高速公路PPP项目股权结构、质量水平与VFM的关系研究

高速公路PPP项目属于具有经营收益的准经营性项目,政府制定有效的激励措施,可以鼓励项目公司发挥专业的建设和运营能力,提高项目质量和收益水平。本文以VFM作为政府绩效评价指标,通过构建完全信息静态博弈模型,研究了PPP项目股权结构、质量水平与VFM之间的关系,结果发现:虽然社会资本较多持有项目公司股份有助于提高VFM水平,但随着社会资本方股权比例的增加,项目质量水平在不断降低,所以政府应该将社会资本方的持股比例控制在一定范围内,在保证项目质量的同时达到VFM最大化,从而降低政府方风险,提高社会效益。在高速公路PPP项目中,政府应优化股权决策,激励项目公司改善项目质量和水平,为公私双方带来良好的绩效水平。     

Electrochemical sensors for environmental gas analysis

The application of electrochemical sensors for measurement of concentration of pollutant gases in air in the part-per-billion (10⁹) range is reviewed. Performance-limiting factors, particularly the effects of extremes and of relatively rapid changes in ambient temperature and humidity, are noted. Variations in composition of the electrolyte in the meniscus at the electrode–gas interface and instability of the solid–liquid–gas contact line, causing important variations in current due to background electrode reactions, are deduced and suggested as the reason for the performance limitations. Suggestions are made for mitigation through instrument design.     

Ensuring robustness in the quality of antibiotic susceptibility test discs for four novel antibiotics

Antibiotic susceptibility test (AST) discs are used as an in-vitro diagnostic tool to select the appropriate antibiotic to treat an infection. Generally, the concentration of the drug loaded on to the AST discs is measured by studying its activity against quality control organisms. This methodology has several limitations—it is time consuming, requires trained manpower, has a wider acceptance criteria of zone of inhibitions—causing ambiguity in judging smaller variations in drug concentration. To overcome these issues, we have developed and validated high-performance liquid chromatographic (HPLC) methods for the determination of strength of AST discs for in-house researched antibiotics, namely Levonadifloxacin/WCK 771, Nafithromycin/WCK 4873, Cefepime-Tazobactam/WCK 4282, and Cefepime-Zidebactam/WCK 5222. The drugs were extracted from the AST discs using an appropriate solvent. The developed methods are simple, accurate, precise, reproducible, rugged, and robust. They are efficient in terms of time, and can be easily conducted in a quality control laboratory during release as well as stability evaluation of AST disc. Application of HPLC methods for the determination of strength of AST discs ensures flawless quality and, consequently, a better selection of drugs to treat bacterial infections in clinics.     

Quantitative NMR (qNMR) for pharmaceutical analysis: The pioneering work of George Hanna at the US FDA

In the last two decades, quantitative NMR (qNMR) has become increasingly important for the analysis of pharmaceuticals, chemicals, and natural products including dietary supplements. For the purpose of quality control and chemical standardization of a large variety of pharmaceutical, chemical, and medicinal products, qNMR has proven to be a valuable orthogonal quantification method and a compelling alternative to chromatographic techniques. This work reviews a fundamental component of the early development of qNMR, reflected in the pioneering work of the late George M. Hanna during the years between 1984 and 2006 at the US Food and Drug Administration (FDA). Because Hanna performed the majority of his groundbreaking work on a 90‐MHz instrument, his legacy output connects with recent progress in low‐field benchtop NMR instrumentation. Hanna gradually established the utility of qNMR for the routine quality control analyses practiced in pharmaceutical and related operations well ahead of his peers. His work has the potential to inspire new developments in qNMR applied to small molecules of biomedical importance.     

Melting thermodynamics of oligonucleic acids conjugated with relatively solvophobic linear polymers: A coarse‐grained molecular simulation study

Oligonucleic acids (ONAs), such as DNA and RNA, are used in various biotechnology and nanotechnology applications due to their ability to form a double helix that is stable at low temperature and melts at high temperatures. The melting temperature (T_m) of ONA duplexes can be tuned by the ONA composition, sequence, length and concentration, solvent quality, and salt concentration and by conjugation to other macromolecules. In this article, we use coarse‐grained (CG) molecular simulations to study ONAs conjugated with linear homopolymers that are relatively more solvophobic than the ONA. We study charged and stiff 8‐mer ONAs (e.g., DNA) and neutral and flexible 8‐mer ONAs (e.g., peptide nucleic acids or PNA), and vary the composition (or G‐C content) and sequence of ONA, conjugated homopolymer lengths and solvent quality for the polymer. For neutral and flexible ONAs, as the solvent quality worsens for the polymer, the ONA melting temperature increases from that of unconjugated ONA. The melting curves broaden with polymer length and worsening solvent quality, especially for ONAs with higher G‐C content. For charged and stiff ONAs, as the solvent quality worsens, the ONA melting temperature decreases compared to unconjugated ONA while the width of the melting curve remains the same. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1196–1208     

