Enhancing the Laser Scanning Confocal Microscopic Visualization of Lucifer Yellow Filled Cells in Whole-Mounted Tissue

The laser scanning confocal microscope (LSCM) is an extremely useful tool that allows fluorescently labelled cells to be visualized in whole-mount preparations. This is particularly advantageous, for example, in studying the dendritic trees of neurons with respect to their environment. One of the most popular, and easiest, ways to visualize a cell is to inject it intracellularly with the fluorophore Lucifer Yellow (LY). However, the argon gas lasers of most LSCM\u27s are not well matched to the excitation spectrum of aqueous LY. When this largely inappropriate excitation is combined with standard filters, designed for fluorescein fluorescence rather than Lucifer Yellow, the resulting image is poor. We report that clearing LY-injected neurons in methyl salicylate and mounting them in Entellan, a non-aqueous medium of high refractive index, enhances their visualization on a Bio-Rad LSCM with standard fluorescein (FITC) filters to an unexpected degree. This technique also leads to a substantial reduction in photobleaching

Continuum limit of parton distribution functions from the pseudo-distribution approach on the lattice

Precise quantification of the structure of nucleons is one of the crucial aims of hadronic physics for the coming years. The expected progress related to ongoing and planned experiments should be accompanied by calculations of partonic distributions from lattice QCD. While key insights from the lattice are expected to come for distributions that are difficult to access experimentally, it is important that lattice QCD can reproduce the well-known unpolarized parton distribution functions (PDFs) with full control over systematic uncertainties. One of the novel methods for accessing the partonic $x$-dependence is the pseudo-distribution approach, which employs matrix elements of a spatially-extended nonlocal Wilson-line operator of length $z$. In this paper, we address the issue of discretization effects, related to the necessarily nonzero value of the lattice spacing $a$, which start at first order in $a$ as a result of the nonlocal operator. We use twisted mass fermions simulated at three values of the lattice spacing, at a pion mass of 370 MeV, and extract the continuum limit of isovector unpolarized PDFs. We also test, for the first time in the pseudo-distribution approach, the effects of the recently derived two-loop matching. Finally, we address the issue of the reliability of the extraction with respect to the maximal value of $z$.Comment: 31 pages, 20 figure

Continuum limit of parton distribution functions from the pseudo-distribution approach on the lattice

Precise exploration of the partonic structure of the nucleon is one of the most important aims of high-energy physics. In recent years, it has become possible to address this topic with first-principle lattice QCD investigations. In this talk, we focus on the so-called pseudo-distribution approach to determine the isovector unpolarized PDFs. In particular, we employ three lattice spacings to study discretization effects and extract the distributions in the continuum limit, at a pion mass of around 370 MeV. Also, for the first time with pseudo-PDFs, we explore effects of the 2-loop matching from pseudo- to light-cone distributions.Comment: 10 pages, 6 figures, proceedings of the 39th International Symposium on Lattice Field Theory LATTICE 2022, 8-13 August 2022, Bonn, German

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

A Chandra Study: Are Dwarf Carbon Stars Spun Up and Rejuvenated by Mass Transfer?

Carbon stars (with C/O> 1) were long assumed to all be giants, because only AGB stars dredge up significant carbon into their atmospheres. The case is nearly iron-clad now that the formerly mysterious dwarf carbon (dC) stars are actually far more common than C giants, and have accreted carbon-rich material from a former AGB companion, yielding a white dwarf and a dC star that has gained both significant mass and angular momentum. Some such dC systems have undergone a planetary nebula phase, and some may evolve to become CH, CEMP, or Ba giants. Recent studies indicate that most dCs are likely from older, metal-poor kinematic populations. Given the well-known anti-correlation of age and activity, dCs would not be expected to show significant X-ray emission related to coronal activity. However, accretion spin-up might be expected to rejuvenate magnetic dynamos in these post mass-transfer binary systems. We describe our Chandra pilot study of six dCs selected from the SDSS for Halpha emission and/or a hot white dwarf companion, to test whether their X-ray emission strength and spectral properties are consistent with a rejuvenated dynamo. We detect all 6 dCs in the sample, which have X-ray luminosities ranging from logLx= 28.5 - 29.7, preliminary evidence that dCs may be active at a level consistent with stars that have short rotation periods of several days or less. More definitive results require a sample of typical dCs with deeper X-ray observations to better constrain their plasma temperatures.Comment: 13 pages, 5 figures. Revised and resubmitted June 20, accepted June 21, 2019 to Ap

