Crystal Structure and Conformation of an Imino Sugar

The title compound 3 was synthesized and characterized by IR,NMR and H-RMS,and its crystal structure was determined by X-ray diffraction analysis. The crystal is of monoclinic system (C16H23NO7S,Mr=373.41),space group P21,with a=12.000(2),b=5.5970(11),c=13.689(3),β=93.25(3)°,V=917.9(3)3,Z=2,Dc=1.351 g/cm3,F(000)=396,μ=0.213 mm-1,the final R=0.0489 and wR=0.0777 for observed reflections (I > 2σ(I)). Three intramolecular and three intermolecular hydrogen bonds were found. The absolute configuration of this molecule was confirmed by comparing with the original material.     

基于有限单元柔度法的材料与几何双重非线性空间梁柱单元

从有限单元柔度法的基本思想出发,基于完全拉格朗日格式(TL格式),建立了能考虑材料与几何双重非线性的一般化空间梁柱单元,适用于满足Euler-Bernoulli梁柱二阶分析理论假定的空间杆系结构非线性分析。另外,在梁柱单元截面分析中引入纤维模型,使其适用于解决钢筋混凝土这类复合材料结构的非线性分析问题。对钢筋混凝土双向偏心受压柱试验结果的模拟分析表明,本文所提方法是正确、可靠的,能有效地分析钢筋混凝土框架柱的材料与几何双重非线性问题。     

Simultaneous capillary GC of acids and sugars as their silyl(oxime) derivatives: Quantitation of chlorogenic acid,raffinose, and pectin substances

Our GC-MS method for the simultaneous quantitation of sugars and acids as their silyl(oxime) derivatives, from one solution by one injection, has been extended to the reproducible determination of high molecular weight compounds sensitive to decomposition yet requiring a high evaporation temperature (e.g. chlorogenic acid and rffinose) and for the quantitation of the decomposition products of pectin (i.e., for the determination of galacturonic acid at low ng levels in the presence of a 10–100 fold excess of glucose eluting just before the acid). The optimized GC procedure has been used for quantitation of the sugar and acid (including chlorogenic acid) composition of potato samples, and for the determination of the increasing amount of the decomposition products of pectin substances in apple pulp after different storage times.     

Synthesis and Characterization of Novel Thiosemicarbazones Bearing Sugar Moieties

IntroductionIt is well known that carbohydrates play importantroles in a wide variety of biological processes[1], suchas cell adhesion to the extracellular matrix and cell sig-naling. They can also act as the ligands for growth fac-tors[2,3].Substituted t…     

Experiments on transonic limit-cycle-flutter of a flexible swept wing

The aeroelastic behavior of wing models is nonlinear particularly in the transonic speed range. The interaction between aerodynamic and structural forces can lead to the occurrence of Limit-Cycle Oscillations (LCOs). If in addition the wing model is flexible and backward swept, the kinematic coupling between bending and torsion makes the situation even more complex.In the research project “Aerostabil” such a wing was investigated, which was equipped with pressure transducers in three sections and accelerometers. The experiments were performed in the adaptive test section of the transonic wind tunnel TWG in Göttingen. Already Dietz et al. (2003) have reported about experimental details and preliminary results. Based on these data Bendiksen (2008) studied numerically LCO-flutter behavior using a very similar, theoretical model (G-wing) and Stickan et al. (2014) used the original data as a LCO flutter test case. The influence of flexibility on the steady aerodynamics of the wing was described in Schewe & Mai (2018). In this paper now the flutter experiments with the same flexible model were analyzed systematically in the transonic range 0.84 <Ma <0.89 and for six angles of attack from 1.46°to 2.7°. Maps of stability, LCO amplitudes and instantaneous pressure distributions are presented. It was found that unstable regions are islands, whose extent depends on the angle of attack. A LCO test case, already treated in the literature is examined in more detail. The analysis of the time functions showed that during LCO-flutter the motion induced aerodynamic sectional lift forces particularly in the outer wing are asymmetric and thus acting as amplitude limiter. The reason for the asymmetry lies in the shock/boundary layer interaction. The test case, containing the stages of built-up and the transition to the limit cycle provides an excellent opportunity for improving our knowledge about LCOs and for code validation purposes.     

