30 research outputs found
Geochemistry and thermodynamic modelling of low-grade metasedimentary rocks from the Sakar-Strandja region, SE Bulgaria
Carbonate-silicate metasedimentary rocks of Triassic protolith age from the Sakar-Strandja region were affected by low-grade metamorphism in the frame of the Maritsa shear zone, which separates two first-order units of the Balkan orogenic system - Rhodopes and Srednogorie zones. The metamorphism was contemporaneous with strike-slip deformation and ductile shearing. We focus attention on whole-rock and mineral chemistry for better understanding of
protoliths origin and metamorphic evolution. The major minerals assemblage comprises calcite, dolomite quartz and white mica in variable proportions, minor chlorite, feldspars and rarely biotite. The accessory phases are ilmenite, rutile, monazite and zircon. Most of the samples show well-defined foliation. The siliciclastic component corresponds to shale, wacke or arkose origin and suggests a quartzose sedimentary provenance. The majority of trace elements tend to
incorporate in silicate minerals, while Sr shows pronounced preference for calcite. Chondrite normalized REE patterns correspond to continental crust. Immobile elements (La, Th, Sc, Zr, Ti) used for discrimination of tectonic regimes suggest continental island arc setting for the siliciclastic component origin. The P-T pseudosections (Perple_X 6.7.4, Connolly, 1990) combined with observed mineral assemblages and mineral chemistry isopleths of white mica, chlorite and plagioclase correspond to metamorphism in the range 200-400°C and 0.2-0.4 GPa. The results are supported by chlorite solid solution geothermometer. The thermodynamic modelling corroborates petrographic observations and confirms metamorphism at greenschist facies. Geochemical
data suggest protoliths origin due to shallow marine terrigenous-carbonate sedimentation with a provenance of typical upper continental crustal composition at continental island arc tectonic setting
Modeling extreme wave heights from laboratory experiments with the nonlinear Schrödinger equation
Spatial variation of nonlinear wave groups with different initial envelope
shapes is theoretically studied first, confirming that the simplest nonlinear
theoretical model is capable of describing the evolution of propagating wave
packets in deep water. Moreover, three groups of laboratory experiments run
in the wave basin of CEHIPAR (Canal de Experiencias Hidrodinámicas de El
Pardo, known also as El Pardo Model Basin) was founded in 1928 by the Spanish
Navy. are systematically compared with the numerical simulations of the
nonlinear Schrödinger equation. Although a little overestimation is
detected, especially in the set of experiments characterized by higher
initial wave steepness, the numerical simulation still displays a high degree
of agreement with the laboratory experiments. Therefore, the nonlinear
Schrödinger equation catches the essential characteristics of the extreme
waves and provides an important physical insight into their generation. The
modulation instability, resulting from the quasi-resonant four-wave
interaction in a unidirectional sea state, can be indicated by the
coefficient of kurtosis, which shows an appreciable correlation with the
extreme wave height and hence is used in the modified Edgeworth–Rayleigh
distribution. Finally, some statistical properties on the maximum wave
heights in different sea states have been related with the initial
Benjamin–Feir index
Rogue waters
In this essay we give an overview on the problem of rogue or freak wave
formation in the ocean. The matter of the phenomenon is a sporadic occurrence
of unexpectedly high waves on the sea surface. These waves cause serious danger
for sailing and sea use. A number of huge wave accidents resulted in damages,
ship losses and people injuries and deaths are known. Now marine researchers do
believe that these waves belong to a specific kind of sea waves, not taken into
account by conventional models for sea wind waves. This paper addresses to the
nature of the rogue wave problem from the general viewpoint based on the wave
process ideas. We start introducing some primitive elements of sea wave physics
with the purpose to pave the way for the further discussion. We discuss linear
physical mechanisms which are responsible for high wave formation, at first.
Then, we proceed with description of different sea conditions, starting from
the open deep sea, and approaching the sea cost. Nonlinear effects which are
able to cause rogue waves are emphasised. In conclusion we briefly discuss the
generality of the physical mechanisms suggested for the rogue wave explanation;
they are valid for rogue wave phenomena in other media such as solid matters,
superconductors, plasmas and nonlinear opticsComment: will be published in Contemporary Physic
Markers for Inflammation and Oxidative Stress in Patients with Coronary Artery Disease and Microvascular Disease – Is there a Difference?
Introduction: The clinical significance of inflammation (and markers such as resistin, hsCRP) and oxidative stress (e.g. 8-isoprostanes) for microvascular disease (MVD) and coronary artery disease (CAD) is still elusive
Time–frequency analysis of the sea state with the Andrea freak wave
The nonlinear and nonstationary properties of a special field wave record
are analysed with the Wigner spectrum with the Choi–Williams kernel. The
wave time series, which was recorded at the Ekofisk complex in the central
North Sea at 00:40 UTC (universal time coordinated) on 9 November 2007, contains an abnormally high
wave known as the "Andrea" wave. The ability of the Wigner spectrum to reveal
the wave energy distribution in frequency and time is demonstrated. The
results are compared with previous investigations for different sea states
and also the state with Draupner's abnormal "New Year" wave
Two partial melting events as recorded by the U-Th-Pb chronometer in monazite: LA-ICPMS in situ dating in metapelites from the Bulgarian Central Rhodopes
International audienc
Late Eocene synmetamorphic thrusting and syn-orogenic extension across the metamorphic pile of the Bulgarian Central Rhodope
International audienc
Persistent synmetamorphic thrusting in the Rhodope until ca. 33 Ma: evidence from the Nestos Shear Zone and implications for Aegean geodynamics
International audienc