Statistical methods applied to the search of sterile neutrinos

The frequentist statistical methods applied to search for short-baseline neutrino oscillations induced by a sterile neutrino with mass at the eV scale are reviewed and compared. The comparison is performed under limit setting and signal discovery scenarios, considering both when an oscillation would enhance the neutrino interaction rate in the detector and when it would reduce it. The sensitivity of the experiments and the confidence regions extracted for specific data sets change considerably according to which test statistic is used and the assumptions on its probability distribution. A standardized analysis approach based on the most general kind of hypothesis test is proposed

Attosecond pulse shaping around a Cooper minimum

High harmonic generation (HHG) is used to measure the spectral phase of the recombination dipole matrix element (RDM) in argon over a broad frequency range that includes the 3p Cooper minimum (CM). The measured RDM phase agrees well with predictions based on the scattering phases and amplitudes of the interfering s- and d-channel contributions to the complementary photoionization process. The reconstructed attosecond bursts that underlie the HHG process show that the derivative of the RDM spectral phase, the group delay, does not have a straight-forward interpretation as an emission time, in contrast to the usual attochirp group delay. Instead, the rapid RDM phase variation caused by the CM reshapes the attosecond bursts.Comment: 5 pages, 5 figure

Inelastic scattering of broadband electron wave packets driven by an intense mid-infrared laser field

Intense, 100 fs laser pulses at 3.2 and 3.6 um are used to generate, by multi-photon ionization, broadband wave packets with up to 400 eV of kinetic energy and charge states up to Xe+6. The multiple ionization pathways are well described by a white electron wave packet and field-free inelastic cross sections, averaged over the intensity-dependent energy distribution for (e,ne) electron impact ionization. The analysis also suggests a contribution from a 4d core excitation in xenon

Mitigation of 42^{42}Ar/42^{42}K background for the GERDA Phase II experiment

Background coming from the $^{42}$Ar decay chain is considered to be one of the most relevant for the GERDA experiment, which aims to search of the neutrinoless double beta decay of $^{76}$Ge. The sensitivity strongly relies on the absence of background around the Q-value of the decay. Background coming from $^{42}$K, a progeny of $^{42}$Ar, can contribute to that background via electrons from the continuous spectrum with an endpoint of 3.5 MeV. Research and development on the suppression methods targeting this source of background were performed at the low-background test facility LArGe. It was demonstrated that by reducing $^{42}$K ion collection on the surfaces of the broad energy germanium detectors in combination with pulse shape discrimination techniques and an argon scintillation veto, it is possible to suppress the $^{42}$K background by three orders of magnitude. This is sufficient for Phase II of the GERDA experiment

