The ATLAS Liquid Argon (LAr) calorimeters produce a total of 182,486 signals which are digitized and processed by the front-end and back-end electronics at every triggered event. In addition, the ...front-end electronics is summing analog signals to provide coarsely grained energy sums, called trigger towers, to the first-level trigger system, which is optimized for nominal LHC luminosities. However, the pile-up noise expected during the high luminosity phases of LHC will be increased by factors of 3–7. An improved spatial granularity of the trigger primitives is therefore proposed in order to improve the identification performance for trigger signatures, like electrons or photons, at high background rejection rates. The general concept of the upgraded LAr calorimeter readout together with the various electronics components to be developed for such a complex system is presented. The R&D activities and architectural studies undertaken by the ATLAS LAr Calorimeter group are described.
The Phase-I trigger readout electronics upgrade of the ATLAS Liquid Argon calorimeters enhances the physics reach of the experiment during the upcoming operation at increasing Large Hadron Collider ...luminosities. The new system, installed during the second Large Hadron Collider Long Shutdown, increases the trigger readout granularity by up to a factor of ten as well as its precision and range. Consequently, the background rejection at trigger level is improved through enhanced filtering algorithms utilizing the additional information for topological discrimination of electromagnetic and hadronic shower shapes. This paper presents the final designs of the new electronic elements, their custom electronic devices, the procedures used to validate their proper functioning, and the performance achieved during the commissioning of this system.
High latitude ocean gateway changes are thought to play a key role in Cenozoic climate evolution. However, the underlying ocean dynamics are poorly understood. Here we use a fully coupled ...atmosphere-ocean model to investigate the effect of ocean gateway formation that is associated with the subsidence of the Greenland-Scotland Ridge. We find a threshold in sill depth (∼50 m) that is linked to the influence of wind mixing. Sill depth changes within the wind mixed layer establish lagoonal and estuarine conditions with limited exchange across the sill resulting in brackish or even fresher Arctic conditions. Close to the threshold the ocean regime is highly sensitive to changes in atmospheric CO
and the associated modulation in the hydrological cycle. For larger sill depths a bi-directional flow regime across the ridge develops, providing a baseline for the final step towards the establishment of a modern prototype North Atlantic-Arctic water exchange.
During the early to mid‐Miocene, benthic δ18O records indicate large ice volume fluctuations of the Antarctic ice sheet (AIS) on multiple timescales. Hitherto, research has mainly focused on how CO2 ...and insolation changes control an equilibrated AIS. However, transient AIS dynamics remain largely unexplored. Here, we study Miocene AIS variability, using an ice sheet‐shelf model forced by climate model output with various CO2 levels and orbital conditions. Besides equilibrium simulations, we conduct transient experiments, gradually changing the forcing climate state over time. We show that transient AIS variability is substantially smaller than equilibrium differences. This reduces the contribution of the AIS to δ18O fluctuations by more than two thirds on a 40‐kyr timescale, hence requiring a larger contribution by deep‐sea‐temperature variability. The growth rates are much slower than the decay rates, which ensures variability around a preferred small state. Finally, if the bedrock topography enlarges the West Antarctic land surface, AIS self‐sustenance increases.
Key Points
The contribution of transient Antarctic ice sheet variations to Miocene δ18O signals is smaller than indicated by equilibrium differences
Transient ice volume variability is centered around a preferred small state and is dependent on the timescale of the forcing
Enlarging the West Antarctic land surface increases the self‐sustenance of the Miocene Antarctic ice sheet, decreasing the variability
The Weddell Sea is a main location of bottom water formation and, thus, an important component of global ocean circulation. In this study we examine the ocean and climatic responses to a shelf ...progradation induced by ice sheet advance and glacially transported sediments during the Miocene, using a general circulation model. Our investigations show that relative to a Miocene standard bathymetry, a farther southerly placed shelf break, as reconstructed in a state‐of‐the‐art bathymetry for the Weddell Sea, enables enhanced Antarctic Bottom Water (AABW) formation and gyre transport during the middle Miocene for both relatively high and low atmospheric CO2 concentrations. Furthermore, CO2 sensitivity experiments show that an atmospheric CO2 decline for a setup with the southerly placed shelf break of a new bathymetry has only a minor impact on AABW formation, while the standard setup shows an increase. In combination, these impacts may explain the pronounced deep water formation in the southern high latitudes from the middle Miocene to the late Miocene.
Key Points
Middle Miocene paleo‐ocean circulation is sensitive to the position of the shelf break in the Weddell Sea
Relative to a standard Miocene model bathymetry, a southerly placed shelf break in the Weddell Sea causes enhanced deep water formation
Sensitivity of southern source water component to CO2 changes depends on the position of the shelf break
Antimicrobial resistance is one of the biggest health and subsequent economic threat humanity faces. Next to massive global awareness campaigns, governments and NGOs alike stress the need for new ...innovative strategies to treat microbial infections. One of such innovative strategies is the photodynamic antimicrobial chemotherapy (PACT) in which the synergistic effects of photons and drugs are exploited. While many promising reports are available, PACT – and especially the drug-design part behind – is still in its infancy. Common best-practice rules, such as the EUCAST or CLSI protocols for classic antibiotics as well as high-throughput screenings, are missing, and this, in turn, hampers the identification of hit structures. Hit-like structures might come from synthetic approaches or from natural sources. They are identified via activity-guided synthesis or isolation strategies. As source for new antimicrobials, fungi are highly ranked. They share the same ecological niche with many other microbes and consequently established chemical strategies to combat with the others. Recently, in members of the Cortinariaceae, especially of the subgenus
Dermocybe
, photoactive metabolites were detected. To study their putative photoantimicrobial effect, a photoantimicrobial high-throughput screening (HTS) based on The European Committee on Antimicrobial Susceptibility Testing (EUCAST) was established. After validation, the established HTS was used to evaluate a sample set containing six colorful representatives from the genus
Cortinarius
(i.e.,
Cortinarius callisteus
,
C. rufo-olivaceus
,
C. traganus
,
C. trivialis
,
C. venetus
, and
C. xanthophyllus
). The assay is built on a uniform, light-emitting diode (LED)-based light irradiation across a 96-well microtiter plate, which was achieved by a pioneering arrangement of the LEDs. The validation of the assay was accomplished with well-known photoactive drugs, so-called photosensitizers, utilizing six distinct emission wavelengths (λ
exc
= 428, 478, 523, 598, or 640 nm) and three microbial strains (
Candida albicans
,
Staphylococcus aureus
, and
Escherichia coli
). Evaluating the extracts of six
Cortinarius
species revealed two highly promising species, i.e.,
C. rufo-olivaceus
and
C. xanthophyllus.
Extracts from the latter were photoactive against the Gram-positive
S. aureus
(
c
= 7.5 μg/ml,
H
= 30 J/cm
2
, λ = 478 nm) and the fungus
C. albicans
(
c
= 75 μg/ml,
H
= 30 J/cm
2
, λ = 478 nm).
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