Collective modes of trapped Fermi gases with in-medium interaction

Due to Pauli blocking of intermediate states, the scattering matrix (or $T$ matrix) of two fermionic atoms in a Fermi gas becomes different from that of two atoms in free space. This effect becomes particularly important near a Feshbach resonance, where the interaction in free space is very strong but becomes effectively suppressed in the medium. We calculate the in-medium $T$ matrix in ladder approximation and study its effects on the properties of collective modes of a trapped gas in the normal-fluid phase. We introduce the in-medium interaction on both sides of the Boltzmann equation, namely in the calculation of the mean field and in the calculation of the collision rate. This allows us to explain the observed upward shift of the frequency of the quadrupole mode in the collisionless regime. By including the mean field, we also improve considerably the agreement with the measured temperature dependence of frequency and damping rate of the scissors mode, whereas the use of the in-medium cross section deteriorates the description, in agreement with previous work.Comment: 17 page

Shear Viscosity of Quark Matter

We consider the shear viscosity of a system of quarks and its ratio to the entropy density above the critical temperature for deconfinement. Both quantities are derived and computed for different modeling of the quark self-energy, also allowing for a temperature dependence of the effective mass and width. The behaviour of the viscosity and the entropy density is argued in terms of the strength of the coupling and of the main characteristics of the quark self-energy. A comparison with existing results is also discussed.Comment: 15 pages, 4 figure

Light clusters and the pasta phase

The effects of including light clusters in nuclear matter at low densities are investigated within four different parametrizations of relativistic models at finite temperature. Both homogeneous and inhomogeneous matter (pasta phase) are described for neutral nuclear matter with fixed proton fractions. We discuss the effect of the density dependence of the symmetry energy, the temperature and the proton fraction on the non-homogeneous matter forming the inner crust of proto-neutron stars. It is shown that the number of nucleons in the clusters, the cluster proton fraction and the sizes of the Wigner Seitz cell and of the cluster are very sensitive to the density dependence of the symmetry energy.Comment: 14 pages, 14 figures; Accepted for publication in Phys. Rev.

Detecting composite orders in layered models via machine learning

Determining the phase diagram of systems consisting of smaller subsystems 'connected' via a tunable coupling is a challenging task relevant for a variety of physical settings. A general question is whether new phases, not present in the uncoupled limit, may arise. We use machine learning and a suitable quasidistance between different points of the phase diagram to study layered spin models, in which the spin variables constituting each of the uncoupled systems (to which we refer as layers) are coupled to each other via an interlayer coupling. In such systems, in general, composite order parameters involving spins of different layers may emerge as a consequence of the interlayer coupling. We focus on the layered Ising and Ashkin–Teller models as a paradigmatic case study, determining their phase diagram via the application of a machine learning algorithm to the Monte Carlo data. Remarkably our technique is able to correctly characterize all the system phases also in the case of hidden order parameters, i.e. order parameters whose expression in terms of the microscopic configurations would require additional preprocessing of the data fed to the algorithm. We correctly retrieve the three known phases of the Ashkin–Teller model with ferromagnetic couplings, including the phase described by a composite order parameter. For the bilayer and trilayer Ising models the phases we find are only the ferromagnetic and the paramagnetic ones. Within the approach we introduce, owing to the construction of convolutional neural networks, naturally suitable for layered image-like data with arbitrary number of layers, no preprocessing of the Monte Carlo data is needed, also with regard to its spatial structure. The physical meaning of our results is discussed and compared with analytical data, where available. Yet, the method can be used without any a priori knowledge of the phases one seeks to find and can be applied to other models and structures

The multilevel pairing Hamiltonian versus the degenerate case

We study the pairing Hamiltonian in a set of non degenerate levels. First, we review in the path integral framework the spontaneous breaking of the U(1) symmetry occurring in such a system for the degenerate situation. Then the behaviors with the coupling constant of the ground state energy in the multilevel and in the degenerate case are compared. Next we discuss, in the multilevel case, an exact strong coupling expansion for the ground state energy which introduces the moments of the single particle level distribution. The domain of validity of the expansion, which is known in the macroscopic limit, is explored for finite systems and its implications for the energy of the latter is discussed. Finally the seniority and Gaudin excitations of the pairing Hamiltonian are addressed and shown to display the same gap in leading order.Comment: 20 pages, 4 figure

Maintenance of leukemic cell identity by the activity of the Polycomb complex PRC1 in mice

