122 research outputs found
Studies for New Experiments at the CERN M2 Beamline within "Physics Beyond Colliders": AMBER/COMPASS++, NA64mu, MuonE
The "Physics Beyond Colliders (PBC)" study explores fundamental physics
opportunities at the CERN accelerator complex complementary to collider
experiments. Three new collaborations aim to exploit the M2 beamline in the
North Area with existing high-intensity muon and hadron beams, but also aspire
to go beyond the current M2 capabilities with a RF-separated, high intensity
hadron beam, under study. The AMBER/COMPASS++ collaboration proposes an
ambitious program with a measurement of the proton radius with muon beams, as
well as QCD-related studies from pion PDFs / Drell-Yan to cross section
measurements for dark sector searches. Assuming feasibility of the RF-separated
beam, the spectrum of strange mesons would enter a high precision era while
kaon PDFs as well as nucleon TMDs would be accessible via Drell-Yan reactions.
The NA64mu collaboration proposes to search for dark sector mediators such as a
dark scalar A' or a hypothetical Z_mu using the M2 muon beam and complementing
their on-going A' searches with electron beams. The MuonE collaboration intends
to assess the hadronic component of the vacuum polarization via elastic mu-e
scattering, the dominant uncertainty in the determination of (g-2)_mu. An
overview of the three new experimental programs will be presented together with
implications for the M2 beamline and the experimental area EHN2, based on the
studies of the PBC "Conventional Beams" Working Group.Comment: MENU 2019 Proceedings, 7 page
The excitation of 5-min oscillations in the solar corona
We aim to study excitation of the observed 5-min oscillations in the solar
corona by localized pulses that are launched in the photosphere. We solve the
full set of nonlinear one-dimensional Euler equations numerically for the
velocity pulse propagating in the solar atmosphere that is determined by the
realistic temperature profile. Numerical simulations show that an initial
velocity pulse quickly steepens into a leading shock, while the nonlinear wake
in the chromosphere leads to the formation of consecutive pulses. The time
interval between arrivals of two neighboring pulses to a detection point in the
corona is approximately 5 min. Therefore, the consecutive pulses may result in
the 5-min oscillations that are observed in the solar corona. The 5-min
oscillations observed in the solar corona can be explained in terms of
consecutive shocks that result from impulsive triggers launched within the
solar photosphere by granulation and/or reconnection.Comment: 5 pages, 2 figures, accepted in A&
MHD waves in sunspots
The review addresses the spatial frequency morphology of sources of sunspot
oscillations and waves, including their localization, size, oscillation
periods, height localization with the mechanism of cut-off frequency that forms
the observed emission variability. Dynamic of sunspot wave processes, provides
the information about the structure of wave fronts and their time variations,
investigates the oscillation frequency transformation depending on the wave
energy is shown. The initializing solar flares caused by trigger agents like
magnetoacoustic waves, accelerated particle beams, and shocks are discussed.
Special attention is paid to the relation between the flare reconnection
periodic initialization and the dynamics of sunspot slow magnetoacoustic waves.
A short review of theoretical models of sunspot oscillations is provided.Comment: 20 pages, 6 figures, Chapter in AGU Monograph (in press), Review
articl
The TESS-Keck Survey. XV. Precise Properties of 108 TESS Planets and Their Host Stars
We present the stellar and planetary properties for 85 TESS Objects of
Interest (TOIs) hosting 108 planet candidates which comprise the TESS-Keck
Survey (TKS) sample. We combine photometry, high-resolution spectroscopy, and
Gaia parallaxes to measure precise and accurate stellar properties. We then use
these parameters as inputs to a lightcurve processing pipeline to recover
planetary signals and homogeneously fit their transit properties. Among these
transit fits, we detect significant transit-timing variations among at least
three multi-planet systems (TOI-1136, TOI-1246, TOI-1339) and at least one
single-planet system (TOI-1279). We also reduce the uncertainties on
planet-to-star radius ratios across our sample, from a median
fractional uncertainty of 8.8 among the original TOI Catalog values to
3.0 among our updated results. With this improvement, we are able to
recover the Radius Gap among small TKS planets and find that the topology of
the Radius Gap among our sample is broadly consistent with that measured among
Kepler planets. The stellar and planetary properties presented here will
facilitate follow-up investigations of both individual TOIs and broader trends
in planet properties, system dynamics, and the evolution of planetary systems.Comment: Accepted at The Astronomical Journal; 21 pages, 9 figure
The TESS-Keck Survey. XVI. Mass Measurements for 12 Planets in Eight Systems
With JWST's successful deployment and unexpectedly high fuel reserves,
measuring the masses of sub-Neptunes transiting bright, nearby stars will soon
become the bottleneck for characterizing the atmospheres of small exoplanets
via transmission spectroscopy. Using a carefully curated target list and more
than two years' worth of APF-Levy and Keck-HIRES Doppler monitoring, the
TESS-Keck Survey is working toward alleviating this pressure. Here we present
mass measurements for 11 transiting planets in eight systems that are
particularly suited to atmospheric follow-up with JWST. We also report the
discovery and confirmation of a temperate super-Jovian-mass planet on a
moderately eccentric orbit. The sample of eight host stars, which includes one
subgiant, spans early-K to late-F spectral types ( 5200--6200
K). We homogeneously derive planet parameters using a joint photometry and
radial velocity modeling framework, discuss the planets' possible bulk
compositions, and comment on their prospects for atmospheric characterization.Comment: Accepted for publication in The Astronomical Journal on 2023-Jun-22.
