Dispersion relations for η′→ηππ\eta'\to\eta\pi\pi

We present a dispersive analysis of the decay amplitude for $\eta'\to\eta\pi\pi$ that is based on the fundamental principles of analyticity and unitarity. In this framework, final-state interactions are fully taken into account. Our dispersive representation relies only on input for the $\pi\pi$ and $\pi\eta$ scattering phase shifts. Isospin symmetry allows us to describe both the charged and neutral decay channel in terms of the same function. The dispersion relation contains subtraction constants that cannot be fixed by unitarity. We determine these parameters by a fit to Dalitz-plot data from the VES and BES-III experiments. We study the prediction of a low-energy theorem and compare the dispersive fit to variants of chiral perturbation theory.Comment: 22 pages, 10 figures; v2: added footnote, version published in EPJ

Towards a data-driven analysis of hadronic light-by-light scattering

The hadronic light-by-light contribution to the anomalous magnetic moment of the muon was recently analyzed in the framework of dispersion theory, providing a systematic formalism where all input quantities are expressed in terms of on-shell form factors and scattering amplitudes that are in principle accessible in experiment. We briefly review the main ideas behind this framework and discuss the various experimental ingredients needed for the evaluation of one- and two-pion intermediate states. In particular, we identify processes that in the absence of data for doubly-virtual pion-photon interactions can help constrain parameters in the dispersive reconstruction of the relevant input quantities, the pion transition form factor and the helicity partial waves for $\gamma^*\gamma^*\to\pi\pi$.Comment: 7 pages, 4 figures, 2 tables, journal versio

Nucleon matrix elements of the antisymmetric quark tensor

If physics beyond the Standard Model enters well above the electroweak scale, its low-energy effects are described by Standard Model Effective Field Theory. Already at dimension six many operators involve the antisymmetric quark tensor $\bar q \sigma^{\mu\nu} q$, whose matrix elements are difficult to constrain from experiment, Ward identities, or low-energy theorems, in contrast to the corresponding vector and axial-vector or even scalar and pseudoscalar currents. However, with normalizations determined from lattice QCD, analyticity and unitarity often allow one to predict the momentum dependence in a large kinematic range. Starting from recent results in the meson sector, we extend this method to the nucleon case and, in combination with pole dominance, provide a comprehensive assessment of the current status of the nucleon form factors of the quark tensor.Comment: 7 pages, 3 figures; strangeness input update

Isospin-breaking effects in the two-pion contribution to hadronic vacuum polarization

Isospin-breaking (IB) effects in the two-pion contribution to hadronic vacuum polarization (HVP) can be resonantly enhanced, if related to the interference of the ρ(770) and ω(782) resonances. This particular IB contribution to the pion vector form factor and thus the line shape in e$^{+}$e$^{−}$→ π$^{+}$π$^{−}$ can be described by the residue at the ω pole — the ρ-ω mixing parameter ϵ$_{ω}$. Here, we argue that while in general analyticity requires this parameter to be real, the radiative channels π$^{0}$γ, ππγ, ηγ can induce a small phase, whose size we estimate as δ$_{ϵ}$ = 3.5(1.0)° by using a narrow-width approximation for the intermediate-state vector mesons. We then perform fits to the e$^{+}$e$^{−}$→ π$^{+}$π$^{−}$ data base and study the consequences for the two-pion HVP contribution to the anomalous magnetic moment of the muon, its IB part due to ρ-ω mixing, and the mass of the ω resonance. We find that the global fit does prefer a non-vanishing value of δ$_{ϵ}$ = 4.5(1.2)°, close to the narrow-resonance expectation, but with a large spread among the data sets, indicating systematic differences in the ρ-ω region

Accumulation and nuclear import of HIF1 alpha during high and low oxygen concentration in skeletal muscle cells in primary culture

