高效阴离子交换色谱-铜/铂修饰电极安培法测定大观霉素

采用阴离子交换色谱分离,在CuSO4溶液中加入少量镧系化合物,经电沉积制备La3+-Cu/pt/CME工作电极,建立了直流安培电化学法(DC)直接检测硫酸大观霉素的方法。考察了流动相浓度、测定电位等参数对色谱分离和测定的影响。在固定相为CarboPac PA10阴离子交换柱、流动相为26mmol/L NaOH,流速为0.6mL/min的色谱条件下,检测电位为0.68V时,硫酸大观霉素峰面积与其浓度在0.12～12mg/L(r=0.9991)和12～280mg/L(r=0.9995)两个范围内呈线性。本方法不需要柱前和柱后衍生化,能同时测定硫酸大观霉素中的主要组分和杂质。修饰电极制作方法简单,催化稳定性好,可作为电化学传感器测定硫酸大观霉素中的各组分。     

Identification of in vivo nitrosylated phytochelatins in Arabidopsis thaliana cells by liquid chromatography-direct electrospray-linear ion trap-mass spectrometry

Reversed-phase liquid chromatography (RPLC) and electrospray (ESI)-linear ion trap (LIT) mass spectrometry was applied to the direct characterization of in vivo S-nitrosylated (SNO) phytochelatins (PCs) expressed in cadmium-stressed Arabidopsis thaliana cells. Cys-nitrosylation is under discussion as in vivo redox-based post-translational modification of proteins and peptides in plants in which the –NO group is involved as signal molecule in different biological functions. The gas-phase ion chemistry of in vivo and in vitro generated SNO-PC_s was compared with the aim of evaluating NO binding stability and improving MS knowledge about peptide nitrosation. Using RPLC separation and ESI-LIT-MS, mono-nitrosylated PCs were identified in in vivo cadmium treated A. thaliana cells without derivatization. The in vivo binding of the NO group to PC₂, PC₃ and PC₄ resulted to occur selectively on only one cystein residue. The fragmentation pathway energies of the in vitro GSNO-generated NO-PCs with respect to the in vivo NO-PCs were investigated, suggesting the presence of a different internal stability for these molecules. By carrying out MS² experiments on these quasi-symmetric peptides, the different stability degree of the NO group was demonstrated to be correlated with the PC chain length. In addition, the data obtained highlight a putative role of the adjacent Glu/Cys motif in the gas-phase stability of the NO-containing molecule.     

石墨炉原子吸收光谱法钼涂层直接进样测定葡萄酒中的铝

主要应用了石墨炉原子吸收光谱法塞曼扣除背景方式,在镀钼涂层的平台石墨管中直接进样测定葡萄酒中的铝含量.研究了石墨炉各主要工作条件对吸光度的影响,确定了该方法的最佳条件:0-100μg/L范围内呈线性关系;仪器的检出限为1.7μg/L;应用此方法测定了几种不同样品中铝含量,测定值的相对标准偏差(n=10)在2.28%-3...     

直接膨胀供液制冷系统性能可视化研究

对直接膨胀供液制冷系统的传热性能进行了理论分析,建立了相应的数学模型.在保温体内对-5℃、0℃、5℃、10℃、15℃、20℃的工况进行了实验.分别测得制冷系统的压力、风量、制冷量、及功耗等技术参数,得到在环境温度一定的情况下的传热系数和制冷量的变化关系.并对蒸发器内制冷剂流动状态进行观察.实验表明:直接膨胀供液制冷系统...     

风机盘管机组换热器的分析与改进

分析了影响风机盘管换热器传热性能的主要因素并提出相应的解决措施.采用理论分析与计算的方法,从提高传热效率出发对热交换器进行了改进.对于企业降低生产成本、提升产品性能和提高市场竞争力具有重要意义.     

Fabrication of fluorinated polyimide optical waveguides by micropen direct writing technology

A novel and cheap direct writing method based on the micropen has been developed to fabricate fluorinated polyimide stripe optical waveguides on Si/SiO₂ wafers. The overall design, starting material, micropen direct writing system and fabrication processes of the stripe optical waveguides are presented. The effects of the key direct writing parameters, such as the tip-to-substrate distance, extrusive gas pressure, writing speed and viscosity of the polyamic acid, on the dimension and morphology of the stripe optical waveguides are discussed in detail. After deposition by the micropen system and baking process, the fluorinated polyimide stripe optical waveguides with good morphology and surface quality can be fabricated using the optimal parameters. The propagation losses at the wavelength of 1.55 μm are in the range of 1.4-3.5 dB cm⁻¹ as characterized by different length combinations of the strip optical waveguides.     

Using phase-type models to cost stroke patient care across health,social and community services

Stroke disease places a heavy burden on society, incurring long periods of time in hospital and community care, and associated costs. Also stroke is a highly complex disease with diverse outcomes and multiple strategies for therapy and care. Previously a modeling framework has been developed which clusters patients into classes with respect to their length of stay (LOS) in hospital. Phase-type models were then used to describe patient flows for each cluster. Also multiple outcomes, such as discharge to normal residence, nursing home, or death can be permitted. We here add costs to this model and obtain the Moment Generating Function for the total cost of a system consisting of multiple transient phase-type classes with multiple absorbing states. This system represents different classes of patients in different hospital and community services states. Based on stroke patients’ data from the Belfast City Hospital, various scenarios are explored with a focus on comparing the cost of thrombolysis treatment under different regimes. The overall modeling framework characterizes the behavior of stroke patient populations, with a focus on integrated system-wide costing and planning, encompassing hospital and community services. Within this general framework we have developed models which take account of patient heterogeneity and multiple care options. Such complex strategies depend crucially on developing a deep engagement with the health care professionals and underpinning the models with detailed patient-specific data.     

Monotonicity and the Aumann–Shapley cost-sharing method in the discrete case

We give an axiomatization of the Aumann–Shapley cost-sharing method in the discrete case by means of monotonicity and no merging or splitting (Sprumont, 2005). Monotonicity has not yet been employed to characterize this method in such a case, by contrast with the case in which goods are perfectly divisible, for which Monderer and Neyman (1988) and Young (1985b) characterize the Aumann–Shapley price mechanism.     

A methodology based on profitability criteria for defining the partial defection of customers in non-contractual settings

The defection or churn of customers represents an important concern for any company and a central matter of interest in customer base analysis. An additional complication arises in non-contractual settings, where the characteristics that should be observed to saying that a customer has totally or partially defected are not clearly defined. As a matter of fact, different definitions of the churn situation could be used in this context. Focusing on non-contractual settings, in this paper we propose a methodology for evaluating the short-time economic effects that using a certain definition of churn would have on a company. With this aim, we have defined two efficiency measures for the economic results of a marketing campaign implemented against churn, and these measures have been computed using a set of definitions of partial defection. Our methodology finds that definition maximizing both efficiency measures and moreover, the monetary amount that the company should invest per customer in the campaign for achieving the optimal solution. This has been modelled as a multiobjective optimization problem that we solved using compromise programming. Numerical results using real data from a Spanish retailing company are presented and discussed in order to show the performance and validity of our proposal.