Rapid longitudinal migrations of the filament front off Namibia (SE Atlantic) during the past 70 kyr

Although productivity variations in coastal upwelling areas are mostly attributed to changes in wind strength, productivity dynamics in the Benguela Upwelling System (BUS) is less straightforward due to its complex atmospheric and hydrographic settings. In view of these settings, past productivity variations in the BUS can be better investigated with downcore sediments representing different productivity regimes. In this study, two sediment cores retrieved at ca. 25°–26°S in the BUS and representing different productivity regimes were studied. By using micropaleontological, geochemical and temperature proxies measured on core MD96-2098, recovered at 2910 m water depth in the bathypelagic zone at 26°S off Namibia, variations of filament front location, productivity and temperature in the central BUS over the past 70 kyr were reconstructed. The comparison with newly-generated alkenone-based sea-surface temperature (SST) and previously obtained data at site GeoB3606-1 (~ 25°S; ca. 50 km shoreward from MD96-2098) allowed the recognition of four main phases: (1) upwelling front above the mid slope (70 kyr–44 kyr), (2) seaward displacement of the upwelling front beyond the mid slope (44 kyr–31 kyr), (3) main upwelling front over the hemipelagial (31 kyr–19 kyr), and (4) shoreward contraction of the upwelling filament, and decreased upwelling strength over most of the uppermost bathypelagic (19 kyr–6 kyr). The latitudinal migration of the Southern Hemisphere westerlies and the consequent contractions and expansions of the subpolar gyre played a significant role in millennial and submillennial variability of SST off Namibia. The strength of the southeasterly trade winds, rapid sea-level variations and the equatorward leakage of Antarctic silicate might have acted as amplifiers. Although late Quaternary variations of productivity and upwelling intensity in eastern boundary current systems are thought to be primarily linked to the variability in wind stress, this multi-parameter reconstruction shows that interplaying mechanisms defined the temporal variation pattern of the filament front migrations and the diatom production off Namibia during the past 70 kyr

The interplay between the surface and bottom water environment within the Benguela Upwelling System over the last 70 ka

The Benguela Upwelling System (BUS), located between 30 and 20°S, is one of the fundamentalhigh-productivity systems of the world ocean. The BUS has previously been studied in terms of primaryproductivity and ecology over glacial-interglacial timescales; however, the response and coupling with thebenthic environment have received little attention. Here, for the ?rst time, we present a high-resolutionreconstruction of the BUS highlighting the link between surface and benthic productivity and their responseto climatic and oceanographic changes over the last 70 ka. The study is based on benthic foraminiferal faunalanalysis together with analyses of diatom assemblages, grain size of the terrigenous fraction, and stable Oand C isotopic and bulk biogenic components of core GeoB3606-1. We reveal signi?cant shifts in benthicforaminiferal assemblage composition. Tight coupling existed between the surface and bottom waterenvironment especially throughout marine isotope stages 4 and 3 (MIS4 and MIS3). Due to the high exportproduction, the site has essentially experienced continuous low oxygen conditions; however, there are timeperiods where the hypoxic conditions were even more notable. Two of these severe hypoxic periods wereduring parts of MIS4 and MIS3 where we ?nd an inverse relationship between diatom and benthicforaminifera accumulation, meaning that during times of extremely high phytodetritus export we notestrongly suppressed benthic productivity. We also stress the importance of food source for the benthosthroughout the record. Shifts in export productivity are attributed not only to upwelling intensity and?lament front position, but also, regional-global climatic and oceanographic changes had signi?cant impacton the BUS dynamics

Rapid bottom-water circulation changes during the last glacial cycle in the coastal low-latitude NE Atlantic

Previous paleoceanographic studies along the NW African margin focused on the dynamics of surface and intermediate waters, whereas little attention has been devoted to deep-water masses. Currently, these deep waters consist mainly of North Atlantic Deep Waters as part of the Atlantic Meridional Overturning Circulation (AMOC). However, this configuration was altered during periods of AMOC collapse. We present a highresolution reconstruction of bottom-water ventilation and current evolution off Mauritania from the last glacial maximum into the early Holocene. Applying redox proxies (Mo, U and Mn) measured on sediments from off Mauritania, we describe changes in deep-water oxygenation and we infer the evolution of deep-water conditions during millennial-scale climate/oceanographic events in the area. The second half of Heinrich Event 1 and the Younger Dryas were recognized as periods of reduced ventilation, coinciding with events of AMOC reduction. We propose that these weakening circulation events induced deficient deep-water oxygenation in the Mauritanian upwelling region, which together with increased productivity promoted reducing conditions and enhanced organic-matter preservation. This is the first time the effect of AMOC collapse in the area is described at high resolution, broadening the knowledge on basin-wide oceanographic changes associated with rapid climate variability during the last deglaciation