Clypeal patterning in the paper wasp Polistes dominulus: no evidence of adaptive value in the wild

Status signals function in a number of species to communicate competitive ability to conspecific rivals during competition for resources. In the paper wasp Polistes dominulus, variable black clypeal patterns are thought to be important in mediating competition among females. Results of previous behavioral experiments in the lab indicate that P. dominulus clypeal patterns provide information about an individual's competitive ability to rivals during agonistic interactions. To date, however, there has been no detailed examination of the adaptive value of clypeal patterns in the wild. To address this, we looked for correlations between clypeal patterning and various fitness measures, including reproductive success, hierarchical rank, and survival, in a large, free-living population of P. dominulus in southern Spain. Reproductive success over the nesting season was not correlated with clypeal patterning. Furthermore, there was no relationship between a female's clypeal patterning and the rank she achieved within the hierarchy or her survival during nest founding. Overall, we found no evidence that P. dominulus clypeal patterns are related to competitive ability or other aspects of quality in our population. This result is consistent with geographical variation in the adaptive value of clypeal patterns between P. dominulus populations; however, data on the relationship between patterning and fitness from other populations are required to test this hypothesi

Clypeal patterning in the paper wasp Polistes dominulus: no evidence of adaptive value in the wild

Status signals function in a number of species to communicate competitive ability to conspecific rivals during competition for resources. In the paper wasp Polistes dominulus, variable black clypeal patterns are thought to be important in mediating competition among females. Results of previous behavioral experiments in the lab indicate that P. dominulus clypeal patterns provide information about an individual's competitive ability to rivals during agonistic interactions. To date, however, there has been no detailed examination of the adaptive value of clypeal patterns in the wild. To address this, we looked for correlations between clypeal patterning and various fitness measures, including reproductive success, hierarchical rank, and survival, in a large, free-living population of P. dominulus in southern Spain. Reproductive success over the nesting season was not correlated with clypeal patterning. Furthermore, there was no relationship between a female's clypeal patterning and the rank she achieved within the hierarchy or her survival during nest founding. Overall, we found no evidence that P. dominulus clypeal patterns are related to competitive ability or other aspects of quality in our population. This result is consistent with geographical variation in the adaptive value of clypeal patterns between P. dominulus populations; however, data on the relationship between patterning and fitness from other populations are required to test this hypothesi

Exploiting stochastic locality in lattice QCD: hadronic observables and their uncertainties

Because of the mass gap, lattice QCD simulations exhibit stochastic locality: distant regions of the lattice fluctuate independently. There is a long history of exploiting this to increase statistics by obtaining multiple spatially-separated samples from each gauge field; in the extreme case, we arrive at the master-field approach in which a single gauge field is used. Here we develop techniques for studying hadronic observables using position-space correlators, which are more localized, and compare with the standard time-momentum representation. We also adapt methods for estimating the variance of an observable from autocorrelated Monte Carlo samples to the case of correlated spatially-separated samples.Comment: 45 pages, 16 figures, 3 table

Together for a Better Education Program (Juntos Para Una Mejor Educación)

A new program entitled Together for a Better Education Program or Juntos Para Una Mejor Educación (2011) targets underserved and minority audiences to help build a stronger alliance with families, schools and community based youth serving agencies to help youth reach their goals for a rewarding future. The primary goal of the program is to allow the dream of college to be a reality for youth as well as their families. This six (6) session workshop series is designed so families and youth participate in activities and lessons congruently to develop and reach shared goals focused on graduating from high school and attending post-secondary education