316 research outputs found
Annual proxy data from Lago Grande di Monticchio (southern Italy) between 76 and 112 ka: new chronological constraints and insights on abrupt climatic oscillations
We present new annual sedimentological proxies and sub-annual element scanner
data from the Lago Grande di Monticchio (MON) sediment record for the
sequence 76–112 thousand years before present (ka). They are combined with
the previously published decadal to centennial resolved pollen assemblage in
order to provide a comprehensive reconstruction of six major abrupt stadial
spells (MON 1–6) in the central Mediterranean during the early phase of the last
glaciation. These climatic oscillations are defined by intervals of thicker
varves and high Ti-counts and coincide with episodes of forest depletion
interpreted as Mediterranean stadial conditions (cold winter/dry summer). Our
chronology, labelled as MON-2014, has been updated for the study interval by
tephrochronology and repeated and more precise varve counts and is
independent from ice-core and speleothem chronologies. The high-resolution
Monticchio data then have been compared in detail with the Greenland ice-core
δ<sup>18</sup>O record (NorthGRIP) and the northern Alps speleothem
δ<sup>18</sup>O<sub>calcite</sub> data (NALPS). Based on visual inspection of
major changes in the proxy data, MON 2–6 are suggested to correlate with
Greenland stadials (GS) 25–20. MON 1 (Woillard event), the first and
shortest cooling spell in the Mediterranean after a long phase of stable
interglacial conditions, has no counterpart in the Greenland ice core, but
coincides with the lowest isotope values at the end of the gradual decrease
in δ<sup>18</sup>O<sub>ice</sub> in NorthGRIP during the second half of the
Greenland interstadial (GI) 25. MON 3 is the least pronounced cold spell and
shows gradual transitions, whereas its NorthGRIP counterpart GS 24 is
characterized by sharp changes in the isotope records. MON 2 and MON 4 are
the longest and most pronounced oscillations in the MON sediments in good
agreement with their counterparts identified in the ice and spelethem
records. The length of MON 4 (correlating with GS 22) supports the duration
of stadial proposed by the NALPS timescales and suggests ca. 500 year longer
duration than calculated by the ice-core chronologies
GICC05<sub>modelext</sub> and AICC2012. Absolute dating of the cold spells
provided by the MON-2014 chronology shows good agreement among the MON-2014,
the GICC05<sub>modelext</sub> and the NALPS timescales for the period
between 112 and 100 ka. In contrast, the MON-2014 varve chronology dates the
oscillations MON 4 to MON 6 (92–76 ka) as ca. 3500 years older than the most
likely corresponding stadials GS 22 to GS 20 by the other chronologies
The importance of magnification effects in galaxy-galaxy lensing
Magnification changes the observed number counts of galaxies on the sky. This
biases the observed tangential shear profiles around galaxies, the so-called
galaxy-galaxy lensing (GGL) signal, and the related excess mass profile.
Correspondingly, inference of physical quantities, such as the mean mass
profile of halos around galaxies, are affected by magnification effects. We use
simulated shear and galaxy data of the Millennium Simulation to quantify the
effect on shear and mass estimates from magnified lens and source number
counts. The former are due to the large-scale matter distribution in the
foreground of the lenses, the latter are caused by magnification of the source
population by the matter associated with the lenses. The GGL signal is
calculated from the simulations by an efficient fast-Fourier transform that can
also be applied to real data. The numerical treatment is complemented by a
leading-order analytical description of the magnification effects, which is
shown to fit the numerical shear data well. We find the magnification effect is
strongest for steep galaxy luminosity functions and high redshifts. For a lens
redshift of , a limiting magnitude of in
the -band and a source redshift of , we find that a
magnification correction changes the shear profile up to and the mass is
biased by up to . For medium-redshift galaxies the relative change in
shear and mass is typically a few percent. As expected, the sign of the bias
depends on the local slope of the lens luminosity function ,
where the mass is biased low for and biased high for
. Whereas the magnification effect of sources is rarely
than more , the statistical power of future weak lensing surveys warrants
correction for this effect.Comment: this version fixes a typo in the prefactor of equation (14
Environmental phosphate differentially affects virulence phenotypes of uropathogenic Escherichia coli isolates causative of prostatitis
K-12 Escherichia coli cells grown in static media containing a critical phosphate (Pi) concentration 25 mM maintained a high polyphosphate (polyP) level in stationary phase, impairing biofilm formation, a phenomenon that is triggered by polyP degradation. Pi concentration in human urine fluctuates according to health state. Here, the influence of environmental Pi concentration on the occurrence of virulence traits in uropathogenic E. coli (UPEC) isolated from acute prostatitis patients was evaluated. After a first screening, 3 isolates were selected according to differential biofilm formation profiles depending on media Pi concentration. For each isolate, biofilm positive and negative conditions were established. Regardless of the isolate, biofilm formation capacity was accompanied with curli and cellulose production and expression of some key virulence factors associated with adhesion. When the selected isolates were grown in their non-biofilm-forming condition, low concentrations of nalidixic acid and ciprofloxacin induced biofilm formation. Interestingly, similar to laboratory strains, polyP degradation induced biofilm formation in the selected isolates. Data demonstrated the complexity of UPEC responses to environmental Pi and the importance of polyP metabolism in the virulence of clinical isolates.Fil: Grillo Puertas, Mariana. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Tucumán. Instituto Superior de Investigaciones BiolĂłgicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones BiolĂłgicas; Argentina. Universidad Nacional de Tucumán. Facultad de BioquĂmica, QuĂmica y Farmacia. Instituto de QuĂmica BiolĂłgica; ArgentinaFil: Martinez Zamora, Martin Gustavo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Tucumán. Instituto Superior de Investigaciones BiolĂłgicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones BiolĂłgicas; Argentina. Universidad Nacional de Tucumán. Facultad de BioquĂmica, QuĂmica y Farmacia. Instituto de QuĂmica BiolĂłgica; ArgentinaFil: Rintoul, Maria Regina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Tucumán. Instituto Superior de Investigaciones BiolĂłgicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones BiolĂłgicas; Argentina. Universidad Nacional de Tucumán. Facultad de BioquĂmica, QuĂmica y Farmacia. Instituto de QuĂmica BiolĂłgica; ArgentinaFil: Soto, Sara M.. Universidad de Barcelona; EspañaFil: Rapisarda, Viviana Andrea. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Tucumán. Instituto Superior de Investigaciones BiolĂłgicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones BiolĂłgicas; Argentina. Universidad Nacional de Tucumán. Facultad de BioquĂmica, QuĂmica y Farmacia. Instituto de QuĂmica BiolĂłgica; Argentin
