Reduction Of Trace Quantities Of Chromium (vi) By Strong Acids

The chemical behavior of Cr(VI) at low concentrations (10-4 to 10-7 mol L-1) in several strong acids was studied using high specific activity 51Cr(VI) as a tracer. The speciation of the products from these systems was carried out by ion exchange chromatography with stepwise elution. The results show that trace quantities of Cr(VI), monitored by means of radiochromium (51Cr), are reduced in the presence of mineral acids such as perchloric, hydrochloric, hydrofluoric, sulfuric, nitric and trifluoromethanesulfonic acids, even in the absence of conventional reducing agents, producing different measureable Cr(III) species, depending on the acid anion. Detailed studies of the reduction of low concentrations of Cr(VI) with nitric acid have shown that the relative rate of reduction increases as the concentration of the acid increases or as the concentration of the Cr(VI) decreases.1515865Weeks, M.E., Leicester, H.M., (1968) Discovery of the Elements, 7th Ed., , American Chemical Society: EastonFeigl, F., (1943) J. Chem. Educ., 20, p. 240Westheimer, F.H., (1949) Chem. Rev., 45, p. 419Wiberg, K.B., (1965) Oxidation in Organic Chemistry, Part A, , Academic: New YorkCainelli, G., Cardillo, G., (1984) Chromium Oxidations in Organic Chemistry, , Springer-Verlag: BerlinDas, A.K., (2001) Oxid. Commun., 24, p. 321Beattie, J.K., Haight Jr., G.P., (1972) Prog. Inorg. Chem., 17, p. 93Fendorf, S., Wienlinga, B.W., Hansel, C.M., (2000) Int. Geol. Rev., 42, p. 691Smith, G.F., (1934) Ind. Eng. Chem. Anal. Edition, 6, p. 229Bobtelsky, M., Glasner, A., (1948) J. Chem. Soc., p. 1376Ho, W.-H., (1979) Proc. Natl. Sci. Counc. ROC, 4, p. 1Archundia, C., Collins, C.H., Collins, K.E., (1990) J. Radioanal. Nucl. Chem. Lett., 146, p. 49Archundia, C., Bonato, P.S., Lugo Rivera, J.F., Mascioli, L.C., Collins, C.H., Collins, K.E., (1993) Sci. Total Environ., 130-131, p. 231Archundia, C., Lugo Rivera, J.F., Collins, K.E., Collins, C.H., (1995) J. Radioanal. Nucl. Chem. Art., 195, p. 363Pezzin, S.H., Archundia, C., Collins, C.H., Collins, K.E., (1997) Radiochim. Acta, 77, p. 91Khan, Z., Hashmi, A.A., Din, K., (1998) Transition Met. Chem., 23, p. 147Pezzin, S.H., Collins, C.H., Archundia, C., Collins, K.E., (1998) J. Radioanal. Nucl. Chem., 236, p. 209Pezzin, S.H., Archundia, C., Collins, K.E., Collins, C.H., (2000) Czech. J. Phys., 50, p. 315Pezzin, S.H., Collins, C.H., Collins, K.E., (2000) Proceedings of the National Meeting on Nuclear Applications, , Rio de Janeiro, Brazil, CD-ROM, paper no. 61Pavel, J., Kliment, J., Stoerk, S., Suter, O., (1985) Fresenius Z. Anal. Chem., 321, p. 587Stollenwerk, K.G., Grove, D.B., (1985) J. Environ. Qual., 14, p. 386Gil, M., Escolar, D., Iza, N., Montero, J.L., (1986) Appl. Spectrosc., 40, p. 1156Tong, J.Y.P., King, E.L., (1960) J. Am. Chem. Soc., 82, p. 3805Espenson, J.H., King, E.L., (1963) J. Am. Chem. Soc., 85, p. 3328Khan, Z., Din, K., (2001) Indian J. Chem., 40 A, p. 528Haight Jr., G.P., Richardson, D.C., Coburn, N.H., (1964) Inorg. Chem., 3, p. 1777Espenson, J.H., (1964) J. Am. Chem. Soc., 86, p. 5101Pezzin, S.H., Collins, C.H., Collins, K.E., (2001) Radiochim. Acta, 89, p. 845House, D.A., (1994) Mechanisms of Inorganic and Organometallic Reactions, p. 97. , Twigg, M. V., ed.Plenum: New YorkSena, M.M., Scarminio, I.S., Collins, K.E., Collins, C.H., (2000) Talanta, 53, p. 453Cruywagen, J.J., Heyns, J.B.B., Rohwer, E.A., (1998) Polyhedron, 17, p. 1741Brito, F., Ascanio, J., Mateo, S., Hernandez, C., Araujo, L., Gili, P., MartinZarza, P., Mederos, A., (1997) Polyhedron, 16, p. 3835Nriagu, J.O., Nieboer, E., (1988) Chromium in the Natural and Human Environments, , Wiley: New YorkCollins, C.H., Pezzin, S.H., Lugo Rivera, J.F., Bonato, P.S., Windmöller, C., Archundia, C., Collins, K.E., (1997) J. Chromatogr. A, 789, p. 469Marques, M.J., Salvador, A., Morales-Rubio, A., De La Guardia, M., (2000) Fresenius. J. Anal. Chem., 367, p. 601Collins, K.E., Bonato, P.S., Archundia, C., De Queiroz, M.E.L.R., Collins, C.H., (1988) Chromatographia, 26, p. 160Collins, C.H., Collins, K.E., Ackerhalt, R.E., (1971) J. Radioanal. Chem., 8, p. 263De Andrade, J.C., Collins, K.E., (1981) Quim. Nova, 4, p. 89Gates, H.S., King, E.L., (1958) J. Am. Chem. Soc., 80, p. 5011Autenrieth, W., (1902) Ber. Deutsch. Chem. Ges., 35, p. 2057Krauss, H.L., Leder, M., Münster, G., (1963) Chem. Ber., 96, p. 3008Finholt, J.E., Ph.D. Thesis, Lawrence Radiation Laboratory Report UCRL-8879, University of California, Berkeley, 1960Collins, C.H., Lanças, F.M., (1982) Radiochem. Radioanal. Letters, 19, p. 117Jones, K.M., Bjerrum, J., (1965) Acta Chem. Scand., 19, p. 974Aggett, J., Udy, D.J., (1970) J. Inorg. Nucl. Chem., 32, p. 2802Chaabouni, M., Chausse, T., Pascal, J.L., Potier, J., (1980) J. Chem. Res. (S), 72Archundia, C., Collins, C.H., Collins, K.E., (1988) Proceedings of the Second General Congress on Nuclear Energy, 2, p. 415. , Rio de Janeiro, BrazilStünzi, H., Marty, W., (1983) Inorg. Chem., 22, p. 2145(1985) Chemical Analysis of Metals and Metal-Bearing Ores, , Annual Book of ASTM Standards, Section 3, Vol.03.05, American Society for Testing and MaterialsPhiladelphiaOttaway, J.M., Fell, G.S., (1986) Pure Appl. Chem., 58, p. 170

