602 research outputs found
form factors in HQEFT and model independent analysis of relevant semileptonic decays with NP effects
The form factors of decays into P-wave excited charmed mesons
(including , , , and their
strange counterparts, denoted generically as ) are systematically
calculated via the QCD sum rules in the framework of heavy quark effective
field theory (HQEFT). We consider contributions up to the next leading order of
heavy quark expansion and give all the relevant form factors, including the
scalar and tensor ones only relevant for possible new physics effects. The
expressions for the form factors in terms of several universal wave functions
are derived via heavy quark expansion. These universal functions can be
evaluated through QCD sum rules. Then, the numerical results of the form
factors are presented. With the form factors given here, a model independent
analysis of relevant semileptonic decays is performed, including the contributions from possible new
physics effects. Our predictions for the differential decay widths, branching
fractions and ratios of branching fractions may be tested in
more precise experiments in the future.Comment: 38 pages, 8 figures, 12 table
Electrocatalysis of Oxygen Reduction on Te-Modified Platinum Stepped Crystal Surfaces
Te-modified platinum single-crystal surfaces in the [011̅] zone have been used as model electrocatalysts for oxygen reduction reaction (ORR). The results clearly show that (1) except for Pt(111), all other electrodes display enhanced ORR activity when Te is deposited on the surface; (2) the intrinsic ORR activity for Pt(hkl) decreases in the order of Pt(322) > Pt(755) > Pt(977) > Pt(111) > Pt(311) > Pt(100), while the enhancement factor for ORR with Te modification decreases in the order of Pt(100) > Pt(311) > Pt(977) > Pt(755) > Pt(322); (3) metallic Te and its charge transfer to Pt as well as the consequent lower d-band center and OHad binding energy are probably the reasons for the enhanced electrocatalysis for ORR with Te modification; and (4) the inhibition of Te at Pt(111) as well as the smaller extent for the enhancement of Te at Pt(S)-[n(111) × (100)] with longer terraces in the kinetic region for ORR are a result of partial oxidation of Te. The weaker electronic interaction of Te with the Pt substrate is probably the origin of its facile oxidation at lower potential. Our results imply that modification of Pt with species that can transfer electrons to Pt may be an efficient strategy to enhance the ORR activity.This work was supported by the National Natural Science Foundation of China (No. 22172151, 21972131, and 21832004). E.H. gratefully acknowledged the International Professorship by USTC and financial support from the Ministerio de Ciencia e Innovación (project PID2022–137350NB-I00)
SOME INEQUALITIES FOR EDGE LENGTHS AND CIRCUM-RADIUS OF A SIMPLEX IN HYPERBOLIC SPACE
Abstract. For an n -dimensional simplex in hyperbolic space H n (−1) and spherical space S n (1) , we establish some inequalities for its edge lengths and circum-radius
5-(4-ChloroÂphenÂyl)-1H-tetraÂzole
The two independent molÂecules of the title compound, C7H5ClN4, both lie on a twofold rotation axis that passes through the centroids of the five- and six-membered rings and the attached Cl C atom. One molecule is nearly planar [dihedral angle between rings = 0.22 (6)°], whereas the other is significantly twisted [dihedral angle = 17.38 (6)°]. In the crystal, adjacent molÂecules are linked by N—H⋯N hydrogen bonds into a chain structure
A Survey of Chain of Thought Reasoning: Advances, Frontiers and Future
Chain-of-thought reasoning, a cognitive process fundamental to human
intelligence, has garnered significant attention in the realm of artificial
intelligence and natural language processing. However, there still remains a
lack of a comprehensive survey for this arena. To this end, we take the first
step and present a thorough survey of this research field carefully and widely.
We use X-of-Thought to refer to Chain-of-Thought in a broad sense. In detail,
we systematically organize the current research according to the taxonomies of
methods, including XoT construction, XoT structure variants, and enhanced XoT.
Additionally, we describe XoT with frontier applications, covering planning,
tool use, and distillation. Furthermore, we address challenges and discuss some
future directions, including faithfulness, multi-modal, and theory. We hope
this survey serves as a valuable resource for researchers seeking to innovate
within the domain of chain-of-thought reasoning.Comment: 26 pages. Resources are available at
https://github.com/zchuz/CoT-Reasoning-Surve
Generation of Human Epidermis-Derived Mesenchymal Stem Cell-like Pluripotent Cells and their reprogramming in mouse chimeras
Stem cells can be derived from the embryo (embryonic stem cells, ESCs), from adult tissues (adult stem cells, ASCs), and by induction of fibroblasts (induced pluripotent stem cells, iPSs). Ethical problems, immunological rejection, and difficulties in obtaining human tissues limit the use of ESCs in clinical medicine. Induced pluripotent stem cells are difficult to maintain in vitro and carry a greater risk of tumor formation. Furthermore, the complexity of maintenance and propagation is especially difficult in the clinic. Adult stem cells can be isolated from several adult tissues and present the possibility of self-transplantation for the clinical treatment of a variety of human diseases. Recently, several ASCs have been successfully isolated and cultured in vitro, including hematopoietic stem cells (HSCs) , mesenchymal stem cells (MSCs), epidermis stem cells, neural stem cells (NSCs), adipose-derived stem cells (ADSCs), islet stem cells, and germ line stem cells. Human mesenchymal stem cells originate mainly from bone marrow, cord blood, and placenta, but epidermis-derived MSCs have not yet been isolated. We isolated small spindle-shaped cells with strong proliferative potential during the culture of human epidermis cells and designed a medium to isolate and propagate these cells. They resembled MSCs morphologically and demonstrated pluripotency in vivo; thus, we defined these cells as human epidermis-derived mesenchymal stem cell-like pluripotent cells (hEMSCPCs). These hEMSCPCs present a possible new cell resource for tissue engineering and regenerative medicine
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