Covalent organic frameworks (COFs), which are built upon dynamic covalent chemistry (DCC) with various organic building blocks, possess predesignable, highly ordered and crystalline porous ...structures. These features endow COFs with great potential in the development of function‐tailored materials, particularly in catalytic organic synthesis. Start from selective oxidation reactions early introduced by Ferdi, Thomas and their co‐workers, and then Wang and co‐workers performed Suzuki‐Miyaura reaction through integrating palladium into COFs, increasing numbers of works were established to explore their potentials in the 4.5catalysis of organic reactions. As heterogeneous organic catalysts, COFs bring benefits and solve problems, but also create new obstacles. Hence, we would like to establish a comprehensive system to review some pioneering works in this area. This will help us get a better view so that we can discuss the key and challenging issues we are currently confronted with.
A
bstract
The lifetimes of bottom and charmed hadrons are analyzed within the framework of the heavy quark expansion (HQE). Lifetime differences arise from the spectator effects such as weak
W
...-annihilation and Pauli interference. Spectator effects originating from dimension-7 four-quark operators are derived. Hadronic matrix elements of four-quark operators are parameterized in a model-independent way. Using the dimension-6 bag parameters recently determined from HQET sum rules and the vacuum insertion approximation for meson matrix elements of dimension-7 operators, the calculated
B
meson lifetime ratios
τ
(
B
+
)/
τ
(
B
d
0
) = 1.074
− 0.016
+ 0.017
and
τ
(
B
s
0
)/
τ
(
B
d
0
) = 0.9962 ± 0.0024 are in excellent agreement with experiment. Likewise, based on the quark model evaluation of baryon matrix elements, the resulting baryon lifetime ratios
τ
(Ξ
b
−
)/
τ
(Λ
b
0
),
τ
(Ξ
b
−
)/
τ
(
Ξ
b
0
),
τ
(Ω
b
−
)/
τ
(
Ξ
b
−
) and the Λ
b
−
B
0
lifetime ratio
τ
(Λ
b
0
)/
τ
(
B
d
0
) = 0.953 also agree well with the data. Contrary to the bottom hadron sector where the HQE in 1/
m
b
works well, the HQE to 1/
m
c
3
fails to give a satisfactory description of the lifetimes of both charmed mesons and charmed baryons. This calls for the subleading 1/
m
Q
corrections to spectator effects. The relevant dimension-7 spectator effects are in the right direction for explaining the large lifetime ratio of
τ
(Ξ
c
+
)/
τ
(Λ
c
+
). However, the destructive 1/
m
c
corrections to Γ(Ω
c
0
) are too large to justify the validity of the HQE, namely, the predicted Pauli interference and semileptonic rates for Ω
c
0
become negative. Demanding these rates to be positive for a sensible HQE, we find the lifetime pattern
τ
(Ξ
c
+
) >
τ
(
Ω
c
0
) >
τ
(Λ
c
+
) >
τ
(Ξ
c
0
), contrary to the current hierarchy
τ
(Ξ
c
+
) >
τ
(Λ
c
+
) >
τ
(Ξ
c
0
) >
τ
(
Ω
c
0
). We conclude that the Ω
c
0
, which is naively expected to be shortest-lived in the charmed baryon system owing to the large constructive Pauli interference, could live longer than the Λ
c
+
due to the suppression from 1/
m
c
corrections arising from dimension-7 four-quark operators. The new charmed baryon lifetime pattern needs to be tested in forthcoming experiments.
Charmed baryon physics circa 2021 Cheng, Hai-Yang
Chinese journal of physics (Taipei),
August 2022, 2022-08-00, Letnik:
78
Journal Article
Recenzirano
Odprti dostop
This is an update of the two articles (Cheng, 2009; Cheng, 2015) in which charmed baryon physics around 2007 and 2015, respectively, were reviewed. In this review we emphasize the experimental ...progress and the theoretical development since 2015.
•Spin-parity assignments of higher excited charmed baryon states are discussed.•Lifetimes of charmed baryons are studied in heavy quark expansion.•Nonleptonic weak decays and radiative decays of charmed baryons are reviewed.•CP violation in the charmed baryon system is addressed.
