Study of cosmogenic activation above ground for the DarkSide-20k experiment

The activation of materials due to exposure to cosmic rays may become an important background source for experiments investigating rare event phenomena. DarkSide-20k, currently under construction at the Laboratori Nazionali del Gran Sasso, is a direct detection experiment for galactic dark matter particles, using a two-phase liquid-argon Time Projection Chamber (TPC) filled with 49.7 tonnes (active mass) of Underground Argon (UAr) depleted in 39Ar. Despite the outstanding capability of discriminating / background in argon TPCs, this background must be considered because of induced dead time or accidental coincidences mimicking dark-matter signals and it is relevant for low-threshold electron-counting measurements. Here, the cosmogenic activity of relevant long-lived radioisotopes induced in the experiment has been estimated to set requirements and procedures during preparation of the experiment and to check that it is not dominant over primordial radioactivity; particular attention has been paid to the activation of the 120 t of UAr used in DarkSide-20k. Expected exposures above ground and production rates, either measured or calculated, have been considered in detail. From the simulated counting rates in the detector due to cosmogenic isotopes, it is concluded that activation in copper and stainless steel is not problematic. The activity of 39Ar induced during extraction, purification and transport on surface is evaluated to be 2.8% of the activity measured in UAr by DarkSide-50 experiment, which used the same underground source, and thus considered acceptable. Other isotopes in the UAr such as 37Ar and 3H are shown not to be relevant due to short half-life and assumed purification methods

Latest results of dark matter detection with the DarkSide experiment

In this contribution the latest results of dark matter direct detection obtained by the DarkSide Collaboration are discussed. New limits on the scattering cross-section between dark matter particles and baryonic matter have been set. The results have been reached using the DarkSide-50 detector, a double-phase Time Projection Chamber (TPC) filled with 40Ar and installed at Laboratori Nazionali del Gran Sasso (LNGS). In 2018, the DarkSide Collaboration has performed three different types of analysis. The so-called high-mass analysis into the range between ∼ 10 GeV and ∼ 1000 GeV is discussed under the hypothesis of scattering between dark matter and Ar nuclei. The low-mass analysis, performed using the same hypothesis, extends the limit down to ∼1.8 GeV. Through a different hypothesis, that predicts dark matter scattering off the electrons inside of the Ar atom, it has been possible to set limits for sub-GeV dark matter masses

A quantitative enzyme-linked immunosorbent assay (ELISA) for the detection of anti-double-stranded DNA IgG antibodies

A detecção de anticorpos contra o ácido desoxirribonucleico (DNA) nativo (ds) é um dos critérios de classificação para o diagnóstico do lúpus eritematoso sistêmico (LES). Descrever uma técnica imunoenzimática enzyme-linked immunosorbent assay (ELISA) quantitativa para a detecção de anticorpos imunoglobulina da classe G (IgG) anti-DNAds. O desempenho da técnica ELISA foi avaliado utilizando o teste de imunofluorescência indireta com Crithidia luciliae (CLIFT) como referência. Anticorpos IgG anti-DNAds foram pesquisados por ELISA e CLIFT em amostras de soros de 127 pacientes com LES, 56 pacientes com outras doenças e 37 indivíduos sadios. O teste Q de Cochran foi utilizado para comparar as sensibilidades e as especificidades das reações, considerando diferenças significantes entre os testes quando p ≤ 0,05. A técnica ELISA apresentou sensibilidade de 92,9% e especificidade de 94,6%, enquanto a sensibilidade e a especificidade da técnica CLIFT foram de 85,8% e 100%, respectivamente. A técnica ELISA apresentou sensibilidade significativamente maior do que a obtida com a técnica CLIFT (p = 0,0027); esta apresentou especificidade significativamente maior do que a obtida com a técnica ELISA (p = 0,0253). A técnica ELISA apresentou excelentes resultados em termos de sensibilidade e especificidade, podendo ser útil em pesquisa e rotina diagnóstica. lúpus eritematoso sistêmico; anticorpos antinucleares; ensaio de imunoadsorção enzimática; técnica indireta de fluorescência para anticorpo552165169The detection of anti-double-stranded (ds) deoxyribonucleic acid (DNA) antibodies is one of the classification criteria for diagnosing systemic lupus erythematosus (SLE). To describe a quantitative enzyme-linked immunosorbent assay (ELISA) for detecting anti-dsDNA immunoglobulin class G (IgG) antibodies. The performance of ELISA was evaluated using the Crithidia luciliae indirect immunofluorescence test (CLIFT) as a reference. Anti-dsDNA IgG antibodies were screened by ELISA and CLIFT in serum samples from 127 patients with SLE, 56 patients with other diseases and 37 healthy persons. The Cochran Q test was used to compare the sensitivity and specificity of the reactions, with differences among the results being considered significant when p ≤ 0.05. ELISA had a sensitivity of 92.9% and a specificity of 94.6%, whereas the sensitivity and specificity of CLIFT were 85.8% and 100%, respectively. ELISA was significantly more sensitive than CLIFT (p = 0.0027), whereas CLIFT was significantly more specific than ELISA (p = 0.0253). ELISA showed excellent results in terms of sensitivity and specificity, with a potential use in research and routine diagnostic