两关节压力驱动柔性仿生机器鱼的设计与仿真

为研究设计一种柔软度高、环境适应性强的新型仿生机器鱼, 模仿鲨鱼外形及鲔科鱼类的游动姿态, 设计了一种采用液压柔性驱动结构的仿生机器鱼. 针对单关节液压驱动柔性机器鱼存在其C型摆动姿态不符合鲔科鱼类摆动规律的问题, 采用两关节液压柔性驱动模拟鱼类S型摆动, 并根据液压柔性驱动器原理设计仿生鱼的内部结构. 依据理论波动方程确定机器鱼的摆动幅值, 借助数值模拟计算施加在柔性驱动器内部的压强载荷大小, 并分析计算液压柔性驱动器的驱动效率. 应用有限元分析软件模拟仿生鱼在流体中的自主游动过程, 并将两关节机器鱼与单关节机器鱼的自主巡游过程进行对比仿真, 获得两种机器鱼在流体中自主巡游时的运动姿态、游动速度及流场情况. 结果表明, 在相同的频率与尾鳍摆幅下, 两关节柔性机器鱼的巡游平均速度为0.29 BL/s (BL为鱼体体长), 高于单关节机器鱼巡游平均速度0.15 BL/s, 且由速度矢量图可得出两关节仿生鱼的S型摆动姿态更接近真实鱼类摆动规律, 并在运动过程中会产生一系列离散的反向卡门涡街, 推进效率高.      

Glucosamine and maltol anchored Zinc(II) complex of COVID-19 health supplement relevance: DFT collaborated spectroscopic formulation with profound biological implications

In association with other antiviral drugs, Zinc is specially administered to the patients suffering from novel coronavirus infectious disease (nCOVID). Zn, maltol, and glucosamine are famous food and drug additives. The supplements made from them are helpful in minimizing malnutrition problems, and in enhancing immune power. Due to the well-pronounced effects of all these three components in the food and medicinal industry, a novel sugar Zn(II) complex of the general composition, [Zn(gls)(mal)], where Hmal is maltol and Hgls is referred to as glucosamine, was synthesized and formulated. The physicochemical methods that were used to establish the molecular structure include elemental analysis, 1HNMR, FT-IR, UV–Vis., thermal and mass spectrometry. Physical properties like decomposition temperature and molar conductance were also examined. The experimental results at each step of characterization were validated/compared with density functionalized spectroscopic/spectrometric data using the LANL2DZ basis set for the metal atom and 6–31 g(d,p) for other atoms under the B3LYP functional. From the study, a suitable square planar geometry is suggested for the complex. Among biological implications, superoxide dismutation (SOD) and antimicrobial actions were studied. Also, virtual screening using SWISS ADME and Autodock 4.0 program (against 6X2B, SARS-CoV-2 u1S2q 2 RBD Up Spike Protein Trimer) were evaluated for the complex. Good interactions were scored by glucosamine and the complex. The results obtained from antimicrobial sensitivity indicate low inhibition zones, but from the SOD data, the complex has shown satisfactory antioxidant behavior. Therefore, the proposed food supplement could act as a good antioxidant agent and could keep the flora of the intestinal tract less disturbed while going through a metabolic pathway.     

