The geometric algebra of Fierz identities in arbitrary dimensions and signatures

We use geometric algebra techniques to give a synthetic and computationally efficient approach to Fierz identities in arbitrary dimensions and signatures, thus generalizing previous work. Our approach leads to a formulation which displays the underlying real, complex or quaternionic structure in an explicit and conceptually clear manner and is amenable to implementation in various symbolic computation systems. We illustrate our methods and results with a few examples which display the basic features of the three classes of pin representations governing the structure of such identities in various dimensions and signatures.Comment: 77 pages; version published in JHEP in 201

Flexible uretero- renoscopy for intrarenal calculi. Initial experience of a single centre. Outcome analysis

Clinica Endoplus, Cluj Napoca, Romania, Al VI-lea Congres de Urologie, Dializă şi Transplant Renal din Republica Moldova cu participare internaţională (21-23 octombrie 2015)INTRODUCERE cu privire la rata de succes (stone free rate-SFR) şi rata Scopul acestui studiu a fost să evaluăm rezultatele clinicii complicaţiilor (RC). noastre în uretero-renoscopia flexibila pentru calculii renali.Introduction Aim of this study was to evaluate the outcome of flexible uretero- renoscopy treatment for renal stones of a single surgeon, with regard to primary stone-free rates (SFR) and complication rates (CR) in a single center

Graphene oxide as a catalyst for the diastereoselective transfer hydrogenation in the synthesis of prostaglandin derivatives

[EN] Modification of GO by organic molecules changes its catalytic activity in the hydrogen transfer from i-propanol to enones, affecting the selectivity to allyl alcohol and diastereoselectivity to the resulting stereoisomers. It is noteworthy the system does not contain metals and is recyclable.Coman, SM.; Podolean, I.; Tudorache, M.; Cojocaru, B.; Parvulescu, VI.; Puche Panadero, M.; García Gómez, H. (2017). Graphene oxide as a catalyst for the diastereoselective transfer hydrogenation in the synthesis of prostaglandin derivatives. Chemical Communications. 53(74):10271-10274. doi:10.1039/c7cc05105kS1027110274537

