup -/ was investigated at different wavelengths. The same action spectrum for the photoinduced hydrogen abstraction was obtained for the three compounds. The photonic energy of the excitation is degraded in part by emission at short wavelengths, e.g. lambda/sub max/ approx. = 420 nm. Such a violet emission, observed with phthalocyanines of Al(III), Rh(III), Co(III), and Ru(II), has been attributed to the relaxation of an upper /sup 3/pipi* excited state. The emission spectra at 77 K exhibited vibronic components with a separation betweenmore » successive peaks ..delta..v approx. = 1.3 x 10/sup 3/ cm/sup -1/. A comparison between the excitation and action spectra shows the difference in the paths that populate the reactive npi* and upper emissive pipi* states. An investigation of the time dependence of the upper /sup 3/pipi* emission and lowest /sup 3/pipi* absorptions reveals the participation of triplet sublevels in the degradation of the excitation energy. The relationship between photoemissive and photoreactive states is discussed. 40 references, 6 figures, 2 tables.« less
NASA Astrophysics Data System (ADS)
Eriksson, P. G.
A widely developed, thin, coarse-matrix conglomerate occurs within early Proterozoic lacustrine mudrocks in the Transvaal Sequence, South Africa. The poorly sorted tabular chert clasts, alternation of a planar clast fabric with disorientated zones, plus normal and inverse grading in the former rock type suggest deposition by density-modified grain-flow and high density turbidity currents. The lower fan-delta slope palæenvironment inferred for the conglomerate is consistent with the lacustrine interpretation for the enclosing mudrock facies. This intracratonic setting contrasts with the marine environment generally associated with density-modified grain-flow deposits.
NASA Astrophysics Data System (ADS)
Ali, Mubarak; Hamzah, Esah; Ali, Nouman
Titanium nitride (TiN) widely used as hard coating material was coated on tool steels, namely on high-speed steel (HSS) and D2 tool steel by physical vapor deposition method. The goal of this study was to examine the effect of ion etching with and without titanium (Ti) and chromium (Cr) on the adhesion strength of TiN coatings deposited on tool steels. From the scratch tester, it was observed that by increasing Ti ion etching showed an increase in adhesion strength of the deposited coatings. The coatings deposited with Cr ion etching showed poor adhesion compared with the coatings deposited with Ti ion etching. Scratch test measurements showed that the coating deposited with titanium ion etching for 16 min is the most stable coating and maintained even at the critical load of 66 N. The curve obtained via penetration depth along the scratch trace is linear in the case of HSS, whereas is slightly flexible in the case of D2 tool steel. The coatings deposited on HSS exhibit better adhesion compared with those on D2 tool steel.
Self-Organization of Polymer Brush Layers in a Poor Solvent
NASA Astrophysics Data System (ADS)
Karim, A.; Tsukruk, V. V.; Douglas, J. F.; Satija, S. K.; Fetters, L. J.; Reneker, D. H.; Foster, M. D.
1995-10-01
Synthesis of densely grafted polymer brushes from good solvent polymer solutions is difficult when the surface interaction is only weakly attractive because of the strong steric repulsion between the polymer chains. To circumvent this difficulty we graft polymer layers in a poor solvent to exploit attractive polymer-polymer interactions which largely nullify the repulsive steric interactions. This simple strategy gives rise to densely grafted and homogeneous polymer brush layers. Model end-grafted polystyrene chains (M_w = 105,000) are prepared in the poor solvent cyclohexane (9.5 °C) where the chains are chemically attached to the surface utilizing a trichlorosilane end-group. Polished silicon wafers were then exposed to the reactive polymer solutions for a series of “induction times” tau_I and the evolving layer was characterized by X-ray reflectivity and atomic force microscopy. Distinct morphologies were found depending on tau_I. For short tau_I, corresponding to a grafting density less than 5 mg/m^2, the grafted layer forms an inhomogeneous island-like structure. At intermediate tau_I, where the coverage becomes percolating, a surface pattern develops which appears similar to spinodal decomposition in bulk solution. Finally, after sufficiently long tau_I, a dense and nearly homogeneous layer with a sharp interface is formed which does not exhibit surface pattern formation. The stages of brush growth are discussed qualitatively in terms of a random deposition model.
Nitrogen emission and deposition budget in West and Central Africa
NASA Astrophysics Data System (ADS)
Galy-Lacaux, C.; Delon, C.
2014-12-01
Atmospheric nitrogen depends on land surface exchanges of nitrogen compounds. In Sub Saharan Africa, deposition and emission fluxes of nitrogen compounds are poorly quantified, and are likely to increase in the near future due to land use change and anthropogenic pressure. This work proposes an estimate of atmospheric N compounds budget in West and Central Africa, along an ecosystem transect, from dry savanna to wet savanna and forest, for years 2000-2007. The budget may be considered as a one point in time budget, to be included in long term studies as one of the first reference point for Sub Saharan Africa. Gaseous dry deposition fluxes are estimated by considering N compounds concentrations measured in the frame of the IDAF network (IGAC/DEBITS/AFrica) at the monthly scale and modeling of deposition velocities at the IDAF sites, taking into account the bi directional exchange of ammonia. Particulate dry deposition fluxes are calculated using the same inferential method. Wet deposition fluxes are calculated from measurements of ammonium and nitrate chemical content in precipitations at the IDAF sites combined with the annual rainfall amount. In terms of emission, biogenic NO emissions are simulated at each IDAF site with a surface model coupled to an emission module elaborated from an artificial neural network equation. Ammonia emissions from volatilization are calculated from literature data on livestock quantity in each country and N content in manure. NOx and NH3 emission from biomass burning and domestic fires are estimated from satellite data and emission factors. The total budget shows that emission sources of nitrogen compounds are in equilibrium with deposition fluxes in dry and wet savannas, with respectively 7.40 (±1.90) deposited and 9.01 (±3.44) kgN ha-1 yr-1 emitted in dry savanna, 8.38 (±2.04) kgN ha-1 yr-1 deposited and 9.60 (±0.69) kgN ha-1 yr-1 emitted in wet savanna. In forested ecosystems, the total budget is dominated by wet plus dry
Measurement of emission and deposition patterns of ammonia from urine in grass swards
NASA Astrophysics Data System (ADS)
Ross, C. A.; Jarvis, S. C.
Currently, legislation is being considered to reduce NH3 emissions in the UK. The major sources of NH3 and their relative contributions are well known, however, the processes that control the rates of emission are still poorly defined. A series of wind-tunnel experiments has been carried out to determine the effects of various management practices on NH3 losses. The tunnels were modified to enable NH3 emission and subsequent deposition to the adjacent swards in the field to be measured. The wind-tunnels were used to examine the effects of herbage length, cutting and N status on rates of NH3 fluxes, which together with the prevailing environmental conditions affected the rates of NH3 emission and deposition. Results showed that between 20 and 60% of the NH3 emitted was deposited within 2 m. Compensation points of between 1.0 and 2.3 μg m-3 were calculated for the grass sward.
Mild oxidation of methane to methanol or acetic acid on supported isolated rhodium catalysts
NASA Astrophysics Data System (ADS)
Shan, Junjun; Li, Mengwei; Allard, Lawrence F.; Lee, Sungsik; Flytzani-Stephanopoulos, Maria
2017-11-01
An efficient and direct method of catalytic conversion of methane to liquid methanol and other oxygenates would be of considerable practical value. However, it remains an unsolved problem in catalysis, as typically it involves expensive or corrosive oxidants or reaction media that are not amenable to commercialization. Although methane can be directly converted to methanol using molecular oxygen under mild conditions in the gas phase, the process is either stoichiometric (and therefore requires a water extraction step) or is too slow and low-yielding to be practical. Methane could, in principle, also be transformed through direct oxidative carbonylation to acetic acid, which is commercially obtained through methane steam reforming, methanol synthesis, and subsequent methanol carbonylation on homogeneous catalysts. However, an effective catalyst for the direct carbonylation of methane to acetic acid, which might enable the economical small-scale utilization of natural gas that is currently flared or stranded, has not yet been reported. Here we show that mononuclear rhodium species, anchored on a zeolite or titanium dioxide support suspended in aqueous solution, catalyse the direct conversion of methane to methanol and acetic acid, using oxygen and carbon monoxide under mild conditions. We find that the two products form through independent pathways, which allows us to tune the conversion: three-hour-long batch-reactor tests conducted at 150 degrees Celsius, using either the zeolite-supported or the titanium-dioxide-supported catalyst, yield around 22,000 micromoles of acetic acid per gram of catalyst, or around 230 micromoles of methanol per gram of catalyst, respectively, with selectivities of 60-100 per cent. We anticipate that these unusually high activities, despite still being too low for commercial application, may guide the development of optimized catalysts and practical processes for the direct conversion of methane to methanol, acetic acid and other useful
Mild oxidation of methane to methanol or acetic acid on supported isolated rhodium catalysts
DOE Office of Scientific and Technical Information (OSTI.GOV)
Shan, Junjun; Li, Mengwei; Allard, Lawrence F.
An efficient and direct method of catalytic conversion of methane to liquid methanol and other oxygenates would be of considerable practical value. However, it remains an unsolved problem in catalysis, as typically it involves expensive or corrosive oxidants or reaction media(5-8) that are not amenable to commercialization. Although methane can be directly converted to methanol using molecular oxygen under mild conditions in the gas phase, the process is either stoichiometric (and therefore requires a water extraction step) or is too slow and low-yielding to be practical. Methane could, in principle, also be transformed through direct oxidative carbonylation to acetic acid,more » which is commercially obtained through methane steam reforming, methanol synthesis, and subsequent methanol carbonylation on homogeneous catalysts. However, an effective catalyst for the direct carbonylation of methane to acetic acid, which might enable the economical small-scale utilization of natural gas that is currently flared or stranded, has not yet been reported. Here we show that mononuclear rhodium species, anchored on a zeolite or titanium dioxide support suspended in aqueous solution, catalyse the direct conversion of methane to methanol and acetic acid, using oxygen and carbon monoxide under mild conditions. Here, we find that the two products form through independent pathways, which allows us to tune the conversion: three-hour-long batch-reactor tests conducted at 150 degrees Celsius, using either the zeolitesupported or the titanium-dioxide-supported catalyst, yield around 22,000 micromoles of acetic acid per gram of catalyst, or around 230 micromoles of methanol per gram of catalyst, respectively, with selectivities of 60-100 per cent. Finally, we anticipate that these unusually high activities, despite still being too low for commercial application, may guide the development of optimized catalysts and practical processes for the direct conversion of methane to methanol
Mild oxidation of methane to methanol or acetic acid on supported isolated rhodium catalysts
Shan, Junjun; Li, Mengwei; Allard, Lawrence F.; ...
2017-11-30
An efficient and direct method of catalytic conversion of methane to liquid methanol and other oxygenates would be of considerable practical value. However, it remains an unsolved problem in catalysis, as typically it involves expensive or corrosive oxidants or reaction media(5-8) that are not amenable to commercialization. Although methane can be directly converted to methanol using molecular oxygen under mild conditions in the gas phase, the process is either stoichiometric (and therefore requires a water extraction step) or is too slow and low-yielding to be practical. Methane could, in principle, also be transformed through direct oxidative carbonylation to acetic acid,more » which is commercially obtained through methane steam reforming, methanol synthesis, and subsequent methanol carbonylation on homogeneous catalysts. However, an effective catalyst for the direct carbonylation of methane to acetic acid, which might enable the economical small-scale utilization of natural gas that is currently flared or stranded, has not yet been reported. Here we show that mononuclear rhodium species, anchored on a zeolite or titanium dioxide support suspended in aqueous solution, catalyse the direct conversion of methane to methanol and acetic acid, using oxygen and carbon monoxide under mild conditions. Here, we find that the two products form through independent pathways, which allows us to tune the conversion: three-hour-long batch-reactor tests conducted at 150 degrees Celsius, using either the zeolitesupported or the titanium-dioxide-supported catalyst, yield around 22,000 micromoles of acetic acid per gram of catalyst, or around 230 micromoles of methanol per gram of catalyst, respectively, with selectivities of 60-100 per cent. Finally, we anticipate that these unusually high activities, despite still being too low for commercial application, may guide the development of optimized catalysts and practical processes for the direct conversion of methane to methanol
Towards ab initio extremely metal-poor stars
NASA Astrophysics Data System (ADS)
Ritter, Jeremy S.; Safranek-Shrader, Chalence; Milosavljević, Miloš; Bromm, Volker
2016-12-01
Extremely metal-poor stars have been the focus of much recent attention owing to the expectation that their chemical abundances can shed light on the metal and dust yields of the earliest supernovae. We present our most realistic simulation to date of the astrophysical pathway to the first metal-enriched stars. We simulate the radiative and supernova hydrodynamic feedback of a 60 M⊙ Population III star starting from cosmological initial conditions realizing Gaussian density fluctuations. We follow the gravitational hydrodynamics of the supernova remnant at high spatial resolution through its freely expanding, adiabatic, and radiative phases, until gas, now metal-enriched, has resumed runaway gravitational collapse. Our findings are surprising: while the Population III progenitor exploded with a low energy of 1051 erg and injected an ample metal mass of 6 M⊙, the first cloud to collapse after the supernova explosion is a dense surviving primordial cloud on which the supernova blast wave deposited metals only superficially, in a thin, unresolved layer. The first metal-enriched stars can form at a very low metallicity, of only 2-5 × 10-4 Z⊙, and can inherit the parent cloud's highly elliptical, radially extended orbit in the dark matter gravitational potential.
NASA Technical Reports Server (NTRS)
Kohl, F. J.
1982-01-01
The methodology to predict deposit evolution (deposition rate and subsequent flow of liquid deposits) as a function of fuel and air impurity content and relevant aerodynamic parameters for turbine airfoils is developed in this research. The spectrum of deposition conditions encountered in gas turbine operations includes the mechanisms of vapor deposition, small particle deposition with thermophoresis, and larger particle deposition with inertial effects. The focus is on using a simplified version of the comprehensive multicomponent vapor diffusion formalism to make deposition predictions for: (1) simple geometry collectors; and (2) gas turbine blade shapes, including both developing laminar and turbulent boundary layers. For the gas turbine blade the insights developed in previous programs are being combined with heat and mass transfer coefficient calculations using the STAN 5 boundary layer code to predict vapor deposition rates and corresponding liquid layer thicknesses on turbine blades. A computer program is being written which utilizes the local values of the calculated deposition rate and skin friction to calculate the increment in liquid condensate layer growth along a collector surface.
1987-04-01
security deposit action is described in the regulation as follows: h. Security Deposits (DACF and DACA ). (1) Issue. PCS moves create financial hardships...General Wickham, The Army Chief of Staff, specified a philosophy toward the family in the Army Family White Paper. General Wickham’s action was in...security deposits arose. 1 The Army’s action to the issue of security deposits will be thoroughly discussed in this paper. The Army’s action comes now
DOE Office of Scientific and Technical Information (OSTI.GOV)
Yavuz, H.H.; Oercen, S.
1988-08-01
The continental and shallow marine clastics and carbonates exposed around the towns of Kale and Acipayam in southwestern Anatolia were investigated to interpret the depositional environments in the northern margin of the Mediterranean in terms of lithofacies and biozones. These deposits include Miogypsina intermedia and M. irregularis, indicating Burdigalian age when correlated with the same species in the different parts of the Tethys Sea and Indian-Pacific Oceans. The clastic lower part of the succession is characterized by sheet flow and braided-stream deposits of an alluvial-fan/fan-delta complex. Marine carbonates overlie these deposits, but in some places a transgressive lag deposit liesmore » between the unconformity surface and the carbonates. The lag deposit unit corresponds to the Gastropoda biozone, including Ostrea, Terebralia, and Pecten. Four carbonate facies are recognized: (1) Clayey limestones with ahermatypic corals, ostracods, macrofossils, and foraminifers. This facies corresponds to the Textularia-Rotalia biozone. (2) Packstones and grainstones with abundant nearshore and some offshore foraminifers, corresponding to the Miliolidae biozone. (3) Packstones and wackestones with offshore foraminifers. This facies includes the Miogypsina irregularis-Miogypsina intermedia biozone. (4) Boundstones and very poorly sorted reef-talus conglomerates including hermatypic corals, foraminifers, and binding foraminifers. This facies is the coral biozone. These sediments define the northern extent of the Tethys Sea in the investigated area during the Burdigalian. They were deposited in a shallow carbonate platform at the southern margin of the Anatolian mainland, which had a steep coast characterized by an alluvial-fan/fan-delta complex.« less
Reviews and new metallogenic models of mineral deposits in South China: An introduction
NASA Astrophysics Data System (ADS)
Hu, Rui-Zhong; Chen, Wei Terry; Xu, De-Ru; Zhou, Mei-Fu
2017-04-01
In South China, the Yangtze and Cathaysia blocks were welded together along the Jiangnan Fold Belt during Neoproterozoic time (∼830 Ma). Large-scale mineralization in these two blocks occurred from Proterozoic to Cenozoic, making the region one of the most important polymetallic metallogenic provinces in the world. Of particular importance are world-class deposits of iron-oxide copper gold (IOCG), sediment-hosted Mn-P-Al-(Ni, Mo, PGE), syenite-carbonatite-related REE, felsic intrusion-related Sn-W-Mo-Cu-Fe-Pb-Zn, mafic intrusion-related V-Ti-Fe and Cu-Ni-PGE and low-temperature hydrothermal Pb, Zn, Au, and Sb (Fig. 1). In addition, the Ta-Nb, Hg, As, Tl and U deposits in South China are among the world largest of these kinds. Because of these deposits, South China has been a focus of researches for many years. Publications before 2005 were mostly restricted in Chinese. In the past decade, some case studies on some world-class deposits in South China are available in international journals. These recent studies have advanced our understanding of their mode of formation. However, some important issues regarding the timing, tectonic setting and mechanisms of metal concentration still remain poorly understood. This special issue brings together some of the latest information on these topics, including major review papers on specific types of mineralization and several papers dealing with some specific deposits in the region. We anticipate that this issue will generate more interests in the studies of mineral deposits in South China. In this introduction, we outline the tectonic framework and associated deposits.
The Olympic Dam copper-uranium-gold deposit, Roxby Downs, South Australia
DOE Office of Scientific and Technical Information (OSTI.GOV)
Roberts, D.E.; Hudson, G.R.T.
1983-08-01
The Olympic Dam copper-uranium-gold deposit appears to be a new type of strata-bound sediment-hosted ore deposit. It is located 650 km north-northwest of Adelaide in South Australia and was discovered in 1975. It has an areal extent exceeding 20 km/sup 2/ with vertical thicknesses of mineralization up to 350 m. The deposit is estimated to contain in excess of 2,000 million metric tons of mineralized material with an average grade of 1.6 percent copper, 0.06 percent uranium oxide, and 0.6 g/metric ton gold. The deposit occurs in the basement beneath 350 m of unmineralized, flat-lying Adelaidean (late Proterozoic) to Cambrianmore » sediments in the Stuart shelf region of South Australia. The host rocks of the deposit are unmetamorphosed and are probably younger than 1,580 m.y. The deposit is spatially related to coincident gravity and magnetic anomalies and the intersection of west-northwest- and north-northwest-trending lineaments. The Proterozoic sediments comprising the local basement sequence are predominantly sedimentary breccias ranging from matrix-poor granite breccias to matrix-rich polymict breccias containing clasts of a variety of rock types. This sequence is over 1 km thick and has been divided into two main units--the Olympic Dam Formation and the Greenfield Formation. The Olympic Dam Formation has five members, three of which are matrix rich. The Greenfield Formation has three members, the lower two being very hematite rich while the upper has a significant volcanic component. Pervasive hematite, chlorite, and sericite alteration of varying intensity affects all the basement sequence.« less
Flohr, M.J.K.; Huebner, J.S.
