Replicate Periodic Windows in the Parameter Space of Driven Oscillators

In the bi-dimensional parameter space of driven oscillators, shrimp-shaped periodic windows are immersed in chaotic regions. For two of these oscillators, namely, Duffing and Josephson junction, we show that a weak harmonic perturbation replicates these periodic windows giving rise to parameter regions correspondent to periodic orbits. The new windows are composed of parameters whose periodic orbits have periodicity and pattern similar to stable and unstable periodic orbits already existent for the unperturbed oscillator. These features indicate that the reported replicate periodic windows are associated with chaos control of the considered oscillators

NEOTROPICAL XENARTHRANS: a data set of occurrence of xenarthran species in the Neotropics

Xenarthrans – anteaters, sloths, and armadillos – have essential functions for ecosystem maintenance, such as insect control and nutrient cycling, playing key roles as ecosystem engineers. Because of habitat loss and fragmentation, hunting pressure, and conflicts with 24 domestic dogs, these species have been threatened locally, regionally, or even across their full distribution ranges. The Neotropics harbor 21 species of armadillos, ten anteaters, and six sloths. Our dataset includes the families Chlamyphoridae (13), Dasypodidae (7), Myrmecophagidae (3), Bradypodidae (4), and Megalonychidae (2). We have no occurrence data on Dasypus pilosus (Dasypodidae). Regarding Cyclopedidae, until recently, only one species was recognized, but new genetic studies have revealed that the group is represented by seven species. In this data-paper, we compiled a total of 42,528 records of 31 species, represented by occurrence and quantitative data, totaling 24,847 unique georeferenced records. The geographic range is from the south of the USA, Mexico, and Caribbean countries at the northern portion of the Neotropics, to its austral distribution in Argentina, Paraguay, Chile, and Uruguay. Regarding anteaters, Myrmecophaga tridactyla has the most records (n=5,941), and Cyclopes sp. has the fewest (n=240). The armadillo species with the most data is Dasypus novemcinctus (n=11,588), and the least recorded for Calyptophractus retusus (n=33). With regards to sloth species, Bradypus variegatus has the most records (n=962), and Bradypus pygmaeus has the fewest (n=12). Our main objective with Neotropical Xenarthrans is to make occurrence and quantitative data available to facilitate more ecological research, particularly if we integrate the xenarthran data with other datasets of Neotropical Series which will become available very soon (i.e. Neotropical Carnivores, Neotropical Invasive Mammals, and Neotropical Hunters and Dogs). Therefore, studies on trophic cascades, hunting pressure, habitat loss, fragmentation effects, species invasion, and climate change effects will be possible with the Neotropical Xenarthrans dataset

New pressure-induced phase transitions of l-threonine crystal: A Raman spectroscopic study

International audienceL-threonine crystal was studied by Raman spectroscopy under pressure in the spectral range from 50 to3300 cm1. The pressure range of a previous study has been extended from 4 to 27.0 GPa. Modificationsin the whole spectrum give us evidence of three structural phase transitions undergone by this aminoacid as well as two conformational change. The classification of the vibrational modes and the behaviorof their frequencies as a function of the pressure are presented

IN-DEPTH MODIFICATIONS OF IMPLANTED AMORPHOUS-CARBON FILMS

Amorphous carbon films (a-C:H) and nitrogen incorporated carbon films [a-C:H(N)] deposited by a self-bias glow discharge have been implanted with 70 keV nitrogen ions at fluences of 0.6, 1 and 2 x 10(17) N/cm(2) The in-depth modifications caused by ion implantation were determined by means of nuclear techniques, such as Rutherford Backscattering Spectrometry (RBS), Nuclear Reaction Analysis (NRA) and Elastic Recoil Detection Analysis (ERDA), as well as by Auger Electron Spectroscopy (AES) and Raman scattering. ERDA profiles show that nitrogen implantation causes hydrogen depletion, the amount of which depends on the film composition and on the ion fluence. In a-C:H(N) films nitrogen loss was also measured. The induced structural modifications in both a-C:H and a-C:H(N) films were followed by both AES, using factor analysis, and microprobe Raman spectroscopy. They turn out to be related to the energy deposited by the incident ions. Our results indicate that the ion-beam bombardment causes in both a-C:H and a-C:H (N) films an increase of either the degree of disorder or the ratio between sp(2)/sp(3) bonds across the hydrogen-depleted layer, which depends on the ion fluence