Hierarchies from D-brane instantons in globally defined Calabi-Yau orientifolds

We construct the first globally consistent semirealistic type I string vacua on an elliptically fibered manifold where the zero modes of the Euclidean D1-instanton sector allow for the generation of nonperturbative Majorana masses of an intermediate scale. In another class of global models, a D1-brane instanton can generate a Polonyi-type superpotential breaking supersymmetry at an exponentially suppressed scale.     

Isoform separation of a multi-acetylated protein using capillary polystyrene-divinylbenzene monolithic columns

Capillary polystyrene-divinylbenzene (PS-DVB) monolithic columns were used to separate differentially acetylated intact IM9 protein isoforms. Compared to the unmodified form, the hydrophobic shift for intact acetylated isoforms was significant under standard reversed-phase conditions (32.5-45% acetonitrile in 10 min). The high chromatographic resolution of the PS-DVB monolithic columns resulted in peak widths at half height of 4-5s. This allowed us to nearly completely resolve a number of peaks greater than the number of possible acetylation sites. This observation suggested that not only the number, but also the location of the acetylations on the protein had a significant effect on the retention. Matrix-assisted laser desorption ionization time-of-flight MS and MS/MS were used to confirm the chromatographic separation of isoforms. It was found that the acetylations site, especially on the N-terminus, has an effect on the retention on the PS-DVB column.     

Quantitative multiresidue method for about 100 veterinary drugs in different meat matrices by sub 2-microm particulate high-performance liquid chromatography coupled to time of flight mass spectrometry

A quantitative multiresidue method covering more than 100 veterinary drugs, belonging to different drug families, has been developed. The proposed approach uses an liquid-liquid-solid extraction technique (bi-polarity extraction) which is capable in recovering polar, medium polar and apolar compounds. A thorough generic reversed phase solid-phase extraction (SPE) clean-up removes interfering proteins and provides clean and stable extracts. Dedicated rinsing steps are proposed to reduce analyte adsorption on glass walls and on precipitating proteins. The resulting extract is analyzed by ultra-performance liquid chromatography (UPLC) coupled to time of flight mass spectrometry (TOF). The method was validated according to the Commission Decision 2002/657/EEC. Validation coved the relevant meat matrices (muscle, kidney and liver).     

Concentrating colloids with electric field gradients. II. Phase transitions and crystal buckling of long-ranged repulsive charged spheres in an electric bottle

We explored the usefulness of electric field gradients for the manipulation of the particle concentration in suspensions of charged colloids, which have long-ranged repulsive interactions. In particular, we studied the compression obtained by "negative" dielectrophoresis, which drives the particles to the regions of lowest field strength, thus preventing unwanted structural changes by induced dipole-dipole interactions. We used several sample cell layouts and suspension compositions, with a different range of the interparticle repulsions. For these systems, we obtained sufficient compression to observe a transition from the initial fluid phase to a random hexagonal close-packed crystal, as well as a body-centered cubic crystal. The heterogeneous dielectrophoretic crystallization mechanism involved an intriguing "pluglike" motion of the crystal, similar to what we have previously reported for hard-sphere suspensions. In this way, remarkably large single crystals were formed of several millimeters wide and a couple of centimeters long. Moreover, we found that these crystals could be compressed to such an extent that it led to an anisotropic deformation ("buckling") and, upon subsequent relaxation, a reorientation of the lattice, while stacking errors disappeared. These striking differences with the compressed hard-sphere crystals that we studied before [M. E. Leunissen et al., J. Chem. Phys. 128, 164508 (2008).] are likely due to the smaller elastic moduli of the present lower-density soft-sphere crystals.     

Concentrating colloids with electric field gradients. I. Particle transport and growth mechanism of hard-sphere-like crystals in an electric bottle

This work concerns the use of electric field gradients to manipulate the local particle concentration in a hard-sphere-like suspension. Inside a specially designed "electric bottle," we observed our colloids to collect in the regions of lowest field strength ("negative dielectrophoresis"). This allows for the use of larger field gradients and stronger dielectrophoretic forces than in the original electric bottle design, which was based on positive dielectrophoresis [M. T. Sullivan et al., Phys. Rev. Lett. 96, 015703 (2006)]. We used confocal scanning laser microscopy to quantitatively follow the time-dependent change in the particle density and the suspension structure. Within a few days, the dielectrophoretic compression was seen to initiate a heterogeneouslike growth of large single crystals, which took place far out-of-equilibrium. The crystals had a random hexagonal close-packed structure and displayed an intriguing growth mechanism, during which the entire crystal was continuously transported, while growing both on the "high-field" and the "low-field" sides, although at different rates. After switching off the electric field, the compressed crystals were found to relax to a lower packing fraction and melt, at a much slower rate than the crystal growth. Besides revealing the particular (far out-of-equilibrium) crystal growth mechanism in these electric bottles, our observations also shed light on the role of the different particle transport processes in the cell and some of the relevant tuning parameters. This is useful for different types of experiments, for instance, focusing more on melting, homogeneous crystallization, or the glass transition.     

Looking at self-consistent-charge density functional tight binding from a semiempirical perspective

The self-consistent-charge density functional tight binding (SCC-DFTB) method is compared with other semiempirical methods (MNDO, AM1, PM3, OM1, OM2, OM3). Despite the differences in the underlying philosophy and derivation, these methods share many common features. Systematic evaluations of their performance are reported for standard test sets that are in common use. The overall accuracy of SCC-DFTB and the other methods is in the same range, with the overall tendency AM1相似文献   

Morphological predictability and acoustic duration of interfixes in Dutch compounds

This study explores the effects of informational redundancy, as carried by a word's morphological paradigmatic structure, on acoustic duration in read aloud speech. The hypothesis that the more predictable a linguistic unit is, the less salient its realization, was tested on the basis of the acoustic duration of interfixes in Dutch compounds in two datasets: One for the interfix -s- (1155 tokens) and one for the interfix -e(n)- (742 tokens). Both datasets show that the more probable the interfix is, given the compound and its constituents, the longer it is realized. These findings run counter to the predictions of information-theoretical approaches and can be resolved by the Paradigmatic Signal Enhancement Hypothesis. This hypothesis argues that whenever selection of an element from alternatives is probabilistic, the element's duration is predicted by the amount of paradigmatic support for the element: The most likely alternative in the paradigm of selection is realized longer.     

Microscopic and Molecular Insights into Heterogeneous Phase Degradation of Agars and Carrageenans by Marine Bacterial Galactanases

Agars and carrageenans are sulfated galactans and are the main matrix component of the cell wall of red algae. They form gels made of a 3D network of fibres built by the aggregation of polysaccharide double-helices. Agarases and carrageenase are enzymes produced by marine bacteria involved in the conversion of algal biomass. We have analyzed the structures and the modes of action of these enzymes adapted to the degradation of anionic polysaccharides in heterogeneous phase. We found that κ- and ι-carrageenases proceed via an endo-processive mode of action as it was already described for other enzymes active on neutral polysaccharides (cellulose, starch).