1992-01-01
Laminated to massive rhodochrosite, hausmannite, and Mn-silicates from the Smith prospect and Manga-Chrome mine, Sierra Nevada, California were deposited as ocean floor sediments associated with chert and shale. The principal lithologies at Smith are chert, argillite, rhodochrosite-, hausmannite- and chlorite-rich layers, and relatively uncommon layers of jacobsite. The Manga-Chrome mine also contains layers rich in manganoan calcite and caryopilite. Tephroite, rhodonite, spessartine, and accessory alleghanyite and sonolite formed during metamorphism. Volcaniclastic components are present at Manga-Chrome as metavolcanic clasts and as Mn-poor, red, garnet- and hematite-rich layers. There is no evidence, such as relict lithologies, that Mn was introduced into Mn-poor lithologies such as chert, limestone or mudstone. Replacement of Mn-poor phases by Mn-rich phases is observed only in the groundmass of volcanic clasts that appear to have fallen into soft Mn-rich mud. Manganiferous samples from the Smith prospect and Manga-Chrome mine have high Mn Fe and low concentrations of Ni, Cu, Zn, Co, U, Th and the rare-earth elements that are similar to concentrations reported from other ancient Mn deposits found in chert-greenstone complexes and from manganiferous sediments and crusts that are forming near modern sea floor vents. The Sierra Nevada deposits formed as precipitates of Mn-rich sediments on the sea floor, probably from mixtures of circulating hydrothermal fluids and seawater. The composition of a metabasalt from the Smith prospect is consistent with those of island-arc tholeiites. Metavolcanic clasts from the Manga-Chrome mine are compositionally distinct from the Smith metabasalt and have alkaline to calc-alkaline affinities. A back-arc basin is considered to be the most likely paleoenvironment for the formation of the Mn-rich lenses at the Manga-Chrome mine and, by association, the Smith prospect. Layers of rhodochrosite, hausmannite and chert preserve the
The El Teniente porphyry Cu-Mo deposit from a hydrothermal rutile perspective
NASA Astrophysics Data System (ADS)
Rabbia, Osvaldo M.; Hernández, Laura B.; French, David H.; King, Robert W.; Ayers, John C.
2009-11-01
Mineralogical, textural, and chemical analyses (EPMA and PIXE) of hydrothermal rutile in the El Teniente porphyry Cu-Mo deposit help to better constrain ore formation processes. Rutile formed from igneous Ti-rich phases (sphene, biotite, Ti-magnetite, and ilmenite) by re-equilibration and/or breakdown under hydrothermal conditions at temperatures ranging between 400°C and 700°C. Most rutile nucleate and grow at the original textural position of its Ti-rich igneous parent mineral phase. The distribution of Mo content in rutile indicates that low-temperature (˜400-550°C), Mo-poor rutile (5.4 ± 1.1 ppm) is dominantly in the Mo-rich mafic wallrocks (high-grade ore), while high-temperature (˜550-700°C), Mo-rich rutile (186 ± 20 ppm) is found in the Mo-poor felsic porphyries (low-grade ore). Rutile from late dacite ring dikes is a notable exception to this distribution pattern. The Sb content in rutile from the high-temperature potassic core of the deposit to its low-temperature propylitic fringe remains relatively constant (35 ± 3 ppm). Temperature and Mo content of the hydrothermal fluids in addition to Mo/Ti ratio, modal abundance and stability of Ti-rich parental phases are key factors constraining Mo content and provenance in high-temperature (≥550°C) rutile. The initial Mo content of parent mineral phases is controlled by melt composition and oxygen fugacity as well as timing and efficiency of fluid-melt separation. Enhanced reduction of SO2-rich fluids and sulfide deposition in the Fe-rich mafic wallrocks influences the low-temperature (≤550°C) rutile chemistry. The data are consistent with a model of fluid circulation of hot (>550°C), oxidized (ƒO2 ≥ NNO + 1.3), SO2-rich and Mo-bearing fluids, likely exsolved from deeper crystallizing parts of the porphyry system and fluxed through the upper dacite porphyries and related structures, with metal deposition dominantly in the Fe-rich mafic wallrocks.
NASA Astrophysics Data System (ADS)
Wang, Z.; Zhang, J.; Jin, Z.
2016-12-01
Cu-Ni sulfide deposit is generally considered partial melt originated from the mantle which is usually PGE-enriched. However, the largest Cu-Ni sulfide deposits of China (the Jinchuan Cu-Ni deposit) is PGE-depleted. Comparing to silicate melt, the nature and topotaxy of sulfide melt have remained poorly understood. Here we report experimental investigation on the topotaxy of sulfide and silicate melts in peridotite using a piston-cylinder press and a 5GPa Griggs-type deformation apparatus. The starting material consists of polycrystalline olivine or pyrolite and 1 wt% Fe-Ni-Cu sulfide. Hydrostatic and deformation experiments were conducted at a pressure of 1.5 GPa and a temperature of 1250°. Under hydrostatic conditions, our results reveal that the apparent dihedral angle of sulfide melt in an olivine matrix( 96°) is much larger than that of silicate + sulfide melt in pyrolite(<60°) under hydrostatic conditions. The sulfide melt pockets appear mostly as blobs in triple junctions with an immiscible Ni-poor center surrounded by a Ni-rich layer. Under deformation conditions, olivine develops pronounced fabrics with the pole of the (010) forming high concentrations approximately normal to the foliation plane and the [100] axes forming a girdle in the foliation plane. EBSD phase mapping analyses reveal strong shape preferred orientations (SPO) of sulfide +silicate melt in the 45, 90, 135 degree directions for deformation experiments indicating complete wetting of grain boundaries and forming a favorable source for ore deposits. Deformation also causes mixing of the Ni-rich and the Ni-poor sulfide melts. As the platinum-group elements(PGE) prefer to concentrate in the Ni-rich sulfide melt at high temperatures, our results suggest that the metallogenetic source of the PGE-depleted Cu-Ni deposits may have formed under relatively intense deformation and low temperatures with a small fraction of mixed sulfide and silicate melts.
Consequences of Growing Up Poor.
ERIC Educational Resources Information Center
Duncan, Greg J., Ed.; Brooks-Gunn, Jeanne, Ed.
The consequences and correlates of growing up poor as well as the mechanisms through which poverty influences children are explored. This book is organized with a primary focus on research findings and a secondary concern with policy implications. The chapters are: (1) "Poor Families, Poor Outcomes: The Well-Being of Children and Youth" (Jeanne…
A 'Scottish Poor Law of Lunacy'? Poor Law, Lunacy Law and Scotland's parochial asylums.
Farquharson, Lauren
2017-03-01
Scotland's parochial asylums are unfamiliar institutional spaces. Representing the concrete manifestation of the collision between two spheres of legislation, the Poor Law and the Lunacy Law, six such asylums were constructed in the latter half of the nineteenth century. These sites expressed the enduring mandate of the Scottish Poor Law 1845 over the domain of 'madness'. They were institutions whose very existence was fashioned at the directive of the local arm of the Poor Law, the parochial board, and they constituted a continuing 'Scottish Poor Law of Lunacy'. Their origins and operation significantly subverted the intentions and objectives of the Lunacy Act 1857, the aim of which had been to institute a public district asylum network with nationwide coverage.
NASA Astrophysics Data System (ADS)
Trofimovs, J.; Cas, R. A. F.; Davis, B. K.
2004-11-01
The Boorara Domain of the Kalgoorlie Terrane, Eastern Goldfields Superterrane, western Australia contains excellent exposure of Archaean felsic and ultramafic breccias characterised by facies associations interpreted to reflect a volcanic debris avalanche mode of deposition. Such Archaean volcanic deposits are typically difficult to identify due to poor preservation and exposure. However, primary volcanological and sedimentological features are preserved within the relatively low strain and low metamorphic grade (up to lower greenschist facies) Boorara Domain that allow accurate facies reconstruction. The breccia deposit is characterised by two clast populations. A 'block facies' comprised of metre- to decimetre-scale megablocks of dacite, basalt and komatiite is preserved within a 'mixed' matrix breccia facies of angular, coarse sand- to boulder-sized clasts. The megablocks preserve original stratigraphy and show fracturing and jigsaw-fit textures within the poorly sorted, unstratified, genetically related matrix. Overlying the volcanic debris avalanche deposit, are a series of stratified horizons. These deposits show evidence of hydraulic sorting within bedforms exhibiting normal grain-size grading and tractional scour and fill structures along their basal contacts. The stratified facies is interpreted to have been deposited by high concentration, high competency turbidity currents, triggered by slope stabilization slides in the source region. Primary contacts and volcanic textures preserved in decimetre-scale volcanic blocks allow reconstruction of the pre-collapse palaeovolcanological history of the source region. The volcanic debris avalanche deposit, together with the associated stratified sedimentary horizons, were produced by sector collapse of a submarine, dacitic volcanic dome. Contemporaneous komatiite intrusion into the dacite dome may have caused dome flank instability. However, the volcanic debris avalanche trigger is interpreted to be a post
Code of Federal Regulations, 2010 CFR
2010-04-01
... AND RELATED STATUTES INSURANCE REGULATIONS Authorization of Self-Insurers § 703.306 Kinds of negotiable securities that may be deposited; conditions of deposit; acceptance of deposits. A self-insurer or a self-insurer applicant electing to deposit negotiable securities to secure its obligations under...
NASA Astrophysics Data System (ADS)
Courel, Maykel; Sanchez, T. G.; Mathews, N. R.; Mathew, X.
2018-03-01
In this work, the processing of Cu2ZnGeS4 (CZGS) thin films by a thermal evaporation technique starting from CuS, GeS and ZnS precursors, and post-deposition thermal processing, is discussed. Batches of films with GeS layers of varying thicknesses are deposited in order to study the role of Ge concentration on the structural, morphological, optical and electrical properties of CZGS films. The formation of the CZGS compound with a tetragonal phase and a kesterite structure is confirmed for all samples using XRD and Raman studies. An improvement in crystallite size for Ge-poor films is also observed in the XRD analysis, which is in good agreement with the grain size observed in the cross section SEM image. Furthermore, it is found that the band-gap of CZGS film can be tailored in the range of 2.0-2.23 eV by varying Ge concentration. A comprehensive electrical characterization is also performed which demonstrates that slightly Ge-poor samples are described by the lowest grain boundary defect densities and the highest photosensitivity and mobility values. A study of the work function of CZGS samples with different Ge concentrations is also presented. Finally, a theoretical evaluation is presented, considering, under ideal conditions, the possible impact of these films on device performance. Based on the characterization results, it is concluded that Ge-poor CZGS samples deposited by thermal evaporation present better physical properties for device applications.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Swihart, G.H.; McBay, E.H.; Smith, D.H.
1992-01-01
Lacustrine evaporite borate deposits span the range from mineralogically unzoned or poorly zoned to concentrically or complexly zoned types. Deposits often contain an inner ulexite or probertite (Na-Ca borates) zone and an outer colemanite (Ca borate) zone. A few deposits contain an innermost borax (Na borate) zone. Boron isotopic analyses of core material from the zoned borax-ulexite-colemanite Kramer deposit have been made with the aim of providing a better understanding of the processes of zone formation. Samples from 6 depths over a 63 foot interval in the borax zone yield a [delta] B-11 range of +0.1 to +2.3 permil. Twomore » samples in the portion of the ulexite zone below the borax zone, vertically separated from one another by 20 feet, yield identical results of [delta]B-11 = [minus]2.1 permit. Three ulexite samples from a 10 foot interval above the borax zone produced results in the range [delta]B-11 = [minus]4.6 to [minus]5.5 permil. A number of possible origins for ulexite at Kramer have been proposed: (1) primary precipitation from the lake brines; (2) postdepositional alteration of the borax zone margin by Ca-rich groundwater; (3) mixing of seeping lake brines and Ca-rich groundwater in muds around the lake. Given the small variation in B isotopic composition exhibited in the borax zone, mechanisms 1 and 2 would produce upper and lower portions of the ulexite zone with similar isotopic compositions. In the third scenario, the difference in composition of the upper and lower ulexites could be due to distance from the lake and relative proportions of seeped lake brine (B-11-rich) and clay adsorbed B (B-10-rich). Furthermore, the cotton ball form of the ulexite in this core is identical to that of ulexite forming today just beneath the surface of dry lakes in NV and CA.« less
Karande, Sunil; Kulkarni, Madhuri
2005-11-01
Education is one of the most important aspects of human resource development. Poor school performance not only results in the child having a low self-esteem, but also causes significant stress to the parents. There are many reasons for children to under perform at school, such as, medical problems, below average intelligence, specific learning disability, attention deficit hyperactivity disorder, emotional problems, poor socio-cultural home environment, psychiatric disorders and even environmental causes. The information provided by the parents, classroom teacher and school counselor about the child's academic difficulties guides the pediatrician to form an initial diagnosis. However, a multidisciplinary evaluation by an ophthalmologist, otolaryngologist, counselor, clinical psychologist, special educator, and child psychiatrist is usually necessary before making the final diagnosis. It is important to find the reason(s) for a child's poor school performance and come up with a treatment plan early so that the child can perform up to full potential.
Nanomechanical properties of platinum thin films synthesized by atomic layer deposition
DOE Office of Scientific and Technical Information (OSTI.GOV)
Mamun, M.A.; Gu, D.; Baumgart, H.
2015-03-01
The nanomechanical properties of Pt thin films grown on Si (100) using atomic layer deposition (ALD) were investigated using nanoindentation. Recently, atomic layer deposition (ALD) has successfully demonstrated the capability to deposit ultra-thin films of platinum (Pt). Using (methylcyclopentadienyl) trimethylplatinum (MeCpPtMe3) as chemical platinum precursor and oxygen (O2) as the oxidizing agent, the ALD synthesis of Pt can be achieved with high conformity and excellent film uniformity. The ALD process window for Pt films was experimentally established in the temperature range between 270 °C and 320 °C, where the sheet conductance was constant over that temperature range, indicating stable ALDmore » Pt film growth rate. ALD growth of Pt films exhibits very poor nucleation and adhesion characteristics on bare Si surfaces when the native oxide was removed by 2% HF etch. Pt adhesion improves for thermally oxidized Si wafers and for Si wafers covered with native oxide. Three ALD Pt films deposited at 800, 900, and 1000 ALD deposition cycles were tested for the structural and mechanical properties. Additionally, the sample with 900 ALD deposition cycles was further annealed in forming gas (95% N2 and 5% H2) at 450 °C for 30 min in order to passivate dangling bonds in the grain boundaries of the polycrystalline Pt film. Cross-sectional transmission electron microscopy (TEM), X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscope (SEM) were employed to characterize the films' surface structure and morphology. Nanoindentation technique was used to evaluate the hardness and modulus of the ALD Pt films of various film thicknesses. The results indicate that the films depict comparable hardness and modulus results; however, the 800 and 1000 ALD deposition cycles films without forming gas annealing experienced significant amount of pileup, whereas the 900 ALD deposition cycles sample annealed in forming gas resulted in a smaller
Broda, Anja; LaPlante, Debi A; Nelson, Sarah E; LaBrie, Richard A; Bosworth, Leslie B; Shaffer, Howard J
2008-01-01
Background In an attempt to reduce harm related to gambling problems, an Internet sports betting service provider, bwin Interactive Entertainment, AG (bwin), imposes limits on the amount of money that users can deposit into their online gambling accounts. We examined the effects of these limits on gambling behavior. Methods We compared (1) gambling behavior of those who exceeded deposit limits with those who did not, and (2) gambling behavior before and after exceeding deposit limits. We analyzed 2 years of the actual sports gambling behavior records of 47000 subscribers to bwin. Results Only 160 (0.3%) exceeded deposit limits at least once. Gamblers who exceeded deposit limits evidenced higher average number of bets per active betting day and higher average size of bets than gamblers who did not exceed deposit limits. Comparing the gambling behavior before and after exceeding deposit limits revealed slightly more unfavorable gambling behavior after exceeding deposit limits. Conclusion Our findings indicate that Internet gamblers who exceed deposit limits constitute a group of bettors willing to take high risks; yet, surprisingly, they appear to do this rather successfully because their percentage of losses is lower than others in the sample. However, some of these gamblers exhibit some poor outcomes. Deposit limits might be necessary harm reduction measures to prevent the loss of extremely large amounts of money and cases of bankruptcy. We discuss how these limits might be modified based on our findings. PMID:18684323
Broda, Anja; LaPlante, Debi A; Nelson, Sarah E; LaBrie, Richard A; Bosworth, Leslie B; Shaffer, Howard J
2008-08-06
In an attempt to reduce harm related to gambling problems, an Internet sports betting service provider, bwin Interactive Entertainment, AG (bwin), imposes limits on the amount of money that users can deposit into their online gambling accounts. We examined the effects of these limits on gambling behavior. We compared (1) gambling behavior of those who exceeded deposit limits with those who did not, and (2) gambling behavior before and after exceeding deposit limits. We analyzed 2 years of the actual sports gambling behavior records of 47000 subscribers to bwin. Only 160 (0.3%) exceeded deposit limits at least once. Gamblers who exceeded deposit limits evidenced higher average number of bets per active betting day and higher average size of bets than gamblers who did not exceed deposit limits. Comparing the gambling behavior before and after exceeding deposit limits revealed slightly more unfavorable gambling behavior after exceeding deposit limits. Our findings indicate that Internet gamblers who exceed deposit limits constitute a group of bettors willing to take high risks; yet, surprisingly, they appear to do this rather successfully because their percentage of losses is lower than others in the sample. However, some of these gamblers exhibit some poor outcomes. Deposit limits might be necessary harm reduction measures to prevent the loss of extremely large amounts of money and cases of bankruptcy. We discuss how these limits might be modified based on our findings.
NASA Astrophysics Data System (ADS)
Cocker, Helen A.; Mauk, Jeffrey L.; Rabone, Stuart D. C.
