Rational construction of metal–base synergetic sites on Au/Mg-beta catalyst for selective aerobic oxidation of 5-hydroxymethylfurfural

The selective aerobic oxidation of biomass-derived 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid (FDCA, a potential renewable substitution of fossil-based terephthalic acid to produce polyethylene 2,5-furandicarboxylate plastic) is an appealing transformation for constructing eco-friendly and sustainable chemical processes. Au supported catalysts have showed encouraging performances for this well-received conversion, whose catalytic behavior was greatly affected by the adopted support derived from the existence of metal-support interactions. Herein, a series of Mg-Beta zeolites were hydrothermally synthesized via developed structural reconstruction, which were employed as basic supports for Au catalysts to construct bifunctional catalysts. The relationship between structure (Au particle size, basicity within zeolites and Auδ+ contents) and FDCA yield was concretely established. The conclusion was made that the utilization of Mg-Beta zeolites with strong basicity as the support could not only improve the FDCA yield but also decrease the amount of additional base. Furthermore, the possible reaction mechanism was also proposed via tracking time-dependent variations of corresponding organics and controlled experiment. This work provides some guidance for rationally designing multifunctional catalysts in the view of integrating metal catalysts with metallosilicate zeolites, which was beneficial to the catalytic upgrading of organic compounds with multiple functional groups.

Changes in Tropical Cyclone Number in the Western North Pacific in a Warming Environment as Implied by Classical Thermodynamics

Observational analyses show that the equatorial trough in the western North Pacific (WNP) is a well-known origin for tropical cyclones (TC) which have tended to weaken in intensity and decrease in number during the last several decades under global warming. A scientific problem then arises as to why higher sea surface temperatures (SSTs), one of the necessary conditions for typhoon genesis, can cause a weakened equatorial trough and a decreased TC number. In this paper, the WNP is taken as an example to illustrate a possible mechanism for the above-mentioned seemingly counterintuitive phenomena and explain the causality between the unusually heterogeneous pattern of SSTs in a warming environment and TC number in the WNP. This mechanism is based substantially on the second law of thermodynamics.

Synoptic-Scale Analysis on Development and Maintenance of the 19–21 July 2021 Extreme Heavy Rainfall in Henan,Central China

In this paper,synoptic-scale analyses of frontogenesis,moisture budget,and tropospheric diabatic heating are performed to reveal the development and maintenance mechanisms for the extreme heavy rainfall in Henan Province of central China from 19 to 21 July 2021,based on station observations and the ECMWF Reanalysis version 5(ERA5)data.The results demonstrate that owing to the blocking effect of local topography,low-level wind convergence in Henan appeared underneath high-level divergence,conducive to development and maintenance of a midtropospheric low-pressure system saddled by the Asian continental high and the western Pacific subtropical high(WPSH),during the extreme heavy rainfall.In the lower troposphere,frontogenesis occurred in the θ_(se) intensive region,as a result of the divergence and horizontal deformation(which play equally important roles),generating frontal secondary circulation with strong vertical motion favorable to heavy rainfall.Moisture budget analysis reveals that 1)with the continuous strengthening of the easterly wind from the north side of Typhoon In-Fa(2106),strong wind shear and orographic uplift led to abnormally strong convergence of water vapor flux in the boundary layer in Henan;2)there occurred extremely strong net inflow of moisture in the boundary layer from the east.Horizontally,both the apparent heat source and the moisture sink coincided with the area of heavy rainfall;vertically,however,Q_(1)exhibited a single peak with the heating center in the middle and upper troposphere,while large Q_(2)values evenly resided over 850–400 hPa;and Q_(1)(Q_(2))was dominated by vertical(horizontal)transport of potential temperature(moisture).These indicate that the latent heat release from condensation of initial heavy rainfall provided a positive feedback,leading to increasingly heavy precipitation.All these synoptic settings sustained the extreme rainfall process.

Leaky modes and the first arrivals in cased boreholes with poorly bonded conditions

The generation mechanism of the first arrivals in the cased boreholes for the poorly bonded conditions is investigated. Based on the analyses of the Riemann surface structure of the characteristic function, the dispersion features, excitation spectra and contributions of modes excited in the cased boreholes with different cementing types are studied. The phase velocity dispersion studies of leaky modes show that high-order modes form "plateau" regions with one approximate velocity denoted by v separated by their cutoff frequencies, in which the phase velocity changes little with a considerable frequency range, while the group velocity keeps a relatively constant high value. Usually, the operation frequency range of a specific cementing evaluation acoustic logging tool is covered by such a "plateau" region. Mode excitation and contribution analyses show that the first arrivals in the cased boreholes for the poorly bonded conditions are the contributions from leaky modes, where the traveling velocity of the first arrivals processed by slowness time coherence(STC) method is equal to the approximated velocity v. Analyses on generation of leaky modes in the cased boreholes supplement the understanding of the generation mechanism of the first arrivals.

Qualitative and quantitative analysis of glucosinolates and nucleosides in Radix Isatidis by HPLC and liquid chromatography tandem mass spectrometry

Multi-component fingerprinting and quantitation of the glucosinolates and nucleosides in samples of Radix Isatidis have been carried out using high-performance liquid chromatography with diode-array detection and electrospray ionization tandem mass spectrometry(HPLC–DAD–ESI/MS).Five nucleosides together with one glucosinolate were identified by comparing retention times,ultraviolet spectra,mass spectra and/or empirical molecular formulae of reference compounds.Quantitation of these six compounds was carried out simultaneously by HPLC on a Phenomenex Luna C18 column using gradient elution with methanol and water and detection at 254 nm.All calibration curves were linear(r40.9994)within test ranges.Limits of detection and quantitation were 0.33 ng and 2.50 ng on column,respectively.Intra-and inter-day precision(as relative standard deviation)for all analytes was o2.19%with recoveries in the range 99.6%–101.8%at three concentration levels.The validated method was successfully applied to fingerprinting and assay of 25 batches of Radix Isatidis sourced from different geographical regions of China.The method is simple and reliable and has potential value in the quality control of Radix Isatidis.

Reply to “Comment on ‘A numerical investigation of the acoustic mode waves in a deviated borehole penetrating a transversely isotropic formation' ”

We appreciate the comment from Horne,Miller and Wang on the paper‘A numerical investigation of the acoustic mode waves in a deviated borehole penetrating a transversely isotropic formation’by Liu et al.(2015)[1],for the opportunity to consider and clarify the group and phase velocity issue in sonic logging with a deviated borehole penetrating a VTI formation.We re-read the paper by Liu et al.[1]and did some numerical tests and analyses.After discussions we agree that at