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Structure of the substrate-engaged SecA-SecY protein translocation machine.
The Sec61/SecY channel allows the translocation of many proteins across the eukaryotic endoplasmic reticulum membrane or the prokaryotic plasma membrane. In bacteria, most secretory proteins are transported post-translationally through the SecY channel by the SecA ATPase. How a polypeptide is moved through the SecA-SecY complex is poorly understood, as structural information is lacking. Here, we report an electron cryo-microscopy (cryo-EM) structure of a translocating SecA-SecY complex in a lipid environment. The translocating polypeptide chain can be traced through both SecA and SecY. In the captured transition state of ATP hydrolysis, SecAs two-helix finger is close to the polypeptide, while SecAs clamp interacts with the polypeptide in a sequence-independent manner by inducing a short β-strand. Taking into account previous biochemical and biophysical data, our structure is consistent with a model in which the two-helix finger and clamp cooperate during the ATPase cycle to move a polypeptide through the channel
Security of Plug-and-Play QKD Arrangements with Finite Resources
The security of a passive plug-and-play QKD arrangement in the case of finite
(resources) key lengths is analysed. It is assumed that the eavesdropper has
full access to the channel so an unknown and untrusted source is assumed. To
take into account the security of the BB84 protocol under collective attacks
within the framework of quantum adversaries, a full treatment provides the
well-known equations for the secure key rate. A numerical simulation keeping a
minimum number of initial parameters constant as the total error sought and the
number of pulses is carried out. The remaining parameters are optimized to
produce the maximum secure key rate. Two main strategies are addressed: with
and without two-decoy-states including the optimization of signal to decoy
relationship
Multiagent-Based Control for Plug-and-Play Batteries in DC Microgrids with Infrastructure Compensation
The influence of the DC infrastructure on the control of power-storage flow in micro- and smart grids has gained attention recently, particularly in dynamic vehicle-to-grid charging applications. Principal effects include the potential loss of the charge–discharge synchronization and the subsequent impact on the control stabilization, the increased degradation in batteries’ health/life, and resultant power- and energy-efficiency losses. This paper proposes and tests a candidate solution to compensate for the infrastructure effects in a DC microgrid with a varying number of heterogeneous battery storage systems in the context of a multiagent neighbor-to-neighbor control scheme. Specifically, the scheme regulates the balance of the batteries’ load-demand participation, with adaptive compensation for unknown and/or time-varying DC infrastructure influences. Simulation and hardware-in-the-loop studies in realistic conditions demonstrate the improved precision of the charge–discharge synchronization and the enhanced balance of the output voltage under 24 h excessively continuous variations in the load demand. In addition, immediate real-time compensation for the DC infrastructure influence can be attained with no need for initial estimates of key unknown parameters. The results provide both the validation and verification of the proposals under real operational conditions and expectations, including the dynamic switching of the heterogeneous batteries’ connection (plug-and-play) and the variable infrastructure influences of different dynamically switched branches. Key observed metrics include an average reduced convergence time (0.66–13.366%), enhanced output-voltage balance (2.637–3.24%), power-consumption reduction (3.569–4.93%), and power-flow-balance enhancement (2.755–6.468%), which can be achieved for the proposed scheme over a baseline for the experiments in question.</p
Security Analysis of an Untrusted Source for Quantum Key Distribution: Passive Approach
We present a passive approach to the security analysis of quantum key
distribution (QKD) with an untrusted source. A complete proof of its
unconditional security is also presented. This scheme has significant
advantages in real-life implementations as it does not require fast optical
switching or a quantum random number generator. The essential idea is to use a
beam splitter to split each input pulse. We show that we can characterize the
source using a cross-estimate technique without active routing of each pulse.
We have derived analytical expressions for the passive estimation scheme.
Moreover, using simulations, we have considered four real-life imperfections:
Additional loss introduced by the "plug & play" structure, inefficiency of the
intensity monitor, noise of the intensity monitor, and statistical fluctuation
introduced by finite data size. Our simulation results show that the passive
estimate of an untrusted source remains useful in practice, despite these four
imperfections. Also, we have performed preliminary experiments, confirming the
utility of our proposal in real-life applications. Our proposal makes it
possible to implement the "plug & play" QKD with the security guaranteed, while
keeping the implementation practical.Comment: 35 pages, 19 figures. Published Versio
Energy flow in a hadronic cascade: Application to hadron calorimetry
The hadronic cascade description developed in an earlier paper is extended to
the response of an idealized fine-sampling hadron calorimeter. Calorimeter
response is largely determined by the transfer of energy from the
hadronic to the electromagnetic sector via production. Fluctuations in
this quantity produce the "constant term" in hadron calorimeter resolution. The
increase of its fractional mean, f_{\rm em}^0 = \vev{E_e}/E, with increasing
incident energy causes the energy dependence of the ratio in a
noncompensating calorimeter. The mean hadronic energy fraction, , was shown to scale very nearly as a power law in : , where GeV for pions, and . It
follows that , where electromagnetic and hadronic
energy deposits are detected with efficiencies and , respectively.
Fluctuations in these quantities, along with sampling fluctuations, are
incorporated to give an overall understanding of resolution, which is different
from the usual treatments in interesting ways. The conceptual framework is also
extended to the response to jets and the difference between and
response.Comment: This paper extends to HEP calorimetry the conceptual framework
developed in Gabriel, Groom Job, Mokhov, and Stevenson, "Energy dependence of
hadronic activity," NIM A 338 (1994) 336-34
The Security of Practical Quantum Key Distribution
Quantum key distribution (QKD) is the first quantum information task to reach
the level of mature technology, already fit for commercialization. It aims at
the creation of a secret key between authorized partners connected by a quantum
channel and a classical authenticated channel. The security of the key can in
principle be guaranteed without putting any restriction on the eavesdropper's
power.
The first two sections provide a concise up-to-date review of QKD, biased
toward the practical side. The rest of the paper presents the essential
theoretical tools that have been developed to assess the security of the main
experimental platforms (discrete variables, continuous variables and
distributed-phase-reference protocols).Comment: Identical to the published version, up to cosmetic editorial change
The theory of parametrically amplified electron-phonon superconductivity
The ultrafast optical manipulation of ordered phases in strongly correlated
materials is a topic of significant theoretical, experimental, and
technological interest. Inspired by a recent experiment on light-induced
superconductivity in fullerenes [Mitrano et al., Nature 530, 2016], we develop
a comprehensive theory of light-induced superconductivity in driven
electron-phonon systems with lattice nonlinearities. In analogy with the
operation of parametric amplifiers, we show how the interplay between the
external drive and lattice nonlinearities lead to significantly enhanced
effective electron-phonon couplings. We provide a detailed and unbiased study
of the nonequilibrium dynamics of the driven system using the real-time Green's
function technique. To this end, we develop a Floquet generalization of the
Migdal-Eliashberg theory and derive a numerically tractable set of quantum
Floquet-Boltzmann kinetic equations for the coupled electron-phonon system. We
study the role of parametric phonon generation and electronic heating in
destroying the transient superconducting state. Finally, we predict the
transient formation of electronic Floquet bands in time- and angle-resolved
photo-emission spectroscopy experiments as a consequence of the proposed
mechanism.Comment: 42 pages, 17 figure
Electrophysiological responses to alcohol cues are not associated with Pavlovian-to-Instrumental Transfer in social drinkers
Peer reviewedPublisher PD
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