Ivan D. Rodriguez

Immune response of zebrafish (Danio rerio) against a newly isolated bacterial pathogen Aeromonas hydrophila

A strain of Aeromonas hydrophila associated with unusual mortalities in zebrafish (Danio rerio) culture facilities was isolated, identified and characterized. In challenge experiments, adult zebrafish were susceptible to infection by intraperitoneal (i.p.) injection with viable bacteria and its extracellular products (ECPs) reaching very high mortalities in a few hours. The infection, by the viable bacteria or the ECPs, caused cell death in kidney, due to the cytotoxic and haemolytic activities of the bacterial ECPs. Moreover, the infection affected the release of oxygen (ROS) and nitrogen (NO) reactive free radicals. To determine if this A. hydrophila infection induces an inflammatory response, mRNA expression levels of tumour necrosis factor-alpha (TNFalpha), interleukin-1beta (IL-1beta), interferon-gamma (IFNgamma) and inducible nitric oxide (iNOS) were assessed by real time PCR. The expression levels of TNFalpha, IL-1beta and IFNgamma were upregulated in the kidneys of infected zebrafish with viable bacteria, heat-killed bacteria and ECPs. Expression levels of iNOS were upregulated by ECPs. Mortality rate (LD(50)) and histopathology were also determined.

β-Glucan administration enhances disease resistance and some innate immune responses in zebrafish (Danio rerio)

The present study was conducted to investigate the effect of beta-glucan (derived from Saccharomyces cerevisiae) on the immune response and its protection against an infection of the bacterial pathogen Aeromonas hydrophila in zebrafish (Danio rerio). Zebrafish received beta-glucan by intraperitoneal injection at three different concentrations (5, 2 and 0.5 mgml(-1)) at 6, 4 and 2 days prior the challenge. On challenge day the control and beta-glucan pretreated zebrafish were intraperitoneally injected with A. hydrophila and mortality was recorded for 4 days. Intraperitoneal injection of 5 mgml(-1) of beta-glucan significantly reduced the mortality. A single injection of 5 mgml(-1) of beta-glucan 6 days before challenge also enhanced significantly the survival against the infection. The treatment with beta-glucan increased the myelomonocytic cell population in the kidney at 6h postchallenge with A. hydrophila. Moreover it enhanced the ability of kidney cells to kill A. hydrophila. beta-glucan did not affect the expression of TNFalpha or IL-1 beta but seemed to modulate IFNgamma and chemokine expression in kidney.

Evaluation of ranks of real space and particle entanglement spectra for large systems.

We devise a way to calculate the dimensions of symmetry sectors appearing in the particle entanglement spectrum (PES) and real space entanglement spectrum (RSES) of multiparticle systems from their real space wave functions. We first note that these ranks in the entanglement spectra equal the dimensions of spaces of wave functions with a number of particles fixed. This also yields equality of the multiplicities in the PES and the RSES. Our technique allows numerical calculations for much larger systems than were previously feasible. For somewhat smaller systems, we can find approximate entanglement energies as well as multiplicities. We illustrate the method with results on the RSES and PES multiplicities for integer quantum Hall states, Laughlin and Jain composite fermion states, and for the Moore-Read state at filling ν = 5/2 for system sizes up to 70 particles.

Neural-Network Quantum States, String-Bond States, and Chiral Topological States

Neural-Network Quantum States have been recently introduced as an Ansatz for describing the wave function of quantum many-body systems. We show that there are strong connections between Neural-Network Quantum States in the form of Restricted Boltzmann Machines and some classes of Tensor-Network states in arbitrary dimensions. In particular we demonstrate that short-range Restricted Boltzmann Machines are Entangled Plaquette States, while fully connected Restricted Boltzmann Machines are String-Bond States with a nonlocal geometry and low bond dimension. These results shed light on the underlying architecture of Restricted Boltzmann Machines and their efficiency at representing many-body quantum states. String-Bond States also provide a generic way of enhancing the power of Neural-Network Quantum States and a natural generalization to systems with larger local Hilbert space. We compare the advantages and drawbacks of these different classes of states and present a method to combine them together. This allows us to benefit from both the entanglement structure of Tensor Networks and the efficiency of Neural-Network Quantum States into a single Ansatz capable of targeting the wave function of strongly correlated systems. While it remains a challenge to describe states with chiral topological order using traditional Tensor Networks, we show that Neural-Network Quantum States and their String-Bond States extension can describe a lattice Fractional Quantum Hall state exactly. In addition, we provide numerical evidence that Neural-Network Quantum States can approximate a chiral spin liquid with better accuracy than Entangled Plaquette States and local String-Bond States. Our results demonstrate the efficiency of neural networks to describe complex quantum wave functions and pave the way towards the use of String-Bond States as a tool in more traditional machine-learning applications.

