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991.
A quark or gluon jet traversing through a quark-gluon plasma can be converted to a gluon or quark jet through scattering with
the thermal quarks and gluons in the quark-gluon plasma. Their conversion rates due to two-body elastic
and inelastic
scattering have recently been evaluated in the lowest order in QCD. Including both energy loss and conversions of quark and
gluon jets in the expanding quark-gluon plasma produced in relativistic heavy ion collisions, a net conversion of quark jets
to gluon jets has been found. This reduces the difference between the nuclear modification factors for quark and gluon jets
in heavy ion collisions and thus enhances the ratios of high transverse momentum protons and antiprotons to pions that are
produced from the fragmentation of these jets. To account for the observed similar ratios in central Au + Au and p + p collisions at same energy requires, however, a much larger net quark to gluon jet conversion rate than that given by the
lowest-order QCD, indicating the importance of higher-order processes and the strongly coupling properties of the quark-gluon
plasma in describing the propagation of jets in the quark-gluon plasma.
B.-W. Zhang: On leave from: Institute of Particle Physics, Huazhong Normal University, Wuhan 430079, China
Correspondence: C.-M. Ko, Cyclotron Institute and Physics Department, Texas A&M University, College Station, TX 77843-3366,
USA 相似文献
992.
993.
For every smooth (irreducible) cubic surface S we give an explicit construction of a representative for each of the 72 equivalence classes of determinantal representations. Equivalence classes (under GL3 × GL3 action by left and right multiplication) of determinantal representations are in one to one correspondence with the sets of six mutually skew lines on S and with the 72 (two-dimensional) linear systems of twisted cubic curves on S. Moreover, if a determinantal representation M corresponds to lines (a 1,...,a 6) then its transpose M t corresponds to lines (b 1,...,b 6) which together form a Schläfli’s double-six \(a_1\ldots a_6 \choose b_1\ldots b_6\) . We also discuss the existence of self-adjoint and definite determinantal representation for smooth real cubic surfaces. The number of these representations depends on the Segre type F i . We show that a surface of type F i , i = 1,2,3,4 has exactly 2(i?1) nonequivalent self-adjoint determinantal representations none of which is definite, while a surface of type F 5 has 24 nonequivalent self-adjoint determinantal representations, 16 of which are definite. 相似文献
994.
C. Foias I. B. Jung E. Ko C. Pearcy 《Transactions of the American Mathematical Society》2007,359(6):2899-2913
In this article we employ a technique originated by Enflo in 1998 and later modified by the authors to study the hyperinvariant subspace problem for subnormal operators. We show that every ``normalized'subnormal operator such that either does not converge in the SOT to the identity operator or does not converge in the SOT to zero has a nontrivial hyperinvariant subspace.
995.
Prof. Dr. Pavel Kočovský Prof. Dr. Jan‐E. Bäckvall 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):36-56
In this review the stereochemistry of palladium‐catalyzed addition of nucleophiles to alkenes is discussed, and examples of these reactions in organic synthesis are given. Most of the reactions discussed involve oxygen and nitrogen nucleophiles; the Wacker oxidation of ethylene has been reviewed in detail. An anti‐hydroxypalladation in the Wacker oxidation has strong support from both experimental and computational studies. From the reviewed material it is clear that anti‐addition of oxygen and nitrogen nucleophiles is strongly favored in intermolecular addition to olefin–palladium complexes even if the nucleophile is coordinated to the metal. On the other hand, syn‐addition is common in the case of intramolecular oxy‐ and amidopalladation as a result of the initial coordination of the internal nucleophile to the metal. 相似文献
996.
997.
