Student Exchange in Japan: Why and How to Provide Engineering Students with an International Experience

In the last years, to improve the performance of prediction of radioactive contamination, an increasing number of studies have explored and exploited the potentials of geostatistical methods. However, traditional methods like kriging and cokriging are optimal only in the case in which the data may be assumed Gaussian and do not properly cope with data measurements that are discrete, nonnegative or show some degree of skewness, as in many environmental applications concerned with radioactivity measurements. To deal with geostatistical skewed data, we consider a model-based approach in which measurements are modeled with the help of a latent Gaussian structure and some recent classes of skewed distributions extending the normal one. For our model we investigate the implied spatial autocorrelation structure and the marginal distributions of the observable variables. In particular we show that all finite-dimensional marginal distributions of the observable variables belong to the family of the unified skew-normal distribution. Estimation of some of the unknown parameters of the model can be carried out by employing a Monte Carlo expectation maximization procedure, whereas predictions of both latent and observed (at unsampled sites) variables, can be supplied by Markov chain Monte Carlo algorithms

Capture Velocity for a Magneto-Optical Trap in a Broad Range of Light Intensity

In a recent paper, we have used the dark-spot Zeeman tuned slowing technique [Phys. Rev. A 62, 013404-1, (2000)] to measure the capture velocity as a function of laser intensity for a sodium magneto optical trap. Due to technical limitation we explored only the low light intensity regime, from 0 to 27 mW/cm^2. Now we complement that work measuring the capture velocity in a broader range of light intensities (from 0 to 400 mW/cm^2). New features, observed in this range, are important to understant the escape velocity behavior, which has been intensively used in the interpretation of cold collisions. In particular, we show in this brief report that the capture velocity has a maximum as function of the trap laser intensity, which would imply a minimum in the trap loss rates.Comment: 2 pages, 2 figure

Magnetic Field Tomography

Neutral atoms may be trapped via the interaction of their magnetic dipole moment with magnetic field gradients. One of the possible schemes is the cloverleaf trap. It is often desirable to have at hand a fast and precise technique for measuring the magnetic field distribution. We introduce a novel diagnostic tool for instantaneous imaging the equipotential lines of a magnetic field within a region of space (the vacuum recipient) that is not accessible to massive probes. Our technique is based on spatially resolved observation of the fluorescence emitted by a hot beam of sodium atoms crossing a thin slice of resonant laser light within the magnetic field region to be investigated. The inhomogeneous magnetic field spatially modulates the resonance condition between the Zeeman-shifted hyperfine sublevels and the laser light and therefore the amount of scattered photons. We demonstrate this technique by mapping the field of our cloverleaf trap in three dimensions under various conditions.Comment: 8 pages, 8 figure

Emergence of turbulence in an oscillating Bose-Einstein condensate

We report on the experimental observation of vortices tangle in an atomic BEC of Rb-87 atoms when an external oscillatory perturbation is introduced in the trap. The vortices tangle configuration is a signature of the presence of a turbulent regime in the cloud. We also show that this turbulent cloud has suppression of the aspect ratio inversion typically observed in quantum degenerate bosonic gases during free expansion. Instead, the cloud expands keeping the ratio between their axis constant. Turbulence in atomic superfluids may constitute an alternative system to investigate decay mechanisms as well as to test fundamental theoretical aspects in this field.Comment: accepted for Phys. Rev. Let

The interconnection of hierarchy, affiliative behaviours, and social play shapes social dynamics in Maremmana beef cattle

Dominance hierarchies can be interconnected with behaviours that are essential to manage social living, such as affiliative behaviours and social play, whose importance can already emerge in the early phases of life. Here, we carried out an observational study (all occurrences sampling) to investigate the possible interconnection between these three behavioural categories in a group of Maremmana beef cattle (n = 44, 6–21 months of age) in an extensive breeding system. We found that a clearly linear hierarchy is present in the group, and that the age of the animals positively correlated with their hierarchical ranks. Affiliative behaviours were directed up to the hierarchy: dominants received more affiliative behaviours and subordinates were generally starting the sessions, suggesting that affiliative behaviours may be used by subordinates to bond with dominants for possibly gaining some benefits. Social play mainly consisted of play fighting and dominant subjects played with the highest frequency. However, playful modality was independent from playmates’ relative rank position, with longer-lasting sessions being characterized by unbalanced and unreciprocated patterns. This indicates that play fighting in cattle has a competitive rather than cooperative nature and that it may be used as physical training to develop competitive skills in all groupmates. When play fighting was punctuated by affiliative behaviours, the playful sessions lasted longer. In this view, affiliative behaviours can have a communicative value useful in downgrading the competition emerging during play fighting. In conclusion, under naturalistic conditions young animals of beef cattle express all the behavioural repertoire typical of adulthood and their agonistic, affiliative, and playful behaviours are strongly interconnected in shaping social dynamics. Thus, our study suggests that extensive farming conditions are ideal to study the behavioural strategies domestic animals enact to form cohesive social groups. Such information is needed to enhance management and welfare of domestic ungulates

Tumor cellular and microenvironmental cues controlling invadopodia formation

During the metastatic progression, invading cells might achieve degradation and subsequent invasion into the extracellular matrix (ECM) and the underlying vasculature using invadopodia, F-actin-based and force-supporting protrusive membrane structures, operating focalized proteolysis. Their formation is a dynamic process requiring the combined and synergistic activity of ECM-modifying proteins with cellular receptors, and the interplay with factors from the tumor microenvironment (TME). Significant advances have been made in understanding how invadopodia are assembled and how they progress in degradative protrusions, as well as their disassembly, and the cooperation between cellular signals and ECM conditions governing invadopodia formation and activity, holding promise to translation into the identification of molecular targets for therapeutic interventions. These findings have revealed the existence of biochemical and mechanical interactions not only between the actin cores of invadopodia and specific intracellular structures, including the cell nucleus, the microtubular network, and vesicular trafficking players, but also with elements of the TME, such as stromal cells, ECM components, mechanical forces, and metabolic conditions. These interactions reflect the complexity and intricate regulation of invadopodia and suggest that many aspects of their formation and function remain to be determined. In this review, we will provide a brief description of invadopodia and tackle the most recent findings on their regulation by cellular signaling as well as by inputs from the TME. The identification and interplay between these inputs will offer a deeper mechanistic understanding of cell invasion during the metastatic process and will help the development of more effective therapeutic strategies

Photoassociative ionization of Na inside a storage ring

Motivated by recent interest in low dimensional arrays of atoms, we experimentally investigated the way cold collisional processes are affected by the geometry of the considered atomic sample. More specifically, we studied the case of photoassociative ionization (PAI) both in a storage ring where collision is more unidirectional in character and in a trap with clear undefinition of collision axis. First, creating a ring shaped trap (atomotron) we investigated two-color PAI dependence with intensity and polarization of a probing laser. The intensity dependence of the PAI rate was also measured in a magneto-optical trap presenting equivalent temperature and density conditions. Indeed, the results show that in the ring trap, the value of the PAI rate constant is much lower and does not show evidences of saturation, unlike in the case of the 3D-MOT. Cold atomic collisions in storage ring may represent new possibilities for study.Comment: 5 pages, 5 figures; Accepted by Optics Communicatio