Acceleration is an important consideration when imaging moving organs such as the heart. Not only does acceleration enable motion‐free scans but, more importantly, it lies at the heart of capturing ...the dynamics of cardiac motion. For over three decades, various ingenious approaches have been devised and implemented for rapid CINE MRI suitable for dynamic cardiac imaging. Virtually all techniques relied on acquiring less data to reduce acquisition times. Parallel imaging was among the first of these innovations, using multiple receiver coils and mathematical algorithms for reconstruction; acceleration factors of 2 to 3 were readily achieved in clinical practice. However, in the context of imaging dynamic events, further decreases in scan time beyond those provided by parallel imaging were possible by exploiting temporal coherencies. This recognition ushered in the era of k‐t accelerated MRI, which utilized predominantly statistical methods for image reconstruction from highly undersampled k‐space. Despite the successes of k‐t acceleration methods, however, the accuracy of reconstruction was not always guaranteed. To address this gap, MR physicists and mathematicians applied compressed sensing theory to ensure reconstruction accuracy. Reconstruction was, indeed, more robust, but it required optimizing regularization parameters and long reconstruction times. To solve the limitations of all previous methods, researchers have turned to artificial intelligence and deep neural networks for the better part of the past decade, with recent results showing rapid, robust reconstruction. This review provides a comprehensive overview of key developments in the history of CINE MRI acceleration, and offers a unique and intuitive explanation behind the techniques and underlying mathematics.Level of Evidence: 5Technical Efficacy Stage: 1
Cancer is a well-known killer of human beings, which has led to countless deaths and misery. Anticancer peptides open a promising perspective for cancer treatment, and they have various attractive ...advantages. Conventional wet experiments are expensive and inefficient for finding and identifying novel anticancer peptides. There is an urgent need to develop a novel computational method to predict novel anticancer peptides. In this study, we propose a deep learning long short-term memory (LSTM) neural network model, ACP-DL, to effectively predict novel anticancer peptides. More specifically, to fully exploit peptide sequence information, we developed an efficient feature representation approach by integrating binary profile feature and k-mer sparse matrix of the reduced amino acid alphabet. Then we implemented a deep LSTM model to automatically learn how to identify anticancer peptides and non-anticancer peptides. To our knowledge, this is the first time that the deep LSTM model has been applied to predict anticancer peptides. It was demonstrated by cross-validation experiments that the proposed ACP-DL remarkably outperformed other comparison methods with high accuracy and satisfied specificity on benchmark datasets. In addition, we also contributed two new anticancer peptides benchmark datasets, ACP740 and ACP240, in this work. The source code and datasets are available at https://github.com/haichengyi/ACP-DL.
Ubiquitin ligases control the degradation of core clock proteins to govern the speed and resetting properties of the circadian pacemaker. However, few studies have addressed their potential to ...regulate other cellular events within clock neurons beyond clock protein turnover. Here, we report that the ubiquitin ligase, UBR4/POE, strengthens the central pacemaker by facilitating neuropeptide trafficking in clock neurons and promoting network synchrony. Ubr4-deficient mice are resistant to jetlag, whereas poe knockdown flies are prone to arrhythmicity, behaviors reflective of the reduced axonal trafficking of circadian neuropeptides. At the cellular level, Ubr4 ablation impairs the export of secreted proteins from the Golgi apparatus by reducing the expression of Coronin 7, which is required for budding of Golgi-derived transport vesicles. In summary, UBR4/POE fulfills a conserved and unexpected role in the vesicular trafficking of neuropeptides, a function that has important implications for circadian clock synchrony and circuit-level signal processing.
Charmed baryons circa 2015 Cheng, Hai-Yang
Frontiers of physics,
12/2015, Letnik:
10, Številka:
6
Journal Article
Recenzirano
Odprti dostop
This is essentially an update of Ref. 1 H. Y. Cheng, Int. J. Mod. Phys. A 24 (Suppl. 1), 593 (2009), a review of charmed baryon physics around 2007. Topics covered in this review include the ...spectroscopy, strong decays, lifetimes, nonleptonic and semileptonic weak decays, and electromagnetic decays of charmed baryons.
Possible spin-parity quantum numbers for excited charmed baryon resonances are discussed in this work. Our main results are as follows. (i) Among the five newly observed Ωc states, we have identified ...Ωc(3090) and Ωc(3119) with radially excited 12+(2S) and 32+(2S) states, respectively, and Ωc(3000) with 12−(1P). The two states Ωc(3050) and Ωc(3066) form a P-wave (32−,52−) doublet. (ii) The widths of Ωc(3066) and Ξc′(2930) are calculable within the framework of heavy hadron chiral perturbation theory. (iii) Since the width of Ωc0(12−) is of order 410 MeV, not all observed narrow Ωc baryons can be identified with 1P states. (iv) For the antitriplet Λc and Ξc states, their Regge trajectories for the orbital excitations of 12− and 32− are parallel to each other. Based on this nice property of parallelism, we see that the highest state Λc(2940) does not fit if its quantum numbers are 32− as found by LHCb. We suggest that Λc(2940)+ is most likely the 12−(2P) state. (v) The charmed baryon Σc(2800) cannot be a 12− state; otherwise, its width will be over 400 MeV, too large compared to the measured one. (vi) In the study of Regge trajectories of Ξc′ states, we find a missing state. It should have quantum numbers 52− with a mass around 2920 MeV. (vii) Antitriplet and sextet states are classified according to their JP(nL) quantum numbers. The mass differences between Ξc and Λc in the antitriplet states clearly lie between 180 and 200 MeV. Moreover, the mass splitting between Ωc and Ξc′ is found to be very close to the one between Ξc′ and Σc for five different sets of sextet multiplets. This lends a strong support to the quantum number assignment to the sextet states in this work.
PDF