Sensitivity To Guest-host Force Fields In Adsorption Equilibrium Of Cyclic Hydrocarbons In One-dimensional Molecular Sieve

We have investigated the effect of different guest-host force fields (united atom, UA; all-atom, AA; and anisotropic united atom, AUA) on the adsorption of cyclic hydrocarbon molecules in AlPO4-5 molecular sieve. Grand canonical Monte Carlo (GCMC) simulations of benzene, xylene and cyclohexane adsorption and positioning are carried out. The results suggest that the force field choice affects considerably the positioning of benzene and cyclohexane molecules while xylenes presented a smaller sensibility. The force fields difference of sensibilities among cyclical molecules seems to be associated with the critical geometric condition identified by Yashonath and Santikary denominated levitation effect. In this condition, the net forces on the guest due to the host is at a minimum, the levitation ratio () is close to unity and we have a weakly bound guest that can be easily moved from its balance position. Unlike xylene, that is only slightly affected by the choice of the force field, benzene and cyclohexane molecules in AlPO4-5 have such dimensions that result in levitation ratio () close to unity. These results point out to the care that should be taken in the choice of the force field when the guest-host size ratio is near the value defined for the levitation effect.3304/05/15437448Yashonath, S., Santikaryt, P., Diffusion of sorbates in zeolites Y and A: Novel dependence on sorbate size and strength of sorbate-zeolite interaction (1994) J. Phys. Chem, 98, p. 6368Fuchs, A.H., Cheetham, A.K., Adsorption of guest molecules in zeolitic materials: Computational aspects (2001) J. Phys. Chem. B, 105, p. 7375Kiselev, A.V., Du, P.Q., Molecular statistical calculation of the thermodynamic adsorption characteristics of zeolites using the atom-atom aproximation (1981) J. Chem. Soc. Faraday Trans. II, 77, p. 17Kiselev, A.V., Lopatkin, A.A., Shulga, A.A., Molecular statistical calculation of gas adsorption by silicalite (1985) Zeolites, 5, p. 261Smit, B., Siepmann, J.I., Computer simulations of the energetics and siting of n-alkanes in zeolites (1994) J. Phys. Chem, 98, p. 8442Siepmann, J.I., Karaborni, S., Smit, B., Simulating the critical behaviour of complex fluids (1993) Nature, 365, p. 330Macedonia, M.D., Maginn, E.J., A biased grand canonical Monte Carlo method for simulating adsorption using all-atom and branched united atom models (1999) Mol. Phys, 96, p. 1375Toxvaerd, S., Molecular dynamics calculation of the equation of state of alkanes (1990) J. Chem. Phys, 93, p. 4290Pellenq, R.J.-M., Tavitian, B., Espinat, D., Fuchs, A.H., Grand canonical Monte Carlo simulations of adsorption of polar and nonpolar molecules in NaY zeolite (1996) Langmuir, 12, p. 4768Kitagawa, T., Tsunekawa, T., Iwayama, K., Experimental and molecular simulation studies of adsorption and diffusion of cyclic hydrocarbons in silicalite-1 (1996) Microporous Mater, 7, p. 227Lachet, V., Boutin, A., Tavitian, B., Fuchs, A.H., Molecular simulation of p-xylene and m-xylene adsorption in Y zeolites. Single components and binary mixtures study (1999) Langmuir, 15, p. 8678Lachet, V., Boutin, A., Tavitian, B., Fuchs, A.H., Computational study of p-xylene/m-xylene mixtures adsorbed in NaY zeolite (1998) J. Phys. Chem. B, 102, p. 9224Snurr, R.Q., Bell, A.T., Theodorou, D.N., Prediction of adsorption of aromatic hydrocarbons from grand canonical Monte Carlo simulations with biased insertions (1993) J. Phys. Chem, 97, p. 13742Snurr, R.Q., Bell, A.T., Theodorou, D.N., Molecular