2013-02-01
The 7.1 Ma Broken Hills adularia-sericite Au-Ag deposit is currently the only producing rhyolite-hosted epithermal deposit in the Hauraki Goldfield of New Zealand. The opaque minerals include pyrite, electrum, acanthite (Ag2S), sphalerite, and galena, which are common in other adularia-sericite epithermal deposits in the Hauraki Goldfield and elsewhere worldwide. Broken Hills ores also contain the less common minerals aguilarite (Ag4SeS), naumannite (Ag2Se), petrovskaite (AuAgS), uytenbogaardtite (Ag3AuS2), fischesserite (Ag3AuSe2), an unnamed silver chloride (Ag2Cl), and unnamed Ag ± Au minerals. Uytenbogaardtite and petrovskaite occur with high-fineness electrum. Broken Hills is the only deposit in the Hauraki Goldfield where uytenbogaardtite and petrovskaite have been identified, and these phases appear to have formed predominantly from unmixing of a precursor high-temperature phase under hypogene conditions. Supergene minerals include covellite, chalcocite, Au-rich electrum, barite, and a variety of iron oxyhydroxide minerals. Uytenbogaardtite can form under supergene and hypogene conditions, and textural relationships between uytenbogaardtite and associated high-fineness electrum may be similar in both conditions. Distinguishing the likely environment of formation rests principally on identification of other supergene minerals and documenting their relationships with uytenbogaardtite. The presence of aguilarite, naumannite, petrovskaite, and fischesserite at Broken Hills reflects a Se-rich mineral assemblage. In the Hauraki Goldfield and the western Great Basin, USA, Se-rich minerals are more abundant in provinces that are characterized by bimodal rhyolite-andesite volcanism, but in other epithermal provinces worldwide, the controls on the occurrences of Se-bearing minerals remain poorly constrained, in spite of the unusually high grades associated with many Se-rich epithermal deposits.
Educational attainment in poor comprehenders
Ricketts, Jessie; Sperring, Rachael; Nation, Kate
2014-01-01
To date, only one study has investigated educational attainment in poor (reading) comprehenders, providing evidence of poor performance on national UK school tests at age 11 years relative to peers (Cain and Oakhill, 2006). In the present study, we adopted a longitudinal approach, tracking attainment on such tests from 11 years to the end of compulsory schooling in the UK (age 16 years). We aimed to investigate the proposal that educational weaknesses (defined as poor performance on national assessments) might become more pronounced over time, as the curriculum places increasing demands on reading comprehension. Participants comprised 15 poor comprehenders and 15 controls; groups were matched for chronological age, nonverbal reasoning ability and decoding skill. Children were identified at age 9 years using standardized measures of nonverbal reasoning, decoding and reading comprehension. These measures, along with a measure of oral vocabulary knowledge, were repeated at age 11 years. Data on educational attainment were collected from all participants (n = 30) at age 11 and from a subgroup (n = 21) at 16 years. Compared to controls, educational attainment in poor comprehenders was lower at ages 11 and 16 years, an effect that was significant at 11 years. When poor comprehenders were compared to national performance levels, they showed significantly lower performance at both time points. Low educational attainment was not evident for all poor comprehenders. Nonetheless, our findings point to a link between reading comprehension difficulties in mid to late childhood and poor educational outcomes at ages 11 and 16 years. At these ages, pupils in the UK are making key transitions: they move from primary to secondary schools at 11, and out of compulsory schooling at 16. PMID:24904464
Gallisai, Rachele; Peters, Francesc; Volpe, Gianluca; Basart, Sara; Baldasano, José Maria
2014-01-01
The surface waters of the Mediterranean Sea are extremely poor in the nutrients necessary for plankton growth. At the same time, the Mediterranean Sea borders with the largest and most active desert areas in the world and the atmosphere over the basin is subject to frequent injections of mineral dust particles. We describe statistical correlations between dust deposition over the Mediterranean Sea and surface chlorophyll concentrations at ecological time scales. Aerosol deposition of Saharan origin may explain 1 to 10% (average 5%) of seasonally detrended chlorophyll variability in the low nutrient-low chlorophyll Mediterranean. Most of the statistically significant correlations are positive with main effects in spring over the Eastern and Central Mediterranean, conforming to a view of dust events fueling needed nutrients to the planktonic community. Some areas show negative effects of dust deposition on chlorophyll, coinciding with regions under a large influence of aerosols from European origin. The influence of dust deposition on chlorophyll dynamics may become larger in future scenarios of increased aridity and shallowing of the mixed layer. PMID:25333783
NASA Astrophysics Data System (ADS)
Akinpelu, Oluwatosin Caleb
The growing need for better definition of flow units and depositional heterogeneities in petroleum reservoirs and aquifers has stimulated a renewed interest in outcrop studies as reservoir analogues in the last two decades. Despite this surge in interest, outcrop studies remain largely two-dimensional; a major limitation to direct application of outcrop knowledge to the three dimensional heterogeneous world of subsurface reservoirs. Behind-outcrop Ground Penetrating Radar (GPR) imaging provides high-resolution geophysical data, which when combined with two dimensional architectural outcrop observation, becomes a powerful interpretation tool. Due to the high resolution, non-destructive and non-invasive nature of the GPR signal, as well as its reflection-amplitude sensitivity to shaly lithologies, three-dimensional outcrop studies combining two dimensional architectural element data and behind-outcrop GPR imaging hold significant promise with the potential to revolutionize outcrop studies the way seismic imaging changed basin analysis. Earlier attempts at GPR imaging on ancient clastic deposits were fraught with difficulties resulting from inappropriate field techniques and subsequent poorly-informed data processing steps. This project documents advances in GPR field methodology, recommends appropriate data collection and processing procedures and validates the value of integrating outcrop-based architectural-element mapping with GPR imaging to obtain three dimensional architectural data from outcrops. Case studies from a variety of clastic deposits: Whirlpool Formation (Niagara Escarpment), Navajo Sandstone (Moab, Utah), Dunvegan Formation (Pink Mountain, British Columbia), Chinle Formation (Southern Utah) and St. Mary River Formation (Alberta) demonstrate the usefulness of this approach for better interpretation of outcrop scale ancient depositional processes and ultimately as a tool for refining existing facies models, as well as a predictive tool for subsurface
Mixture Model for Determination of Shock Equation of State
2012-07-25
not considered in this paper. III. COMPARISON WITH EXPERIMENTAL DATA A. Two-constituent composites 1. Uranium- rhodium composite Uranium- rhodium (U...sound speed, Co, and S were determined from linear least squares fit to the available data22 as shown in Figs. 1(a) and 1(b) for uranium and rhodium ...overpredicts the experimental data, with an average deviation, dUs,/Us of 0.05, shown in Fig. 2(b). The linear fits for uranium and rhodium are shown for
NASA Astrophysics Data System (ADS)
Fug, Frank; Petry, Adrien; Jost, Hendrik; Ahmed, Aisha; Zamanzade, Mohammad; Possart, Wulff
2017-12-01
Thin layers of polyurethane monomers (diol, triol, diisocyanate) are deposited from gas phase onto native aluminium and copper surfaces. According to infrared external reflection absorption spectra both alcohols undergo only weak physical interactions with both metals. The diisocyanate on the other hand reveals resistance against desorption and rich new spectral features indicate strong adhesion. Preparation of urethane layers by sequential deposition of diisocyanate and diol yields urethane linkages. Urethane is formed faster on Cu than on Al. Scanning force microscopy reveals heterogeneous layers with metal dependent morphology. They show poor resistance against tetrahydrofuran rinsing i.e. most part of the formed urethane containing molecules are removed. Nevertheless, a residue of molecules sticks on the metal. It contains strongly adsorbed isocyanates and few isocyanate units which are bonded to diol units via urethane links. Further improvement of the molecular layer deposition is necessary to achieve well-crosslinked polyurethane layers.
NASA Astrophysics Data System (ADS)
Bai, Juan; Xing, Shi-Hui; Zhu, Ying-Ying; Jiang, Jia-Xing; Zeng, Jing-Hui; Chen, Yu
2018-05-01
Rationally tailoring the surface/interface structures of noble metal nanostructures emerges as a highly efficient method for improving their electrocatalytic activity, selectivity, and long-term stability. Recently, hydrogen evolution reaction is attracting more and more attention due to the energy crisis and environment pollution. Herein, we successfully synthesize polyallylamine-functionalized rhodium nanosheet nanoassemblies-carbon nanotube nanohybrids via a facile one-pot hydrothermal method. Three-dimensionally branched rhodium nanosheet nanoassemblies are consisted of two dimensionally atomically thick ultrathin rhodium nanosheets. The as-prepared polyallylamine-functionalized rhodium nanosheet nanoassemblies-carbon nanotube nanohybrids show the excellent electrocatalytic activity for the hydrogen evolution reaction in acidic media, with a low onset reduction potential of -1 mV, a small overpotential of 5 mV at 10 mA cm-2, which is much superior to commercial platinum nanocrystals. Two dimensionally ultrathin morphology of rhodium nanosheet, particular rhodium-polyallylamine interface, and three-dimensionally networks induced by carbon nanotube are the key factors for the excellent hydrogen evolution reaction activity in acidic media.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Yang, Dong; Xu, Pinghong; Browning, Nigel D.
The initial steps of rhodium cluster formation from zeolite-supported mononuclear Rh(C2H4)2 complexes in H2 at 373 K and 1 bar were investigated by infrared and extended X-ray absorption fine structure spectroscopies and scanning transmission electron microscopy (STEM). The data show that ethylene ligands on the rhodium react with H2 to give supported rhodium hydrides and trigger the formation of rhodium clusters. STEM provided the first images of the smallest rhodium clusters (Rh2) and their further conversion into larger clusters. The samples were investigated in a plug-flow reactor as catalysts for the conversion of ethylene + H2 in a molar ratiomore » of 4:1 at 1 bar and 298 K, with the results showing how the changes in catalyst structure affect the activity and selectivity; the rhodium clusters are more active for hydrogenation of ethylene than the single-site complexes, which are more selective for dimerization of ethylene to give butenes« less
ERIC Educational Resources Information Center
Thomas, M. A.
2012-01-01
The shifting ideological winds of foreign aid donors have driven their policy towards governments in poor countries. Donors supported state-led development policies in poor countries from the 1940s to the 1970s; market and private-sector driven reforms during the 1980s and 1990s; and returned their attention to the state with an emphasis on…
Porphyry copper deposit density
Singer, Donald A.; Berger, Vladimir; Menzie, W. David; Berger, Byron R.
2005-01-01
Estimating numbers of undiscovered mineral deposits has been a source of unease among economic geologists yet is a fundamental task in considering future supplies of resources. Estimates can be based on frequencies of deposits per unit of permissive area in control areas around the world in the same way that grade and tonnage frequencies are models of sizes and qualities of undiscovered deposits. To prevent biased estimates it is critical that, for a particular deposit type, these deposit density models be internally consistent with descriptive and grade and tonnage models of the same type. In this analysis only deposits and prospects that are likely to be included in future grade and tonnage models are employed, and deposits that have mineralization or alteration separated by less than an arbitrary but consistent distance—2 km for porphyry copper deposits—are combined into one deposit. Only 286 deposits and prospects that have more than half of the deposit not covered by postmineral rocks, sediments, or ice were counted.Nineteen control areas were selected and outlined along borders of hosting magmatic arc terranes based on three main features: (1) extensive exploration for porphyry copper deposits, (2) definable geologic settings of the porphyry copper deposits in island and continental volcanic-arc subduction-boundary zones, and (3) diversity of epochs of porphyry copper deposit formation.Porphyry copper deposit densities vary from 2 to 128 deposits per 100,000 km2 of exposed permissive rock, and the density histogram is skewed to high values. Ninety percent of the control areas have densities of four or more deposits, 50 percent have densities of 15 or more deposits, and 10 percent have densities of 35 or more deposits per 100,000 km2. Deposit density is not related to age or depth of emplacement. Porphyry copper deposit density is inversely related to the exposed area of permissive rock. The linear regression line and confidence limits constructed with
What controls deposition rate in electron-beam chemical vapor deposition?
White, William B; Rykaczewski, Konrad; Fedorov, Andrei G
2006-08-25
The key physical processes governing electron-beam-assisted chemical vapor deposition are analyzed via a combination of theoretical modeling and supporting experiments. The scaling laws that define growth of the nanoscale deposits are developed and verified using carefully designed experiments of carbon deposition from methane onto a silicon substrate. The results suggest that the chamber-scale continuous transport of the precursor gas is the rate controlling process in electron-beam chemical vapor deposition.
Chiou, Mong-Feng; Jayakumar, Jayachandran; Cheng, Chien-Hong; Chuang, Shih-Ching
2018-06-13
Reaction mechanisms for the synthesis of indenamines, indenols, and isoquinolinium salts through cobalt- and rhodium-catalysis were investigated using density functional theory calculations. We found that the valence charge of transition metals dramatically influences the reaction pathways. Catalytic reactions involving lower-oxidation-state transition metals (M I /M III , M = Co and Rh) generally favor a [3+2] cyclization pathway, whereas those involving higher oxidation states (M III /M V ) proceed through a [4+2] cyclization pathway. A catalytic cycle with novel M III /M V as a crucial species was successfully revealed for isoquinolinium salts synthesis, which highly valent M V was not only encountered in the [RhCp*]-catalysis but also in the [CoCp*]-catalysis.
Carbon nanotubes synthesized by Ni-assisted atmospheric pressure thermal chemical vapor deposition
NASA Astrophysics Data System (ADS)
Choi, G. S.; Cho, Y. S.; Hong, S. Y.; Park, J. B.; Son, K. H.; Kim, D. J.
2002-03-01
A detailed systematic study on the growth morphology of carbon nanotubes (CNTs) on Si in atmospheric pressure thermal chemical vapor deposition was undertaken. The role of NH3 for vertical alignment of CNTs was investigated. The direct cause for the alignment was a dense distribution of the catalytic metal particles, but that the particles are maintained catalytically active under amorphous carbon deposits was established by NH3. It allows a dense nucleation of the CNTs, and consequently, assists vertical alignment through entanglement and mechanical leaning among the tubes. The CNTs grew in a base growth mode. Since Ni is consumed both by silicide reaction and by capture into the growing tube, the growth stops when Ni is totally depleted. It occurs earlier for smaller particles, and thus a long time of growth results in a thin bottom with poor adhesion.
NASA Astrophysics Data System (ADS)
McMurtry, G. M.; Campbell, J. F.; Fryer, G. J.; Tappin, D. R.; Fietzke, J.
2010-12-01
Sandy, basalt-coral conglomerates associated with both beachrock and coral reefs are found at high elevations on Oahu, Hawaii. They have been attributed to either brief, sea level high-stands or storms. The Kahe Point conglomerates are at 12.5 m elevation, whereas the main stage MIS-5e reef at this location has a maximum elevation of 8.2 m. They are loosely consolidated and poorly cemented, graded, poorly sorted, and with varying amounts of basalt and coral clasts ranging from cobble to boulder size. Coral in these deposits has been U-series dated by us at between 120-125 ka (n=5). Four distinct beds, with a gently seaward tilt, are recognized in a road cut section, with each bed composed of a few cm-thick topset bed of fine-grained, shelly, calcareous sand to silt. Similar high elevation conglomerates and 5e reefs are also described at Mokapu and Kaena Points on Oahu, indicating an island-wide deposit. Older coral clasts, dated at 130 to 142 ka (n=6; oldest by alpha spectrometry) found in association with the stage 5e corals suggest reworking and incorporation of older low-stand reef material. The coarse grain size of the conglomerates indicates deposition from a high-energy event; thus a high-stand source is ruled out. We also consider that the overall lithology and up to 0.5 m bed thickness not to be the result of storms; a series of high frequency storm events is considered unlikely. The weight of the evidence in our opinion clearly indicates deposition by a series of tsunami waves. If correct, this has implications for “probabilistic” models of sea level peaks at least 6.6 m higher than present at stage 5e that use such data in their models (e. g., Kopp et al., 2009), at least for Oahu. Within about 2 km of the Kahe deposit, in a road cut at Ko Olina, there is another markedly similar high-energy, sandy basalt-bearing coral conglomerate sequence at 21 to 25 m elevation. There are at least two distinct beds about one meter in thickness, both gently seaward
Artigas, Albert; Pla-Quintana, Anna; Lledó, Agustí; Roglans, Anna; Solà, Miquel
2018-06-04
A novel methodology to transform C60 into a variety of open-cage fullerene derivatives employing rhodium(I) catalysis has been developed. This transformation encompasses a partially intermolecular [2+2+2] cycloaddition reaction between diynes 1 and C60 to deliver a cyclohexadiene-fused fullerene, which concomitantly undergoes a formal [4+4]/retro-[2+2+2] rearrangement to deliver open-cage fullerenes 2. Most notably, this process occurs without the need of photoexcitation. The complete mechanism of this transformation has been rationalized by DFT calculations, which indicate that, after [2+2+2] cycloaddition, the cyclohexadiene-fused intermediate evolves into the final product through a Rh-catalyzed di-π-methane rearrangement followed by a retro-[2+2+2] cycloaddition. The obtained open-cage fullerenes can be derivatized by Suzuki-Miyaura cross-coupling, or subjected to ring expansion to deliver a 12-membered ring orifice in the fullerene structure. Overall, the methodology presented constitutes a straightforward entry to functional open-cage C60-fullerene derivatives employing catalytic methods. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
NASA Astrophysics Data System (ADS)
Valentine, G. A.; Perry, F. V.; WoldeGabriel, G.
2000-12-01
The Oligocene, deeply eroded Summer Coon composite volcano contains mafic andesite deposits that are massive to poorly bedded, have abundant flattened and deformed spatter clasts, have varying proportions of dense lithic clasts, and are supported mostly by a coarse-ash matrix. Although superficially these deposits resemble typical facies from Strombolian eruptions (emplaced ballistically, by fallout, and by rolling and local grain-avalanches down steep cone slopes), there are several lines of evidence that lead to an interpretation that the deposits were emplaced by pyroclastic density currents. These include local coarse-tail grading, deformation of spatter clasts in a down-flow direction, incorporation of matrix ash and lapilli into flattened spatter clasts, imbrication of large clasts, plastering of spatter on stoss sides of large lithic blocks and lenses of lithic-rich material on lee sides, deposition on angles less than the angle of repose, and a paucity of clast shapes associated with Strombolian mechanisms. The deposit characteristics are consistent with rapid sedimentation from a low-particle-concentration, turbulent flow onto an aggrading bed. We infer two potential mechanisms for generating these density currents: (1) explosive magma-water interaction involving lithic debris and relatively unfragmented melt; and (2) collapse of oversteepened upper cone slopes due to rapid accumulation of spatter from voluminous Strombolian eruptions.
Raoult, Vincent; Howell, Nicholas; Zahra, David; Peddemors, Victor M; Howard, Daryl L; de Jonge, Martin D; Buchan, Benjamin L; Williamson, Jane E
2018-01-01
The development of shark vertebrae and the possible drivers of inter- and intra-specific differences in vertebral structure are poorly understood. Shark vertebrae are used to examine life-history traits related to trophic ecology, movement patterns, and the management of fisheries; a better understanding of their development would be beneficial to many fields of research that rely on these calcified structures. This study used Scanning X-ray Fluorescence Microscopy to observe zinc distribution within vertebrae of ten shark species from five different orders. Zinc was mostly localised within the intermedialis and was generally detected at levels an order of magnitude lower in the corpus calcareum. In most species, zinc concentrations were higher pre-birth mark, indicating a high rate of pre-natal zinc deposition. These results suggest there are inter-specific differences in elemental deposition within vertebrae. Since the deposition of zinc is physiologically-driven, these differences suggest that the processes of growth and deposition are potentially different in the intermedialis and corpus calcareum, and that caution should be taken when extrapolating information such as annual growth bands from one structure to the other. Together these results suggest that the high inter-specific variation in vertebral zinc deposition and associated physiologies may explain the varying effectiveness of ageing methodologies applied to elasmobranch vertebrae.
