1,535 research outputs found
Trends in cyclones in the high-latitude North Atlantic during 1979-2016
We report an increase in winter (DJF) cyclone densities in the areas around Svalbard and in northwestern Barents Sea and a decrease in cyclone densities in southeastern Barents Sea during 1979-2016. Despite high interannual variability, the trends are significant at the 90% confidence level. The changes appear as a result of a shift into a more meridional winter storm track in the high-latitude North Atlantic, associated with a positive trend in the Scandinavian Pattern. A significant decrease in the Brunt-Vaisala frequency east of Svalbard and a significant increase in the Eady Growth Rate north of Svalbard indicate increased baroclinicity, favouring enhanced cyclone activity in these regions. For the first time, we apply composite analysis to explicitly address regional consequences of these wintertime changes in the high-latitude North Atlantic. We find a tendency toward a warmer and more moist atmospheric state in the Barents Sea and over Svalbard with increased cyclone activity around Svalbard.Peer reviewe
The generalized non-conservative model of a 1-planet system - revisited
We study the long-term dynamics of a planetary system composed of a star and
a planet. Both bodies are considered as extended, non-spherical, rotating
objects. There are no assumptions made on the relative angles between the
orbital angular momentum and the spin vectors of the bodies. Thus, we analyze
full, spatial model of the planetary system. Both objects are assumed to be
deformed due to their own rotations, as well as due to the mutual tidal
interactions. The general relativity corrections are considered in terms of the
post-Newtonian approximation. Besides the conservative contributions to the
perturbing forces, there are also taken into account non-conservative effects,
i.e., the dissipation of the mechanical energy. This dissipation is a result of
the tidal perturbation on the velocity field in the internal zones with
non-zero turbulent viscosity (convective zones). Our main goal is to derive the
equations of the orbital motion as well as the equations governing
time-evolution of the spin vectors (angular velocities). We derive the
Lagrangian equations of the second kind for systems which do not conserve the
mechanical energy. Next, the equations of motion are averaged out over all fast
angles with respect to time-scales characteristic for conservative
perturbations. The final equations of motion are then used to study the
dynamics of the non-conservative model over time scales of the order of the age
of the star. We analyze the final state of the system as a function of the
initial conditions. Equilibria states of the averaged system are finally
discussed.Comment: 37 pages, 13 figures, accepted to Celestial Mechanics and Dynamical
Astronom
Hard-core Yukawa model for two-dimensional charge stabilized colloids
The hyper-netted chain (HNC) and Percus-Yevick (PY) approximations are used
to study the phase diagram of a simple hard-core Yukawa model of
charge-stabilized colloidal particles in a two-dimensional system. We calculate
the static structure factor and the pair distribution function over a wide
range of parameters. Using the statics correlation functions we present an
estimate for the liquid-solid phase diagram for the wide range of the
parameters.Comment: 7 pages, 9figure
Fractional reaction-diffusion equations
In a series of papers, Saxena, Mathai, and Haubold (2002, 2004a, 2004b)
derived solutions of a number of fractional kinetic equations in terms of
generalized Mittag-Leffler functions which provide the extension of the work of
Haubold and Mathai (1995, 2000). The subject of the present paper is to
investigate the solution of a fractional reaction-diffusion equation. The
results derived are of general nature and include the results reported earlier
by many authors, notably by Jespersen, Metzler, and Fogedby (1999) for
anomalous diffusion and del-Castillo-Negrete, Carreras, and Lynch (2003) for
reaction-diffusion systems with L\'evy flights. The solution has been developed
in terms of the H-function in a compact form with the help of Laplace and
Fourier transforms. Most of the results obtained are in a form suitable for
numerical computation.Comment: LaTeX, 17 pages, corrected typo
The anapole moment and nucleon weak interactions
From the recent measurement of parity nonconservation (PNC) in the Cs atom we
have extracted the constant of the nuclear spin dependent electron-nucleon PNC
interaction, ; the anapole moment constant, ; the strength of the PNC proton-nucleus potential, ; the -meson-nucleon interaction constant,
; and the strength of the neutron-nucleus potential, .Comment: Uses RevTex, 12 pages. We have added an explanation of the effect of
finite nuclear siz
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Is there H2O stacking disordered ice I in the Solar System?
