Catalytic and Atom‐Economic C −C Bond Formation: Alkyl Tantalum Ureates for Hydroaminoalkylation

Atom‐economic and regioselective C ?C bond formation has been achieved by rapid C?H alkylation of unprotected secondary arylamines with unactivated alkenes. The combination of Ta(CH₂SiMe₃)₃Cl₂, and a ureate N,O‐chelating‐ligand salt gives catalytic systems prepared in situ that can realize high yields of β‐alkylated aniline derivatives from either terminal or internal alkene substrates. These new catalyst systems realize C?H alkylation in as little as one hour and for the first time a 1:1 stoichiometry of alkene and amine substrates results in high yielding syntheses of isolated amine products by simple filtration and concentration.     

Twist-grain boundary phase induced by Au nanoparticles in a chiral liquid crystal host

We report on the stabilisation of the liquid-crystalline, twist-grain boundary A (TGB_A) phase in mixtures of a chiral liquid crystal and surface-functionalised spherical Au nanoparticles (NPs) of 10 nm diameter. The results, obtained by calorimetric, optical, small-angle X-ray and plasmon resonance measurements, demonstrate that a TGB_A phase, which is metastable for the pure liquid crystal host, can be effectively stabilised for a 3 K range in the presence of NPs. Moreover, the role of NPs size on the TGB_A stabilisation is briefly discussed.     

Associating divisors with quadratic differentials on Klein surfaces

We extend the notion and basic properties of quadratic differential divisors to a Klein surface, using the corresponding form’s divisors from the double cover of the Klein surface.     

An Area Preserving Projection from the Regular Octahedron to the Sphere

In this paper, we propose an area preserving bijective map from the regular octahedron to the unit sphere ${\mathbb{S}^2}$ , both centered at the origin. The construction scheme consists of two steps. First, each face F _i of the octahedron is mapped to a curved planar triangle ${\mathcal{T}_i}$ of the same area. Afterwards, each ${\mathcal{T}_i}$ is mapped onto the sphere using the inverse Lambert azimuthal equal area projection with respect to a certain point of ${\mathbb{S}^2}$ . The proposed map is then used to construct uniform and refinable grids on a sphere, starting from any triangular uniform and refinable grid on the triangular faces of the octahedron.     

Penalty variable sample size method for solving optimization problems with equality constraints in a form of mathematical expectation

Numerical Algorithms - Equality-constrained optimization problems with deterministic objective function and constraints in the form of mathematical expectation are considered. The constraints are...     

Minimum Disparity Estimation in Linear Regression Models: Distribution and Efficiency

This paper deals with the minimum disparity estimation in linear regression models. The estimators are defined as statistical quantities which minimize the blended weight Hellinger distance between a weighted kernel density estimator of errors and a smoothed model density of errors. It is shown that the estimators of the regression parameters are asymptotic normally distributed and efficient at the model if the weights of the density estimators are appropriately chosen.     

Assessment of angiogenesis: implications for ultrasound imaging

In this paper, the fundamentals of tumor angiogenesis and the implications for ultrasound imaging will be described. Twenty-eight athymic nude mice were implanted with the human melanoma cell lines DB-1 or MW-9 (14 mice/group). Ultrasound contrast agents were injected in the tail veins. Power Doppler and pulse inversion harmonic imaging (PI-HI) was performed (in real time and intermittently). Ultrasound results were compared to immunohistochemical stains for endothelial cells (CD31), vascular endothelial growth factor (VEGF), and cyclooxygenase-2 (COX-2). Linear regression analysis indicated statistically significant correlations between percent area stained with COX-2 and with VEGF relative to power Doppler (p<0.05) and intermittent PI-HI (p<0.05) measures of tumor neovascularity in the MW-9 and the DB-1 mice, respectively. Preliminary results from a human trial of the anti-angiogenic drug Angiostatin (Entremed, Rockville, MD) showed tumor volumes increased in two patients, while the vascularity remained virtually unchanged. Conversely, in three patients with diminished tumor volumes vascularity increased by 38%. In conclusion, contrast enhanced ultrasound imaging of tumor neovascularity may provide noninvasive markers of angiogenesis and may become a useful tool for monitoring anti-angiogenic therapies in vivo.     

Σ- atoms and the ΣN interaction

It is shown that among four models of the Nijmegen baryon-baryon interaction only model F --which leads to a repulsive potential felt by the Σ hyperon inside the nucleus-- is consistent both with the analysis of Σ^- atoms and of the (K ^-,π) reactions. The Nijmegen models are used to determine the strong complex single-particle (s.p.) potential of Σ^-, and to calculate the strong-interaction shifts and widths of the lowest observed levels of Σ^- atoms. The results obtained with model F are in best agreement with the experimental data. Received: 15 January 2002 / Accepted: 14 March 2002     

Influence of Morphological Homogeneity of Superspherical Gold Nanoparticles on Plasmonic Photothermal Heat Generation

The plasmonic photothermal (PPT) characteristics of gold nanostructures have been extensively investigated theoretically and experimentally due to their potential for use materials science and industry. The management of the size and shape of gold nanoparticles has been a key issue in the development of better solutions for PPT heat generation because their size and shape determine their resultant photothermal properties. However, the light absorption of gold nanostructures is mainly dependent on the wavelength and orientation of the incident light; hence, maintaining uniform size and shape is critical for achieving maximum photothermal energy. Morphologically homogeneous spherical gold nanoparticles, or super gold nanospheres prepared by slowly etching uniform octahedral gold nanoparticles, demonstrate better PPT heat generation compared with commercially available nonsmooth gold nanoparticles (GNSs). The PPT heating experiments show a maximum temperature difference of 5.7 °C between the super and ordinary GNSs with the same average maximum Feret's diameters, which result from the more efficient PPT heat power generation (20.6%) of the super GNSs. In an electromagnetic‐wave simulation, the super GNSs show lower polarization dependence and a 24.6% higher absorption cross‐section than ordinary GNSs.