Transverse-and zero-field μSR investigation of magnetism and superconductivity in (Y1−xPr x )Ba2Cu3O7

Zero-field muon-spin-rotation (μSR) measurements on (Y₁? _x Pr _x )Ba₂Cu₃O₇ [x=1.0, 0.8, 0.6, and 0.54] show evidence for antiferromagnetic ordering of the Cu moments within the Cu?O planes, with Néel temperatures 285, 220, 35. 30 and 20 K, respectively. Forx=1.0 the local muon magnetic field is ≈16 mT, but decreases to ≈12 mT at 17K, due to additional magnetic ordering. The zero-field data, in conjunction with transport data, allow construction of a complete phase diagram for this system. Transverse-field (1 kOe) μSR data forx=0.2 (T _c =75 K) show that the muon depolarization is determined primarily by the Cu nuclear moments forT>T _c , and by the vortex state forT _c . Fitting the superconducting-state data to a BCS model yields an extrapolated zero-temperature magnetic penetration depth of 2170 Å.     

A comparison between ab initio calculated and measured Raman spectrum of triclinic albite (NaAlSi3O8)

Albite is one of the most common minerals in the Earth's crust, and its polymorphs can be found in rocks with different cooling histories. The characteristic spectrum of vibration of the albite mineral reflects its structural Si/Al ordering. In this study, we report on the comparison between the Raman spectra measured on a natural and fully ordered (as deduced on the basis of single‐crystal X‐ray diffraction data) ‘low albite’, NaAlSi₃O₈, and those calculated at the hybrid Hartree–Fock/density functional theory level by employing the WC1LYP Hamiltonian, which has proven to give excellent agreement between calculated and experimentally measured vibrational wavenumbers in silicate minerals. All the 39 expected A_g modes are identified in the Raman spectra, and their wavenumbers and intensities, in different scattering configurations, correspond well to the calculated ones. The average absolute discrepancy is ~3.4 cm⁻¹, being the maximum discrepancy |Δv|_max ~ 10.3 cm⁻¹. The very good quality of the WC1LYP results allows for reliable assignments of the Raman features to specific patterns of atomic vibrational motion. Copyright © 2015 John Wiley & Sons, Ltd.     

Reactions of stereochemically rigid diisocyanides with manganese carbonyl derivatives

The reactions of BrMn(CO)₅ with the non-chelating stereochemically rigid bidentate ligands (L-L) 1,3-, and 1,4-diisocyanobenzene, 4,4′-diisocyanobiphenyl, and 4,4′-diisocyanodiphenylmethane afford well characterized complexes of the types BrMn(CO)₄(L-L), BrMn(CO)₃(L-L)₂, and [BrMn(CO)₄]₂(L-L). Similar reactions with [RC₅H₄Mn(CO)₂NO]⁺PF₆⁻ gave mixtures of oligomers of the type [(RC₅H₄MnNO)_n(L-L)_n+1]ⁿ⁺[PF₆⁻]_n.     

Reversible and Irreversible Tracer Dispersion in an Oscillating Flow Inside a Model Rough Fracture

We study the mixing dynamics of a dyed and a clear miscible fluid by an oscillating flow inside an Hele-Shaw cell with randomly distributed circular obstacles. A transparent setup allows us to analyze the distribution of the two fluids and the reversible and irreversible mixing components. At the lower Péclet numbers Pe (based on the averaged absolute fluid velocity), geometrical dispersion due to the disordered flow field between the obstacles is dominant: the corresponding dispersivity is constant with Pe and, at constant Pe, increases with the amplitude of the oscillations and is negligible at small ones. Compared to echo dispersion with only one injection–suction cycle, oscillating flows are shown to provide additional information when the number of oscillations and, as a result, the distance of transverse mixing are varied. Geometrical dispersion is dominant up to a limiting Pe increasing with the amplitude. At higher \({\textit{Pe}}'{\textit{s}}\), the results are similar to those of Taylor dispersion in cells with smooth walls.     