Filling and emptying manoeuvres in large pipes. Application to a cast iron pipeline DN400 located in Massamagrell, Valencia, Spain

[ES] Debido a las bolsas de aire que hay en el interior de las tuberías durante los procesos de llenado y vaciado, se producen depresiones o sobrepresiones en el interior de las mismas, capaces de producir serios daños en las instalaciones. Para analizar todas las variables hidráulicas en las maniobras de llenado y vaciado, se opta por la aplicación de un modelo matemático, el cual es capaz de simular con exactitud el comportamiento de ambos fluidos, tanto la columna de agua como la bolsa de aire. El modelo propuesto por los autores ya ha sido validado en pequeñas instalaciones de laboratorio. En este trabajo, se pretende validar el modelo matemático en una instalación real de grandes dimensiones. Concretamente, se trata de una conducción de diámetro DN400, ubicada en Massamagrell (Valencia), donde se analizan las maniobras de llenado y de vaciado. Finalmente, se comparan los resultados que proporciona el modelo con las mediciones realizadas por la Empresa Mixta Metropolitana S.A. (EMIMET),[EN] Air pockets inside hydraulic installations during filling and emptying processes can generate pressure surges and negative pressure, respectively. Serious damages can be occurred in pipelines. In order to analyse hydraulic variables in filling and emptying operations, the selection of a mathematical model is chosen, which is suitable of simulating accurately the behaviour of both fluids (water and air) in pressurized water systems. The mathematical model proposed by the authors has been validated in small laboratory facilities. The aim of this work is to validate the mathematical model in current pipeline installations with large both nominal diameter and length. The pipeline is a nominal diameter DN400, and is located in Massamagrell, Valencia, Spain. The filling and emptying manoeuvres in the selected pipeline are performed by the Empresa Mixta Metropolitana S.A. (EMIMET). A good agreement is obtained when a comparison of absolute pressure and water flow is carried out between the maRomero, G.; Coronado-Hernández, O.; Fuertes-Miquel, V.; Ponz-Carcelén, R. (2020). Maniobras de llenado y vaciado en grandes conducciones. Aplicación a una tubería de fundición DN400 en Massamagrell (Valencia, España). Ingeniería del agua. 24(1):15-29. https://doi.org/10.4995/ia.2020.12184OJS1529241AWWA American Water Works Association 2001. Manual of Water Supply Practices M51: Air-Release, Air-Vacuum, and Combination Air Valves, American Water Works Association, Denver, CO, USA.Apollonio, C., Balacco, G., Fontana, N., Giugni, M., Marini, G., Piccinni, A.F. 2016. Hydraulic transients caused by air expulsion during rapid filling of undulating pipelines. Water, 8(1), 25, https://doi.org/10.3390/w8010025Balacco, G., Apollonio, C., Piccinni, A.F. 2015. Experimental analysis of air valve behaviour during hydraulic transients. Journal of Applied Water Engineering Research, 3(1), 3-11, https://doi.org/10.1080/23249676.2015.1032374Besharat, M., Coronado-Hernández, O.E., Fuertes-Miquel, V.S., Viseu, M.T., Ramos, H.M. 2018. Backflow air and pressure analysis in emptying pipeline containing entrapped air pocket. Urban Water Journal, 15(8), 769-779, https://doi.org/10.1080/1573062X.2018.1540711Besharat, M., Coronado-Hernández, O.E., Fuertes-Miquel, V.S., Viseu, M.T, Ramos, H.M. 2019. Computational fluid dynamics for sub-atmospheric pressure analysis in pipe drainage. Journal of Hydraulic Research. https://doi.org/10.1080/00221686.2019.1625819Chaudhry, M.H. 1989. Application of lumped and distributed approaches for hydraulic transient analysis. Proceedings of the International Congress on Cases and Accidents in Fluid Systems, ANAIS, Polytechnic University of Sao Paulo, Brasil.Coronado-Hernández, O.E., Fuertes-Miquel, V.S., Besharat, M., Ramos, H.M. 2017. Experimental and numerical analysis of a water emptying pipeline using different air valves, Water, 9(2), 98, https://doi.org/10.3390/w9020098Coronado-Hernández, O.E., Fuertes-Miquel, V.S., Besharat, M, Ramos, H.M. 2018a. Subatmospheric pressure in a water draining pipeline with an air pocket. Urban Water Journal, 15(4), pp. 