Chiral recognition by mass-resolved laser spectroscopy

Chiral recognition is a fundamental phenomenon in life sciences, based on the enantioselective complexation of a chiral molecule with a chiral selector. The diastereomeric aggregates, formed by complexation, are held together by a different combination of intermolecular forces and are therefore endowed with different stability and reactivity. Determination of these forces, which are normally affected in the condensed phase by solvent and supramolecular interactions, requires the generation of the diastereomeric complexes in the isolated state and their spectroscopic investigation. This review deals with chiral recognition in the gas phase through the application of laser-resolved mass spectrometric techniques (R2PI-TOF and RET-MS). The measurement of the fragmentation thresholds of diastereomeric clusters by these techniques allows the determination of the nature of the intrinsic interactions, which control their formation and affect their stability and reactivity.     

Numerical simulation of ballistic surface transport in cylindrical nanosystems

We study, by numerical simulations, the effect of topology on coherent electron transport through cylindrical junctions and bent cylindrical surfaces. The dynamics of a particle bound to a curved surface is described by a modified Schrödinger equation depending on two curvilinear coordinates. The modeling approach based on a finite-difference discretization of the latter equation is described, and a comparison with the standard solution of Schrödinger equation for flat surfaces is given. The effect of the geometrical parameters of the structures is reported.     

Effects of training in sentence construction on the comprehension of learning disabled children.

30 learning-disabled Hispanic, White, and Black children (mean IQ 88.60 and mean age 11.73 yrs) were randomly assigned to 2 conditions focusing on sentence comprehension: a sentence anagram/word grouping treatment and a more traditional sentence study treatment. With age, IQ, and pretest comprehension (Gates-MacGinitie Reading Tests) controlled, Ss in the sentence anagram/word grouping condition had significantly higher cloze scores than Ss in the sentence study group. The greatest achievement benefits associated with the anagram treatment, however, accrued to Ss with higher initial reading achievement. As level of pretreatment achievement decreased, the magnitude of the treatment differences also tended to decrease. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Palladium Catalytic Species Containing Chiral Phosphites: Towards a Discrimination between Molecular and Colloidal Catalysts

Palladium nanoparticles ( Pd1 – Pd3 ) stabilized by chiral diphosphite ligands ( 1 – 3 ), were synthesized and tested as catalysts for the allylic alkylation reaction, using different substrates (rac‐ I , rac‐ III and rac‐ V ). Carbohydrate ligands ( 1 and 2 ), only differing in the C‐3 configuration, led to a remarkable difference in stability of the corresponding nanoparticles: while Pd1 is a robust catalyst, Pd2 decomposes into molecular species. In addition, the high enantioselective systems, Pd1 and Pd3 , are only active for a substrate containing phenyl groups. Concerning the catalytic behaviour of the corresponding molecular systems, palladium complexes coordinated to ligands 1 or 3 , gave excellent asymmetric inductions, but an analogous catalyst accommodating ligand 2 , was not found selective.     

Effects of Ozone on Resin Acids in Thermomechanical Pulp and Paper Mill Circulation Waters

The present study investigated ozonation as means to remove resin acids from pulp and paper mill circulation waters. Ozone selectively oxidizes resin acids in debarking, thermomechanical pulping (TMP), and newsprint machine (PM) circulation waters. The relative ozone dose of 0.2 mgO₃/initial mgCOD eliminated over 90% of total resin acid concentration in all tested waters, despite the initial resin acid or organic matter concentration. With that ozone dose, the removal of organic material (measured as COD) was only about 30%. Because of the different COD concentrations of tested waters, the absolute amount of ozone needed for over 90% resin acid reduction was 2000 mg/1 for debarking water, 600 mg/1 for TMP water, and 300 mg/1 for PM water, when initial COD concentrations were 10,000, 3000, and 1500 mg/1, respectively. In theory, abietane type resin acids should be more susceptible to ozone attack than pimarane type resin acids, because of their conjugated double bond structure. In the experiments, a high oxidizability of pimarane type resin acids, as compared to abietane type resin acids, was found.     

Variable order metrics for decision diagrams in system verification

International Journal on Software Tools for Technology Transfer - Decision diagrams (DDs) are widely used in system verification to compute and store the state space of finite discrete events...     

Matrix Addressing of an Electronic Surface Switch Based on a Conjugated Polyelectrolyte for Cell Sorting

Spatial control of cell detachment is potentially of great interest when selecting cells for clonal expansion and in order to obtain a homogeneous starting population of cells aimed for tissue engineering purposes. Here, selective detachment and cell sorting of human primary keratinocytes and fibroblasts is achieved using thin films of a conjugated polymer. Upon electrochemical oxidation, the polymer film swells, cracks, and finally detaches taking cells cultured on top along with it. The polymer can be patterned using standard photolithography to fabricate a cross‐point matrix with polymer pixels that can be individually addressed and thus detached. Detachment occurs above a well‐defined threshold of +0.7 V versus Ag/AgCl, allowing the use of a relatively simple and easily manufactured passive matrix‐addressing configuration, based on a resistor network, to control the cell‐sorting device.     

Functional nanocomposites with graphene-DNA hybrid fillers: Synthesis and surface properties under UV irradiation

In this work, nanocomposites containing assemblies of graphene nanoplatelets (GNP) and double-stranded DNA are investigated as UV-sensitive materials, as they show good electrical properties combined with the chemical sensitivity of DNA to UV radiation, particularly to the more energetic UV-C band. Nanocomposite films were prepared by drop-casting technique after embedding the graphene-DNA fillers in a flexible polydimethylsiloxane (PDMS) matrix using a suitable solvent. The synthesis was optimized in order to improve the dispersion of the graphene-DNA elements in the polymer matrix, as the sensing properties of the nanocomposite materials are highly affected by the amount and homogeneity of the filler dispersion. The electrical and thermal properties of the GNP-DNA/PDMS films, as well as their surface morphology and wettability, were investigated before and after exposure to UV-C radiation using complementary techniques. Results give information on the potential applications of these novel functional nanocomposites for radiation monitoring in environments that are characterized by high levels of biologically-damaging UV radiation.