212 research outputs found
Physical consequences of PNP and the DMRG-annealing conjecture
Computational complexity theory contains a corpus of theorems and conjectures
regarding the time a Turing machine will need to solve certain types of
problems as a function of the input size. Nature {\em need not} be a Turing
machine and, thus, these theorems do not apply directly to it. But {\em
classical simulations} of physical processes are programs running on Turing
machines and, as such, are subject to them. In this work, computational
complexity theory is applied to classical simulations of systems performing an
adiabatic quantum computation (AQC), based on an annealed extension of the
density matrix renormalization group (DMRG). We conjecture that the
computational time required for those classical simulations is controlled
solely by the {\em maximal entanglement} found during the process. Thus, lower
bounds on the growth of entanglement with the system size can be provided. In
some cases, quantum phase transitions can be predicted to take place in certain
inhomogeneous systems. Concretely, physical conclusions are drawn from the
assumption that the complexity classes {\bf P} and {\bf NP} differ. As a
by-product, an alternative measure of entanglement is proposed which, via
Chebyshev's inequality, allows to establish strict bounds on the required
computational time.Comment: Accepted for publication in JSTA
Reconstruction of the second layer of Ag on Pt(111)
The reconstruction of an Ag monolayer on Ag/Pt(111) is analyzed
theoretically, employing a vertically extended Frenkel-Kontorova model whose
parameters are derived from density functional theory. Energy minimization is
carried out using simulated quantum annealing techniques. Our results are
compatible with the STM experiments, where a striped pattern is initially found
which transforms into a triangular reconstruction upon annealing. In our model
we recognize the first structure as a metastable state, while the second one is
the true energy minimum
The H=xp model revisited and the Riemann zeros
Berry and Keating conjectured that the classical Hamiltonian H = xp is
related to the Riemann zeros. A regularization of this model yields
semiclassical energies that behave, in average, as the non trivial zeros of the
Riemann zeta function. However, the classical trajectories are not closed,
rendering the model incomplete. In this paper, we show that the Hamiltonian H =
x (p + l_p^2/p) contains closed periodic orbits, and that its spectrum
coincides with the average Riemann zeros. This result is generalized to
Dirichlet L-functions using different self-adjoint extensions of H. We discuss
the relation of our work to Polya's fake zeta function and suggest an
experimental realization in terms of the Landau model.Comment: 5 pages, 3 figure
Entanglement hamiltonian and entanglement contour in inhomogeneous 1D critical systems
Inhomogeneous quantum critical systems in one spatial dimension have been studied by using conformal field theory in static curved backgrounds. Two interesting examples are the free fermion gas in the harmonic trap and the inhomogeneous XX spin chain called rainbow chain. For conformal field theories defined on static curved spacetimes characterised by a metric which is Weyl equivalent to the flat metric, with the Weyl factor depending only on the spatial coordinate, we study the entanglement hamiltonian and the entanglement spectrum of an interval adjacent to the boundary of a segment where the same boundary condition is imposed at the endpoints. A contour function for the entanglement entropies corresponding to this configuration is also considered, being closely related to the entanglement hamiltonian. The analytic expressions obtained by considering the curved spacetime which characterises the rainbow model have been checked against numerical data for the rainbow chain, finding an excellent agreement
Las cĂ©lulas presentadoras de antĂgeno y su papel en el sĂndrome reproductivo y respiratorio porcino
Las cĂ©lulas presentadoras de antĂgeno son aquellas cĂ©lulas encargadas de capturar, procesar y presentar antĂgenos con la finalidad de lograr una respuesta inmune efectiva por parte del organismo. Su papel, como centinelas, es crucial durante el transcurso de diversas enfermedades infecciosas. El estudio de estas cĂ©lulas tras la infecciĂłn con el virus del SĂndrome Reproductivo y Respiratorio Porcino nos da informaciĂłn para abordar nuevas estrategias de control frente a esta enfermedad.Antigen presenting cells are able to capture, process and present antigens in order to develop an effective immune response. The role of these cells during infectious diseases is crucial to control the disease. Thus, the study of these cells after the infection with Porcine Reproductive and Respiratory Syndrome Virus gives us useful information on how to control this disease
2-DE analysis of sera protein expression profiles in early stages of human neonatal development. A preliminary study.
