Mass spectrometry analysis of new chemical entities for pharmaceutical discovery

In this Section, we review the applications of mass spectrometry for the analysis and purification of new chemical entities (NCEs) for pharmaceutical discovery. Since the speed of synthesis of NCEs has dramatically increased over the last few years, new high throughput analytical techniques have been developed to keep pace with the synthetic developments. In this Section, we review both novel, as well as modifications of commonly used mass spectrometry techniques that have helped increase the speed of the analytical process. Part of the review is devoted to the purification of NCEs, which has undergone significant development in recent years, and the close integral association between characterization and purification to drive high throughput operations. At the end of the Section, we review potential future directions based on promising and exciting new developments.     

市场环境下电力系统安全可靠性措施的经济当量

在竞争的电力市场中，由于各发电公司、电网公司、供电公司分属不同的经济实体，从而导致在系统运行和规划设计中对系统安全可靠性因素的考虑与传统电力系统存在巨大的区别。该文针对市场环境下电力系统的安全可靠性问题，从电网运行、电网规划、辅助服务等几方面进行了探讨。文中指出：电力系统中的安全可靠性将融入经济性中，传统的安全可靠性指标将不再单独存在，而只是作为可能给相应公司带来经济利益的一种措施：安全可靠性措施的经济当量是指实施某一项安全性措施所能带来的经济利益与其实施成本之差，即安全性措施的实施效益；传统电力系统中的某一安全可靠性指标在市场环境下是否会得到执行、执行到何种程度将取决于其经济当量值，只有当其经济当量值大于零，该安全可靠性校验措施的执行才是可行的。在对各类安全性校验措施实施后所导致的后果分析的基础上，文中提出了电力系统运行和电力系统规划设计中安全可靠性措施经济当量的计算模型。经济当量的提出为市场环境下电力系统安全可靠性的经济化实现提供了新的思路。     

Distributed electric power systems of the future: Institutional and technological drivers for near-optimal performance

Viewing electric power distribution systems as complex engineering systems whose states and inputs are defined by both technical and non-technical components of the system could help us understand challenges and lead to possible innovative solutions. In this setup, regulatory incentives, pricing, demand, and technological innovation are all endogenous feed-forward and/or feedback signals to the existing physical network and shape its evolution in both the short and long terms. We suggest that it is, indeed, possible to design technical, economic, and regulatory feed-forward and feedback signals keeping in mind the desired performance of the system. A particularly unique challenge is to enhance and operate the existing systems by incorporating distributed technologies (distributed generation or DG, active demand response, controllable wires) whose added value comes from just-in-time and right-location adjustments to the changing conditions. One way of interpreting the value of technologies of this type is to understand that they provide flexible and efficient responses by the end-user (DG and demand), therefore reducing the need for capacity reserve at the system level. Technical implementations and regulatory rules are not in place today to support systematic penetration of these technologies into the existing distribution systems. In this paper we stress the critical role of future load serving entities (LSEs) as aggregators and catalysts of customer choice at the value as one possible way forward. The LSEs would, through systematic protocols between themselves and the wholesale markets, on one side, and the customers whom they serve, on the other side, effectively implement incentives to induce near-optimal distribution system performance over long time horizons by investing in near-optimal technologies. These incentives must capture and compare both cumulative effects of real time decisions and the effects of longer-term investment decisions on near-optimal industry architecture. A non-traditional cost–benefit analysis which draws on temporal and spatial economies of scope is critical for ensuring penetration of what might be viewed as a rather costly disruptive technology. To illustrate the relevance of such analysis on incentives design, we provide numerical examples showing the objectives of the price-responsive demand and the objectives of the evolving distribution (local wire) companies under several regulatory rules.     

基于关系自适应解码的实体关系联合抽取

基于编码器-解码器的实体关系联合抽取模型解决了流水线模型存在的误差传递问题,但是以往基于编码器-解码器的模型还是存在两点问题:一是在解码阶段同时生成实体和关系,而两者是不同的对象,使得同一语义空间的映射降低了抽取效果;二是没有考虑不同关系之间的交互信息.针对这两点问题,提出了关系自适应解码模型.所提模型将实体关系联合抽...     

Synthesis of tadpole-shaped copolyesters based on living macrocyclic poly(-caprolactone)

Synthesis of an asymmetric tadpole-shaped aliphatic copolyester consisting of a poly(entities/25b.gif" alt="var epsilon" title="var epsilon" border="0">-caprolactone) ring and two poly(l-lactide) tails was reported for the first time. First, a high molecular weight cyclic PCL macroinitiator (M_n = 31,000) was prepared by intramolecular photocross-linking of “living” chains. Polymerization of l-lactide was resumed by the tin dialkoxide containing macrocycles, thus making the targeted tadpole-shaped copolyester available. A preliminary investigation of the crystallization of these copolyesters was carried out by differential scanning calorimetry and polarized optical microscopy.     

