We study masses, lifetimes and weak decays of the triply heavy tetraquarks
b
c
¯
b
q
¯
. The masses of tetraquark are explored under two different models. Further more, our calculations show a ...possibility of existence for the stable triply heavy tetraquark
b
c
¯
b
q
¯
with
J
P
=
1
+
which should be verified in experiment. Following the heavy quark expanding(HQE), the lifetimes of tetraquarks
b
c
¯
b
q
¯
can be expressed as the summation of different dimension operators. Particularly, we obtain the lifetimes of
b
c
¯
b
q
¯
at the next-to-leading order(NLO) given as
τ
(
T
{
c
¯
q
¯
}
{
b
b
}
)
=
0.70
×
10
-
12
s
. Besides, we construct the weak decays Hamiltonian of
b
c
¯
b
q
¯
in hadronic level under the SU(3) flavor symmetry. The discussion of the Hamiltonian can deduce the decay amplitudes and width relations of the tetraquarks. Following the choosing rules, we collect some golden channels for the mesonic decays of tetraquarks, which will be helpful to search for triply heavy tetraquarks
b
c
¯
b
q
¯
in future experiments.
We study strong deflection gravitational lensing by a Lee-Wick ultracompact object. Its unique feature is a series of relativistic images inside its photon sphere, which are absent in the case of a ...black hole. We obtain its observables and estimate them for the supermassive black holes Sgr A* and M87* respectively in the Galactic center and in the center of M87. We find that the innermost relativistic image is a very promising signature according to its angular separation from the photon sphere and its considerable brightness. A preliminary bound on the UV scale of such an object is estimated based on the shadow of M87*.
Organic azides are highly reactive, which have long established as versatile building blocks in the assembly of structurally diverse N‐containing heterocycles. The conversion of organic azides into ...high‐value compounds is of great importance and a subject of enormous current interest. Transition metal‐catalyzed C(sp2)−H amination/annulation of organic azides provides a powerful tool for the transformation of organic azides into a wide range of biologically important heterocyclic frameworks. In this review, we aim to summarize the recent progress on organic azides‐mediated C(sp2)−H amination/annulation for N‐heterocycle synthesis enabled by transition metal catalysts. Representative strategies are discussed in detail, including catalytic systems, reaction scopes, limitations and mechanisms.
The strength and elastic modulus of macroscopic nanoporous Au samples are much lower than that predicted by using Gibson-Ashby scaling laws. Here we attribute this discrepancy to a lowered network ...connectivity in nanoporous structure, and propose to modify the scaling equations (for both strength and stiffness) by introducing a concept of effective relative density. It is presented that the effective relative density can be determined by measuring the elasticity of nanoporous Au; under this scenario, the corrected strengths of Au nano-ligaments agree (on the order of magnitude) well with the previous data for similar-sized Au nanowires or nanopillars, which confirms our hypotheses. This study also revealed a low power-law exponent of size-dependent strength for Au nano-ligaments (β = −0.34) compared with that of Au submicron-pillars machined by focused ion beam (FIB) (β = −0.61), which may be related to the critical roles of surface defects played in deformation. A ratio between effective relative density and relative density is suggested to quantify the network connectivity in nanoporous structure, which decreases rapidly during structure coarsening – it explains why most previous nanoporous Au samples, which more or less experienced coarsening, were unexpectedly soft. Current study also leads to some general strategies for syntheses of strong and stiff nanoporous metals.
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We study the masses and lifetimes of doubly charmed pentaquark
P
c
c
q
¯
q
q
(
q
=
u
,
d
,
s
)
primarily. The operation of masses carried out by the doubly heavy triquark-diquark model, whose results ...suggests the existence of stable states
c
c
s
¯
u
d
with the parity
J
P
=
1
2
-
. The roughly calculation about lifetimes show the short magnitudes,
(
4
.
65
-
0.55
+
0.71
)
×
10
-
13
s
for the parity
J
P
=
1
2
-
and
(
0
.
93
-
0.11
+
0.14
)
×
10
-
12
s
for
J
P
=
3
2
-
. Since the pentaquark
c
c
s
¯
u
d
is interpreted as the stable bound states against strong decays, then we will focus on the production and possible decay channels of the pentaquark in the next step, the study would be fairly valuable supports for future experiments. For completeness, we systematically studied the production from
Ω
ccc
and the decay modes in the framework SU(3) flavor symmetry, including the processes of semi-leptonic and two body non-leptonic decays. Synthetically, we make a collection of the golden channels.