N-Doped graphene as a metal-free catalyst for glucose oxidation to succinic acid

[EN] N-Containing graphenes obtained either by simultaneous amination and reduction of graphene oxide or by pyrolysis of chitosan under an inert atmosphere have been found to act as catalysts for the selective wet oxidation of glucose to succinic acid. Selectivity values over 60% at complete glucose conversion have been achieved by performing the reaction at 160 degrees C and 18 atm O-2 pressure for 20 h. This activity has been attributed to graphenic-type N atoms on graphene. The active N-containing graphene catalysts were used four times without observing a decrease in conversion and selectivity of the process. A mechanism having tartaric and fumaric acids as key intermediates is proposed.Financial support by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa, Grapas and CTQ2015-69153-CO2-R1) and Generalitat Valenciana (Prometeo 2013-014) is gratefully acknowledged. Prof. Simona M. Coman kindly acknowledges UEFISCDI for financial support (project PN-II-PT-PCCA-2013-4-1090, Nr. 44/2014). Cristina Bucur acknowledges Core Programme, Project PN-480103/2016.Rizescu, C.; Podolean, I.; Albero-Sancho, J.; Parvulescu, VI.; Coman, SM.; Bucur, C.; Puche Panadero, M.... (2017). N-Doped graphene as a metal-free catalyst for glucose oxidation to succinic acid. Green Chemistry. 19(8):1999-2005. https://doi.org/10.1039/C7GC00473GS19992005198Alonso, D. M., Wettstein, S. G., & Dumesic, J. A. (2012). Bimetallic catalysts for upgrading of biomass to fuels and chemicals. Chemical Society Reviews, 41(24), 8075. doi:10.1039/c2cs35188aCherubini, F. (2010). The biorefinery concept: Using biomass instead of oil for producing energy and chemicals. Energy Conversion and Management, 51(7), 1412-1421. doi:10.1016/j.enconman.2010.01.015Christensen, C. H., Rass-Hansen, J., Marsden, C. C., Taarning, E., & Egeblad, K. (2008). The Renewable Chemicals Industry. 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Chemical Reviews, 110(6), 3552-3599. doi:10.1021/cr900354uPodolean, I., Rizescu, C., Bala, C., Rotariu, L., Parvulescu, V. I., Coman, S. M., & Garcia, H. (2016). Unprecedented Catalytic Wet Oxidation of Glucose to Succinic Acid Induced by the Addition ofn-Butylamine to a RuIIICatalyst. ChemSusChem, 9(17), 2307-2311. doi:10.1002/cssc.201600474Huang, C., Li, C., & Shi, G. (2012). Graphene based catalysts. Energy & Environmental Science, 5(10), 8848. doi:10.1039/c2ee22238hNavalon, S., Dhakshinamoorthy, A., Alvaro, M., & Garcia, H. (2014). Carbocatalysis by Graphene-Based Materials. Chemical Reviews, 114(12), 6179-6212. doi:10.1021/cr4007347Su, D. S., Perathoner, S., & Centi, G. (2013). Nanocarbons for the Development of Advanced Catalysts. Chemical Reviews, 113(8), 5782-5816. doi:10.1021/cr300367dDhakshinamoorthy, A., Primo, A., Concepcion, P., Alvaro, M., & Garcia, H. (2013). Doped Graphene as a Metal-Free Carbocatalyst for the Selective Aerobic Oxidation of Benzylic Hydrocarbons, Cyclooctane and Styrene. Chemistry - A European Journal, 19(23), 7547-7554. doi:10.1002/chem.201300653Huang, H., Huang, J., Liu, Y.-M., He, H.-Y., Cao, Y., & Fan, K.-N. (2012). Graphite oxide as an efficient and durable metal-free catalyst for aerobic oxidative coupling of amines to imines. Green Chemistry, 14(4), 930. doi:10.1039/c2gc16681jLi, X.-H., Chen, J.-S., Wang, X., Sun, J., & Antonietti, M. (2011). Metal-Free Activation of Dioxygen by Graphene/g-C3N4Nanocomposites: Functional Dyads for Selective Oxidation of Saturated Hydrocarbons. Journal of the American Chemical Society, 133(21), 8074-8077. doi:10.1021/ja200997aSun, H., Wang, Y., Liu, S., Ge, L., Wang, L., Zhu, Z., & Wang, S. (2013). Facile synthesis of nitrogen doped reduced graphene oxide as a superior metal-free catalyst for oxidation. Chemical Communications, 49(85), 9914. doi:10.1039/c3cc43401jYang, J.-H., Sun, G., Gao, Y., Zhao, H., Tang, P., Tan, J., … Ma, D. (2013). Direct catalytic oxidation of benzene to phenol over metal-free graphene-based catalyst. Energy & Environmental Science, 6(3), 793. doi:10.1039/c3ee23623dRocha, R. P., Gonçalves, A. G., Pastrana-Martínez, L. M., Bordoni, B. C., Soares, O. S. G. P., Órfão, J. J. M., … Pereira, M. F. R. (2015). Nitrogen-doped graphene-based materials for advanced oxidation processes. Catalysis Today, 249, 192-198. doi:10.1016/j.cattod.2014.10.046Wang, Y., Xie, Y., Sun, H., Xiao, J., Cao, H., & Wang, S. (2016). Efficient Catalytic Ozonation over Reduced Graphene Oxide for p-Hydroxylbenzoic Acid (PHBA) Destruction: Active Site and Mechanism. ACS Applied Materials & Interfaces, 8(15), 9710-9720. doi:10.1021/acsami.6b01175Duan, X., Su, C., Zhou, L., Sun, H., Suvorova, A., Odedairo, T., … Wang, S. (2016). Surface controlled generation of reactive radicals from persulfate by carbocatalysis on nanodiamonds. Applied Catalysis B: Environmental, 194, 7-15. doi:10.1016/j.apcatb.2016.04.043Kang, J., Duan, X., Zhou, L., Sun, H., Tadé, M. O., & Wang, S. (2016). Carbocatalytic activation of persulfate for removal of antibiotics in water solutions. Chemical Engineering Journal, 288, 399-405. doi:10.1016/j.cej.2015.12.040Sun, H., Kwan, C., Suvorova, A., Ang, H. M., Tadé, M. O., & Wang, S. (2014). Catalytic oxidation of organic pollutants on pristine and surface nitrogen-modified carbon nanotubes with sulfate radicals. Applied Catalysis B: Environmental, 154-155, 134-141. doi:10.1016/j.apcatb.2014.02.012Wang, X., Qin, Y., Zhu, L., & Tang, H. (2015). Nitrogen-Doped Reduced Graphene Oxide as a Bifunctional Material for Removing Bisphenols: Synergistic Effect between Adsorption and Catalysis. Environmental Science & Technology, 49(11), 6855-6864. doi:10.1021/acs.est.5b01059Lai, L., Potts, J. 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The Journal of Physical Chemistry Letters, 8(1), 264-278. doi:10.1021/acs.jpclett.6b0199

