163 research outputs found
Capillary electrophoretic separation of herbicidal enantiomers applying ergot alkaloids
Abstract The capillary electrophoretic separation of some herbicidal enantiomers is shown applying 1-allylterguride as chiral selector. Baseline separation is shown for the enantiomers of fluazifop, halossifop and fenoxaprop, whereas the optical isomers of flamprop could be partially resolved. Separation times are short compared to similar analyses, applying HPLC and a terguride chiral stationary phase. The degree of dissociation of the acidic analytes, as well as the amount of methanol present in the background electrolyte, are shown to have a major influence on enantioresolution, as expected form earlier studies. © 1997 Elsevier Science B. V
Off-Diagonal Elements of the DeWitt Expansion from the Quantum Mechanical Path Integral
The DeWitt expansion of the matrix element M_{xy} = \left\langle x \right|
\exp -[\case{1}{2} (p-A)^2 + V]t \left| y \right\rangle, in
powers of can be made in a number of ways. For (the case of interest
when doing one-loop calculations) numerous approaches have been employed to
determine this expansion to very high order; when (relevant for
doing calculations beyond one-loop) there appear to be but two examples of
performing the DeWitt expansion. In this paper we compute the off-diagonal
elements of the DeWitt expansion coefficients using the Fock-Schwinger gauge.
Our technique is based on representing by a quantum mechanical path
integral. We also generalize our method to the case of curved space, allowing
us to determine the DeWitt expansion of \tilde M_{xy} = \langle x| \exp
\case{1}{2} [\case{1}{\sqrt {g}} (\partial_\mu - i
A_\mu)g^{\mu\nu}{\sqrt{g}}(\partial_\nu - i A_\nu) ] t| y \rangle by use of
normal coordinates. By comparison with results for the DeWitt expansion of this
matrix element obtained by the iterative solution of the diffusion equation,
the relative merit of different approaches to the representation of as a quantum mechanical path integral can be assessed. Furthermore, the
exact dependence of on some geometric scalars can be
determined. In two appendices, we discuss boundary effects in the
one-dimensional quantum mechanical path integral, and the curved space
generalization of the Fock-Schwinger gauge.Comment: 16pp, REVTeX. One additional appendix concerning end-point effects
for finite proper-time intervals; inclusion of these effects seem to make our
results consistent with those from explicit heat-kernel method
Reply to Guy et al.: Support for a bottleneck in the 2011 Escherichia coli O104:H4 outbreak in Germany
In our paper (1), we analyzed isolates from the Escherichia coli O104:H4 outbreaks in Germany and France in May to July 2011. We concluded that, although the German outbreak was larger, the German isolates represent a clade within the greater diversity of the French outbreak. We proposed several hypotheses to explain these findings, including that the lineage leading to the German outbreak went through a narrow bottleneck that purged diversity.
Guy et al. (2) report the genomes of eight additional E. coli O104:H4 isolates sampled from the German outbreak. By focusing on the numbers of SNPs in their samples, they suggest that the German outbreak is more diverse than we reported and is similar to the French outbreak.
In fact, Guy et al.’s data (2) strongly support our conclusion that the German outbreak represents a clade within the diversity
Unconventional secretion of Acb1 is mediated by autophagosomes
Evidence is presented for an unconventional protein secretion pathway that is conserved from yeast to Dictyostelium discoideum in which Acb1 may be sequestered into autophagosomal vesicles, which then fuse (either directly or indirectly) with the plasma membrane (see also the companion paper from Manjithaya et al. in this issue)
Standard Model Theory for the FCC-ee Tera-Z stage
The future 100-km circular collider FCC at CERN is planned to operate in one
of its modes as an electron-positron FCC-ee machine. We give an overview
comparing the theoretical status to the experimental demands of one of four
foreseen FCC-ee operating stages, Z-boson resonance energy physics, called the
FCC-ee Tera-Z stage for short. The FCC-ee Tera-Z will deliver the highest
integrated luminosities as well as very small systematic errors for a study of
the Standard Model (SM) with unprecedented precision. In fact, the FCC-ee
Tera-Z will allow the study of at least one more perturbative order in quantum
field theory compared to the LEP/SLC precision. The real problem is that the
present precision of theoretical calculations of the various SM observables
does not match that of the anticipated experimental measurements. The
bottle-necks to overcoming this situation are identified. In particular, the
issues of precise QED unfolding and the correct calculation of SM
pseudo-observables are critically reviewed. In an Executive Summary, we specify
which basic theoretical calculations are needed to meet the strong experimental
expectations at the FCC-ee Tera-Z. Several methods, techniques and tools needed
for higher-order multi-loop calculations are presented. By inspection of the
Z-boson partial and total decay width analyses, it is argued that at the
beginning of operation of the FCC-ee Tera-Z, the theory predictions may be
tuned to be precise enough not to limit the physics interpretation of the
measurements. This statement is based on anticipated progress in analytical and
numerical calculations of multi-loop and multi-scale Feynman integrals and on
the completion of two-loop electroweak radiative corrections to the SM
pseudo-observables this year. However, the above statement is conditional as
the theoretical issues demand a very dedicated and focused investment by the
community.Comment: Published versio
Formation of Amyloid-Like Fibrils by Y-Box Binding Protein 1 (YB-1) Is Mediated by Its Cold Shock Domain and Modulated by Disordered Terminal Domains
YB-1, a multifunctional DNA- and RNA-binding nucleocytoplasmic protein, is involved in the majority of DNA- and mRNA-dependent events in the cell. It consists of three structurally different domains: its central cold shock domain has the structure of a β-barrel, while the flanking domains are predicted to be intrinsically disordered. Recently, we showed that YB-1 is capable of forming elongated fibrils under high ionic strength conditions. Here we report that it is the cold shock domain that is responsible for formation of YB-1 fibrils, while the terminal domains differentially modulate this process depending on salt conditions. We demonstrate that YB-1 fibrils have amyloid-like features, including affinity for specific dyes and a typical X-ray diffraction pattern, and that in contrast to most of amyloids, they disassemble under nearly physiological conditions
HE-LHC: The High-Energy Large Hadron Collider – Future Circular Collider Conceptual Design Report Volume 4
In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100 km tunnel infrastructure, as well as the physics opportunities of these two colliders, and a high-energy LHC, based on FCC-hh technology. This document constitutes the third volume of the FCC Conceptual Design Report, devoted to the hadron collider FCC-hh. It summarizes the FCC-hh physics discovery opportunities, presents the FCC-hh accelerator design, performance reach, and staged operation plan, discusses the underlying technologies, the civil engineering and technical infrastructure, and also sketches a possible implementation. Combining ingredients from the Large Hadron Collider (LHC), the high-luminosity LHC upgrade and adding novel technologies and approaches, the FCC-hh design aims at significantly extending the energy frontier to 100 TeV. Its unprecedented centre-of-mass collision energy will make the FCC-hh a unique instrument to explore physics beyond the Standard Model, offering great direct sensitivity to new physics and discoveries
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