Leukemia is a complex heterogeneous disease often driven by the expression of oncogenic fusion proteins with different molecular and biochemical properties. Whereas several fusion proteins induce leukemogenesis by activating Hox gene expression (Hox-activating fusions), others impinge on different pathways that do not involve the activation of Hox genes (non-Hox-activating fusions). It has been postulated that one of the main oncogenic properties of the HOXA9 transcription factor is its ability to control the expression of the p16/p19 tumor suppressor locus (Cdkn2a), thereby compensating Polycomb-mediated repression, which is dispensable for leukemias induced by Hox-activating fusions. We show, by genetically depleting the H2A ubiquitin ligase subunits of the Polycomb repressive complex 1 (PRC1), Ring1a and Ring1b, that Hoxa9 activation cannot repress Cdkn2a expression in the absence of PRC1 and its dependent deposition of H2AK119 monoubiquitination (H2AK119Ub). This demonstrates the essential role of PRC1 activity in supporting the oncogenic potential of Hox-activating fusion proteins. By combining genetic tools with genome-wide location and transcription analyses, we further show that PRC1 activity is required for the leukemogenic potential of both Hox-activating and non-Hox-activating fusions, thus preventing the differentiation of leukemic cells independently of the expression of the Cdkn2a locus. Overall, our results genetically demonstrate that PRC1 activity and the deposition of H2AK119Ub are critical factors that maintain the undifferentiated identity of cancer cells, positively sustaining the progression of different types of leukemia

Efecto de la concentración salina y el regimen hídrico sobre la germinación, emergencia y establecimiento de alfalfa (Medicago sativa L.)

Los suelos halo-hidromórficos de la región húmeda y subhúmeda de Argentina suman aproximadamente 20 millones de hectáreas, un amplio porcentaje de estos presentan vegetación nativa de baja producción de biomasa y consumo de agua. Entender el funcionamiento de especies forrajeras perennes como alfalfa en estos sitios es de suma importancia para mejorar la producción de los sistemas allí ubicados. El objetivo de este trabajo fue comprender y cuantificar el efecto de la salinidad y el contenido hídrico edáfico sobre la germinación, emergencia y establecimiento temprano del cultivo de alfalfa. Así se realizaron tres experimentos a diferentes escalas: (E1) experimento en cámara de germinación, con el fin de determinar, bajo condiciones controladas, el efecto de diferentes condiciones de salinidad y disponibilidad hídrica sobre la germinación y emergencia de alfalfa; (E2) un experimento en invernáculo para evaluar el efecto del estrés hídrico (por exceso o por defecto) sobre plantas de alfalfa en la etapa de establecimiento temprano; y (E3) un experimento a campo, con el fin de identificar y jerarquizar indicadores ambientales determinantes de la emergencia, establecimiento y producción del cultivo de alfalfa. Se halló que en ambientes halo-hidromórficos la concentración salina fue la principal variable determinante del crecimiento y supervivencia de la especie durante las etapas tempranas con límites cercanos a 4 dS.m-1. El exceso o déficit hídrico afectó al stand de plantas, reduciendo a la mitad el número de individuos. La plasticidad fenotípica de la alfalfa frente a diferentes tenores salinos, así como al estrés hídrico (por exceso o por defecto) determina que sea una especie para considerar cuando se pretende producir biomasa de alta calidad, distribuida en el tiempo, en este tipo de ambientes.The halo-hydromorphic soils of the humid and sub-humid region of Argentina cover approximately 20 million hectares. A large proportion of them have native vegetation with low biomass production and water consumption. Understanding the functioning of perennial forage species such as alfalfa in these sites is of paramount importance to improve the productivity of the grazing systems located there. The objective of this work is to understand and quantify the effect of salinity and soil water content on the germination, emergence and early establishment of alfalfa. Three experiments were carried out at different scales: (E1) germination chamber experiment, to determine, under controlled conditions, the effect of different salinity and water availability conditions on the germination and emergence of alfalfa; (E2) a greenhouse experiment to assess the effect of water stress (by insufficiency or excess) on alfalfa plants in the early establishment stage; and (E3) a field experiment, to identify and rank environmental indicators that determine the emergence, establishment and production of alfalfa. It was found that, in halo-hydromorphic environments, saline concentration was the main variable affecting alfalfa growth and survival during the early stages, where salinity levels close to 4 dS.m-1. Water stress by excess or water deficit affected plant stands, halving the number of individuals. The phenotypic plasticity of alfalfa against different salinity and water conditions, makes it a species to consider to produce high quality biomass, distributed over time, in this type of environment.EEA Marcos JuárezFil: Bertram, Nicolas. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Marcos Juárez; ArgentinaFil: Alfonso, C. Asociación Universitaria de Enseñanza Agropecuaria Superior. Becaria INTA-AUDEASFil: Grande, S. Universidad Nacional de Río Cuarto. Facultad de Ciencias Agrarias; ArgentinaFil: Chiacchiera, Sebastián. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Marcos Juárez; ArgentinaFil: Ohanian, Alfredo. Universidad Nacional de Río Cuarto. Facultad de Ciencias Agrarias; ArgentinaFil: Bonvillani, Julieta. Universidad Nacional de Río Cuarto. Facultad de Ciencias Agrarias; ArgentinaFil: Conde, Maria Belen. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Marcos Juárez; ArgentinaFil: Angeletti, Fernando Ramón. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Marcos Juárez; Argentin

