New specimens of a fossil ostrich from the Miocene of Kenya

Fossilised hind limb bones from the late Middle Miocene (approximately 14 million-year-old [MYA]) Fort Ternan, Kadianga West and Ngorora localities in Western Kenya indicate the presence of a new representative of the ostrich genus Struthio. These new fossils represent some of the oldest known records for Struthio yet described, slightly younger than Struthio coppensi, from the Lower Miocene of Namibia. Because the four sub-species of the modern-day ostrich (Struthio camelus camelus, Struthio camelus australis, Struthio camelus massaicus, and Struthio camelus molybdophanes) inhabit the plains of Africa, and as recently as the 1940s, a fifth sub-species was also present in the Middle East and Saudi Arabia (Struthio camelus syriacus), records of Struthio from Kenya and Namibia testify to the much wider distribution of these cursorial birds in the relatively recent past. This is further supported by the very high frequency of ostrich eggshell fragments found across Africa and Eurasia, which vastly outweighs the amount of skeletal material uncovered over the last century.     

Calibration of an oscillating nozzle‐type rainfall simulator

Nozzle‐type rainfall simulators are commonly used in hydrologic and soil erosion research. Simulated rainfall intensity, originating from the nozzle, increases as the distance between the point of measurement and the source is decreased. Hence, rainfall measured using rain gauges would systematically overestimate the rainfall received at the ground level. A simple model was developed to adjust rainfall measured anywhere under the simulator to plot‐wide average rainfall at the ground level. Nozzle height, plot width, gauge diameter and height, and gauge location are required to compute this adjustment factor. Results from 15 runs at different rain intensities and durations, and with different rain gauge layouts, showed that a simple average of measured rain would overestimate the plot‐wide rain by about 20 per cent. Using the adjustment factor to convert measured rainfall for individual gauges before averaging improved the estimate of plot‐wide rainfall considerably. For the 15 runs considered, overall discrepancy between actual and measured rain is reduced to less than 1 per cent with a standard error of 0·97 mm. This model can be easily tested in the ?eld by comparing rainfall depths of different sized gauges. With the adjustment factor they should all give very similar values. Copyright © 2003 John Wiley & Sons, Ltd.     

Lake Neor reveals how mountain vegetation responded to 7000 years of hydroclimate variability in northwestern Iran

Palynological and geochemical analyses provide valuable information about modern and past climatic regimes and vegetation. The impact of climate and humans on past vegetation in the semi-arid areas of northwestern Iran has received increased interest in the wake of warming temperatures in the Middle East. Palynological and down-core XRF elemental abundances from a peat core from Lake Neor enabled a reconstruction of vegetational changes of the past 7000 years over the highlands of northwestern Iran. Periods of increased arboreal pollen (AP) types and high (Artemisia + Poaceae)/Chenopodiaceae ratios along with low titanium abundances, high percentages of total organic carbon, more negative δD values, and higher carbon accumulation rates suggest a relatively wet climate. These conditions have persisted during the periods 6700–6200, 5200–4450 and 3200–2200 cal a bp. The overall low AP values, substantial rise of Chenopodiaceae, high Ti abundances and low values of palaeo-redox proxies, are all evidences of a drier climate, as has been reconstructed for the periods 6200–5200 and 4030–3150 cal a bp and the last 2200 years. An important feature of the last centuries is the increase of anthropogenic and pastoral indicator pollen types. Our results may provide basic data to predict future trends in vegetation dynamics under future climate change in western Asia.     

Low melting temperature for calcite at 1000 bars on the join CaCO3‐H2O – some geological implications

Melting experiments of calcite were performed on the join CaCO₃‐H₂O at a pressure of 1000 bars. The system evolves to the ternary CaO‐H₂O‐CO₂ system during melting experiments. Our experiments show that partial melting of calcite begins at a low temperature, below 650 °C. Such a low partial melting temperature for carbonates revives the debate about the presence of carbonate melts in the upper crust. More specifically, the conditions for carbonate partial melting are present in carbonate host rocks undergoing contact metamorphism at high temperatures in the presence of water‐rich fluid. The presence of carbonate melts influences physical parameters such as viscosity and permeability in contact aureoles, and, furthermore, decarbonation reactions release massive amounts of CO₂.     

Elastic behavior of weakly cemented contact

We investigate the elastic behavior of weakly cemented contact. We show that the radial distribution of stresses and the stiffnesses of a cemented contact are governed by the ratio a/RΛ, where R, a, and Λ are, respectively, the grain radius, the contact size, and the ratio of the elastic moduli of cement and grains. Moreover, we show that a cemented contact is always less stiff than a Hertzian contact having a similar size. Finally, we propose accurate approximate expressions of the contact stiffnesses. Copyright © 2014 John Wiley & Sons, Ltd.     

Development of a rain‐on‐snow detection algorithm using passive microwave radiometry

Currently observed climate warming in the Arctic has numerous consequences. Of particular relevance, the precipitation regime is modified where mixed and liquid precipitation can occur during the winter season leading to rain‐on‐snow (ROS) events. This phenomenon is responsible for ice crust formation, which has a significant impact on ecosystems (such as biological, hydrological, ecological and physical processes). The spatially and temporally sporadic nature of ROS events makes the phenomenon difficult to monitor using meteorological observations. This paper focuses on the detection of ROS events using passive microwave (PMW) data from a modified brightness temperature (T_B) gradient approach at 19 and 37 GHz. The approach presented here was developed empirically for observed ROS events with coincident ground‐based PMW measurements in Sherbrooke, Quebec, Canada. It was then tested in Nunavik, Quebec, with the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR‐E). We obtained a detection accuracy of 57, 71 and 89% for ROS detection for three AMSR‐E grid cells with a maximum error of 7% when considering all omissions and commissions with regard to the total number of AMSR‐E passes throughout the winter period. Copyright © 2016 John Wiley & Sons, Ltd.     