Hydrogen-Helium Mixtures at High Pressure

The properties of hydrogen-helium mixtures at high pressure are crucial to address important questions about the interior of Giant planets e.g. whether Jupiter has a rocky core and did it emerge via core accretion? Using path integral Monte Carlo simulations, we study the properties of these mixtures as a function of temperature, density and composition. The equation of state is calculated and compared to chemical models. We probe the accuracy of the ideal mixing approximation commonly used in such models. Finally, we discuss the structure of the liquid in terms of pair correlation functions.Comment: Proceedings article of the 5th Conference on Cryocrystals and Quantum Crystals in Wroclaw, Poland, submitted to J. Low. Temp. Phys. (2004

Decision making and risk management in adventure sports coaching

Adventure sport coaches practice in environments that are dynamic and high in risk, both perceived and actual. The inherent risks associated with these activities, individuals’ responses and the optimal exploitation of both combine to make the processes of risk management more complex and hazardous than the traditional sports where risk management is focused almost exclusively on minimization. Pivotal to this process is the adventure sports coaches’ ability to make effective judgments regarding levels of risk, potential benefits and possible consequences. The exact nature of this decision making process should form the basis of coaching practice and coach education in this complex and dynamic field. This positional paper examines decision making by the adventure sports coach in these complex, challenging environments and seeks to stimulate debate whilst offering a basis for future research into this topic

Nonperturbative renormalization group approach to frustrated magnets

This article is devoted to the study of the critical properties of classical XY and Heisenberg frustrated magnets in three dimensions. We first analyze the experimental and numerical situations. We show that the unusual behaviors encountered in these systems, typically nonuniversal scaling, are hardly compatible with the hypothesis of a second order phase transition. We then review the various perturbative and early nonperturbative approaches used to investigate these systems. We argue that none of them provides a completely satisfactory description of the three-dimensional critical behavior. We then recall the principles of the nonperturbative approach - the effective average action method - that we have used to investigate the physics of frustrated magnets. First, we recall the treatment of the unfrustrated - O(N) - case with this method. This allows to introduce its technical aspects. Then, we show how this method unables to clarify most of the problems encountered in the previous theoretical descriptions of frustrated magnets. Firstly, we get an explanation of the long-standing mismatch between different perturbative approaches which consists in a nonperturbative mechanism of annihilation of fixed points between two and three dimensions. Secondly, we get a coherent picture of the physics of frustrated magnets in qualitative and (semi-) quantitative agreement with the numerical and experimental results. The central feature that emerges from our approach is the existence of scaling behaviors without fixed or pseudo-fixed point and that relies on a slowing-down of the renormalization group flow in a whole region in the coupling constants space. This phenomenon allows to explain the occurence of generic weak first order behaviors and to understand the absence of universality in the critical behavior of frustrated magnets.Comment: 58 pages, 15 PS figure

Measurement of D*+/- meson production in jets from pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