Prospects of Heterogeneous Hydroformylation with Supported Single Atom Catalysts

[EN] The potential of oxide-supported rhodium single atom catalysts (SACs) for heterogeneous hydroformylation was investigated both theoretically and experimentally. Using high-level domain-based local-pair natural orbital coupled cluster singles doubles with perturbative triples contribution (DLPNO-CCSD(T)) calculations, both stability and catalytic activity were investigated for Rh single atoms on different oxide surfaces. Atomically dispersed, supported Rh catalysts were synthesized on MgO and CeO2. While the CeO2-supported rhodium catalyst is found to be highly active, this is not the case for MgO, most likely due to increased confinement, as determined by extended X-ray absorption fine structure spectroscopy (EXAFS), that diminishes the reactivity of Rh complexes on MgO. This agrees well with our computational investigation, where we find that rhodium carbonyl hydride complexes on flat oxide surfaces such as CeO2(111) have catalytic activities comparable to those of molecular complexes. For a step edge on a MgO(301) surface, however, calculations show a significantly reduced catalytic activity. At the same time, calculations predict that stronger adsorption at the higher coordinated adsorption site leads to a more stable catalyst. Keeping the balance between stability and activity appears to be the main challenge for oxide supported Rh hydroformylation catalysts. In addition to the chemical bonding between rhodium complex and support, the confinement experienced by the active site plays an important role for the catalytic activity.X-ray absorption experiments were performed at the ALBA Synchrotron Light Source (Spain), experiment 2019023278. Beamline scientists L. Simonelli and C. Marini are gratefully acknowledged for their contribution to beam setup. E. Andrés, E. Martínez-Monje, I. López, and M. García-Farpón (ITQ) are acknowledged for their assistance with XAS data acquisition. J. Ternedien (MPI-KOFO) is acknowledged for the performance of XRD experiments. N. Pfänder (MPI-CEC) is acknowledged for his contribution to STEM characterization. The authors acknowledge support by the state of Baden-Württemberg through bwHPC (bwUnicluster and JUSTUS, RV bw17D01). The authors gratefully acknowledge support by the GRK 2450. Financial support from the Helmholtz Association is also gratefully acknowledged. The experimental work received funding from the Max Planck Society and the Spanish Ministry of Science, Innovation and Universities (projects SEV-2016-0683 and RTI2018-096399-A-I00). B.B.S. acknowledges the Alexander von Humboldt Foundation for a postdoctoral scholarship.Amsler, J.; Sarma, BB.; Agostini, G.; Prieto González, G.; Plessow, P.; Studt, F. (2020). Prospects of Heterogeneous Hydroformylation with Supported Single Atom Catalysts. Journal of the American Chemical Society. 142(11):5087-5096. https://doi.org/10.1021/jacs.9b12171S5087509614211Franke, R., Selent, D., & Börner, A. (2012). Applied Hydroformylation. Chemical Reviews, 112(11), 5675-5732. doi:10.1021/cr3001803Serna, P., Yardimci, D., Kistler, J. D., & Gates, B. C. (2014). Formation of supported rhodium clusters from mononuclear rhodium complexes controlled by the support and ligands on rhodium. Phys. Chem. Chem. Phys., 16(3), 1262-1270. doi:10.1039/c3cp53057dGuan, E., & Gates, B. C. (2017). Stable Rhodium Pair Sites on MgO: Influence of Ligands and Rhodium Nuclearity on Catalysis of Ethylene Hydrogenation and H–D Exchange in the Reaction of H2 with D2. ACS Catalysis, 8(1), 482-487. doi:10.1021/acscatal.7b03549Dossi, C., Fusi, A., Garlaschelli, L., Roberto, D., Ugo, R., & Psaro, R. (1991). Ethylene hydroformylation with the silica-supported K2[Rh12(CO)30] cluster: evidence for vapor-phase cluster catalysis. Catalysis Letters, 11(3-6), 335-339. doi:10.1007/bf00764325Ehresmann, J. O., Kletnieks, P. W., Liang, A., Bhirud, V. A., Bagatchenko, O. P., Lee, E. J., … Haw, J. F. (2006). Evidence from NMR and EXAFS Studies of a Dynamically Uniform Mononuclear Single-Site Zeolite-Supported Rhodium Catalyst. Angewandte Chemie International Edition, 45(4), 574-576. doi:10.1002/anie.200502864Sun, Q., Dai, Z., Liu, X., Sheng, N., Deng, F., Meng, X., & Xiao, F.