201 research outputs found
Heisenberg-Limited Quantum Metrology without Ancilla
The asymptotic theory of quantum channel estimation has been well
established, but in general noiseless and controllable ancilla is required for
attaining the ultimate limit in the asymptotic regime. Little is known about
the metrological performance without noiseless ancilla, which is more relevant
in practical circumstances. In this work, we present a novel theoretical
framework to address this problem, bridging quantum metrology and the
asymptotic theory of quantum channels. Leveraging this framework, we prove
sufficient conditions for achieving the Heisenberg limit with repeated
application of the channel to estimate, both with and without applying
interleaved unitary control operations. For the latter case, we design an
algorithm to identify the control operation. Finally, we analyze several
intriguing examples by our approach.Comment: 15 pages + 2 figure
Suppression of nano-channel ion conductance by electro-osmotic flow in nano-channels with weakly overlapping electrical double layers
This theoretical study investigates the nonlinear ionic current-voltage
characteristics of nano-channels that have weakly overlapping electrical double
layers. Numerical simulations as well as a 1-D mathematical model are developed
to reveal that the electro-osmotic flow (EOF) interplays with the
concentration-polarization process and depletes the ion concentration inside
the channels, thus significantly suppressing the channel conductance. The
conductance may be restored at high electrical biases in the presence of
recirculating vortices within the channels. As a result of the EOF-driven ion
depletion, a limiting-conductance behavior is identified, which is
intrinsically different from the classical limiting-current behavior
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Mechanism of Exact Transition between Cationic and Anionic Redox Activities in Cathode Material Li2FeSiO4.
The discovery of anion redox activity is promising for boosting the capacity of lithium ion battery (LIB) cathodes. However, fundamental understanding of the mechanisms that trigger the anionic redox is still lacking. Here, using hybrid density functional study combined with experimental soft X-ray absorption spectroscopy (sXAS) measurements, we unambiguously proved that Li(2- x)FeSiO4 performs sequent cationic and anionic redox activity through delithiation. Specifically, Fe2+ is oxidized to Fe3+ during the first Li ion extraction per formula unit (f.u.), while the second Li ion extraction triggered the oxygen redox exclusively. Cationic and anionic redox result in electron and hole polaron states, respectively, explaining the poor conductivity of Li(2- x)FeSiO4 noted by previous experiments. In contrast, other cathode materials in this family exhibit diversity of the redox process. Li2MnSiO4 shows double cationic redox (Mn2+-Mn4+) during the whole delithiation, while Li2CoSiO4 shows simultaneous cationic and anionic redox. The present finding not only provides new insights into the oxygen redox activity in polyanionic compounds for rechargeable batteries but also sheds light on the future design of high-capacity rechargeable batteries
Efficient 2-Round General Perfectly Secure Message Transmission: A Minor Correction to Yang and Desmedt\u27s Protocol
At Asiacrypt~\u2710, Yang and Desmedt proposed a number of perfectly secure message transmission protocols in the general adversary model. However, there is a minor flaw in the 2-round protocol in an undirected graph to transmit multiple messages. A small correction solves the problem. Here we fix the protocol and prove its security
Interlayer Interactions in Anisotropic Atomically-thin Rhenium Diselenide
Recently, two-dimensional (2D) materials with strong in-plane anisotropic
properties such as black phosphorus have demonstrated great potential for
developing new devices that can take advantage of its reduced lattice symmetry
with potential applications in electronics, optoelectronics and
thermoelectrics. However, the selection of 2D material with strong in-plane
anisotropy has so far been very limited and only sporadic studies have been
devoted to transition metal dichalcogenides (TMDC) materials with reduced
lattice symmetry, which is yet to convey the full picture of their optical and
phonon properties, and the anisotropy in their interlayer interactions. Here,
we study the anisotropic interlayer interactions in an important TMDC 2D
material with reduced in-plane symmetry - atomically thin rhenium diselenide
(ReSe2) - by investigating its ultralow frequency interlayer phonon vibration
modes, the layer dependent optical bandgap, and the anisotropic
photoluminescence (PL) spectra for the first time. The ultralow frequency
interlayer Raman spectra combined with the first study of polarization-resolved
high frequency Raman spectra in mono- and bi-layer ReSe2 allows deterministic
identification of its layer number and crystal orientation. PL measurements
show anisotropic optical emission intensity with bandgap increasing from 1.26
eV in the bulk to 1.32 eV in monolayer, consistent with the theoretical results
based on first-principle calculations. The study of the layer-number dependence
of the Raman modes and the PL spectra reveals the relatively weak van der Waals
interaction and 2D quantum confinement in atomically-thin ReSe2.Comment: 17 pages, 5 figures, supplementary informatio
Increased expression of the pluripotency markers sex-determining region Y-box 2 and Nanog homeobox in ovarian endometriosis
BACKGROUND: The precise etiology of endometriosis is not fully understood; the involvement of stem cells theory is a new hypothesis. Related studies mainly focus on stemness-related genes, and pluripotency markers may play a role in the etiology of endometriosis. We aimed to analyze the transcription pluripotency factors sex-determining region Y-box 2 (SOX2), Nanog homeobox (NANOG), and octamer-binding protein 4 (OCT4) in the endometrium of reproductive-age women with and without ovarian endometriosis. METHODS: We recruited 26 women with laparoscopy-diagnosed ovarian endometriosis (endometriosis group) and 16 disease-free women (control group) to the study. Endometrial and endometriotic samples were collected. SOX2, NANOG, and OCT4 expression were analyzed with quantitative real-time polymerase chain reaction, western blotting, and immunohistochemistry. RESULTS: Compared to the control group, SOX2 mRNA and protein expression was significantly higher in the eutopic endometrium of participants in the endometriosis group. In the endometriosis group, SOX2 and NANOG mRNA and protein expression were significantly increased in ectopic endometrium compared with eutopic endometrium; there was a trend towards lower OCT4 mRNA expression and higher OCT4 protein expression in ectopic endometrium. CONCLUSIONS: The transcription pluripotency factors SOX2 and NANOG were overexpression in ovarian endometriosis, their role in pathogenesis of endometriosis should be further studied
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