NASA Astrophysics Data System (ADS)
Kumar, Priyank; Bhatt, Nisarg K.; Vyas, Pulastya R.; Gohel, Vinod B.
2016-10-01
The thermophysical properties of rhodium are studied up to melting temperature by incorporating anharmonic effects due to lattice ions and thermally excited electrons. In order to account anharmonic effects due to lattice vibrations, we have employed mean field potential (MFP) approach and for thermally excited electrons Mermin functional. The local form of the pseudopotential with only one effective adjustable parameter rc is used to construct MFP and hence vibrational free energy due to ions - Fion. We have studied equation of state at 300 K and further, to access the applicability of present conjunction scheme, we have also estimated shock-Hugoniot and temperature along principle Hugoniot. We have carried out the study of temperature variation of several thermophysical properties like thermal expansion (βP), enthalpy (EH), specific heats at constant pressure and volume (CP and CV), specific heats due to lattice ions and thermally excited electrons ( and , isothermal and adiabatic bulk moduli (BT and Bs) and thermodynamic Gruneisen parameter (γth) in order to examine the inclusion of anharmonic effects in the present study. The computed results are compared with available experimental results measured by using different methods and previously obtained theoretical results using different theoretical philosophy. Our computed results are in good agreement with experimental findings and for some physical quantities better or comparable with other theoretical results. We conclude that local form of the pseudopotential used accounts s-p-d hybridization properly and found to be transferable at extreme environment without changing the values of the parameter. Thus, even the behavior of transition metals having complexity in electronic structure can be well understood with local pseudopotential without any modification in the potential at extreme environment. Looking to the success of present scheme (MFP + pseudopotential) we would like to extend it further for the
Abdoli, Nasrin; Farnia, Vahid; Delavar, Ali; Esmaeili, Alirez; Dortaj, Fariborz; Farrokhi, Noorali; Karami, Majid; Shakeri, Jalal; Holsboer-Trachsler, Edith; Brand, Serge
2015-01-01
Background In Iran, traffic accidents and deaths from traffic accidents are among the highest in the world, and generally driver behavior rather than either technical failures or environmental conditions are responsible for traffic accidents. In the present study, we explored the extent to which aggressive traits, health status, and sociodemographic variables explain driving behavior among Iranian male traffic offenders. Method A total of 443 male driving offenders (mean age: M =31.40 years, standard deviation =9.56) from Kermanshah (Iran) took part in the study. Participants completed a questionnaire booklet covering sociodemographic variables, traits of aggression, health status, and driving behavior. Results Poor health status, such as symptoms of depression, anxiety, insomnia, and social dysfunction, and also higher levels of trait aggression explained poor driving behavior. Multiple regressions indicated that poor health status, but not aggression, independently predicted poor driving behavior. Conclusion Results suggest that health status concerns are associated with poor driving behavior. Prevention and intervention might therefore focus on drivers reporting poor mental health status. PMID:26316753
Dong, Qiuchen; Huang, Yikun; Song, Donghui; Wu, Huixiang; Cao, Fei; Lei, Yu
2018-07-30
Both pH-sensitive and glucose-responsive rhodium oxide nanocorals (Rh 2 O 3 NCs) were synthesized through electrospinning followed by high-temperature calcination. The as-prepared Rh 2 O 3 NCs were systematically characterized using various advanced techniques including scanning electron microscopy, X-ray powder diffraction and Raman spectroscopy, and then employed as a dual functional nanomaterial to fabricate a dual sensor for both non-enzymatic glucose sensing and solid-state pH monitoring. The sensing performance of the Rh 2 O 3 NCs based dual sensor toward pH and glucose was evaluated using open circuit potential, cyclic voltammetry and amperometric techniques, respectively. The results show that the as-prepared Rh 2 O 3 NCs not only maintain accurate and reversible pH sensitivity of Rh 2 O 3 , but also demonstrate a good electrocatalytic activity toward glucose oxidation in alkaline medium with a sensitivity of 11.46 μA mM -1 cm -2 , a limit of detection of 3.1 μM (S/N = 3), and a reasonable selectivity against various interferents in non-enzymatic glucose detection. Its accuracy in determining glucose in human serum samples was further demonstrated. These features indicate that the as-prepared Rh 2 O 3 NCs hold great promise as a dual-functional sensing material in the development of a high-performance sensor forManjakkal both solid-state pH and non-enzymatic glucose sensing. Copyright © 2018 Elsevier B.V. All rights reserved.
Zeglis, Brian M.; Pierre, Valérie C.; Kaiser, Jens T.; Barton, Jacqueline K.
2009-01-01
Two crystal structures are determined for Δ-Rh(bpy)2(chrysi)3+ (chrysi = 5,6-chrysenequinone diimine) bound to the oligonucleotide duplex 5′-CGGAAATTACCG-3′ containing two adenosine-adenosine mismatches (italics) through metalloinsertion. Diffraction quality crystals with two different space groups (P3221 and P43212) were obtained under very similar crystallization conditions. In both structures, the bulky rhodium complex inserts into the two mismatched sites from the minor groove side, ejecting the mismatched bases into the major groove. The conformational changes are localized to the mismatched site; the metal complex replaces the mismatched base pair without an increase in base pair rise. The expansive metal complex is accommodated in the duplex by a slight opening in the phosphodiester backbone; all sugars retain a C2′-endo puckering, and flanking base pairs neither stretch nor shear. The structures differ, however, in that in one of the structures, an additional metal complex is bound by intercalation from the major groove at the central 5′-AT-3′ step. We conclude that this additional metal complex is intercalated into this central step because of crystal packing forces. The structures described here of Δ-Rh(bpy)2(chrysi)3+ bound to thermodynamically destabilized AA mismatches share critical features with binding by metalloinsertion in two other oligonucleotides containing different single base mismatches. These results underscore the generality of the metalloinsertion as a new mode of non-covalent binding by small molecules with a DNA duplex. PMID:19374348
Development of volume deposition on cast iron by additive manufacturing
DOE Office of Scientific and Technical Information (OSTI.GOV)
Sridharan, Niyanth; Dehoff, Ryan R.; Jordan, Brian H.
2016-11-10
ORNL partnered with Cummins to demonstrate the feasibility of using additive manufacturing techniques to help develop repair techniques for refurbished cast iron engine blocks. Cummins is interested in the refurbished engine business due to the increased cost savings and reduced emissions. It is expected that by refurbishing engines could help reduce the green house gas emissions by as much as 85%. Though such repair techniques are possible in principle there has been no major industry in the automotive sector that has deployed this technology. Therefore phase-1 would seek to evaluate the feasibility of using the laser directed energy deposition techniquemore » to repair cast iron engine blocks. The objective of the phase-1 would be to explore various strategies and understand the challenges involved. During phase-1 deposits were made using Inconel-718, Nickel, Nr-Cr-B braze filler. Inconel 718 builds showed significant cracking in the heat-affected zone in the cast iron. Nickel was used to reduce the cracking in the cast iron substrate, however the Ni builds did not wet the substrate sufficiently resulting in poor dimensional tolerance. In order to increase wetting the Ni was alloyed with the Ni-Cr-B braze to decrease the surface tension of Ni. This however resulted in significant cracks in the build due to shrinkage stresses associated with multiple thermal cycling. Hence to reduce the residual stresses in the builds the DMD-103D equipment was modified and the cast iron block was pre heated using cartridge heaters. Inconel-718 alloyed with Ni was deposited on the engine block. The pre-heated deposits showed a reduced susceptibility to cracking. If awarded the phase-2 of the project would aim to develop process parameters to achieve a crack free deposit engine block.« less
DepositScan, a Scanning Program to Measure Spray Deposition Distributions
USDA-ARS?s Scientific Manuscript database
DepositScan, a scanning program was developed to quickly measure spray deposit distributions on water sensitive papers or Kromekote cards which are widely used for determinations of pesticide spray deposition quality on target areas. The program is installed in a portable computer and works with a ...
Connecting the records: exploiting tephra deposits to help understand abrupt climate change
NASA Astrophysics Data System (ADS)
Davies, S. M.; Abbott, P. M.; Bourne, A. J.; Chapman, M.; Pearce, N. J. G.; Griggs, A. J.; Cook, E.
2016-12-01
The causal mechanism of abrupt climate change during the last glacial period remains a key challenge. Although these events are well-documented in a wide range of proxy records, the triggers and drivers remain poorly understood, largely due to the dating uncertainties that prevent the integration of different archives. Unravelling the lead/lag responses (hence cause and effect) between the Earth's climate components is limited by the challenges of synchronising palaeoclimate records on a common timescale. Here we present the potential and the challenges of optimising the use of cryptotephra deposits to precisely correlate the Greenland ice-cores with North Atlantic marine records. A series of new cryptotephra deposits have been identified in Greenland, increasing the scope of identifying coeval isochrons in the marine environment. This new framework, however, brings new challenges in the search for unique and robust geochemical fingerprints for unequivocal tephra correlations. As such, some tephra deposits are proposed to be more valuable than others and underpin key snapshots in time during the last glacial period. The North Atlantic Ash Zone II, for instance, represents the most widespread isochron and constrains the cooling of GI-15. Some tephra deposits in the ice-core record originate from ultra-distal sources beyond the North Atlantic region and we also explore the potential for establishing North Pacific linkages.
Parenting Efficacy and the Early School Adjustment of Poor and Near-Poor Black Children
ERIC Educational Resources Information Center
Jackson, Aurora P.; Choi, Jeong-Kyun; Bentler, Peter M.
2009-01-01
This short-term longitudinal study investigates whether maternal educational attainment, maternal employment status, and family income affect African American children's behavioral and cognitive functioning over time through their impacts on mothers' psychological functioning and parenting efficacy in a sample of 100 poor and near-poor single…
NASA Astrophysics Data System (ADS)
Young, Grant M.
Paleoproterozoic glaciogenic deposits have a more restricted distribution than those of the Neoproterozoic, which are thought by some to provide evidence that the surface of the entire Earth was frozen (snowball Earth hypothesis). In Laurentia, Paleoproterozoic glacial rocks appear to be associated with the breakup of a supercontinent, whereas in Vaalbara they may form part of the early fill of compressional (foreland?) basins representing ocean closure. The scattered Paleoproterozoic glacial deposits may be approximately contemporaneous but ages are poorly constrained at around 2.3 Ga. Many features ascribed to the existence of a snowball Earth in the Neoproterozoic are not developed in the Paleoproterozoic. For example most of the older glaciogenic successions lack cap carbonates. Major element geochemistry of the post-glacial sedimentary rocks of the Gowganda Formation suggests a weathering trend opposite to that predicted by the SEH. The close association between iron-formations and some glacial deposits in the Neoproterozoic, is virtually absent from the Paleoproterozoic. Thus the Paleoproterozoic glacial successions lack many of the criteria that are supposed to substantiate the snowball Earth hypothesis. These ancient glacial deposits are perhaps more appropriately compared with those of temperate glaciations. Apparent low paleolatitudes derived from some Paleoproterozoic glaciogenic deposits pose a problem for any interpretation of these rocks. Williams suggested that these odd relationships might be explained by a much higher obliquity of the Earth's ecliptic in the Precambrian but resolution of these problems must await additional geochronological and paleomagnetic work.
NASA Astrophysics Data System (ADS)
Chatalov, Athanas
2017-04-01
Glaciomarine deposits of late Hirnantian age in the western part of the Palaeozoic Balkan Terrane have persistent thickness ( 7 m) and lateral uniformity in rock colour, bedding pattern, lithology, and sedimentary structures. Four lithofacies are distinguished from base to top: lonestone-bearing diamictites, interbedded structureless mudstones, crudely laminated diamictites, and finely laminated mudstones. The diamictites are clast-poor to clast-rich comprising muddy to sandy varieties. Their compositional maturity is evidenced by the very high amount of detrital quartz compared to the paucity of feldspar and unstable lithic grains. Other textural components include extraclasts derived from the local Ordovician basement, mudstone intraclasts, and sediment aggregates. Turbate structures, grain lineations, and soft sediment deformation of the matrix below larger grains are locally observed. Sedimentological analysis reveals that deposition occurred in an ice-intermediate to ice-distal, poorly agitated shelf environment by material supplied from meltwater buoyant plumes and rain-out from ice-rafted debris. Remobilization by mass-flow processes (cohesive debris flows and slumps) was an important mechanism particularly for the formation of massive diamictites. The glaciomarine deposits represent a typical deglaciation sequence reflecting retreat of the ice front (grounded or floating ice sheet), relative sea-level rise and gradually reduced sedimentation rate with increasing contribution from suspension fallout. This sequence was deposited on the non-glaciated shelf of the intracratonic North Gondwana platform along the southern margin of the Rheic Ocean. The Hirnantian strata of the Balkan Terrane can be correlated with similar glaciomarine deposits known from peri-Gondwana terranes elsewhere in Europe showing clear 'Armorican affinity'. Several lines of evidence suggest that the provenance of siliciclastic material was associated mainly with sedimentary recycling of
Sullivan, Timothy J.; Lawrence, Gregory B.; Bailey, Scott W.; McDonnell, Todd C.; McPherson, G.T.
2013-01-01
This study documents the effects of acidic deposition and soil acid-base chemistry on the growth, regeneration, and canopy condition of sugar maple (SM) trees in the Adirondack Mountains of New York. Sugar maple is the dominant canopy species throughout much of the northern hardwood forest in the State. A field study was conducted in 2009 in which 50 study plots within 20 small Adirondack watersheds were sampled and evaluated for soil acid-base chemistry and SM growth, canopy condition, and regeneration. Atmospheric sulfur (S) and nitrogen (N) deposition were estimated for each plot. Trees growing on soils with poor acid-base chemistry (low exchangeable calcium and % base saturation) that receive relatively high levels of atmospheric S and N deposition exhibited little to no SM seedling regeneration, decreased canopy condition, and short-to long-term growth declines compared with study plots having better soil condition and lower levels of atmospheric deposition. These results suggest that the ecosystem services provided by SM in the western and central Adirondack Mountain region, including aesthetic, cultural, and monetary values, are at risk from ongoing soil acidification caused in large part by acidic deposition.
Carbonate Deposition on Antarctic Shelves
NASA Astrophysics Data System (ADS)
Frank, T. D.; James, N. P.; Malcolm, I.
2011-12-01
Limestones associated with glaciomarine deposits occur throughout the geologic record but remain poorly understood. The best-described examples formed during major ice ages of the Neoproterozoic and Late Paleozoic. Quaternary analogs on Antarctic shelves have received comparatively little study. Here, we report on the composition, spatial distribution, and stratigraphic context of carbonate sediments contained in piston cores from the Ross Sea. The goals of this work are to (1) document the nature and distribution of carbonate sediments on the Ross Sea continental shelf and (2) examine temporal relationships to Quaternary glaciation. Results will be used to develop criteria that will improve understanding of analogous deposits in the ancient record. All carbonate-rich intervals in piston cores from the Ross Rea, now housed at the Antarctic Marine Geology Research Facility at Florida State University, were examined and described in detail. Sediment samples were disaggregated and sieved into size fractions before description with paleontological analysis carried out on the coarsest size fraction (>250 microns). Carbonate-rich sediments are concentrated in the northwestern Ross Sea, along the distal margins of Mawson and Pennell Banks. Calcareous facies include a spectrum of lithologies that range from fossiliferous mud, sand, and gravel to skeletal floatstone-rudstone and bafflestone. Floatstone-rudstone and bafflestone is most abundant along western-facing slopes in areas protected from the Antarctic Coastal Current. Sand-prone facies dominate the tops of banks and mud-prone, often spicultic, facies occur in deeper areas. The carbonate factory is characterized by a low-diversity, heterozoan assemblage that is dominated by stylasterine hydrocorals, barnacles, and bryozoans. Molluscs and echinoids are present but not abundant. Planktic and benthic foraminifera are ubiquitous components of the sediment matrix, which is locally very rich in sponge spicules. Biota rarely
78 FR 56583 - Deposit Insurance Regulations; Definition of Insured Deposit
Federal Register 2010, 2011, 2012, 2013, 2014
2013-09-13
... as a potential global deposit insurer, preserve confidence in the FDIC deposit insurance system, and... the United States.\\2\\ The FDIC generally pays out deposit insurance on the next business day after a... since 2001 and total approximately $1 trillion today. In many cases, these branches do not engage in...
NASA Astrophysics Data System (ADS)
Zhang, Gai; Tian, Min
2015-04-01
This proposed method regulated the determination of platinum, palladium, ruthenium, rhodium, iridium and gold in platinum-group ores by nickel sulfide fire assay—inductively coupled plasma optical emission spectrometry (ICP-OES) combined with ultrasound extraction for the first time. The quantitative limits were 0.013-0.023μg/g. The samples were fused to separate the platinum-group elements from matrix. The nickel sulfide button was then dissolved with hydrochloric acid and the insoluble platinum-group sulfide residue was dissolved with aqua regia by ultrasound bath and finally determined by ICP-OES. The proposed method has been applied into the determination of platinum-group element and gold in large amounts of ultrabasic rocks from the Great Dyke of Zimbabwe.
NASA Astrophysics Data System (ADS)
Brand, Brittany D.; Bendaña, Sylvana; Self, Stephen; Pollock, Nicholas
2016-07-01
Our ability to interpret the deposits of pyroclastic density currents (PDCs) is critical for understanding the transport and depositional processes that control PDC dynamics. This paper focuses on the influence of slope on flow dynamics and criticality as recorded in PDC deposits from the 18 May 1980 eruption of Mt. St. Helens (USA). PDC deposits are found along the steep flanks (10°-30°) and across the pumice plain ( 5°) up to 8 km north of the volcano. Granulometry, componentry and descriptions of depositional characteristics (e.g., bedform morphology) are recorded with distance from source. The pumice plain deposits are primarily thick (3-12 m), massive and poorly-sorted, and represent deposition from a series of concentrated PDCs. By contrast, the steep flank deposits are stratified to cross-stratified, suggesting deposition from PDCs where turbulence strongly influenced transport and depositional processes. We propose that acceleration of the concentrated PDCs along the steep flanks resulted in thinning of the concentrated, basal region of the current(s). Enhanced entrainment of ambient air, and autofluidization from upward fluxes of air from substrate interstices and plunging breakers across rugged, irregular topography further inflated the currents to the point that the overriding turbulent region strongly influenced transport and depositional mechanisms. Acceleration in combination with partial confinement in slot canyons and high surface roughness would also increase basal shear stress, further promoting shear and traction transport in the basal region of the current. Conditions along the steep flank resulted in supercritical flow, as recorded by regressive bedforms, which gradually transitioned to subcritical flow downstream as the concentrated basal region thickness increased as a function of decreasing slope and flow energy. We also find that (1) PDCs were erosive into the underlying granular substrate along high slopes (> 25°) where currents were
NASA Astrophysics Data System (ADS)
Vinkler, A.; Ort, M. H.; Giordano, G.
