Evolución geológica en la cuenca baja del río Colorado durante el cenozoico, Patagonia Norte, Argentina

Climatic changes and eustatic sea levels have been assumed to be the most important controllers of the Colorado River alluvial fan in northern Patagonia. Although the alluvial fan occurs in a region considered tectonically stable, there are pieces of evidence that the Miocene Andean orogeny has reactivated inherited structures, with subsequent geomorphological changes that date back to the Pleistocene. Besides, the clear evidence of neotectonism in the region and their effects on the evolution of this fan, it has not been studied in detail yet. In this study, we map and analyze six sections outcropping in different terraces of the alluvial fan with the primary aim of disentangling the role of tectonism, climate and eustatic changes on the evolution of the alluvial fan. This study is part of a bigger project aimed to understand the origin of the shallow lakes occurring in northern Patagonia. Our results indicate that the alluvial fan of the Colorado River was established in the area around the Middle Pleistocene. Evidence of deformations in Miocene to Pleistocene units indicates significant neotectonism during the Upper Pleistocene. By the Pleistocene-Holocene transition, tectonism produced incision generating a set of terraces. After this time, an important climate change from semiarid to arid favored the calcretization of some terraces. By the Pleistocene-Middle Holocene, the terraces were covered by ancient eolian sediment accumulated during dry conditions. By the Middle Holocene, a broad alluvial fan developed in the region under a warmer and more humid climate generating the Alluvial Colorado River-III deposit at the T3 terrace. In the late Holocene, aggradation process was favored by a high sea level and temperate-arid climate, producing T4 terrace. At the same time, this climate condition favored the local deflation-sedimentation processes that resulted in the deposition of modern eolian deposits (mE) over the T3 terrace. The depressions generated by the deflation were, later on, occupied by shallow lakes when the climate turn more humid. Subsequently, during regressive sea level condition, ca. 2000 years BP, the T4 terrace was partially eroded and the modern alluvial plain formed.La evolución geológica y morfológica del abanico aluvial del río Colorado en el norte de Patagonia ha sido explicada, en su zona distal, como resultado de cambios eustáticos y climáticos. A pesar de que el abanico se encuentra en una región considerada como una zona tectónicamente estable, hay evidencia de que la orogenia andina durante el Mioceno reactivó estructuras preexistentes y produjo cambios geomorfológicos asignados al Pleistoceno. Sin embargo, la influencia de la tectónica en la evolución del abanico aluvial del río Colorado no ha sido aún estudiada. En este trabajo, se levantaron y estudiaron seis secciones que afloran en distintas terrazas del abanico aluvial del río Colorado con el objetivo principal de comprender el rol de la tectónica, los cambios climáticos y eustáticos en la evolución del abanico aluvial. Este estudio es parte de un proyecto mayor que busca entender el origen de las lagunas someras presentes en la parte norte de la Patagonia. Nuestros resultados indican que el abanico aluvial del río Colorado se estableció en el área alrededor del Pleistoceno medio. La evidencia de deformaciones en las unidades del Mioceno al Pleistoceno indica una significativa actividad neotectónica durante el Pleistoceno superior. Para la transición Pleistoceno-Holoceno, el tectonismo generó una serie de terrazas. Posteriormente, un cambio climático de semiárido a árido favoreció la calcretización de las terrazas. Durante el Pleistoceno-Holoceno medio, las terrazas fueron cubiertas por la acumulación de sedimentos eólicos antiguos en condiciones de clima seco. En el Pleistoceno medio se desarrolló un amplio abanico aluvial en la región, en un clima más cálido y húmedo, que generó los depósitos aluviales del río Colorado-III en un nuevo nivel de terraza (T3). En el Holoceno tardío, el proceso de agradación fue favorecido por un alto nivel del mar y un clima templado-árido, que produjo la terraza T4. Al mismo tiempo, estas condiciones climáticas favorecieron los procesos de deflación-sedimentación local que dieron lugar a la deposición de depósitos eólicos modernos (mE) sobre la terraza T3. Las depresiones generadas por la deflación fueron, más tarde, ocupadas por los lagos poco profundos cuando el clima se volvió más húmedo. Posteriormente, durante condiciones regresivas del nivel del mar, ca. 2000 años AP, la terraza T4 fue parcialmente erosionada y se formó la llanura aluvial moderna.Fil: Seitz, Carina. Universidad Nacional del Sur. Departamento de Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Vélez, María I.. University Of Regina; CanadáFil: Perillo, Gerardo Miguel E.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina. Universidad Nacional del Sur. Departamento de Geología; Argentin

