A parameterized proximal point algorithm for separable convex optimization

In this paper, we develop a parameterized proximal point algorithm (P-PPA) for solving a class of separable convex programming problems subject to linear and convex constraints. The proposed algorithm is provable to be globally convergent with a worst-case O(1 / t) convergence rate, where t denotes the iteration number. By properly choosing the algorithm parameters, numerical experiments on solving a sparse optimization problem arising from statistical learning show that our P-PPA could perform significantly better than other state-of-the-art methods, such as the alternating direction method of multipliers and the relaxed proximal point algorithm.     

A new model for sparse and low-rank matrix decomposition

The robust principal component analysis (RPCA) model is a popular method for solving problems with the nuclear norm and $\ell_1$ norm. However, it is time-consuming since in general one has to use the singular value decomposition in each iteration. In this paper, we introduce a novel model to reformulate the existed model by making use of low-rank matrix factorization to surrogate the nuclear norm for the sparse and low-rank decomposition problem. In such case we apply the Penalty Function Method (PFM) and Augmented Lagrangian Multipliers Method (ALMM) to solve this new non-convex optimization problem. Theoretically, corresponding to our methods, the convergence analysis is given respectively. Compared with classical RPCA, some practical numerical examples are simulated to show that our methods are much better than RPCA.     

低温微波技术在化学研究中的应用

低温微波技术可用于降低微波反应时体系的温度,减少或消除微波辐射时速热效应带来的副反应,具有快速高效、反应均匀、安全环保等优势,在化学研究中得到了广泛关注和应用。本文介绍了低温微波技术的实现方法,综述了近年来该技术在蛋白质研究、合成反应、天然产物研究和微波化学机理研究等领域中的应用,并展望了低温微波技术的发展方向。     

农药化学中的绿色化学

绿色化学是从根本上消除环境污染的必由之路。由于某些传统农药是引起环境污染的一个重要因素,因而对农药化学中的绿色化学进行研究和推广具有非常重要的意义。本文应用绿色化学原理,对农药化学中的一些绿色化学方法和技术作了简单介绍。     

Carboxylated graphene oxide/polyvinyl chloride as solid-phase extraction sorbent combined with ion chromatography for the determination of sulfonamides in cosmetics

A carboxylated graphene oxide/polyvinyl chloride (CGO/PVC) material was prepared as a sorbent for the selective extraction of sulphonamides from complex sample. After being dispersed in buffer solution, sample was transferred into the prefabricated solid-phase extraction (SPE) column, which integrated extraction and cleanup into one single-step. A multi-response optimization based on the Box-Behnken design was used to optimize factors affecting extraction efficiency. Compared with the commonly commercial sorbents including MCX, WCX and C₁₈, CGO/PVC hybrid material had higher extraction selectivity and capacity to sulphonamides. The limits of detection and quantification for seven target compounds were in the range of 3.4–7.1 μg/L and 11.4–23.7 μg/L, respectively. The self-assembly SPE cartridge was successfully used to enrich seven analytes in anti-acne cosmetics prior to ion chromatography detection with good recoveries of 87.8–102.0% and relative standard deviations of 1.2–6.4%, implying that this method was suitable for routine analysis of cosmetics.     

咪唑并吡啶类化合物的合成及其应用

咪唑并吡啶类化合物具有与吲哚、氮杂吲哚等类似的特殊结构和良好的生物活性,在医药和农药工业有着广泛的应用,成为有机化学家和药物化学家的研究热点。咪唑并吡啶类化合物主要有咪唑并[4,5-b]吡啶、咪唑并[4,5-c]吡啶、咪唑并[1,2-a]吡啶和咪唑并[1,5-a]吡啶等4个类型。本文阐述了近年来咪唑并吡啶类化合物的合成研究进展和应用情况,主要介绍了咪唑并[4,5-b]吡啶和咪唑并[4,5-c]吡啶这两类化合物的合成方法和在医药及农药领域的应用。     

新型2-胺基-1,3,4-噻二唑类化合物的合成及其抗肿瘤活性的研究

设计合成了一系列新型的N1-(5-取代基-1,3,4-噻二唑-2-基)-N3-取代苯基-脲类化合物,并测定了它们的抗肿瘤活性.标题化合物对肿瘤转移的生物活性实验是以荷Lewis肺癌小鼠为模型的.生物活性表明部分标题化合物对肿瘤的转移和肿瘤生长具有较好的抑制作用.其结构经元素分析、红外光谱及1H NMR确证.     

聚酰胺-胺-2-吡啶甲醛席夫碱树枝状大分子钯配合物的制备、表征及催化性能

制备了聚酰胺-胺(PAMAM)-2-吡啶甲醛(Py)席夫碱树枝状大分子及其钯配合物。通过红外、核磁共振、元素分析、等离子耦合原子发散光谱及热重-差热等分析手段对其进行了结构确证。研究了PAMAM-2-吡啶甲醛席夫碱钯配合物在Heck反应中的催化性能。以三乙胺(Et₃N)作为缚酸剂,碘代苯(PhI):10 mmol,n(PhI):n(AA):n(Et₃N)为1:1.4:2.5,n(Pd)=6.1×10^-3 mmol(5.0G PAMAMPy-Pd),在5 mL DMF中,100 ℃和N₂气保护下反应25 min,产率90.1%。催化剂经过简单的过滤可回收,重复使用3次产率仍可达82.0%。     

A Discussion of the Effect of Tortuosity on the Capillary Imbibition in Porous Media

In the past decades, there was considerable controversy over the Lucas–Washburn (LW) equation widely applied in capillary imbibition kinetics. Many experimental results showed that the time exponent of the LW equation is less than 0.5. Based on the tortuous capillary model and fractal geometry, the effect of tortuosity on the capillary imbibition in wetting porous media is discussed in this article. The average height growth of wetting liquid in porous media driven by capillary force following the [`(L)] _s(t) ~ t^1/2D_T{\overline L _{\rm {s}}(t)\sim t^{1/{2D_{\rm {T}}}}} law is obtained (here D _T is the fractal dimension for tortuosity, which represents the heterogeneity of flow in porous media). The LW law turns out to be the special case when the straight capillary tube (D _T = 1) is assumed. The predictions by the present model for the time exponent for capillary imbibition in porous media are compared with available experimental data, and the present model can reproduce approximately the global trend of variation of the time exponent with porosity changing.     

Optimal Biopsy Protocols for Prostate Cancer

Prostate cancer is the second leading cause of cancer-related death among American men. Biopsy for prostate cancer is a procedure known as transrectal ultrasound-guided needle biopsy. Because of the low resolution of ultrasound, the urologist cannot usually distinguish between cancerous and healthy tissue. For this reason, most biopsies follow standard protocols based on long-term experience of physicians. Recent studies indicate that these protocols have a significant rate of false negative diagnoses. In this research we use real prostate specimens removed by prostatectomy to develop a 3-D distribution map of cancer in the prostate, and use this to develop optimized biopsy procedures. The new procedures have detection rates that are significantly higher than those of current procedures, and thus have the potential to increase the rate of early detection of prostate cancer.