Local lazy regression: making use of the neighborhood to improve QSAR predictions

Traditional quantitative structure-activity relationship (QSAR) models aim to capture global structure-activity trends present in a data set. In many situations, there may be groups of molecules which exhibit a specific set of features which relate to their activity or inactivity. Such a group of features can be said to represent a local structure-activity relationship. Traditional QSAR models may not recognize such local relationships. In this work, we investigate the use of local lazy regression (LLR), which obtains a prediction for a query molecule using its local neighborhood, rather than considering the whole data set. This modeling approach is especially useful for very large data sets because no a priori model need be built. We applied the technique to three biological data sets. In the first case, the root-mean-square error (RMSE) for an external prediction set was 0.94 log units versus 0.92 log units for the global model. However, LLR was able to characterize a specific group of anomalous molecules with much better accuracy (0.64 log units versus 0.70 log units for the global model). For the second data set, the LLR technique resulted in a decrease in RMSE from 0.36 log units to 0.31 log units for the external prediction set. In the third case, we obtained an RMSE of 2.01 log units versus 2.16 log units for the global model. In all cases, LLR led to a few observations being poorly predicted compared to the global model. We present an analysis of why this was observed and possible improvements to the local regression approach.     

Determination of volatile residual solvents in pharmaceutical products by headspace liquid-phase microextraction gas chromatography-flame ionization detector

This paper demonstrates headspace liquid-phase microextraction (HS-LPME) as used for the determination of volatile residual solvents in pharmaceutical products. This method is based on headspace liquid-phase microextraction capillary column gas chromatography. Under optimum conditions, the linerary of the method ranged from 1 to 1,000 mg l⁻¹. The limits of detection are 0.2–2.0 mg l⁻¹ and relative standard deviations (RSD) for most of the volatile solvents were below 10%. This novel method is applied to the analysis of volatile residual solvents in pharmaceutical products with satisfactory results.     

色酮吡唑啉酮骨架拼接二氢查尔酮类化合物的合成

以色酮-吡唑啉酮合成子(1）为原料,在三级胺N,N-二甲基乙醇胺催化下,与查尔酮发生Michael加成反应,合成了10个新型的色酮吡唑啉酮骨架拼接二氢查尔酮类化合物3a~3j,产率79%~90%, dr值为6/1~10/1, 其结构经¹H NMR, ¹³C NMR和HR-MS（ESI-TOF）表征。化合物3b的相对构型由单晶培养确定。该类化合物含有连续两个立体中心,包括一个季碳中心,可以为生物活性筛选提供物质基础。     

1,2-二(2-甲氧基苯基)-1,2-乙二胺的制备方法研究

手性1,2-二(2-甲氧基苯基)-1,2-乙二胺可作为有机小分子催化剂、金属配体前体广泛应用于多种有机合成反应之中,其可以消旋体为原料通过拆分得到。以廉价易得的邻甲氧基苯甲醛为原料,重点针对亚胺中间体还原过程中反应条件苛刻、后处理复杂等问题,首次利用Mg作为还原剂,在室温下,以93%的分离收率得到关键中间体3。通过该关键步骤的放大实验（92%）,进一步评价了该方法的应用潜力。      

悬浮态煅烧氧化铝熟料的试验研究

本文在一维煤粉试验炉内对高铝煤进行了直接悬浮态煅烧氧化铝熟料的试验研究,研究了不同炉温对熟料生成的影响,并对在不同温度下煅烧得到氧化铝熟料进行XRD分析。试验结果表明:在悬浮态下燃烧,燃烧温度高于1100℃以上时,完全可以生成氧化铝熟料,粉煤灰中氧化铝熟料生成量在1200℃最多。     