Performance of the Two Aerogel Cherenkov Detectors of the JLab Hall A Hadron Spectrometer

We report on the design and commissioning of two silica aerogel Cherenkov detectors with different refractive indices. In particular, extraordinary performance in terms of the number of detected photoelectrons was achieved through an appropriate choice of PMT type and reflector, along with some design considerations. After four years of operation, the number of detected photoelectrons was found to be noticeably reduced in both detectors as a result of contamination, yellowing, of the aerogel material. Along with the details of the set-up, we illustrate the characteristics of the detectors during different time periods and the probable causes of the contamination. In particular we show that the replacement of the contaminated aerogel and parts of the reflecting material has almost restored the initial performance of the detectors.Comment: 18 pages, 9 Figures, 4 Tables, 44 Reference

Nitrogen-doped graphene as metal free basic catalyst for coupling reactions

[EN] N-doped defective graphene [(N)G] obtained by pyrolysis at 900 degrees C of chitosan contains about 3.7% of residual N atoms, distributed as pyridinic, pyrrolic and graphitic N atoms. It has been found that (N)G acts as basic catalyst promoting two classical C-C bond forming nucleophilic additions in organic chemistry, such as the Michael and the Henry additions. Computational calculations at DFT level of models corresponding to the various N atoms leads to the conclusion that N atoms are more stable at the periphery of the graphene sheets and that H adsorption on these sites is a suitable descriptor to correlate with the catalytic activity of the various sites. According to these calculations the most active sites are pyridinic N atoms at zig-zag edges of the sheets. In addition, N as dopant changes the reactivity of the neigh. bour C atoms. Water was found a suitable solvent to achieve high conversions in both reactions. In this solvent the initial distribution of N atoms is affected due to the easy protonation of the N-py to N-pyH sites. As an effect, C edge sites adjacent at N-PyH with an appropriate reactivity towards the alpha-C-H bond breaking are formed. The present results show the general activity of N-doped graphene as base catalysts and illustrate the potential of carbocatalysis to promote reactions of general interest in organic synthesis. (C) 2019 Elsevier Inc. All rights reserved.This work was supported by UEFISCDI (PN-III-P4-ID-PCE-2016-0146. nr. 121/2017 and project number PN-III-P1-1.1-TE-2016-2191. nr. 89/2018). Financial support by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa and CTQ2015-69653-CO2-R1) and Generalitat Valenciana (Prometeo 2017-083) is gratefully acknowledged. A.P thanks the Spanish Ministry of Science and Innovation for a Ramon y Cajal research associate contract.Candu, N.; Man, I.; Andrada, S.; Cojocaru, B.; Coman, SM.; Bucur, C.; Primo Arnau, AM.... (2019). Nitrogen-doped graphene as metal free basic catalyst for coupling reactions. Journal of Catalysis. 376:238-247. https://doi.org/10.1016/j.jcat.2019.07.011S23824737

