We investigate the temperature dependence of the thermal dilepton rate and the electrical conductivity of the gluon plasma at temperatures of 1.1, 1.3, and 1.5T sub(c) in quenched QCD. Making use of ...nonperturbatively clover-improved Wilson valence quarks allows for a clean extrapolation of the vector meson correlation function to the continuum limit. We found that the vector correlation function divided by T super(3) is almost temperature independent in the current temperature window. The spectral functions are obtained by chi super(2) fitting of phenomenologically inspired Ansatze for the spectral function to the continuum extrapolated correlator data, where the correlations between the data points have been included. Systematic uncertainties arising from varying the Ansatze motivated from strong coupling theory as well as perturbation theory are discussed and estimated. We found that the electrical conductivity of the hot medium, related to the slope of the vector spectral function at zero frequency and momentum, is 0.2C sub(em) less than or approximate to sigma/T less than or approximate to 0.7C sub(em) for T=1.1T sub(c) and 0.2C sub(em) less than or approximate to sigma/T less than or approximate to 0.4C sub(em) for the higher temperatures. The dilepton rates and soft photon rates, resulting from the obtained spectral functions, show no significant temperature dependence, either.
A challenging direct asymmetric catalytic aerobic oxidative cross‐coupling of 2‐naphthylamine and 2‐naphthol, using a novel CuI/SPDO system, has been successfully developed for the first time. ...Enantioenriched 3,3′‐disubstituted NOBINs were achieved and could be readily derived to divergent chiral ligands and catalysts. This reaction features high enantioselectivities (up to 96 % ee) and good yields (up to 80 %). The DFT calculations suggest that the F–H interactions between CF3 of L17 and H‐1,8 of 2‐naphthol, and the π–π stacking between the two coupling partners could play vital roles in the enantiocontrol of this cross‐coupling reaction.
We describe a challenging and straightforward asymmetric catalytic aerobic oxidative cross‐coupling of 2‐naphthylamine and 2‐naphthol by using a CuI/SPDO/air system. Optically pure 3,3′‐disubstituted NOBINs were achieved that could be readily derived to divergent chiral ligands/catalysts. Mechanistic studies and DFT calculations give a comprehensive understanding of the high enantioselectivity and good chemoselectivity.
Nonbiaryl N-C atropisomer is an important structural scaffold, which is present in natural products, medicines and chiral ligands. However the direct enantioselective C-H amination to access ...optically pure N-C atropisomer is still difficult and rare. Here we report a π-π interaction and dual H-bond concerted control strategy to develop the chiral phosphoric acids (CPAs) catalyzed direct intermolecular enantioselective C-H amination of N-aryl-2-naphthylamines with azodicarboxylates as amino sources for the construction of atroposelective naphthalene-1,2-diamines. This type of N-C atropisomers is stabilized by intramolecular hydrogen bond and the method features a broad range of substrates, high yields and ee values, providing a strategy to chirality transfer via the modification of N-C atropisomers.
Bioinspired palladium‐catalyzed intramolecular cyclization of amino acid derivatives containing a vinyl iodide moiety by C−H activation enabled rapid access to a wide range of functionalized proline ...derivatives with an exocyclic olefin. To demonstrate the practicality of this methodology, the functionalized prolines were used as intermediates for the synthesis of several natural products: lucentamycin A, oxotomaymycin, oxoprothracarcin, and barmumycin.
Bioinspired palladium(II)‐catalyzed intramolecular cyclization of amino acid derivatives containing a vinyl iodide moiety by C−H activation enabled rapid access to a wide range of functionalized proline derivatives with an exocyclic double bond. Such functionalized prolines were used as intermediates for the total synthesis of several natural products: lucentamycin A, barmumycin, oxotomaymycin, and oxoprothracarcin.
Given the worldwide effort to improve crop drought resistance, it is crucial to understand the mechanisms of root system adaptation of ploidy wheat to water‐deficient environments. A meta‐analysis ...was performed to examine the changes in root system mechanisms under drought conditions. Data used in the analysis were drawn from 192 papers, taking into account wheat ploidy levels as well as pot and field studies. The results illustrated that water stress reduced grain yield and aboveground biomass to a greater extent in diploid and tetraploid compared with hexaploid genotypes. In contrast, drought reduced root biomass, root surface area and root volume more in hexaploid than in diploid and tetraploid wheat. Under water‐limited conditions, diploid and tetraploid genotypes exhibited greater root biomass and root length densities in the topsoil. Hexaploid genotypes greatly reduced root biomass and root length density in the topsoil and maintained higher root biomass and root length density in subsoil. These genotypes also showed smaller root diameter and xylem centre vessel diameter under drought conditions. The analysis revealed that grain yield was negatively correlated with topsoil root biomass and root length density, root volume, root diameter and xylem centre vessel, but positively correlated with subsoil root mass, root length density and root vigour. The study demonstrated that domestication and selection pressures of ploidy wheat have altered wheat root system traits while improving grain yield. Greater root mass and root length densities in the subsoil facilitate access to soil moisture from deep layers, contributing to high yields in drought environments.
