Do we understand the incompressibility of neutron-rich matter?

The ``breathing mode'' of neutron-rich nuclei is our window into the incompressibility of neutron-rich matter. After much confusion on the interpretation of the experimental data, consistency was finally reached between different models that predicted both the distribution of isoscalar monopole strength in finite nuclei and the compression modulus of infinite matter. However, a very recent experiment on the Tin isotopes at the Research Center for Nuclear Physics(RCNP) in Japan has again muddled the waters. Self-consistent models that were successful in reproducing the energy of the giant monopole resonance (GMR) in nuclei with various nucleon asymmetries (such as 90Zr, 144Sm, and 208Pb) overestimate the GMR energies in the Tin isotopes. As important, the discrepancy between theory and experiment appears to grow with neutron excess. This is particularly problematic as models artificially tuned to reproduce the rapid softening of the GMR in the Tin isotopes become inconsistent with the behavior of dilute neutron matter. Thus, we regard the question of ``why is Tin so soft?'' as an important open problem in nuclear structure.Comment: 12 pages, 3 figures, and 1 table. Submitted to the "Focus issue on Open Problems in Nuclear Structure", Journal of Physics

Nonuniform Neutron-Rich Matter and Coherent Neutrino Scattering

Nonuniform neutron-rich matter present in both core-collapse supernovae and neutron-star crusts is described in terms of a semiclassical model that reproduces nuclear-matter properties and includes long-range Coulomb interactions. The neutron-neutron correlation function and the corresponding static structure factor are calculated from molecular dynamics simulations involving 40,000 to 100,000 nucleons. The static structure factor describes coherent neutrino scattering which is expected to dominate the neutrino opacity. At low momentum transfers the static structure factor is found to be small because of ion screening. In contrast, at intermediate momentum transfers the static structure factor displays a large peak due to coherent scattering from all the neutrons in a cluster. This peak moves to higher momentum transfers and decreases in amplitude as the density increases. A large static structure factor at zero momentum transfer, indicative of large density fluctuations during a first-order phase transition, may increase the neutrino opacity. However, no evidence of such an increase has been found. Therefore, it is unlikely that the system undergoes a simple first-order phase transition. It is found that corrections to the commonly used single heavy nucleus approximation first appear at a density of the order of $10^{13}$ g/cm$^3$ and increase rapidly with increasing density. Thus, neutrino opacities are overestimated in the single heavy nucleus approximation relative to the complete molecular dynamics simulations.Comment: 17 pages, 23 included ps figure

Acción del análogo tumoral de PTH (PTHrP) en la regulación de factores asociados al fenotipo invasivo y a la angiogénesis en células de cáncer de colon humano

El péptido relacionado con la hormona paratiroidea (PTHrP) está implicado en varios cánceres humanos, entre los que se encuentra el cáncer colorrectal (CCR). Esta patología implica varios procesos, como mayor supervivencia celular, proliferación, migración, invasión, transición epitelio-mesenquimática (TEM) y angiogénesis. Previamente encontramos que PTHrP induce la proliferación, supervivencia y migración de células Caco-2 y HCT116, dos líneas celulares de tumores de colon humano. La invasión celular durante la progresión del cáncer se ha asociado a la pérdida de características epiteliales, la remodelación de la matriz extracelular, y el desarrollo de vascularización, por lo que abordar estos procesos es de relevancia para entender el rol de PTHrP en la enfermedad y constituye el objetivo de este trabajo. Se observó que el tratamiento con PTHrP 10-8 M en estas células aumenta los niveles de ARNm de la metaloproteinasa de la matriz 7 (MMP-7) y la expresión proteica de la proteína ácida y rica en cisteína SPARC, dos proteínas que participan en la reestructuración del estroma y que están fuertemente implicadas en la invasión tumoral. Además el tratamiento con PTHrP disminuyó los niveles proteicos de citoqueratina-18 (CK-18) un marcador epitelial asociado con TEM mediante Western blot e Inmunocitoquímica. Los niveles del factor de crecimiento endotelial vascular (VEGF), del factor inducible por hipoxia 1α (HIF-1α) y de la metaloproteinasa de la matriz 9 (MMP-9) por RT-qPCR mostraron que PTHrP aumenta la transcripción de estos factores implicados en la angiogénesis tumoral. Estos resultados sugieren un nuevo rol de PTHrP en la regulación de fenómenos asociados a un fenotipo más agresivo de células derivadas de cáncer colorrectalFil: Carriere, P.. Universidad Nacional del Sur.Fil: Riquelme, A.N.. Universidad Nacional del Sur.Fil: Novoa Díaz, M.B.. Universidad Nacional del Sur.Fil: Calvo, N. . Universidad Nacional del Sur.Fil: Gentili, C.. Universidad Nacional del Sur

