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"Yang, L"
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Femtosecond electron-phonon lock-in by photoemission and x-ray free-electron laser
The interactions that lead to the emergence of superconductivity in iron-based materials remain a subject of debate. It has been suggested that electron-electron correlations enhance electron-phonon coupling in iron selenide (FeSe) and related pnictides, but direct experimental verification has been lacking. Here we show that the electron-phonon coupling strength in FeSe can be quantified by combining two time-domain experiments into a “coherent lock-in” measurement in the terahertz regime. X-ray diffraction tracks the light-induced femtosecond coherent lattice motion at a single phonon frequency, and photoemission monitors the subsequent coherent changes in the electronic band structure.Comparison with theory reveals a strong enhancement of the coupling strength in FeSe owing to correlation effects. Given that the electron-phonon coupling affects superconductivity exponentially, this enhancement highlights the importance of the cooperative interplay between electron-electron and electron-phonon interactions.
Journal Article
Chemical mapping of a single molecule by plasmon-enhanced Raman scattering
Chemical mapping of a single molecule by optical means down to subnanometre resolution is achieved by spectrally matching the resonance of a nanocavity plasmon to the vibronic transitions of the molecules being studied, using tip-enhanced Raman scattering.
Inner workings of a single molecule
Raman spectroscopy is widely used to identify molecules by detecting their signature molecular vibrations. The technology has been refined to be effective at the single-molecule level by making use of strong localized plasmonic fields that can enhance spectral signals. This study goes further, with the demonstration of a technique related to 'tip-enhanced Raman scattering' (TERS) that allows precise tuning of the plasmon resonance and Raman spectral imaging with a spatial resolution below 1 nm, resolving even the inner structure of a single molecule and its configuration on the surface. The technique opens a new path to photochemistry at the single-molecule level, offering the potential to design, control and engineer the functionality of molecules on demand.
Visualizing individual molecules with chemical recognition is a longstanding target in catalysis, molecular nanotechnology and biotechnology. Molecular vibrations provide a valuable ‘fingerprint’ for such identification. Vibrational spectroscopy based on tip-enhanced Raman scattering allows us to access the spectral signals of molecular species very efficiently via the strong localized plasmonic fields produced at the tip apex
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, which is not adequate for resolving a single molecule chemically. Here we demonstrate Raman spectral imaging with spatial resolution below one nanometre, resolving the inner structure and surface configuration of a single molecule. This is achieved by spectrally matching the resonance of the nanocavity plasmon to the molecular vibronic transitions, particularly the downward transition responsible for the emission of Raman photons. This matching is made possible by the extremely precise tuning capability provided by scanning tunnelling microscopy. Experimental evidence suggests that the highly confined and broadband nature of the nanocavity plasmon field in the tunnelling gap is essential for ultrahigh-resolution imaging through the generation of an efficient double-resonance enhancement for both Raman excitation and Raman emission. Our technique not only allows for chemical imaging at the single-molecule level, but also offers a new way to study the optical processes and photochemistry of a single molecule.
Journal Article
Parity–time symmetry and exceptional points in photonics
Exploiting the interplay between gain, loss and the coupling strength between different optical components creates a variety of new opportunities in photonics to generate, control and transmit light. Inspired by the discovery of real eigenfrequencies for non-Hermitian Hamiltonians obeying parity–time (PT) symmetry, many counterintuitive aspects are being explored, particularly close to the associated degeneracies also known as ‘exceptional points’. This Review explains the underlying physical principles and discusses the progress in the experimental investigation of PT-symmetric photonic systems. We highlight the role of PT symmetry and non-Hermitian dynamics for synthesizing and controlling the flow of light in optical structures and provide a roadmap for future studies and potential applications.This Review discusses recent developments in the area of non-Hermitian physics, and more specifically the special case of non-Hermitian optical systems with parity–time symmetry.
Journal Article
MSBooster: improving peptide identification rates using deep learning-based features
Peptide identification in liquid chromatography-tandem mass spectrometry (LC-MS/MS) experiments relies on computational algorithms for matching acquired MS/MS spectra against sequences of candidate peptides using database search tools, such as MSFragger. Here, we present a new tool, MSBooster, for rescoring peptide-to-spectrum matches using additional features incorporating deep learning-based predictions of peptide properties, such as LC retention time, ion mobility, and MS/MS spectra. We demonstrate the utility of MSBooster, in tandem with MSFragger and Percolator, in several different workflows, including nonspecific searches (immunopeptidomics), direct identification of peptides from data independent acquisition data, single-cell proteomics, and data generated on an ion mobility separation-enabled timsTOF MS platform. MSBooster is fast, robust, and fully integrated into the widely used FragPipe computational platform.
