Lattice QCD calculation of hadronic light-by-light scattering

We perform a lattice QCD calculation of the hadronic light-by-light scattering amplitude in a broad kinematical range. At forward kinematics, the results are compared to a phenomenological analysis based on dispersive sum rules for light-by-light scattering. The size of the pion pole contribution is investigated for momenta of typical hadronic size. The presented numerical methods can be used to compute the hadronic light-by-light contribution to the anomalous magnetic moment of the muon. Our calculations are carried out in two-flavor QCD with the pion mass in the range of 270 to 450MeV, and contain so far only the diagrams with fully connected quark lines.Comment: 5 pages, 5 figure

Light-by-light forward scattering amplitudes in Lattice QCD

We present our preliminary results on the calculation of hadronic light-by-light forward scattering amplitudes using vector four-point correlation functions computed on the lattice. Using a dispersive approach, forward scattering amplitudes can be described by $\gamma^* \gamma^* \to$ hadrons fusion cross sections and then compared with phenomenology. We show that only a few states are needed to reproduce our data. In particular, the sum rules considered in this study imply relations between meson$-\gamma\gamma$ couplings and provide valuable information about individual form factors which are often used to estimate the meson-pole contributions to the hadronic light-by-light contribution to the $(g-2)$ of the muon.Comment: Proceedings of the 35th International Symposium on Lattice Field Theory (Lattice 2017), Granada, Spain. 8 pages, 15 figure

Complement activation and protein adsorption by carbon nanotubes

As a first step to validate the use of carbon nanotubes as novel vaccine or drug delivery devices, their interaction with a part of the human immune system, complement, has been explored. Haemolytic assays were conducted to investigate the activation of the human serum complement system via the classical and alternative pathways. Western blot and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) techniques were used to elucidate the mechanism of activation of complement via the classical pathway, and to analyse the interaction of complement and other plasma proteins with carbon nanotubes. We report for the first time that carbon nanotubes activate human complement via both classical and alternative pathways. We conclude that complement activation by nanotubes is consistent with reported adjuvant effects, and might also in various circumstances promote damaging effects of excessive complement activation, such as inflammation and granuloma formation. C1q binds directly to carbon nanotubes. Protein binding to carbon nanotubes is highly selective, since out of the many different proteins in plasma, very few bind to the carbon nanotubes. Fibrinogen and apolipoproteins (AI, AIV and CIII) were the proteins that bound to carbon nanotubes in greatest quantit

Mapping cellular processes in the mesenchyme during palatal development in the absence of Tbx1 reveals complex proliferation changes and perturbed cell packing and polarity

The 22q11 deletion syndromes represent a spectrum of overlapping conditions including cardiac defects and craniofacial malformations. Amongst the craniofacial anomalies that are seen, cleft of the secondary palate is a common feature. Haploinsufficiency of TBX1 is believed to be a major contributor toward many of the developmental structural anomalies that occur in these syndromes, and targeted deletion of Tbx1 in the mouse reproduces many of these malformations, including cleft palate. However, the cellular basis of this defect is only poorly understood. Here, palatal development in the absence of Tbx1 has been analysed, focusing on cellular properties within the whole mesenchymal volume of the palatal shelves. Novel image analyses and data presentation tools were applied to quantify cell proliferation rates, including regions of elevated as well as reduced proliferation, and cell packing in the mesenchyme. Also, cell orientations (nucleus–Golgi axis) were mapped as a potential marker of directional cell movement. Proliferation differed only subtly between wild‐type and mutant until embryonic day (E)15.5 when proliferation in the mutant was significantly lower. Tbx1 (−/−) palatal shelves had slightly different cell packing than wild‐type, somewhat lower before elevation and higher at E15.5 when the wild‐type palate has elevated and fused. Cell orientation is biased towards the shelf distal edge in the mid‐palate of wild‐type embryos but is essentially random in the Tbx1 (−/−) mutant shelves, suggesting that polarised processes such as directed cell rearrangement might be causal for the cleft phenotype. The implications of these findings in the context of further understanding Tbx1 function during palatogenesis and of these methods for the more general analysis of genotype–phenotype functional relationships are discussed

The charm-quark contribution to light-by-light scattering in the muon (g−2)(g-2) from lattice QCD

We compute the hadronic light-by-light scattering contribution to the muon $g-2$ from the charm quark using lattice QCD. The calculation is performed on ensembles generated with dynamical $(u,d,s)$ quarks at the SU(3)$_{\rm f}$ symmetric point with degenerate pion and kaon masses of around 415 MeV. It includes the connected charm contribution, as well as the leading disconnected Wick contraction, involving the correlation between a charm and a light-quark loop. Cutoff effects turn out to be sizeable, which leads us to use lighter-than-physical charm masses, to employ a broad range of lattice spacings reaching down to 0.039 fm and to perform a combined charm-mass and continuum extrapolation. We use the $\eta_c$ meson to define the physical charm-mass point and obtain a final value of $a_\mu^{\rm HLbL,c} = (2.8\pm 0.5) \times 10^{-11}$, whose uncertainty is dominated by the systematics of the extrapolation. Our result is consistent with the estimate based on a simple charm-quark loop, whilst being free of any perturbative scheme dependence on the charm mass. The mixed charm-light disconnected contraction contributes a small negative amount to the final value.Comment: 21 pages, 8 figures, 9 table

Hadronic light-by-light contribution to (g−2)μ(g-2)_\mu from lattice QCD with SU(3) flavor symmetry

