On the cascade mechanism of short surface wave modulation

International audienceModulation of short surface ripples by long surface or internal waves by a cascade mechanism is considered. At the first stage, the orbital velocity of the long wave (LW) adiabatically modulates an intermediate length nonlinear gravity wave (GW), which generates a bound (parasitic) capillary wave (CW) near its crest in a wide spatial frequency band. Due to strong dependence of the CW amplitude on that of the GW, the resulting ripple modulation by LW can be strong. Adiabatic modulation at the first stage is calculated for an arbitrarily strong LW current. The CWs are calculated based on the Lonquet-Higgins theory, in the framework of a steady periodic solution, which proves to be sufficient for the cases considered. Theoretical results are compared with data from laboratory experiments. A discussion of related sea clutter data is given in the conclusion

Infrasound generation by tornadic supercell storms

Acoustic wave generation by turbulence in the stratified, moist atmosphere is studied. It is shown that in the saturated moist air turbulence in addition to the Lighthill's quadrupole and the dipole sources of sound related to stratification and temperature fluctuations, there exist monopole sources related to heat and mass production during the condensation of moisture. We determine acoustic power of these monopole sources. Performed analysis shows that the monopole radiation is dominant for typical parameters of strong convective storms. Obtained results are in good qualitative agreement with the main observed characteristics of infrasound radiation by strong convective storms such as total acoustic power and characteristic frequency

New Kinds of Acoustic Solitons

We find that the modified sine-Gordon equation belonging to the class of the soliton equations describes the propagation of extremely short transverse acoustic pulses through the low-temperature crystal containing paramagnetic impurities with effective spin S=1/2 in the Voigt geometry case. The features of nonlinear dynamics of strain field and effective spins, which correspond to the different kinds of acoustic solitons, are studied.Comment: 9 pages, 1 figur

Upper Cretaceous paleosols of the Bain-Dzak section, southern Mongolia

© 2016, Pleiades Publishing, Ltd.Three paleosol profiles (FPS-profiles) are described from the Djadokhta Formation (Upper Cretaceous, Campanian), outcropping in the Bain-Dzak section (southern Gobi aimag, Mongolia). The new data allow the climate at the time of the formation of the Late Cretaceous FPS-profiles to be interpreted as semiarid with seasonal precipitation. The isolated fossil roots of higher plants preserved in situ in the FPS-1 profile of the Bain-Dzak section are described as a new species, Radicites gobiensis Naugolnykh, sp. nov

A new genus of male cones of voltzialean affinity, Uralostrobus voltzioides nov. gen., nov. sp., from the Lower Permian of the Urals (Russia)

© 2014 Elsevier Masson SAS. A new genus and species of male cones of coniferophyte from the Lower Permian (Artinskian and Kungurian) deposits of the Urals, Russia is described: Uralostrobus voltzioides Naugolnykh nov. gen., nov. sp. The cone shows characters typical of some representatives of conifers belonging to the order Voltziales: more or less isometrical bracts of rhombic shape, prolonged sporangia with attenuate apices, and bisaccate pollen of Illinites-type. General information on the associated female seed scales and vegetative leafy shoots is given as well

Fossil flora and stratigraphy of the Terrigenous Kungurian beds (Lower Permian) of the basin of the Barda River (Urals, Perm krai)

© 2014, Pleiades Publishing, Ltd. The stratigraphy and nomenclature of the most important sections of the Kungurian Stage composed of arenaceous-argillaceous deposits in the basin of the Barda River (Perm krai, Middle Urals) are characterized using paleobotanical and palynological data. A new genus Astrogaussia Naugolnykh, gen. nov. is established for female reproductive organs of the gymnosperm order Vojnovskyales from the Carboniferous and Permian deposits of Angaraland and the Subangaran ecotonic belt, represented by headlike aggregations of sterile scales and seed stalks, with attached orthotropic seeds with a well-developed integumental wing. New combinations are proposed: Astrogaussia imbricata (Naugolnykh) Naugolnykh, comb. nov. (type species of the genus Astrogaussia), A. cristata (Neuburg) Naugolnykh, comb. nov., and A. relaxata (Radczenko) Naugolnykh, comb. nov

Fossil flora from the Kazanian (Middle Permian) Iva-Gora locality, Soyana River, Arkhangelsk Region, Russia

© 2015, Pleiades Publishing, Ltd. A floral assemblage from the Iva-Gora locality (middle reaches of the Soyana River, Arkhangelsk Region) is described. The flora includes lycopsids, sphenophytes, ferns, peltasperms (order Peltaspermales, families Peltaspermaceae and Angaropeltaceae), conifers, and vojnovskians (order Vojnovskyales). A new genus of isolated seeds, Megasylvella gen. nov., is established. Praephylladoderma sojanaeana (Zalessky, 1937) Naugolnykh, comb. nov., emend. nov. is newly combined. The new species Megasylvella ivagorica Naugolnykh, sp. nov. and Radicites trimorphus Naugolnykh, sp. nov. are described

Permocallipteris, a new genus from the Permian of Angaraland

This paper deals with Permian peltasperm foliages attributed to a new genus Permocallipteris Naug., gen. nov., which is characteristic of Angaraland paleofloristic realm. The genus is proposed for two- or three-pinnate fronds with entire-margined last order segments (pinnules), normally with obtuse round to slightly acute apex, wide base, well-developed midvein and pinnately disposed lateral (secondary) veins. The fronds always possess clear additional (intercalated) pinnules attached directly to the frond rachis. The intercalated pinnules can be identical to common pinnules or be slightly modified and form wings on the frond rachis. The epidermal-cuticular structure of Permocallipteris fronds is characterized. The leaves are amphystomatic, the lower (adaxial) leaf cuticle is thinner and has numerous papillae. Stomata are monocyclic to incompletely dicyclic, with thick cutinization of the subsidiary cells

Laser-Generated Ultrasonic Beams

Now, it is well known that when the radiation from a high-power laser (a Q-switched laser) is focused onto a specimen, very large stresses are generated within the specimen primarily by thermo-elastic means as well as others. Generally, in this focused configuration, damage results. 11 Damage 11 is a bad word in the context of this workshop, so consequently we were concerned with harnessing this potential for lasers to generate large stress waves and thereby produce a stress wave of a more useful nature. In particular, we wanted to generate plane compressive stress pulses and sinusoidal wave trains to be used in subsequent wave propagation experiments from a nondestructive point of view. These waves may be used wherever a compressive stress pulse or a sinusoidal wave train with a very large amplitude might be needed. In particular, they may be used for flaw detection through materials that might be very dissipative where signals from piezoelectric crystals might not get through

A new matoniaceous fern from the Upper Triassic of the Caspian Depression in the context of florogenetic processes of transition from the Paleozoic to Mesozoic

© 2015, Pleiades Publishing, Ltd. A new matoniaceous fern species of the genus Phlebopteris Brongniart from the Upper Triassic of the Caspian Depression (Zhylyoiskii District, Atyrau Region, Kazakhstan) is described. It is represented by both sterile and fertile leaves preserved in situ, including the structure of sporangia and spores. The main trends in the evolution of ferns at transition from the Paleozoic to Mesozoic are discussed