Role of gas cooling time on crystalline morphology and mechanical property of the HDPE parts prepared by gas-assisted injection molding

In this study, the hierarchical crystalline structures of high-density polyethylene (HDPE) samples molded by gas-assisted injection molding (GAIM) with different gas cooling times were characterized via scanning electron microscopy, two-dimensional wide-angle X-ray scattering, tensile testing techniques, and differential scanning calorimetry, respectively. It was found that the shish-kebab, the oriented lamellae, and common spherulite structures orderly distributed from the skin region to gas channel region of samples. More importantly, the wider area with highly oriented structure (shish-kebab) was obtained in the samples with longer gas cooling time, in that the longer gas cooling time tends to increase the cooling rate of polymer melt, and then much more stretched chains are retained. Although lower crystallinity, the higher degree of orientation, and much more shish-kebab structures lead to significant reinforcement from 28 to 785 MPa of the samples with gas cooling time of 0.5 s to 32 and 879 MPa of the samples with gas cooling time of 20 s for tensile strength and modulus, respectively. Finally, combined the HDPE molecular parameter with characteristic of the GAIM temperature field and flow field, the formation and stability of crystalline morphology in different regions of sample were discussed.     

Waste Biogas Residue from Cassava Dregs as Carbon Source to Produce Galactomyces sp. Cczu11-1 Cellulase and its Enzymatic Saccharification

In the conversion of cassava starch dregs to biogas by anaerobic fermentation, the biogas residue (BR) containing lignocellulosic materials still remained in the environment. In order to effectively utilize BR, the complexed 1-methyl-3-methylimidazolium dimethyl phosphate ([Mmim]DMP) media were used for pretreating cellulosic materials. After the optimization of pretreatment, the IL [Mmim]DMP-HCl-water (78.5:1.5:20, w/w/w) pretreament media were used for pretreating BR at 130 °C for 30 min. Furthermore, BR pretreated could be effectively saccharified by cellulase of Galactomyces sp. CCZU11-1. Moreover, BR could be used as a cheap carbon source for the production of Galactomyces sp. CCZU11-1 cellulase. After the culture optimization, the optimal culture conditions were obtained as follows: BR 5 g/L, (NH₄)₂SO₄ 5 g/L, K₂HPO₄ 2 g/L, MgSO₄ 0.2 g/L, NaCl 1 g/L, PEG6000 4 g/L, pH 5.5, and culture temperature 30 °C. After the fermentation for 6 days, the FPA and CMCase were 26.2 and 52.8 U/mL, respectively. In conclusion, waste BR could be chosen as a promising feedstock for biofuels.     

Nitrobenzene degradation by micro-sized iron and electron efficiency evaluation

The effect of pH, temperature, zero-valent iron (ZVI) dosage and reaction duration on nitrobenzene (NB) degradation by micro-sized ZVI was investigated in batch experiments and the electron efficiency (EE) was evaluated at constant pH. The experimental results showed that the reaction rate constant attained 0.616 min^?1, which was far higher than reported in previous studies. The decrease in pH and increase in temperature of the reaction bath promoted the reaction kinetics. ZVI dosage and reaction duration were two key factors affecting NB reduction and EE. A lower ZVI dosage and a slightly longer reaction duration could afford an optimised EE and optimum NB removal. A prolonged reaction or too high a ZVI dosage resulted in increased ZVI waste.     

液体闪烁计数法测定生物塑料中生物基含量

研究并建立了液体闪烁计数法测量生物塑料中生物基含量。首先将生物塑料样品充分燃烧,通过碳的转移与固定,最终催化合成液态苯。通过液体闪烁计数器对液体苯中的放射性核素14C衰变进行计数,从而计算生物塑料样品中生物基的含量。生物塑料样品加标回收率为98.5%~101%,相对标准偏差为0.2%。方法可用于生物塑料中生物基含量检测。     

硫脲络合–火焰原子吸收光谱法测定低硅铝合金中的银含量

采用硫脲络合–火焰原子吸收光谱法测定低硅铝合金中的银元素含量。实验探讨了酸度及硫脲用量对银测定的影响及铝合金中基体元素与共存元素对银元素分析线的干扰情况。结果表明:选用9%的盐酸和3%的硝酸溶解试样最好,加入5 mL 50 g/L硫脲溶液可消除氯离子对试验结果的影响,基体铝元素和其它共存元素不干扰银的测定。根据低硅铝合金中银元素的含量范围,合成系列标准溶液,建立工作曲线,工作曲线的线性范围为0.05%~0.50%。银元素含量为0.30%的样品测定结果的相对标准偏差为0.15%(n=8),标准加入回收率为96.8%~98.5%。该方法操作简便、重现性好、测量结果准确可靠。     