The preparation of dicyano-1,3,4-thiadiazole and tricyanothiazole via 1,2,3-dithiazole chemistry

Treatment of 1,2-bis(4-chloro-5H-1,2,3-dithiazol-5-ylidene)hydrazine 4 with benzyltriethylammonium iodide (1 equiv) affords dicyano-1,3,4-thiadiazole 3 and 5-cyano-1,3,4-thiadiazole-2-carboxamide 5 in 79 and 21% yields, respectively. By using polymer bound triphenylphosphine instead of benzyltriethylammonium iodide the dicyano-1,3,4-thiadiazole 3 can be isolated in 70% yield without chromatography. The reaction of DAMN with Appel salt 8 gave 2-(4-chloro-5H-1,2,3-dithiazol-5-ylideneamino)-2-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)acetonitrile 7 (14%), 2,3-bis-(4-chloro-5H-1,2,3-dithiazol-5-ylideneamino)fumaronitrile 10 (14%), and 2,3-bis(4-chloro-5H-1,2,3-dithiazol-5-ylideneamino)maleonitrile 11 (24%) together with other products. The maleonitrile 11 isomerizes into the fumaronitrile 10 on irradiation at 365 nm. Reaction of aminoacetonitrile with Appel salt 8 gives the (dithiazolylidene)acetonitrile 7 in 33% yield. Treatment of (dithiazolylidene)acetonitrile 7 with polymer bound triphenylphosphine gives tricyanothiazole 6 in 76% yield. A rational general mechanism for the transformation of bisdithiazoles to percyanoheteroles is proposed.     

Interventions in GARCE Branching Processes with Application to Ebola Virus Data

In hindsight, even a cursory look may have revealed substantial growth of the 2014 Ebola infection and death cases in West Africa before drastic interventions showed an effect in late 2014. Yet a timely assessment as to whether an intervention has a sufficient impact to stabilize and eventually end an outbreak is equally important as early detection and accurate prediction of the magnitude of the outbreak several months before it spins out of control. To this aim, we consider an intervention effect in the GARCE branching process model, proposed by Hueter, that was successful to early detect the magnitude of the outbreak when data became available in early 2014. This model provides a novel and simple approach to branching processes that allows for time-varying random environments and instances of peak growth and near extinction-type rates as seen in Ebola viruses, tuberculosis infections, and infectious diseases. We present results on the survival and extinction behaviours, characterization of the phase transition between the subcritical and supercritical phases, and a sufficient condition for escape from supercriticality upon a level shift intervention. Intervention analysis of the Ebola outbreak data are presented and findings on the outbreak’s estimated phase and intervention effect are discussed.     

Unsteady simple shear flow in a viscoplastic fluid: comparison between analytical and numerical solutions

In this paper, an unsteady flow of a viscoplastic fluid for simple shear flow geometry is solved numerically using two regularizing functions to overcome the discontinuity for zero shear rate of the Bingham constitutive law. The adopted models are the well-known Papanastasiou relation and one based on the error function. The numerical results are compared with the analytical solution of the same problem obtained by Sekimoto (J Non-Newton Fluid Mech 39:107–113, 1991). The analysis of the results emphasizes that the errors are much smaller in the yielded than in the unyielded region. The models approximate closer the ideal Bingham model as the regularization parameters increase. The differences between the models tend to vanish as the regularization parameters are at least greater than 10⁵.     

Galois theory, discriminants and torsion subgroup of elliptic curves

We find a tight relationship between the torsion subgroup and the image of the mod 2 Galois representation associated to an elliptic curve defined over the rationals. This is shown using some characterizations for the squareness of the discriminant of the elliptic curve.     

Non Commutative Functional Calculus: Bounded Operators

In this paper we develop a functional calculus for bounded operators defined on quaternionic Banach spaces. This calculus is based on the new notion of slice-regularity, see Gentili and Struppa (Acad Sci Paris 342:741–744, 2006) and the key tools are a new resolvent operator and a new eigenvalue problem.