simulations of low occupancy adsorption of aromatics in silicalite (1993) Proceedings from the Ninth International Zeolite Conference, 2, p. 71Lucena, S.M.P., Pereira, J.A.F.R., Cavalcante Jr., C.L., Structural analysis and adsorption sites of xylenes in AlPO4-5 and AlPO4-11 using molecular simulation (2006) Microporous Mesoporous Mater, 88, p. 135Lucena, S.M.P., Pereira, J.A.F.R., Cavalcante Jr., C.L., Orthoselectivity in aluminophosphate molecular sieves: A molecular simulation study (2006) Adsorption, 12, p. 425Demontis, P., Yashonath, S., Klein, M.L., Localization and mobility of benzene in sodium-Y zeolite by molecular dynamics calculations (1989) J. Phys. Chem, 93, p. 5016Auerbach, S.M., Bull, L.M., Henson, N.J., Metiu, H.I., Cheetham, A.K., Behavior of Benzene in Na-X and Na-Y Zeolites: Comparative study by 2H NMR and molecular mechanics (1996) J. Phys. Chem, 100, p. 5923Klein, H., Fuess, H., Schrimpf, G., Mobility of aromatic molecules in zeolite NaY by molecular dynamics simulation (1996) J. Phys. Chem, 100, p. 11101Clark, L.A., Snurr, R.Q., Adsorption isotherm sensitivity to small changes in zeolite structure (1999) Chem. Phys. Lett, 308, p. 155Fox, J.P., Rooy, V., Bates, S.P., Simulating the adsorption of linear, branched and cyclic alkanes in silicalite-1 and AlP04-5 (2004) Microporous Mesoporous Mater, 69, p. 9Gupta, A., Clark, L.A., Snurr, R.Q., Grand canonical Monte Carlo simulations of nonrigid molecules: Siting and segregation in silicalite zeolite (2000) Langmuir, 16, p. 3910Schenk, M., Smit, B., Maesen, T.L.M., Vlugt, T.J.H., Molecular simulations of the adsorption of cycloalkanes in MFI-type silica (2005) Phys. Chem. Chem. Phys, 7, p. 2622Newalkar, B.L., Jasra, R.V., Kamath, V., Bhat, S.G.T., Sorption of C6 alkanes in aluminophosphate molecular sieve, AlPO4-5 (1999) Adsorption, 5, p. 345Chiang, A.S.T., Lee, C.K., Chang, Z.H., Adsorption and diffusion of aromatics in AlPO4-5 (1991) Zeolites, 11, p. 380Ungerer, P., Beauvais, C., Delhommelle, J., Boutin, A., Rousseau, B., Fuchs, A.H., Optimization of the anisotropic united atoms intermolecular potential for n-alkanes (2000) J. Chem. Phys, 112, p. 5499Contreras-Camacho, R.O., Ungerer, P., Boutin, A., Mackie, A.D., Optimized intermolecular potential for aromatic hydrocarbons based on anisotropic united atoms. 1. Benzene (2004) J. Phys. Chem. B, 108, p. 14109Contreras-Camacho, R.O., Ungerer, P., Ahunbay, M.G., Lachet, V., Perez-Pellitero, J., Mackie, A.D., Optimized intermolecular potential for aromatic hydrocarbons based on anisotropic united atoms. 2. Alkylbenzenes and styrene (2004) J. Phys. Chem. B, 108, p. 14115Bourasseau, E., Ungerer, P., Boutin, A., Prediction of equilibrium properties of cyclic alkanes by Monte Carlo simulations new anisotropic united atoms intermolecular potentials new transfer bias method (2002) J. Phys. Chem. B, 106, p. 5483Bennet, J.M., Cohen, J.P., Flanigen, E.M., Pluth, J.J., Smith, J.V., Crystal structure of tetrapropylammonium hydroxide-aluminum phosphate (1983) ACS Symp. Ser, 218 (5), p. 109Jorgensen, W.L., Severance, D.L., Aromatic-aromatic interactions: Free energy profiles for the benzene dimer in water, chloroform, and liquid benzene (1990) J. Am. Chem. Soc, 112, p. 4768Mayo, S.L., Olafson, B.D., Goddard, W.A., DREIDING: A generic force field for molecular simulations (1990) J. Phys. Chem, 94, p. 8897Rodriguez, A.L., Vega, C., Freire, J.J., Lago, S., Potential parameters of methyl and methylene obtained from second virial coefficients of n-alkanes (1991) Mol. Phys, 73 (3), p. 691W.L. Jorgensen, E.R. Laird, T.B. Nguyen, J. Tirado-Rives. Monte