Rare earth based nanostructured materials: Synthesis, functionalization, properties and bioimaging and biosensing applications

Rare earth based nanostructures constitute a type of functional materials widely used and studied in the recent literature. The purpose of this review is to provide a general and comprehensive overview of the current state of the art, with special focus on the commonly employed synthesis methods and functionalization strategies of rare earth based nanoparticles and on their different bioimaging and biosensing applications. The luminescent (including downconversion, upconversion and permanent luminescence) and magnetic properties of rare earth based nanoparticles, as well as their ability to absorb X-rays, will also be explained and connected with their luminescent, magnetic resonance and X-ray computed tomography bioimaging applications, respectively. This review is not only restricted to nanoparticles, and recent advances reported for in other nanostructures containing rare earths, such as metal organic frameworks and lanthanide complexes conjugated with biological structures, will also be commented on.European Union 267226Ministerio de Economía y Competitividad MAT2014-54852-

Cannibalism in an Introduced Population of Cyclura nubila nubila on Isla Magueyes, Puerto Rico

In the mid-1960s, Cuban Iguanas (Cyclura nubila nubila) were introduced to Isla Magueyes, a 7.2-ha islet in southwestern Puerto Rico (Rivero 1978). Anecdotal information affirms that this population originated from a single pair of individuals

Upper bounds on the superfluid stiffness and superconducting TcT_c: Applications to twisted-bilayer graphene and ultra-cold Fermi gases

Understanding the material parameters that control the superconducting transition temperature $T_c$ is a problem of fundamental importance. In many novel superconductors, phase fluctuations determine $T_c$, rather than the collapse of the pairing amplitude. We derive rigorous upper bounds on the superfluid phase stiffness for multi-band systems, valid in any dimension. This in turn leads to an upper bound on $T_c$ in two dimensions (2D), which holds irrespective of pairing mechanism, interaction strength, or order-parameter symmetry. Our bound is particularly useful for the strongly correlated regime of low-density and narrow-band systems, where mean field theory fails. For a simple parabolic band in 2D with Fermi energy $E_F$, we find that $k_BT_c \leq E_F/8$, an exact result that has direct implications for the 2D BCS-BEC crossover in ultra-cold Fermi gases. Applying our multi-band bound to magic-angle twisted bilayer graphene (MA-TBG), we find that band structure results constrain the maximum $T_c$ to be close to the experimentally observed value. Finally, we discuss the question of deriving rigorous upper bounds on $T_c$ in 3D.Comment: Revised figures, includes estimates from another model of MA-TBG, published version of manuscrip

Survival, dispersal and reproduction of headstarted Mona Island iguanas, Cyclura cornuta stejnegeri

The endemic Mona Island Iguana, Cyclura cornuta stejnegeri, is considered endangered, and exhibits relatively low population numbers and reduced recruitment of juveniles to adults. A headstarting program was initiated in 1999 to increase the effective population number. Two groups of headstarted iguanas were released in April and August 2002, after reaching a target size. Most of the released iguanas have since been observed to be active and in good health. Two females bred in 2004, the first certain record of reproduction by headstarted Cyclura iguanas in the wild. Eight radiotracked individuals had large dispersal ranges, with mean Minimum Convex Polygon (MCP) of 10.7 ha (range 2.6-22.2 ha) and mean distances covered of 288 m (range 471-6396 m).We discuss the future development of the headstarting program for Mona Island iguanas

Positron annihilation analysis of nanopores and growth mechanism of oblique angle evaporated TiO2 and SiO2 thin films and multilayers

The nano-porosity embedded into the tilted and separated nanocolumns characteristic of the microstructure of evaporated thin films at oblique angles has been critically assessed by various variants of the positron annihilation spectroscopy. This technique represents a powerful tool for the analysis of porosity, defects and internal interfaces of materials, and has been applied to different as-deposited SiO and TiO thin films as well as SiO/TiO multilayers prepared by electron beam evaporation at 70° and 85° zenithal angles. It is shown that, under same deposition conditions, the concentration of internal nano-pores in SiO is higher than in TiO nanocolumns, while the situation is closer to this latter in TiO/SiO multilayers. These features have been compared with the predictions of a Monte Carlo simulation of the film growth and explained by considering the influence of the chemical composition on the growth mechanism and, ultimately, on the structure of the films

Evaluación de diferentes pruebas para el diagnóstico de H. Pylori.

