Matter-wave localization in disordered cold atom lattices

We propose to observe Anderson localization of ultracold atoms in the presence of a random potential made of atoms of another species or spin state and trapped at the nodes of an optical lattice, with a filling factor less than unity. Such systems enable a nearly perfect experimental control of the disorder, while the possibility of modeling the scattering potentials by a set of pointlike ones allows an exact theoretical analysis. This is illustrated by a detailed analysis of the one-dimensional case.     

Upper Bound on the Decay of Correlations in a General Class of O(N)-Symmetric Models

We consider a general class of two-dimensional spin systems, with continuous but not necessarily smooth, possibly long-range, O(N)-symmetric interactions, for which we establish algebraically decaying upper bounds on spin-spin correlations under all infinite-volume Gibbs measures. As a by-product, we also obtain estimates on the effective resistance of a (possibly long-range) resistor network in which randomly selected edges are shorted.     

Universality and Conformal Invariance for the Ising Model in Domains with Boundary

The partition function with boundary conditions for various two-dimensional Ising models is examined and previously unobserved properties of nonformal invariance and universality are established numerically.     

A Stereoselective Approach to β-l-Arabino Nucleoside Analogues: Synthesis and Cyclization of Acyclic 1',2'-synN,O-Acetals

Reported herein is a novel and versatile strategy for the stereoselective synthesis of unnatural β-l-arabinofuranosyl nucleoside analogues from acyclic N,OTMS-acetals bearing pyrimidine and purine bases. These unusual acetals undergo a C1' to C4' cyclization where the OTMS of the acetal serves as the nucleophile to generate 2'-oxynucleosides with complete retention of configuration at the C1' acetal center. N,OTMS-acetals are obtained diastereoselectively from additions of silylated nucleobases onto acyclic polyalkoxyaldehydes in the presence of MgBr(2)·OEt(2). The strategy reported is addressing important synthetic challenges by providing stereoselective access to unnatural l-nucleosides starting from easily accessible pools of d-sugars and, as importantly, by allowing the formation of the sterically challenging 1',2'-cis nucleosides. A wide variety of nucleoside analogues were synthesized in 7-8 steps from easily accessible d-xylose.     

Amylose-3,5-dimethylphenylcarbamate immobilized on monolithic silica stationary phases for chiral separations in capillary electrochromatography

Chiral monolithic silica capillary columns were prepared by immobilization of amylose-3,5-dimethylphenylcarbamate (ADMPC) bearing a small fraction of 3-(triethoxysilyl)propyl residues through intermolecular polycondensation of the triethoxysilyl groups. The obtained columns were used for chiral separations in capillary electrochromatography (CEC). The effects of the silica monolith nature and the used chiral selector concentration on the resulting enantiomeric separations were investigated. Fifteen chiral compounds, including acidic, neutral, and basic substances were evaluated and twelve showed partial or baseline separation at some of the different conditions tested. These results demonstrated the promising applicability of ADMPC-immobilized monolithic silica columns in CEC enantioseparations, but also revealed the need for further improvements on the level of baseline separations and efficiencies.     

Efficient recovery of electrophoretic profiles of nucleoside metabolites from urine samples by multivariate curve resolution

Chemometric techniques usually employed in purity assessment and resolution of multicomponent peaks have been applied to analytical data from complex biological samples obtained with CE‐DAD. In the assessment of the purity of the electrophoretic peaks, the orthogonal projection approach, the orthogonal projection approach with Durbin–Watson criterion, and the simple‐to‐use interactive self‐modeling mixture analysis method have been employed. Multivariate curve resolution with alternating least squares has been successfully implemented to resolve co‐migrating peaks of metabolites in CE‐DAD and to recover qualitative and quantitative information about co‐migrating components of urine extract. The main challenge consisted of developing high‐quality multivariate curve resolution with alternating least squares models of multicomponent peaks acquired during the CE analysis of nucleoside patterns in 18 urine samples. The recovered ultraviolet visible (UV–Vis) spectra have been employed to identify additional nucleosides, such as 1‐methylinosine, 2‐methylguanosine, and 1‐methylguanosine, whose presence in the metabolic profile produced by the applied CE‐DAD method has not yet been recognized. Concentration profiles of these compounds can be used in metabonomic studies.     

Aminocyclopropanes as precursors of endoperoxides with antimalarial activity

This contribution describes the synthesis of several novel bicyclic α-amino endoperoxides, including CF(3)-substituted compounds, prepared by the aerobic electrochemical oxidation of a family of bicyclic aminocyclopropanes. These, in turn, are readily synthesised by a titanium-mediated intramolecular cyclopropanation process (Kulinkovich-de Meijere reaction), starting from N-alkenyl amides that contain a vic-disubstituted double bond, with high diastereoselectivity. An evaluation of the biological activities of several of the molecules produced, against the parasite Plasmodium falciparum, is also presented.     

Micellar liquid chromatography for lipophilicity determination of new biologically active 1,3‐purinodiones

A series of newly synthesized 1,3‐purinodiones with potential anticonvulsant activity, exhibiting affinity to adenosine A₁ and/or A_2A receptors, were subjected to micellar LC (MLC) with SDS as micelle‐forming agent and n‐propanol as organic modifier. Two C18 silica‐based columns were employed in MLC: a particle one and a monolithic. In parallel, those derivatives were also analyzed in RP‐LC on four silica‐based columns and on an immobilized artificial membrane column. The correlations between the relevant logarithms of the retention factors of analytes obtained in MLC, immobilized artificial membrane and RP‐LC systems on the one hand, and the calculated log P (clog P) and log D values (clog D) on the other, were examined. The level of the correlations of retention data from MLC and RP‐LC systems with clog P and clog D obtained is similar but it could be stressed that MLC allows increasing the speed of analysis and using only one mobile phase. Moreover, there is no need of applying an extrapolation procedure in lipophilicity determination. Therefore, the MLC systems, providing chromatographic data in a fast and efficient manner, were demonstrated as promising alternatives to the classical RP‐LC systems to estimate the lipophilicity of drugs and drug candidates.     

Classification tree models for the prediction of blood-brain barrier passage of drugs

The use of classification trees for modeling and predicting the passage of molecules through the blood-brain barrier was evaluated. The models were built and evaluated using a data set of 147 molecules extracted from the literature. In the first step, single classification trees were built and evaluated for their predictive abilities. In the second step, attempts were made to improve the predictive abilities using a set of 150 classification trees in a boosting approach. Two boosting algorithms, discrete and real adaptive boosting, were used and compared. High-predictive classification trees were obtained for the data set used, and the models could be improved with boosting. In the context of this research, discrete adaptive boosting gives slightly better results than real adaptive boosting.