Tokenizzazione di azioni e azioni tokens

Il lavoro analizza il fenomeno della rappresentazione delle partecipazioni azionarie in tokens e delle azioni tokens native. Dopo una breve illustrazione della circolazione della ric- chezza nella tecnologia a registro distribuito (distributed ledger technology, c.d. DLT), lo studio esamina la nozione di cripto-attività e la relativa tassonomia, come elaborate dalla proposta di Regolamento (UE) MiCA (Market in Crypto-Asset), evidenziando le criticità di inquadramento. L’attenzione si sofferma altresì sulle verosimili ripercussioni dell’approvazione del Regolamento (UE) 2022/858 relativo a un regime pilota. Successivamente il contributo approfondisce le cripto-attività nella prospettiva societaria mediante una valutazione di assimilabilità dei security tokens ai tradizionali strumenti finanziari e svolge una distinzione tra security tokens e utility tokens e tra utility tokens e NFT (non-fungible tokens). Muovendo da una ricostruzione delle tecniche di legittimazione e circolazione delle partecipazioni sociali previste dal Codice civile, il testo delinea la possibilità di rappresentare, de iure condito, azioni, quote o altri strumenti so- cietari su DLT e ne valuta la compatibilità con il quadro giuridico vigente. In conclusione, il lavoro formula alcune proposte de iure condendo per l’applicazione della tecnologia DLT nelle infra- strutture di mercato

Structure and Magnetism of well-defined cobalt nanoparticles embedded in a niobium matrix

Our recent studies on Co-clusters embedded in various matrices reveal that the co-deposition technique (simultaneous deposition of two beams : one for the pre-formed clusters and one for the matrix atoms) is a powerful tool to prepare magnetic nanostructures with any couple of materials even though they are miscible. We study, both sharply related, structure and magnetism of the Co/Nb system. Because such a heterogeneous system needs to be described at different scales, we used microscopic and macroscopic techniques but also local selective absorption ones. We conclude that our clusters are 3 nm diameter f.c.c truncated octahedrons with a pure cobalt core and a solid solution between Co and Nb located at the interface which could be responsible for the magnetically inactive monolayers we found. The use of a very diluted Co/Nb film, further lithographed, would allow us to achieve a pattern of microsquid devices in view to study the magnetic dynamics of a single-Co cluster.Comment: 7 TeX pages, 9 Postscript figures, detailed heading adde

Rheological characterization of jet-cooked Lesquerella fendleri seed gum and cornstarch solutions

Abstract Lesquerella is a potential new seed crop that contains hydroxy fatty acid triglycerides and approximately 15% seed coat gums. The polysaccharide gum of the Lesquerella fendleri seed was isolated and jet-cooked with cornstarch in a series of laboratory experiments to investigate the viscoelastic properties of gum-modified starch solutions. The Lesquerella gum was combined with cornstarch at 1, 5, and 10% levels to produce a jet-cooked and drum dried material with potential application as a thickening or suspension agent. Flow curves were determined for 1% solutions of jet-cooked starch and gum combinations. All materials investigated were biodegradable and exhibited positive thixotropic behavior