Entanglement entropy of integer Quantum Hall states

We compute the entanglement entropy, in the real space, of the ground state of the integer Quantum Hall states for three different domains embedded in the cylinder, the disk and the sphere. We establish the validity of the area law with a vanishing value of the topological entanglement entropy. The entropy per unit length of the perimeter depends on the filling fraction, but it is independent of the geometry.

Composite fermion model for entanglement spectrum of fractional quantum Hall states

We show that the entanglement spectrum associated with a certain class of strongly correlated many-body states --- the wave functions proposed by Laughlin and Jain to describe the fractional quantum Hall effect --- can be very well described in terms of a simple model of non-interacting (or weakly interacting) composite fermions.

Quasielectrons as inverse quasiholes in lattice fractional quantum Hall models

From an experimental point of view, quasielectrons and quasiholes play very similar roles in the fractional quantum Hall effect. Nevertheless, the theoretical description of quasielectrons is known to be much harder than the one of quasiholes. The problem is that one obtains a singularity in the wavefunction if one tries to naively construct the quasielectron as the inverse of the quasihole. Here, we demonstrate that the same problem does not arise in lattice fractional quantum Hall models. This result allows us to make detailed investigations of the properties of quasielectrons, including their braiding statistics and density distribution on lattices on the plane and on the torus. We show that some of the states considered have high overlap with certain fractional Chern insulator states. We also derive few-body Hamiltonians, for which various states containing quasielectrons are exact ground states.

Continuum limit of lattice models with Laughlin-like ground states containing quasiholes

There has been a significant interest in the last years in finding fractional quantum Hall physics in lattice models, but it is not always clear how these models connect to the corresponding models in continuum systems. Here we introduce a family of models that is able to interpolate between a recently proposed set of lattice models with Laughlin-like ground states constructed from conformal field theory and models with ground states that are practically the usual bosonic/fermionic Laughlin states in the continuum. Both the ground state and the Hamiltonian are known analytically, and we find that the Hamiltonian in the continuum limit does not coincide with the usual delta interaction Hamiltonian for the Laughlin states. We introduce quasiholes into the models and show analytically that their braiding properties are as expected if the quasiholes are screened. We demonstrate screening numerically for the 1/3 Laughlin model and find that the quasiholes are slightly smaller in the continuum than in the lattice. Finally, we compute the effective magnetic field felt by the quasiholes and show that it is close to uniform when approaching the continuum limit. The techniques presented here to interpolate between the lattice and the continuum can also be applied to other fractional quantum Hall states that are constructed from conformal field theory.

Performance of thermoacoustic device and its thermal contact to a source

An important application of a thermoacoustic prime mover is in the conversion of heat to electricity when coupled to a sound to electricity converter. In order to achieve maximum sound output, the thermal coupling of the heat source is critical. This was studied here by using (i) a constant heat flow heat source and (ii) a constant temperature difference heat source. As in an electric system where the higher efficiency of power delivery is for a constant voltage source, maximum heat is delivered to the acoustic device from a constant temperature difference heat source. This was investigated on a 1.94 kHz thermoacoustic engine coupled to an acoustic cavity. A shutter located inside the cavity made it possible to have sound on and sound off. In the constant heat flow approach, the shutter technique gave a direct value and measure of heat which was converted to sound. The constant temperature difference approach provided the most heat input for maximum sound output. The temperature profile of cold heat excha...