Design of the Target Dump Injection Segmented (TDIS) in the framework of the High Luminosity Large Hadron Collider (HL-LHC) project

The High Luminosity Large Hadron Collider (HL-LHC) Project at CERN calls for increasing beam brightness and intensity. In this scenario, most equipment has to be redesigned and rebuilt. In particular, beam intercepting devices (such as dumps, collimators, absorbers and scrapers) have to withstand impact or scraping of the new intense HL-LHC beams without failure. Furthermore, minimizing the electromagnetic beam-device interactions is also a key design driver since they can lead to beam instabilities and excessive thermo-mechanical loading of devices. In this context, the present study assesses the conceptual design quality of the new LHC injection protection absorber, the Target Dump Injection Segmented (TDIS), from an electromagnetic and thermo-mechanical perspective. This contribution analyzes the thermo-mechanical response of the device considering two cases: an accidental beam impact scenario and another accidental scenario with complete failure of the RFcontacts. In addition, this paper presents the preliminary results from the simulation of the energy deposited by the two counter-rotating beams circulating in the device

The effects of extreme drought events on the morphometry of shallow lakes: Implications for sediment resuspension and littoral and pelagic zone distribution

Shallow lakes, because of their depth, are more vulnerable to the effects of wind and changes in precipitation and evaporation that deeper lakes and thus respond more dramatically to extreme climatic events, such as drought. The morphology of shallow lakes influences many of their physical, chemical, biological and sedimentological processes including sediment resuspension. Sediment resuspension can trigger undesired effects such as eutrophication, increase in turbidity, cyanobacterial blooms, and also affects the distribution and extent of the littoral and pelagic zones (habitat distribution) with potentially negative consequences on biodiversity and loss of native species. These problems are an increasing concern in the face of global warming. To understand how changes in lake' morphometry, triggered by extreme drought events influence sediment resuspension and habitat distribution, we studied four shallow lakes located in the southwest of the Argentinean Pampas. Each lake was characterized by its bathymetry, morphometric parameters (including area, shore development, dynamic ratio, critical depth), the spatial distribution of the littoral and pelagic areas, and the effect of the waves on sediment resuspension. We measured the Area and Shore development again during selected extreme drought periods identified through the Standardized Precipitation-Evapotranspiration Index. Then, for the given drought period, we calculated the extent and distribution of littoral and pelagic areas and the critical depth at which sediment resuspension occurred and then estimated the percentage of the lake that would be affected by it. We found that Pampean lakes are profoundly affected by sediment resuspension triggered by wind during extreme dry events. Droughts have different effects depending on lake morphology. Dry periods caused not only a decrease in water volume, but also modified the extension of littoral and pelagic zones and increased sediment resuspension. These results have significant implications for the preservation of these rich ecosystems, especially in the context of global warming.Fil: Seitz, Carina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina. Universidad Nacional del Sur. Departamento de Geología; ArgentinaFil: Facundo, Scordo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina. Universidad Nacional del Sur. Departamento de Geografía y Turismo; Argentina. University of Nevada; Estados UnidosFil: Vitale, Alejandro José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras; ArgentinaFil: Vélez, María I.. University of Saskatchewan; CanadáFil: Perillo, Gerardo Miguel E.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina. Universidad Nacional del Sur. Departamento de Geología; Argentin

