464 research outputs found
Gabriel T. Csanady : understanding the physics of the ocean
No full textAuthor Posting. © Elsevier B.V., 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Progress In Oceanography 70 (2006): 91-112, doi:10.1016/j.pocean.2006.07.002.Gabriel T. Csanady turned 80 in December 2005 and we celebrate it with this special Progress in Oceanography issue. It comprises 20 papers covering some of the many areas that Gabe contributed significantly throughout his professional career. In this introductory paper we briefly review Gabe’s career as an engineer, meteorologist and oceanographer, and highlight some of his major contributions to oceanography, both as a scientist as well as an educator. But we also use this opportunity to remember and thank Gabe, and his wife Joyce, for being such good friends and mentors to several generations of oceanographers. The authors of the collection of papers in this volume deserve special thanks for their efforts. We also are pleased to acknowledge the support of Progress in Oceanography’s editor, Detlef Quadfasel, and the many anonymous reviewers who generously contributed their time and expertise
Microstructure measurements and estimates of entrainment in the Denmark Strait overflow plume
No full textTo examine processes controlling the entrainment of ambient water into the Denmark Strait overflow (DSO) plume/gravity current, measurements of turbulent dissipation rate were carried out by a quasi-free-falling (tethered) microstructure profiler (MSP). The MSP was specifically designed to collect data on dissipation-scale turbulence and fine thermohaline stratification in an ocean layer located as deep as 3500 m. The task was to perform microstructure measurements in the DSO plume in the lower 300 m depth interval including the bottom mixed layer and the interfacial layer below the non-turbulent ambient water. The MSP was attached to a Rosette water sampler rack equipped with a SeaBird CTDO and an RD Instruments lowered acoustic Doppler current profiler (LADCP). At a chosen depth, the MSP was remotely released from the rack to perform measurements in a quasi-free-falling mode. Using the measured vertical profiles of dissipation, the entrainment rate as well as the bottom and interfacial stresses in the DSO plume were estimated at a location 200 km downstream of the sill at depths up to 1771 m. Dissipation-derived estimates of entrainment were found to be much smaller than bulk estimates of entrainment calculated from the downstream change of the mean properties in the plume, suggesting the lateral stirring due to mesoscale eddies rather than diapycnal mixing as the main contributor to entrainment. Dissipation-derived bottom stress estimates are argued to be roughly one third the magnitude of those derived from log velocity profiles. In the interfacial layer, the Ozmidov scale calculated from turbulence dissipation rate and buoyancy frequency was found to be linearly proportional to the overturning scale extracted from conventional CTD data (the Thorpe scale), with a proportionality constant of 0.76, and a correlation coefficient of 0.77
Monitoring the flow of Atlantic water through the Faroe-Shetland Channel
No full textThis report presents results from an experiment, carried out in 2011-2012 within the EU-THOR project to investigate whether future monitoring of the Atlantic water transport through the Faroe-Shetland Channel might be more efficiently achieved on another section than the traditional Munken-Fair Isle section. The new section is less affected by meso-scale activity and narrower, allowing better horizontal resolution of the mooring array, but the experiment revealed that moving to the new section involved other drawbacks. The experiment also confirmed an earlier conjecture that data from satellite altimetry might provide better estimates of transport variations than estimates based on in situ measurements, solely. Previous efforts to determine the average volume transport of Atlantic water through the channel and its variations have been hampered by lack of information on the thickness variations of the Atlantic layer. Re-evaluating the historical data set, we find that the transport estimates are not significantly affected by assuming that the lower boundary of the Atlantic layer is fixed, equal to the average 5°C-isotherm. Based on the conclusions of this report, we recommend that future in situ monitoring in the channel is re-focused
Huntington's chorea with special reference to its incidence in Malta
No full textHuntington's Chorea is known to be a hereditary degenerative disease of the basal ganglia and of the cortex of the brain. It commonly manifests itself clinically at middle age in the form of choreiform movements or of muscular rigidity, which are often accompanied by mental deterioration. A brief historical overview of this anomaly and hereditary aspects are presented, with special reference to its incidence in Malta. The case material of the study is based upon the observations carried out by the author himself, from normal relatives of affected indiviuals, or gathered from past records at the Attard Mental Hospital since 1861 and at the St. Vincent De Paule Hospital since 1892. Furthermore, several summaries of Maltese case histories are reported and explained according to age, mental manifestations and physical behaviours. The occurences of the disease across Malta are mentioned, whereby the only method of prevention is eugenic control. Of utmost importance is therefore the need for notification of the disease, so that prompt measures could be taken to limit its advance in time.peer-reviewe
Analyse der antreibenden Mechanismen der Transportvariabilität in der Flämischen Passage im westlichen Randstrom des subpolaren Nordatlantiks
No full textThe aim of this study is to analyse the Upper Labrador Sea Water (ULSW) volume transport variability at Flemish Pass and in the Deep Western Boundary Current (DWBC) at 47°N and at 53°N along the topographic slope of the Continental Shelf at the Grand Banks of Newfoundland. In the focus of this study are the physical mechanisms governing the transport variability of ULSW at various timescales using monthly (from 1960-2009) and daily (from 2003-2009) model data from an 8-km resolution numerical ocean model (MITgcm).