聚(2-甲氧基-5-辛氧基)对苯乙炔/Y_2O_3:Eu~(3+)纳米复合材料的光致电子转移效应

采用原位脱氯化氢缩合聚合法制备了聚(2-甲氧基-5-辛氧基)对苯乙炔/Y_2O_3:E~(3+)(PMOCOPV/Y_2 O_3:Eu~(3+))纳米复合材料。红外光谱证实了在Y_2O_3:Eu~(3+)表面的包覆层为PMOCOPV。紫外-可见吸收光谱表明与PMOCOPV相比,PMOCOPV/Y_2O_3:Eu~(3+)的最大吸收峰发生红移且强度提高。荧光光谱研究表明PMOCOPV/Y_2O_3:Eu~(3+)的最大发射波长发生红移且强度提高,荧光寿命得到增强,Y_2O_3:Eu~(3+)与PMOCOPV之间形成了光致电子转移体系,使得π电子离域程度增加,并且导致荧光量子效率提高。根据E_g与入射光子能量hv的关系,拟合了PMOCOPV/Y_2O_3:Eu~(3+)薄膜的光学禁带宽度,发现E_g减小。采用简并四波混频方法测试它们的三阶非线性极化率x~((3)),结果发现与PMOCOPV相比,PMOCOPV/Y_2O_3:Eu~(3+)纳米复合体的非线性光学响应逐渐增强,进一步说明PMOCOPV与Y_2O_3:Eu~(3+)之间形成了分子间光致电子转移体系,产生了复杂的分子间离域π电子非线性运动。     

Non-Markovian relaxation of a three-level system: quantum trajectory approach

The non-Markovian dynamics of a three-level quantum system coupled to a bosonic environment is a difficult problem due to the lack of an exact dynamic equation such as a master equation. We present for the first time an exact quantum trajectory approach to a dissipative three-level model. We have established a convolutionless stochastic Schr?dinger equation called the time-local quantum state diffusion (QSD) equation without any approximations, in particular, without Markov approximation. Our exact time-local QSD equation opens a new avenue for exploring quantum dynamics for a higher dimensional quantum system coupled to a non-Markovian environment.     

Efficient one-pot synthesis of Ag nanoparticles loaded on N-doped multiphase TiO2 hollow nanorod arrays with enhanced photocatalytic activity

The simultaneous Ag loaded and N-doped TiO₂ hollow nanorod arrays with various contents of silver (Ag/N-THNAs) were successfully synthesized on glass substrates by one-pot liquid phase deposition (LPD) method using ZnO nanorod arrays as template. The catalysts were characterized by Raman spectrum, field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscope (HRTEM), ultraviolet-vis (UV-vis) absorption spectrum and X-ray photoelectron spectroscopy (XPS). The results suggest that AgNO₃ additive in the precursor solutions not only can promote the anatase-to-rutile phase transition, but also influence the amount of N doping in the samples. The photocatalytic activity of all the samples was evaluated by photodegradation of methylene blue (MB) in aqueous solution. The sample exhibited the highest photocatalytic activity under UV light illumination when the AgNO₃ concentration in the precursor solution was 0.03 M, due to Ag nanoparticles acting as electron sinks; When the AgNO₃ concentration was 0.07 M, the sample performed best under visible light illumination, attributed to the synergetic effects of Ag loading, N doping, and the multiphase structure (anatase/rutile).     

Nonlinear Maps Preserving the Jordan Triple *-Product on Factor von Neumann Algebras

Let A and B be two factor von Neumann algebras. For A, B ∈ A, define by [A, B]_*= AB-BA~*the skew Lie product of A and B. In this article, it is proved that a bijective map Φ : A → B satisfies Φ([[A, B]_*, C]_*) = [[Φ(A), Φ(B)]_*, Φ(C)]_*for all A, B, C ∈ A if and only if Φ is a linear *-isomorphism, or a conjugate linear *-isomorphism, or the negative of a linear *-isomorphism, or the negative of a conjugate linear *-isomorphism.     

Recovering a space-dependent source term in a time-fractional diffusion wave equation

This work is concerned with identifying a space-dependent source function from noisy final time measured data in a time-fractional diffusion wave equation by a variational regularization approach. We provide a regularity of direct problem as well as the existence and uniqueness of adjoint problem. The uniqueness of the inverse source problem is discussed. Using the Tikhonov regularization method, the inverse source problem is formulated into a variational problem and a conjugate gradient algorithm is proposed to solve it. The efficiency and robust of the proposed method are supported by some numerical experiments.