There is a need for accessible ways to improve peptide spectrum match rescoring with deep learning predictions in bottom-up proteomics. Here, the authors demonstrate robust gains in peptide/protein identifications across various experiments, from single cell proteomics to immunopeptidomics.
Journal Article
Influence of air mass downward transport on the variability of surface ozone at Xianggelila Regional Atmosphere Background Station, southwest China
In situ measurements of ozone (O3), carbon monoxide (CO) and meteorological parameters were made from December 2007 to November 2009 at the Xianggelila Regional Atmosphere Background Station (28.006° N, 99.726° E; 3580 m a.s.l.), southwest China. It was found that both O3 and CO peaked in spring while the minima of O3 and CO occurred in summer and winter, respectively. A normalized indicator (marked as \"Y\") on the basis of the monthly normalized O3, CO and water vapor, is proposed to evaluate the occurrence of O3 downward transport from the upper, O3-rich atmosphere. This composite indicator has the advantage of being less influenced by the seasonal or occasional variations of individual factors. It is shown that the most frequent and effective transport occurred in winter (accounting for 39% of the cases on the basis of a threshold of the Y value larger than 4) and they can make a significant contribution to surface O3 at Xianggelila. A 9.6 ppb increase (21.0%) of surface ozone is estimated based on the impact of deep downward transport events in winter. A case of strong O3 downward transport event under the synoptic condition of a deep westerly trough is studied by the combination of the Y indicator, potential vorticity, total column ozone and trajectory analysis. Asian monsoon plays an important role in suppressing O3 accumulation in summer and fall. The seasonal variation of O3 downward transport, as suggested by the Y indicator at Xianggelila, is consistent with the seasonality of stratosphere-to-troposphere transport and the subtropical jet stream over the Tibetan Plateau.
Journal Article
Patient-reported outcome use in oncology: a systematic review of the impact on patient-clinician communication
PurposePatient-reported outcomes (PROs) are an increasingly popular tool to optimize care and bridge the gap between patient experience and clinician understanding. The aim of this review was to identify mechanisms through which PROs facilitate patient-clinician communication in the adult oncology population.MethodsWe conducted a systematic review of the published literature using the following data sources: MEDLINE, EMBASE, CINAHL, PsycINFO, Cab Direct, and CDSR. Studies included in this review reported on the outcomes of PRO use, used PROs as an intervention and not as a study outcome measurement tool, included cancer patients or survivors as study participants, and analyzed patient-clinician communication.ResultsWe identified 610 unique records, of which 43 publications met the inclusion and exclusion criteria. Synthesis of the reviewed studies provided evidence of the usefulness of PROs in facilitating patient-clinician communication on a variety of topics. We identified mechanisms though which PROs influenced patient-clinician communication to include increasing symptom awareness, prompting discussion, streamlining consultations, and facilitating inter-professional communication. Barriers to PRO use in communication improvement include technical problems impeding its administration and completion, compliance issues due to lack of incentive or forgetfulness, and use of PROs that do not appropriately assess issues relevant to the patient. Facilitators include increased education on PRO use, using PRO tools that patients find more acceptable, and providing patient data summaries in an easily accessible format for clinicians.ConclusionsOur review suggests that PROs facilitate patient-clinician communication through various mechanisms that could perhaps contribute to improvements in symptom management and survival. The impact of PROs on clinical outcomes, however, remains poorly studied.
Journal Article
Breakup of the proton halo nucleus 8B near barrier energies
The dynamics of a nuclear open quantum system could be revealed in the correlations between the breakup fragments of halo nuclei. The breakup mechanism of a proton halo nuclear system is of particular interest as the Coulomb polarization may play an important role, which, however, remains an open question. Here we use a highly efficient silicon detector array and measure the correlations between the breakup fragments of
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B incident on
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Sn at near-barrier energies. The energy and angular correlations can be explained by a fully quantum mechanical method based on the state-of-the-art continuum discretized coupled channel calculations. The results indicate that, compared to the neutron halo nucleus
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B presents distinctive reaction dynamics: the dominance of the elastic breakup. This breakup occurs mainly via the short-lived continuum states, almost exhausts the
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Be yield, indicating the effect of Coulomb polarization on the proton halo state. The correlation information reveals that the prompt breakup mechanism dominates, occurring predominantly on the outgoing trajectory. We also show that, as a large environment, the continuum of
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B breakup may not significantly influence elastic scattering and complete fusion.
Halo-structured nuclei are examples of many-body open quantum system. Here the authors use a complete kinematics measurement and find an elastic breakup of proton halo nucleus
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B.
Journal Article