Comunicaciones a congreso
Bases de la respuesta inflamatoria en la forma respiratoria del PRRS
El SĂndrome Reproductivo y Respiratorio Porcino (PRRS) es una enfermedad de distribuciĂłn mundial que causa graves pĂ©rdidas econĂłmicas al sector porcino. Este virus no sĂłlo es importante como agente causal del PRRS sino tambiĂ©n por su participaciĂłn en el desarrollo del Complejo Respiratorio Porcino. Su interacciĂłn con las defensas pulmonares, la alteraciĂłn de la respuesta inmune y su persistencia en los Ăłrganos linfoides conlleva a que los cerdos tengan dificultades para luchar contra la enfermedad.Porcine Reproductive and Respiratory Syndrome (PRRS) is considered as the most economically important disease of the modern swine industry. The importance of this virus lies in not only being the causative agent of PRRSV, but also due to its implication in the onset of the Porcine Respiratory Disease Complex. The interaction of the virus with pulmonary defenses, the impairment of the immune response as well as the viral persistence in lymphoid organs make overcoming the disease diffi cult to infected pigs
The jigsaw of PRRSV virulence
Porcine reproductive and respiratory syndrome virus (PRRSV) is the causative agent of the, probably, most economically important disease for the pig industry worldwide. This disease, characterised by producing reproductive failure in sows and respiratory problems in growing pigs, appeared in the late 1980s in the United States and Canada. Since its appearance, strains capable of producing higher mortality rates as well as greater severity in clinical signs and lesions than classical strains have been identified. However, since the first reports of these “virulent” PRRSV outbreaks, no homogeneity and consensus in their description have been established. Moreover, to the authors’ knowledge, there is no published information related to the criteria that a PRRSV strain should fulfil to be considered as a “virulent” strain. In this review, we revise the terminology used and gather the information related to the main characteristics and differences in clinical signs, lesions, viral replication and tropism as well as immunological parameters between virulent and classical PRRSV strains and propose a first approximation to the criteria to define a virulent PRRSV strain
Ergotropy and entanglement in critical spin chains
A subsystem of an entangled ground state is in a mixed state. Thus, if we
isolate this subsystem from its surroundings we may be able to extract work
applying unitary transformations, up to a maximal amount which is called
ergotropy. Once this work has been extracted, the subsystem will still contain
some bound energy above its local ground state, which can provide valuable
information about the entanglement structure. We show that the bound energy for
half a free fermionic chain decays as the square of the entanglement entropy
divided by the chain length, thus approaching zero for large system sizes, and
we conjecture that this relation holds for all 1D critical states
Activation of T-bet, FOXP3, and EOMES in Target Organs From Piglets Infected With the Virulent PRRSV-1 Lena Strain
Transcription factors (TFs) modulate genes involved in cell-type-specific proliferative and migratory properties, metabolic features, and effector functions. Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most important pathogen agents in the porcine industry; however, TFs have been poorly studied during the course of this disease. Therefore, we aimed to evaluate the expressions of the TFs T-bet, GATA3, FOXP3, and Eomesodermin (EOMES) in target organs (the lung, tracheobronchial lymph node, and thymus) and those of different effector cytokines (IFNG, TNFA, and IL10) and the Fas ligand (FASL) during the early phase of infection with PRRSV-1 strains of different virulence. Target organs from mock-, virulent Lena-, and low virulent 3249-infected animals humanely euthanized at 1, 3, 6, 8, and 13 days post-infection (dpi) were collected to analyze the PRRSV viral load, histopathological lesions, and relative quantification through reverse transcription quantitative PCR (RT-qPCR) of the TFs and cytokines. Animals belonging to both infected groups, but mainly those infected with the virulent Lena strain, showed upregulation of the TFs T-bet, EOMES, and FOXP3, together with an increase of the cytokine IFN-g in target organs at the end of the study (approximately 2 weeks post-infection). These results are suggestive of a stronger polarization to Th1 cells and regulatory T cells (Tregs), but also CD4+ cytotoxic T lymphocytes (CTLs), effector CD8+ T cells, and gdT cells in virulent PRRSV-1-infected animals; however, their biological functionality should be the object of further studies
- …