Geometric phases and criticality in spin systems

A general formalism of the relation between geometric phases produced by circularly evolving interacting spin systems and their criticality behavior is presented. This opens up the way for the use of geometric phases as a tool to study regions of criticality without having to undergo a quantum phase transition. As a concrete example a spin-1/2 chain with XY interactions is presented and the corresponding geometric phases are analyzed. The generalization of these results to the case of an arbitrary spin system provides an explanation for the existence of such a relation.Comment: 12 pages, 4 figure

Synthesis and characterization of nanometric titania coated on granular alumina for arsenic removal

The adsorption process is widely used for the treatment of drinking water sources containing high levels of arsenic. The choice of the adsorbent is crucial for the efficiency of the process. Very good performances were obtained in the past by activated alumina, while more recent studies have shown that also other media such as titanium oxide can provide high removal rates. In the present work, four types of adsorbents were tested for their removal capability of pentavalent arsenic from liquid solutions. Specifically, it was investigated if modifications of activated alumina by coating with titanium oxide nanoparticles or by reducing particle size might improve their performance. The adsorbents were firstly characterized by X-ray diffraction, BET specific area measurement and SEM analysis. Then, kinetics, equilibrium isotherm experiments were conducted in batch mode at fixed pH. All the tested adsorbents showed satisfactory arsenic removal, with the best performance obtained by the mesoporous gamma-alumina which had the lowest grain size. The titanium coating did not appear to significantly improve adsorption capacity. The kinetic data were best fitted by the pseudo-second order model, while both the Freundlich and the Langmuir equations well represented the adsorption isotherm data

Semiclassical limit of the entanglement in closed pure systems

We discuss the semiclassical limit of the entanglement for the class of closed pure systems. By means of analytical and numerical calculations we obtain two main results: (i) the short-time entanglement does not depend on Planck's constant and (ii) the long-time entanglement increases as more semiclassical regimes are attained. On one hand, this result is in contrast with the idea that the entanglement should be destroyed when the macroscopic limit is reached. On the other hand, it emphasizes the role played by decoherence in the process of emergence of the classical world. We also found that, for Gaussian initial states, the entanglement dynamics may be described by an entirely classical entropy in the semiclassical limit.Comment: 8 pages, 2 figures (accepted for publication in Phys. Rev. A

Evaluation of lens distortion errors in video-based motion analysis

In an effort to study lens distortion errors, a grid of points of known dimensions was constructed and videotaped using a standard and a wide-angle lens. Recorded images were played back on a VCR and stored on a personal computer. Using these stored images, two experiments were conducted. Errors were calculated as the difference in distance from the known coordinates of the points to the calculated coordinates. The purposes of this project were as follows: (1) to develop the methodology to evaluate errors introduced by lens distortion; (2) to quantify and compare errors introduced by use of both a 'standard' and a wide-angle lens; (3) to investigate techniques to minimize lens-induced errors; and (4) to determine the most effective use of calibration points when using a wide-angle lens with a significant amount of distortion. It was seen that when using a wide-angle lens, errors from lens distortion could be as high as 10 percent of the size of the entire field of view. Even with a standard lens, there was a small amount of lens distortion. It was also found that the choice of calibration points influenced the lens distortion error. By properly selecting the calibration points and avoidance of the outermost regions of a wide-angle lens, the error from lens distortion can be kept below approximately 0.5 percent with a standard lens and 1.5 percent with a wide-angle lens

Quantum linear mutual information and classical correlations in globally pure bipartite systems

We investigate the correlations of initially separable probability distributions in a globally pure bipartite system with two degrees of freedom for classical and quantum systems. A classical version of the quantum linear mutual information is introduced and the two quantities are compared for a system of oscillators coupled with both linear and non-linear interactions. The classical correlations help to understand how much of the quantum loss of purity are due to intrinsic quantum effects and how much is related to the probabilistic character of the initial states, a characteristic shared by both the classical and quantum pictures. Our examples show that, for initially localized Gaussian states, the classical statistical mutual linear entropy follows its quantum counterpart for short times. For non-Gaussian states the behavior of the classical and quantum measures of information are still qualitatively similar, although the fingerprints of the non-classical nature of the initial state can be observed in their different amplitudes of oscillation.Comment: (16 pages, 4 figures

Electron-phonon coupling in Ti/TiN MKIDs multilayer microresonator

Over the last few years there has been a growing interest toward the use of superconducting microwave microresonators operated in quasi-thermal equilibrium mode, especially applied to single particle detection. Indeed, previous devices designed and tested by our group with X-ray sources in the keV range evidenced that several issues arise from the attempt of detection through athermal quasiparticles produced within direct strikes of X-rays in the superconductor material of the resonator. In order to prevent issues related to quasiparticles self-recombination and to avoid exchange of athermal phonons with the substrate, our group focused on the development of thermal superconducting microresonators. In this configuration resonators composed of multilayer films of Ti/TiN sense the temperature of an absorbing material. To maximize the thermal response, low critical temperature films are preferable. By lowering the critical temperature, though, the maximum probing power bearable by the resonators decrease abruptly because of the weakening of the electron-phonon coupling. A proper compromise has to be found in order to avoid signal to noise ratio degradation. In this contribution we report the latest measurement of the electron-phonon coupling

Spectral and Spatial Dependence of Diffuse Optical Signals in Response to Peripheral Nerve Stimulation

Using non-invasive, near-infrared spectroscopy we have previously reported optical signals measured at or around peripheral nerves in response to their stimulation. Such optical signals featured amplitudes on the order of 0.1% and peaked about 100 ms after peripheral nerve stimulation in human subjects. Here, we report a study of the spatial and spectral dependence of the optical signals induced by stimulation of the human median and sural nerves, and observe that these optical signals are: (1) unlikely due to either dilation or constriction of blood vessels, (2) not associated with capillary bed hemoglobin, (3) likely due to blood vessel(s) displacement, and (4) unlikely due to fiber-skin optical coupling effects. We conclude that the most probable origin of the optical response to peripheral nerve stimulation is from displacement of blood vessels within the optically probed volume, as a result of muscle twitch in adjacent areas.National Institutes of Health (R01-NS059933); U.S. Army Medical Acquisition Activity (W81XWH-07-2-0011

Decoherence induced by a phase-damping reservoir

A phase damping reservoir composed by $N$-bosons coupled to a system of interest through a cross-Kerr interaction is proposed and its effects on quantum superpo sitions are investigated. By means of analytical calculations we show that: i-) the reservoir induces a Gaussian decay of quantum coherences, and ii-) the inher ent incommensurate character of the spectral distribution yields irreversibility . A state-independent decoherence time and a master equation are both derived an alytically. These results, which have been extended for the thermodynamic limit, show that nondissipative decoherence can be suitably contemplated within the EI D approach. Finally, it is shown that the same mechanism yielding decoherence ar e also responsible for inducing dynamical disentanglement.Comment: 8 pages, 3 figure

Immunopathogenesis of tuberculosis and novel mechanisms of vaccine activity

SummaryThe 4th Global Forum on TB Vaccines, convened in Shanghai, China, from 21 – 24 April 2015, brought together a wide and diverse community involved in tuberculosis vaccine research and development to discuss the current status of, and future directions for this critical effort. This paper summarizes the sessions on Immunopathogenesis of Tuberculosis, and Immunopathogenesis and Novel Mechanisms of Vaccine Activity. Summaries of all sessions from the 4th Global Forum are compiled in a special supplement of Tuberculosis