3,890 research outputs found
Polaritonic Huang-Rhys Factor: Basic Concepts and Quantifying Light-Matter Interaction in Medium
Huang-Rhys (HR) factor, a dimensionless factor that characterizes
electron-phonon coupling, has been extensively employed to investigate material
properties in various fields. In the same spirit, we present a quantity called
polaritonic HR factor to quantitatively describe the effects of (i)
light-matter coupling induced by permanent dipoles and (ii) dipole self-energy.
The former can be viewed as polaritonic displacements, while the latter is
associated with the electronic coupling shift. In the framework of macroscopic
quantum electrodynamics, the polaritonic HR factor, coupling shift, and
modified light-matter coupling strength in an arbitrary dielectric environment
can be evaluated without free parameters, whose magnitudes are in good
agreement with the previous experimental results. In addition, polaritonic
progression developed in our theory indicates that large polaritonic HR factors
can result in light-matter decoupling, multipolariton formation, and
non-radiative transition. We believe that this study provides a useful
perspective to understand and quantify light-matter interaction in medium
Wide-Dynamic-Range Control of Quantum-Electrodynamic Electron Transfer Reactions in the Weak Coupling Regime
Catalyzing reactions effectively by vacuum fluctuations of electromagnetic
fields is a significant challenge within the realm of chemistry. Different from
most studies based on vibrational strong coupling, we introduce an innovative
catalytic mechanism driven by weakly coupled polaritonic fields. Through the
amalgamation of macroscopic quantum electrodynamics (QED) principles with
Marcus electron transfer (ET) theory, our results reveal that ET reaction rates
can be precisely modulated across a wide dynamic range by controlling the size
and structure of nanocavities. Comparing to QED-driven radiative ET rates in
free space, plasmonic cavities induce substantial rate enhancements spanning
from orders of magnitude ranging from 10^3-fold to 10^1-fold. By contrast,
Fabry-Perot cavities engender rate suppression spanning from 10^{-2}-fold to
10^{-1}-fold. This work overcomes the necessity of using strong light-matter
interactions in QED chemistry, opening up a new era of manipulating QED-based
chemical reactions in a wide dynamic range
Many-Body Coherence in Quantum Transport
In this study, we propose the concept of harnessing quantum coherence to
control electron transport in a many-body system. Combining an open quantum
system technique based on Hubbard operators, we show that many-body coherence
can eliminate the well-known Coulomb staircase and cause strong negative
differential resistance. To explore the mechanism, we analytically derive the
current-coherence relationship in the zero electron-phonon coupling limit.
Furthermore, by incorporating a gate field, we demonstrate the possibility of
constructing a coherence-controlled transistor. This development opens up a new
direction for creating quantum electronic devices based on many-body coherence.Comment: 5 pages, 3 figure
A new time-frequency method to reveal quantum dynamics of atomic hydrogen in intense laser pulses: Synchrosqueezing Transform
This study introduces a new adaptive time-frequency (TF) analysis technique,
synchrosqueezing transform (SST), to explore the dynamics of a laser-driven
hydrogen atom at an {\it ab initio} level, upon which we have demonstrated its
versatility as a new viable venue for further exploring quantum dynamics. For a
signal composed of oscillatory components which can be characterized by
instantaneous frequency, the SST enables rendering the decomposed signal based
on the phase information inherited in the linear TF representation with
mathematical support. Compared with the classical type TF methods, the SST
clearly depicts several intrinsic quantum dynamical processes such as selection
rules, AC Stark effects, and high harmonic generation
Terrestrial water storage anomalies emphasize interannual variations in global mean sea level during 1997-1998 and 2015-2016 El Nino Events
© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Kuo, Y.-N., Lo, M.-H., Liang, Y.-C., Tseng, Y.-H., & Hsu, C.-W. Terrestrial water storage anomalies emphasize interannual variations in global mean sea level during 1997-1998 and 2015-2016 El Nino Events. Geophysical Research Letters, 48(18), (2021): e2021GL094104, https://doi.org/10.1029/2021GL094104.Interannual variations in global mean sea level (GMSL) closely correlate with the evolution of El Niño-Southern Oscillation. However, GMSL differences occur in extreme El Niños; for example, in the 2015–2016 and 1997–1998 El Niños, the peak GMSL during the mature stage of the former (9.00 mm) is almost 2.5 times higher than the latter (3.72 mm). Analyses from satellite and reanalysis data sets show that the disparity in GMSL is primarily due to barystatic (ocean mass) changes. We find that the 2015–2016 event developed not purely as an Eastern Pacific El Niño event but with Central Pacific (CP) El Niño forcing. CP El Niños contribute to a stronger negative anomaly of global terrestrial water storage and subsequent higher barystatic heights. Our results suggest that the mechanism of hydrology-related interannual variations of GMSL should be further emphasized, as more CP El Niño events are projected to occur.This study was supported by a grant of MOST 106-2111-M-002-010-MY4 to National Taiwan University
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FAM129B, an antioxidative protein, reduces chemosensitivity by competing with Nrf2 for Keap1 binding.
BackgroundThe transcription factor Nrf2 is a master regulator of antioxidant response. While Nrf2 activation may counter increasing oxidative stress in aging, its activation in cancer can promote cancer progression and metastasis, and confer resistance to chemotherapy and radiotherapy. Thus, Nrf2 has been considered as a key pharmacological target. Unfortunately, there are no specific Nrf2 inhibitors for therapeutic application. Moreover, high Nrf2 activity in many tumors without Keap1 or Nrf2 mutations suggests that alternative mechanisms of Nrf2 regulation exist.MethodsInteraction of FAM129B with Keap1 is demonstrated by immunofluorescence, colocalization, co-immunoprecipitation and mammalian two-hybrid assay. Antioxidative function of FAM129B is analyzed by measuring ROS levels with DCF/flow cytometry, Nrf2 activation using luciferase reporter assay and determination of downstream gene expression by qPCR and wester blotting. Impact of FAM129B on in vivo chemosensitivity is examined in mice bearing breast and colon cancer xenografts. The clinical relevance of FAM129B is assessed by qPCR in breast cancer samples and data mining of publicly available databases.FindingsWe have demonstrated that FAM129B in cancer promotes Nrf2 activity by reducing its ubiquitination through competition with Nrf2 for Keap1 binding via its DLG and ETGE motifs. In addition, FAM129B reduces chemosensitivity by augmenting Nrf2 antioxidative signaling and confers poor prognosis in breast and lung cancer.InterpretationThese findings demonstrate the important role of FAM129B in Nrf2 activation and antioxidative response, and identify FMA129B as a potential therapeutic target. FUND: The Chang Gung Medical Foundation (Taiwan) and the Ministry of Science and Technology (Taiwan)
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