In order to quantify the southward USLW volume transport, the modeled monthly outputs were used. The average model transport of ULSW decreases southwards from 6.7 Sv at 53°N to 4.5 Sv at 45°N due to interior pathways in the Labrador Sea and in the Newfoundland Basin. The largest fraction of the total ULSW volume transport goes around Flemish Cap within the Deep Western Boundary Current (70%) but a significant part goes through Flemish Pass (20%). At seasonal and interannual timescales, the temporal evolution of the ULSW volume transport variability at Flemish Pass presents a distinct behavior when compared to the variability in the DWBC at 47°N and to the upstream fluctuations at 53°N. Other physical parameters are taken into consideration for the examination of the behavior of the transport variability at Flemish Pass. These parameters include the North Atlantic Oscillation (NAO) index, the local Ekman transport, the rate of ULSW formation in the Labrador Sea, the position of the North Atlantic Current (NAC) relative to the slope and the averaged transport in the subpolar gyre. The relationship between these physical processes and the ULSW transports at each section is tested using a running correlation method. Weakened or strengthened transport of ULSW through Flemish Pass coincides with the effect either of the local atmospheric forcing or of changes of the NAC’s position. The transport variability in the DWBC at 47°N is caused by upstream flow fluctuations and changes in the rate of ULSW formation.
At high frequencies for periods of T <26 days, the behavior of the ULSW volume transport along the topographic slope between 53°N and 47°N is examined by using the daily model outputs. The presence of the dominant peaks of energy at 24 and 11 days in the Flemish Pass transport of ULSW is likely due to a propagating signal of coastal trapped waves along the topographic slope. The perturbation of the ULSW volume transport signal appears strong close to the topographic slope and decays offshore.Das Ziel dieser Arbeit ist es, die Variabilität des Volumentransports von Oberem Labradorseewasser (ULSW) in der Flämischen Passage und im tiefen westlichen Randstrom (DWBC) bei 47°N und 53°N am Kontinentalabhang entlang der Grand Banks von Neufundland zu untersuchen. Im Fokus dieser Arbeit sind die physikalischen Mechanismen, die verantwortlich sind für die Transportvariabilität von ULSW auf verschiedenen Zeitskalen. Diese werden mit monatlichen (1960-2009) und täglichen (2003-2009) Modelldaten aus einem 8 km Ozeanmodell (MITgcm) untersucht.
Um den südwärtigen ULSW Volumentransport zu quantifizieren, wurden die modellierten monatlichen Modellfelder verwendet. Der durchschnittliche Modelltransport von ULSW verringert sich von 6,7 Sv bei 53°N auf 4,5 Sv bei 45°N durch interne Ausbreitungspfade in der Labradorsee und im Neufundland Becken. Der größte Anteil des gesamten ULSW Volumentransports geht um die Flämische Kappe im tiefen westlichen Randstrom (70%), aber ein erheblicher Teil strömt auch durch die Flämische Passage (20%). Auf saisonalen und zwischenjährlichen Zeitskalen zeigt der ULSW Volumentransport in der Flämischen Passage eine andere Variabilität im Vergleich zur Variabilität im DWBC bei 47°N und zu den stromaufwärts beobachten Schwankungen bei 53°N. Andere physikalische Parameter werden in Betracht gezogen, um das Verhalten der Transportvariabilität in der Flämischen Passage zu erklären. Diese Parameter umfassen die Nordatlantische Oszillation (NAO Index), den lokalen Ekman Transport, die Rate der ULSW Bildung in der Labradorsee, die Position des Nordatlantikstroms (NAC) in Bezug auf den Kontinentalabhang und den gemittelten Transport im Subpolarwirbel. Die Beziehung zwischen diesen physikalischen Prozessen und den ULSW Transporten in jedem untersuchten Schnitt wird unter Verwendung eines Korrelationsverfahrens (running correlation coefficient method) getestet. Schwacher oder starker Transport von ULSW durch die Flämische Passage decken sich mit der Wirkung entweder des lokalen atmosphärischen Antriebs oder Veränderungen der Lage des NAC. Die Transportvariabilität im DWBC bei 47°N wird durch stromaufwärts erzeugte Schwankungen und Änderungen in der Rate der ULSW Bildung verursacht.
