Influence of Non-Kolmogorov Turbulence on Bit-Error Rates in Laser Satellite Communications

In satellite–ground laser communications, atmospheric turbulence in the link degrades the performance of the system, so it is very important to estimate its influence on the performance of the system. The bit-error rate (BER) is an important parameter to indicate the communication performance of the system, which is directly used to judge the quality of the communication system. Using the results of our two previous papers, we analyze the joint influence of Kolmogorov turbulence from the ground up to 6 km and non-Kolmogorov turbulence above 6 km on the BER. These kinds of turbulence are associated respectively with the uplink and the downlink propagation channels for the geosynchronous orbit satellite communication system.     

Interaction between trelagliptin and pepsin through spectroscopy methods and molecular dynamics simulation

The interaction between trelagliptin and pepsin was probed through spectroscopy methods and molecular dynamics simulation. Results of fluorescence lifetime and fluorescence spectroscopy analysis showed that trelagliptin can spontaneously interact with pepsin through a static quenching. This interaction was mainly driven by hydrogen bonding and van der Waals, as evident from thermodynamic parameters and molecular dynamics simulation. The microenvironment of tyrosine residues and the secondary structure of pepsin were slightly influenced by trelagliptin based on synchronous fluorescence, three-dimensional fluorescence, and circular dichroism spectra. In addition, the activity of pepsin was hardly affected by the insertion of trelagliptin. Molecular dynamics simulations were used to further analyze the pepsin–trelagliptin complex. This study provides useful information for binding mechanisms of trelagliptin on pepsin.     

Facile preparation of ZrCO composite aerogel with high specific surface area and low thermal conductivity

A novel ZrCO composite aerogel is synthesized using zirconium oxychloride and resorcinol–formaldehyde (RF) as precursors through the sol–gel route and carbothermal reduction process. The effects of different Zr/R molar ratios and calcination temperatures on the physical chemistry properties of ZrCO aerogels are investigated. The ZrCO composite aerogel consists of the C/ZrO₂/ZrC ternary aerogel. The results show that with the increase of R/Zr molar ratios, the specific surface area and bulk density increase with calcination temperature up to 1300?°C, but decrease at even temperature (1500?°C). The specific surface area is as high as 637.4?m²/g for ZrCO composite aerogel (R:Zr?=?2:1), which was higher than ever reported. As the heat-treatment temperature increases to 1500?°C, the ZrC crystalline phase occurs and the t-ZrO₂ phase still appears within the composite. The thermal conductivity of the carbon fiber mat-reinforced composite aerogel is as low as 0.057?W/m/K at room temperature (25?°C).

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Diastereo‐ and Enantioselective Palladium‐Catalyzed Dearomative [3+2] Cycloaddition of 3‐Nitroindoles

Diastereo‐ and enantioselective cycloaddition of 3‐nitroindoles with vinyl aziridine was realized under Pd‐catalysis using commercially available Walphos as the ligand, affording pyrroloindolines in high yields with high diastereo‐ and enantioselectivities. The reaction can be scaled up to a gram scale and the reaction products are easily converted to amino pyrroloindoline and other pyrroloindoline derivatives.     

Isolation and structure determination of a new flavone glycoside from seed residues of seabuckthorn (Hippophae rhamnoides L.)

In this study, a valid method was established for the isolation and purification of flavone glycosides from Hippophae rhamnoides L. seed residues using high-speed counter-current chromatography in one step, with a solvent system of ethyl acetate-methanol-n-butyl alcohol-water (9:1:0.5:9, v/v/v/v). A total of 28.8 mg compound I and 57.3 mg compound II were obtained from 200 mg of flavone H-glycosides rich extract, with purities of 98.3 and 96.4%, respectively. The structures of two compounds were identified by MS and NMR. 3-O-β-D-Sophorosylkaempferol-7-O-{3-O-[2(E)-2,6-dimethyl-6-hydroxyocta-2,7-dienoyl]}-α-L-rhamnoside is compound I and compound II named hippophanone is a new compound were identified by MS and NMR. The method was efficient and convenient, which could be used for the preparative separation of flavone glycosides from H. rhamnoides L. seed residues.     

A Robust Metal-Organic Framework with Scalable Synthesis and Optimal Adsorption and Desorption for Energy-Efficient Ethylene Purification

Adsorptive separation is an energy-efficient alternative, but its advancement has been hindered by the challenge of industrially potential adsorbents development. Herein, a novel ultra-microporous metal-organic framework ZU-901 is designed that satisfies the basic criteria raised by ethylene/ethane (C₂H₄/C₂H₆) pressure swing adsorption (PSA). ZU-901 exhibits an “S” shaped C₂H₄ curve with high sorbent selection parameter (65) and could be mildly regenerated. Through green aqueous-phase synthesis, ZU-901 is easily scalable with 99 % yield, and it is stable in water, acid, basic solutions and cycling breakthrough experiments. Polymer-grade C₂H₄ (99.51 %) could be obtained via a simulating two-bed PSA process, and the corresponding energy consumption is only 1/10 of that of simulating cryogenic distillation. Our work has demonstrated the great potential of pore engineering in designing porous materials with desired adsorption and desorption behavior to implement an efficient PSA process.     

LC-DAD-ESI-MS Characterization of Carbohydrates Using a New Labeling Reagent

A novel labeling reagent 1-(2-naphthyl)-3-methyl-5-pyrazolone (NMP) coupling to liquid chromatography with electrospray ionization mass spectrometry for the detection of carbohydrates from the derivatized rape bee pollen samples is reported. Carbohydrates are derivatized to their bis-NMP-labeled derivatives. Derivatives showed an intense protonated molecular ion at m/z [M+H]⁺ in positive-ion detection mode. The mass-to-charge ratios of characteristic fragment ions at m/z 473.0 could be used for the accurately qualitative analysis of carbohydrates. This characteristic fragment ion is from the cleavage of C2–C3 bond in carbohydrate chain giving the specific fragment ions at m/z [MH-C _m H_2m+1O _m -H₂O]⁺ for pentose, hexose and glyceraldehydes and at m/z [MH-C _m H_2m-1O _m+1-H₂O]⁺ for alduronic acids such as galacturonic acid and glucuronic acid (m = n ? 2, n is carbon number of carbohydrate). No interferences for all aliphatic and aromatic aldehydes presented in natural environmental samples were observed due to the highly specific parent mass-to-charge ratio and the characteristic fragment ions. The method, in conjunction with a gradient elution, offered a baseline resolution of carbohydrate derivatives on a reversed-phase Hypersil ODS-2 column. The carbohydrates such as mannose, galacturonic acid, glucuronic acid, rhamnose, glucose, galactose, xylose, arabinose and fucose can successfully be detected.