Carlo simulations of pure liquid substituted benzenes with OPLS potential functions. J. Comp. Chem., 14, 206 (1993)Bhide, S.Y., Yashonath, S., Structure and dynamics of benzene in one-dimensional channels (2000) J. Phys. Chem. B, 104, p. 11977Jänchen, J., Stach, H., Uytterhoeven, L., Mortier, W.J., Influence of the framework density and effective electronegativity of silica and aluminophosphate molecular sieves on the heat of adsorption od nonpolar molecules (1996) J. Phys. Chem, 100, p. 12489Pascual, P., Ungerer, P., Tavitian, B., Pernot, P., Boutin, A., Development of a transferable guest-host force field for adsorption of hydrocarbons in zeolites. I. Reinvestigation of alkanes adsorption in silicalite by grand canonical Monte Carlo simulation (2003) Phys. Chem. Chem. Phys, 5, p. 3684Pascual, P., Kirsch, H., Boutin, A., Paillaud, J.-L., Soulard, M., Tavitian, B., Faye, D., Fuchs, A.H., Adsorption of various hydrocarbons in siliceous zeolites: A molecular simulation study (2005) Adsorption, 11, p. 379Karasawa, N., Goddard III, W.A., Acceleration of convergence for lattice sums (1989) J. Phys. Chem, 93, p. 7320Frenkel, D., Smit, B., (2002) Understanding Molecular Simulation, , Academic Press, New YorkVitale, G., Mellot, C.F., Cheetham, A.K., Localization of adsorbed cyclohexane in the acid form of zeolite Y. A powder neutron diffraction and computational study (1997) J. Phys. Chem. B, 101, p. 9886Boutin, A.P., Roland, J.-M., Nicholson, D., Molecular simulation of the stepped adsorption isotherm of methane in AlPO4-5 (1994) Chem. Phys. Lett, 219, p. 484Sorption, invoked from Cerius2 v. 4.6, Accelrys Inc., San Diego (2001)McCullen, S.B., Reischman, P.T., Olson, D.H., Hexane and benzene adsorption by aluminophosphates and SSZ-24: The effect of pore size and molecular sieve composition (1993) Zeolites, 13, p. 640Ghorai, P.K., Yashonath, S., Demontis, P., Suffritti, G.B., Diffusion anomaly as a function of molecular length of linear molecules: Levitation effect (2003) J. Am. Chem. Soc, 125, p. 7116Bandyopadhyay, S., Yashonath, S., Diffusion anomaly in silicalite and VPI-5 from molecular dynamics simulations (1995) J. Phys. Chem, 99, p. 4286Breck, D.W., (1974) Zeolite Molecular Sieve, p. 636. , John Wiley & sons, pWebster, C.E., Drago, R.S., Zerner, M.C., Molecular dimensions for adsorptives (1998) J. Am. Chem. Soc, 120, p. 5509Maris, T., Vlugt, T.J.H., Smit, B., Simulation of alkane adsorption in the aluminophosphate molecular sieve AlPO4-5 (1998) J. Phys. Chem. B, 102, p. 718

REMOVAL OF COPPER ELECTROLYTE CONTAMINANTS BY ADSORPTION

Abstract - Selective adsorbents have become frequently used in industrial processes. Recent studies have shown the possibility of using adsorption to separate copper refinery electrolyte contaminants, with better results than those obtained with conventional techniques. During copper electrorefinning, many impurities may be found as dissolved metals present in the anode slime which forms on the electrode surface, accumulated in the electrolyte or incorporated into the refined copper on the cathode by deposition. In this study, synthetic zeolites, chelating resins and activated carbons were tested as adsorbents to select the best adsorbent performance, as well as the best operating temperature for the process. The experimental method applied was the finite bath, which consists in bringing the adsorbent into contact with a finite volume of electrolyte while controlling the temperature. The concentration of metals in the liquid phase was continuously monitored by atomic absorption spectrophotometry (AAS