Contact process on a Voronoi triangulation

We study the continuous absorbing-state phase transition in the contact process on the Voronoi-Delaunay lattice. The Voronoi construction is a natural way to introduce quenched coordination disorder in lattice models. We simulate the disordered system using the quasistationary simulation method and determine its critical exponents and moment ratios. Our results suggest that the critical behavior of the disordered system is unchanged with respect to that on a regular lattice, i.e., that of directed percolation

Multiscale model for the effects of adaptive immunity suppression on the viral therapy of cancer

Oncolytic virotherapy - the use of viruses that specifically kill tumor cells - is an innovative and highly promising route for treating cancer. However, its therapeutic outcomes are mainly impaired by the host immune response to the viral infection. In the present work, we propose a multiscale mathematical model to study how the immune response interferes with the viral oncolytic activity. The model assumes that cytotoxic T cells can induce apoptosis in infected cancer cells and that free viruses can be inactivated by neutralizing antibodies or cleared at a constant rate by the innate immune response. Our simulations suggest that reprogramming the immune microenvironment in tumors could substantially enhance the oncolytic virotherapy in immune-competent hosts. Viable routes to such reprogramming are either in situ virus-mediated impairing of CD$8^+$ T cells motility or blockade of B and T lymphocytes recruitment. Our theoretical results can shed light on the design of viral vectors or new protocols with neat potential impacts on the clinical practice.Comment: 14 pages, 4 figure

An approximation to density functional theory for an accurate calculation of band-gaps of semiconductors

The local-density approximation (LDA), together with the half-occupation (transition state) is notoriously successful in the calculation of atomic ionization potentials. When it comes to extended systems, such as a semiconductor infinite system, it has been very difficult to find a way to half-ionize because the hole tends to be infinitely extended (a Bloch wave). The answer to this problem lies in the LDA formalism itself. One proves that the half-occupation is equivalent to introducing the hole self-energy (electrostatic and exchange-correlation) into the Schroedinger equation. The argument then becomes simple: the eigenvalue minus the self-energy has to be minimized because the atom has a minimal energy. Then one simply proves that the hole is localized, not infinitely extended, because it must have maximal self-energy. Then one also arrives at an equation similar to the SIC equation, but corrected for the removal of just 1/2 electron. Applied to the calculation of band gaps and effective masses, we use the self-energy calculated in atoms and attain a precision similar to that of GW, but with the great advantage that it requires no more computational effort than standard LDA.Comment: Zip file containing .tex and 6 .ps figure

CD4 T follicular cells and B cells

© 2023 Wiley-VCH GmbH.Regulatory and effector cell responses to Plasmodium vivax, the most common human malaria parasite outside Africa, remain understudied in naturally infected populations. Here, we describe peripheral CD4 + T- and B-cell populations during and shortly after an uncomplicated P. vivax infection in 38 continuously exposed adult Amazonians. Consistent with previous observations, we found an increased frequency in CD4 + CD45RA - CD25 + FoxP3 + T regulatory cells that express the inhibitory molecule CTLA-4 during the acute infection, with a sustained expansion of CD21 - CD27 - atypical memory cells within the CD19 + B-cell compartment. Both Th1- and Th2-type subsets of CXCR5 + ICOS hi PD-1 + circulating T follicular helper (cTfh) cells, which are thought to contribute to antibody production, were induced during P. vivax infection, with a positive correlation between overall cTfh cell frequency and IgG antibody titers to the P. vivax blood-stage antigen MSP1 19 . We identified significant changes in cell populations that had not been described in human malaria, such as an increased frequency of CTLA-4 + T follicular regulatory cells that antagonize Tfh cells, and a decreased frequency of circulating CD24 hi CD27 + B regulatory cells in response to acute infection. In conclusion, we disclose a complex immunoregulatory network that is critical to understand how naturally acquired immunity develops in P. vivax malaria.publishersversionepub_ahead_of_prin

Nuclear structure model for double-charge-exchange processes

A new model, based on the BCS approach, is especially designed to describe nuclear phenomena (A, Z) → (A, Z ± 2) of double-charge exchange (DCE). Although it was proposed and applied in the particle-hole limit, by one of the authors [Krmpotić, Fizika B 14, 139 (2005)], it has not yet been applied within the BCS mean-field framework, nor has its ability to describe DCE processes been thoroughly explored. It is a natural extension of the pn-QRPA model, developed by Halbleib and Sorensen [Nucl. Phys. A 98, 542 (1967)] to describe the single β decays (A, Z) → (A, Z ± 1), to the DCE processes. As such, it exhibits several advantages over the pn-QRPA model when used in the evaluation of the double beta decay (DBD) rates. For instance, (i) the extreme sensitivity of the nuclear matrix elements (NMEs) on the model parametrization does not occur; (ii) it allows us to study the NMEs, not only for the ground state in daughter nuclei, as the pn-QRPA model does, but also for all final 0⁺ and 2⁺ states, accounting at the same time for their excitation energies and the corresponding DBD Q values; (iii) together with the DBD-NMEs it also provides the energy spectra of Fermi and Gamow-Teller DCE transition strengths, as well as the locations of the corresponding resonances and their sum rules; (iv) the latter are relevant for both the DBD and the DCE reactions, since the underlying nuclear structure is the same; this correlation does not exist within the pn-QRPA model. As an example, detailed numerical calculations are presented for the (A, Z) → (A, Z + 2) process in ⁴⁸Ca → ⁴⁸Ti and the (A, Z) → (A, Z − 2) process in ⁹⁶Ru → ⁹⁶Mo, involving all final 0⁺ states and 2⁺ states.Facultad de Ciencias ExactasInstituto de Física La Plat