60 pages, 17 Tables, 28 Figure
Virology Experts in the Boundary Zone Between Science, Policy and the Public: A Biographical Analysis
This article aims to open up the biographical black box of three experts working in the boundary zone between science, policy and public debate. A biographical-narrative approach is used to analyse the roles played by the virologists Albert Osterhaus, Roel Coutinho and Jaap Goudsmit in policy and public debate. These figures were among the few leading virologists visibly active in the Netherlands during the revival of infectious diseases in the 1980s. Osterhaus and Coutinho in particular are still the key figures today, as demonstrated during the outbreak of novel influenza A (H1N1). This article studies the various political and communicative challenges and dilemmas encountered by these three virologists, and discusses the way in which, strategically or not, they handled those challenges and dilemmas during the various stages of the field’s recent history. Important in this respect is their pursuit of a public role that is both effective and credible. We will conclude with a reflection on the H1N1 pandemic, and the historical and biographical ties between emerging governance arrangements and the experts involved in the development of such arrangements
Calibration of the B/Ca proxy in the planktic foraminifer Orbulina universa to Paleocene seawater conditions
This research is funded by NSF [OCE12-32987] to BH.The B/Ca ratio of planktic foraminiferal calcite, a proxy for the surface ocean carbonate system, displays large negative excursions during the Paleocene-Eocene Thermal Maximum (PETM, 55.9 Ma), consistent with rapid ocean acidification at that time. However, the B/Ca excursion measured at the PETM exceeds a magnitude that modern pH-calibrations can explain. Numerous other controls on the proxy have been suggested, including foraminiferal growth rate and the total concentration of Dissolved Inorganic Carbon (DIC). Here we present new calibrations for B/Ca vs. the combined effects of pH and DIC in the symbiont-bearing planktic foraminifer Orbulina universa, grown in culture solutions with simulated Paleocene seawater elemental composition (high [Ca], low [Mg], and low [B]T). We also investigate the isolated effects of low seawater total boron concentration ([B]T), high [Ca], reduced symbiont photosynthetic activity, and average shell growth rate on O. universa B/Ca in order to further understand the proxy systematics and to determine other possible influences on the PETM records. We find that average shell growth rate does not appear to determine B/Ca in high calcite saturation experiments. In addition, our “Paleocene” calibration shows higher sensitivity than the modern calibration at low [B(OH)4-]/DIC. Given a large DIC pulse at the PETM, this amplification of the B/Ca response can more fully explain the PETM B/Ca excursion. However, further calibrations with other foraminifer species are needed to determine the range of foraminifer species-specific proxy sensitivities under these conditions for quantitative reconstruction of large carbon cycle perturbations.Publisher PDFPeer reviewe
Romania - Polity Contestation and the Resilience of Mainstream Parties
ERC POLCON project funded
Late quaternary sea-ice and sedimentary redox conditions in the eastern Bering Sea – Implications for ventilation of the mid-depth North Pacific and an Atlantic-Pacific seesaw mechanism
On glacial-interglacial and millennial timescales, sea ice is an important player in the circulation and primary productivity of high latitude oceans, affecting regional and global biogeochemical cycling. In the modern North Pacific, brine rejection during sea-ice freezing in the Sea of Okhotsk drives the formation of North Pacific Intermediate Water (NPIW) that ventilates the North Pacific Ocean at 300 m to 1000 m water depth. Glacial intervals of the late Quaternary, however, experienced a deepening of glacial NPIW to at least 2000 m, with the strongest ventilation observed during cold stadial conditions of the last deglaciation. However, the origin of the shifts in NPIW ventilation is poorly understood. Numerical simulations suggest an atmospheric teleconnection between the North Atlantic and the North Pacific, in response to a slowdown or shutdown of the Atlantic meridional overturning circulation. This leads to a build-up of salinity in the North Pacific surface ocean, triggering deep ventilation. Alternatively, increased sea-ice formation in the North Pacific and its marginal seas may have caused strengthened overturning in response to enhanced brine rejection.
Here we use a multi-proxy approach to explore sea-ice dynamics, sedimentary redox chemistry, and benthic ecology at Integrated Ocean Drilling Program Site U1343 in the eastern Bering Sea across the last 40 ka. Our results suggest that brine rejection from enhanced sea-ice formation during early Heinrich Stadial 1 locally weakened the halocline, aiding in the initiation of deep overturning. Additionally, deglacial sea-ice retreat likely contributed to increased primary productivity and expansion of mid-depth hypoxia at Site U1343 during interstadials, confirming a vital role of sea ice in the deglacial North Pacific carbon cycle
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