Three-body hadronic structure of low-lying 1/2+ Σ and Λ resonances⋆

We discuss the dynamical generation of some low-lying 1/2⁺ Σ 's and Λ 's in two-meson one-baryon systems. These systems have been constructed by adding a pion in the S -wave to the ˉN pair and its coupled channels, where the 1/2^- Λ(1405) -resonance gets dynamically generated. We solve Faddeev equations in the coupled-channel approach to calculate the T -matrix for these systems as a function of the total energy and the invariant mass of one of the meson-baryon pairs. This squared T -matrix shows peaks at the energies very close to the masses of the strangeness -1 , 1/2⁺ resonances listed in the particle data book.     

Multilinear Calderón-Zygmund Theory

A systematic treatment of multilinear Calderón-Zygmund operators is presented. The theory developed includes strong type and endpoint weak type estimates, interpolation, a multilinear T1 theorem, and a variety of results regarding multilinear multiplier operators.     

Experiments to detect long-range heteronuclear shift correlations: LR-J-HSMQC

The utility of the J-HSMQC experiment to detect long-range CH correlations was investigated. Two new long-range J-compensated pulse sequences, LR-J-HSMQC(80,27) and LR-J-HSMQC(27,80), were developed using the (3beta(x))beta(y) composite 90 degrees pulse sequence. These two experiments were shown to be effective for long-range coupling constants, (n)J(CH), that were greater than 3 Hz. Although the overall sensitivities of the long-range J-HSMQC experiments were slightly lower than that of the conventional decoupled HMBC experiment, their 2D maps showed additional cross peaks that could be useful in structure elucidation. LR-J-HSMQC(27,80) was very efficient in yielding two- and four-bond relay correlations. The utility of the new sequences is demonstrated with strychnine as the sample.     

Neural Networks in Which Synaptic Patterns Fluctuate with Time

We study a stochastic neural-network model in which neurons and synapses change with a priori probability p and 1–p, respectively, in the limit p0. This implies neuron activity competing with fast fluctuations of the synaptic connections—in fact, random oscillations around values given by a learning (for example, Hebb's) rule. The consequences for the system performance of a dynamics constantly checking at random the set of memorized patterns is thus studied both analytically and numerically. We describe various nonequilibrium phase transitions whose nature depends on the properties of fluctuations. We find, in particular, that under rather general conditions locally stable mixture states do not occur, and pattern recognition and retrieval processes are substantially improved for some classes of synaptic fluctuations.     

Observation of a nonlinear mode in a cylindrical Fabry-Perot cavity

We report what is believed to be the first observation of a nonlinear mode in a cylindrical nonlinear Fabry-Perot cavity. The field enhancement from cavity buildup, as well as the large chi((3)) optical nonlinearity that is due to resonantly excited (85)Rb vapor, allows the nonlinear mode to form at low incident optical powers of less than 1 mW. The mode is observed to occur for both self-focusing and self-defocusing nonlinearity.     

Fluorescence properties of some schiff's bases derived from 3-hydroxypyridine-2-aldehyde and of their metal chelates Fluorimetric determination of manganese based on its catalytic effect on the oxidation of these compounds with hydrogen peroxide

The fluorimetric properties of the oxime, thiosemicarbazone, azine and 2-pyridylhydrazone of 3-hydroxypyridine-2-aldehyde have been studied; quantum yields have been measured in ethanol-water and ethanol-dimethylformamide media. Two kinetic methods are described for the determination of trace amounts of manganese(II), based on its catalytic effect on the oxidation of the thiosemicarbazone and of the azine by hydrogen peroxide. The reactions are followed by measuring the rate of change of the fluorescence. The calibration graph is linear over the manganese range 5-50 ng ml with a precision of +/- 3.0% for the thiosemicarbazone, and 0.4-0.9 mug ml with a precision of +/-2.0% for the azine. Interferences by foreign ions have been investigated.     

Indices de refraction et birefringence spontanee de l'orthophosphate de plomb ferroelastique

Refraction indices at room temperature and the temperature dependence of the spontaneous birefringence have been measured in ferroelastic lead orthophosphate. The 180°C phase transition in this material has been determined as a thermodynamic first order transition.     

Direct imaging of Cu dimer formation, motion, and interaction with Cu atoms on Ag(111)

We have investigated the formation and motion of copper adatoms and addimers on Ag(111) between 6 and 25 K with low-temperature scanning tunneling microscopy. The presence of atoms and dimers alters the motion of atoms and dimers via the long-range interaction mediated by the electrons in the two-dimensional surface state band. Above 16 K, dimers show quantum rotor behavior with altered rotational behavior in the presence of an additional adatom. The most favorable diffusional motion of the dimer is identified in combination with molecular dynamics calculations to be a zigzag out-of-cell motion starting above 24 K.     

Cluster formation and laser-induced effects in the ablation of 2Cu(CO3)·Cu(OH)2. Time-of-flight mass spectrometric study

The mechanism of laser ablation of 2Cu(CO₃)·Cu(OH)₂ at 308 nm is investigated by time-of-flight mass spectroscopy at laser fluences in the range of 0.07 to 0.6 Jcm^-2. The neutral and ion composition of the plume reveals the presence of Cu, Cu₂O, CuO, H₂O and CO₂, which appear as free species or forming clusters. Plume composition is compatible with a thermal ablation mechanism which involves chemical processes similar to those reported for the purely thermal decomposition of the target. Velocity distributions of neutral species in the plume are measured and fitted to shifted Maxwell–Boltzmann time distributions; the best fitting yields flow velocities of 0.07 cms^-1 for CO₂ and Cu and 0.04 cms^-1 for Cu₂, which is compatible with an expansion regime characterized by weak interaction of the ejected particles. PACS 82.30.Nr; 78.70.-g