2009-12-01
The Villa Senni Eruption Unit (350ka) represents the youngest large caldera-forming eruption of the Colli Albani volcano near Rome (Italy). The Colli Albani magma is marked by very undersaturated chemistry (tephritic to K-foiditic) and low viscosity. The total volume of the Villa Senni Eruption Unit is estimated at > 50 km3 and 30 km3 DRE (Watkins et al., 2002). The unit includes a sequence of a basal fallout/surge deposit, two main ignimbrites emplaced during the same eruptive event, a series of breccia deposits positioned between the two ignimbrites, and a rarely preserved final fallout. The basal surge and fallout sequence may help answer questions regarding the beginning of a large mafic ignimbrite eruption. The entire surge and fallout deposit is 190 cm thick at the caldera wall, consisting of 19 individual, parallel to faintly cross-stratified layers. The deposit distally thins to 25 cm at 18 km east of the caldera and to 2.5 cm at 21 km NW of the caldera. The eruption started with fine ash surges showing cross-stratification at proximal locations and being vesicular distally. The deposit consists mainly of juvenile clasts, which are angular, poorly vesicular, and rich in leucite microlites (~80 µm). Clasts around 100-150 μm show signs of magma-water interaction: quench fracturing: conchoidal and step fractures, smooth surfaces, adhering clasts and melt film. These features are present in several thin alternating surge and fall sequences at the base of the deposit. The lithic clasts in these first deposits are concentrated in layers, indicating pulsatory behavior of the eruption. Upward, the deposit consists of thicker, coarse ash to lapilli fallout layers from more sustained columns. The juvenile clasts in these deposits are more irregular, with higher vesicularity (but less than 50%) and smaller leucite microlites (~60 μm). The uppermost part of the basal fallout/surge deposit shows features transitional to the first large ignimbrite: fallout deposits
McKelvey, V.E.; Cathcart, J.B.; Altschuler, Z.S.; Swanson, R.W.; Lutz, Katherine
1953-01-01
Most of the worlds phosphate deposits can be grouped into six types: 1) igneous apatite deposits; 2) marine phosphorites; 3) residual phosphorites; 4) river pebble deposits; 5) phosphatized rock; and 6) guano. The igneous apatites and marine phosphorites form deposits measurable in millions or billions of tons; the residual deposits are measurable in thousands or millions; and the other types generally only in thousands of tons. Igneous apatite deposits have been mined on a small scale in New York, New Jersey, and Virginia. Marine phosphorites have been mined in Montana, Idaho, Utah, Wyoming, Arkansas, Tennessee, North Carolina, South Carolina, Georgia, and Florida. Residual phosphorites have been mined in Tennessee, Pennsylvania, and Florida. River pebble has been produced in South Carolina and Florida; phosphatized rock in Tennessee and Florida; and guano in New Mexico and Texas. Present production is limited almost entirely to Florida, Tennessee, Montana, Idaho, and Wyoming. Incomplete but recently partly revised estimates indicate the presence of about 5 billion tons of phosphate deposits in the United States that is minable under present economic conditions. Deposits too lean in quality or thickness to compete with those in the western and southeastern fields probably contain tens of billions of tons.
NASA Astrophysics Data System (ADS)
Ribes, C.; Gillard, M.; Epin, M. E.; Ghienne, J. F.; Manatschal, G.; Karner, G. D.; Johnson, C. A.
2016-12-01
Research on the formation and evolution of deep-water rifted margins has undergone a major paradigm shift in recent years. An increasing number of studies of present-day and fossil rifted margins allow us to identify and characterize the structural architecture of the most distal parts of rifted margins, the so-called hyperextended, magma-poor rifted margins. However, at present, little is known about the depositional environments, sedimentary facies, stacking patterns, subsidence and thermal history within these domains. In this context, characterizing the stratal stacking patterns and understanding their spatial and temporal evolution is a new challenge. The major difficulty comes from the fact that the observed stratigraphic geometries and facies relationships are a result of the complex interplay between sediment supply and available accommodation, which is controlled by not only the regional generation of accommodation, but also by local tectono-magmatic processes. These parameters are poorly constrained or even sufficiently known in these tectonic settings. Indeed, the complex structural evolution of hyperextended magma-poor rifted margins, including the development of poly-phase in-sequence and out of sequence extensional detachment faults and associated mantle exhumation and magmatic activity, can generate complex accommodation patterns over a highly structured top basement. The presentation summarizes early results concerning the controlling parameters on ultra-deep water stratigraphic stacking patterns and to provide a conceptual framework. This observation-driven approach combines fieldwork from fossil Alpine Tethys margins exposed in the Alps and the analysis of seismic reflection data from present-day deep water rifted margins such as the Australian-Antarctic, East India and Iberia-Newfoundland margins.
Clow, David W.; Roop, Heidi; Nanus, Leora; Fenn, Mark; Sexstone, Graham A.
2015-01-01
Lakes and streams in Class 1 wilderness areas in the western United States (U.S.) are at risk from atmospheric deposition of nitrogen (N) and sulfur (S), and protection of these resources is mandated under the Federal Clean Air Act and amendments. Assessment of critical loads, which are the maximum exposure to pollution an area can receive without adverse effects on sensitive ecosystems, requires accurate deposition estimates. However, deposition is difficult and expensive to measure in high-elevation wilderness, and spatial patterns in N and S deposition in these areas remain poorly quantified. In this study, ion-exchange resin (IER) collectors were used to measure dissolved inorganic N (DIN) and S deposition during June 2006–September 2007 at approximately 20 alpine/subalpine sites spanning the Continental Divide in Rocky Mountain National Park. Results indicated good agreement between deposition estimated from IER collectors and commonly used wet + dry methods during summer, but poor agreement during winter. Snowpack sampling was found to be a more accurate way of quantifying DIN and S deposition during winter. Summer DIN deposition was significantly greater on the east side of the park than on the west side (25–50%; p ≤ 0.03), consistent with transport of pollutants to the park from urban and agricultural areas to the east. Sources of atmospheric nitrate (NO3−) were examined using N isotopes. The average δ15N of NO3− from IER collectors was 3.5‰ higher during winter than during summer (p < 0.001), indicating a seasonal shift in the relative importance of regional NOxsources, such as coal combustion and vehicular sources of atmospheric NO3−. There were no significant differences in δ15N of NO3− between east and west sides of the park during summer or winter (p = 0.83), indicating that the two areas may have similar sources of atmospheric NO3−. Results from this study indicate that a combination of IER collectors and snowpack
NASA Astrophysics Data System (ADS)
Seghedi, I.; Fülöp, A.
2009-05-01
The recent identification of debris avalanche deposits (DADs) originating from the southern edge of the Ignis peak (1306m, highest of the Gutai Mts.) has important implications for understanding its genesis in the geological context of the broader area, rich in hydrothermal intrusive-related base metal and gold-silver deposits closely connected to the Dragos Voda - Bogdan Voda strike-slip fault system. Pyroxene andesite lavas are exposed below the Ignis peak followed by hornblende and pyroxene andesites the only ones found in the DAD. The flank failure event has left an E-W-oriented horseshoe shaped scar with an estimated volume of material removed of at least 0.35 km3 and an estimated area covered by DADs of 4,345 km2 as a minimum. The deposit is a mega breccia with a variable amount of coarse matrix with jigsaw-fractured blocks, large boulders, and several southward-elongated hummocks up to 1.8 km distance from the scar. Between 720-850 m altitude the DADs contain megablocks of 5-12 m thick and up to 100 m long of layered fine-grained poorly consolidated pyroclastic materials of interlayered ash and lapillistone of fallout origin, and clay beds rich in vegetation remnants(known as the 'Chiuzbaia flora' of similar age as the surrounding lava flows, i.e. ca. 10-7 Ma) and diatoms. These megablocks found in various positions, suggest a lithological discontinuity likely representing the detachment surface of the gravity-driven instability phenomenon and the deep excavation of the volcano flank by the sector collapse event. The clayey material of these blocks acted probably as an efficient barrier to water infiltration and helped destabilization of the overlying rock mass. Since no explosive products have been observed to follow the DAD, it is possible that the sliding was triggered by pressure release of hydrothermal system along an E-W fault parallel to the Dragos Voda-Bogdan Voda fault system, with related high-grade ore deposits. This suggests the possible presence
Deposition of Boron in Possible Evaporite Deposits in Gale Crate
NASA Astrophysics Data System (ADS)
Gasda, P. J.; Peets, E.; Lamm, S. N.; Rapin, W.; Lanza, N.; Frydenvang, J.; Clark, B. C.; Herkenhoff, K. E.; Bridges, J.; Schwenzer, S. P.; Haldeman, E. B.; Wiens, R. C.; Maurice, S.; Clegg, S. M.; Delapp, D.; Sanford, V.; Bodine, M. R.; McInroy, R.
2017-12-01
Boron has been previously detected in Gale crater using the ChemCam instrument on board the NASA Curiosity rover within calcium sulfate fracture fill hosted by lacustrine mudstone and eolian sandstone units. Recent results show that up to 300 ppm B is present in the upper sections of the lacustrine unit. Boron has been detected in both the groundwater-emplaced calcium sulfate fracture fill materials and bedding-parallel calcium sulfate layers. The widespread bedding-parallel calcium sulfate layers within the upper strata of the lacustrine bedrock that Curiosity has encountered recently could be interpreted as primary evaporite deposits. We have two hypotheses for the history of boron in Gale crater. In both hypotheses, borates were first deposited as lake water evaporated, depositing primary evaporates that were later re-dissolved by groundwater, which redistributed the boron into secondary evaporitic calcium sulfate fracture fill deposits. In the first scenario, Gale crater may have undergone a period of perennial lake formation during a drier period of martian history, depositing layers of evaporitic minerals (including borates) among lacustrine mudstone layers. In the second scenario, lake margins could have become periodically exposed during cyclic drops in lake level and subsequently desiccated. Evaporites were deposited and desiccation features were formed in lowstand deposits. Either hypothetical scenario of evaporite deposition would promote prebiotic chemical reactions via wet-dry cycles. Boron may be an important prebiotic element, and as such, its presence in ancient martian surface and groundwater provides evidence that important prebiotic chemical reactions could occur on Mars if organics were present. The presence of boron in ancient Gale crater groundwater also provides additional evidence that a habitable environment existed in the martian subsurface well after the expected disappearance of liquid water on the surface of Mars. We will report on the
Cesium-137 deposition and contamination of Japanese soils due to the Fukushima nuclear accident.
Yasunari, Teppei J; Stohl, Andreas; Hayano, Ryugo S; Burkhart, John F; Eckhardt, Sabine; Yasunari, Tetsuzo
2011-12-06
The largest concern on the cesium-137 ((137)Cs) deposition and its soil contamination due to the emission from the Fukushima Daiichi Nuclear Power Plant (NPP) showed up after a massive quake on March 11, 2011. Cesium-137 ((137)Cs) with a half-life of 30.1 y causes the largest concerns because of its deleterious effect on agriculture and stock farming, and, thus, human life for decades. Removal of (137)Cs contaminated soils or land use limitations in areas where removal is not possible is, therefore, an urgent issue. A challenge lies in the fact that estimates of (137)Cs emissions from the Fukushima NPP are extremely uncertain, therefore, the distribution of (137)Cs in the environment is poorly constrained. Here, we estimate total (137)Cs deposition by integrating daily observations of (137)Cs deposition in each prefecture in Japan with relative deposition distribution patterns from a Lagrangian particle dispersion model, FLEXPART. We show that (137)Cs strongly contaminated the soils in large areas of eastern and northeastern Japan, whereas western Japan was sheltered by mountain ranges. The soils around Fukushima NPP and neighboring prefectures have been extensively contaminated with depositions of more than 100,000 and 10,000 MBq km(-2), respectively. Total (137)Cs depositions over two domains: (i) the Japan Islands and the surrounding ocean (130-150 °E and 30-46 °N) and, (ii) the Japan Islands, were estimated to be approximately 6.7 and 1.3 PBq, [corrected] respectively.We hope our (137)Cs deposition maps will help to coordinate decontamination efforts and plan regulatory measures in Japan.
Cesium-137 deposition and contamination of Japanese soils due to the Fukushima nuclear accident
Yasunari, Teppei J.; Stohl, Andreas; Hayano, Ryugo S.; Burkhart, John F.; Eckhardt, Sabine; Yasunari, Tetsuzo
2011-01-01
The largest concern on the cesium-137 (137Cs) deposition and its soil contamination due to the emission from the Fukushima Daiichi Nuclear Power Plant (NPP) showed up after a massive quake on March 11, 2011. Cesium-137 (137Cs) with a half-life of 30.1 y causes the largest concerns because of its deleterious effect on agriculture and stock farming, and, thus, human life for decades. Removal of 137Cs contaminated soils or land use limitations in areas where removal is not possible is, therefore, an urgent issue. A challenge lies in the fact that estimates of 137Cs emissions from the Fukushima NPP are extremely uncertain, therefore, the distribution of 137Cs in the environment is poorly constrained. Here, we estimate total 137Cs deposition by integrating daily observations of 137Cs deposition in each prefecture in Japan with relative deposition distribution patterns from a Lagrangian particle dispersion model, FLEXPART. We show that 137Cs strongly contaminated the soils in large areas of eastern and northeastern Japan, whereas western Japan was sheltered by mountain ranges. The soils around Fukushima NPP and neighboring prefectures have been extensively contaminated with depositions of more than 100,000 and 10,000 MBq km-2, respectively. Total 137Cs depositions over two domains: (i) the Japan Islands and the surrounding ocean (130–150 °E and 30–46 °N) and, (ii) the Japan Islands, were estimated to be more than 5.6 and 1.0 PBq, respectively. We hope our 137Cs deposition maps will help to coordinate decontamination efforts and plan regulatory measures in Japan. PMID:22084074
Erosion and deposition on a debris-flow fan
NASA Astrophysics Data System (ADS)
Densmore, A. L.; Schuerch, P.; Rosser, N. J.; McArdell, B. W.
2011-12-01
The ability of a debris flow to entrain or deposit sediment controls the downstream evolution of flow volume, and ultimately dictates both the geomorphic impact of the flow and the potential hazard that it represents. Our understanding of the patterns of, and controls on, such flow volume changes remains extremely limited, however, partly due to a poor mechanistic grasp of the interactions between debris flows and their bed and banks. In addition, we lack a good understanding of the cumulative long-term effects of sequences of flows in a single catchment-fan system. Here we begin to address these issues by using repeated terrestrial laser scanning (TLS) to characterize the detailed surface change associated with the passage of multiple debris flows on the Illgraben fan, Switzerland. We calculate surface elevation change along a 300 m study reach, and from this derive the downfan rate of flow volume change, or lag rate; for comparison, we also derive the spatially-averaged lag rate over the entire ~2 km length of the fan. Lag rates are broadly comparable over both length scales, indicating that flow behavior does not vary significantly across the fan for most flows, but importantly we find that flow volume at the fan head is a poor predictor of volume at the fan toe. The sign and magnitude of bed elevation change scale with local flow depth; at flow depths < 2 m, erosion and deposition are approximately equally likely, but erosion becomes increasingly dominant for flow depths > 2 m. On the Illgraben fan, this depth corresponds to a basal shear stress of 3-4 kPa. Because flow depth is in part a function of channel cross-sectional topography, which varies strongly both within and between flows, this result indicates that erosion and deposition are likely to be highly dynamic. The dependence of flow volume change on both the channel topography and the flow history may thus complicate efforts to predict debris-flow inundation areas by simple flow routing. We then apply
Benson, L.
1994-01-01
During the late Quarternary, the elevation of terrace cutting and carbonate deposition in the Pyramid Lake subbasin were controlled by constancy of lake level imposed by spill to adjoining subbasins. Sill elevations are 1177-1183 m (Mud Lake Slough Sill), 1207 m (Emerson Pass Sill), and 1265 m (Darwin Pass Sill). Carbonate deposition was favored by: (1) hydrologic closure, (2) proximity to a source of calcium, (3) elevated water temperature, and (4) a solid substrate. The thickness and aspect of tufa are a function oflake-level dynamics. Relatively thin sheets and pendant sheets were deposited during a rising or falling lake. The upper parts of thick reef-form tufas have a horizontal aspect and were deposited in a lake which was stabilized by spill to the Carson Desert subbasin. The lower parts of the reef-form tufas are thinner and their outer surface has a vertical aspect, indicating that the lower part formed in a receding lake. The thickest and most complete sequences of tufa are mounds that border the Pyramid Lake shore. The tops of the tallest mounds reach the elevation of the Darwin Pass Sill and many mounds have been eroded to the elevations of the Mud Lake Slough Sill of the Emerson Pass Sill. The sequence of tufa formation (from oldest to youngest) displayed in these mounds is: (1) a beachrock containing carbonate-cemented volcanic cobbles, (2) broken and eroded old spheroids that contain thinolitic tufa and an outer rind of dense laminated tufa, (3) large cylindrical (tubular) tufas capped by (4) coatings of old dense tufas, and (5) several generations of old branching tufa commonly associated with thin, platy tufas and coatings of thinolitic tufa, (6) young spheroids that contain poorly oriented young thinolitic tufa in the center and several generations of radially oriented young thinolitic tufas near the outer edge, (7) a transitional thinolite-to-branching tufa, (8) two or more layers of young branching tufa, (9) a 0.5-cm-thick layer of fine
The dilemma of the Jiaodong gold deposits: Are they unique?
Goldfarb, Richard J.; Santosh, M.
2013-01-01
The ca. 126–120 Ma Au deposits of the Jiaodong Peninsula, eastern China, define the country's largest gold province with an overall endowment estimated as >3000 t Au. The vein and disseminated ores are hosted by NE- to NNE-trending brittle normal faults that parallel the margins of ca. 165–150 Ma, deeply emplaced, lower crustal melt granites. The deposits are sited along the faults for many tens of kilometers and the larger orebodies are associated with dilatational jogs. Country rocks to the granites are Precambrian high-grade metamorphic rocks located on both sides of a Triassic suture between the North and South China blocks. During early Mesozoic convergent deformation, the ore-hosting structures developed as ductile thrust faults that were subsequently reactivated during Early Cretaceous “Yanshanian” intracontinental extensional deformation and associated gold formation.Classification of the gold deposits remains problematic. Many features resemble those typical of orogenic Au including the linear structural distribution of the deposits, mineralization style, ore and alteration assemblages, and ore fluid chemistry. However, Phanerozoic orogenic Au deposits are formed by prograde metamorphism of accreted oceanic rocks in Cordilleran-style orogens. The Jiaodong deposits, in contrast, formed within two Precambrian blocks approximately 2 billion years after devolatilization of the country rocks, and thus require a model that involves alternative fluid and metal sources for the ores. A widespread suite of ca. 130–123 Ma granodiorites overlaps temporally with the ores, but shows a poor spatial association with the deposits. Furthermore, the deposit distribution and mineralization style is atypical of ores formed from nearby magmas. The ore concentration requires fluid focusing during some type of sub-crustal thermal event, which could be broadly related to a combination of coeval lithospheric thinning, asthenospheric upwelling, paleo-Pacific plate
Heller, Debra S; Tellier, Raymond; Pabbaraju, Kanti; Wong, Sallene; Faye-Petersen, Ona M; Muehlenbachs, Atis; Goldsmith, Cynthia; Denison, Amy; Zaki, Sherif R
Massive placental perivillous fibrinoid deposition in the placenta is thought to be an immune-related condition associated with poor perinatal outcomes, including growth restriction and intrauterine fetal demise, with a high risk of recurrence. Rare cases have been associated with Coxsackievirus infection. We present such a case and review the literature.
