氨基清除树脂辅助合成2-(7-氟-3-氧-3,4-2H-苯并[b][1,4]噁嗪-6-基)异吲哚1,3-二酮

采用氨基清除树脂辅助合成方法,由6-氨基-7-氟-4-取代基-3(4H)-酮与取代邻苯二甲酸酐在冰醋酸中加热反应制备了2-(7-氟-3-氧-3,4-2H-苯并[b][1,4]噁嗪-6-基)异吲哚-1,3-二酮类化合物,纯度86％～95％．其结构经^1H NMR,IR和MS表征。     

Prediction of Chemical Inhibitors Efficiency for Reducing Deposition Thickness Using Artificial Neural Network

Prediction of efficiency of chemical inhibitors to mitigation of deposition thickness is a key to developing crude oil transportation process. In this work, a feed-forward artificial neural network (ANN) algorithm has been applied to predict the influence of the mitigation effect of ethylene-co-vinyl acetate (EVA) copolymer and its combination with chloroform (C), acetone (A), P-xylene (PX), and petroleum ether (PE) on the deposition thickness in the pipeline. An optimized three-layer feed-forward ANN model using properties of the oil pipeline such as: inlet oil temperature, environmental (coolant mixture) temperature, oil Reynolds numbers; properties of injected inhibitor such as molecular weight, boiling point, and amount of injection; and time is presented. Different networks are considered and trained using 62661 data sets; the accuracy of the network is validated by 20888 testing data sets. To verify the network generalization, 29 different experiment data sets of four different set of inhibitors have been considered. It is found that the proposed ANN model is an alternative to experimentation and predicts deposition thickness without experimentation, vast information, and tedious and time-consuming calculations.     

ASYMPTOTIC BEHAVIOR OF DYNAMIC EQUATIONS ON A PERIODIC TIME SCALES

We first prove some basic results on the periodic time scales, then on a special but practical periodic time scales T =∪[k(a + b),k(a + b) + a], the asymptotic behavior of x△ = px is explored with specific emphasis given to how the graininess of the time scales affects stability. At last, we analyze the asymptotic properties of the solutions of planar linear dynamic system, and obtain some sufficient conditions for the stability of the equalibium (0,0).     

Triple positive solutions of boundary value problems for p-Laplacian dynamic equations on time scales

A new triple fixed-point theorem is applied to investigate the existence of at least three positive solutions of boundary value problems for p-Laplacian dynamic equations on time scales.     

X-ray crystallographic and molecular modeling studies of 1-(2,6-difluorobenzoyl)-5-(4-chlorophenyl)biuret

Crystals of 1-(2,6-difluorobenzoyl)-5-(4-chlorophenyl)biuret (BFB), C₁₅H₁₀N₃O₃F₂Cl, were grown by evaporation from an acetonitrile solution. Two polymorphs were obtained. The first polymorph (BFB1) crystallized in the monoclinic space group P2₁/c (Z = 4) with unit cell a = 13.021(3), b = 5.293(1), c = 21.199(6) Å, and = 97.34(2)°. The second polymorph (BFB2) crystallized in the orthorhombic space group P 2₁2₁2₁ (Z = 8) with a = 10.513(1), b = 10.806(1), and c = 26.685(1) Å. The results of crystallographic and molecular modeling studies on BFB were in good agreement. The compound has an extended conformation with the benzene rings coplanar and the intervening –CONHCONHCONH– moiety rotated out of the plane due to steric effects from the two fluorine atoms.     

Synthesis of huperzine B through ring closing metathesis

Huperzine B and its analogues were obtained through ring closing metathesis of N-alkenyl amine to the corresponding tricyclic compounds.     

Design and Synthesis of Exocyclic Cyclitol Aziridines as Potential Mechanism-Based Glycosidase Inactivators

Cyclophellitol aziridines have found wide application as mechanism-based, covalent, and irreversible inhibitors of retaining glycosidases. These compounds, like their parent compound, cyclophellitol (a natural product retaining β-glucosidase inactivator), make use of the mechanism of action of retaining glycosidases, which process their substrate through the formation of a transient covalent intermediate. In contrast, inverting glycosidases, the other main family of glycosyl hydrolases, do not employ such a covalent intermediate, and, as a consequence, useful scaffolds for mechanism-based inhibitor design have yet to be discovered. In this work, we explore chemistries that allow for the construction of cyclitol aziridines with the aziridine electrophile attached in an exocyclic fashion, more distal from the anomeric carbon – thus putatively closer to an inverting glycosidase active site nucleophile. The developed chemistries have allowed for the synthesis of a focused library of differently N-substituted, α-and β-glucopyranose configured cyclitol aziridines for future evaluation as inhibitors or inactivators of α-and β-glucosidases alike.     

Commercialization of Ionic Liquids in Pursuit of Green Chemistry: Must we Each Become an Entrepreneur?

There will be common challenges to scaling-up any ionic liquids separations technologies which require very large volumes of ionic liquid. Some of these challenges are illustrated in this personal account which chronicles the extraction of chitin from shrimp shell from discovery to current commercialization efforts. The road being taken from discovery in an academic laboratory, through attempts to navigate the scaling-up to commercial scale using the vehicle of a faculty startup company is rewarding, but fraught with roadblocks, detours, and unexpected challenges. The differences in ‘technically feasible’ and ‘commercially viable’ are not always evident from the beginning of the journey, however, one wonders what achievements we miss as a Society because it was assumed to not be commercially viable.     

Parameter change test for location‐scale time series models with heteroscedasticity based on bootstrap

This study considers the bootstrap cumulative sum (CUSUM) test for a parameter change in location‐scale time series models with heteroscedasticity. The CUSUM test has been popular for detecting an abrupt change in time series models because it performs well in many applications. However, it has severe size distortions in many situations. As a remedy, we consider the bootstrap CUSUM test, particularly focusing on the CUSUM test based on score vectors, and demonstrate the weak consistency of the bootstrap test for its justification. A simulation study and data analysis are conducted for illustration.     

基于时域误差限的大规模系统自适应模型降阶

为满足解大规模动态系统常微分方程组对精度和速度权衡的要求,提出了一种基于误差限的大规模系统自适应模型降阶方法,其中方法的误差分析基于时域最大误差限,降阶方法基于SVD-Krylov子空间的方法.方法既考虑了算法的复杂性,又保证了算法的精度.通过对典型实例分析,结果表明该方法在给定相对误差限10~(-4)下得出的降阶阶数在不同频率下都能给出很好的近似精度,低频1~10Hz平均相对误差为1.1812×10~(-5),高频1~10GHz平均相对误差为5.6408×10~(-5),即在很宽的频率范围内都能满足精度要求.