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Natural and anthropogenic rapid changes in the Kara-Bogaz Gol over the last two centuries reconstructed from palynological analyses and a comparison to instrumental records
Palynological analyses (pollen and dinocysts) of a sediment core taken in the Kara-Bogaz Gol have been used to
reconstruct rapid and catastrophic environmental changes over the last two centuries (chronology based on 210Pb). A
natural cyclicity (65 years) of water level changes in the Caspian Sea and in the Kara-Bogaz Gol and anthropogenic
factors (building of a dam separating the CS and the KBG waters) combine to induce rapid changes in water levels of
the KBG, in the salinity of its waters and in vegetation cover of its surroundings. The impact of low water levels on
the dinocysts is marked by a lower diversity and the survival of two species that are typical of the KBG, the Caspian
Sea species present in the KBG having disappeared. During periods of higher water levels (AD 1871 to 1878), the
lake is surrounded by a steppe-like vegetation dominated by Artemisia; whereas during periods of low water levels
(AD 1878 to 1913 and AD 1955-1998), the emerged shore are colonised by Chenopodiaceae. The period of AD 1913
to 1955 corresponding to decreasing water levels has an extremely low pollen concentration and a maximum of
reworking of arboreal taxa. During the last low-level period, humans responded by abandoning the shores of the bay.
What happened to the KBG can be used as an example of what may happen in the future for the Aral Sea.
A problem of reworking of Tertiary dinocysts into modern deposits has been detected owing to the knowledge of the
modern dinoflagellate assemblages recently made available through a water survey. A comparison to modern surface
pollen samples from Central Asia (Anzali, Caspian Sea south and central basins, Aral Sea, Lake Balkhash, Lake
Issyk-Kul and the Chinese Tien-Shan range) allows us to establish the potential reworking of at least five arboreal
pollen taxa possibly by run-off and dust storms
Rings Over Which Cyclics are Direct Sums of Projective and CS or Noetherian
R is called a right WV -ring if each simple right R-module is injective
relative to proper cyclics. If R is a right WV -ring, then R is right uniform
or a right V -ring. It is shown that for a right WV-ring R, R is right
noetherian if and only if each right cyclic module is a direct sum of a
projective module and a CS or noetherian module. For a finitely generated
module M with projective socle over a V -ring R such that every subfactor of M
is a direct sum of a projective module and a CS or noetherian module, we show M
= X \oplus T, where X is semisimple and T is noetherian with zero socle. In the
case that M = R, we get R = S \oplus T, where S is a semisimple artinian ring,
and T is a direct sum of right noetherian simple rings with zero socle. In
addition, if R is a von Neumann regular ring, then it is semisimple artinian.Comment: A Para\^itre Glasgow Mathematical Journa
A Characterization of Infinite LSP Words
G. Fici proved that a finite word has a minimal suffix automaton if and only
if all its left special factors occur as prefixes. He called LSP all finite and
infinite words having this latter property. We characterize here infinite LSP
words in terms of -adicity. More precisely we provide a finite set of
morphisms and an automaton such that an infinite word is LSP if
and only if it is -adic and all its directive words are recognizable by
Activity Dependent Branching Ratios in Stocks, Solar X-ray Flux, and the Bak-Tang-Wiesenfeld Sandpile Model
We define an activity dependent branching ratio that allows comparison of
different time series . The branching ratio is defined as . The random variable is the value of the next signal given
that the previous one is equal to , so . If
, the process is on average supercritical when the signal is equal to
, while if , it is subcritical. For stock prices we find
within statistical uncertainty, for all , consistent with an ``efficient
market hypothesis''. For stock volumes, solar X-ray flux intensities, and the
Bak-Tang-Wiesenfeld (BTW) sandpile model, is supercritical for small
values of activity and subcritical for the largest ones, indicating a tendency
to return to a typical value. For stock volumes this tendency has an
approximate power law behavior. For solar X-ray flux and the BTW model, there
is a broad regime of activity where , which we interpret as an
indicator of critical behavior. This is true despite different underlying
probability distributions for , and for . For the BTW model the
distribution of is Gaussian, for sufficiently larger than one, and
its variance grows linearly with . Hence, the activity in the BTW model
obeys a central limit theorem when sampling over past histories. The broad
region of activity where is close to one disappears once bulk dissipation
is introduced in the BTW model -- supporting our hypothesis that it is an
indicator of criticality.Comment: 7 pages, 11 figure
Kinetics of chloride exchange in aqueous chloride-tetrachloroplatinate (II) system
