Digital technology and COVID-19 Ting, Daniel Shu Wei; Carin, Lawrence; Dzau, Victor ...
Nature medicine,
04/2020, Letnik:
26, Številka:
4
Journal Article
Dissipative Kerr solitons in resonant frequency combs offer a promising route for ultrafast mode-locking, precision spectroscopy and time-frequency standards. The dynamics for the dissipative soliton ...generation, however, are intrinsically intertwined with thermal nonlinearities, limiting the soliton generation parameter map and statistical success probabilities of the solitary state. Here, via use of an auxiliary laser heating approach to suppress thermal dragging dynamics in dissipative soliton comb formation, we demonstrate stable Kerr soliton singlet formation and soliton bursts. First, we access a new soliton existence range with an inverse-sloped Kerr soliton evolution-diminishing soliton energy with increasing pump detuning. Second, we achieve deterministic transitions from Turing-like comb patterns directly into the dissipative Kerr soliton singlet pulse bypassing the chaotic states. This is achieved by avoiding subcomb overlaps at lower pump power, with near-identical singlet soliton comb generation over twenty instances. Third, with the red-detuned pump entrance route enabled, we uncover unique spontaneous soliton bursts in the direct formation of low-noise optical frequency combs from continuum background noise. The burst dynamics are due to the rapid entry and mutual attraction of the pump laser into the cavity mode, aided by the auxiliary laser and matching well with our numerical simulations. Enabled by the auxiliary-assisted frequency comb dynamics, we demonstrate an application of automatic soliton comb recovery and long-term stabilization against strong external perturbations. Our findings hold potential to expand the parameter space for ultrafast nonlinear dynamics and precision optical frequency comb stabilization.
A redox‐neutral, light‐mediated functionalization of unactivated C(sp3)−H bonds via iminyl radicals is presented here. A 1,5‐H transfer followed by the functionalization of a C(sp2)−H bond takes ...place in aqueous media producing a variety of elaborated fused ketones. Mechanistic investigations have revealed 1,5‐H transfer as the reversible, rate‐determining step in this transformation. Divergent scaffolds are also accessible via C(sp3)−N bond formation upon a careful choice of the reaction additives.
The choice is yours: The title reaction represents the first example of visible‐light‐mediated 1,5‐H transfer of iminyl radicals under mild, redox neutral conditions. A radical relay process enables the site‐selective functionalization of aliphatic C−H bonds via C−C and C−N bond formation to produce divergent scaffolds upon a careful choice of additives.
The recent confirmation of the muon
g
-
2
anomaly by the Fermilab
g
-
2
experiment may harbinger a new era in
μ
and
τ
physics. In the context of general two Higgs doublet model, the discrepancy can ...be explained via one-loop exchange of sub-TeV exotic scalar and pseudoscalars, namely
H
and
A
, that have flavor changing neutral couplings
ρ
τ
μ
and
ρ
μ
τ
at
∼
20
times the usual tau Yukawa coupling,
λ
τ
. Taking
ρ
ℓ
ℓ
′
∼
λ
m
i
n
(
ℓ
,
ℓ
′
)
, we show that the above solution to muon
g
-
2
then predicts enhanced rates of various charged lepton flavor violating processes, which should be accessible at upcoming experiments. We cover muon related processes such as
μ
→
e
γ
,
μ
→
e
e
e
and
μ
N
→
e
N
, and
τ
decays
τ
→
μ
γ
and
τ
→
μ
μ
μ
. A similar one-loop diagram with
ρ
e
τ
=
ρ
τ
e
=
O
(
λ
e
)
induces
μ
→
e
γ
, bringing the rate right into the sensitivity of the MEG II experiment. The
μ
e
γ
dipole can be probed further by
μ
→
3
e
and
μ
N
→
e
N
. With its promised sensitivity range and ability to use different nuclei, the
μ
N
→
e
N
conversion experiments can not only make discovery, but access the extra diagonal quark Yukawa couplings
ρ
qq
. For the
τ
lepton, we find that
τ
→
μ
γ
would probe
ρ
τ
τ
down to
λ
τ
or lower, while
τ
→
3
μ
would probe
ρ
μ
μ
to
O
(
λ
μ
)
.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A series of twisted D–π–A type emitters based on the acridine donor unit and CN‐substituted pyridine, pyrimidine, and benzene acceptor units are studied. They not only allow one to systematically ...probe the influence of different acceptor strengths, but also permit one to intriguingly probe the influence of tunable conformations (twist angles) within the acceptor moieties through controlling the orientation of asymmetric heteroaromatic ring relative to the donor component. Intramolecular charge‐transfer transitions are observed in all these compounds and emission wavelengths are widely tunable from deep blue to yellow not only by the general acceptor strength due to the characters of heteroarene and CN‐substitution pattern but also by the subtle control of in‐acceptor conformation (twist angles). Small triplet‐to‐singlet energy gaps (ΔEST) and significant thermally activated delayed fluorescence (TADF) characteristics are obtained in a series of D–π–A compounds with sufficient acceptor strengths and tunable in‐acceptor conformation, yielding a series of efficient blue‐green to yellow TADF emitters with promisingly high photoluminescence quantum yields of 90%–100%. Highly efficient blue‐green to yellow TADF organic light‐emitting diodes (OLEDs) having external quantum efficiencies of up to 23.1%–31.3% are achieved using these efficient TADF emitters, which are among the most efficient TADF OLEDs ever reported.