Impedance measurements and simulations on the TCT and TDI LHC collimators

The LHC collimation system is a critical element for the safe operation of the LHC machine and it is subject to continuous performance monitoring, hardware upgrade and optimization. In this work we will address the impact on impedance of the upgrades performed on the injection protection target dump (TDI), where the absorber material has been changed to mitigate the device heating observed in machine operation, and on selected secondary (TCS) and tertiary (TCT) collimators, where beam position monitors (BPM) have been embedded for faster jaw alignment. Con- cerning the TDI, we will present the RF measurements per- formed before and after the upgrade, comparing the result to heating and tune shift beam measurements. For the TCTs, we will study how the higher order modes (HOM) intro- duced by the BPM addition have been cured by means of ferrite placement in the device. The impedance mitigation campaign has been supported by RF measurements whose results are in good agreement with GdfidL and CST simula- tions. The presence of undamped low frequency modes is proved not to be detrimental to the safe LHC operation

Quantitative and qualitative effect of gH625 on the nanoliposome-mediated delivery of mitoxantrone anticancer drug to HeLa cells

The present work investigates in vitro the delivery of the anticancer drug mitoxantrone (MTX) to HeLa cancer cells by means of liposomes functionalized with the novel cell penetrating peptide gH625. This hydrophobic peptide enhances the delivery of doxorubicin to the cytoplasm of cancer cells, while the mechanism of this enhancement has not yet been understood. Here, in order to get a better insight into the role of gH625 on the mechanism of liposome-mediated drug delivery, we treated HeLa cells with liposomes functionalized with gH625 and loaded with MTX; liposome were characterized in terms of their physico-chemical properties and drug release kinetics. To quantify the MTX uptake and to study the subcellular drug distribution and interaction, we took advantage of the intrinsic fluorescence of MTX and of the fluorescence-based techniques like fluorescence-activated cell sorting (FACS) and confocal spectral imaging (CSI). gH625 liposomes showed an enhanced staining of the internalized drug is observed mainly in hydrophobic regions of the cytoplasm, where the increased presence of an oxidative metabolite of the drug is observed. MTX delivery with gH625-decorated nanoliposomes enhances the quantity of both the intracellular drug and of its oxidative metabolite and contributes to higher anticancer efficacy of the drug

Color plasma oscillation in strangelets

The dispersion relation and damping rate of longitudinal color plasmons in finite strange quark matter (strangelets) are evaluated in the limits of weak coupling, low temperature, and long wavelength. The property of the QCD vacuum surrounding a strangelet makes the frequency of the plasmons nearly the same as the color plasma frequency of bulk matter. The plasmons are damped by their coupling with individual excitations of particle-hole pairs of quarks, of which the energy levels are discretized by the boundary. For strangelets of macroscopic size, the lifetime of the plasmons is found to be proportional to the size, as in the case of the usual plasma oscillations in metal nanoparticles.Comment: 9 pages (REVTeX), 2 Postscript figures, to be published in Phys. Rev.

New Neuronal Subtypes With a “Pre-Pancreatic” Signature in the Sea Urchin Stongylocentrotus purpuratus

Neurons and pancreatic endocrine cells have a common physiology and express a similar toolkit of transcription factors during development. To explain these common features, it has been hypothesized that pancreatic cells most likely co-opted a pre-existing gene regulatory program from ancestral neurons. To test this idea, we looked for neurons with a “pre-pancreatic” program in an early-branched deuterostome, the sea urchin. Only vertebrates have a proper pancreas, however, our lab previously found that cells with a pancreatic-like signature are localized within the sea urchin embryonic gut. We also found that the pancreatic transcription factors Xlox/Pdx1 and Brn1/2/4 co-localize in a sub-population of ectodermal cells. Here, we find that the ectodermal SpLox+ SpBrn1/2/4 cells are specified as SpSoxC and SpPtf1a neuronal precursors that become the lateral ganglion and the apical organ neurons. Two of the SpLox+ SpBrn1/2/4 cells also express another pancreatic transcription factor, the LIM-homeodomain gene islet-1. Moreover, we find that SpLox neurons produce the neuropeptide SpANP2, and that SpLox regulates SpANP2 expression. Taken together, our data reveal that there is a subset of sea urchin larval neurons with a gene program that predated pancreatic cells. These findings suggest that pancreatic endocrine cells co-opted a regulatory signature from an ancestral neuron that was already present in an early-branched deuterostome

Caracterización de médanos parabólicos de la región pampeana oriental, centro oeste de la provincia de Buenos Aires (Argentina).