AbstractThe hypoxia-inducible-factor-1 (HIF1) mediates the transcriptional upregulation of several target genes during hypoxia. HIF1 itself is known to be regulated essentially by ubiquitinylation and proteolytic degradation of the subunit HIF1α of the dimeric transcription factor HIF1. In contrast to other tissues, skeletal muscle expresses high amounts of HIF1α in normoxia as well as in hypoxia. In view of this, we aimed to investigate HIF1α accumulation and subcellular localization as well as the transcriptional activity of the HIF1α-regulated gene of glyceraldehyde dehydrogenase (GAPDH) in skeletal muscle cells exposed to low oxygen concentration (3% O2), normoxia (20% O2) or high oxygen concentration (42% O2). Immunofluorescence analysis reveals that under normoxic and high oxygen conditions, significant amounts of HIF1α can be found exclusively in the cytoplasm of the myotubes. Muscle cells treated with CoCl2, a known inhibitor of HIF1α degradation, show even higher levels of HIF1α, again exclusively in the cytoplasm. Under conditions of low oxygen, HIF1α in controls as well as in CoCl2-treated cells is found in the nuclei. CdCl2 inhibits nuclear import of HIF1α at low oxygen concentration and leads to a transcriptional downregulation of the marker enzyme of anaerobic glycolysis GAPDH. Immunoprecipitation with anti-HIF1α antibody co-precipitates HSP90 in an oxygen-dependent manner, more at high pO2 than at low pO2. Cadmium-treated samples also show high amounts of co-immunoprecipitated HSP90, independent of oxygen concentration. We conclude that in skeletal muscle cells, HIF1α, in contrast to other tissues, may, in addition to its regulation by degradation, also be regulated by binding to HSP90 and subsequent inhibition of its import into the nuclei

Heterogeneous effects of eccentric training and nordic hamstring exercise on the biceps femoris fascicle length based on ultrasound assessment and extrapolation methods: A systematic review of randomised controlled trials with meta-analyses

Objective To systematically review the effects of eccentric training based on biceps femoris fascicle length using ultrasound assessment and extrapolation methods. Design Systematic review and meta-analysis of randomised controlled trials. Data sources CENTRAL, CINAHL Plus with full text, PubMed and OpenGrey databases were searched on 6 July 2021. Eligibility criteria for selecting studies Randomised controlled trials (RCTs) lasting at least four weeks and presenting data about biceps femoris (BF) fascicle length (FL) as an outcome. Method Searching databases, screening studies, performing risk of bias assessments and determining the level of evidence (LoE) for each meta-analysis were applied during the study. PRISMA 2020 statement and Cochrane Handbook for Systematic Reviews of Interventions were used as the guidelines of this systematic review. Results Eight randomised controlled trials included in meta-analyses. Based on the very low and low LoE, eccentric training has small (g = 0.29, 95% CI [-0.26, 0.85]), moderate (g = 0.72, 95% CI [0.17, 1.28]) and large (g = 2.20, 95% CI [0.99, 3.41]) effect sizes (ES) based on manual linear extrapolation (MLE), panoramic ultrasound scanning and trigonometric equation methods, respectively. Similarly, Nordic hamstring exercise (NHE) has small (g = 0.23 [-1.02, 1.47]), small (g = 0.38, 95% CI [-0.50, 1.27]) and large (g = 1.98, 95% CI [0.52, 3.44]) ES based on the MLE, panoramic ultrasound scanning and trigonometric equation methods, respectively. Conclusion ES of eccentric training, including NHE, vary between the MLE, panoramic ultrasound scanning, and equation methods. The relevant scientific community should have a consensus on measurement standards of the BF FL measurements. Further studies can be conducted to compare the effects of eccentric training based on the ultrasound assessment and extrapolation methods

The Effects of Resistance Training on Architecture and Volume of the Upper Extremity Muscles: A Systematic Review of Randomised Controlled Trials and Meta-Analyses

To systematically review the effects of exercise on fascicle geometry and muscle size parameters of the upper extremity muscles, the CENTRAL, CINAHL, PubMed and OpenGrey databases were searched on 31 July 2021. Finally, 17 randomised controlled trials (RCTs) were included in this systematic review. High-intensity bench press training (g = 1.03) and 12 RM bench press exercises (g = 1.21) showed a large effect size on increasing pectoralis major muscle size. In the elbow extensors, large effects were reported for an increase in muscle size with isometric maximal voluntary co-contraction training (g = 1.97), lying triceps extension exercise (g = 1.25), and nonlinear periodised resistance training (g = 2.07). In addition, further large effects were achieved in the elbow flexors via traditional elbow flexion exercises (g = 0.93), concentric low-load forearm flexion-extension training (g = 0.94, g = 1), isometric maximal voluntary co-contraction training (g = 1.01), concentric low-load forearm flexion-extension training with blood flow restriction (g = 1.02, g = 1.07), and nonlinear periodised resistance training (g = 1.13, g = 1.34). Regarding the forearm muscles, isometric ulnar deviation training showed a large effect (g = 2.22) on increasing the flexor carpi ulnaris and radialis muscle size. Results show that these training modalities are suitable for gaining hypertrophy in the relevant muscles with at least four weeks of training duration. Future RCTs should investigate the effects of exercise modalities on the triceps brachii fascicle geometry, the infraspinatus muscle thickness (MT) and the subscapular MT due to their associations with sports performance