Water ice exists in large quantities across the Solar System, and it is involved in a wide range of atmospheric and geological processes. Here we focus on the question if stacking disordered ice I (ice Isd) is present in the Solar System. The conditions required to form ice Isd are described and we argue that previous descriptions of ‘cubic ice’ (ice Ic) in the literature may in fact have been concerned with ice Isd. In contrast to the stable hexagonal ice I (ice Ih) and ice Ic, ice Isd is a highly complex material that encompasses a wide range of possible stacking regimes and structures. The most fundamental quantity to describe a given ice Isd sample is its cubicity which reflects the fraction of cubic stacking. Following an introduction into the characterisation techniques used to identify and characterise ice Isd, we discuss the various environments in the Solar System where ice Isd may exist and the relevance its existence may have. This includes the atmospheres of the inner planets, various icy moons as well as comets and other icy objects in the far reaches of the Solar System. The details of the stacking disorder may contain information about the formation and thermal history of ice Isd samples. This offers the exciting prospect of using ice Isd as a marker material for atmospheric and geological processes. The crystallographic space group of ice Isd allows polar structures which could be an important factor for the accretion of ice particles in space. We conclude that ice Isd should exist at several locations in the Solar System and in potentially large quantities. The definitive identification of ice Isd in a natural environment is a next major milestone in our understanding of the importance of water ice across the Solar System
3D MHD Flux Emergence Experiments: Idealized models and coronal interactions
This paper reviews some of the many 3D numerical experiments of the emergence
of magnetic fields from the solar interior and the subsequent interaction with
the pre-existing coronal magnetic field. The models described here are
idealized, in the sense that the internal energy equation only involves the
adiabatic, Ohmic and viscous shock heating terms. However, provided the main
aim is to investigate the dynamical evolution, this is adequate. Many
interesting observational phenomena are explained by these models in a
self-consistent manner.Comment: Review article, accepted for publication in Solar Physic
Evolution of whole-body enantiomorphy in the tree snail genus Amphidromus
Diverse animals exhibit left–right asymmetry in development. However, no example of dimorphism for the left–right polarity of development (whole-body enantiomorphy) is known to persist within natural populations. In snails, whole-body enantiomorphs have repeatedly evolved as separate species. Within populations, however, snails are not expected to exhibit enantiomorphy, because of selection against the less common morph resulting from mating disadvantage. Here we present a unique example of evolutionarily stable whole-body enantiomorphy in snails. Our molecular phylogeny of South-east Asian tree snails in the genus Amphidromus indicates that enantiomorphy has likely persisted as the ancestral state over a million generations. Enantiomorphs have continuously coexisted in every population surveyed spanning a period of 10 years. Our results indicate that whole-body enantiomorphy is maintained within populations opposing the rule of directional asymmetry in animals. This study implicates the need for explicit approaches to disclosure of a maintenance mechanism and conservation of the genus
Ecological Invasion, Roughened Fronts, and a Competitor's Extreme Advance: Integrating Stochastic Spatial-Growth Models
Both community ecology and conservation biology seek further understanding of
factors governing the advance of an invasive species. We model biological
invasion as an individual-based, stochastic process on a two-dimensional
landscape. An ecologically superior invader and a resident species compete for
space preemptively. Our general model includes the basic contact process and a
variant of the Eden model as special cases. We employ the concept of a
"roughened" front to quantify effects of discreteness and stochasticity on
invasion; we emphasize the probability distribution of the front-runner's
relative position. That is, we analyze the location of the most advanced
invader as the extreme deviation about the front's mean position. We find that
a class of models with different assumptions about neighborhood interactions
exhibit universal characteristics. That is, key features of the invasion
dynamics span a class of models, independently of locally detailed demographic
rules. Our results integrate theories of invasive spatial growth and generate
novel hypotheses linking habitat or landscape size (length of the invading
front) to invasion velocity, and to the relative position of the most advanced
invader.Comment: The original publication is available at
www.springerlink.com/content/8528v8563r7u2742
The last reconnection of the Marmara Sea (Turkey) to the World Ocean : A paleoceanographic and paleoclimatic perspective
Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Marine Geology 255 (2008): 64-82, doi:10.1016/j.margeo.2008.07.005.During the late glacial, marine isotope Stage 2, the Marmara Sea transformed into a
brackish lake as global sea level fell below the sill in the Dardanelles Strait. A record of the
basin’s reconnection to the global ocean is preserved in its sediments permitting the extraction of
the paleoceanographic and paleoclimatic history of the region. The goal of this study is to
develop a high-resolution record of the lacustrine to marine transition of Marmara Sea in order to
reconstruct regional and global climatic events at 24 a millennial scale. For this purpose, we mapped
the paleoshorelines of Marmara Sea along the northern, eastern, and southern shelves at
Çekmece, Prince Islands, and Imrali, using data from multibeam bathymetry, high-resolution
subbottom profiling (chirp) and ten sediment cores. Detailed sedimentologic, biostratigraphic
(foraminifers, mollusk, diatoms), X-ray fluorescence geochemical scanning, and oxygen and
carbon stable isotope analyses correlated to a calibrated radiocarbon chronology provided
evidence for cold and dry conditions prior to 15 ka BP, warm conditions of the Bolling-Allerod
from ~15 to 13 ka BP, a rapid marine incursion at 12 ka BP, still stand of Marmara Sea and
sediment reworking of the paleoshorelines during the Younger Dryas at ~11.5 to 10.5 ka BP, and
development of strong stratification and influx of nutrients as Black Sea waters spilled into
Marmara Sea at 9.2 ka BP. Stable environmental conditions developed in Marmara Sea after 6.0
ka BP as sea-level reached its present shoreline and the basin floors filled with sediments
achieving their present configuration.Support for the analyses was
from NSF-OCE-0222139; OCE-9807266 and PSC-CUNY 69138-00 38
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