-S. (2015). Highly Efficient Heterogeneous Hydroformylation over Rh-Metalated Porous Organic Polymers: Synergistic Effect of High Ligand Concentration and Flexible Framework. Journal of the American Chemical Society, 137(15), 5204-5209. doi:10.1021/jacs.5b02122De Munck, N. A., Verbruggen, M. W., & Scholten, J. J. F. (1981). Gas phase hydroformylation of propylene with porous resin anchored rhodium complexes part I. Methods of catalyst preparation and characterization. Journal of Molecular Catalysis, 10(3), 313-330. doi:10.1016/0304-5102(81)85052-3Lang, R., Li, T., Matsumura, D., Miao, S., Ren, Y., Cui, Y.-T., … Zhang, T. (2016). Hydroformylation of Olefins by a Rhodium Single-Atom Catalyst with Activity Comparable to RhCl(PPh3)3. Angewandte Chemie International Edition, 55(52), 16054-16058. doi:10.1002/anie.201607885Yang, X.-F., Wang, A., Qiao, B., Li, J., Liu, J., & Zhang, T. (2013). Single-Atom Catalysts: A New Frontier in Heterogeneous Catalysis. Accounts of Chemical Research, 46(8), 1740-1748. doi:10.1021/ar300361mPaolucci, C., Khurana, I., Parekh, A. A., Li, S., Shih, A. J., Li, H., … Gounder, R. (2017). Dynamic multinuclear sites formed by mobilized copper ions in NO x selective catalytic reduction. Science, 357(6354), 898-903. doi:10.1126/science.aan5630Jangjou, Y., Do, Q., Gu, Y., Lim, L.-G., Sun, H., Wang, D., … Epling, W. S. (2018). Nature of Cu Active Centers in Cu-SSZ-13 and Their Responses to SO2 Exposure. ACS Catalysis, 8(2), 1325-1337. doi:10.1021/acscatal.7b03095Wang, L., Zhang, W., Wang, S., Gao, Z., Luo, Z., Wang, X., … Zeng, J. (2016). Atomic-level insights in optimizing reaction paths for hydroformylation reaction over Rh/CoO single-atom catalyst. Nature Communications, 7(1). doi:10.1038/ncomms14036Li, T., Chen, F., Lang, R., Wang, H., Su, Y., Qiao, B., … Zhang, T. (2020). Styrene Hydroformylation with In Situ Hydrogen: Regioselectivity Control by Coupling with the Low‐Temperature Water–Gas Shift Reaction. Angewandte Chemie International Edition, 59(19), 7430-7434. doi:10.1002/anie.202000998Heck, R. F., & Breslow, D. S. (1961). The Reaction of Cobalt Hydrotetracarbonyl with Olefins. Journal of the American Chemical Society, 83(19), 4023-4027. doi:10.1021/ja01480a017Van Leeuwen, P. W. N. M., & Claver, C. (Eds.). (2002). Rhodium Catalyzed Hydroformylation. Catalysis by Metal Complexes. doi:10.1007/0-306-46947-2Van Rooy, A. (1996). Rhodium-catalysed hydroformylation of branched 1-alkenes; bulky phosphite vs. triphenylphosphine as modifying ligand. Journal of Organometallic Chemistry, 507(1-2), 69-73. doi:10.1016/0022-328x(95)05748-eSparta, M., Børve, K. J., & Jensen, V. R. (2007). Activity of Rhodium-Catalyzed Hydroformylation:  Added Insight and Predictions from Theory. Journal of the American Chemical Society, 129(27), 8487-8499. doi:10.1021/ja070395nGellrich, U., Himmel, D., Meuwly, M., & Breit, B. (2013). Realistic Energy Surfaces for Real-World Systems: An IMOMO CCSD(T):DFT Scheme for Rhodium-Catalyzed Hydroformylation with the 6-DPPon Ligand. Chemistry - A European Journal, 19(48), 16272-16281. doi:10.1002/chem.201302132Kumar, M., Chaudhari, R. V., Subramaniam, B., & Jackson, T. A. (2014). Ligand Effects on the Regioselectivity of Rhodium-Catalyzed Hydroformylation: Density Functional Calculations Illuminate the Role of Long-Range Noncovalent Interactions. Organometallics, 33(16), 4183-4191. doi:10.1021/om500196gJiao, Y., Torne, M. S., Gracia, J., Niemantsverdriet, J. W. (Hans), & van Leeuwen, P. W. N. M. (2017). Ligand effects in rhodium-catalyzed hydroformylation with bisphosphines: steric or electronic? Catalysis Science & Technology, 7(6), 1404-1414. doi:10.1039/c6cy01990kSchmidt, S., Deglmann, P., & Hofmann, P. (2014). Density