We perform a lattice QCD calculation of the hadronic light-by-light contribution to $(g-2)_\mu$ at the SU(3) flavor-symmetric point $m_\pi=m_K\simeq 420\,$MeV. The representation used is based on coordinate-space perturbation theory, with all QED elements of the relevant Feynman diagrams implemented in continuum, infinite Euclidean space. As a consequence, the effect of using finite lattices to evaluate the QCD four-point function of the electromagnetic current is exponentially suppressed. Thanks to the SU(3)-flavor symmetry, only two topologies of diagrams contribute, the fully connected and the leading disconnected. We show the equivalence in the continuum limit of two methods of computing the connected contribution, and introduce a sparse-grid technique for computing the disconnected contribution. Thanks to our previous calculation of the pion transition form factor, we are able to correct for the residual finite-size effects and extend the tail of the integrand. We test our understanding of finite-size effects by using gauge ensembles differing only by their volume. After a continuum extrapolation based on four lattice spacings, we obtain $a_\mu^{\rm hlbl} = (65.4\pm 4.9 \pm 6.6)\times 10^{-11}$, where the first error results from the uncertainties on the individual gauge ensembles and the second is the systematic error of the continuum extrapolation. Finally, we estimate how this value will change as the light-quark masses are lowered to their physical values.Comment: 19 figures, 39 pages; improved references, in particular concerning the eta exchange; no figures or results change

The perception of lip aesthetics in the context of facial proportions—An eye-tracking-based analysis

Background: Minimally invasive lip volumizing and contouring soft tissue filler procedures are frequently requested by both female and male aesthetic patients. Guidance on how to achieve the most beautiful outcome is inconsistent. Objective: To investigate what the most beautiful proportions are in relation to vermillion thickness, the distance of the upper and lower lip in relation to nose and chin, and relation to the bigonial distance. Methods: This study included a total of n = 101 volunteers (52 females, 49 males, 100% Caucasian) who inspected frontal images of modified facial proportions and answered a related questionnaire showcasing the same images. Image presentation followed a randomized sequence both for the eye tracking and for the survey component of this study but was equal for all observers. Results: The most attractive vertical position of lips was the 1:2 ratio in which the distance between lips and chin is double the length as the distance between lips and nose. For the ratio between the width of the lips and the bigonial distance, it was the 1:2.5 ratio, whereas for the thickness of the upper lip vermilion in relation to the upper lip ergotrid it was the 1:3/1:2 (male/female) ratio and for the lower lip vermilion and lower lip ergotrid it was the 1:4 ratio for both genders. Conclusion: The results of this eye tracking and survey-based investigation revealed that instead of one single universal ratio, multiple facial proportions exist that are perceived as most attractive/masculine/feminine. Regarding the perception of facial aesthetics, it appears there is a distinction between attractiveness and masculinity/femininity: the most attractive male/female face is not necessarily the most masculine or feminine.</p

The perception of lip aesthetics in the context of facial proportions—An eye-tracking-based analysis

Background: Minimally invasive lip volumizing and contouring soft tissue filler procedures are frequently requested by both female and male aesthetic patients. Guidance on how to achieve the most beautiful outcome is inconsistent. Objective: To investigate what the most beautiful proportions are in relation to vermillion thickness, the distance of the upper and lower lip in relation to nose and chin, and relation to the bigonial distance. Methods: This study included a total of n = 101 volunteers (52 females, 49 males, 100% Caucasian) who inspected frontal images of modified facial proportions and answered a related questionnaire showcasing the same images. Image presentation followed a randomized sequence both for the eye tracking and for the survey component of this study but was equal for all observers. Results: The most attractive vertical position of lips was the 1:2 ratio in which the distance between lips and chin is double the length as the distance between lips and nose. For the ratio between the width of the lips and the bigonial distance, it was the 1:2.5 ratio, whereas for the thickness of the upper lip vermilion in relation to the upper lip ergotrid it was the 1:3/1:2 (male/female) ratio and for the lower lip vermilion and lower lip ergotrid it was the 1:4 ratio for both genders. Conclusion: The results of this eye tracking and survey-based investigation revealed that instead of one single universal ratio, multiple facial proportions exist that are perceived as most attractive/masculine/feminine. Regarding the perception of facial aesthetics, it appears there is a distinction between attractiveness and masculinity/femininity: the most attractive male/female face is not necessarily the most masculine or feminine.</p

X-ray crystallographic structure of a complex between a synthetic protease of human immunodeficiency virus 1 and a substrate-based hydroxyethylamine inhibitor

The structure of a crystal complex of the chemically synthesized protease of human immunodeficiency virus 1 with a heptapeptide-derived inhibitor bound in the active site has been determined. The sequence of the inhibitor JG-365 is Ac-Ser-Leu-Asn-Phe-ψ[CH(OH)CH_2N]-Pro-Ile-Val-OMe; the K_i is 0.24 nM. The hydroxyethylamine moiety, in place of the normal scissile bond of the substrate, is believed to mimic a tetrahedral reaction intermediate. The structure of the complex has been refined to an R factor of 0.146 at 2.4-Å resolution by using restrained least squares with rms deviations in bond lengths of 0.02 Å and bond angles of 4. The bound inhibitor diastereomer has the S configuration at the hydroxyethylamine chiral carbon, and the hydroxyl group is positioned between the active site aspartate carboxyl groups within hydrogen bonding distance. Comparison of this structure with a reduced peptide bond inhibitor-protease complex indicates that these contacts confer the exceptional binding strength of JG-365