Modification of Collagen by 3-Deoxyglucosone Alters Wound Healing through Differential Regulation of p38 MAP Kinase

Background: Wound healing is a highly dynamic process that requires signaling from the extracellular matrix to the fibroblasts for migration and proliferation, and closure of the wound. This rate of wound closure is impaired in diabetes, which may be due to the increased levels of the precursor for advanced glycation end products, 3-deoxyglucosone (3DG). Previous studies suggest a differential role for p38 mitogen-activated kinase (MAPK) during wound healing; whereby, p38 MAPK acts as a growth kinase during normal wound healing, but acts as a stress kinase during diabetic wound repair. Therefore, we investigated the signaling cross-talk by which p38 MAPK mediates wound healing in fibroblasts cultured on native collagen and 3DG-collagen. Methodology/Principal Findings: Using human dermal fibroblasts cultured on 3DG-collagen as a model of diabetic wounds, we demonstrated that p38 MAPK can promote either cell growth or cell death, and this was dependent on the activation of AKT and ERK1/2. Wound closure on native collagen was dependent on p38 MAPK phosphorylation of AKT and ERK1/2. Furthermore, proliferation and collagen production in fibroblasts cultured on native collagen was dependent on p38 MAPK regulation of AKT and ERK1/2. In contrast, 3DG-collagen decreased fibroblast migration, proliferation, and collagen expression through ERK1/2 and AKT downregulation via p38 MAPK. Conclusions/Significance: Taken together, the present study shows that p38 MAPK is a key signaling molecule that plays

An Aqueous Extract of Fagonia cretica Induces DNA Damage, Cell Cycle Arrest and Apoptosis in Breast Cancer Cells via FOXO3a and p53 Expression

Background - Plants have proved to be an important source of anti-cancer drugs. Here we have investigated the cytotoxic action of an aqueous extract of Fagonia cretica, used widely as a herbal tea-based treatment for breast cancer. Methodology/Principal Findings - Using flow cytometric analysis of cells labeled with cyclin A, annexin V and propidium iodide, we describe a time and dose-dependent arrest of the cell cycle in G0/G1 phase of the cell cycle and apoptosis following extract treatment in MCF-7 (WT-p53) and MDA-MB-231 (mutant-p53) human breast cancer cell lines with a markedly reduced effect on primary human mammary epithelial cells. Analysis of p53 protein expression and of its downstream transcription targets, p21 and BAX, revealed a p53 associated growth arrest within 5 hours of extract treatment and apoptosis within 24 hours. DNA double strand breaks measured as ?-H2AX were detected early in both MCF-7 and MDA-MB-231 cells. However, loss of cell viability was only partly due to a p53-driven response; as MDA-MB-231 and p53-knockdown MCF-7 cells both underwent cell cycle arrest and death following extract treatment. p53-independent growth arrest and cytotoxicity following DNA damage has been previously ascribed to FOXO3a expression. Here, in MCF-7 and MDA-MB-231 cells, FOXO3a expression was increased significantly within 3 hours of extract treatment and FOXO3 siRNA reduced the extract-induced loss of cell viability in both cell lines. Conclusions/Significance - Our results demonstrate for the first time that an aqueous extract of Fagonia cretica can induce cell cycle arrest and apoptosis via p53-dependent and independent mechanisms, with activation of the DNA damage response. We also show that FOXO3a is required for activity in the absence of p53. Our findings indicate that Fagonia cretica aqueous extract contains potential anti-cancer agents acting either singly or in combination against breast cancer cell proliferation via DNA damage-induced FOXO3a and p53 expression