Proton G_E/G_M from beam-target asymmetry

The ratio of the proton's electric to magnetic form factor, G_E/G_M, can be extracted in elastic electron-proton scattering by measuring either cross sections, beam-target asymmetry or recoil polarization. Separate determinations of G_E/G_M by cross sections and recoil polarization observables disagree for Q^2 > 1 (GeV/c)^2. Measurement by a third technique might uncover an unknown systematic error in either of the previous measurements. The beam-target asymmetry has been measured for elastic electron-proton scattering at Q^2 = 1.51 (GeV/c)^2 for target spin orientation aligned perpendicular to the beam momentum direction. This is the largest Q^2 at which G_E/G_M has been determined by a beam-target asymmetry experiment. The result, \muG_E/G_M = 0.884 +/- 0.027 +/- 0.029, is compared to previous world data.Comment: 8 pages, 6 figures, Updated to be version published in Physical Review

Measurement of the Electric Form Factor of the Neutron at Q^2=0.5 and 1.0 (GeV/c)^2

The electric form factor of the neutron was determined from measurements of the \vec{d}(\vec{e},e' n)p reaction for quasielastic kinematics. Polarized electrons were scattered off a polarized deuterated ammonia target in which the deuteron polarization was perpendicular to the momentum transfer. The scattered electrons were detected in a magnetic spectrometer in coincidence with neutrons in a large solid angle detector. We find G_E^n = 0.0526 +/- 0.0033 (stat) +/- 0.0026 (sys) and 0.0454 +/- 0.0054 +/- 0.0037 at Q^2 = 0.5 and 1.0 (GeV/c)^2, respectively.Comment: 5 pages, 2 figures, as publishe

Approximating Mexican highways with slime mould

Plasmodium of Physarum polycephalum is a single cell visible by unaided eye. During its foraging behavior the cell spans spatially distributed sources of nutrients with a protoplasmic network. Geometrical structure of the protoplasmic networks allows the plasmodium to optimize transport of nutrients between remote parts of its body. Assuming major Mexican cities are sources of nutrients how much structure of Physarum protoplasmic network correspond to structure of Mexican Federal highway network? To find an answer undertook a series of laboratory experiments with living Physarum polycephalum. We represent geographical locations of major cities by oat flakes, place a piece of plasmodium in Mexico city area, record the plasmodium's foraging behavior and extract topology of nutrient transport networks. Results of our experiments show that the protoplasmic network formed by Physarum is isomorphic, subject to limitations imposed, to a network of principle highways. Ideas and results of the paper may contribute towards future developments in bio-inspired road planning

Exclusive electroproduction of K+ Lambda and K+ Sigma^0 final states at Q^2 = 0.030-0.055 (GeV/c)^2

Cross section measurements of the exclusive p(e,e'K+)Lambda,Sigma^0 electroproduction reactions have been performed at the Mainz Microtron MAMI in the A1 spectrometer facility using for the first time the Kaos spectrometer for kaon detection. These processes were studied in a kinematical region not covered by any previous experiment. The nucleon was probed in its third resonance region with virtual photons of low four-momenta, Q^2= 0.030-0.055 (GeV/c)^2. The MAMI data indicate a smooth transition in Q^2 from photoproduction to electroproduction cross sections. Comparison with predictions of effective Lagrangian models based on the isobar approach reveal that strong longitudinal couplings of the virtual photon to the N* resonances can be excluded from these models.Comment: 16 pages, 7 figure