Search for electroweak SUSY production at CMS

Using the data collected during Run I of LHC operation the CMS Collaboration performed multiple analyses searching for the direct electroweak production of supersymmetric particles in proton-proton collisions. Different decay modes of the gauginos and sleptons were considered, through intermediate vector bosons or Higgs bosons, or directly to leptons. A set of complementary searches were designed to target these different decays. None of these searches shows any indication for physics beyond the standard model.Comment: On behalf of the CMS Collaboration Presented at The Second Annual Conference on Large Hadron Collider Physics, Columbia University, New York, U.S.A, June 2-7, 201

Quantification of carboxyl groups in carbodiimide cross-linked collagen sponges

Glutaraldehyde (GA) fixation of bioprosthetic tissue is a well adapted technique, with commercial products on the market for almost 40 years. Amine groups present in tissue react with GA to form different types of cross-links. An estimation of the degree of cross-linking of the tissue can be obtained by measuring the concentration of residual amine groups, which is frequently carried out with the 2,4,6 trinitrobenzene sulphonic acid (TNBS) assay. Cross-linked tissue and collagen matrices are usually further characterized by determining their physical properties (such as the shrinkage temperature), biological properties (such as resistance to enzymatic degradation), and mechanical properties before in vivo evaluation takes place. In an effort to improve the properties of cross-linked tissue and collagen, alternative cross-linking methods have been developed. One of these methods is based on the use of water soluble carbodiimides (CDI). It is generally accepted that this cross-linking method leads only to the formation of amide linkages between tissue carboxyl and amine groups. Therefore, until recently the TNBS assay was also used to determine the degree of cross-linking of CDI cross-linked tissue and collagen. However, it cannot be excluded that after activation of carboxyl groups of tissue and collagen by CDI, these groups can react with other nucleophiles (like hydroxyl groups) present in the matrix. To obtain a better insight in the degree of cross-linking of CDI cross-linked matrices a reliable assay for quantification of residual carboxyl groups is required. Up to now such an assay was not available. In this study a new assay to determine residual carboxyl groups in CDI cross-linked collagen matrices is presented. Reconstituted dermal bovine collagen matrices (RDBC) were cross-linked with a water soluble CDI and N-hydroxysuccinimide (NHS) and residual carboxyl groups were labeled using 5-bromomethyl fluorescein. Subsequently, the fluorescent label was released by mild hydrolysis and quantified with capillary zone electrophoresis. A calibration curve relating the concentration of carboxyl groups with peak intensities was obtained using SephadexTM standards with known concentrations of carboxyl groups. The concentration of carboxyl groups in unprocessed RDBC as determined with this new technique was equal to the concentration of carboxyl groups measured by amino acid analysis. On the basis of the concentration of residual carboxyl groups determined for CDI/NHS cross-linked RDBC and RDBC, in which the amine groups were blocked with propionaldehyde before CDI/NHS cross-linking, it was concluded that activated carboxyl groups can also react with other groups (such as hydroxyl groups) present in the matrix. This implies that the crosslink density of RDBC matrices after treatment with CDI/NHS is higher than expected on the basis of amide bond formation only, as determined by the TNBS assay

Volume-coupling in isotachophoresis

A new device for isotachophoretic analyses is described in which pre-separation columns with different inner diameters can simply be exchanged (so-called volume-coupling). The most important advantages compared to conventional equipment having a uniform column diameter are: the low end-voltages needed, a ready optimization of analysis time for a particular problem and the possibility of applying terminators with very low effective mobility. The application of Araldite® allows the use of non-aqueous solvents

Training software for chiral separations in capillary electrophoresis

A previously published steady-state simulation program for CE was extended with a sub-menu for chiral interaction. The interaction was modelled with a hypothetical (neutral) selector with properties similar to cyclodextrins. A three-type chiral interaction model was implemented in such a way that it was valid for both anionic and cationic analytes. User-defined chiral variables in the model were: the concentration of this chiral selector, the complex formation constants (K) of both non-ionic and ionic analyte species, the relative K differences between the two optical isomers (also for both non-ionic and ionic species) and the mobility of the analyte–selector complex, relative to that of the fully dissociated free analyte. In addition the following non-chiral variables are added: the dependence of the bulk viscosity on the chiral selector concentration and the dependence of the mobilities on the viscosity. Chiral components in the data base are simulated as mixtures of optical isomers with variable enantiomeric concentration ratios. These chiral parameters, together with the original features of the program, provide a very flexible training tool for chiral separations in capillary electrophoresis. For example, determination of the optimum chiral selector concentration can be done in seconds, using the simulation software. Although the software is intended mainly for training purposes, in cases where sufficient details of existing chiral selector–analyte combinations are available, the program is also suitable for method development of chiral separations in CE