Functional Investigations of the Rh-Catalyzed Hydroformylation of 1,3-Butadiene with Bisphosphite Ligands. ACS Catalysis, 4(10), 3593-3604. doi:10.1021/cs500718vJacobs, I., de Bruin, B., & Reek, J. N. H. (2015). Comparison of the Full Catalytic Cycle of Hydroformylation Mediated by Mono- and Bis-Ligated Triphenylphosphine-Rhodium Complexes by Using DFT Calculations. ChemCatChem, 7(11), 1708-1718. doi:10.1002/cctc.201500087Kégl, T. (2015). Computational aspects of hydroformylation. RSC Advances, 5(6), 4304-4327. doi:10.1039/c4ra13121eWodrich, M. D., Busch, M., & Corminboeuf, C. (2016). Accessing and predicting the kinetic profiles of homogeneous catalysts from volcano plots. Chemical Science, 7(9), 5723-5735. doi:10.1039/c6sc01660jLiu, J., Bunes, B. R., Zang, L., & Wang, C. (2017). Supported single-atom catalysts: synthesis, characterization, properties, and applications. Environmental Chemistry Letters, 16(2), 477-505. doi:10.1007/s10311-017-0679-2Kwon, Y., Kim, T. Y., Kwon, G., Yi, J., & Lee, H. (2017). Selective Activation of Methane on Single-Atom Catalyst of Rhodium Dispersed on Zirconia for Direct Conversion. Journal of the American Chemical Society, 139(48), 17694-17699. doi:10.1021/jacs.7b11010Sarma, B. B., Kim, J., Amsler, J., Agostini, G., Weidenthaler, C., Pfänder, N., … Prieto, G. (2020). One‐Pot Cooperation of Single‐Atom Rh and Ru Solid Catalysts for a Selective Tandem Olefin Isomerization‐Hydrosilylation Process. Angewandte Chemie International Edition, 59(14), 5806-5815. doi:10.1002/anie.201915255Qiao, B., Wang, A., Yang, X., Allard, L. F., Jiang, Z., Cui, Y., … Zhang, T. (2011). Single-atom catalysis of CO oxidation using Pt1/FeOx. Nature Chemistry, 3(8), 634-641. doi:10.1038/nchem.1095Sun, S., Zhang, G., Gauquelin, N., Chen, N., Zhou, J., Yang, S., … Sun, X. (2013). Single-atom Catalysis Using Pt/Graphene Achieved through Atomic Layer Deposition. Scientific Reports, 3(1). doi:10.1038/srep01775Abbet, S., Sanchez, A., Heiz, U., Schneider, W.-D., Ferrari, A. M., Pacchioni, G., & Rösch, N. (2000). Acetylene Cyclotrimerization on Supported Size-Selected Pdn Clusters (1 ≤ n ≤ 30): One Atom Is Enough! Journal of the American Chemical Society, 122(14), 3453-3457. doi:10.1021/ja9922476Lin, J., Wang, A., Qiao, B., Liu, X., Yang, X., Wang, X., … Zhang, T. (2013). Remarkable Performance of Ir1/FeOx Single-Atom Catalyst in Water Gas Shift Reaction. Journal of the American Chemical Society, 135(41), 15314-15317. doi:10.1021/ja408574mGu, X.-K., Qiao, B., Huang, C.-Q., Ding, W.-C., Sun, K., Zhan, E., … Li, W.-X. (2014). Supported Single Pt1/Au1 Atoms for Methanol Steam Reforming. ACS Catalysis, 4(11), 3886-3890. doi:10.1021/cs500740uJones, J., Xiong, H., DeLaRiva, A. T., Peterson, E. J., Pham, H., Challa, S. R., … Datye, A. K. (2016). Thermally stable single-atom platinum-on-ceria catalysts via atom trapping. Science, 353(6295), 150-154. doi:10.1126/science.aaf8800Fei, H., Dong, J., Arellano-Jiménez, M. J., Ye, G., Dong Kim, N., Samuel, E. L. G., … Tour, J. M. (2015). Atomic cobalt on nitrogen-doped graphene for hydrogen generation. Nature Communications, 6(1). doi:10.1038/ncomms9668Wei, H., Liu, X., Wang, A., Zhang, L., Qiao, B., Yang, X., … Zhang, T. (2014). FeOx-supported platinum single-atom and pseudo-single-atom catalysts for chemoselective hydrogenation of functionalized nitroarenes. Nature Communications, 5(1). doi:10.1038/ncomms6634Wang, X., van Bokhoven, J. A., & Palagin, D. (2020). Atomically dispersed platinum on low index and stepped ceria surfaces: phase diagrams and stability analysis. Physical Chemistry Chemical Physics, 22(1), 28-38. doi:10.1039/c9cp04973hNeitzel, A., Figueroba, A., Lykhach, Y., Skála, T., Vorokhta, M., Tsud, N., … Libuda, J. (2016). Atomically Dispersed Pd, Ni, and Pt Species in Ceria-Based Catalysts: Principal Differences in Stability and Reactivity. The Journal of Physical Chemistry C, 120(18), 9852-9862. doi:10.1021/acs.jpcc.6b02264Tang, Y., Asokan, C., Xu, M., Graham, G. W., Pan, X., Christopher, P., … Sautet, P. (2019). Rh single atoms on TiO2 dynamically respond to reaction conditions by adapting their site. Nature Communications, 10(1). doi:10.1038/s41467-019-12461-6DeRita, L., Resasco, J., Dai, S., Boubnov, A., Thang, H. V., Hoffman, A. S., … Christopher, P. (2019). Structural evolution of atomically dispersed Pt catalysts dictates reactivity. Nature Materials, 18(7), 746-751. doi:10.1038/s41563-019-0349-9Su, Y.