Results are presented on R&D efforts to design and build large size veto panels, optimized for underground low background experiments, in the most efficient and economical way using commercially ...available components. A variety of plastic scintillators, photomultiplier tubes, wavelength shifting fibers, and light reflector combinations were tested. Results of these studies and performance of a 2.2m long panel are presented.
A new model of interconnected coevolving SIRS epidemic and public vaccination opinion pattern is presented. The underlying two-layer network contains strata corresponding to physical interactions in ...real space and social communications. The layer corresponding to physical interactions is constructed based on data on a real network representing communications between high school students. The evolution of people vaccination attitude is described using an Ising-type model. The model describes a non-trivial dependence of resulting epidemic dynamics on (1) noise amplitude, (2) initial opinion pattern and (3) influence of external information.
An approach combining atomistic molecular dynamics (MD) and thermodynamic simulations has been applied to predict the distribution of components in binary Ni–Cu and Au–Ag nanoparticles consisting of ...2000 atoms (of about 4 nm in size). The term ‘thermodynamic simulation’ has referred to solving, in some approximations, the Butler equation for a core–shell particle model. Both atomistic and thermodynamic approaches predict the surface segregation of Cu atoms in Ni–Cu nanoparticles and segregation of Ag to the surface of Au–Ag nanoalloys. Then, contrary to the Ni–Cu systems, some Au–Ag nanoparticles demonstrated an onion-like structure with the outer Ag monolayer. The results of MD and thermodynamic simulations agree with each other and with some available direct and indirect experimental data.
Employing the isothermal molecular dynamics and the embedded atom method, we simulated melting of metallic nanoparticles (Au, Ag, Cu, Ni, and Pb ones). In more detail, the results for Au and Ag ...nanoparticles are presented and discussed. At first, we analyzed the behavior of the temperature dependences for the potential (cohesive) term into the specific (per atom) internal energy and for the degree of crystallinity in the course of heating nanoparticles. We have found that the results obtained for nanoparticles of about 4 and 8 nm in size (containing 2093 and 20,113 atoms, respectively) demonstrate the continuous melting. Employing the dependence of the specific potential energy on the distance to the nanoparticle center of mass and the common neighbor analysis, we showed that the continuous melting occurs via the surface pre-melting mechanism. Then, we evaluated the self-diffusion coefficient in the surface disordered layers of Au and Ag nanoparticles and found that our results agree in order of magnitude (10
−9
m
2
/s) with the values of the self-diffusion coefficient for the bulk Au and Ag melts at the corresponding bulk melting temperatures. Finally, combining in our molecular dynamics experiments continuous heating Au nanoparticles with annealing them at some constant selected temperatures, we have shown that the liquid nucleation and growth mechanism should be most adequate to the melting behavior of metallic nanoparticles.
Human ring chromosomes are often unstable during mitosis, and daughter cells can be partially or completely aneuploid. We studied the mitotic stability of four ring chromosomes, 8, 13, 18, and 22, in ...long-term cultures of skin fibroblasts and induced pluripotent stem cells (iPSCs) by GTG karyotyping and aCGH. Ring chromosome loss and secondary aberrations were observed in all fibroblast cultures except for r(18). We found monosomy, fragmentation, and translocation of indexed chromosomes. In iPSCs, aCGH revealed striking differences in mitotic stability both between iPSC lines with different rings and, in some cases, between cell lines with the same ring chromosome. We registered the spontaneous rescue of karyotype 46,XY,r(8) to 46,XY in all six iPSC lines through ring chromosome loss and intact homologue duplication with isoUPD(8)pat occurrence, as proven by SNP genotype distribution analysis. In iPSCs with other ring chromosomes, karyotype correction was not observed. Our results suggest that spontaneous correction of the karyotype with ring chromosomes in iPSCs is not universal and that pluripotency is compatible with a wide range of derivative karyotypes. We conclude that marked variability in the frequency of secondary rearrangements exists in both fibroblast and iPSC cultures, expanding the clinical significance of the constitutional ring chromosome.
The possibility of forming nanoporous copper-silicide films with different phase compositions is experimentally demonstrated. For this purpose, the parameters of the initial
a
-Si/Cu structure and ...the conditions of its annealing are chosen so that the process of solid-phase synthesis comes to a halt at the stage of formation of a branched silicide cluster. Then the films are subjected to liquid etching in a mixture of diluted inorganic acids. In this case, the metastable Cu
x
Si phase with a low Cu content is selectively removed, and a three-dimensional silicide cluster is released. At the same time, surface Kirkendall voids present in the films open. As a result of these two processes in combination, a nanoporous structure is formed.
The reactions of CuX2 (X = Cl, Br) with dipinodiazafluorenes yielded four new complexes CuX2L12 (X = Cl (1), Br (2), L1 = ...(1R,3R,8R,10R)-2,2,9,9-Tetramethyl-3,4,7,8,9,10-hexahydro-1H-1,3:8,10-dimethanocyclopenta 1,2-b:5,4-b’diquinolin-12(2H)-one) and (CuX2)2L2n (X = Cl (3), Br (4), L2 = (1R,3R,8R,10R,1’R,3’R,8’R,10’R)-2,2,2’,2’,9,9,9’,9’-Octamethyl-1,1’,2,2’,3,3’,4,4’,7,7’,8,8’,9,9’,10,10’-hexadecahydro-1,3:1’,3’:8,10:8’,10’-tetramethano-12,12’-bi(cyclopenta 1,2-b:5,4-b’diquinolinylidene). The complexes were characterized by IR and EPR spectroscopy, HR-ESI-MS and elemental analysis. The crystal structures of compounds 1, 2 and 4 were determined by X-ray diffraction (XRD) analysis. Complexes 1–2 have a monomeric structure, while complex 4 has a polymeric structure due to additional coordinating N,N sites in L2. All complexes contain a binuclear fragment {Cu2(μ-X)2×2} (X = Cl, Br) in their structures. Each copper atom has a distorted square-pyramidal coordination environment formed by two nitrogen atoms and three halogen atoms. The Cu-Nax distance is elongated compared to Cu-Neq. The EPR spectra of compounds 1–4 in CH3CN confirm their paramagnetic nature due to the d9 electronic configuration of the copper(II) ion. The magnetic properties of all compounds were studied by the method of static magnetic susceptibility. For complexes 1 and 2, the effective magnetic moments are µeff ≈ 1.87 and 1.83 µB (per each Cu2+ ion), respectively, in the temperature range 50–300 K, which are close to the theoretical spin value (1.73 µB). Ferromagnetic exchange interactions between Cu(II) ions inside {Cu2(μ-X)2X2} (X = Cl, Br) dimers (J/kB ≈ 25 and 31 K for 1 and 2, respectively) or between dimers (θ′ ≈ 0.30 and 0.47 K for 1 and 2, respectively) were found at low temperatures. For compounds 3 and 4, the magnetic susceptibility is well described by the Curie–Weiss law in the temperature range 1.77–300 K with µeff ≈ 1.72 and 1.70 µB for 3 and 4, respectively, and weak antiferromagnetic interactions (θ ≈ −0.4 K for 3 and −0.65 K for 4). Complexes 1–4 exhibit high catalytic activity in the oxidation of alkanes and alcohols with peroxides. The maximum yield of cyclohexane oxidation products reached 50% (complex 3). Based on the data on the study of regio- and bond-selectivity, it was concluded that hydroxyl radicals play a decisive role in the oxidation reaction. The initial products in reactions with alkanes are alkyl hydroperoxides.
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