Observing different phases for the dynamics of entanglement in an ion trap

The evolution of the entanglement between two oscillators coupled to a common thermal environment is non-trivial. The long time limit has three qualitatively different behaviors (phases) depending on parameters such as the temperature of the bath ({\em Phys. Rev. Lett.} \textbf{100}, 220401). The phases include cases with non-vanishing long-term entanglement, others with a final disentangled state, and situations displaying an infinite sequence of events of disappearance and revival of entanglement. We describe an experiment to realize these different scenarios in an ion trap. The motional degrees of freedom of two ions are used to simulate the system while the coupling to an extra (central) ion, which is continuously laser cooled, is the gateway to a decohering reservoir. The scheme proposed allows for the observation and control of motional entanglement dynamics, and is an example of a class of simulations of quantum open systems in the non-Markovian regime.Comment: 5 pages, 5 figure

Decoherence induced by a dynamic spin environment (II): Disentanglement by local system-environment interactions

This article studies the decoherence induced on a system of two qubits by local interactions with a spin chain with nontrivial internal dynamics (governed by an XY Hamiltonian). Special attention is payed to the transition between two limits: one in which both qubits interact with the same site of the chain and another one where they interact with distant sites. The two cases exhibit different behaviours in the weak and strong coupling regimes: when the coupling is weak it is found that decoherence tends to decrease with distance, while for strong coupling the result is the opposite. Also, in the weak coupling case, the long distance limit is rapidly reached, while for strong coupling there is clear evidence of an expected effect: environment-induced interactions between the qubits of the system. A consequence of this is the appearance of quasiperiodic events that can be interpreted as ``sudden deaths'' and ``sudden revivals'' of the entanglement between the qubits, with a time scale related to the distance between them.Comment: 10 pages, 9 figure

The QUEST RR Lyrae Survey: III. The Low Galactic Latitude Catalogue

We present results for the QUEST RR Lyrae Survey at low galactic latitude, conducted entirely with observations obtained with the QUEST mosaic camera and the 1.0/1.5m J\"urgen Stock Schmidt telescope at the National Observatory of Venezuela. The survey spans an area of 476 sq. deg on the sky, with multi-epoch observations in the V, R and I photometric bands for 6.5x10^6 stars in the galactic latitude range 30<= b(deg) <=+25, in a direction close to the Galactic Anticenter 190<= l(deg)<= 230. The variability survey has a typical number of 30 observations per object in V and I and ~25 in R, with up to ~120-150 epochs in V and I and up to ~100 in R in the best sampled regions. The completeness magnitudes of the survey are V=R=18.5 mag, and I=18.0 mag. We identified 211 RR Lyrae stars, 160 bona fide stars of type ab and 51 candidates of type c, ours being the first deep RR Lyrae survey conducted at low galactic latitude.The completeness of the RR Lyrae survey was estimated in >95 per cent and ~85 per cent for RRab and RRc stars respectively. Photometric metallicities were computed based on the light curves and individual extinctions calculated from minimum light colours for each RRab star. Distances were obtained with typical errors ~7 per cent. The RR Lyrae survey simultaneously spans a large range of heliocentric distances 0.5<= R_hel(kpc)<=40 and heights above the plane -15<=z(kpc)<=+20, with well known completeness across the survey area, making it an ideal set for studying the struc ture of the Galactic thick disk.Comment: 24 pages, 17 figures, 8 tables. Accepted for publication in MNRA

Long-term changes in phytoplankton phenology and community structure in the Bahía Blanca Estuary, Argentina

The phytoplankton of the Bahía Blanca Estuary, Argentina, has been surveyed since 1978. Chlorophyll a, phytoplankton abundance, species composition and physico-chemical variables have been fortnightly recorded. From 1978 to 2002, a single winter–early spring diatom bloom has dominated the main pattern of phytoplankton interannual variability. Such pattern showed noticeable changes since 2006: the absence of the typical winter bloom and changes in phenology, together with the replacement of the dominant blooming species, i.e. Thalassiosira curviseriata, and the appearance of different blooming species, i.e. Cyclotella sp. and Thalassiosira minima. The new pattern showed relatively short-lived diatom blooms that spread throughout the year. In addition, shifts in the phytoplankton size structure toward small-sized diatoms, including the replacement of relatively large Thalassiosira spp. by small Cyclotella species and Chaetoceros species have been noticed. The changes in the phenology and composition of the phytoplankton are mainly attributed to warmer winters and the extremely dry weather conditions evidenced in recent years in the Bahía Blanca area. Changing climate has modified the hydrological features in the inner part of the estuary (i.e. higher temperatures and salinities) and potentially triggered the reorganization of the phytoplankton community. This long-term study provides evidence on species-specific and structural changes at the bottom of the pelagic food web likely related to the recent hydroclimatic conditions in a temperature estuary of the southwestern Atlantic

