Allylpalladium umpolung in the three-component coupling synthesis of homoallylic amines

[Structure: see text] Homoallylic amines and alpha-amino esters were prepared via a Pd(II)-catalyzed coupling of boronic acids and 1,2-nonadiene with ethyl iminoacetate or aliphatic, aromatic, and heteroaromatic imines. The allylpalladium umpolung was induced by a Pd(OAc)2 catalyst with commercial phosphine ligands.     

Nanostructured Zr/Hf/Zr multilayer studied by perturbed angular correlations technique

In this work the perturbed angular correlation technique is used to locally monitor the epitaxy and thermal stability of the hafnium layer in a Zr/Hf/Zr multilayer. The studies reveal that the system is highly homogeneous and presents high epitaxy. Measurements at high temperatures show that no HfO_x formation occurs up to 562 K but at this temperature the Hf layer is no longer oxygen-defect free.     

Perturbed angular correlations investigations on YMnO3 multiferroic manganite

The Perturbed Angular Correlation (PAC) technique was applied to study the yttrium local environment in YMnO₃ multiferroic manganite. The electric field gradients (EFG) at the Y site have been measured as function of temperature, covering both ferroelectric and magnetic transitions. The results were compared with point charge model (PCM) calculations. The experimental results show two different EFG distributions for all temperatures. Only one can be directly attributed to the yttrium crystalline site in the hexagonal structure.     

Synchronization time in a hyperbolic dynamical system with long-range interactions

We show that the threshold of complete synchronization in a lattice of coupled non-smooth chaotic maps is determined by linear stability along the directions transversal to the synchronization subspace. We examine carefully the synchronization time and show that an inadequate observation of the system evolution leads to wrong results. We present both careful numerical experiments and a rigorous mathematical explanation confirming this fact, allowing for a generalization involving hyperbolic coupled map lattices.     

Intrinsic Fluorescence of Protoporphyrin IX from Blood Samples Can Yield Information on the Growth of Prostate Tumours

Prostate cancer is one of the most common types of cancer in men, and unfortunately many prostate tumours remain asymptomatic until they reach advanced stages. Diagnosis is typically performed through Prostate-Specific Antigen (PSA) quantification, Digital Rectal Examination (DRE) and Transrectal Ultrasonography (TU). The antigen (PSA) is secreted by all prostatic epithelial cells and not exclusively by cancerous ones, so its concentration also increases in the presence of other prostatic diseases. DRE and TU are not reliable for early detection, when histological analysis of prostate tissue obtained from a biopsy is necessary. In this context, fluorescence techniques are very important for the diagnosis of cancer. In this paper we explore the potential of using endogenous phorphyrin blood fluorescence as tumour marker for prostate cancer. Substances such as porphyrin derivatives accumulate substantially more in tumours than in normal tissues; thus, measuring blood porphyrin concentration by autofluorescence intensity may provide a good parameter for determining tumour stage. In this study, the autofluorescence of blood porphyrin was analyzed using fluorescence and excitation spectroscopy on healthy male NUDE mice and in those with prostate cancer induced by inoculation of DU145 cells. A significant contrast between the blood of normal and cancer subjects could be established. Blood porphyrin fluorophore showed an enhancement on the fluorescence band around 632 nm following tumour growth. Fluorescence detection has advantages over other light-based investigation methods: high sensitivity, high speed and safety. However it does carry the drawback of low specificity of detection. The extraction of blood porphyrin using acetone can solve this problem, since optical excitation of further molecular species can be excluded, and light scattering from blood samples is negligible.     

Observation of postsoliton expansion following laser propagation through an underdense plasma

The expansion of electromagnetic postsolitons emerging from the interaction of a 30 ps, 3×101? W?cm?2 laser pulse with an underdense deuterium plasma has been observed up to 100 ps after the pulse propagation, when large numbers of postsolitons were seen to remain in the plasma. The temporal evolution of the postsolitons has been accurately characterized with a high spatial and temporal resolution. The observed expansion is compared to analytical models and three-dimensional particle-in-cell results, revealing a polarization dependence of the postsoliton dynamics.     

Vanishing viscosity limits and boundary layers for circularly symmetric 2D flows

We continue the work of Lopes Filho, Mazzucato and Nussenzveig Lopes [10] on the vanishing viscosity limit of circularly symmetric viscous flow in a disk with rotating boundary, shown there to converge to the inviscid limit in L ²-norm as long as the prescribed angular velocity α(t) of the boundary has bounded total variation. Here we establish convergence in stronger L ² and L ^p -Sobolev spaces, allow for more singular angular velocities α, and address the issue of analyzing the behavior of the boundary layer. This includes an analysis of concentration of vorticity in the vanishing viscosity limit. We also consider such flows on an annulus, whose two boundary components rotate independently. Supported in part by NSF grant DMS-0456861.     

A supercloseness result for the discontinuous Galerkin stabilization of convection–diffusion problems on Shishkin meshes

We consider a convection–diffusion problem with Dirichlet boundary conditions posed on a unit square. The problem is discretized using a combination of the standard Galerkin FEM and an h–version of the nonsymmetric discontinuous Galerkin FEM with interior penalties on a layer–adapted mesh with linear/bilinear elements. With specially chosen penalty parameters for edges from the coarse part of the mesh, we prove uniform convergence (in the perturbation parameter) in an associated norm. In the same norm we also establish a supercloseness result. Numerical tests support our theoretical estimates.© 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007     

On Quasi-Hopf Smash Products and Twisted Tensor Products of Quasialgebras

We analyze some relations between quasi-Hopf smash products and certain twisted tensor products of quasialgebras. Along the way we obtain also some results of independent interest, such as a duality theorem for finite dimensional quasi-Hopf algebras and a universal property for generalized diagonal crossed products.