Low temperature preparation of carbon-supported PdCo alloy electrocatalysts for methanol-tolerant oxygen reduction reaction

Carbon-supported Pdentities/sbnd" class="glyphImg">Co alloy electrocatalysts of different Pd/Co atomic ratios were simply prepared in an aqueous solution at room temperature with NH₄F as a complexing agent and H₃BO₃ as a buffer, followed by NaBH₄ reduction. As-prepared Pdentities/sbnd" class="glyphImg">Co bimetallic nanoparticles show a single-phase face-centered-cubic (fcc) disordered structure, and the mean particle size is found to decrease with increase in Co content. TEM images demonstrated that the as-prepared Pdentities/sbnd" class="glyphImg">Co alloy nanoparticles are well dispersed on the surface of the carbon support with a small particle size and a relatively narrow particle size distribution. For example, the average particle size of a Pd₂Co₁/C catalyst is ca. 3.0 nm, which is much smaller than that of the Pdentities/sbnd" class="glyphImg">Co/C bimetallic nanoparticles reported by others. An activity evaluation of the oxygen reduction reaction (ORR) on as-prepared Pdentities/sbnd" class="glyphImg">Co/C catalysts with a rotating disk electrode (RDE) technique indicated that the maximum ORR mass activity was observed for a Pd:Co atomic ratio of 4:1, but the highest specific activity was found on a Pd:Co atomic ratio of 2:1. Kinetic analysis reveals that the ORR on Pdentities/sbnd" class="glyphImg">Co/C catalysts follows a four-electron process leading to water. Moreover, the Pdentities/sbnd" class="glyphImg">Co/C catalyst exhibited much higher methanol tolerance during the ORR than the Pt/C catalyst, assessing that it may function as a methanol-tolerant cathode catalyst in a direct methanol fuel cell (DMFC).     

Carbon-induced corrosion of MSF condenser tubes in Arabian Gulf water

The present investigation was undertaken to shed light on the failure of some 90/10 Cuentities/sbnd" class="glyphImg">Ni condenser tubes in a MSF distiller. The tubes showed numerous tiny pits of unusual features. Particles of C were discovered inside the tubes and were suspected of initiating micro-galvanic cells leading to pitting. The study involved the measurement of open circuit potentials (OCP) of C and 90/10 and 70/30 Cuentities/sbnd" class="glyphImg">Ni electrodes in stagnant-, stirred-, natural- and synthetic seawaters at various temperatures. The way these changed with time till constant values were recorded was followed over long exposure times. The EMF of the C/Cuentities/sbnd" class="glyphImg">Ni galvanic cells varied between 400 and 450 mV. Contact between C and the copper alloys resulted in dissolution of copper, and the development of galvanic corrosion potentials and galvanic corrosion currents. These were discussed in the light of Evans corrosion diagrams. The study was extended to include the C/316 stainless steel system under similar conditions. The OCP behaviour of the steel electrode depended upon whether measurements were carried out in stagnant-, stirred-, natural- or synthetic seawaters. Galvanic coupling with C resulted in intensified pitting attack of steel in stagnant, artificial seawater. Similar measurements were conducted on the C/Ti couple. The anode reaction led to the thickening of TiO, Insignificant corrosion was recorded with the Ti/316 stainless steel system.     

The observation of nanometer-sized entities in sulphided Mo-based catalysts on various supports

The progressive sulphidation of molybdenum-based hydrotreating model catalysts is studied using HRTEM and XPS. The catalysts are sulphided quasi in situ and prepared for TEM measurements in a glovebox. Subsequently, a specially developed vacuum-transfer specimen holder is used for transfer to the TEM. Using this procedure, a previously unknown feature is observed in the catalysts. Apart from the well-known slab-like structure of bulk molybdenum disulphide, nanometer-sized spherical entities of molybdenum sulphide or oxysulphide are observed. For a series of model CoMo/silica catalysts, these spots predominantly occur after mild sulphidation procedures. At higher sulphidation temperatures, these spots exist next to the slabs of MoS₂-like material. Comparison with practical molybdenum-based hydrotreating catalysts shows that these, too, can contain spots next to or instead of slabs, depending on precursor preparation and sulphidation procedures.