Classicality in discrete Wigner functions

Gibbons et al. [Phys. Rev. A 70, 062101(2004)] have recently defined a class of discrete Wigner functions W to represent quantum states in a Hilbert space with finite dimension. We show that the only pure states having non-negative W for all such functions are stabilizer states, as conjectured by one of us [Phys. Rev. A 71, 042302 (2005)]. We also show that the unitaries preserving non-negativity of W for all definitions of W form a subgroup of the Clifford group. This means pure states with non-negative W and their associated unitary dynamics are classical in the sense of admitting an efficient classical simulation scheme using the stabilizer formalism.Comment: 10 pages, 1 figur

Assessing Spanish-Speaking University Students’ Info-Competencies with iSkills, SAILS, and an In-House Instrument: Challenges and Benefits

In its ongoing assessment of information literacy competencies (ILC), CETYS Universidad first developed an in-house instrument and then applied the standardized tests, SAILS and iSkills. This paper analyzes the design of these instruments as well as data gathered from their implementation. This comparison aids in finding similarities in the ILC they measure, describe how they measure them, and study their differences. The objectives of this analysis are to describe the evolution of the Institution’s ILC assessment over the past four years while providing the basis for making an evidence-based decision about improving the in-house instrument and pushing to develop a Spanish-language multi-institutional tool, and/or the continued use of international instruments

Assessing Spanish-Speaking University Students’ Info-Competencies with iSkills, SAILS, and an In-House Instrument: Challenges and Benefits

In its ongoing assessment of information literacy competencies (ILC), CETYS Universidad first developed an in-house instrument and then applied the standardized tests, SAILS and iSkills. This paper analyzes the design of these instruments as well as data gathered from their implementation. This comparison aids in finding similarities in the ILC they measure, describe how they measure them, and study their differences. The objectives of this analysis are to describe the evolution of the Institution’s ILC assessment over the past four years while providing the basis for making an evidence-based decision about improving the in-house instrument and pushing to develop a Spanish-language multi-institutional tool, and/or the continued use of international instruments

Related factors to human toxocariasis in a rural community of Argentina

The objective of this study was to evaluate the relationship between toxocariasis frequency and demographic, environmental, sanitary variables, eosinophylia, and other intestinal parasites in a rural population of Argentina. Serological examination of 100 individuals was carried out by using ELISA technique for the detection of antitoxocara antibodies. Eosinophiles in peripheral blood, presence of intestinal parasites, and demographic, environmental, and socio-cultural data were evaluated. Eighty-one feces samples of dogs belonging to the studied people were analyzed to detect eggs of Toxocara canis. Thirty of them were from 30 dogs and 51 were pools from dog feces. Samples of dirt from around the homes (n: 47) and from public park (n: 4) were taken. To determine the associations, the X2 and Fisher tests were used. The seroprevalence was 23%. Eosinophilia in peripheral blood was detected in 86.95% seropositive individuals and in 37.66% seronegative individuals (p < 0.001, OR = 11.03). Of the 23 people with positive serology, 69.56% had at least one intestinal parasite. All individuals with positive serology had dogs in their homes. Among the dog owners there was a significant association between the presence of anti-toxocara antibodies and home flooding. Eggs of T. canis were detected in the feces of 5/81 dogs and three of these dogs belonged to individuals with positive serology. Eggs of Toxocara spp. were found in 41.17% of the dirt samples, eight of which came from the area surrounding the homes of individuals with positive serology (p = 0.032; OR = 4.36). Taking into account all the variables influencing the frequency of toxocariasis in this population, the implementation of Public Health programs specifically focused on anti-parasitic treatment of dogs is recommended

Highly dispersed copper oxide on silica: Towards an efficient catalyst for continuous glycerol dehydration to acetol

[EN] In most current processes aimed at producing biodiesel glycerol is still a co-product, and its valorisation is essential for the biorefinery. This work relies on previous results showing the dependence of the selective dehydration of glycerol to acetol (hydroxyacetone) on achieving a moderate acidity and the redox functionality of copper to complete the chemical process. In this sense, this reaction was studied using CuO supported on silica. Different silicas and copper incorporation methodologies were investigated to develop the best CuO/SiO2 material. Interestingly, these CuO-based materials developed acidity and became more active when increasing the copper oxide dispersion, thereby going from poorly to intensely effective to dehydrate glycerol selectively to acetol. Catalysts were characterised by different techniques (i.e., ICP, N2 adsorption, XRD, TPR, HR-TEM, etc.) to explain the differences observed in catalytic activity and acetol yield based on their physicochemical properties.Financial support by Spanish Government (CTQ-2015-67592, PGC2018-097277-B-I00 and SEV-2016-0683) is gratefully acknowl-edged. J.M. thanks Spanish Government (CTQ-2015-67592) for the Ph.D. fellowship. Authors also thank Miriam Parreno Romero and the Electron Microscopy Service of Universitat Polite`cnica de València for their support.Mazarío-Santa-Pau, J.; Cecilia, JA.; Rodríguez-Castellón, E.; Domine, ME. (2023). Highly dispersed copper oxide on silica: Towards an efficient catalyst for continuous glycerol dehydration to acetol. Applied Catalysis A General. 652. https://doi.org/10.1016/j.apcata.2023.11902965