Benzidine/Quinoidal-Benzidine-Linked,Superbenzene-Based π-Conjugated Chiral Macrocycles and Cyclophanes

Synthesis of fully conjugated cyclophanes containing large-size polycyclic aromatics is challenging. Now, three benzidine-linked, hexa-peri-hexabenzocoronene (superbenzene)-based ortho-, para-, and meta-cyclophanes are synthesized through intermolecular Yamamoto coupling reaction of structurally pre-organized precursors. Subsequent oxidative dehydrogenation gave the corresponding quinoidal benzidine-linked cyclophanes. Their geometries were confirmed by X-ray crystallographic analysis and their electronic properties were investigated by electronic absorption, cyclic voltammetry, and DFT calculations. The quinoidal benzidine-linked cyclophanes show thermally populated paramagnetic activity with a relatively large singlet-triplet energy gap. Two enantiomers for the ortho-cyclophanes ( 1-NH and 1-N ) were isolated and their chiral figure-of-eight macrocyclic structures were identified. The cage-like cyclophanes 2-NH and 3-NH with concave surface can selectively encapsulate fullerene C₇₀.     

Pressure-Suppressed Carrier Trapping Leads to Enhanced Emission in Two-Dimensional Perovskite (HA)2(GA)Pb2I7

A remarkable PL enhancement by 12 fold is achieved using pressure to modulate the structure of a recently developed 2D perovskite (HA)₂(GA)Pb₂I₇ (HA=n-hexylammonium, GA=guanidinium). This structure features a previously unattainable, extremely large cage. In situ structural, spectroscopic, and theoretical analyses reveal that lattice compression under a mild pressure within 1.6 GPa considerably suppresses the carrier trapping, leading to significantly enhanced emission. Further pressurization induces a non-luminescent amorphous yellow phase, which is retained and exhibits a continuously increasing band gap during decompression. When the pressure is released to 1.5 GPa, emission can be triggered by above-band gap laser irradiation, accompanied by a color change from yellow to orange. The obtained orange phase could be retained at ambient conditions and exhibits two-fold higher PL emission compared with the pristine (HA)₂(GA)Pb₂I₇.     

Machine-Driven Chemoenzymatic Synthesis of Glycopeptide

Historically, researchers have put considerable effort into developing automation systems to prepare natural biopolymers such as peptides and oligonucleotides. The availability of such mature systems has significantly advanced the development of natural science. Over the past twenty years, breakthroughs in automated synthesis of oligosaccharides have also been achieved. A machine-driven platform for glycopeptide synthesis by a reconstructed peptide synthesizer is described. The designed platform is based on the use of an amine-functionalized silica resin to facilitate the chemical synthesis of peptides in organic solvent as well as the enzymatic synthesis of glycan epitopes in the aqueous phase in a single reaction vessel. Both syntheses were performed by a peptide synthesizer in a semiautomated manner.     

Asymmetric Coupling of Carbon-Centered Radicals Adjacent to Nitrogen: Copper-Catalyzed Cyanation and Etherification of Enamides

The first copper-catalyzed asymmetric cyanation and etherification reactions of enamides have been established, where a carbon-centered radical adjacent to a nitrogen atom (CRAN) is enantioselectively trapped by a chiral copper(II) species. Moreover, the asymmetric cyanation of vinyl esters was disclosed as well. These reactions feature very mild reaction conditions and high functional group tolerance, and give a series of chiral α-cyano amides, α-cyano esters and α-hemiaminals in good yields with excellent enantioselectivity. The chiral α-cyano amides can be easily converted into enantioenriched 1,2-diamines and amino acids.     

The Fe-N-C Nanozyme with Both Accelerated and Inhibited Biocatalytic Activities Capable of Accessing Drug–Drug Interactions

Emerging as a cost-effective and robust enzyme mimic, nanozymes have drawn increasing attention with broad applications ranging from cancer therapy to biosensing. Developing nanozymes with both accelerated and inhibited biocatalytic properties in a biological context is intriguing to peruse more advanced functions of natural enzymes, but remains challenging, because most nanozymes are lack of enzyme-like molecular structures. By re-visiting and engineering the well-known Fe-N-C electrocatalyst that has a heme-like Fe-N_x active sites, herein, it is reported that Fe-N-C could not only catalyze drug metabolization but also had inhibition behaviors similar to cytochrome P450 (CYP), endowing it a potential replacement of CYP for preliminary evaluation of massive potential chemicals, drug dosing guide, and outcome prediction. In addition, in contrast to electrocatalysts, the highly graphitic framework of Fe-N-C may not be obligatory for a competitive CYP-like activity.