Efficient blue‐green to yellow thermally activated delayed fluorescence emitters capable of generating 23%–31% electroluminescence external quantum efficiencies are developed adopting the acridine donor unit and cyano (CN)‐substituted pyridine and pyrimidine acceptor units. They permit systematic probing of influences of acceptor strengths and tunable conformations (twist angles) within the acceptor moieties through controlling the orientation of asymmetric heteroaromatic ring.
Fluorine-containing molecules have found broad applications in pharmaceutical and agrochemical industries as introducing fluorine into a molecule could significantly tune the biological activities of ...parent molecules. Thus, the synthesis of fluorine-containing molecules has received substantial attention over the past few decades. As a complementary strategy for the synthesis of fluorinated compounds through new Csp3–F bonds formation, selective cleavage of inert Csp3–F bonds from easily-available and cost-effective multifluorinated molecules, such as fluoroalkylaromatics, α-trifluoromethyl alkenes and α-multifluorinated carbonyl compounds, has been emerging as an attractive alternative to access fluorine-containing molecules. Moreover, the inherent nature of radical reactions offers the opportunity for the selective Csp3–F functionalizations to occur under mild conditions. In this regard, the development of photoredox catalysis, transition-metal catalysis, or electrochemistry to enable radical species generation via selective Csp3–F cleavage has gained broad attention and substantial progress has been made over recent years. This highlight summerizes the recent advances in the single-electron-transfer enabled selective functionalizations of Csp3–F bonds in multifluorinated compounds via radical pathways.
We study electroweak baryogenesis driven by the top quark in a general two Higgs doublet model with flavor-changing Yukawa couplings, keeping the Higgs potential CP invariant. With Higgs sector ...couplings and the additional top Yukawa coupling ρtt all of O(1), one naturally has sizable CP violation that fuels the cosmic baryon asymmetry. Even if ρtt vanishes, the favor-changing coupling ρtc can still lead to successful baryogenesis. Phenomenological consequences such as t→ch, τ→μγ electron electric dipole moment, h→γγ, and hhh coupling are discussed.
We elucidate a cancellation mechanism for the electric dipole moment of the electron in the general two Higgs doublet model. The impressive improvement by the ACME Collaboration in 2018 suggests the ...presence of a new electron Yukawa coupling that brings in exquisite cancellations among dangerous diagrams, broadening the solution space for electroweak baryogenesis driven by an extra top Yukawa coupling. The cancellation mechanism calls for the new Yukawa couplings to have hierarchical structures that echo the observed pattern of the Standard Model Yukawa couplings.
Graphene, a unique two-dimensional material comprising carbon in a honeycomb lattice1, has brought breakthroughs across electronics, mechanics and thermal transport, driven by the quasiparticle Dirac ...fermions obeying a linear dispersion2,3. Here, we demonstrate a counter-pumped all-optical difference frequency process to coherently generate and control terahertz plasmons in atomic-layer graphene with octave-level tunability and high efficiency. We leverage the inherent surface asymmetry of graphene for strong second-order nonlinear polarizability4,5, which, together with tight plasmon field confinement, enables a robust difference frequency signal at terahertz frequencies. The counter-pumped resonant process on graphene uniquely achieves both energy and momentum conservation. Consequently, we demonstrate a dual-layer graphene heterostructure with terahertz charge- and gate-tunability over an octave, from 4.7 THz to 9.4 THz, bounded only by the pump amplifier optical bandwidth. Theoretical modelling supports our single-volt-level gate tuning and optical-bandwidth-bounded 4.7 THz phase-matching measurements through the random phase approximation, with phonon coupling, saturable absorption and below the Landau damping, to predict and understand graphene plasmon physics.
Red pear is favored because of its bright appearance and abundant anthocyanins. Anthocyanin biosynthesis is controlled by transcription factors (TFs) forming regulatory complexes. In red-skinned ...pears, the WRKY TFs have a significant relationship with anthocyanin biosynthesis, but the molecular mechanism of the WRKY TFs involved in regulating color formation in red-skinned pear is unclear. In this study, the TFs
and
were screened as candidate genes for controlling anthocyanin biosynthesis by transcriptome data and bioinformatics analysis. The effect of anthocyanin accumulations after cotransformation of
or
with its partners
,
, and
was verified in tobacco leaves and strawberry receptacles by a transient expression system. RT-qPCR analysis and a dual-luciferase reporter system further confirmed that this cotransformation activated the expression of
,
, and
in anthocyanin biosynthesis and
in anthocyanin transport instead of the
and
. Furthermore, the cotransformed
and
could bind to the
promoter, and
directly activated the transcription of
. In addition, the TF PyWRKY26 could interact with PybHLH3, as confirmed by firefly luciferase complementation and yeast two-hybrid (Y2H) assays. These results showed that the interaction of PyWRKY26 and PybHLH3 could cotarget the
promoter, which resulted in anthocyanin accumulation in red-skinned pear. This study further strengthened the understanding of the regulatory mechanism of anthocyanin accumulation and contributed to improving the appearance of red-skinned pears.
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