Practical enantiospecific syntheses of (+) erythro-9- (2s-hydroxy-3r-nonyl) adenine.

Three enantiospecific syntheses of 1S (2S-benzyloxethyl) oxirane (9) from L-ascorbic acid, L(+) tartaric acid, and Z-butene 1,4-diol are reported. The conversion of 9 to 2S-hydroxy-3R-nonylamine (19) is also described.     

Performance replication of the Spot Energy Index with optimal equity portfolio selection: Evidence from the UK,US and Brazilian markets

This paper reproduces the performance of a geometric average Spot Energy Index by investing only in a subset of stocks from the Dow Jones Composite Average, the FTSE 100 and Bovespa Composite indexes, and in two pools that include only energy-sector stocks from the US and the UK respectively. Daily data are used and the index-tracking problem for passive investment is addressed with two evolutionary algorithms – the differential evolution algorithm and the genetic algorithm. The performance of the suggested investment strategy is tested under three different scenarios: buy-and-hold, quarterly and monthly rebalancing, accounting for transaction costs where necessary.     

Adsorption of Remazol Red 3BS from aqueous solutions using APTES- and cyclodextrin-modified HMS-type mesoporous silicas

The removal of Remazol Red 3BS (C.I. 239) dye by HMS ordered mesoporous silica, aminopropyl-modified HMS (HMS-NH₂) and β-cyclodextrin-modified HMS (HMS-CD) materials was studied in the present work. The modified materials were functionalized in situ by adding the organic modifiers (3-aminopropyltriethoxysilane and a silylated derivative of MCT-β-CD) in the synthesis mixture and using dodecylamine as the mesopore structure directing agent. The successful incorporation of aminopropyl groups in HMS-NH₂ and of cyclodextrin moieties in HMS-CD was verified by means of FT-IR spectroscopy, elemental analysis and N₂ porosimetry. The HMS-CD material exhibited significantly higher adsorption capacity compared to that of the HMS-NH₂ material, while the parent HMS mesoporous silica showed negligible adsorption capability. The maximum adsorption capacities obtained (at the optimum pH 2) on the basis of the Langmuir analysis were 0.28 mmol/g for HMS-CD and 0.14 mmol/g for HMS-NH₂. It was shown that the HMS-CD sorbent can be effectively regenerated by the surfactant-enhanced regeneration method using SDS and that can be reused without significant loss of its adsorption capabilities.     

Threshold for the volume spanned by random points with independent coordinates

Let μ be an even compactly supported Borel probability measure on the real line. For every N > n consider N independent random vectors X ₁, ..., X _N in ℝ ⁿ , with independent coordinates having distribution μ. We establish a sharp threshold for the volume of the random polytope K _N ≔ conv{X ₁, ..., X _N }, provided that the Legendre transform λ of the cumulant generating function of μ satisfies the condition

Asymptotic shape of a random polytope in a convex body

Let K be an isotropic convex body in and let Z_q(K) be the L_q-centroid body of K. For every N>n consider the random polytope K_N:=conv{x₁,…,x_N} where x₁,…,x_N are independent random points, uniformly distributed in K. We prove that a random K_N is “asymptotically equivalent” to Z_[ln(N/n)](K) in the following sense: there exist absolute constants ρ₁,ρ₂>0 such that, for all and all NN(n,β), one has:

(i) K_Nc(β)Z_q(K) for every qρ₁ln(N/n), with probability greater than 1−c₁exp(−c₂N^1−βn^β).

(ii) For every qρ₂ln(N/n), the expected mean width of K_N is bounded by c₃w(Z_q(K)).

As an application we show that the volume radius |K_N|^1/n of a random K_N satisfies the bounds for all Nexp(n).

High-resolution 3D MR spectroscopic imaging of the prostate at 3 T with the MLEV-PRESS sequence

A 3 T MLEV-point-resolved spectroscopy (PRESS) sequence employing optimized spectral-spatial and very selective outer-voxel suppression pulses was tested in 25 prostate cancer patients. At an echo time of 85 ms, the MLEV-PRESS sequence resulted in maximally upright inner resonances and minimal outer resonances of the citrate doublet of doublets. Magnetic resonance spectroscopic imaging (MRSI) exams performed at both 3 and 1.5 T for 10 patients demonstrated a 2.08+/-0.36-fold increase in signal-to-noise ratio (SNR) at 3 T as compared with 1.5 T for the center citrate resonances. This permitted the acquisition of MRSI data with a nominal spatial resolution of 0.16 cm3 at 3 T with similar SNR as the 0.34-cm3 data acquired at 1.5 T. Due to the twofold increase in spectral resolution at 3 T and the improved magnetic field homogeneity provided by susceptibility-matched endorectal coils, the choline resonance was better resolved from polyamine and creatine resonances as compared with 1.5 T spectra. In prostate cancer patients, the elevation of choline and the reduction of polyamines were more clearly observed at 3 T, as compared with 1.5 T MRSI. The increased SNR and corresponding spatial resolution obtainable at 3 T reduced partial volume effects and allowed improved detection of the presence and extent of abnormal metabolite levels in prostate cancer patients, as compared with 1.5 T MRSI.     

Nonlinear radial oscillations of encapsulated microbubbles subject to ultrasound: the effect of membrane constitutive law

The nonlinear radial oscillations of bubbles that are encapsulated in an elastic shell are investigated numerically subject to three different constitutive laws describing the viscoelastic properties of the shell: the Mooney-Rivlin (MR), the Skalak (SK), and the Kelvin-Voigt (KV) models are used in order to describe strain-softening, strain-hardening and small displacement (Hookean) behavior of the shell material, respectively. Due to the isotropic nature of the acoustic disturbances, the area dilatation modulus is the important parameter. When the membrane is strain softening (MR) the resonance frequency decreases with increasing sound amplitude, whereas the opposite happens when the membrane is strain hardening (SK). As the amplitude of the acoustic disturbance increases the total scattering cross section of a microbubble with a SK membrane tends to decrease, whereas that of a KV or a MR membrane tends to increase. The importance of strain-softening behavior in the abrupt onset of volume pulsations, that is often observed with small insonated microbubbles at moderately large sound amplitudes, is discussed.     

Fabrication of complex three-dimensional nanostructures from self-assembling block copolymer materials on two-dimensional chemically patterned templates with mismatched symmetry

A study is presented of the self-assembly of a lamella-forming blend of a diblock copolymer and its respective homopolymers on periodically patterned substrates consisting of square arrays of spots, that preferentially attract one component, as a function of pattern dimensions and film thickness. The blend morphology follows the pattern at the substrate and forms a single quadratically perforated lamella (QPL). At intermediate film thicknesses necks connect this QPL to the film surface, resulting in a bicontinuous morphology. The necks do not register with the underlying square lattice but exhibit a substantial amount of hexagonal short-range order. For thicker films we observe bicontinuous morphologies consisting of parallel lamellae with disordered perforations. These results demonstrate a promising strategy for the fabrication of complex interfacial nanostructures from two-dimensional chemically patterned templates.     

On a local version of the Aleksandrov-Fenchel inequality for the quermassintegrals of a convex body

We discuss the analogue in the Brunn-Minkowski theory of the inequalities of Marcus-Lopes and Bergstrom about symmetric functions of positive reals and determinants of symmetric positive matrices respectively. We obtain a local version of the Aleksandrov-Fenchel inequality which relates the quermassintegrals of a convex body to those of an arbitrary hyperplane projection of . A consequence is the following fact: for any convex body , for any -dimensional subspace of and any 0$">,

where denotes the Euclidean unit ball and denotes volume in the appropriate dimension.