-Q., Wang, Y., Liu, J.-X., Filot, I. A. W., Alexopoulos, K., Zhang, L., … Hensen, E. J. M. (2019). Theoretical Approach To Predict the Stability of Supported Single-Atom Catalysts. ACS Catalysis, 9(4), 3289-3297. doi:10.1021/acscatal.9b00252O’Connor, N. J., Jonayat, A. S. M., Janik, M. J., & Senftle, T. P. (2018). Interaction trends between single metal atoms and oxide supports identified with density functional theory and statistical learning. Nature Catalysis, 1(7), 531-539. doi:10.1038/s41929-018-0094-5Perdew, J. P., Burke, K., & Ernzerhof, M. (1996). Generalized Gradient Approximation Made Simple. Physical Review Letters, 77(18), 3865-3868. doi:10.1103/physrevlett.77.3865Grimme, S., Antony, J., Ehrlich, S., & Krieg, H. (2010). A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. The Journal of Chemical Physics, 132(15), 154104. doi:10.1063/1.3382344Kresse, G., & Joubert, D. (1999). From ultrasoft pseudopotentials to the projector augmented-wave method. Physical Review B, 59(3), 1758-1775. doi:10.1103/physrevb.59.1758Kresse, G., & Furthmüller, J. (1996). Efficient iterative schemes forab initiototal-energy calculations using a plane-wave basis set. Physical Review B, 54(16), 11169-11186. doi:10.1103/physrevb.54.11169Blöchl, P. E. (1994). Projector augmented-wave method. Physical Review B, 50(24), 17953-17979. doi:10.1103/physrevb.50.17953Anisimov, V. I., Zaanen, J., & Andersen, O. K. (1991). Band theory and Mott insulators: HubbardUinstead of StonerI. Physical Review B, 44(3), 943-954. doi:10.1103/physrevb.44.943Dudarev, S. L., Botton, G. A., Savrasov, S. Y., Humphreys, C. J., & Sutton, A. P. (1998). Electron-energy-loss spectra and the structural stability of nickel oxide:  An LSDA+U study. Physical Review B, 57(3), 1505-1509. doi:10.1103/physrevb.57.1505Song, Y.-L., Yin, L.-L., Zhang, J., Hu, P., Gong, X.-Q., & Lu, G. (2013). A DFT+U study of CO oxidation at CeO2(110) and (111) surfaces with oxygen vacancies. Surface Science, 618, 140-147. doi:10.1016/j.susc.2013.09.001Nolan, M., Grigoleit, S., Sayle, D. C., Parker, S. C., & Watson, G. W. (2005). Density functional theory studies of the structure and electronic structure of pure and defective low index surfaces of ceria. Surface Science, 576(1-3), 217-229. doi:10.1016/j.susc.2004.12.016Huang, M., & Fabris, S. (2008). CO Adsorption and Oxidation on Ceria Surfaces from DFT+U Calculations. The Journal of Physical Chemistry C, 112(23), 8643-8648. doi:10.1021/jp709898rMonkhorst, H. J., & Pack, J. D. (1976). Special points for Brillouin-zone integrations. Physical Review B, 13(12), 5188-5192. doi:10.1103/physrevb.13.5188Plessow, P. N. (2018). Efficient Transition State Optimization of Periodic Structures through Automated Relaxed Potential Energy Surface Scans. Journal of Chemical Theory and Computation, 14(2), 981-990. doi:10.1021/acs.jctc.7b01070Zhao, Y., & Truhlar, D. G. (2007). The M06 suite of density functionals for main group thermochemistry, thermochemical kinetics, noncovalent interactions, excited states, and transition elements: two new functionals and systematic testing of four M06-class functionals and 12 other functionals. Theoretical Chemistry Accounts, 120(1-3), 215-241. doi:10.1007/s00214-007-0310-xStephens, P. J., Devlin, F. J., Chabalowski, C. F., & Frisch, M. J. (1994). Ab Initio Calculation of Vibrational Absorption and Circular Dichroism Spectra Using Density Functional Force Fields. The Journal of Physical Chemistry, 98(45), 11623-11627. doi:10.1021/j100096a001TURBOMOLE, V.7.1 2016, a development of