Mineralogy and ore fluid chemistry of the Roc Blanc Ag deposit, Jebilet Hercynian massif, Morocco
NASA Astrophysics Data System (ADS)
Essarraj, Samira; Boiron, Marie-Christine; Cathelineau, Michel; Tarantola, Alexandre; Leisen, Mathieu; Hibti, Mohamed
2017-03-01
The Roc Blanc Ag deposit is located about 20 km north of Marrakesh city (Morocco) in the Jebilet Hercynian massif. The ore bodies consist of N-S to NE-SW quartz (±carbonates) veins hosted by the Sarhlef marine sediments. These series, deposited in a Devonian-Carboniferous rift basin context, were deformed during the Hercynian orogeny, and submitted to low-grade regional metamorphism. Two major stages of fluid circulation and metal deposition are distinguished on the basis of mineralogical and paleo-fluid studies carried out on quartz and dolomite (microthermometry, Raman spectroscopy, LA-ICP-MS on individual inclusions, and O, H stable isotope data): (i) an early Fe-As stage, characterized by the circulation of metamorphic aqueous-carbonic fluids, under P-T conditions lower than 200 MPa ± 20 MPa and 400 °C respectively, along N-S structures; (ii) the ore stage, characterized by the circulation of a Na-Mg-K ± Ca high salinity brine, poor in gas but rich in metals such as Fe, Sr, Ba, Zn, Pb, ± Cu (salinity ranging from 19.6 wt% to likely more than 30 wt% NaCl equiv.) and the deposition of a sphalerite/dolomite-calcite assemblage; such a fluid likely evolved to a Na-K-(Ca-Mg)-Ag brine, with significant Pb and Sb concentrations and lower Sr, Ba and Zn concentrations than in the preceding fluid (salinity up to 19.4 wt% NaCl equiv.). The Ag content of the second mineralizing brine ranges from 0.9 mmol/kg to 9.4 mmol/kg solution (100 ppm-1000 ppm), whereas the base metal brine is generally Ag poor (up to 1.3 mmol/kg solution: 140 ppm). Dilution of the Ag brine by low salinity fluids (<6 wt% NaCl equiv., and Th from 130° to 230 °C) seems to be the main driving mechanism for the Ag ore deposition at Roc Blanc, with a possible involvement of cooling and reduction reactions in black schists. Base metal and Ag fluids may have circulated at average temperatures around 200 ± 30 °C or slightly higher and under hydrostatic pressures, along dominant E-W structures. The ore
Chung, Jung Wha; Shin, Eun; Kim, Haeryoung; Han, Ho-Seong; Cho, Jai Young; Choi, Young Rok; Hong, Sukho; Jang, Eun Sun; Kim, Jin-Wook; Jeong, Sook-Hyang
2018-05-01
Hepatic iron overload is associated with liver injury and hepatocarcinogenesis; however, it has not been evaluated in patients with hepatocellular carcinoma (HCC) in Asia. The aim of this study was to clarify the degree and distribution of intrahepatic iron deposition, and their effects on the survival of HCC patients. Intrahepatic iron deposition was examined using non-tumorous liver tissues from 204 HCC patients after curative resection, and they were scored by 2 semi-quantitative methods: simplified Scheuer's and modified Deugnier's methods. For the Scheuer's method, iron deposition in hepatocytes and Kupffer cells was separately evaluated, while for the modified Deugnier's method, hepatocyte iron score (HIS), sinusoidal iron score (SIS) and portal iron score (PIS) were systematically evaluated, and the corrected total iron score (cTIS) was calculated by multiplying the sum (TIS) of the HIS, SIS, and PIS by the coefficient. The overall prevalence of hepatic iron was 40.7% with the simplified Scheuer's method and 45.1% with the modified Deugnier's method with a mean cTIS score of 2.46. During a median follow-up of 67 months, the cTIS was not associated with overall survival. However, a positive PIS was significantly associated with a lower 5-year overall survival rate (50.0%) compared with a negative PIS (73.7%, P = .006). In the multivariate analysis, a positive PIS was an independent factor for overall mortality (hazard ratio, 2.310; 95% confidence interval, 1.181-4.517). Intrahepatic iron deposition was common, and iron overload in the portal tract indicated poor survival in curatively resected HCC patients. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Dekov, V.M.; Kamenov, George D.; Savelli, C.; Stummeyer, Jens; Thiry, M.; Shanks, Wayne C.; Willingham, A.L.; Boycheva, T.B.; Rochette, P.; Kuzmann, E.; Fortin, D.; Vertes, A.
2009-01-01
A sediment core taken from the south-east slope of the Eolo Seamount is composed of alternating red-brown and light-brown to bluish-grey layers with signs of re-deposition in the middle-upper section. The red-brown layers are Fe-rich metalliferous sediments formed as a result of low-temperature (??? 77????C) hydrothermal discharge, whereas the bluish-grey layers most probably originated from background sedimentation of Al-rich detrital material. The metalliferous layers are composed mainly of Si-rich goethite containing some Al. Co-precipitation of hydrothermally released SiO44- and Fe2+ as amorphous or poorly crystalline Fe-Si-oxyhydroxides explains the high Si concentration in goethite. The elevated Al content of the goethite is fairly unusual, but reflects the extremely high background Al content of the Tyrrhenian seawater due to the high eolian terrigenous flux from the Sahara desert. The Sr and Nd isotope data suggest that the Eolo metalliferous sediments are the product of a 3-component mixture: hydrothermal fluid, seawater, and detrital material (Saharan dust and Aeolian Arc material). The enrichment in Fe, P, As, Mo, Cd, Be, Sb, W, Y, V, depletion in REE and transition elements (Cu, Co, Ni, Zn) and the REE distribution patterns support the low-temperature hydrothermal deposition of the metalliferous layers. The hydrothermal field is located in a seawater layer of relative O2 depletion, which led to a significant fractionation of the hydrothermally emitted Fe and Mn. Fe-oxyhydroxides precipitated immediately around the vents whereas Mn stayed in solution longer and the Mn-oxides precipitated higher up on the seamount slope in seawater with relatively higher O2 levels. High seismic activity led to sediment re-deposition and slumping of the Mn-rich layers down slope and mixing with the Fe-rich layers. ?? 2009 Elsevier B.V. All rights reserved.
Zheng, Xinxin; Guo, Rui
2018-01-01
We report a rhodium-catalyzed asymmetric formal intermolecular [4 + 2] cycloaddition reaction of 2-alkylenecyclobutanols with α,β-unsaturated cyclic ketones leading to synthetically useful trans-bicyclic molecules. Three consecutive stereogenic centers are formed in a highly enantio- and diastereoselective manner. Stepwise C–C bond cleavage and annulation are likely involved in the reaction pathway. Here, iPr-Duphos is the viable chiral ligand that promotes excellent enantio-control. PMID:29675233
Geva, Esther; Massey-Garrison, Angela
2013-01-01
The overall objective of this article is to examine how oral language abilities relate to reading profiles in English language learners (ELLs) and English as a first language (EL1) learners, and the extent of similarities and differences between ELLs and EL1s in three reading subgroups: normal readers, poor decoders, and poor comprehenders. The study included 100 ELLs and 50 EL1s in Grade 5. The effect of language group (ELL/EL1) and reading group on cognitive and linguistic skills was examined. Except for vocabulary, there was no language group effect on any measure. However, within ELL and EL1 alike, significant differences were found between reading groups: Normal readers outperformed the two other groups on all the oral language measures. Distinct cognitive and linguistic profiles were associated with poor decoders and poor comprehenders, regardless of language group. The ELL and EL1 poor decoders outperformed the poor comprehenders on listening comprehension and inferencing. The poor decoders displayed phonological-based weaknesses, whereas the poor comprehenders displayed a more generalized language processing weakness that is nonphonological in nature. Regardless of language status, students with poor decoding or comprehension problems display difficulties with various aspects of language.
Graham, G.E.; Kelley, K.D.
2009-01-01
The Drenchwater shale-hosted Zn-Pb-Ag deposit and the immediate vicinity, on the northern flank of the Brooks Range in north-central Alaska, is an ideal example of a naturally low pH system. The two drainages, Drenchwater and False Wager Creeks, which bound the deposit, differ in their acidity and metal contents. Moderately acidic waters with elevated concentrations of metals (pH ??? 4.3, Zn ??? 1400 ??g/L) in the Drenchwater Creek drainage basin are attributed to weathering of an exposed base-metal-rich massive sulfide occurrence. Stream sediment and water chemistry data collected from False Wager Creek suggest that an unexposed base-metal sulfide occurrence may account for the lower pH (2.7-3.1) and very metal-rich waters (up to 2600 ??g/L Zn, ??? 260 ??g/L Cu and ???89 ??g/L Tl) collected at least 2 km upstream of known mineralized exposures. These more acidic conditions produce jarosite, schwertmannite and Fe-hydroxides commonly associated with acid-mine drainage. The high metal concentrations in some water samples from both streams naturally exceed Alaska state regulatory limits for freshwater aquatic life, affirming the importance of establishing base-line conditions in the event of human land development. The studies at the Drenchwater deposit demonstrate that poor water quality can be generated through entirely natural weathering of base-metal occurrences, and, possibly unmineralized black shale.
A step toward development of printable dosage forms for poorly soluble drugs.
Raijada, Dhara; Genina, Natalja; Fors, Daniela; Wisaeus, Erik; Peltonen, Jouko; Rantanen, Jukka; Sandler, Niklas
2013-10-01
The purpose of this study was to formulate printable dosage forms for a poorly soluble drug (piroxicam; PRX) and to gain understanding of critical parameters to be considered during development of such dosage forms. Liquid formulations of PRX were printed on edible paper using piezoelectric inkjet printing (PIJ) and impression printing (flexography). The printed dosage forms were characterized using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) and the amount of drug was determined using high-performance liquid chromatography. Solutions of PRX in polyethylene glycol 400 (PEG-400):ethanol (40:60) and in PEG-400 were found to be optimal formulations for PIJ and flexography, respectively. SEM-EDX analysis revealed no visible solid particles on the printed dosage forms indicating the drug most likely remained in solution after printing. More accurate drug deposition was obtained by PIJ as compared with flexography. More than 90% drug release was achieved within 5 min regardless of printing method used. The solubility of drug in solvents/cosolvents, rheological properties of formulations, properties of substrate, feasibility and accuracy of the printing methods, and detection limit of analytical techniques for characterization of printed dosage forms are some of the concerns that need to be addressed for development of printable dosage forms of poorly soluble drugs. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association.
Growth and dielectric properties of ZnO nanoparticles deposited by using electrophoretic deposition
NASA Astrophysics Data System (ADS)
Chung, Yoonsung; Park, Hyejin; Kim, Dong-Joo; Cho, Sung Baek; Yoon, Young Soo
2015-05-01
The deposition behavior of ZnO nanoparticles on metal plates and conductive fabrics was investigated using electrophoretic deposition (EPD). The deposition kinetics on both metal plates and fabrics were examined using the Hamaker equation. Fabric substrates give more deposited weight than flat substrates due to their rougher shape and higher surface area. The morphologies and the structures of the deposited ZnO layers showed uniform deposition without any preferred orientation on both substrates. The dielectric properties of the ZnO layers formed by using EPD showed values that were reduced, but comparable to those of bulk ZnO. This result suggests that EPD is a convenient method to deposit functional oxides on flexible substrates.
Eberhart, Michael G.; Yehia, Baligh R.; Hillier, Amy; Voytek, Chelsea D.; Fiore, Danielle J.; Blank, Michael; Frank, Ian; Metzger, David S.; Brady, Kathleen A.
2015-01-01
Background Previous analyses identified specific geographic areas in Philadelphia (hotspots) associated with negative outcomes along the HIV care continuum. We examined individual and community factors associated with residing in these hotspots. Methods Retrospective cohort of 1,404 persons newly diagnosed with HIV in 2008–2009 followed for 24 months after linkage to care. Multivariable regression examined associations between individual (age, sex, race/ethnicity, HIV transmission risk, and insurance status) and community (economic deprivation, distance to care, access to public transit, and access to pharmacy services) factors and the outcomes: residence in a hotspot associated with poor retention in care and residence in a hotspot associated with poor viral suppression. Results 24.4% and 13.7% of persons resided in hotspots associated with poor retention and poor viral suppression, respectively. For persons residing in poor retention hotspots, 28.3% were retained in care compared to 40.4% of those residing outside hotspots (p<0.05). Similarly, for persons residing in poor viral suppression hotspots, 51.4% achieved viral suppression compared to 75.3% of those outside hotspots (p<.0.05). Factors significantly associated with residence in a poor retention hotspots included: female sex, lower economic deprivation, greater access to public transit, shorter distance to medical care, and longer distance to pharmacies. Factors significantly associated with residence in a poor viral suppression hotspots included; female sex, higher economic deprivation, and shorter distance to pharmacies. Conclusions Individual and community-level associations with geographic hotspots may inform both content and delivery strategies for interventions designed to improve retention in care and viral suppression. PMID:25867777
Eberhart, Michael G; Yehia, Baligh R; Hillier, Amy; Voytek, Chelsea D; Fiore, Danielle J; Blank, Michael; Frank, Ian; Metzger, David S; Brady, Kathleen A
2015-05-01
Previous analyses identified specific geographic areas in Philadelphia (hotspots) associated with negative outcomes along the HIV care continuum. We examined individual and community factors associated with residing in these hotspots. Retrospective cohort of 1404 persons newly diagnosed with HIV in 2008-2009 followed for 24 months after linkage to care. Multivariable regression examined associations between individual (age, sex, race/ethnicity, HIV transmission risk, and insurance status) and community (economic deprivation, distance to care, access to public transit, and access to pharmacy services) factors and the outcomes: residence in a hotspot associated with poor retention-in-care and residence in a hotspot associated with poor viral suppression. In total, 24.4% and 13.7% of persons resided in hotspots associated with poor retention and poor viral suppression, respectively. For persons residing in poor retention hotspots, 28.3% were retained in care compared with 40.4% of those residing outside hotspots (P < 0.05). Similarly, for persons residing in poor viral suppression hotspots, 51.4% achieved viral suppression compared with 75.3% of those outside hotspots (P < 0.0.05). Factors significantly associated with residence in poor retention hotspots included female sex, lower economic deprivation, greater access to public transit, shorter distance to medical care, and longer distance to pharmacies. Factors significantly associated with residence in poor viral suppression hotspots included female sex, higher economic deprivation, and shorter distance to pharmacies. Individual and community-level associations with geographic hotspots may inform both content and delivery strategies for interventions designed to improve retention-in-care and viral suppression.
NASA Technical Reports Server (NTRS)
Siegel, F. R.; Vaz, J. E.; Lindholm, R. C.
1982-01-01
Buried thermoluminescence dosimeters may be useful in remote sensing of petroleum and natural gas accumulations and blind uranium deposits. They act as integrating detectors that smooth out the effects of environmental variations that affect other measuring systems and result in irregularities and poor repeatability in measurements made during gas and radiometric surveys.
Complex proximal deposition during the Plinian eruptions of 1912 at Novarupta, Alaska
Houghton, Bruce F.; Wilson, C.J.N.; Fierstein, J.; Hildreth, W.
2004-01-01
Proximal (<3 km) deposits from episodes II and III of the 60-h-long Novarupta 1912 eruption exhibit a very complex stratigraphy, the result of at least four transport regimes and diverse depositional mechanisms. They contrast with the relatively simple stratigraphy (and inferred emplacement mechanisms) for the previously documented, better known, medial-distal fall deposits and the Valley of Ten Thousand Smokes ignimbrite. The proximal products include alternations and mixtures of both locally and regionally dispersed fall ejecta, and numerous thin complex deposits of pyroclastic density currents (PDCs) with no regional analogs. The locally dispersed component of the fall deposits forms sector-confined wedges of material whose thicknesses halve radially from and concentrically about the vent over distances of 100-300 m (cf. several kilometers for the medial-distal fall deposits). This locally dispersed fall material (and many of the associated PDC deposits) is rich in andesitic and banded pumices and richer in shallow-derived wall-rock lithics in comparison with the coeval medial fall units of almost entirely dacitic composition. There are no marked contrasts in grain size in the near-vent deposits, however, between locally and widely dispersed beds, and all samples of the proximal fall deposits plot as a simple continuation of grain size trends for medial-distal samples. Associated PDC deposits form a spectrum of facies from fines-poor, avalanched beds through thin-bedded, landscape-mantling beds to channelized lobes of pumice-block-rich ignimbrite. The origins of the Novarupta near-vent deposits are considered within a spectrum of four transport regimes: (1) sustained buoyant plume, (2) fountaining with co-current flow, (3) fountaining with counter-current flow, and (4) direct lateral ejection. The Novarupta deposits suggest a model where buoyant, stable, regime-1 plumes characterized most of episodes II and III, but were accompanied by transient and variable
Brushite coatings on titanium for orthopedic implants: Studies on deposition and transformation
NASA Astrophysics Data System (ADS)
Kumar, Mukesh
Hydroxyapatite (HA, Ca5(PO4)3OH) coating on the metallic substrate is expected to assist bone growth and implant integration. However, HA is quite stable in physiological solution and the use of other more reactive calcium phosphate ceramics (CPC) could induce faster bone growth by providing calcium and phosphate ions to the interacting physiological solution. This study utilized a non-line of sight electrodeposition process to achieve brushite (CaHPO4.2H2O) coatings. The uses of potassium or sodium chloride as a conducting electrolyte in the depositing bath enhanced deposition rates and altered the morphology of the coatings. Analysis suggested a strained deposit with sight specific substitution of cations from the conducting electrolyte. Such a deposit (modified brushite) was determined to have CaHPO 4.2H2O and CaY2(1-x)HPO4•2H 2O (x ˜0.95) with Y as Na0 or K. Whereas normal brushite was obtained from unsupported baths. The deposited mass of brushite increased with charge consumed and bonding to the substrate decreased with increasing deposition time. Though inconclusive. in-situ studies on electrodeposition did not rule out the possibility of ionic species responsible for the deposit. Transformations of both forms of brushite were investigated in calcium free Hank's type simulated body fluid. Modified brushite showed periodic appearance of freshly precipitated, but poorly crystalline HA, without the benefit of monetite (CaHPO4) as an intermediate. However, normal brushite transformation showed nonstoichiometric HA with monetite as an intermediate. Normal brushite demonstrated a slower transformation to HA when compared to the transformation kinetics of modified brushite. It is shown that lattice strain due to localized ion incorporation could be used to after the properties of brushite coatings to adjust the kinetics of transformation and indirectly the amount of calcium and phosphate ions released into the surrounding.
NASA Astrophysics Data System (ADS)
Weiss, S. B.