Snow carrots after the Chelyabinsk event and model implications for highly porous solar system objects

After the catastrophic disruption of the Chelyabinsk meteoroid, small fragments formed funnels in the snow layer covering the ground. We constrain the pre‐impact characteristics of the fragments by simulating their atmospheric descent with the atmospheric entry model. Fragments resulting from catastrophic breakup may lose about 90% of their initial mass due to ablation and reach the snow vertically with a free‐fall velocity in the range of 30–90 m s^?1. The fall time of the fragments is much longer than their cooling time, and, as a consequence, fragments have the same temperature as the lower atmosphere, i.e., of about ?20 °C. Then, we use the shock physics code iSALE to model the penetration of fragments into fluffy snow, the formation of a funnel and a zone of denser snow lining its walls. We examine the influence of several material parameters of snow and present our best‐fit model by comparing funnel depth and funnel wall characteristics with observations. In addition, we suggest a viscous flow approximation to estimate funnel depth dependence on the meteorite mass. We discuss temperature gradient metamorphism as a possible mechanism which allows to fill the funnels with denser snow and to form the observed “snow carrots.” This natural experiment also helps us to calibrate the iSALE code for simulating impacts into highly porous matter in the solar system including tracks in the aerogel catchers of the Stardust mission and possible impact craters on the 67P/Churyumov‐Gerasimenko comet observed recently by the Rosetta mission.     

The organic chemistry and biology of the atmosphere of the planet Jupiter

In order to understand the chemical processes which may be taking place in the Jovian atmosphere, we have conducted a number of simulation experiments in the laboratory. These reactions appear to be significant for our understanding of chemical evolution and the nature and origin of organic matter in the universe. Mixtures of methane and ammonia in varying proportions have been exposed to electric discharges and the products analyzed. We have found that, as the methane and ammonia disappear, hydrogen cyanide and acetylene are to be built up. The analysis of the volatiles has also provided us with a wide range of aminonitriles. It is conceivable that some of these nitriles, on hydrolysis, will give rise to amino acids. On cyclization, some of them would provide the pathways for the origin of pyrimidines. A characteristic result of these reactions has also been the appearance of a red polymer which may have a bearing on the color in the red spots of Jupiter. Spectral analysis in the laboratory may provide some clues in our search for organic material in the Jovian atmosphere by orbiting spacecraft, or ground-based observations.     

Robotic telescopes for high energy astrophysics in Ondřejov

We report on two small aperture robotic telescopes called BART and D50 operated in Ondřejov. Both telescopes are capable of automatic observation of gamma ray burst (GRB) optical afterglows. Coordinates of GRBs are taken from alerts distributed via Internet. Telescopes observe other interesting high energy sources when there is not any alert. The smaller telescope BART has aperture D = 254 mm. The bigger telescope D50 has a primary mirror of diameter D = 500 mm. Both telescopes are controlled by free software package RTS2 and are accessible through Internet. We describe the two telescopes and related software and show some results such as our first observed optical counterpart of GRB.     

Proprietes Geometriques des Equations d'Euler-Poisson du Corps Solide a Point Fixe

Introduction et résumé Le problème de la réduction à l'ordre deux des équations d'Euler-Poisson par les 3 intégrales premières classiques a été étudié par Leimanis en 1971. Dans cet article on se propose de reprendre ce problème d'un point de vue géométrique. On étudie systématiquement les propriétés géométriques des équations d'Euler-Poisson du mouvement du corps solide pesant à point fixe dans deux cas. Dans le premier cas, le corps solide est muni d'un moment gyrostatique constant par rapport à lui-même. On montre ici que la réduction des équations d'Euler-Poisson nous ramène aux trois équations d'Euler initiales avec une structure présymplectique, ceci grâce à la présence d'une forme invariante de volume. D'autres conséquences géométriques sont signalées.Dans le deuxième cas, on supprime le moment gyrostatique. On remarque alors une propriété supplémentaire par rapport au cas précédent: la présence d'une transformation infinitésimale dûe à l'homogénéité des équations. La réduction des équations peut s'effectuer d'une infinité de manières alors qu'elle était unique dans le premier cas. Ceci est illustré par le cas intégrable de la toupie symétrique où l'on met en évidence, de façon originale, les deux quadratures nécessaires.

---

Geometrical properties of the Euler Poisson's equations of a heavy rigid body about a fixed point

In this paper, we study the geometrical properties of the Euler Poisson's equations of the motion of a heavy rigid body about a fixed point. Two cases are studied. In the first on the rigid body has a gyrostatic moment, constant with respect to itself. It is shown, from the reduction of Euler Poisson's equations, we that we have a presymplectic structure for the initial Euler's equations, and this fact being due to the existence of an invariant volume. Other geometrical consequences are obtained.Secondly the rigid body is considered without its gyrostatic moment. We have here a new property which is the existence of an infinitesimal transformation, due to the homogeneity of the equations. Here the reduction of the equation can be made by an infinity of ways, when it was unique precedently. This study is illustrated by the integrable case of the symetrical top.

---

---

Paper presented at the 1981 Oberwolfach Conference on Mathematical Methods in Celestial Mechanics.