Measurement of W-pair production in e+e−e^+ e^- collisions at 189 GeV

The production of W-pairs is analysed in a data samplecollected by ALEPH at a mean centre-of-mass energy of 188.6 GeV,corresponding to an integrated luminosity of 174.2 pb^-1. Crosssections are given for different topologies of W decays intoleptons or hadrons. Combining all final states and assumingStandard Model branching fractions, the total W-pair cross sectionis measured to be 15.71 +- 0.34 (stat) +- 0.18 (syst) pb.Using also the W-pair data samples collected by ALEPH at lowercentre-of-mass energies, the decay branching fraction of the W bosoninto hadrons is measured to be BR (W hadrons) = 66.97+- 0.65 (stat) +- 0.32 (syst) %, allowing a determination of theCKM matrix element |V(cs)|= 0.951 +- 0.030 (stat) +- 0.015 (syst)

Searches for neutral Higgs bosons in e+e−e^{+}e^{-} collisions at centre-of-mass energies from 192 to 202 GeV

Searches for neutral Higgs bosons are performed with the 237 pb^-1 of data collected in 1999 by the ALEPH detector at LEP, for centre-of-mass energies between 191.6 and 201.6 GeV. These searches apply to Higgs bosons within the context of the Standard Model and its minimal supersymmetric extension (MSSM) as well as to invisibly decaying Higgs bosons. No evidence of a signal is seen. A lower limit on the mass of the Standard Model Higgs boson of 107.7 GeV/c^2 at 95% confidence level is set. In the MSSM, lower limits of 91.2 and 91.6 GeV/c^2 are derived for the masses of the neutral Higgs bosons h and A, respectively. For a Higgs boson decaying invisibly and produced with the Standard Model cross section, masses below 106.4 GeV/c^2 are excluded

Determination of sin2 θeff w using jet charge measurements in hadronic Z decays

The electroweak mixing angle is determined with high precision from measurements of the mean difference between forward and backward hemisphere charges in hadronic decays of the Z. A data sample of 2.5 million hadronic Z decays recorded over the period 1990 to 1994 in the ALEPH detector at LEP is used. The mean charge separation between event hemispheres containing the original quark and antiquark is measured for bb̄ and cc̄ events in subsamples selected by their long lifetimes or using fast D*'s. The corresponding average charge separation for light quarks is measured in an inclusive sample from the anticorrelation between charges of opposite hemispheres and agrees with predictions of hadronisation models with a precision of 2%. It is shown that differences between light quark charge separations and the measured average can be determined using hadronisation models, with systematic uncertainties constrained by measurements of inclusive production of kaons, protons and A's. The separations are used to measure the electroweak mixing angle precisely as sin2 θeff w = 0.2322 ± 0.0008(exp. stat.) ±0.0007(exp. syst.) ± 0.0008(sep.). The first two errors are due to purely experimental sources whereas the third stems from uncertainties in the quark charge separations

CCMV-based enzymatic nanoreactors

Protein-based nanoreactors are generated by encapsulating an enzyme inside the capsid of the cowpea chlorotic mottle virus (CCMV). Here, three different noncovalent methods are described to efficiently incorporate enzymes inside the capsid of these viral protein cages. The methods are based on pH, leucine zippers, and electrostatic interactions respectively, as a driving force for encapsulation. The methods are exclusively described for the enzymes horseradish peroxidase, glucose oxidase, and Pseudozyma antarctica lipase B, but they are also applicable for other enzymes

Disassembling peptide-based fibres by switching the hydrophobic-hydrophilic balance

\u3cp\u3eAmyloid-like model peptides, modified on the N-terminus with an alkyl tail and on the C-terminus with a PEG chain, yielded fibres that were susceptible to triggered disassembly by removal of the alkyl chain, which affected the hydrophobic-hydrophilic balance.\u3c/p\u3

Recombinant expression and purification of 'virus-like' bacterial encapsulin protein cages

Ultracentrifugation, particularly the use of sucrose or cesium chloride density gradients, is a highly reliable and efficient technique for the purification of virus-like particles and protein cages. Since virus-like particles and protein cages have a unique size compared to cellular macromolecules and organelles, the rate of migration can be used as a tool for purification. Here we describe a detailed protocol for the purification of recently discovered virus-like assemblies called bacterial encapsulins from Thermotoga maritima and Brevibacterium linens

Geometric curvature controls the chemical patchiness and self-assembly of nanoparticles

When organic molecules are tethered onto non-spherical nanoparticles, their chemical properties depend on the particles' local curvature and shape. Based on this observation, we show here that it is possible to engineer chemical patchiness across the surface of a non-spherical nanoparticle using a single chemical species. In particular, when acidic ligands are used, regions of the particle surface with different curvature become charged at different pH values of the surrounding solution. This interplay between particle shape and local electrostatics allows for fine control over nanoscale self-assembly leading to structures with varying degrees of complexity. These structures range from particle cross-stacks to open-lattice crystals, the latter with pore sizes on the order of tens of nanometres, that is, at the lower synthetic limits of metallic mesoporous materials