Effect of Alanine and Glycine on the Assembly of Surfactant‐like Peptides with Tyrosine as Hydrophilic Head in Basic Solution

Surfactant‐like peptides (SLPs ) can self‐assemble into various nanostructures, which have shown great potential for a variety of biomedical and biotechnological applications. In this work, two SLPs , V₄Y , and V₄AGY , were designed and synthesized, both of which had hydrophobic head valines (V) with large side‐chain steric hindrance effect and the hydrophilic head tyrosine (Y) with a rigid ring and two negative charges in the basic solution. Fourier transform infrared and circular dichroism studies confirmed their different secondary structures, whereas atomic force microscopy and dynamic light scattering characterized the difference in their morphologies. In solution, they formed different secondary structures. Correspondingly, V₄Y and V₄AGY formed noncompact spherical aggregates and a spiral clubbed structure, respectively. In V₄AGY , the introduction of alanine (A) and glycine (G) increased the molecule's flexibility and increased the distance between the tyrosine and four continuous valines, so as to weaken the synergistic action of electronic repulsion and steric hindrance and strengthen the intermolecular hydrogen bond beneficial to β‐sheet formation and the axial growth of the self‐assembly. Therefore, the flexibility of the molecule and the side‐chain steric effect of the two heads of SLPs are non‐negligible in the tuning process of peptide self‐assembly, in addition to hydrogen‐bonding, hydrophobic, and electrostatic interactions.     

Determination of Phenolic Compounds and Coumarins in Sugar Cane Spirit Aged in Different Species of Wood

The identities and quantities of the phenolic compounds and coumarins in twelve samples of sugar cane spirit aged in Quercus sp., Amburana cearensis, Cariniana legalis, Castanea sativa Mill, Ocotea sp., Cotyledon orbiculata L., and Hymenaea sp. casks were determined. These compounds have a direct influence on the sensory characteristics of aged beverages; some of them are considered to be markers for the aging process. The analysis of phenolic compounds was performed by HPLC. Solid phase extraction (SPE) was also used for the determination of coumarins. The concentrations of the principal compounds extracted varied according to the species of wood. The concentrations of total phenolic compounds ranged from 0.08 for a sample stored in a 4000-L jatobá barrel for a period of six months to 40.9 mg · L^?1 for a sample aged in a 50000-L oak barrel for a period of 48 months. The use of the SPE technique removed interfering compounds from the samples, thereby improving the detection of coumarin.     

Metal-Dependent and Selective Crystallization of CAU-10 and MIL-53 Frameworks through Linker Nitration

The reaction of the V-shaped linker molecule 5-hydroxyisophthalic acid (H₂L⁰), with Al or Ga nitrate under almost identical reaction conditions leads to the nitration of the linker and subsequent formation of metal–organic frameworks (MOFs) with CAU-10 or MIL-53 type structure of composition [Al(OH)(L)], denoted as Al-CAU-10-L^{0, 2, 4, 6} or [Ga(OH)(L)], denoted as Ga-MIL-53-L². The Al-MOF contains the original linker L⁰ as well as three different nitration products (L², L⁴ and L^4/6), whereas the Ga-MOF mainly incorporates the linker L². The compositions were deduced by ¹H NMR spectroscopy and confirmed by Rietveld refinement. In situ and ex situ studies were carried out to follow the nitration and crystallization, as well as the composition of the MOFs. The crystal structures were refined against powder X-ray diffraction (PXRD) data. As anticipated, the use of the V-shaped linker results in the formation of the CAU-10 type structure in the Al-MOF. Unexpectedly, the Ga-MOF crystallizes in a MIL-53 type structure, which is usually observed with linear or slightly bent linker molecules. To study the structure directing effect of the in situ nitrated linker, pure 2-nitrobenzene-1,3-dicarboxylic acid (m-H₂BDC-NO₂) was employed which exclusively led to the formation of [Ga(OH)(C₈H₃NO₆)] (Ga-MIL-53-m-BDC-NO₂), which is isoreticular to Ga-MIL-53-L². Density Functional Theory (DFT) calculations confirmed the higher stability of Ga-MIL-53-L² compared to Ga-CAU-10-L² and grand canonical Monte Carlo simulations (GCMC) are in agreement with the observed water adsorption isotherms of Ga-MIL-53-L².