Flavin-catalyzed aerobic oxidation of sulfides in aqueous media

An aerobic, organocatalytic, and aqueous method for the oxidation of sulfides is described. Synthetic flavin, 5-ethyl-3,7,8,10-tetramethylisoalloxazinium perchlorate, acts as an efficient catalyst for the oxidation of sulfides in water under an oxygen atmosphere (1 atm) with the assistance of ascorbic acid as a reductant. This is an inexpensive, convenient, and environmentally benign method for the selective oxidative transformation of sulfides into sulfoxides.     

Automated data interpretation based on the concept of "negative signature mass" for mass-mapping disulfide structures of cystinyl proteins

An efficient method for data processing and interpretation is needed to support and extend disulfide mass-mapping methodology based on partial reduction and cyanylation-induced cleavage to proteins containing more than four cystines. Here, the concept of "negative signature mass" is introduced as the novel feature of an algorithm designed to identify the disulfide structure of a cystinyl protein given an input of mass spectral data and an amino acid sequence. The "negative signature mass" process is different from the conventional approach in that it does not directly rule-in disulfide linkages, but rather eliminates linkages from a list of all possible theoretical linkages, with the goal of ruling out enough linkages so that only one disulfide structure can be constructed. The operating principles and the effectiveness of the algorithm are described in the context of analyzing ribonuclease A, a 124-residue protein containing eight cysteines in the form of four cystines (disulfides).     

Determination of the optimal accelerated burn-in time under Arrhenius–Lognormal distribution assumption

Burn-in has been widely used as an effective procedure for screening out failed electronic products during the early-failure period, before shipment to the customers. Environmental stress such as temperature is increasingly being used to effectively shorten the burn-in time, and this method is usually called an accelerated burn-in test. When different stress levels are chosen for the burn-in operation, the burn-in times must be determined. An Arrhenius–Lognormal distribution can describe the lognormal lifetime of electronic products under different temperature levels. In this paper, the Arrhenius–Lognormal distribution and its mean residual life function are applied to the accelerated burn-in cost model, and a genetic algorithm is used to solve for the optimal burn-in time. We choose a real TFT–LCD module as an example, and determine its optimal accelerated burn-in time. A sensitivity analysis of the TFT–LCD module case shows the effect of model parameters on optimal burn-in time.     

水杨酸分子印迹膜电化学传感器的制备

以水杨酸为模板分子,采用循环伏安法电聚合形成聚吡咯膜,以固定电位过氧化法去除印迹分子,制备了水杨酸分子印迹膜电极.本印迹电极能促进水杨酸电氧化过程,有效地避免结构类似物(如苯甲酸)对其测定的干扰.循环伏安法用于电化学检测,当富集时间为10 min,磷酸盐缓冲溶液的pH=6.86 时,在1.0×10-6～2.0×10-3 mol/L浓度范围内,水杨酸氧化峰电流与其浓度呈良好的线性关系,检出限为0.8 μmol/L, 用分子印迹膜电极对加标样品进行分析,回收率为94.6%～103.4%.     

脉冲射频等离子体聚合沉积乙烯基乙酸

通过脉冲射频等离子体聚合方法获得乙烯基乙酸沉积薄膜，并用红外光谱、x射线光电子能 谱、表面张力、微分扫描量热分析及扫描电子显微镜等测试方法研究聚合沉积薄膜的化学结 构、表面物理形貌与脉冲放电条件的关系. 实验结果表明，采用脉冲放电，在脉冲占空比较 低时，能够保留较多的完整的单体分子官能团. 如果脉冲占空比较高或是采用连续波放电时 ，聚合沉积薄膜的化学结构与单体相比有较大改变. 聚合沉积薄膜在放置一段时间后表面为 规整的高度交联的网络状结构. 放电形式不同，结构有所区别. 因此可以根据实际需要，选 择不同的 关键词： 等离子体聚合 脉冲射频放电 乙烯基乙酸     

The k-Client Problem

Virtually all previous research in online algorithms has focused on single-threaded systems where only a single sequence of requests compete for system resources. To model multithreaded online systems, we define and analyze the k-client problem, a dual of the well-studied k-server problem. In the basic k-client problem, there is a single server and k clients, each of which generates a sequence of requests for service in a metric space. The crux of the problem is deciding which client's request the single server should service rather than which server should be used to service the current request. We also consider variations where requests have nonzero processing times and where there are multiple servers as well as multiple clients.We evaluate the performance of algorithms using several cost functions including maximum completion time and average completion time. Two of the main results we derive are tight bounds on the performance of several commonly studied disk scheduling algorithms and lower bounds of on the competitive ratio of any online algorithm for the maximum completion time and average completion time cost functions when k is a power of 2. Most of our results are essentially identical for the maximum completion time and average completion time cost functions.     

A counterexample to the conjecture of Aksionov and Mel'nikov on non-3-colorable planar graphs

Aksinov and Mel'nikov conjectured that every edge-critical non-3-colorable planar graph with triangles at distance at least one has connectivity 2. By constructing 3-connected edge-critical non-3-colorable planar graphs in which the distance between triangles is 2 or more, this conjecture is refuted.