THz photometers for solar flare observations from space

The search for the still unrevealed spectral shape of the mysterious THz solar flare emissions is one of the current most challenging research issues. The concept, fabrication and performance of a double THz photometer system, named SOLAR-T, is presented. Its innovative optical setup allows observations of the full solar disk and the detection of small burst transients at the same time. The detecting system was constructed to observe solar flare THz emissions on board of stratospheric balloons. The system has been integrated to data acquisition and telemetry modules for this application. SOLAR-T uses two Golay cell detectors preceded by low-pass filters made of rough surface primary mirrors and membranes, 3 and 7 THz band-pass filters, and choppers. Its photometers can detect small solar bursts (tens of solar flux units) with sub second time resolution. Tests have been conducted to confirm the entire system performance, on ambient and low pressure and temperature conditions. An artificial Sun setup was developed to simulate performance on actual observations. The experiment is planned to be on board of two long-duration stratospheric balloon flights over Antarctica and Russia in 2014–2016.     

Measuring species richness on sandy beach transects: extrapolative estimators and their implications for sampling effort

Species richness is a measure that is fundamental to many studies in ecology, and it is particularly important on sandy beaches, where it underlies patterns described by the broadly accepted swash exclusion hypothesis. However, its estimation in practice is problematic. This has led ecologists in other fields to adopt extrapolative estimators of species richness, which project the total number of species present in a habitat by adjusting upward the number of species observed by an amount related to the number of rare species encountered in the samples. In so doing, the species richness can be estimated, with confidence intervals, at any level of sampling effort. Despite the availability and advantages of these methods, beach ecologists have continued to use the observed species richness as a point estimate of biodiversity for beaches. Here, we employ a Monte Carlo resampling approach over a range of routine transect designs used to sample sandy beaches, and evaluate the performance of seven non-parametric extrapolative estimators for species richness relative to that of the more conventionally used observed species richness. We find that the first-order Jackknife estimator (Jack 1) is the least biased, most accurate and most consistent across sites. Employing this estimator would allow accurate estimation of species richness on short (tens of metres) stretches of beach without exceeding the acceptable levels of sampling effort (4–5 m²). Spreading this effort evenly over three across-shore transects, each with a minimum of 13 equally spaced levels seems appropriately efficient. Although a greater number of research studies is required to ascertain the generality of these results beyond the beaches we sampled, we tentatively recommend the application of our results in biodiversity surveys on sandy beaches.     

Experimental testing, numerical modelling and seismic strengthening of traditional stone masonry: comprehensive study of a real Azorian pier

Stone masonry is one of the oldest building techniques used worldwide and it is known to exhibit poor behaviour under seismic excitations. In this context, this work aims at assessing the in-plane behaviour of an existing double-leaf stone masonry pier by experimental testing. Additionally, a detailed 3D finite element numerical analysis based on micro-modelling of the original pier is presented (fully describing the geometry and division of each individual elements, namely infill, blocks and joints) aiming at simulating the experimental test results. This numerical strategy can be seen as an alternative way of analysing this type of constructions, particularly useful for laboratory studies, and suitable for the calibration of simplified numerical models. As part of a wider research activity, this work is further complemented with the presentation of an effective retrofit/strengthening technique (reinforced connected plaster) to achieve a significant improvement of its in-plane cyclic response which is experimentally verified in the results presented herein.     

Molecular and distribution data on the poorly known,elusive, cave mysid Harmelinella mariannae (Crustacea: Mysida)

Mediterranean underwater marine caves harbour abundant populations of several species of mysids that are increasingly used as biological models in ecological and evolutionary studies. One exception is the species Harmelinella mariannae, described in 1989 and then hardly ever again reported in the literature. We here provide the first data on the distribution of this poorly known taxon that, contrary to expectations for a rare brooding cave dweller, we now report from Madeira Island in the nearby Atlantic, to the easternmost parts of the Mediterranean. Brief behavioural observations are added, particularly its atypical solitary habits and its feeding behaviour as a high trophic level carnivore. Molecular characterization of the different specimens captured provided three sorts of information. Mitochondrial COI and 16S haplotypes suggest different colonization waves in the Mediterranean, with one group in the Eastern Basin, two in the Marseille region in the NW part of this sea, and another group with a very wide extension from Madeira to Liguria and Malta. Mitochondrial data also support that one of the groups in Marseille might have diverged as a cryptic species of Harmelinella. 18S rRNA gene displays a single common sequence to all specimens from the four groups, and seems to confirm the original proposed placement of this taxon within the subfamily Heteromysinae, not Leptomysinae.     