We investigate the chiral phase structure of three flavor QCD in a background U(1) magnetic field using the standard staggered action and the Wilson plaquette gauge action. We perform simulations on ...lattices with a temporal extent of N τ = 4 and four spatial extents of Nσ = 8, 16, 20 and 24. We choose a quark mass in lattice spacing as a m = 0.030 with corresponding pion mass estimated as m π ∼ 280 MeV such that there exists a crossover transition at vanishing magnetic fields, and adopt two values of magnetic field strength in lattice spacing a √eB ≃ 1.5 and 2 corresponding to eB/m2π ∼ 11 and 20, respectively. We find that the transition becomes stronger in the presence of a background magnetic field, and turns into a first order as seen from the volume scaling of the order parameter susceptibility as well as the metastable states in the time history of the chiral condensate. On the other hand, the chiral condensate and transition temperature always increase with B even within the regime of a first order phase transition. This suggests that the discrepancy in the behavior of chiral condensates and transition temperature as a function of B between earlier lattice studies using larger-than-physical pion masses with standard staggered fermions and those using physical pions with improved staggered fermions is mainly due to lattice cutoff effects.
Crop avoidance and tolerance strategies are critical adaptive mechanisms of drought stress and play different roles in grain yield. However, little is known about the contribution of these two ...mechanisms to grain yield in old and modern wheat genotypes. Here, pot and field experiments were carried out to characterize and compare the mechanisms of drought avoidance and drought tolerance, and determine their differential contributions to the yield in six wheat genotypes. The pot experiment results demonstrated that the old genotypes acquired a better avoidance ability to adapt to drought stress. These avoidance abilities include larger root systems, lower leaf areas, low stomatal conductance, pale green leaf colour, higher degrees of leaf rolling and leaf waxiness. The modern genotypes displayed stronger drought tolerance advantages, such as high osmotic adjustment and antioxidant enzyme activity, and a smaller root system. Our field experiment further showed that under severe water‐deficit conditions, the old genotypes with stronger drought avoidance traits had higher yields and water use efficiency (WUEg), whereas the modern genotypes with strong drought tolerance characteristics produced higher yields and had higher WUEg under mild and intermediate water deficits. The results indicate that the relative contribution of drought tolerance and drought avoidance to grain yield depends to a large extent on the degree of drought stress and genotypes. Understanding the differential plant response depending on genotype and drought stress may help plant breeders develop drought‐resistant varieties suitable for drought‐prone environments under anticipated climate change scenarios.
An asymmetric intramolecular hydroalkylation of unactivated internal olefins with tethered cyclic ketones was realized by the cooperative catalysis of a newly designed chiral amine (SPD‐NH2) and PdII ...complex, providing straightforward access to either bridged or fused bicyclic systems containing three stereogenic centers with excellent enantioselectivity (up to 99 % ee) and diastereoselectivity (up to >20 : 1 dr). Notably, the bicyclic products could be conveniently transformed into a diverse range of key structures frequently found in bioactive terpenes, such as Δ6‐protoilludene, cracroson D, and vulgarisins. The steric hindrance between the Ar group of the SPD‐NH2 catalyst and the branched chain of the substrate, hydrogen‐bonding interactions between the N−H of the enamine motif and the C=O of the directing group MQ, and the counterion of the PdII complex were identified as key factors for excellent stereoinduction in this dual catalytic process by density functional theory calculations.
We developed a novel SPD‐NH2 organocatalyst that works cooperatively with a PdII complex to catalyze the asymmetric intramolecular hydroalkylation. It demonstrates great reactivity, enantio‐ and diastereoselectivity (up to 99 % ee and 20 : 1 dr). Moreover, bridged or fused bicyclic systems can be conveniently transformed into diverse di‐, tri‐, and tetracyclic scaffolds for further conversion into biologically important compounds.
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