926 research outputs found
RG transport theory for open quantum systems: Charge fluctuations in multilevel quantum dots in and out of equilibrium
We present the real-time renormalization group (RTRG) method as a method to
describe the stationary state current through generic multi-level quantum dots
with a complex setup in nonequilibrium. The employed approach consists of a
very rudiment approximation for the RG equations which neglects all vertex
corrections while it provides a means to compute the effective dot Liouvillian
self-consistently. Being based on a weak-coupling expansion in the tunneling
between dot and reservoirs, the RTRG approach turns out to reliably describe
charge fluctuations in and out of equilibrium for arbitrary coupling strength,
even at zero temperature. We confirm this in the linear response regime with a
benchmark against highly-accurate numerically renormalization group data in the
exemplary case of three-level quantum dots. For small to intermediate bias
voltages and weak Coulomb interactions, we find an excellent agreement between
RTRG and functional renormalization group data, which can be expected to be
accurate in this regime. As a consequence, we advertise the presented RTRG
approach as an efficient and versatile tool to describe charge fluctuations
theoretically in quantum dot systems
P4-PSFP: P4-Based Per-Stream Filtering and Policing for Time-Sensitive Networking
Time-Sensitive Networking (TSN) extends Ethernet to enable real-time
communication, including the Credit-Based Shaper (CBS) for prioritized
scheduling and the Time-Aware Shaper (TAS) for scheduled traffic. Generally,
TSN requires streams to be explicitly admitted before being transmitted. To
ensure that admitted traffic conforms with the traffic descriptors indicated
for admission control, Per-Stream Filtering and Policing (PSFP) has been
defined. For credit-based metering, well-known token bucket policers are
applied. However, time-based metering requires time-dependent switch behavior
and time synchronization with sub-microsecond precision. While TSN-capable
switches support various TSN traffic shaping mechanisms, a full implementation
of PSFP is still not available. To bridge this gap, we present a P4-based
implementation of PSFP on a 100 Gb/s per port hardware switch. We explain the
most interesting aspects of the PSFP implementation whose code is available on
GitHub. We demonstrate credit-based and time-based policing and synchronization
capabilities to validate the functionality and effectiveness of P4-PSFP. The
implementation scales up to 35840 streams depending on the stream
identification method. P4-PSFP can be used in practice as long as appropriate
TSN switches lack this function. Moreover, its implementation may be helpful
for other P4-based hardware implementations that require time synchronization
Entropy Changes upon Double Layer Charging at a (111)-Textured Au Film in Pure 1-Butyl-1-Methylpyrrolidinium Bis[(trifluoromethyl)sulfonyl]imide Ionic Liquid
Die Bedeutung von Stress-aktivierten Proteinkinasen (SAPK) nach 6-Hydroxydopamin-induzierter Apoptose in SH-SY5Y-Zellen
Die Bedeutung von Stress-aktivierten Proteinkinasen (SAPK) nach 6-Hydroxydopamin-induzierter Apoptose in SH-SY5Y-Zellen
Flavor fluctuations in 3-level quantum dots: Generic SU(3)-Kondo fixed point in equilibrium and non-Kondo fixed points in nonequilibrium
We study a -level quantum dot in the singly occupied cotunneling regime
coupled via a generic tunneling matrix to several multi-channel leads in
equilibrium or nonequilibrium. We derive an effective model where also each
reservoir has three channels labelled by the quark flavors , and
with an effective d.o.s. polarized w.r.t. an eight-dimensional -spin
corresponding to the eight generators of . In equilibrium we perform a
standard poor man scaling analysis and show that tunneling via virtual
intermediate states induces flavor fluctuations on the dot which become
-symmetric at a characteristic and exponentially small low-energy scale
. Using the numerical renormalization group (NRG) we study in detail the
linear conductance and confirm the -symmetric Kondo fixed point with
universal conductance for various tunneling setups by tuning the
level spacings on the dot. In contrast to the equilibrium case, we find in
nonequilibrium that the fixed point model is not -symmetric but
characterized by rotated -spins for each reservoir with total vanishing sum.