Environmental phosphate differentially affects virulence phenotypes of uropathogenic Escherichia coli isolates causative of prostatitis
K-12 Escherichia coli cells grown in static media containing a critical phosphate (Pi) concentration 25 mM maintained a high polyphosphate (polyP) level in stationary phase, impairing biofilm formation, a phenomenon that is triggered by polyP degradation. Pi concentration in human urine fluctuates according to health state. Here, the influence of environmental Pi concentration on the occurrence of virulence traits in uropathogenic E. coli (UPEC) isolated from acute prostatitis patients was evaluated. After a first screening, 3 isolates were selected according to differential biofilm formation profiles depending on media Pi concentration. For each isolate, biofilm positive and negative conditions were established. Regardless of the isolate, biofilm formation capacity was accompanied with curli and cellulose production and expression of some key virulence factors associated with adhesion. When the selected isolates were grown in their non-biofilm-forming condition, low concentrations of nalidixic acid and ciprofloxacin induced biofilm formation. Interestingly, similar to laboratory strains, polyP degradation induced biofilm formation in the selected isolates. Data demonstrated the complexity of UPEC responses to environmental Pi and the importance of polyP metabolism in the virulence of clinical isolates.Fil: Grillo Puertas, Mariana. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Tucumán. Instituto Superior de Investigaciones BiolĂłgicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones BiolĂłgicas; Argentina. Universidad Nacional de Tucumán. Facultad de BioquĂmica, QuĂmica y Farmacia. Instituto de QuĂmica BiolĂłgica; ArgentinaFil: Martinez Zamora, Martin Gustavo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Tucumán. Instituto Superior de Investigaciones BiolĂłgicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones BiolĂłgicas; Argentina. Universidad Nacional de Tucumán. Facultad de BioquĂmica, QuĂmica y Farmacia. Instituto de QuĂmica BiolĂłgica; ArgentinaFil: Rintoul, Maria Regina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Tucumán. Instituto Superior de Investigaciones BiolĂłgicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones BiolĂłgicas; Argentina. Universidad Nacional de Tucumán. Facultad de BioquĂmica, QuĂmica y Farmacia. Instituto de QuĂmica BiolĂłgica; ArgentinaFil: Soto, Sara M.. Universidad de Barcelona; EspañaFil: Rapisarda, Viviana Andrea. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Tucumán. Instituto Superior de Investigaciones BiolĂłgicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones BiolĂłgicas; Argentina. Universidad Nacional de Tucumán. Facultad de BioquĂmica, QuĂmica y Farmacia. Instituto de QuĂmica BiolĂłgica; Argentin
A varved lake sediment record of <sup>10</sup>Be solar activity proxy for the Lateglacial-Holocene transition
Solar modulated variations in cosmogenic radionuclide production provide both information on past changes in the activity of the Sun and a global synchronization tool. However, to date the use of cosmogenic radionuclides for these applications is almost exclusively based on 10Be records from ice cores and 14C time-series from tree rings, all including archive-specific limitations. We present the first 10Be record from annually laminated (varved) lake sediments for the Lateglacial-Holocene transition from Meerfelder Maar. We quantify environmental influences on the catchment and, consequently, 10Be deposition using a new approach based on regression analyses between our 10Be record and environmental proxy time-series from the same archive. Our analyses suggest that environmental influences contribute to up to 37% of the variability in our 10Be record, but cannot be the main explanation for major 10Be excursions. Corrected for these environmental influences, our 10Be record is interpreted to dominantly reflect changes in solar modulated cosmogenic radionuclide production. The preservation of a solar production signal in 10Be from varved lake sediments highlights the largely unexplored potential of these archives for solar activity reconstruction, as global synchronization tool and, thus, for more robust paleoclimate studies
Dampened predictable decadal North Atlantic climate fluctuations due to ice melting
The oscillatory behaviour of the climate system on decadal timescales before the instrumental record is hard to quantify. However, knowledge of this variability is important for putting current changes in context and for supporting reliable future predictions. Here we investigate the recurrent component of Holocene climate variability in the North Atlantic sector from 10,500 to 2,000 years ago by conducting a frequency analysis of both an annually laminated climate record from a lake in England and outputs from a long transient simulation of the Atlantic meridional overturning circulation. We find consistent decadal variability over the past 6,700 years and before 8,500 years before present, probably reflecting predominance of solar and ocean forcings. Between these dates, climate variability was dampened on decadal timescales. Our results suggest that meltwater discharge into the North Atlantic and the subsequent hydrographic changes, from the opening of the Hudson Bay until the final collapse of the Laurentide Ice Sheet, disrupted the decadal cyclic signals for more than a millennium. Given the current acceleration of the Greenland Ice Sheet melting in response to global warming, this study provides long-term evidence of potential challenges predicting future patterns of the climate syste
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