Karlsruhe Institute of Technology, Karlsruhe, 1989–2019, TURBOMOLE GmbH, since 2007; available from http://www.turbomole.com. Turbomole GmbH: 2016.Weigend, F. (2006). Accurate Coulomb-fitting basis sets for H to Rn. Physical Chemistry Chemical Physics, 8(9), 1057. doi:10.1039/b515623hWeigend, F., & Ahlrichs, R. (2005). Balanced basis sets of split valence, triple zeta valence and quadruple zeta valence quality for H to Rn: Design and assessment of accuracy. Physical Chemistry Chemical Physics, 7(18), 3297. doi:10.1039/b508541aNeese, F. (2011). The ORCA program system. WIREs Computational Molecular Science, 2(1), 73-78. doi:10.1002/wcms.81Neese, F. (2017). Software update: the ORCA program system, version 4.0. WIREs Computational Molecular Science, 8(1). doi:10.1002/wcms.1327Ekström, U., Visscher, L., Bast, R., Thorvaldsen, A. J., & Ruud, K. (2010). Arbitrary-Order Density Functional Response Theory from Automatic Differentiation. Journal of Chemical Theory and Computation, 6(7), 1971-1980. doi:10.1021/ct100117sAndrae, D., H�u�ermann, U., Dolg, M., Stoll, H., & Preu�, H. (1990). Energy-adjustedab initio pseudopotentials for the second and third row transition elements. Theoretica Chimica Acta, 77(2), 123-141. doi:10.1007/bf01114537Marenich, A. V., Cramer, C. J., & Truhlar, D. G. (2009). Universal Solvation Model Based on Solute Electron Density and on a Continuum Model of the Solvent Defined by the Bulk Dielectric Constant and Atomic Surface Tensions. The Journal of Physical Chemistry B, 113(18), 6378-6396. doi:10.1021/jp810292nRiplinger, C., Pinski, P., Becker, U., Valeev, E. F., & Neese, F. (2016). Sparse maps—A systematic infrastructure for reduced-scaling electronic structure methods. II. Linear scaling domain based pair natural orbital coupled cluster theory. The Journal of Chemical Physics, 144(2), 024109. doi:10.1063/1.4939030Ugliengo, P., & Damin, A. (2002). Are dispersive forces relevant for CO adsorption on the MgO(001) surface? Chemical Physics Letters, 366(5-6), 683-690. doi:10.1016/s0009-2614(02)01657-3Alessio, M., Usvyat, D., & Sauer, J. (2018). Chemically Accurate Adsorption Energies: CO and H2O on the MgO(001) Surface. Journal of Chemical Theory and Computation, 15(2), 1329-1344. doi:10.1021/acs.jctc.8b01122Utamapanya, S., Klabunde, K. J., & Schlup, J. R. (1991). Nanoscale metal oxide particles/clusters as chemical reagents. Synthesis and properties of ultrahigh surface area magnesium hydroxide and magnesium oxide. Chemistry of Materials, 3(1), 175-181. doi:10.1021/cm00013a036Ravel, B., & Newville, M. (2005). ATHENA,ARTEMIS,HEPHAESTUS: data analysis for X-ray absorption spectroscopy usingIFEFFIT. Journal of Synchrotron Radiation, 12(4), 537-541. doi:10.1107/s0909049505012719Connett, J. E. (1972). Chemical equilibria 5. Measurement of equilibrium constants for the dehydrogenation of propanol by a vapour flow technique. The Journal of Chemical Thermodynamics, 4(2), 233-237. doi:10.1016/0021-9614(72)90061-4Wodrich, M. D., Busch, M., & Corminboeuf, C. (2018). Expedited Screening of Active and Regioselective Catalysts for the Hydroformylation Reaction. Helvetica Chimica Acta, 101(9), e1800107. doi:10.1002/hlca.201800107Goula, G., Botzolaki, G., Osatiashtiani, A., Parlett, C. M. A., Kyriakou, G., Lambert, R. M., & Yentekakis, I. V. (2019). Oxidative Thermal Sintering and Redispersion of Rh Nanoparticles on Supports with High Oxygen Ion Lability. Catalysts, 9(6), 541. doi:10.3390/catal9060541Lazzaroni, R., Raffaelli, A., Settambolo, R., Bertozzi, S., & Vitulli, G. (1989). Regioselectivity in the rhodium-catalyzed hydroformylation of styrene as a function of reaction temperature and gas pressure. Journal of Molecular Catalysis, 50(1), 1-9. doi:10.1016/0304-5102(89)80104-xYu, S., Chie, Y., Guan, Z., Zou, Y., Li, W., & Zhang, X. (2008). Highly Regioselective Hydroformylation of Styrene and Its Derivatives Catalyzed by Rh Complex with Tetraphosphorus Ligands. Organic Letters, 11(1), 241-244. doi:10.1021/ol802479

