Les cumulus dans les Alpes valaisannes

Résumé Les cumulus de beau temps et les cumulonibus locaux ont leur base comprise entre 1500 et 4500 m. dans les Alpes valaisannes (Suisse); l'altitude moyenne s'établit à 3160 m. Variation diurne et saisonnière du niveau de condensation et spectre de fréquence.

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Summary In the Alps of the Valais (Switzerland) the base of the height of the fine weather cumuli and of the cumulo-nimbi of local character is situated between 1500 and 4500 m. above sea level; the average height is 3160 m. The diurnal and the annual variation of the condensation height and the frequency distribution are discussed.

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Zusammenfassung Die Basishöhe der Schönwettercumuli und der Cumulonimben lokalen Charakters liegt in den Walliser Alpen (Schweiz) zwischen 1500 und 4500 m über Meer; die mittlere Höhe beträgt 3160 m. Es werden die Tages- und die Jahresschwankung der Kondensationshöhe und Frequenzverteilung untersucht.

     

Scenario of the January 1997 West Bohemia Earthquake Swarm

In order to learn more about the nature of the dynamic processes taking place in the West Bohemia/Vogtland earthquake swarm region, we investigated the temporal and spatial variations of the source mechanisms of the January 1997 swarm beneath Nový Kostel (NKC). Visual analyses of WEBNET seismograms of over 800 events revealed that a specific feature of this swarm was the occurrence of eight classes of multiplet events. The result of single-source, absolute moment tensor inversion of the P and SH peak amplitudes of a subset of 70 events representing all multiplet classes indicated that eight statistically significant types of mechanisms occurred during the swarm. Two of them, types A and B in our denotation, comprised all M _L 1.3 events and predominated in the swarm. Type A were pure strike-slip mechanisms or strike-slip mechanisms containing a small normal component, with a nearly pure double-couple source. For class B events, oblique-thrust faulting and non-double-couple components significant at a fairly high confidence level were typical. Type A events predominated in the southern subcluster of the swarm, whereas most of type B events occurred in the subcluster northwards from NKC. This indicates that two major seismogenic planes were active during the swarm. The swarm essentially developed in four phases: in the first, type A events prevailed and the southern plane was active; during the second, characterised by the occurrence of both type A and B events (the former in the southern, the latter predominantly in the northern subcluster), the activity of the swarm culminated; in the third and fourth, the occurrence of type B events in the northern plane predominated, and only weak single events occurred southwards from NKC. Mechanisms of types AB , C , D , E , F and G , which were typical for M _L 1.2 events, occurred randomly throughout the swarm. Type AB events were identified in both the southern and northern clusters, type C , E , F and G mechanisms only southwards from NKC. Type D events exhibited a large scatter of hypocentres which fell in neither the southern nor the northern cluster. Focal mechanisms like those reported in this study and with analogous temporal and spatial variations were observed by other authors already fifteen years ago in the 1985/86 earthquake swarm and may, therefore, be typical for the region under study.     

The offshore east African rift system: new insights from the Sakalaves seamounts (Davie Ridge,SW Indian Ocean)

The offshore branch of the East African Rift System (EARS) has developed during Late Cenozoic time along the eastern Africa continental margin. While Neogene–Pleistocene extensional tectonic deformation has been evidenced along the northern segment of the Davie Ridge, the spatial extent of deformation further south remains poorly documented. Based on recent and various oceanographic datasets (bathymetric surveys, dredge samples and seismic profiles), our study highlights active normal faulting, modern east–west extensional tectonic deformation and Late Cenozoic alkaline volcanism at the Sakalaves Seamounts (18°S, Davie Ridge) that seem tightly linked to the offshore EARS development. In parallel, rift‐related tectonic subsidence appears responsible for the drowning of the Sakalaves Miocene shallow‐water carbonate platform. Our findings bring new insights regarding the development of the EARS offshore branch and support recent kinematic models proposing the existence of a plate boundary across the Mozambique Channel.     

Comparison Between Theoretical Predictions and LEGRI Background Noise Experimental Measurements

Trapped protons are responsible for the main component of LEGRIbackground. Detailed theoretical model has demonstrated that theproton-induced counting rate is two orders of magnitude larger thanthe counting rate of the diffuse gamma-ray flux. The continuous passesof LEGRI through the SAA (7 times everyday) makes very difficult thebackground modelling. Long and short lived isotopes contribute in verydifferent time scales to the proton-induced background component.The goal of this paper is to present a comparison between the long-livedbackground noise theoretical predictions and the experimental data. Theresults show an unexpected good agreement between the predicted and theobserved counting rates.     

