1,027 research outputs found
Pollen-based temperature and precipitation changes in the Ohrid Basin (western Balkans) between 160 and 70 ka
Our study aims to reconstruct climate changes that occurred at Lake Ohrid
(south-western Balkan Peninsula), the oldest extant lake in Europe, between
160 and 70 ka (covering part of marine isotope stage 6, MIS 6; all of MISÂ 5;
and the beginning of MISÂ 4). A multi-method approach, including the âModern
Analog Techniqueâ and the âWeighted Averaging Partial Least-Squares Regressionâ, is
applied to the high-resolution pollen sequence of the DEEP site, collected
from the central part of Lake Ohrid, to provide quantitative estimates of
climate and bioclimate parameters. This allows us to document climatic change
during the key periods of MISÂ 6 and MISÂ 5 in southern Europe, a region where
accurate climate reconstructions are still lacking for this time interval.
Our results for the penultimate glacial show cold and dry conditions, while the onset of
the âlast interglacialâ is characterized by wet and warm conditions, with temperatures
higher than today (by ca. 2 âC). The Eemian also shows the well-known climatic
tri-partition in the Balkans, with an initial pre-temperate phase of abrupt warming
(128â121 ka), a central temperate phase with decreasing temperatures associated with
wet conditions (121â118 ka), followed by a post-temperate phase of progressive change
towards cold and dry conditions (118â112 ka).
After the Eemian, an alternation of four warm/wet periods with cold/dry
ones, likely related to the succession of Greenland stadials and cold events
known from the North Atlantic, occurred. The observed pattern is also
consistent with hydrological and isotopic data from the central
Mediterranean.
The Lake Ohrid climate reconstruction shows greater similarity with climate
patterns inferred from northern European pollen records than with southern
European ones, which is probably due to its intermediate position and the
mountainous setting. However, this hypothesis needs further testing as very
few climate reconstructions are available for southern Europe for this key
time period.</p
An important role for Myb-MuvB and its target gene KIF23 in a mouse model of lung adenocarcinoma
The conserved Myb-MuvB (MMB) multiprotein complex has an important role in transcriptional activation of mitotic genes. MMB target genes are overexpressed in several different cancer types and their elevated expression is associated with an advanced tumor state and a poor prognosis. This suggests that MMB could contribute to tumorigenesis by mediating overexpression of mitotic genes. However, although MMB has been extensively characterized biochemically, the requirement for MMB in tumorigenesis in vivo has not been investigated. Here we demonstrate that MMB is required for tumor formation in a mouse model of lung cancer driven by oncogenic K-RAS. We also identify a requirement for the mitotic kinesin KIF23, a key target gene of MMB, in tumorigenesis. RNA interference-mediated depletion of KIF23 inhibited lung tumor formation in vivo and induced apoptosis in lung cancer cell lines. Our results suggest that inhibition of KIF23 could be a strategy for treatment of lung cancer
Corrigendum to âPollen-based paleoenvironmental and paleoclimatic change at Lake Ohrid (south-eastern Europe) during the past 500 kaâ published in Biogeosciences, 13, 1423â1437, 2016
In this corrigendum we report an updated pollen record from the Lake Ohrid DEEP site spanning the past 500 ka whereby we have reprocessed and re-analyzed 104 samples affected by chemical procedure problems that occurred in one palynological laboratory. Firstly, these samples were affected by the use of wrong containers, causing in- adequate settling of particles at the set centrifuging speed. Secondly, HCl and HF treatments were combined without the prescribed intermediate centrifuging and decanting steps. The inaccuracy in the protocol resulted in the loss of smaller pollen grains and in the overrepresentation of bisaccate ones in most of the re-analyzed samples. We therefore provide an updated set of figures with the new data and have revised the description of the results, discussion and conclusions re- ported in Sadori et al. (2016) where necessary. We stress that the majority of the original results and conclusions remain valid, while the recordsâ reliability and resolution have improved as 12 samples that had been omitted in the original study because of low count sums are now included in the revised dataset (Sadori et al., 2018)
Possible earthquake trigger for 6th century mass wasting deposit at Lake Ohrid (Macedonia/Albania)
Lake Ohrid shared by the Republics of Albania
and Macedonia is formed by a tectonically active graben within the south Balkans and suggested to be the oldest lake in Europe. Several studies have shown that the lake provides a valuable record of climatic and environmental changes and a distal tephrostratigraphic record of volcanic eruptions from Italy. Fault structures identified in seismic data demonstrate that sediments have also the potential to record tectonic activity in the region. Here, we provide an example of linking seismic and sedimentological information with tectonic activity and historical documents. Historical documents indicate that a major earthquake destroyed the city of Lychnidus (today: city of Ohrid) in the early 6th century AD. Multichannel
seismic profiles, parametric sediment echosounder profiles, and a 10.08m long sediment record from the western part of the lake indicate a 2m thick mass wasting deposit, which is tentatively correlated with this earthquake. The mass wasting deposit is chronologically well constrained, as it directly overlays the AD472/AD 512 tephra. Moreover, radiocarbon dates and cross correlation with other sediment sequences