A western boundary current east of New Caledonia: Observed characteristics

Waters from the South Equatorial Current (SEC), the northern branch of the South Pacific subtropical gyre, are a major supply of heat to the equatorial warm pool, and have an important contribution to climate variability and ENSO which motivated the Southwest Pacific Ocean and Climate Experiment (SPICE, CLIVAR/WCRP). Initially a broad westward current extending from the equator to 30°S, the SEC splits upon arriving at the major islands and archipelagoes of Fiji (18°S, 180°E), Vanuatu (16°S, 168°E), and New Caledonia (22°S, 165°E), resulting in a complex system of western boundary currents and zonal jets that feed the Coral and Solomon Seas. We focus here on the formation of one specific jet feeding the Coral Sea, the North Caledonian Jet (NCJ). Using a combination of recent oceanographic cruises, we describe the ocean circulation to the northeast of New Caledonia, where the SEC forms a western boundary current that ultimately becomes the NCJ. This current, which we document for the first time and propose to refer to as the East Caledonian Current (ECC), has its core located 10-100 km off the east coast of New Caledonia, and extends vertically to at least 1000 m depth. Water mass properties show continuous westward transports through the ECC, from the SEC to the NCJ in both the South Pacific Tropical Waters in the thermocline and Antarctic Intermediate Waters near 700 m depth. The ECC extends about 100 km horizontally; its average 0-1000 m transport was estimated at 14.5±3 Sv off the north tip of the New Caledonian reef, with a maximum of 20 Sv in May 2010. South of that the upstream branch of the ECC east of the Loyalty is close to 8 Sv suggesting an important additional contribution from central Pacific waters carried by the SEC at 16°S and diverted to our region through the western boundary current system east of Vanuatu.     

Electron-impact rotational excitation of linear molecular ions

Molecular R -matrix calculations are performed to give rotational excitation rates for electron collisions with linear molecular ions. Results are presented for CO⁺, HCO⁺, NO⁺ and H₂⁺ up to electron temperatures of 10 000 K. De-excitation rates and critical electron densities are also given. It is shown that the widely used Coulomb–Born approximation is valid for Δ j =1 transitions when the molecular ion has a dipole greater than about 2D, but otherwise is not reliable for studying electron-impact rotational excitation. In particular, transitions with Δ j >1 are found to have appreciable rates and are found to be entirely dominated by short-range effects.     

On the co-orbital motion in the planar restricted three-body problem: the quasi-satellite motion revisited

In the framework of the planar and circular restricted three-body problem, we consider an asteroid that orbits the Sun in quasi-satellite motion with a planet. A quasi-satellite trajectory is a heliocentric orbit in co-orbital resonance with the planet, characterized by a nonzero eccentricity and a resonant angle that librates around zero. Likewise, in the rotating frame with the planet, it describes the same trajectory as the one of a retrograde satellite even though the planet acts as a perturbator. In the last few years, the discoveries of asteroids in this type of motion made the term “quasi-satellite” more and more present in the literature. However, some authors rather use the term “retrograde satellite” when referring to this kind of motion in the studies of the restricted problem in the rotating frame. In this paper, we intend to clarify the terminology to use, in order to bridge the gap between the perturbative co-orbital point of view and the more general approach in the rotating frame. Through a numerical exploration of the co-orbital phase space, we describe the quasi-satellite domain and highlight that it is not reachable by low eccentricities by averaging process. We will show that the quasi-satellite domain is effectively included in the domain of the retrograde satellites and neatly defined in terms of frequencies. Eventually, we highlight a remarkable high eccentric quasi-satellite orbit corresponding to a frozen ellipse in the heliocentric frame. We extend this result to the eccentric case (planet on an eccentric motion) and show that two families of frozen ellipses originate from this remarkable orbit.     

On the co-orbital motion of two planets in quasi-circular orbits

We develop an analytical Hamiltonian formalism adapted to the study of the motion of two planets in co-orbital resonance. The Hamiltonian, averaged over one of the planetary mean longitudes, is expanded in power series of eccentricities and inclinations. The model, which is valid in the entire co-orbital region, possesses an integrable approximation modeling the planar and quasi-circular motions. First, focusing on the fixed points of this approximation, we highlight relations linking the eigenvectors of the associated linearized differential system and the existence of certain remarkable orbits like the elliptic Eulerian Lagrangian configurations, the anti-Lagrange (Giuppone et al. in MNRAS 407:390–398, 2010) orbits and some second sort orbits discovered by Poincaré. Then, the variational equation is studied in the vicinity of any quasi-circular periodic solution. The fundamental frequencies of the trajectory are deduced and possible occurrence of low order resonances are discussed. Finally, with the help of the construction of a Birkhoff normal form, we prove that the elliptic Lagrangian equilateral configurations and the anti-Lagrange orbits bifurcate from the same fixed point $L_4$ L 4 .