Ferromagnetic Mn-doped Si0.3Ge0.7 nanodots self-assembled on Si(100)

Densely packed epitaxial Mn-doped Si(0.3)Ge(0.7) nanodots self-assembled on Si(100) have been obtained. Their structural properties were studied using reflection high-energy electron diffraction, energy dispersive x-ray diffraction, atomic force microscopy, extended x-ray absorption fine structure measurements and high-resolution transmission electron microscopy. Mn(5)Ge(1)Si(2) crystallites embedded in Si(0.3)Ge(0.7) were found. They exhibit a ferromagnetic behaviour with a Curie temperature of about 225?K.     

The highest water exchange rate ever measured for a Gd(III) chelate

The complex [Gd(L)(H2O)]3- (H(6)L =N,N'-bis(6-carboxy-2-pyridylmethyl)ethylenediamine-N,N'-methylenephosphonic acid) displays the highest water exchange rate ever measured for a Gd(III) chelate (k(298)(ex)= 8.8 x 10(8) s(-1)), which is attributed to the flexibility of the metal coordination environment.     

Separable and additive representations of binary gambles of gains

Two approaches are taken to a new utility representation of binary gambles that is called “ratio rank-dependent utility.” Both are based on known axiomatizations of a ranked-additive representation of consequence pairs (x, y) in binary gambles (x, C; y) of gains with C held fixed and of a separable one of the special gambles (x, C; e), where e denotes the status quo. The axiomatized version imposes the condition of status-quo event commutativity to get a functional equation that leads to the result. The other assumes, but does not axiomatize, a separable representation of the (C; y) portion of the gamble. These assumptions lead to two difficult functional equations that are solved in the mathematical literature, but the former only under the assumption that the function is twice differentiable. Three behavioral conditions are shown to force this new utility representation to reduce to the standard rank-dependent utility one for gains. They are co-monotonic trade-off consistency, ranked bisymmetry, and segregation, the latter requiring the addition of an operation of joint receipt.     

Modulation of Relaxivity,Suspension Stability,and Biodistribution of Dendronized Iron Oxide Nanoparticles as a Function of the Organic Shell Design

Nanoparticles (NPs) with a mean diameter of 10 nm are functionalized with three dendrons: D1 a PEGylated PAMAM dendron of generation 0.5, D2 a hydrophilic oligoethyleneglycol‐derivatized dendron (D2) displaying a phosphonic acid at the focal point, and D2–2P the same dendron than D2 but with two phosphonic acid anchoring agents. Their grafting is confirmed by IR spectroscopy and elemental analysis. All dendronized NPs are stable over a long period of time in suspensions in water and in different physiological media and display a mean hydrodynamic diameter smaller than 50 nm whatever the molecule architecture. NMRD profiles and relaxivity measurements highlight the influence of the molecule architecture on the water diffusion close to the magnetic core thus influencing the relaxation properties at low magnetic field. The high hydrophilic architecture of the dendron D2 by contrast to dendron D1 allows maintaining the colloidal stability in different conditions while ensuring a very good accessibility of water molecule close to the magnetic core. Coupling of a fluorescent dye on dendrons have allowed investigating the biodistribution of dendronized NPs, which are found to be quickly eliminated through urinary and hepatobiliary pathways within 4 h. Furthermore, no enhanced permeation and retention effect in tumors can be observed.     

Zeolite GdNaY nanoparticles with very high relaxivity for application as contrast agents in magnetic resonance imaging

In this paper we explore Gd(3+)-doped zeolite NaY nanoparticles for their potential application as a contrast agent in magnetic resonance imaging (MRI). The nanoparticles have an average size of 80-100 nm, as determined by TEM and XRD. A powdered sample loaded with La3+ was characterised by means of multinuclear solid-state NMR spectroscopy. The NMR dispersion (NMRD) profiles obtained from aqueous suspensions of samples with Gd3+ doping ratios of 1.3-5.4 wt% were obtaining at different temperatures. The relaxivity increases drastically as the Gd3+ loading decreases, with values ranging between 11.4 and 37.7 s-1 mM-1 at 60 MHz and 37 degrees C. EPR spectra of aqueous suspensions of the samples suggest that an interaction between neighbouring Gd3+ ions within the same particle produces a significant increase in the transversal electronic relaxation rates in samples with a high Gd3+ content. The experimental NMRD and EPR data are explained with the use of a model that considers the system as a concentrated aqueous solution of Gd3+ in the interior of the zeolite that is in exchange with the bulk water outside the zeolite. The results obtained indicate that the Gd3+ ion is immobilised in the interior of the zeolite and that the relaxivity is mainly limited by the relatively slow diffusion of water protons from the pores of the zeolite channels into the bulk water.     

On the rational approximation of Markov functions,with applications to the computation of Markov functions of Toeplitz matrices

Numerical Algorithms - We investigate the problem of approximating the matrix function f(A) by r(A), with f a Markov function, r a rational interpolant of f, and A a symmetric Toeplitz matrix. In a...     

Infrared near-field microscopy with the Vanderbilt free electron laser: overview and perspectives

Scanning near-field optical microscopy (SNOM) makes it routinely possible to overcome the fundamental diffraction limit of standard (far-field) microscopy. Recently, aperture-based infrared SNOM performed in the spectroscopic mode, using the Vanderbilt University free electron laser, started delivering spatially-resolved information on the distribution of chemical species and on other laterally-fluctuating properties. The practical examples presented here show the great potential of this new technique both in materials science and in life sciences.