Li Ma Qian Wang Dr. Wai‐Lun Man Dr. Hoi‐Ki Kwong Dr. Chi‐Chiu Ko Prof. Tai‐Chu Lau 《Angewandte Chemie (International ed. in English)》2015,54(17):5246-5249
The study of manganese complexes as water‐oxidation catalysts (WOCs) is of great interest because they can serve as models for the oxygen‐evolving complex of photosystem II. In most of the reported Mn‐based WOCs, manganese exists in the oxidation states III or IV, and the catalysts generally give low turnovers, especially with one‐electron oxidants such as CeIV. Now, a different class of Mn‐based catalysts, namely manganese(V)–nitrido complexes, were explored. The complex [MnV(N)(CN)4]2− turned out to be an active homogeneous WOC using (NH4)2[Ce(NO3)6] as the terminal oxidant, with a turnover number of higher than 180 and a maximum turnover frequency of 6 min−1. The study suggests that active WOCs may be constructed based on the MnV(N) platform. 相似文献
998.
Rhodium(II)‐Catalyzed Cycloaddition Reactions of Non‐classical 1,5‐Dipoles for the Formation of Eight‐Membered Heterocycles
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Dong Jin Lee Donguk Ko Prof. Eun Jeong Yoo 《Angewandte Chemie (International ed. in English)》2015,54(46):13715-13718
A new type of intermolecular rhodium(II)‐catalyzed [5+3] cycloaddition has been developed. This higher‐order cycloaddition between pyridinium zwitterion 1,5‐dipole equivalents and enol diazoacetates enables the formation of eight‐membered heterocyclic skeletons, which are otherwise difficult to construct. The optimized cycloaddition occurs efficiently under mild conditions with a wide range of pyridinium zwitterions and with high functional‐group tolerance. 相似文献
999.
Youngmin Ko Hyunji Park Kyunam Lee Dr. Sung Joo Kim Dr. Hyeokjun Park Dr. Youngjoon Bae Jihyeon Kim Prof. Soo Young Park Dr. Ji Eon Kwon Prof. Kisuk Kang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(13):5414-5418
Redox mediators (RMs) are considered an effective countermeasure to reduce the large polarization in lithium-oxygen batteries. Nevertheless, achieving sufficient enhancement of the cyclability is limited by the trade-offs of freely mobile RMs, which are beneficial for charge transport but also trigger the shuttling phenomenon. Here, we successfully decoupled the charge-carrying redox property of RMs and shuttling phenomenon by anchoring the RMs in polymer form, where physical RM migration was replaced by charge transfer along polymer chains. Using PTMA (poly(2,2,6,6-tetramethyl-1-piperidinyloxy-4-yl methacrylate)) as a polymer model system based on the well-known RM tetramethylpiperidinyloxyl (TEMPO), it is demonstrated that PTMA can function as stationary RM, preserving the redox activity of TEMPO. The efficiency of RM-mediated Li2O2 decomposition remains remarkably stable without the consumption of oxidized RMs or degradation of the lithium anode, resulting in an improved performance of the lithium-oxygen cell. 相似文献
1000.
Tereza Košutová Lukáš Horák Artem Shelemin Mykhailo Vaidulych Jan Hanuš Hynek Biederman Ondřej Kylián Pavel Solař Miroslav Cieslar Andrei Choukourov Milan Dopita 《Surface and interface analysis : SIA》2020,52(12):1023-1028
Metal-polymer nanocomposites have gained increasing attention due to the wide potential applications field. Synthesis of nanoparticles from the gas phase is an intensively studied alternative to the chemical preparation methods. We present a one-step procedure that combines magnetron-based gas aggregation cluster source of silver nanoparticles and simultaneous plasma-enhanced chemical vapour deposition of hexamethyldisiloxane (HMDSO). The key parameter of the process, significantly influencing the morphology and microstructure of studied nanoparticles, was found to be the amount of HMDSO added to the deposition chamber as witnessed by small angle X-ray scattering and X-ray diffraction methods combined with transmission electron microscopy and UV–Vis spectrophotometry. The presence of HMDSO in the chamber leads to changes in the size distribution and also in the architecture of prepared nanoparticles. The increasing amount of HMDSO induces the formation of individual core-shell nanoparticles, chains of core-shell nanoparticles, and for the highest concentration of HMDSO, the synthesis of multi-core-shell nanoparticles. The size of crystallites in the silver cores of nanoparticles decreases with addition of HMDSO, which prevents further aggregation. 相似文献