Weighted finite energy sum rules for the omega meson in nuclear matter

The possible in-medium changes of the properties of an omega meson placed in cold nuclear matter are constrained by QCD sum rules. It is shown that the sum rules cannot fully determine the in-medium spectral shape of the omega meson. However, for a given parameterization the sum rules can constrain or correlate the hadronic parameters. It is shown that weighted finite energy sum rules provide a proper framework to study directly these constraints/correlations. Two typical parameterizations of possible in-medium omega spectra are analyzed, namely (i) a one-peak structure with arbitrary position and width of the peak and (ii) a structure with two (narrow) peaks, caused by the genuine omega meson and a resonance-hole branch. The sum rules provide for case (i) a mass-width correlation and for case (ii) a correlation between the peak heights and the peak position of the omega branch. It is also analyzed how the obtained results depend on the size of the relevant four-quark operator evaluated with respect to a nucleon. Finally it is argued that a strict vector meson dominance scenario is not compatible with the sum rules.Comment: 14 page

Rho meson properties from combining QCD-based models

Aiming at the calculation of the properties of rho-mesons, non-perturbative QCD-based methods are discussed concerning their potentials as well as their short-comings. The latter are overcome by combining these techniques. The utilized methods are (i) the chiral constituent quark model deduced from the instanton vacuum model and large-N_c arguments, (ii) chiral perturbation theory unitarized by the inverse amplitude method and (iii) QCD sum rules. Advantages of the combination of these methods are especially the absence of un-physical quark-production thresholds and parameter-free results. Already in the chiral limit and in leading order in 1/N_c one obtains a reasonable result for the mass of the rho-meson, namely m_rho = 790 \pm 30 MeV. Using the KSFR relation the universality of the rho-meson coupling is recovered. The latter is found to be g = 6.0 \pm 0.3.Comment: 16 pages, 1 figure, Revtex

QCD sum rules at finite density in the large-N_c limit: The coupling of the rho-nucleon system to the D_{13}(1520)

QCD sum rules are studied for the vector-isovector current at finite baryon density in the limit of large number of colors N_c. For the condensate side it is shown that in this limit the four-quark condensate factorizes also for the finite density case. At the hadronic side the medium dependence is expressed in terms of the current-nucleon forward scattering amplitude. Generalizing vector meson dominance we allow for a direct coupling of the current to the nucleon as well as a coupling via the rho meson. We discuss the N_c dependence of (a) modifications of the pion cloud of the rho meson, (b) mixing with other mesons (in particular a_1 and omega) and (c) resonance-hole excitations R N^{-1}. We show that only the last effect survives in the large-N_c limit. Saturating the sum rules with a simple hadronic ansatz which allows for the excitation of the D_{13}(1520) we determine the coupling of the latter to the rho-nucleon and the photon-nucleon system. These couplings are hard to determine from vacuum physics alone.Comment: 13 pages, 2 figure

Upstream microbial process characterization with single-use bioreactors from 15 mL to 50L

Developing biological and industrial molecules derived from microbial fermentation relies upon performant bioreactors to allow a rapid scale up to commercial batches. For this it is relevant to minimize any possible risks while developing a process that fits the industry quality standards. The choice of a well characterized system plays an important role from R&D through to production stages. The aim of this poster is to provide evidence to demonstrate the benefits of a microbial process developed using single-use, high throughput, and scalable upstream solutions. The method chosen to showcase this consistency is based on the DECHEMA Guidelines for Engineering Characterization principles and with the Zurich University of Applied Sciences, ZHAW. DECHEMA guidelines include a set of standard conditions for bioreactor characterization. By using process development and pilot scale bioreactors like the ambr 15f, ambr 250, and BIOSTAT STR 50, it is possible to accelerate development timelines and ensure process success

QCD sum rule analysis for light vector and axial-vector mesons in vacuum and nuclear matter

Extending previous work we study the constraints of QCD sum rules on mass and width of light vector and axial-vector mesons in vacuum and in a medium with finite nuclear density. For the latter case especially the effect of nuclear pions leading to vector-axial-vector mixing is included in the analysis.Comment: RevTeX, 32 pages, 10 eps figure

Regulation of 3′ splice site selection after step 1 of splicing by spliceosomal C* proteins

Alternative precursor messenger RNA splicing is instrumental in expanding the proteome of higher eukaryotes, and changes in 3′ splice site (3'ss) usage contribute to human disease. We demonstrate by small interfering RNA–mediated knockdowns, followed by RNA sequencing, that many proteins first recruited to human C* spliceosomes, which catalyze step 2 of splicing, regulate alternative splicing, including the selection of alternatively spliced NAGNAG 3′ss. Cryo–electron microscopy and protein cross-linking reveal the molecular architecture of these proteins in C* spliceosomes, providing mechanistic and structural insights into how they influence 3'ss usage. They further elucidate the path of the 3′ region of the intron, allowing a structure-based model for how the C* spliceosome potentially scans for the proximal 3′ss. By combining biochemical and structural approaches with genome-wide functional analyses, our studies reveal widespread regulation of alternative 3′ss usage after step 1 of splicing and the likely mechanisms whereby C* proteins influence NAGNAG 3′ss choices

Operator Product Expansion and Quark-Hadron Duality: Facts and Riddles

We review the status of the practical operator product expansion (OPE), when applied to two-point correlators of QCD currents which interpolate to mesonic resonances, in view of the violations of local quark-hadron duality. Covered topics are: a mini-review of mesonic QCD sum rules in vacuum, at finite temperature, or at finite baryon density, a comparison of model calculations of current-current correlation functions in 2D and 4D with the OPE expression, a discussion of meson distribution amplitudes in the light of nonperturbatively nonlocal modifications of the OPE, and a reorganization of the OPE which (partially) resums powers of covariant derivatives.Comment: now 68 pages, 29 figures (1 figure added), habilitation thesis, mild restructuring, typos corrected, about 30 references and corresponding text added, version to be published in Prog. Part. Nucl. Phy

Photoproduction of mesons off nuclei

Recent results for the photoproduction of mesons off nuclei are reviewed. These experiments have been performed for two major lines of research related to the properties of the strong interaction. The investigation of nucleon resonances requires light nuclei as targets for the extraction of the isospin composition of the electromagnetic excitations. This is done with quasi-free meson photoproduction off the bound neutron and supplemented with the measurement of coherent photoproduction reactions, serving as spin and/or isospin filters. Furthermore, photoproduction from light and heavy nuclei is a very efficient tool for the study of the interactions of mesons with nuclear matter and the in-medium properties of hadrons. Experiments are currently rapidly developing due to the combination of high quality tagged (and polarized) photon beams with state-of-the-art 4pi detectors and polarized targets

Recommendation for biological evaluation of bioreactor performance for microbial processes

The Escherichia coli model process described in the recommendation also makes it possible to characterise the biological performance of a system. The standardised process aims to determine the performance of bioreactors, in particular, single-use bioreactors, and to evaluate their suitability for microbial applications. Since microbial processes place high demands on the bioreactor system with regard to oxygen transfer, this is of particular importance; another important parameter is heat removal. The associated Excel tool offers the possibility of a standardised evaluation so that a comparison across bioreactor systems is possible. Calculations, e.g. of the volumetric mass transfer coefficient, will be performed automatically after input of the raw data. Recommendation and Excel tool were developed by the "Single-Use Microbial" working group of DECHEMA's expert group "Single-Use Technology in Biopharmaceutical Manufacturing"