346-352, https://doi.org/10.1080/1573062X.2018.1475578Coronado-Hernández, O.E., Fuertes-Miquel, V.S., Iglesias-Rey, P.L., Martínez-Solano, F.J. 2018b. Rigid water column model for simulating the emptying process in a pipeline using pressurized air. Journal of Hydraulic Engineering, 144(4), https://doi.org/10.1061/(ASCE)HY.1943-7900.0001446Coronado-Hernández, O.E., Besharat, M., Fuertes-Miquel, V.S., Ramos, H.M. 2019. Effect of a commercial air valve on rapid filling of a single pipeline: numerical and experimental analysis. Water, 11(9), 1814, https://doi.org/10.3390/w11091814Fuertes-Miquel, V.S. 2001, Hydraulic transients with entrapped air pockets, PhD Thesis, Department of Hydraulic Engineering, Polytechnic University of Valencia, Editorial Universitat Politècnica de València.Fuertes-Miquel, V.S., López-Jiménez, P.A., Martínez-Solano, F.J., López-Patiño, G. 2016. Numerical modelling of pipelines with air pockets and air valves. Canadian Journal of Civil Engineering, 43(12), 1052-1061, https://doi.org/10.1139/cjce-2016-0209Fuertes-Miquel, V.S., Coronado-Hernández, O.E., Iglesias-Rey, P.L., Mora-Meliá, D. 2019a. Transient phenomena during the emptying process of a single pipe with water-air interaction. Journal of Hydraulic Research, 57(3), 318-326, https://doi.org/10.1080/00221686.2018.1492465Fuertes-Miquel, V.S., Coronado-Hernández, O.E., Mora-Meliá, D., Iglesias-Rey, P.L. 2019b. Hydraulic modeling during filling and emptying processes in pressurized pipelines: a literature review. Urban Water Journal, 16(4), pp. 299-311, https://doi.org/10.1080/1573062X.2019.1669188Hope, P., Papworth, M.U. 1980. Fire main failures due to rapid priming of dry lines. Proceedings of the 3rd International Conference on Pressure Surges, BHRA, Canterbury, Inglaterra, pp. 381-390.Izquierdo, J., Fuertes, V.S., Cabrera, E., Iglesias, P.L., García-Serra, J. 1999. Pipeline startup with entrapped air. Journal of Hydraulic Research, 37(5), 579-590. https://doi.org/10.1080/00221689909498518Jönsson, L. 1985. Maximun transient pressures in a conduit with check valve and air entrainment. Proceedings of the International Conference on Hydraulics of Pumping Stations, Manchester, Inglaterra, pp. 55-76.Laanearu, J., Annus, I., Koppel, T., Bergant, A., Vučkovič, S., Hou, Q., Tijsseling, A.S., Anderson, A, van't Westende, J.M.C. 2012. Emptying of large-scale pipeline by pressurized air. Journal of Hydraulic Engineering, 138(12), 1090-1100. https://doi.org/10.1061/(ASCE)HY.1943-7900.0000631León, A., Ghidaoui, M., Schmidt, A., García, M. 2010. A robust two-equation model for transient-mixed flows. Journal of Hydraulic Research, 48(1), 44-56, https://doi.org/10.1080/00221680903565911Liou, C., Hunt, W.A. 1996. Filling of pipelines with undulating elevation profiles. Journal of Hydraulic Engineering, 122(10), 534-539, https://doi.org/10.1061/(ASCE)07339429(1996)122:10(534)Malekpour, A., Karney, B.W., Nault, J. 2015. Physical understanding of sudden pressurization of pipe systems with entrapped air: energy auditing approach. Journal of Hydraulic Engineering, 142(2). https://doi.org/10.1061/(ASCE)HY.1943-7900.0001067Martins, S.C., Ramos, H.M., Almeida, A.B. 2015. Conceptual analogy for modelling entrapped air action in hydraulic systems. Journal of Hydraulic Research, 53(5), 678-686. https://doi.org/10.1080/00221686.2015.1077353Ramezani, L., Karney, B., Malekpour, A. 2016. The challenge of air valves: a selective critical literature review. Journal of Water Resources Planning and Management, 141(10). https://doi.org/10.1061/(ASCE)WR.1943-5452.0000530Tijsseling, A.S., Hou, Q., Bozkus, Z, Laanearu, J. 2016. Improved one-dimensional models for rapid emptying and filling of pipelines. Journal of Pressure Vessel Technology. 138(3), 031301. https://doi.org/10.1115/1.4031508Trindade, B.C., Vasconcelos, J.G. 2013. Modeling of water pipeline filling events accounting for air phase interactions. Journal of Hydraulic Engineering, 139(9). https://doi.org/10.1061/(ASCE)HY.1943-7900.0000757Vasconcelos, J.G., Wright, S.J. 2008. Rapid flow startup in filled horizontal pipelines. Journal of Hydraulic Engineering, 134(7), 984-992. https://doi.org/10.1061/(ASCE)0733-9429(2008)134:7(984)Wylie, E., Streeter, V. 1993. Fluid transients in systems. Ed. Prentice Hall, Englewood Cliffs, New Jersey, USA