 La región pampeana, especialmente la provincia de Buenos Aires, se caracteriza por la presencia de paisajes eólicos que, si bien responden a eventos producidos en el Cuaternario Superior, en la actualidad son reactivados por la actividad agropecuaria. El objetivo de este trabajo se centra en la detección y delimitación de un campo de médanos parabólicos parcialmente reactivados, ubicados en el centro oeste de dicha provincia, que si bien han sido mencionados en la literatura, no han sido objeto de estudio detallado. Mediante la generación de un Modelo Digital de Elevaciones (MDE) a partir de imágenes SRTM (Shuttle Radar Topography Mission) se ha detectado un campo con un total de 254 médanos parabólicos que ocupan 20.200 km2, ubicados entre los 120 y 90 msnm. Los mismos presentan una dirección general SW-NE, con anchos que varían entre 2 y 5 km y alturas entre 2 y 6 m. Aplicando la herramienta Distancia Vertical al Curso (Vertical Distance to Channel Network, VDCN) del Software SAGA GIS 2.1.2 y una clasificación automática no supervisada en ArcGIS 10.1, se lograron discriminar los médanos de la planicie circundante. A partir de muestras de sedimento de un médano testigo ubicado en la localidad de 30 de Agosto (Buenos Aires), se establecieron claras diferencias en la granulometría en distintos sectores del mismo. La ubicación de estos médanos es clave en la configuración del escurrimiento y, en consecuencia, este paisaje arenoso tiene un rol importante en la configuración del espacio del área de estudio ya que se forman lagunas intermedanales someras cuyo desarrollo depende de las precipitaciones locales

Contribution of carbonate precipitation to the preservation of ripples in siliciclastic sediments colonized by microorganisms.

The present study traces a carbonate lamination in microbial mats in a siliciclastic coastal environment. The aim of this paper is to determine how physicochemical and biological processes influence the preservation of sedimentary structures such as ripple marks, covering it by carbonate precipitation. Such precipitation is a combination of the activity of microorganisms, and physicochemical factors. Biological factors, such as photosynthesis, composition and activity of the microbial community, and presence of exopolymeric substances (EPS), play a significant role in coastal environments, while high-energy hydrodynamic events supply seawater, providing calcium and carbonate ions, and trigger events like sediment transport, deposition, and erosion. The combination of these hydrodynamic events with the microbial activity creates physical sedimentary structures, such as ripple marks, which can be biostabilized. The study was conducted in Paso Seco (40°38’40´´S; 62°12´22´´W), a modern coastal flat within an elongated semi-closed basin colonized by microbial mats and categorized as a supratidal zone. Water samples were taken from different ponds within the flat with different degrees of evaporation, and in a tidal creek for hydrochemical analyses. Seawater level fluctuations were measured in the tidal flat over a 10-month period in 2018 using a HOBO water level logger. Ripple field formation over the tidal flat was documented after the occurrence of a strong storm and was monitored throughout three subsequent field trips, and sedimentary samples were taken in a field trip. Petrographic studies show a laterally continuous dense micritic calcite layer, 100–200 µm in thickness, covering the ripple structure, improving the preservation of these bedforms. The presence of microorganisms in the sedimentary environment enables the stabilization of ripple marks because their motility and abundant EPS secretion bind the sediment grains and generate an organic layer that protects them from erosion. On the other hand, the presence of microbial mats contributes to the early preservation of the ripples because they create the adequate conditions for carbonate precipitation. Our observations of modern sedimentary structures and the in situ study of their evolution and early lithification may provide an indicator of microbial colonization and stabilization of ripples in the paleoenvironmental reconstruction