Developing low‐cost and high‐activity pH‐universal hydrogen evolution reaction (HER) catalysts is very crucial to the industrialization of water electrolysis. However, the high price, low yield, and ...poor stability of current HER catalysts make them difficult to meet practical requirements. Herein, a plasma spraying technique is employed to prepare self‐supported Cu catalysts with tensile strain for the first time. The tensile strain upshifts the d‐band of Cu, improves the water dissociation and H* adsorption, eventually improves the intrinsic HER catalytic activity. As such, Cu electrode achieves overpotentials of 182 mV in 0.5 m H2SO4, 261 mV in 1 M PBS, and 121 mV in 1 M KOH at 10 mA cm–2. In addition, Cu electrode also performs well at high current densities, the overpotentials at 1 A cm–2 are much lower than those of Pt foil in acid, neutral, and alkaline solutions.
The Cu electrode prepared by plasma spraying exhibits an excellent pH‐universal HER catalytic activity, superb long‐term stability, and marvelous corrosion resistance. The superb HER activity is attributed to self‐supported porous structure, abundant active sites, tensile strain enhanced intrinsic catalytic activity, and small charge transfer resistance.
Polysaccharides are biopolymers made up of a large number of monosaccharides joined together by glycosidic bonds. Polysaccharides are widely distributed in nature: Some, such as peptidoglycan and ...cellulose, are the components that make up the cell walls of bacteria and plants, and some, such as starch and glycogen, are used as carbohydrate storage in plants and animals. Fungi exist in a variety of natural environments and can exploit a wide range of carbon sources. They play a crucial role in the global carbon cycle because of their ability to break down plant biomass, which is composed primarily of cell wall polysaccharides, including cellulose, hemicellulose, and pectin. Fungi produce a variety of enzymes that in combination degrade cell wall polysaccharides into different monosaccharides. Starch, the main component of grain, is also a polysaccharide that can be broken down into monosaccharides by fungi. These monosaccharides can be used for energy or as precursors for the biosynthesis of biomolecules through a series of enzymatic reactions. Industrial fermentation by microbes has been widely used to produce traditional foods, beverages, and biofuels from starch and to a lesser extent plant biomass. This review focuses on the degradation and utilization of plant homopolysaccharides, cellulose and starch; summarizes the activities of the enzymes involved and the regulation of the induction of the enzymes in well-studied filamentous fungi.
The newly-discovered
Ξ
cc
+
+
decays into the
Λ
c
+
K
-
π
+
π
+
, but the experimental data has indicated that this decay is not saturated by any two-body intermediate state. In this work, we analyze ...the multi-body weak decays of doubly heavy baryons
Ξ
cc
,
Ω
cc
,
Ξ
bc
,
Ω
bc
,
Ξ
bb
and
Ω
bb
, in particular the three-body nonleptonic decays and four-body semileptonic decays. We classify various decay modes according to the quark-level transitions and present an estimate of the typical branching fractions for a few golden decay channels. Decay amplitudes are then parametrized in terms of a few SU(3) irreducible amplitudes. With these amplitudes, we find a number of relations for decay widths, which can be examined in future.
Characterized by bulk Dirac or Weyl cones and surface Fermi-arc states, topological semimetals have sparked enormous research interest in recent years. The nanostructures, with large ...surface-to-volume ratio and easy field-effect gating, provide ideal platforms to detect and manipulate the topological quantum states. Exotic physical properties originating from these topological states endow topological semimetals attractive for future topological electronics (topotronics). For example, the linear energy dispersion relation is promising for broadband infrared photodetectors, the spin-momentum locking nature of topological surface states is valuable for spintronics, and the topological superconductivity is highly desirable for fault-tolerant qubits. For real-life applications, topological semimetals in the form of nanostructures are necessary in terms of convenient fabrication and integration. Here, we review the recent progresses in topological semimetal nanostructures and start with the quantum transport properties. Then topological semimetal-based electronic devices are introduced. Finally, we discuss several important aspects that should receive great effort in the future, including controllable synthesis, manipulation of quantum states, topological field effect transistors, spintronic applications, and topological quantum computation.
We perform a SU(3) analysis for both semi-leptonic and non-leptonic heavy meson weak decays into a pseudoscalar meson and a fully-light tetraquark in 10 or 27 representation. A reduction of the SU(3) ...representation tensor for the fully-light tetraquarks is produced and all the flavor components for each representation tensor are listed. The decay channels we analysis include
B
/
D
→
U
/
T
P
l
ν
,
B
/
D
→
U
/
T
P
and
B
c
→
U
/
T
P
/
D
, with
U
/
T
represents a fully-light tetraquark in 10 or 27 representation and
P
is a pseudoscalar meson. Finally, among these results we list all the golden decay channels which are expected to have more possibilities to be observed in experiments.
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