Highly stereocontrolled and regiocontrolled syntheses of polyoxygenated [2.2.2]oxabicyclic synthons

Highly oxygenated cyclohexanes (known as cyclitols or carba-sugars) were synthesized regiospecifically and stereoselectively via a key inverse electron demand Diels–Alder cycloaddition of electron poor 2-pyrones with electron rich tert-butyldimethylsilyl vinyl ether. The resulting [2.2.2]oxabicyclic lactones proved to be versatile synthons; syn-dihydroxylations were achieved with very high stereocontrol, with up to five stereocenters being produced from commercially available or easily prepared planar starting materials.     

Improvement of the analysis of the biochemical oxygen demand (BOD) of Mediterranean seawater by seeding control

Biochemical oxygen demand (BOD) is a useful parameter for assessing the biodegradability of dissolved organic matter in water. At the same time, this parameter is used to evaluate the efficiency with which certain processes remove biodegradable natural organic matter (NOM). However, the values of BOD in seawater are very low (around 2 mg O₂ L⁻¹) and the methods used for its analysis are poorly developed. The increasing attention given to seawater desalination in the Mediterranean environment, and related phenomena such as reverse osmosis membrane biofouling, have stimulated interest in seawater BOD close to the Spanish coast. In this study the BOD analysis protocol was refined by introduction of a new step in which a critical quantity of autochthonous microorganisms, measured as adenosine triphosphate, is added. For the samples analyzed, this improvement allowed us to obtain reliable and replicable BOD measurements, standardized with solutions of glucose-glutamic acid and acetate. After 7 days of analysis duration, more than 80% of ultimate BOD is achieved, which in the case of easily biodegradable compounds represents nearly a 60% of the theoretical oxygen demand. BOD₇ obtained from the Mediterranean Sea found to be 2.0 ± 0.3 mg O₂ L⁻¹ but this value decreased with seawater storage time due to the rapid consumption of labile compounds. No significant differences were found between two samples points located on the Spanish coast, since their organic matter content was similar. Finally, the determination of seawater BOD without the use of inoculum may lead to an underestimation of BOD.     

Ultrasound for microalgal cell disruption and product extraction: A review

Microalgae are a promising feedstock for the production of biofuels, nutraceuticals, pharmaceuticals and cosmetics, due to their superior capability of converting solar energy and CO₂ into lipids, proteins, and other valuable bioactive compounds. To facilitate the release of these important biomolecules from microalgae, effective cell disruption is usually necessary, where the use of ultrasound has gained tremendous interests as an alternative to traditional methods. This review not only summarizes the mechanisms of and operation parameters affecting cell disruption, but also takes an insight into measuring techniques, synergistic integration with other disruption methods, and challenges of ultrasonication for microalgal biorefining. Optimal conditions including ultrasonic frequency, intensity, and duration, and liquid viscosity and sonochemical reactor are the key factors for maximizing the disruption and extraction efficiency. A combination of ultrasound with other disruption methods such as ozonation, microwave, homogenization, enzymatic lysis, and solvents facilitates cell disruption and release of target compounds, thus provides powerful solutions to commercial scale-up of ultrasound extraction for microalgal biorefining. It is concluded that ultrasonication is a sustainable “green” process, but more research and work are needed to upscale this process without sacrificing performance or consuming more energy.     

基于两阶段解耦的可变功能机械模块划分研究

可变功能机械是一类多功能集成的机械产品, 较适合于采用模块化设计方法. 但是, 这类产品的每个功能都有相应的私有构件与之对应, 除此之外还有一定数量的共享构件, 造成各功能(相应地各客户需求)间存在不同程度的耦合性, 因此传统的单纯解决构件间耦合的模块划分方法存在困难. 为解决这一问题, 本文提出通过分阶段解耦的方法实现可变功能机械的模块划分, 其中第一阶段通过引入客户需求设计结构矩阵, 将与产品功能相关的客户需求先进行解耦, 以此解决单一解耦方式无法解决客户需求耦合的问题; 第二阶段通过引入需求结构关联矩阵与构件设计结构矩阵, 根据构件内部的关联关系进行结构解耦, 获得模块内部高耦合、模块之间低耦合的模块划分方案. 在此基础上, 通过引入模块化指数的评判标准, 解决产品模块聚合度和模块间耦合度相背离的问题, 实现了多种模块划分方案的选优. 最后通过一个多功能电钻案例来验证这一两阶段解耦模块划分方法的可行性.     