with similar geochemical characteristics of the Holocene indicate that the mass wasting event took place prior to the onset of the Medieval Warm Period, and is attributed it to one of the known earthquakes in the region in the early 6th century AD
Modelling sediment export, retention and reservoir sedimentation in drylands with the WASA-SED model
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Ageâdepth model of the past 630 kyr for Lake Ohrid (FYROM/Albania) based on cyclostratigraphic analysis of downhole gamma ray data
Gamma ray (GR) fluctuations and potassium (K) values from downhole logging data obtained in the sediments of Lake Ohrid from 0 to 240 m below lake floor (b.l.f). correlate with fluctuations in Ύ18O values from the global benthic isotope stack LR04 (Lisiecki and Raymo, 2005). GR and K values are considered a reliable proxy to depict glacial-interglacial cycles, with high clastic input during cold and/or drier periods and high carbonate precipitation during warm and/or humid periods at Lake Ohrid. Spectral analysis was applied to investigate the climate signal and evolution over the length of the borehole. Linking downhole logging data with orbital cycles was used to estimate sedimentation rates and the effect of compaction was compensated for. Sedimentation rates increase on average by 14 % after decompaction of the sediment layers and the mean sedimentation rates shift from 45 cm kyr-1 between 0 and 110 m to 30 cm kyr-1 from 110 to 240 m b.l.f. Tuning of minima and maxima of gamma ray and potassium values versus LR04 extrema, in combination with eight independent tephrostratigraphical tie points, allows establishing of a robust age model for the downhole logging data over the past 630 kyr. © Author(s) 2015
A passive Stokes flow rectifier for Newtonian fluids
Non-linear effects of the Navier-Stokes equations disappear under the Stokes
regime of Newtonian fluid flows disallowing the fluid flow rectification. Here
we show mathematically and experimentally that passive flow rectification of
Newtonian fluids is obtainable under the Stokes regime of both compressible and
incompressible flows by introducing nonlinearity into the otherwise linear
Stokes equations. Asymmetric flow resistances arise in shallow nozzle/diffuser
microchannels with deformable ceiling, in which the fluid flow is governed by a
non-linear coupled fluid-solid mechanics equation. Fluid flow rectification has
been demonstrated for low-Reynolds-number flows (Re ~ O(0.001)-O(1)) of common
Newtonian fluids such as air, water, and alcohol. This mechanism can pave the
way for regulating the low-Reynolds-number fluid flows with potential
applications in precise low-flow-rate micropumps, drug delivery systems, etc
Aligning MIS5 proxy records from Lake Ohrid (FYROM) with independently dated Mediterranean archives: implications for core chronology
The DEEP site sediment sequence obtained during the ICDP SCOPSCO project at Lake Ohrid was dated using tephrostratigraphic information, cyclostratigraphy, and orbital tuning through marine isotope record. Although this approach is suitable for the generation of a general chronological framework of the long succession, it is insufficient to resolve more detailed paleoclimatological questions, such as leads and lags of climate events between marine and terrestrial records or between different regions. In this paper, we demonstrate how the use of different tie points can affect cyclostratigraphy and orbital tuning for the period between ca. 140 and 70 ka and how the results can be correlated with directly/indirectly radiometrically-dated Mediterranean marine and continental proxy records. The alternative age model obtained shows consistent differences with that proposed by Francke et al. (2015) for the same interval, in particular at the level of the MIS6-5e transition. According to this age model, different proxies from the DEEP site sediment record support an increase of temperatures between glacial to interglacial conditions, which is almost synchronous with a rapid increase in sea surface temperature observed in the western Mediterranean. The results show how important a detailed study of independent chronological tie points is for synchronizing different records and to highlight asynchronisms of climate events
Ly-alpha Emission-Line Galaxies at z = 3.1 in the Extended Chandra Deep Field South
We describe the results of an extremely deep, 0.28 deg^2 survey for z = 3.1
Ly-alpha emission-line galaxies in the Extended Chandra Deep Field South. By
using a narrow-band 5000 Anstrom filter and complementary broadband photometry
from the MUSYC survey, we identify a statistically complete sample of 162
galaxies with monochromatic fluxes brighter than 1.5 x 10^-17 ergs cm^-2 s^-1
and observers frame equivalent widths greater than 80 Angstroms. We show that
the equivalent width distribution of these objects follows an exponential with
a rest-frame scale length of w_0 = 76 +/- 10 Angstroms. In addition, we show
that in the emission line, the luminosity function of Ly-alpha galaxies has a
faint-end power-law slope of alpha = -1.49 +/- 0.4, a bright-end cutoff of log
L^* = 42.64 +/- 0.2, and a space density above our detection thresholds of 1.46
+/- 0.12 x 10^-3 h70^3 galaxies Mpc^-3. Finally, by comparing the emission-line
and continuum properties of the LAEs, we show that the star-formation rates
derived from Ly-alpha are ~3 times lower than those inferred from the
rest-frame UV continuum. We use this offset to deduce the existence of a small
amount of internal extinction within the host galaxies. This extinction,
coupled with the lack of extremely-high equivalent width emitters, argues that
these galaxies are not primordial Pop III objects, though they are young and
relatively chemically unevolved.Comment: 45 pages, 15 figures, accepted for publication in the Astrophysical
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