Hohen Frequenzen für Perioden von T<26 Tagen, die den ULSW Volumentransport entlang des Kontinentalabhangs zwischen 53°N und 47°N
beeinflussen, werden anhand von täglichen Modelldaten untersucht. Die Hauptspitzen von Energie bei 24 und 11 Tagen in der Flämischen Passage im Transport von ULSW entstehen wahrscheinlich durch ein sich ausbreitendes Signal von Küstenwellen (coastal trapped waves) entlang des Kontinentalabhangs. Die Störung des ULSW Volumetransports ist ausgeprägt nahe des Kontinentalabhangs und verschwindet mit grösserem Abstand zum Hang
Measurement of the t t ¯ H and tH production rates in the H → b b ¯ decay channel using proton-proton collision data at s = 13 TeV
No full textAbstract An analysis of the production of a Higgs boson (H) in association with a top quark-antiquark pair ( t t ¯ H ) or a single top quark (tH) is presented. The Higgs boson decay into a bottom quark-antiquark pair (H → b b ¯ ) is targeted, and three different final states of the top quark decays are considered, defined by the number of leptons (electrons or muons) in the event. The analysis utilises proton-proton collision data collected at the CERN LHC with the CMS experiment at s = 13 TeV in 2016–2018, which correspond to an integrated luminosity of 138 fb −1. The observed t t ¯ H production rate relative to the standard model expectation is 0.33 ± 0.26 = 0.33 ± 0.17(stat) ± 0.21(syst). Additionally, the t t ¯ H production rate is determined in intervals of Higgs boson transverse momentum. An upper limit at 95% confidence level is set on the tH production rate of 14.6 times the standard model prediction, with an expectation of 19.3 − 6.0 + 9.2 . Finally, constraints are derived on the strength and structure of the coupling between the Higgs boson and the top quark from simultaneous extraction of the t t ¯ H and tH production rates, and the results are combined with those obtained in other Higgs boson decay channels
Measurement of the differential t t ¯ production cross section as a function of the jet mass and extraction of the top quark mass in hadronic decays of boosted top quarks
No full textAbstract A measurement of the jet mass distribution in hadronic decays of Lorentz-boosted top quarks is presented. The measurement is performed in the lepton + jets channel of top quark pair production ( t t ¯ ) events, where the lepton is an electron or muon. The products of the hadronic top quark decay are reconstructed using a single large-radius jet with transverse momentum greater than 400 Ge V . The data were collected with the CMS detector at the LHC in proton-proton collisions and correspond to an integrated luminosity of 138 fb - 1 . The differential t t ¯ production cross section as a function of the jet mass is unfolded to the particle level and is used to extract the top quark mass. The jet mass scale is calibrated using the hadronic W boson decay within the large-radius jet. The uncertainties in the modelling of the final state radiation are reduced by studying angular correlations in the jet substructure. These developments lead to a significant increase in precision, and a top quark mass of 173.06 ± 0.84 Ge V
Measurement of the top quark pole mass using +jet events in the dilepton final state in proton-proton collisions at = 13 TeV
No full textInternational audienceA measurement of the top quark pole mass in events where a top quark-antiquark pair () is produced in association with at least one additional jet (+jet) is presented. This analysis is performed using proton-proton collision data at = 13 TeV collected by the CMS experiment at the CERN LHC, corresponding to a total integrated luminosity of 36.3 fb. Events with two opposite-sign leptons in the final state (ee, μμ, eμ) are analyzed. The reconstruction of the main observable and the event classification are optimized using multivariate analysis techniques based on machine learning. The production cross section is measured as a function of the inverse of the invariant mass of the +jet system at the parton level using a maximum likelihood unfolding. Given a reference parton distribution function (PDF), the top quark pole mass is extracted using the theoretical predictions at next-to-leading order. For the ABMP16NLO PDF, this results in = 172.93 ± 1.36 GeV.[graphic not available: see fulltext
Search for CP violation in tH and tH production in multilepton channels in proton-proton collisions at = 13 TeV
No full textThe charge-parity (CP) structure of the Yukawa interaction between the Higgs (H) boson and the top quark is measured in a data sample enriched in the tt¯
H and tH associated production, using 138 fb−1 of data collected in proton-proton collisions at s√
= 13 TeV by the CMS experiment at the CERN LHC. The study targets events where the H boson decays via H → WW or H → ττ and the top quarks decay via t → Wb: the W bosons decay either leptonically or hadronically, and final states characterized by the presence of at least two leptons are studied. Machine learning techniques are applied to these final states to enhance the separation of CP -even from CP -odd scenarios. Two-dimensional confidence regions are set on κt and κ∼
t, which are respectively defined as the CP -even and CP -odd top-Higgs Yukawa coupling modifiers. No significant fractional CP -odd contributions, parameterized by the quantity |fHttCP
| are observed; the parameter is determined to be |fHttCP
| = 0.59 with an interval of (0.24, 0.81) at 68% confidence level. The results are combined with previous results covering the H → ZZ and H → γγ decay modes, yielding two- and one-dimensional confidence regions on κt and κ∼
t, while |fHttCP
| is determined to be |fHttCP
| = 0.28 with an interval of |fHttCP
| < 0.55 at 68% confidence level, in agreement with the standard model CP -even prediction of |fHttCP
| = 0
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