在寿命周期内具有抛物型需求的物品的最优补充模型

本文建立了在寿命周期内具有二次抛物需求的物品的一个确定型最优批量模型,提供了产生最优补充策略的一个简单的动态规划方法,用数字例子说明了该模型的求解过程,并出示了模型参数的灵敏度分析．     

Stochastic orders and their applications in financial optimization

Stochastic orders and inequalities are very useful tools in various areas of economics and finance. The purpose of this paper is to describe main results obtained so far by using the idea of stochastic orders in financial optimization. Especially, the emphasis is placed on the demand and shift effect problems in portfolio selection. Some other examples, which are not related directly to optimization problems, are also given to demonstrate the wide spectrum of application areas of stochastic orders in finance.     

Bayesian decision-making in inventory modelling

The objective of this paper is to advocate the use of Bayesianmethods in tackling decision problems with limited past data.It is assumed that a Bayesian approach is least likely to besuccessful when there is no information on which to base a meaningfulprior. Here we use a limiting, invariant, form of the conjugateprior distribution to represent this ignorance. The resultsof decisions based on Bayesian methods with this ‘non-informative’prior are compared with those which result from deriving a pointestimate for the unknown parameter. The particular context consideredhere is that of a single-period inventory model with compoundPoisson demand made up of a known demand size distribution butan unknown demand rate. The demand rate is assumed to be highenough for a normal approximation to the compound Poisson distributionto be used, in which case it is possible to analyse the behaviourdirectly. An extension to the multi-period model with zero leadtime is considered briefly. The results lend support to theuse of Bayesian methods, with or without a meaningful prior,for which the analysis and computation are no more complex thanthose required by standard methods.     

钻井污水处理的实验研究

钻井污水是油田开发中的主要环境污染物之一。其成分复杂,使得CODCr值高而处理难度大。以渤深6井为研究对象,采用混凝与微电解相结合处理废水。试验结果表明,原水的CODCr从35 155 mg/L降到186 mg/L,达到二级排放标准。     

Mussel-inspired chemistry in producing mechanically robust and bioactive hydrogels as skin dressings

The development of hydrogels as skin dressings demonstrates a great potential in real life applications. To achieve this, the hydrogel has to conquer its natural poor mechanical strength, and to prolong its lifetime, antifatigue and self-healing properties originating from dynamic interactions are also required. As skin dressings, the hydrogel needs to maintain its ductility while pursuing the above mentioned properties. In this work, poly(ethylene glycol) diacrylate is used to produce skin dressings by reinforcing poly(ethylene glycol) diacrylate/alginate double network hydrogels with a crosslinker from mussel-inspired chemistry, which is 3,4-dihydroxy-l-phenylalanine. This crosslinking methodology significantly improved mechanical strength of the hydrogel, with 11,200% increase in compressive failure strength; it endowed the hydrogel with outstanding antifatigue and training strengthening properties that makes its mechanical strength increasing in a 50 cycles compressive test; the hydrogel showed excellent self-healing properties that in rheological characterization; it also displayed enhanced storage modulus after withstanding a shear strain up to 1100%; meanwhile, the hydrogel exhibited extreme ductility with an elastic modulus of only 10.90–16.53 kPa. 3,4-dihydroxy-l-phenylalanine also renders the hydrogel its inherent antioxidant activity, conductivity, and bioadhesiveness. Together with the highly transparent appearance, the hydrogels possess a great potential and practibility in the fields of skin dressings.     

Toxic effects of imidacloprid and sulfoxaflor on Rana nigromaculata tadpoles: Growth,antioxidant indices and thyroid hormone-related endocrine system

Imidacloprid and sulfoxaflor have potential damage to nontarget aquatic organisms. However, limited information has been provided on their underlying toxicity effects on Rana nigromaculata tadpoles. Thus, the acute toxicity and chronic effects of imidacloprid and sulfoxaflor on R. nigromaculata tadpoles were studied. Acute toxicity indicted that 96 h for LC₅₀ values of  imidacloprid and sulfoxaflor were 173.55 and 427.37 mg/L, respectively. In this research, we explored antioxidant enzymes, some biological indexes, hormone levels and expression of relative tadpole genes involved in thyroid hormone-dependent metaplastic development after exposure for 28 days under 1/10 and 1/100 LC₅₀. Results showed an increase in the activity of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) in the tadpoles, and a low bioconcentration level with a bioconcentration factor (BCFs) < 1. The impact on the development of tadpoles was induced by the breakdown of hormonal levels engaged in metamorphosis. According to the real-time PCR results, imidacloprid and sulfoxaflor delayed amphibian metamorphosis by modifying mRNA expression, indicating that imidacloprid and sulfoxaflor may have an endocrine-disrupting effect on R. nigromaculata tadpoles. These findings were indicative of the toxicity of imidacloprid and sulfoxaflor to R. nigromaculata tadpoles.