This paper reports a measurement of D*+/- meson production in jets from proton-proton collisions at a center-of-mass energy of sqrt(s) = 7 TeV at the CERN Large Hadron Collider. The measurement is based on a data sample recorded with the ATLAS detector with an integrated luminosity of 0.30 pb^-1 for jets with transverse momentum between 25 and 70 GeV in the pseudorapidity range |eta| < 2.5. D*+/- mesons found in jets are fully reconstructed in the decay chain: D*+ -> D0pi+, D0 -> K-pi+, and its charge conjugate. The production rate is found to be N(D*+/-)/N(jet) = 0.025 +/- 0.001(stat.) +/- 0.004(syst.) for D*+/- mesons that carry a fraction z of the jet momentum in the range 0.3 < z < 1. Monte Carlo predictions fail to describe the data at small values of z, and this is most marked at low jet transverse momentum.Comment: 10 pages plus author list (22 pages total), 5 figures, 1 table, matches published version in Physical Review

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Search for supersymmetry in final states with jets, missing transverse momentum and one isolated lepton in sqrt{s} = 7 TeV pp collisions using 1 fb-1 of ATLAS data

We present an update of a search for supersymmetry in final states containing jets, missing transverse momentum, and one isolated electron or muon, using 1.04 fb^-1 of proton-proton collision data at sqrt{s} = 7 TeV recorded by the ATLAS experiment at the LHC in the first half of 2011. The analysis is carried out in four distinct signal regions with either three or four jets and variations on the (missing) transverse momentum cuts, resulting in optimized limits for various supersymmetry models. No excess above the standard model background expectation is observed. Limits are set on the visible cross-section of new physics within the kinematic requirements of the search. The results are interpreted as limits on the parameters of the minimal supergravity framework, limits on cross-sections of simplified models with specific squark and gluino decay modes, and limits on parameters of a model with bilinear R-parity violation.Comment: 18 pages plus author list (30 pages total), 9 figures, 4 tables, final version to appear in Physical Review

Reducing heterotic M-theory to five dimensional supergravity on a manifold with boundary

This paper constructs the reduction of heterotic $M$-theory in eleven dimensions to a supergravity model on a manifold with boundary in five dimensions using a Calabi-Yau three-fold. New results are presented for the boundary terms in the action and for the boundary conditions on the bulk fields. Some general features of dualisation on a manifold with boundary are used to explain the origin of some topological terms in the action. The effect of gaugino condensation on the fermion boundary conditions leads to a `twist' in the chirality of the gravitino which can provide an uplifting mechanism in the vacuum energy to cancel the cosmological constant after moduli stabilisation.Comment: 16 pages, RevTe

Measurement of tau polarization in W->taunu decays with the ATLAS detector in pp collisions at sqrt(s) = 7 TeV

In this paper, a measurement of tau polarization in W->taunu decays is presented. It is measured from the energies of the decay products in hadronic tau decays with a single final state charged particle. The data, corresponding to an integrated luminosity of 24 pb^-1, were collected by the ATLAS experiment at the Large Hadron Collider in 2010. The measured value of the tau polarization is Ptau = -1.06 +/- 0.04 (stat) + 0.05 (syst) - 0.07 (syst), in agreement with the Standard Model prediction, and is consistent with a physically allowed 95% CL interval [-1,-0.91]. Measurements of tau polarization have not previously been made at hadron colliders.Comment: 10 pages plus author list (25 pages total), 4 figures, 4 tables, revised author list, matches published EPJC versio

Designing a broad-spectrum integrative approach for cancer prevention and treatment

Targeted therapies and the consequent adoption of "personalized" oncology have achieved notablesuccesses in some cancers; however, significant problems remain with this approach. Many targetedtherapies are highly toxic, costs are extremely high, and most patients experience relapse after a fewdisease-free months. Relapses arise from genetic heterogeneity in tumors, which harbor therapy-resistantimmortalized cells that have adopted alternate and compensatory pathways (i.e., pathways that are notreliant upon the same mechanisms as those which have been targeted). To address these limitations, aninternational task force of 180 scientists was assembled to explore the concept of a low-toxicity "broad-spectrum" therapeutic approach that could simultaneously target many key pathways and mechanisms. Using cancer hallmark phenotypes and the tumor microenvironment to account for the various aspectsof relevant cancer biology, interdisciplinary teams reviewed each hallmark area and nominated a widerange of high-priority targets (74 in total) that could be modified to improve patient outcomes. For thesetargets, corresponding low-toxicity therapeutic approaches were then suggested, many of which werephytochemicals. Proposed actions on each target and all of the approaches were further reviewed forknown effects on other hallmark areas and the tumor microenvironment. Potential contrary or procar-cinogenic effects were found for 3.9% of the relationships between targets and hallmarks, and mixedevidence of complementary and contrary relationships was found for 7.1%. Approximately 67% of therelationships revealed potentially complementary effects, and the remainder had no known relationship. Among the approaches, 1.1% had contrary, 2.8% had mixed and 62.1% had complementary relationships. These results suggest that a broad-spectrum approach should be feasible from a safety standpoint. Thisnovel approach has potential to be relatively inexpensive, it should help us address stages and types ofcancer that lack conventional treatment, and it may reduce relapse risks. A proposed agenda for futureresearch is offered