Which blazars are neutrino loud?

Protons accelerated in the cores of active galactic nuclei can effectively produce neutrinos only if the soft radiation background in the core is sufficiently high. We find restrictions on the spectral properties and luminosity of blazars under which they can be strong neutrino sources. We analyze the possibility that neutrino flux is highly beamed along the rotation axis of the central black hole. The enhancement of neutrino flux compared to GeV gamma-ray flux from a given source makes the detection of neutrino point sources more probable. At the same time the smaller open angle reduces the number of possible neutrino-loud blazars compared to the number of gamma-ray loud ones. We present the table of 15 blazars which are the most likely candidates for the detection by future neutrino telescopes.Comment: 9 pages, 5 figures, version to be published in PR

New hadrons as ultra-high energy cosmic rays

Ultra-high energy cosmic ray (UHECR) protons produced by uniformly distributed astrophysical sources contradict the energy spectrum measured by both the AGASA and HiRes experiments, assuming the small scale clustering of UHECR observed by AGASA is caused by point-like sources. In that case, the small number of sources leads to a sharp exponential cutoff at the energy E<10^{20} eV in the UHECR spectrum. New hadrons with mass 1.5-3 GeV can solve this cutoff problem. For the first time we discuss the production of such hadrons in proton collisions with infrared/optical photons in astrophysical sources. This production mechanism, in contrast to proton-proton collisions, requires the acceleration of protons only to energies E<10^{21} eV. The diffuse gamma-ray and neutrino fluxes in this model obey all existing experimental limits. We predict large UHE neutrino fluxes well above the sensitivity of the next generation of high-energy neutrino experiments. As an example we study hadrons containing a light bottom squark. These models can be tested by accelerator experiments, UHECR observatories and neutrino telescopes.Comment: 17 pages, revtex style; v2: shortened, as to appear in PR

Evaluating How Potential Pool of Partners Can Join Together in Different Types of Long Term Collaborative Networked Organizations

International audienceThe considerable benefits brought up by strategic alliances and diverse types of long term Collaborative Networked Organizations (CNOs) are nowadays widely recognized. There is an increasing demand in the industrial world for concretely implement new forms of collaborations. For example, demand often comes from pre-existent form of clusters or local productive arrangements, that want to evolve to more efficient forms of collaboration, or from small and medium enterprises that are facing a crisis, and look at collaboration with other enterprises as almost the last chance to survive. In general, variety of motivations in collaborating implies variety of missions of potential collaborations, that in turn requires the choice of an appropriate form of Collaborative Network aligned to the mission statement. This paper addresses the problem to define a methodology for analyzing potential pool of partners and for identifing the mission, the form, the governance structure and the value drivers of long term strategic alliance that would bring highest benefits to the partners. Three different forms of CNOs are considered: the Virtual organizations Breeding Environment (VBE), the Virtual Development Office (VDO) and the T-Holding

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02

Search for R-parity violating supersymmetry with displaced vertices in proton-proton collisions at root s=8 TeV

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