QUANTIS: Data quality assessment tool by clustering analysis

Automatically generated kinetic networks are ideally validated against a large set of accurate, reproducible, and easy-to-model experimental data. However, although this might seem simple, it proves to be quite challenging. QUANTIS, a publicly available Python package, is specifically developed to evaluate both the precision and accuracy of experimental data and to ensure a uniform, quick processing, and storage strategy that enables automated comparison of developed kinetic models. The precision is investigated with two clustering techniques, PCA and t-SNE, whereas the accuracy is probed with checks for the conservation laws. First, the developed tool processes, evaluates, and stores experimental yield data automatically. All data belonging to a given experiment, both unprocessed and processed, are stored in the form of an HDF5 container. The demonstration of QUANTIS on three different pyrolysis cases showed that it can help in identifying and overcoming instabilities in experimental datasets, reduce mass and molar balance closure discrepancies, and, by evaluating the visualized correlation matrices, increase understanding in the underlying reaction pathways. Inclusion of all experimental data in the HDF5 file makes it possible to automate simulating the experiment with CHEMKIN. Because of the employed InChI string identifiers for molecules, it is possible to automate the comparison experiment/simulation. QUANTIS and the concepts demonstrated therein is a potentially useful tool for data quality assessment, kinetic model validation, and refinement.     

3种现场快速水质检测仪的性价对比

选择了市场上口碑好、占有率高的3款便携式水质现场应急检测设备,通过准确度、精密度、检测时长及价格等指标,以权重积分法对3款仪器进行了比选,结果表明德国MN公司的PF-12型便携式多参数分光光度计的综合性能最优.     

Comparison of the chromatographic fingerprint,multicomponent quantitation and antioxidant activity of Salvia miltiorrhiza Bge. between sweating and nonsweating

Salvia miltiorrhiza Bge. is a traditional Chinese medicine applied in the treatment of various diseases in clinical practice. In the course of its processing, S. miltiorrhiza Bge. is usually processed by sweating. This study employed 10‐component contents determination coupled with high‐performance liquid chromatography (HPLC) fingerprint and antioxidant activity to investigate the effect of sweating on S. miltiorrhiza Bge. so as to evaluate the quality of S. miltiorrhiza Bge. The HPLC method was performed using C₁₈ and 0.05% phosphoric acid aqueous solution–acetonitrile with a gradient elution system. It was validated for linearity, precision, repeatability, stability and recovery. Similarity analysis, principal components analysis and antioxidant activity assays were used to compare sweated S. miltiorrhiza Bge. (SSM) and nonsweated S. miltiorrhiza Bge. (NSSM). SSM and NSSM showed good similarities in HPLC fingerprint (>0.9), but principal components analysis could classify the HPLC fingerprint and 10‐component quantitation analysis. Meanwhile, the antioxidant activity of SSM was significantly higher than that of NSSM (p < 0.01). The results of this study indicated that sweating could alter the content of chemical constituents in S. miltiorrhiza Bge., and could also improve its antioxidant activity. In addition, the method not only affords a viable strategy for comparing SSM and NSSM and assessing the quality of S. miltiorrhiza Bge., but also provides a reference for other herbal medicine that suffers from sweating.     

Geographical discrimination of Glechomae Herba based on fifteen phenolic constituents determined by LC–MS/MS method combined with chemometric methods

Glechomae Herba (GH) is rich in bioactive phenolic constituents and is widely used for treatment of cholelithiasis, urolithiasis and dropsy. The simultaneous determination of phenolic constituents in GH from different geographical origins is significant for authentication and quality control purposes. In this study, we developed a strategy integrating targeted analysis and chemometric methods for quality evaluation and discrimination of GH from different geographical origins. Firstly, an accurate and reliable liquid chromatography–tandem mass spectrometry method was developed for simultaneous quantification of 15 phenolic constituents in GH from different geographical origins. The established method was well validated in terms of desirable specificity, linearity, precision and accuracy. Secondly, the quantitative data were subjected to principal component analysis and orthogonal partial least squares discriminant analysis. Thirdly, a heatmap visualization was employed for clarifying the distribution of 15 phenolic compounds in GH from different geographical origins. These results indicated that GH samples from Shandong province obviously differ from those from other provinces in the content of bioactive phenolic constituents. Collectively, the proposed platform might be a suitable tool for quality evaluation and discrimination of GH from different geographical origins, providing promising perspectives in tracking the formulation processes of traditional Chinese medicine products.