Todos los métodos disponibles para el diagnóstico de H. pylori tienen diferencias en su sensibilidad y especificidad. El propósito de este estudio es determinar el índice de desempeño, sensibilidad, especificidad y valores predictivos de cuatro métodos invasivos, teniendo como técnica de referencia la definición de caso: cultivo positivo o la concordancia de por lo menos dos procesos de diagnósticos positivos

Conserving the Puerto Rican herpetofauna

With a total area of 8900 km2, Puerto Rico is the smallest of the Greater Antilles. It is divided in three physiographic regions or areas of relief: the mountainous interior, the karst region, and the coastal plains and valleys. The island comprises six ecological life zones: subtropical dry forest, subtropical moist forest, subtropical wet forest, subtropical rain forest, lower montane wet forest and lower montane rain forest. The herpetofauna of Puerto Rico consists of 25 species of amphibians (19 native, six introduced) and 56 species of reptiles (52 native, four introduced). The goal of this paper is to describe some of the present studies directed towards the conservation of Puerto Rican herpetofauna. Eleutherodactylus karlschmidti, E. jasperi and E. eneidae have not been seen or heard since 1976, 1981 and 1990, respectively, and are probably extinct. Since 2000, the potential causes of amphibian declines in Puerto Rico have been studied, and a synergistic interaction between climate change (increased dry periods) and disease (chytridiomycosis) have been proposed as an explanation for the patterns observed. Recovery efforts for Peltophryne lemur include a captivebreeding program, reintroductions island-wide educational outreach, protection and restoration of existing habitat, and the creation of new breeding ponds. Among reptiles, the first conservation efforts to protect Epicrates inornatus were limited to trying to halt collection and hunting. However, current strategies to preserve the boa include gathering basic biological information, habitat conservation, and educational outreach. Recent efforts for the conservation of Trachemys s. stejnegeri combine three research approaches to clarify the status of local populations: a mark-recapture-release study, field monitoring of reproductive activity (i.e., nocturnal patrolling to identify nesting activity), and field assessment of the potential impact of introduced species, particularly identification of predatory species and exotic turtles. Recovery initiatives for Cyclura stejnegeri include management of invasive mammals, a headstart program for hatchling iguanas, and the assessment of the etiology of a condition causing blindness in adult iguanas. A reforestation project aimed at recovering a local herpetofaunal assemblage after disturbances in a limestone valley in northern Puerto Rico is discussed. As population sizes of common colonizers such as Eleutherodactylus and Anolis increased, larger forest-interior and predatory species like Epicrates inornatus, Alsophis portoricensis and Anolis cuvieri followed. Finally, the Mona Island marine turtle monitoring program is discussed and compared to other similar programs in Puerto Rico. As these and other similar conservation efforts provide scientifically based management recommendations, we hope to succeed in conserving the diverse herpetofauna that characterizes Puerto Rico

Genetic Continuity in the Franco-Cantabrian Region: New Clues from Autochthonous Mitogenomes

Background: The Late Glacial Maximum (LGM),,20 thousand years ago (kya), is thought to have forced the people inhabiting vast areas of northern and central Europe to retreat to southern regions characterized by milder climatic conditions. Archaeological records indicate that Franco-Cantabria might have been the major source for the re-peopling of Europe at the beginning of the Holocene (11.5 kya). However, genetic evidence is still scarce and has been the focus of an intense debate. Methods/Principal Findings: Based on a survey of more than 345,000 partial control region sequences and the analysis of 53 mitochondrial DNA (mtDNA) genomes, we identified an mtDNA lineage, HV4a1a, which most likely arose in the Franco-Cantabrian area about 5.4 kya and remained confined to northern Iberia. Conclusions/Significance: The HV4a1a lineage and several of its younger branches reveal for the first time genetic continuity in this region and long-term episodes of isolation. This, in turn, could at least in part explain the unique linguistic and cultural features of the Basque region

Origin of the large dispersion of magnetic properties in nanostructured oxides: FexO/Fe3O4 nanoparticles as a case study

The intimate relationship in transition-metal oxides between stoichiometry and physiochemical properties makes them appealing as tunable materials. These features become exacerbated when dealing with nanostructures. However, due to the complexity of nanoscale materials, establishing a distinct relationship between structure-morphology and functionalities is often complicated. In this regard, in the FexO/Fe3O4 system a largely unexplained broad dispersion of magnetic properties has been observed. Here we show, thanks to a comprehensive multi-technique approach, a clear correlation between magneto-structural properties in large (45 nm) and small (9 nm) FexO/Fe3O4 core/shell nanoparticles that can explain the spread of magnetic behaviors. The results reveal that while the FexO core in the large nanoparticles is antiferromagnetic and has bulk-like stoichiometry and unit-cell parameters, the FexO core in the small particles is highly non-stoichiometric and strained, displaying no significant antiferromagnetism. These results highlight the importance of ample characterization to fully understand the properties of nanostructured metal oxide