2011-12-01
Atmospheric nitrogen deposition threatens biodiversity in many parts of the world. In California, 20% of the land surface receives > 5 kg-N ha-1 year-1, with hotspots receiving > 50 kg-N ha-1 year-1. Documented impacts of N-deposition include increased growth of annual grass and other invasives in coastal sage scrub, serpentine grasslands, vernal pools, and deserts, altered nutrient cycling and fuel accumulation of montane forests, enhanced fire cycles, nitrate leaching into surface and groundwater, and eutrophication of montane lakes such as Lake Tahoe. 40% of listed threatened and endangered plants are exposed to > 5 kg-N ha-1 year-1, and N-deposition is arguably a greater immediate threat to biodiversity than is climate change. Appropriate policy responses are lagging, because the magnitude of N-deposition impacts on biodiversity is poorly known in the broader conservation/regulatory community and the general public. Policies to decrease emissions and deposition are clearly the ultimate solution on a decadal time scale. In the interim, habitat management is critical to preventing extinction of many species. This presentation reviews recent policies and regulatory actions in California that address N-deposition impacts on biodiversity. The immediate and long-term needs for invasive weed management are overwhelming and require long-term endowment funding. Mitigation requirements under the US Endangered Species Act have been used to secure land and management resources. The on-going story of the threatened Bay checkerspot butterfly, from the first precedent setting mitigation in 2001 through a regional Habitat Conservation Plan (HCP), illustrates the development of these novel policies based on science, regulatory authority, grassroots activism, public education, habitat restoration, and legal actions. The 50-year HCP will ultimately result in a network of conserved lands with management endowments. Eventually N-deposition may be reduced below critical loads
Assessing the risk of nitrogen deposition to natural resources in the Four Corners area
Reed, Sasha C.; Belnap, Jayne; Floyd-Hanna, Lisa; Crews, Tim; Herring, Jack; Hanna, Dave; Miller, Mark E.; Duniway, Michael C.; Roybal, Carla M.
2013-01-01
Nitrogen (N) deposition in the western U.S. is on the rise and is already dramatically affecting terrestrial ecosystems. For example, N deposition has repeatedly been shown to lower air and water quality, increase greenhouse gas emissions, alter plant community composition, and significantly modify fire regimes. Accordingly, the effects of N deposition represent one of our largest environmental challenges and make difficult the National Park Service’s (NPS) important mission to “preserve the scenery and the natural and historic objects and the wildlife… unimpaired for the enjoyment of future generations”. Due to increased population growth and energy development (e.g., natural gas wells), the Four Corners region has become a notable ‘hotspot’ for N deposition. However, our understanding of how increased N deposition will affect these unique ecosystems, as well as how much deposition is actually occurring, remains notably poor. Here we used a multi-disciplinary approach to gathering information in an effort to help NPS safeguard the Four Corners national parks, both now and into the future. We applied modeling, field, and laboratory techniques to clarify current N deposition gradients and to help elucidate the ecosystem consequences of N deposition to the national parks of the Four Corners area. Our results suggest that NOx deposition does indeed represent a significant source of N to Mesa Verde National Park and, as expected, N deposition significantly affects coupled biogeochemical cycling (N, carbon, and phosphorus) of these landscapes. We also found some surprising results. For example, perhaps due to the low nutrient availability in these (and other) dryland ecosystems, although most other research suggests that adding N reduces N fixation rates, N additions did not consistently reduce natural N inputs via biological N2 fixation at our dryland sites. While the timeline of this pilot project is too brief to elucidate all the potential insight from
The Interaction of Carbon Monoxide with Rhodium on Potassium-Modified CeO 2(111)
Mullins, David R.
2016-02-03
The adsorption and reactions of CO adsorbed on Rh particles deposited on K-covered CeO 2(111) were studied by temperature programmed desorption and photoelectron spectroscopy. K deposited on CeO 2(111) forms a KO X over-layer by extracting O from the ceria and partially reducing some of the Ce 4+ to Ce 3+. CO does not adsorb on the KO X / CeO 2-X(111) surface in the absence of Rh particles. CO adsorbed on Rh / K / CeO 2(111) adsorbs molecularly on the Rh at 200 K. As the surface is heated the CO spills-over and reacts with the KOX tomore » form carbonate. The carbonate decomposes at elevated temperature to produce CO and CO 2. The carbonate stabilizes the KO X so that K desorbs at a higher temperature than it would in the absence of CO. When the Rh and K deposition are reversed so that K is deposited on both the Rh and the CeO 2(111), CO adsorbs as CO 2- at 200 K. The CO 2- decomposes below 350 K to produce gas phase CO and adsorbed CO3 2- and CO. The CO is stabilized by the K on the Rh and desorbs above 540 K. The carbonate decomposes into gas phase CO and CO 2.« less
Reactive flow models of the Anarraaq Zn-Pb-Ag deposit, Red Dog district, Alaska
Schardt, C.; Garven, G.; Kelley, K.D.; Leach, D.L.
2008-01-01
The Red Dog ore deposit district in the Brooks Range of northern Alaska is host to several high-grade, shale-hosted Zn + Pb deposits. Due to the complex history and deformation of these ore deposits, the geological and hydrological conditions at the time of formation are poorly understood. Using geological observations and fluid inclusion data as constraints, numerical heat and fluid flow simulations of the Anarraaq ore deposit environment and coupled reactive flow simulations of a section of the ore body were conducted to gain more insight into the conditions of ore body formation. Results suggest that the ore body and associated base metal zonation may have formed by the mixing of oxidized, saline, metal-bearing hydrothermal fluids (<200??C) with reducing, HS-rich pore fluids within radiolarite-rich host rocks. Sphalerite and galena concentrations and base metal sulfide distribution are primarily controlled by the nature of the pore fluids, i.e., the extent and duration of the HS- source. Forward modeling results also predict the distribution of pyrite and quartz in agreement with field observations and indicate a reaction front moving from the initial mixing interface into the radiolarite rocks. Heuristic mass calculations suggest that ore grades and base metal accumulation comparable to those found in the field (18% Zn, 5% Pb) are predicted to be reached after about 0.3 My for initial conditions (30 ppm Zn, 3 ppm Pb; 20% deposition efficiency). ?? Springer-Verlag 2008.
Kauhanen, L; Lynch, J W; Lakka, H-M; Kauhanen, J; Smith, G D
2010-05-01
Previous research has suggested that dehydration in infancy may lead to high blood pressure in later life because of sodium retention. The purpose of this study was to examine the effect of poor hygiene of the child, poor social and poor housing conditions at home and diarrhoea in childhood as proxies for dehydration on high blood pressure in later life. Data were from a subset of participants in the Kuopio Ischaemic Heart Disease Risk Factor Study, a population-based cohort study in eastern Finland. Information on childhood factors was collected from school health records (n=952), from the 1930s to the 1950s. Adult data were obtained from baseline examinations of the Kuopio Ischaemic Heart Disease Risk Factor Study cohort (n=2682) in 1984-1989. Men who had poor hygiene in childhood had on average 4.07 mm Hg (95% CI 0.53 to 7.61) higher systolic blood pressure than men who had good or satisfactory hygiene in childhood in the age-adjusted analysis. Reports of diarrhoea were not associated with adult blood pressure. The authors' findings suggest that poor hygiene and living in poor social conditions in childhood are associated with higher systolic blood pressure in adulthood. Reported childhood diarrhoea did not explain the link between hygiene and high blood pressure in adulthood.
NASA Astrophysics Data System (ADS)
Barra, F.; Rojas, P.; Reich, M.; Deditius, A.; Simon, A. C.
2017-12-01
Iron oxide-apatite (IOA) or "Kiruna-type" deposits are an important source of Fe, P, REE, among other essential elements for society. Three main hypotheses have been proposed to explain the genesis of these controversial deposits, which invoke liquid immiscibility, hydrothermal replacement or a magmatic-hydrothermal origin driven by flotation of magnetite-bubble pairs. Here we focus on the El Romeral, one of the largest IOA deposits located in the southernmost part of the Cretaceous Chilean Iron Belt. We combined SEM observations and EMPA analyses of magnetite, actinolite, pyrite, and apatite, with micro-Raman determinations of mineral inclusions within magnetite grains. Two textural types of magnetite were identified at El Romeral: (i) inclusion-rich magnetite (Mag I), and (ii) inclusion-poor magnetite (Mag II) that are commonly surrounding the inclusion-rich Mag I grains. Mag I is characterized by high V ( 2500-2800 ppm) and Ti (300-1000 ppm) contents with high-temperature mineral inclusions such as ilmenite, Ti-pargasite and clinochlore at depth, and quartz and phlogopite inclusions in shallower samples. These characteristics are consistent with a magmatic origin for Mag I. Inclusion-poor magnetite (Mag II) have high V (2400-2600 ppm) and lower Ti (70-200 ppm) contents than Mag I, which point to chemical changes of the mineralizing fluid(s). An increase in thermal gradient with depth is evidenced by the presence of high-temperature (low #Fe) actinolite, as well as F-rich apatite and pyrite with high Co:Ni (>1) in the deep zones. In contrast, lower Co:Ni ratios (<0.5) in pyrite and higher Cl contents in OH-rich apatite are detected in samples from shallower levels. This vertical chemical variation supports a magmatic-hydrothermal origin for the El Romeral deposit, and point to compositional changes driven by decompression of a magnetite-fluid suspension.
Roussillon, Yann; Scholz, Jeremy H; Shelton, Addison; Green, Geoff T; Utthachoo, Piyaphant
2014-01-21
Methods and devices are provided for improved deposition systems. In one embodiment of the present invention, a deposition system is provided for use with a solution and a substrate. The system comprises of a solution deposition apparatus; at least one heating chamber, at least one assembly for holding a solution over the substrate; and a substrate curling apparatus for curling at least one edge of the substrate to define a zone capable of containing a volume of the solution over the substrate. In another embodiment of the present invention, a deposition system for use with a substrate, the system comprising a solution deposition apparatus; at heating chamber; and at least assembly for holding solution over the substrate to allow for a depth of at least about 0.5 microns to 10 mm.
Thermal Anomaly Engendered by the Emplacement of AN Au-DEPOSIT: Example from the Franciscan Complex
NASA Astrophysics Data System (ADS)
Lahfid, A.; Lacroix, B.; Delchini, S.; Hughes, J.
2016-12-01
The thermal history of the Lucia subterrane located within the Franciscan Complex (California, USA) has been previously proposed by Underwood et al. (1995). Based on both vitrinite reflectance (Rm) and illite cristallinity methods, these authors suggest that the Lucia subterrane is locally perturbed by a thermal anomaly (up to 300ºC), probably caused by the emplacement of an Au-deposit: the Los Burros Gold deposit. Although both the thermal anomaly and the deposit seem spatially correlated, their relationship is still poorly constrained. In order to better explain the anomalous temperatures recorded in the vicinity of the deposit and their possible link with mineralization processes, we first performed detailed geological and structural mapping within the Los Burros district coupled to a thermal study. The peak temperature reached by metasediments from the Lucia subterrane have been regionally investigated using Raman Spectroscopy of Carbonaceous Materials (RSCM) method. In addition, through a careful fluid-inclusion study of the deposit, the potential source and the temperature of the fluid responsible for the Los Burros Au-deposit emplacement are currently being investigated. Our preliminary results confirm the previous temperatures and the presence of the thermal anomaly in the range 260-320ºC as inferred by Underwood et al (1995). In addition, our structural interpretation shows that the Los Burros deposit was emplaced during a late tectonic event marked by local reorientation of the regional tectonic features and the emplacement of meter-wide, quartz-calcite-sulfide extension veins. The temperatures determined by both methods (RSCM thermometry and fluid inclusion microthermometry) are consistent and support that the thermal anomaly is likely generated by the emplacement of the Los Burros Au-deposit during a local tectonic event.
Zimmermann, Sonja; Wolff, Carolina; Sures, Bernd
2017-05-01
Mainly due to automobile traffic, but also due to other sources, the platinum group elements (PGE) platinum (Pt), palladium (Pd) and rhodium (Rh) are introduced into aquatic biotopes where they accumulate in sediments of lakes and rivers. However, the toxicity of these noble metals to aquatic organisms is not well understood and especially toxicity studies under standardized condition are lacking. Thus, the toxicity of Pt, Pd and Rh to Daphnia magna was tested in single metal exposure experiments according to OECD guideline 202. Immobility and lethality was recorded after 24 h and 48 h of exposure and EC 50 and LC 50 , respectively, were determined. As the nominal exposure concentration of Pd differed significantly from the quantified concentration, the control of the real exposure concentration by chemical analysis is mandatory, especially for Pd. The toxicity decreased in the order Pd > Pt ≫ Rh with e.g. LC 50 (48 h) values of 14 μg/L for Pd, 157 μg/L for Pt and 56,800 μg/L for Rh. The exposure period had a clear effect on the toxicity of Pt, Pd and Rh. For Pt and Rh the endpoint immobility was more sensitive than the endpoint lethality whereas Pd toxicity was similar for both endpoints. The Hill slopes, which are a measure for the steepness of the concentration-response curves, showed no significant discrepancies between the different metals. The binary metal exposure to Pt and Pd revealed a more-than-additive, i.e. a synergistic toxicity using the toxic unit approach. The present study is a start to understand the toxicity of interacting PGE. The modes of action behind the synergistic effect are unclear. Copyright © 2017 Elsevier Ltd. All rights reserved.
2015-01-01
Rhodium metalloinsertors are octahedral complexes that bind DNA mismatches with high affinity and specificity and exhibit unique cell-selective cytotoxicity, targeting mismatch repair (MMR)-deficient cells over MMR-proficient cells. Here we describe a new generation of metalloinsertors with enhanced biological potency and selectivity, in which the complexes show Rh–O coordination. In particular, it has been found that both Δ- and Λ-[Rh(chrysi)(phen)(DPE)]2+ (where chrysi =5,6 chrysenequinone diimmine, phen =1,10-phenanthroline, and DPE = 1,1-di(pyridine-2-yl)ethan-1-ol) bind to DNA containing a single CC mismatch with similar affinities and without racemization. This is in direct contrast with previous metalloinsertors and suggests a possible different binding disposition for these complexes in the mismatch site. We ascribe this difference to the higher pKa of the coordinated immine of the chrysi ligand in these complexes, so that the complexes must insert into the DNA helix with the inserting ligand in a buckled orientation; spectroscopic studies in the presence and absence of DNA along with the crystal structure of the complex without DNA support this assignment. Remarkably, all members of this new family of compounds have significantly increased potency in a range of cellular assays; indeed, all are more potent than cisplatin and N-methyl-N′-nitro-nitrosoguanidine (MNNG, a common DNA-alkylating chemotherapeutic agent). Moreover, the activities of the new metalloinsertors are coupled with high levels of selective cytotoxicity for MMR-deficient versus proficient colorectal cancer cells. PMID:25254630
Yoshimura, Takayoshi; Taketsugu, Tetsuya; Sawamura, Masaya
2017-01-01
We explored the reaction mechanism of the cationic rhodium(i)–BINAP complex catalysed isomerisation of allylic amines using the artificial force induced reaction method with the global reaction route mapping strategy, which enabled us to search for various reaction paths without assumption of transition states. The entire reaction network was reproduced in the form of a graph, and reasonable paths were selected from the complicated network using Prim’s algorithm. As a result, a new dissociative reaction mechanism was proposed. Our comprehensive reaction path search provided rationales for the E/Z and S/R selectivities of the stereoselective reaction. PMID:28970877
Particle deposition in a peri-urban Mediterranean forest.
Fares, Silvano; Savi, Flavia; Fusaro, Lina; Conte, Adriano; Salvatori, Elisabetta; Aromolo, Rita; Manes, Fausto
2016-11-01
Urban and peri-urban forests provide a multitude of Ecosystem Services to the citizens. While the capacity of removing carbon dioxide and gaseous compounds from the atmosphere has been tested, their capacity to sequestrate particles (PM) has been poorly investigated. Mediterranean forest ecosystems are often located nearby or inside large urban areas. This is the case of the city of Rome, Italy, which hosts several urban parks and is surrounded by forested areas. In particular, the Presidential Estate of Castelporziano is a 6000 ha forested area located between the Tyrrhenian coast and the city (25 km downtown of Rome). Under the hypothesis that forests can ameliorate air quality thanks to particle deposition, we measured fluxes of PM1, 2.5 and 10 with fast optical sensors and eddy covariance technique. We found that PM1 is mainly deposited during the central hours of the day, while negligible fluxes were observed for PM 2.5 and 10. A Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT v4) simulated PM emission from traffic areas in the city of Rome and showed that a significant portion of PM is removed by vegetation in the days when the plume trajectory meets the urban forest. Copyright © 2016 Elsevier Ltd. All rights reserved.
Waythomas, C.F.; Wallace, K.L.
2002-01-01
An areally extensive volcanic mass-flow deposit of Pleistocene age, known as the Chetaslina volcanic mass-flow deposit, is a prominent and visually striking deposit in the southeastern Copper River lowland of south-central Alaska. The mass-flow deposit consists of a diverse mixture of colorful, variably altered volcanic rocks, lahar deposits, glaciolacustrine diamicton, and till that record a major flank collapse on the southwest flank of Mount Wrangell. The deposit is well exposed near its presumed source, and thick, continuous, stratigraphic exposures have permitted us to study its sedimentary characteristics as a means of better understanding the origin, significance, and evolution of the deposit. Deposits of the Chetaslina volcanic mass flow in the Chetaslina River drainage are primary debris-avalanche deposits and consist of two principal facies types, a near-source block facies and a distal mixed facies. The block facies is composed entirely of block-supported, shattered and fractured blocks with individual blocks up to 40 m in diameter. The mixed facies consists of block-sized particles in a matrix of poorly sorted rock rubble, sand, and silt generated by the comminution of larger blocks. Deposits of the Chetaslina volcanic mass flow exposed along the Copper, Tonsina, and Chitina rivers are debris-flow deposits that evolved from the debris-avalanche component of the flow and from erosion and entrainment of local glacial and glaciolacustrine diamicton in the Copper River lowland. The debris-flow deposits were probably generated through mixing of the distal debris avalanche with the ancestral Copper River, or through breaching of a debris-avalanche dam across the ancestral river. The distribution of facies types and major-element chemistry of clasts in the deposit indicate that its source was an ancestral volcanic edifice, informally known as the Chetaslina vent, on the southwest side of Mount Wrangell. A major sector collapse of the Chetaslina vent initiated
Multi-chamber deposition system
Jacobson, Richard L.; Jeffrey, Frank R.; Westerberg, Roger K.
1989-10-17
A system for the simultaneous deposition of different coatings onto a thin web within a large volume vacuum chamber is disclosed which chamber is provided with a plurality of deposition chambers in which the different layers are deposited onto the film as its moves from a supply roll to a finished take-up roll of coated web. The deposition chambers provided within the large vacuum chamber are provided with separate seals which minimize back diffusion of any dopant gas from adjacent deposition chambers.
Multi-chamber deposition system
Jacobson, Richard L.; Jeffrey, Frank R.; Westerberg, Roger K.
1989-06-27
A system for the simultaneous deposition of different coatings onto a thin web within a large volume vacuum chamber is disclosed which chamber is provided with a plurality of deposition chambers in which the different layers are deposited onto the film as its moves from a supply roll to a finished take-up roll of coated web. The deposition chambers provided within the large vacuum chamber are provided with separate seals which minimize back diffusion of any dopant gas from adjacent deposition chambers.