Double Ionization by Strong Elliptically Polarized Laser Pulses

We join the tribute to Professor N.B. Delone in this memorial issue by presenting the results of new calculations on the effects of ellipticity on double ionization by short and strong near-optical laser pulses.Comment: 3 pages, 4 figures, accepted in Professor N.B. Delone's memorial issu

Bottom-up assembly of bimetallic nanocluster catalysts from oxide-supported single-atom precursors

The precise synthesis and stabilization of oxide-supported bimetallic clusters in the low-to-sub nanometer size regime is highly relevant in various fields, from optics and sensing to electrochemistry and catalysis. In surface-driven phenomena such as catalysis, avoiding metal segregation and agglomeration is essential for performance and stability under relevant operation conditions. Here we show how high-temperature oxidative crystal redispersion and oxide atom-trapping phenomena provide a widely valid route towards atomically dispersed bimetallic precursors which, upon reductive metal agglomeration, result in very small, uniformly sized and remarkably stable bimetallic clusters. For a PdPt/MgO system, oxidative redispersion leads to isolated Pd and Pt atoms stabilized by the MgO support up to overall surface metal contents of ca. 1.0 M$_{at}$ nm$_{-2}$, beyond which loading, atom-trapping oxide sites become exhausted and metal aggregation sets in. On the contrary, more conventional, milder-temperature activation protocols lead to significant metal segregation and markedly bimodal particle size populations already from comparatively lower metal contents. As proven by in situ X-ray absorption spectroscopy and atomic-resolution STEM microscopy, the stabilization of isolated Pd and Pt cations within nanometer distances on the common MgO support is essential for the synthesis of ca. 1 nm bimetallic PdPt clusters by reductive agglomeration. The uniformly sized PdPt aggregates developed on MgO from single-atom precursors display a notably higher activity for the oxidative activation of methane with carbon dioxide (dry reforming) at 923 K compared to analogue materials synthesized via milder calcination/reduction protocols. Moreover, despite their high surface-to-volume ratio, the small bimetallic clusters in the former display an outstanding stability against metal agglomeration under the demanding reaction conditions, likely as a result of a lower driving force for Ostwald ripening growth processes. The synthesis concept, which is amenable to other combinations of 4d and 5d transition metals, contributes to the rationalization of the possibilities and bounds of oxidative metal redispersion phenomena and provides a technically simple and potentially general route to high-temperature stable, (sub)nanometer bimetallic clusters for catalysis and other applications where bimetallic effects and thermal stability are of importance

Two-color ionization of hydrogen by short intense pulses

Photoelectron energy spectra resulting by the interaction of hydrogen with two short pulses having carrier frequencies, respectively, in the range of the infrared and XUV regions have been calculated. The effects of the pulse duration and timing of the X-ray pulse on the photoelectron energy spectra are discussed. Analysis of the spectra obtained for very long pulses show that certain features may be explained in terms of quantum interferences in the time domain. It is found that, depending on the duration of the X-ray pulse, ripples in the energy spectra separated by the infrared photon energy may appear. Moreover, the temporal shape of the low frequency radiation field may be inferred by the breadth of the photoelectron energy spectra.Comment: 12 pages, 8 figure

Intrinsic and Extrinsic Modulators of the Epithelial to Mesenchymal Transition: Driving the Fate of Tumor Microenvironment

The epithelial to mesenchymal transition (EMT) is an evolutionarily conserved process. In cancer, EMT can activate biochemical changes in tumor cells that enable the destruction of the cellular polarity, leading to the acquisition of invasive capabilities. EMT regulation can be triggered by intrinsic and extrinsic signaling, allowing the tumor to adapt to the microenvironment demand in the different stages of tumor progression. In concomitance, tumor cells undergoing EMT actively interact with the surrounding tumor microenvironment (TME) constituted by cell components and extracellular matrix as well as cell secretome elements. As a result, the TME is in turn modulated by the EMT process toward an aggressive behavior. The current review presents the intrinsic and extrinsic modulators of EMT and their relationship with the TME, focusing on the non-cell-derived components, such as secreted metabolites, extracellular matrix, as well as extracellular vesicles. Moreover, we explore how these modulators can be suitable targets for anticancer therapy and personalized medicine