Analysis of development and depth of backward erosion pipes in the presence of a coarse sand barrier

Backward erosion piping (BEP) is a failure mechanism that can affect the safety of water-retaining structures. It can occur when a local anomaly on the downstream side of an embankment causes a concentration of seepage flow at that location. Shallow pipes may then form, progressing in the upstream direction and leading to a collapse of the water-retaining structure. A novel and economically appealing measure against BEP is the coarse sand barrier (CSB), which is now being developed in a multiscale experimental programme in the Netherlands. The method involves placing a trench filled with coarse sand below the blanket layer on the downstream side of the embankment. The CSB prevents the upstream progression of the pipe and significantly enhances resistance to BEP. This paper presents medium-scale laboratory tests involving a range of sands, barrier depths and relative densities. The piping process and the observations of pipe progression in the presence of a CSB are presented, followed by a conceptual model. The presence of a CSB changed the erosion pattern. It resulted in pipe formation perpendicular to the flow direction over the entire width of the barrier before the barrier was damaged. The findings also demonstrate the effect of material properties on pipe initiation, progression and pipe depth. Measurements of the pipe depth are presented and analysed, revealing the significance of pipe depth for understanding the piping process. This analysis shows considerable erosion in the downstream background sand and demonstrates that erosion profiles and measured pipe depths are significantly larger than in BEP tests without a CSB.

     

Complete spin and orbital evolution of close-in bodies using a Maxwell viscoelastic rheology

In this paper, we present a formalism designed to model tidal interaction with a viscoelastic body made of Maxwell material. Our approach remains regular for any spin rate and orientation, and for any orbital configuration including high eccentricities and close encounters. The method is to integrate simultaneously the rotation and the position of the planet as well as its deformation. We provide the equations of motion both in the body frame and in the inertial frame. With this study, we generalize preexisting models to the spatial case and to arbitrary multipole orders using a formalism taken from quantum theory. We also provide the vectorial expression of the secular tidal torque expanded in Fourier series. Applying this model to close-in exoplanets, we observe that if the relaxation time is longer than the revolution period, the phase space of the system is characterized by the presence of several spin-orbit resonances, even in the circular case. As the system evolves, the planet spin can visit different spin-orbit configurations. The obliquity is decreasing along most of these resonances, but we observe a case where the planet tilt is instead growing. These conclusions derived from the secular torque are successfully tested with numerical integrations of the instantaneous equations of motion on HD 80606 b. Our formalism is also well adapted to close-in super-Earths in multiplanet systems which are known to have non-zero mutual inclinations.     

Still a good neighbour? Implications of changing priorities in New Zealand Aotearoa's aid sector

The period following the election of the National government in 2008 has been controversial for Aotearoa New Zealand's aid programme for a number of reasons. This article examines changes in funding modalities and other aspects of non‐governmental organisation (NGO)–government relations as the sites of contested philosophies that surround aid and development discourse. In focusing on the introduction of the Sustainable Development Fund in 2010, the article argues that this shift has generated significant uncertainty among the aid community and may ultimately undermine many of the relationships NGOs previously enjoyed with partners in the Global South.     

Hip-hop solutions of the 2N-body problem

Hip-hop solutions of the 2N-body problem with equal masses are shown to exist using an analytic continuation argument. These solutions are close to planar regular 2N-gon relative equilibria with small vertical oscillations. For fixed N, an infinity of these solutions are three-dimensional choreographies, with all the bodies moving along the same closed curve in the inertial frame.     

High-pressure single-crystal X-ray diffraction study of jadeite and kosmochlor

The crystal structures of natural jadeite, NaAlSi₂O₆, and synthetic kosmochlor, NaCrSi₂O₆, were studied at room temperature, under hydrostatic conditions, up to pressures of 30.4 (1) and 40.2 (1) GPa, respectively, using single-crystal synchrotron X-ray diffraction. Pressure–volume data have been fit to a third-order Birch–Murnaghan equation of state yielding V ₀ = 402.5 (4) Å³, K ₀ = 136 (3) GPa, and K ₀ ^′  = 3.3 (2) for jadeite and V ₀ = 420.0 (3) Å³, K ₀ = 123 (2) GPa and K ₀ ^′  = 3.61 (9) for kosmochlor. Both phases exhibit anisotropic compression with unit-strain axial ratios of 1.00:1.95:2.09 for jadeite at 30.4 (1) GPa and 1:00:2.15:2.43 for kosmochlor at 40.2 (1) GPa. Analysis of procrystal electron density distribution shows that the coordination of Na changes from 6 to 8 between 9.28 (Origlieri et al. in Am Mineral 88:1025–1032, 2003) and 18.5 (1) GPa in kosmochlor, which is also marked by a decrease in unit-strain anisotropy. Na in jadeite remains six-coordinated at 21.5 (1) GPa. Structure refinements indicate a change in the compression mechanism of kosmochlor at about 31 GPa in both the kinking of SiO₄ tetrahedral chains and rate of tetrahedral compression. Below 31 GPa, the O3–O3–O3 chain extension angle and Si tetrahedral volume in kosmochlor decrease linearly with pressure, whereas above 31 GPa the kinking ceases and the rate of Si tetrahedral compression increases by greater than a factor of two. No evidence of phase transitions was observed over the studied pressure ranges.