The investigation described in this thesis has included a study of the kinetics of the exchange of chlorine between chloride and tetrachloroplatinate (II) in aqueous solution. As the case in any exchange study it has been necessary to develop a radioactive tracer technique and separation procedure so that the extent of the exchange could be ascertained. By the determination of the extent of exchange as a function of time, the dependence of the rate of exchange upon a number of concentration variables was demonstrated. It was to be expected that the experimental exchange rate law would elucidate features of the mechanism of the process and the species which were involved
The Structure of a Low-Metallicity Giant Molecular Cloud Complex
To understand the impact of low metallicities on giant molecular cloud (GMC)
structure, we compare far infrared dust emission, CO emission, and dynamics in
the star-forming complex N83 in the Wing of the Small Magellanic Cloud. Dust
emission (measured by Spitzer as part of the S3MC and SAGE-SMC surveys) probes
the total gas column independent of molecular line emission and traces
shielding from photodissociating radiation. We calibrate a method to estimate
the dust column using only the high-resolution Spitzer data and verify that
dust traces the ISM in the HI-dominated region around N83. This allows us to
resolve the relative structures of H2, dust, and CO within a giant molecular
cloud complex, one of the first times such a measurement has been made in a
low-metallicity galaxy. Our results support the hypothesis that CO is
photodissociated while H2 self-shields in the outer parts of low-metallicity
GMCs, so that dust/self shielding is the primary factor determining the
distribution of CO emission. Four pieces of evidence support this view. First,
the CO-to-H2 conversion factor averaged over the whole cloud is very high 4-11
\times 10^21 cm^-2/(K km/s), or 20-55 times the Galactic value. Second, the
CO-to-H2 conversion factor varies across the complex, with its lowest (most
nearly Galactic) values near the CO peaks. Third, bright CO emission is largely
confined to regions of relatively high line-of-sight extinction, A_V >~ 2 mag,
in agreement with PDR models and Galactic observations. Fourth, a simple model
in which CO emerges from a smaller sphere nested inside a larger cloud can
roughly relate the H2 masses measured from CO kinematics and dust.Comment: 17 pages, 10 figures (including appendix), accepted for publication
in the Astrophysical Journa
Lingulodinium machaerophorum expansion over the last centuries in the Caspian Sea reflects global warming
This article is made available through the Brunel Open Access Publishing Fund. Copyright @ Author(s) 2012. This work is distributed
under the Creative Commons Attribution 3.0 License.We analysed dinoflagellate cyst assemblages in four short sediment cores, two of them dated by radionuclides, taken in the south basin of the Caspian Sea. The interpretation of the four sequences is supported by a collection of 27 lagoonal or marine surface sediment samples. A sharp increase in the biomass of the dinocyst occurs after 1967, especially owing to Lingulodinium machaerophorum. Considering nine other cores covering parts or the whole of Holocene, this species started to develop in the Caspian Sea only during the last three millennia. By analysing instrumental data and collating existing reconstructions of sea level changes over the last few millennia, we show that the main forcing of the increase of L. machaerophorum percentages and of the recent dinocyst abundance is global climate change, especially sea surface temperature increase. Sea level fluctuations likely have a minor impact. We argue that the Caspian Sea has entered the Anthropocene
Rotational cooling of molecules using lamps
We investigate theoretically the application of tailored incoherent
far-infrared fields in combination with laser excitation of a single
rovibrational transition for rotational cooling of translationally cold polar
diatomic molecules. The cooling schemes are effective on a timescale shorter
than typical unperturbed trapping times in ion traps and comparable to
obtainable confinement times of neutral molecules.Comment: 5 pages, 2 figure
Solar rotation rate and its gradients during cycle 23
Available helioseismic data now span almost the entire solar activity cycle
23 making it possible to study solar-cycle related changes of the solar
rotation rate in detail. In this paper we study how the solar rotation rate, in
particular, the zonal flows change with time. In addition to the zonal flows
that show a well known pattern in the solar convection zone, we also study
changes in the radial and latitudinal gradients of the rotation rate,
particularly in the shear layer that is present in the immediate sub-surface
layers of the Sun. In the case of the zonal-flow pattern, we find that the band
indicating fast rotating region close to the equator seems to have bifurcated
around 2005. Our investigation of the rotation-rate gradients show that the
relative variation in the rotation-rate gradients is about 20% or more of their
average values, which is much larger than the relative variation in the
rotation rate itself. These results can be used to test predictions of various
solar dynamo models.Comment: To appear in ApJ. Fig 5 has been corrected in this versio
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