At large voltage we analyse the -spin magnetization and the current in
golden rule as function of a magnetic field for the isospin of the up/down
quark and the level spacing to the strange quark. As a smoking gun to detect
the nonequilibrium fixed point we find that the curve of zero -spin
magnetization has a particular shape on the dot parameters. We propose that our
findings can be generalized to the case of quantum dots with an arbitrary
number of levels.Comment: 24 pages, 8 figure
Hydrogen Site Lampoldshausen – On-site Production of Green Hydrogen and Technology Transfer from Space Applications
Hydrogen Site Lampoldshausen – On-site Production of Green Hydrogen and Technology Transfer from Space Application
Thinning leads to calving-style changes at Bowdoin Glacier, Greenland
This research has been supported by the Alfred and Flora Spälti Fund and the ETH Zurich Foundation (Sun2ice; grant no. ETH-12 16-2); the Swiss National Science Foundation (grant nos. 200021-153179/1 and PP00P2_183719); the SPI Exploratory Grants 2018 awarded to Fabian Walter and Guillaume Jouvet; the Japanese Ministry of Education, Culture, Sports, Science and Technology through the GRENE Arctic Climate Research Project and the Arctic Challenge for Sustainability (ArCS) project; and by NERC (CALISMO: Calving Laws for Ice Sheet Models; grant no. NE/P011365/1).Ice mass loss from the Greenland ice sheet is the largest single contributor to sea level rise in the 21st century. The mass loss rate has accelerated in recent decades mainly due to thinning and retreat of its outlet glaciers. The diverse calving mechanisms responsible for tidewater glacier retreat are not fully understood yet. Since a tidewater glacier's sensitivity to external forcings depends on its calving style, detailed insight into calving processes is necessary to improve projections of ice sheet mass loss by calving. As tidewater glaciers are mostly thinning, their calving styles are expected to change. Here, we study calving behaviour changes under a thinning regime at Bowdoin Glacier, north-western Greenland, by combining field and remote-sensing data from 2015 to 2019. Previous studies showed that major calving events in 2015 and 2017 were driven by hydro-fracturing and melt-undercutting. New observations from uncrewed aerial vehicle (UAV) imagery and a GPS network installed at the calving front in 2019 suggest ungrounding and buoyant calving have recently occurred as they show (1) increasing tidal modulation of vertical motion compared to previous years, (2) absence of a surface crevasse prior to calving, and (3) uplift and horizontal surface compression prior to calving. Furthermore, an inventory of calving events from 2015 to 2019 based on satellite imagery provides additional support for a change towards buoyant calving since it shows an increasing occurrence of calving events outside of the melt season. The observed change in calving style could lead to a possible retreat of the terminus, which has been stable since 2013. We therefore highlight the need for high-resolution monitoring to detect changing calving styles and numerical models that cover the full spectrum of calving mechanisms to improve projections of ice sheet mass loss by calving.Publisher PDFPeer reviewe
Synthesis and Properties of the First [4.4]Ferrocenophane-1,3,15,17-tetrayne
Building butadiyne bridges: The kinetically stabilized 1,1′-diethynylferrocene, readily prepared from the pentafulvenoid allene 1, can be transformed into the [4.4]ferrocenophane 2 by oxidative coupling. This compound exhibits a remarkably symmetrical structure in which the electrons are delocalized through the butadiyne bridges; in the crystalline state 2 exists in a helical-chiral conformation
Synthese und Eigenschaften des ersten [4.4]Ferrocenophan-1,3,15,17-tetrains
Das aus dem pentafulvenoiden Allen 1 leicht zugängliche, kinetisch stabilisierte 1,1′-Diethinylferrocen lässt sich durch oxidative Kupplung in das [4.4]Ferrocenophan 2 überführen. Diese Verbindung hat eine bemerkenswert symmetrische Struktur, die Elektronen sind über die Butadiinbrücken hinweg delokalisiert, und im Kristall liegt 2 in einer helical-chiralen Konformation vor
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