Majumder, Nabanita; Ram, Faujdar
2015-01-01
Objectives We examined the overall contributions of the poor and non-poor in fertility decline across the Asian countries. Further, we analyzed the direct and indirect factors that determine the reproductive behaviour of two distinct population sub-groups. Design Data from several new rounds of DHS surveys are available over the past few years. The DHS provides cross-nationally comparable and useful data on fertility, family planning, maternal and child health along with the other information. Six selected Asian countries namely: Bangladesh, India, Indonesia, Nepal, Philippines, and Vietnam are considered for the purpose of the study. Three rounds of DHS surveys for each country (except Vietnam) are considered in the present study. Methods Economic status is measured by computing a “wealth index”, i.e. a composite indicator constructed by aggregating data on asset ownership and housing characteristics using principal components analysis (PCA). Computed household wealth index has been broken into three equal parts (33.3 percent each) and the lowest and the highest 33.3 percent is considered as poor and non-poor respectively. The Bongaarts model was employed to quantify the contribution of each of the proximate determinants of fertility among poor and non-poor women. Results Fertility reduction across all population subgroups is now an established fact despite the diversity in the level of socio-economic development in Asian countries. It is clear from the analysis that fertility has declined irrespective of economic status at varying degrees within and across the countries which can be attributed to the increasing level of contraceptive use especially among poor women. Over the period of time changing marriage pattern and induced abortion are playing an important role in reducing fertility among poor women. Conclusions Fertility decline among majority of the poor women across the Asian countries is accompanied by high prevalence of contraceptive use followed by
MAPLE deposition of nanomaterials
NASA Astrophysics Data System (ADS)
Caricato, A. P.; Arima, V.; Catalano, M.; Cesaria, M.; Cozzoli, P. D.; Martino, M.; Taurino, A.; Rella, R.; Scarfiello, R.; Tunno, T.; Zacheo, A.
2014-05-01
The matrix-assisted pulsed laser evaporation (MAPLE) has been recently exploited for depositing films of nanomaterials by combining the advantages of colloidal inorganic nanoparticles and laser-based techniques. MAPLE-deposition of nanomaterials meeting applicative purposes demands their peculiar properties to be taken into account while planning depositions to guarantee a congruent transfer (in terms of crystal structure and geometric features) and explain the deposition outcome. In particular, since nanofluids can enhance thermal conductivity with respect to conventional fluids, laser-induced heating can induce different ablation thermal regimes as compared to the MAPLE-treatment of soft materials. Moreover, nanoparticles exhibit lower melting temperatures and can experience pre-melting phenomena as compared to their bulk counterparts, which could easily induce shape and or crystal phase modification of the material to be deposited even at very low fluences. In this complex scenario, this review paper focuses on examples of MAPLE-depositions of size and shape controlled nanoparticles for different applications highlights advantages and challenges of the MAPLE-technique. The influence of the deposition parameters on the physical mechanisms which govern the deposition process is discussed.
2002-12-04
Like many of the craters in the Oxia Palus region of Mars, Trouvelot Crater, shown in this NASA Mars Odyssey image, hosts an eroded, light-toned, sedimentary deposit on its floor. Compared with the much larger example in Becquerel Crater to the NE, the Trouvelot deposit has been so eroded by the scouring action of dark, wind-blown sand that very little of it remains. Tiny outliers of bright material separated from the main mass attest to the once, more really extensive coverage by the deposit. A similar observation can be made for White Rock, the best known example of a bright, crater interior deposit. The origin of the sediments in these deposits remains enigmatic but they are likely the result of fallout from ash or dust carried by the thin martian atmosphere. http://photojournal.jpl.nasa.gov/catalog/PIA04017
Cassells, Irwin; Stringer, Tameryn; Hutton, Alan T; Prince, Sharon; Smith, Gregory S
2018-05-30
A series of bidentate salicylaldimine ligands was prepared and reacted with either [RuCl(µ-Cl)(p-cymene)] 2 , [RhCl(µ-Cl)(Cp*)] 2 or [IrCl(µ-Cl)(Cp*)] 2 . All of the compounds were characterised using an array of spectroscopic and analytical techniques, namely, nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy and mass spectrometry. Single crystal X-ray diffraction (XRD) was used to confirm the bidentate coordination mode of the salicylaldimine ligand to the metal centre. The platinum group metal (PGM) complexes were screened against the MCF7 breast cancer cell line. The ruthenium and iridium salicylaldimine complexes showed comparable or greater cytotoxicity than cisplatin against the MCF7 cancer cells, as well as greater cytotoxicity than their rhodium counterparts. Three of the salicylaldimine complexes showed potent activity in the range 18-21 µM. Two of these complexes had a greater affinity for cancerous cells than for CHO non-cancerous cells (SI > 4). Preliminary mechanistic studies suggest that the ruthenium complexes undergo solvation prior to 5'-GMP binding, whereas the iridium complexes were inert to the solvation process.
NASA Astrophysics Data System (ADS)
Jankowski, K. L.; Shen, Z.; Tornqvist, T. E.; Steponaitis, E.; Rosenheim, B. E.
2017-12-01
Understanding how natural systems sequester carbon, and at what rates, is critical for planning future climate change mitigation strategies. For the decade from 2006-2015, average annual CO2 emissions to the atmosphere ( 11 Pg C) are not completely offset by atmospheric retention and oceanic uptake ( 5 Pg C and 2.5 Pg C, respectively) (LeQuéré et al., 2016) implying residual terrestrial C sinks that are not fully understood. Rivers are increasingly recognized as playing a complex role in the global C cycle which, beyond acting as a source of CO2to the atmosphere, may act as a C sink. Here, we find that the mechanisms of C transfer through fluviodeltaic systems include various means of C storage and contribute significantly to the global unidentified terrestrial C sink. C sequestration by coastal wetlands - at a globally averaged rate of 200 g C/m2/yr - has been widely recognized as an important mechanism for terrestrial C sequestration, with less attention paid to the role of inland fluvial to deltaic deposition. We sampled three cores in the central Mississippi Delta for C content (using elemental analysis) and bulk density in fluviodeltaic overbank deposits as well as intercalated peat. We also established a flexible, Bayesian age-depth model using Bacon (Blaauw and Christen 2011) in order to calculate sediment accumulation rates from 14C and OSL ages. Peat deposits sequester C at an average rate of 40 g C/m2/yr. The relatively organic-poor overbank sediments sequester C at an average rate of 200 g C/m2/yr including what are likely punctuated periods of very fast deposition. While the episodic nature of overbank deposits make quantifying an annual impact difficult, it is clear that overbank deposition is an important and efficient mechanism for C sequestration in fluviodeltaic systems that deserves continued investigation.
NASA Astrophysics Data System (ADS)
Konnunaho, J. P.; Hanski, E. J.; Bekker, A.; Halkoaho, T. A. A.; Hiebert, R. S.; Wing, B. A.
2013-12-01
Archean komatiites host important resources of Ni, Cu, Co, and PGE, particularly in Western Australia and Canada. In Finland, several small, low-grade sulfide deposits have been found in komatiites, including the ca. 2.8 Ga Vaara deposit in the Archean Suomussalmi greenstone belt. It occurs in the central part of the serpentinized olivine cumulate zone of a komatiitic extrusive body and is composed of disseminated interstitial sulfides consisting of pyrite, pentlandite, millerite, violarite, and chalcopyrite accompanied by abundant magnetite. Although currently subeconomic, the mineralization is interesting due to the very high chalcophile element contents of the sulfide fraction (38 wt% Ni, 3.4 wt% Cu, 0.7 wt% Co, 22.4 ppm Pd, and 9.5 ppm Pt). The sulfides occur in relatively Cr-poor olivine cumulates suggesting involvement of a chromite-undersaturated magma. The parental magma was an Al-undepleted komatiite with an estimated MgO content of at least 24 wt%. In contrast to the common komatiite types in the eastern Finland greenstone belts, the Vaara rocks are moderately enriched in LREE relative to MREE, suggesting that crustal contamination played an important role in the genesis of the Vaara deposit. Multiple sulfur isotope data reveal considerable mass-independent sulfur isotope fractionation both in country rock sedimentary sulfides (Δ33S ranges from -0.50 to +2.37 ‰) and in the Vaara mineralization (Δ33S ranges from +0.53 to +0.66 ‰), which provides strong evidence for incorporation of crustal sulfur. Extensive replacement of interstitial sulfides by magnetite and the presence of millerite- and violarite-bearing, pyrrhotite-free sulfide assemblages indicate significant post-magmatic, low-temperature hydrothermal oxidation of the primary magmatic pyrrhotite-pentlandite-chalcopyrite assemblages and associated sulfur loss that led to a significant upgrading of the original metal tenors of the Vaara deposit.
Characterization of Cu2ZnSnS4 thin films prepared by photo-chemical deposition
NASA Astrophysics Data System (ADS)
Moriya, Katsuhiko; Watabe, Jyunichi; Tanaka, Kunihiko; Uchiki, Hisao
2006-09-01
Cu2ZnSnS4 (CZTS) thin films were prepared by post-annealing films of metal sulfides of Cu2S, ZnS and SnS2 precursors deposited on soda-lime glass substrates by photo-chemical deposition (PCD) from aqueous solution containing CuSO4, ZnSO4, SnSO4 and Na2S2O3. In this study, sulfurization was employed to prepare high quality CZTS thin films. Deposited films of metal sulfides were annealed in a furnace in an atmosphere of N2 or N2+H2S(5%) at the temperature of 300°, 400° or 500 °C. The sulfured films showed X-ray diffraction peaks from (112), (220), and (312) planes of CZTS and the peaks became sharp by an increase in the sulfurization temperature. CZTS thin film annealed in atmosphere of N2 was S-poor. After annealing atmosphere was changed from N2 into N2+H2S(5%), the decrease of a composi- tional ratio of sulfur could be suppressed.
NASA Astrophysics Data System (ADS)
Tivey, M. K.; Evans, G. N.; Ferrini, V. L.; Spierer, H.
2016-12-01
High-resolution bathymetric mapping and recovery and study of samples from precisely known locations relative to local tectonic and volcanic features provide insight into the formation of seafloor massive sulfide deposits. Additional insight comes from repeat mapping efforts in 2005 and 2016 that provide details of relations and changes that may have occurred over time. Located 21 km apart on the Valu Fa Ridge, the Tui Malila and Mariner vent fields exhibit contrasting vent fluid chemistry, mineral deposit composition, deposit morphology, and seafloor morphology. At the Tui Malila vent field, near-neutral pH fluids with low metal contents vent from Zn- and Ba-rich, but Cu-poor deposits. The highest temperature fluids are found near the intersection of two faults and between volcanic domes. In contrast, acidic, metal-rich hydrothermal fluids at the Mariner vent field vent from Cu-rich, Zn-poor deposits. No discernable faults are present. At both the Tui Malila and Mariner vent fields, intermediate temperature fluids were sampled emanating from barite-rich deposits. At the Tui Malila vent field, intermediate fluids vent from flange-dominated edifices that are located on brecciated lava flow that overlays one of the two faults. Intermediate fluids at the Mariner vent field vent from squat terrace-like edifices located peripheral (10-15 m) to high-temperature chimney edifices, and seafloor morphology is dominated by brecciated lava flows. Thermodynamic models of mixing between high-temperature hydrothermal fluids and seawater that consider subsurface deposition of sulfide minerals and iron oxyhydroxide were used to reproduce the chemistry of intermediate fluids. This study suggests that the porous, brecciated lavas characteristic of these two vent fields provide sites for subsurface mixing and contribute to mineral deposition, with the faults at the Tui Malila vent field providing a pathway for subsurface fluid flow.
Assisted deposition of nano-hydroxyapatite onto exfoliated carbon nanotube oxide scaffolds.
Zanin, H; Rosa, C M R; Eliaz, N; May, P W; Marciano, F R; Lobo, A O
2015-06-14
Electrodeposited nano-hydroxyapatite (nHAp) is more similar to biological apatite in terms of microstructure and dimension than apatites prepared by other processes. Reinforcement with carbon nanotubes (CNTs) enhances its mechanical properties and increases adhesion of osteoblasts. Here, we carefully studied nHAp deposited onto vertically aligned multi-walled CNT (VAMWCNT) scaffolds by electrodeposition and soaking in a simulated body fluid (SBF). VAMWCNTs are porous biocompatible scaffolds with nanometric porosity and exceptional mechanical and chemical properties. The VAMWCNT films were prepared on a Ti substrate by a microwave plasma chemical vapour deposition method, and then oxidized and exfoliated by oxygen plasma etching (OPE) to produce graphene oxide (GO) at the VAMWCNT tips. The attachment of oxygen functional groups was found to be crucial for nHAp nucleation during electrodeposition. A thin layer of plate-like and needle-like nHAp with high crystallinity was formed without any need for thermal treatment. This composite (henceforth referred to as nHAp-VAMWCNT-GO) served as the scaffold for in vitro biomineralization when soaked in the SBF, resulting in the formation of both carbonate-rich and carbonate-poor globular-like nHAp. Different steps in the deposition of biological apatite onto VAMWCNT-GO and during the short-term biomineralization process were analysed. Due to their unique structure and properties, such nano-bio-composites may become useful in accelerating in vivo bone regeneration processes.
Assisted deposition of nano-hydroxyapatite onto exfoliated carbon nanotube oxide scaffolds
NASA Astrophysics Data System (ADS)
Zanin, H.; Rosa, C. M. R.; Eliaz, N.; May, P. W.; Marciano, F. R.; Lobo, A. O.
2015-05-01
Electrodeposited nano-hydroxyapatite (nHAp) is more similar to biological apatite in terms of microstructure and dimension than apatites prepared by other processes. Reinforcement with carbon nanotubes (CNTs) enhances its mechanical properties and increases adhesion of osteoblasts. Here, we carefully studied nHAp deposited onto vertically aligned multi-walled CNT (VAMWCNT) scaffolds by electrodeposition and soaking in a simulated body fluid (SBF). VAMWCNTs are porous biocompatible scaffolds with nanometric porosity and exceptional mechanical and chemical properties. The VAMWCNT films were prepared on a Ti substrate by a microwave plasma chemical vapour deposition method, and then oxidized and exfoliated by oxygen plasma etching (OPE) to produce graphene oxide (GO) at the VAMWCNT tips. The attachment of oxygen functional groups was found to be crucial for nHAp nucleation during electrodeposition. A thin layer of plate-like and needle-like nHAp with high crystallinity was formed without any need for thermal treatment. This composite (henceforth referred to as nHAp-VAMWCNT-GO) served as the scaffold for in vitro biomineralization when soaked in the SBF, resulting in the formation of both carbonate-rich and carbonate-poor globular-like nHAp. Different steps in the deposition of biological apatite onto VAMWCNT-GO and during the short-term biomineralization process were analysed. Due to their unique structure and properties, such nano-bio-composites may become useful in accelerating in vivo bone regeneration processes.
Nitrogen deposition and sensitive ecosystems: a case study from the San Francisco Bay Area
NASA Astrophysics Data System (ADS)
Weiss, S. B.
2001-12-01
Nitrogen deposition from urban smog can greatly affect local ecosystems. This paper examines a complex situation in the Santa Clara Valley, CA where N-deposition from existing, new, and proposed developments threatens an ecosystem supporting numerous rare, threatened, and endangered species. Grasslands on nutrient-poor serpentinitic soils are being invaded by nutrient-demanding introduced annual grasses, driven by dry N-deposition of about 10 kg ha-1 yr-1. These grass invasions threaten the native biodiversity of the serpentinitic grasslands, including the federally-protected Bay checkerspot butterfly. Additional NOx and NH3 sources planned for the region include a 600 MW natural gas fired power plant, industrial parks that may eventually draw 20,000 to 50,000 additional cars per day, 25,000 housing units, and associated highway improvements. Ongoing mitigation proposals include purchase and long-term management of hundreds of hectares of habitat. The situation is a model for understanding N-deposition from a scientific and policy viewpoint. Fundamental biogeochemical questions include: 1) What are the relative contributions of NOx and NH3 to increased N-deposition? NH3 slip from power plant NOx scrubbers can release more reactive nitrogen than is removed as NOx, and modern automobiles release NH3 in addition to NOx. 2) How are N-emissions transported, chemically modified, and deposited on the local ecosystems, and are these processes adequately captured in regulatory models? How do point sources differ from line sources such as a heavily traveled freeway? 3) What are the effects of chronic N-deposition on the ecosystem, and is there a critical load or a steady cumulative effect? 4) What are the effects of management such as fire, grazing, mowing on N-cycling and plant composition? Policy issues include: 1) What are the incremental impacts of individual projects relative to high background deposition, 2) What margin of safety should be built into modeling and
Hayes, Timothy S.; Cox, Dennis P.; Bliss, James D.; Piatak, Nadine M.; Seal, Robert R.
2015-01-01
This report contains a descriptive model of sediment-hosted stratabound copper (SSC) deposits that supersedes the model of Cox and others (2003). This model is for use in assessments of mineral resource potential. SSC deposits are the second most important sources of copper in the world behind porphyry copper deposits. Around 20 percent of the copper in the world is produced from this class of deposits. They are also the most important sources of cobalt in the world, and they are fourth among classes of ore deposits in production of silver. SSC deposits are the basis of the economies of three countries: Democratic Republic of Congo, Poland, and Zambia. This report provides a description of the key features of SSC deposits; it identifies their tectonic-sedimentary environments; it illustrates geochemical, geophysical, and geoenvironmental characteristics of SSC deposits; it reviews and evaluates hypotheses on how these deposits formed; it presents exploration and assessment guides; and it lists some gaps in our knowledge about the SSC deposits. A summary follows that provides overviews of many subjects concerning SSC deposits.
Code of Federal Regulations, 2013 CFR
2013-07-01
... deposition shall be taken in accordance with the Federal Rules of Civil Procedure, particularly Federal Rule... dismiss. (c) Notice of taking. Any depositions allowed by the Commission or Judge may be taken after 10... borne by the party at whose instance the deposition is taken. (e) Use of depositions. Depositions taken...
Code of Federal Regulations, 2012 CFR
2012-07-01
... deposition shall be taken in accordance with the Federal Rules of Civil Procedure, particularly Federal Rule... dismiss. (c) Notice of taking. Any depositions allowed by the Commission or Judge may be taken after 10... borne by the party at whose instance the deposition is taken. (e) Use of depositions. Depositions taken...
Code of Federal Regulations, 2011 CFR
2011-04-01
... 24 Housing and Urban Development 1 2011-04-01 2011-04-01 false Depositions. 26.20 Section 26.20... PROCEDURES Hearings Before Hearing Officers Discovery § 26.20 Depositions. (a) Taking oral deposition. A party may take the oral deposition of any person. Reasonable written notice of deposition shall be...
Code of Federal Regulations, 2010 CFR
2010-04-01
... 24 Housing and Urban Development 1 2010-04-01 2010-04-01 false Depositions. 26.20 Section 26.20... PROCEDURES Hearings Before Hearing Officers Discovery § 26.20 Depositions. (a) Taking oral deposition. A party may take the oral deposition of any person. Reasonable written notice of deposition shall be...