University of Costa Rica

About: University of Costa Rica is a education organization based out in San José, Costa Rica. It is known for research contribution in the topics: Population & Venom. The organization has 9817 authors who have published 16781 publications receiving 238208 citations. The organization is also known as: UCR & Universidad de Costa Rica.

Analysis of nucleon electromagnetic form factors from light-front holographic QCD : The spacelike region

Abstract: We present a comprehensive analysis of the spacelike nucleon electromagnetic form factors and their flavor decomposition within the framework of light-front (LF) holographic QCD (LFHQCD) We show that the inclusion of the higher Fock components $|qqqq\overline{q}⟩$ has a significant effect on the spin-flip elastic Pauli form factor and almost zero effect on the spin-conserving Dirac form factor. We present light-front holographic QCD results for the proton and neutron form factors at any momentum transfer range, including asymptotic predictions, and show that our results agree with the available experimental data with high accuracy. In order to correctly describe the Pauli form factor we need an admixture of a five quark state of about 30% in the proton and about 40% in the neutron. We also extract the nucleon charge and magnetic radii and perform a flavor decomposition of the nucleon electromagnetic form factors. The free parameters needed to describe the experimental nucleon form factors are very few: two parameters for the probabilities of higher Fock states for the spin-flip form factor and a phenomenological parameter $r$, required to account for possible SU(6) spin-flavor symmetry breaking effects in the neutron, whereas the Pauli form factors are normalized to the experimental values of the anomalous magnetic moments. The covariant spin structure for the Dirac and Pauli nucleon form factors prescribed by ${\mathrm{AdS}}_{5}$ semiclassical gravity incorporates the correct twist scaling behavior from hard scattering and also leads to vector dominance at low energy.

Macrophage-derived lipocalin-2 transports iron in the tumor microenvironment

Abstract: While the importance of iron for tumor development is widely appreciated, the exact sources of tumor-supporting iron largely remain elusive. The possibility that iron might be provided by stromal cells in the tumor microenvironment was not taken into account so far. In the present study, we show that tumor-associated macrophages (TAM) acquire an iron-release phenotype upon their interaction with tumor cells, thereby increasing the availability of iron in the tumor microenvironment. Mechanistically, TAM expressed elevated levels of the high-affinity iron-binding protein lipocalin-2 (LCN-2), which appeared to be critical for the export of iron from TAM, and in turn enhanced tumor cell proliferation. Moreover, in PyMT-mouse tumors as well as in primary human breast tumors LCN-2 was predominantly expressed in the tumor stroma as compared to tumor cells. LCN-2 expression in the stroma further correlated with enhanced tumor proliferation in vivo. Our data suggest a dominant role of TAM in the tumor iron-management and identify LCN-2 as a critical iron transporter in this context. Targeting the LCN-2 iron export mechanism selectively in stromal cells might open for future iron-targeted tumor therapeutic approaches.

Use of qualitative research in foodservice organizations: a review of challenges, strategies, and applications

Abstract: Purpose – The purpose of this paper is to present the challenges encountered when conducting qualitative research in foodservice operations and to discuss the strategies to overcome the identified challenges.Design/methodology/approach – The researchers conducted food safety observations, interviews, and focus groups with more than 600 foodservice employees and managers. The researchers encountered multiple challenges including institutional review board approvals, managements' willingness to participate, and organizational and cultural barriers.Findings – Obtaining in‐depth, credible information through observations, interviews, and focus groups adds depth and breadth to hospitality studies. However, given high industry turnover, recruitment and retention throughout a study is problematic. Moreover, researchers encounter many barriers as they obtain data, such as establishing authenticity and overcoming Hawthorne and halo effects.Originality/value – Strategies to increase participation and thereby improv...