EPR Studies of the Binding Properties,Guest Dynamics,and Inner‐Space Dimensions of a Water‐Soluble Resorcinarene Capsule

Nitroxide free radicals have been used to study the inner space of one of Rebek’s water‐soluble capsules. EPR and ¹H NMR spectroscopy, ESI‐MS, and DFT calculations showed a preference for the formation of 1:2 complexes. EPR titrations allowed us to determine binding constants (K_a) in the order of 10⁷ M ^?2. EPR spectral‐shape analysis provided information on the guest rotational dynamics within the capsule. The interplay between optimum hydrogen bonding upon capsule formation and steric strain for guest accommodation highlights some degree of flexibility for guest inclusion, particularly at the center of the capsule where the hydrogen bond seam can be barely distorted or slightly disturbed.     

Predicting polycyclic aromatic hydrocarbon formation with an automatically generated mechanism for acetylene pyrolysis

Using Reaction Mechanism Generator (RMG), we have automatically constructed a detailed mechanism for acetylene pyrolysis, which predicts formation of polycyclic aromatic hydrocarbons (PAHs) up to pyrene. To improve the data available for formation pathways from naphthalene to pyrene, new high‐pressure limit reaction rate coefficients and species thermochemistry were calculated using a combination of electronic structure data from the literature and new quantum calculations. Pressure‐dependent kinetics for the CH potential energy surface calculated by Zádor et al. were incorporated to ensure accurate pathways for acetylene initiation reactions. After adding these new data into the RMG database, a pressure‐dependent mechanism was generated in a single RMG simulation which captures chemistry from C to C. In general, the RMG‐generated model accurately predicts major species profiles in comparison to plug‐flow reactor data from the literature. The primary shortcoming of the model is that formation of anthracene, phenanthrene, and pyrene are underpredicted, and PAHs beyond pyrene are not captured. Reaction path analysis was performed for the RMG model to identify key pathways. Notable conclusions include the importance of accounting for the acetone impurity in acetylene in accurately predicting formation of odd‐carbon species, the remarkably low contribution of acetylene dimerization to vinylacetylene or diacetylene, and the dominance of the hydrogen abstraction CH addition (HACA) mechanism in the formation pathways to all PAH species in the model. This work demonstrates the improved ability of RMG to model PAH formation, while highlighting the need for more kinetics data for elementary reaction pathways to larger PAHs.     

Implementation of a quality management system in meteorological practice in Serbia

An optional approach in the meteorological service Quality Management System (QMS) based on the case study of the Republic Hydrometeorological Service (MHS) of Serbia is presented and discussed in this paper. The idea is to use the ISO/IEC 17025 standard as a base for its QMS development. Main reasons for such a decision and the elements of the implemented solution are presented and discussed. Meteorological testing processes of the MHS of Serbia and relevant ISO/IEC 17025 scope of accreditation are presented. After establishing competencies in meteorological, environmental, and hydrological testing, the MHS of Serbia will develop an integrative ISO 9001 QMS. The Serbian case study could be taken into consideration as one of the options related to the future World Meteorological Organization Quality Management Framework.     

Measuring the performance of quality assurance processes: pharmaceutical industry deviation management case study

This article presents experience from the practice of a successful pharmaceutical company related to design and implementation of performance measures (PMs) for deviation management linked to the analysis of impact on the production cost for the selected product. Case study focuses on PMs within good manufacturing practice (GMP) processes related to quality assurance (QA) and quality management, with the aim of complying with its future requirements proposed by the European Commission. Critical areas were identified based on data gathered from the industrial deviation database. Implementation of the suggested corrective actions showed significant improvement in terms of reducing their number for more than 50% per selected deviation category. The results obtained in the course of this practice-oriented study contribute to further improvement of deviation management in the pharmaceutical industry and performance measurement of other GMP processes. The suggested performance measurement concept and problem-solving techniques may serve both practitioners and the decision-makers within QA and quality control (QC) in order to improve their processes by implementing relevant regulatory requirements for quality management and maintain compliance.     

Synthesis and spin-trapping behavior of 5-ChEPMPO, a cholesteryl ester analogue of the spin trap DEPMPO

[structure: see text] 5-(Cholesteryloxyethoxyphosphoryl)-5-methylpyrroline N-oxide (5-ChEPMPO), a DEPMPO analogue bearing a cholesterol group on the phosphorus atom, has been prepared and used to trap peroxyl-, alkoxyl-, thiyl-, and carbon-centered radicals in organic solvent. The important steric hindrance in 5-ChEPMPO does not affect the properties of 5-ChEPMPO in comparison to DEPMPO for the spin trapping of an enantiopure linoleic acid hydroperoxide. The 5-ChEPMPO-OOL spin adduct was observed by ESR and confirmed by ESI-MS/MS experiments. The relaxation terms of the 5-ChEPMPO-lipid peroxyl spin adduct were compared with those of other peroxyl spin adducts, and it was shown that the cholesteryl group has only a weak influence on the exchange rate between adduct conformers.     

Using fuzzy cognitive mapping techniques to model situation awareness for army infantry platoon leaders

This paper describes work on the development of an actionable model of situation awareness for Army infantry platoon leaders using fuzzy cognitive mapping techniques. Developing this model based on the formal representation of the platoon leader provided by the Goal-Directed Task Analysis (GDTA) methodology advances current cognitive models because it provides valuable insight on how to effectively support human cognition within the decision-making process. We describe the modeling design approach and discuss validating the model using the VBS2 simulation environment.     

Protein structure and dynamics in ionic liquids. Insights from molecular dynamics simulation studies

We present in this work the first molecular simulation study of an enzyme, the serine protease cutinase from Fusarium solani pisi, in two ionic liquids (ILs): 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) and 1-butyl-3-methylimidazolium nitrate ([BMIM][NO(3)]). We tested different water contents in these ILs at room temperature (298 K) and high temperature (343 K), and we observe that the enzyme structure is highly dependent on the amount of water present in the IL media. We show that the enzyme is preferentially stabilized in [BMIM][PF6] at 5-10% (w/w) (weight of water over protein) water content at room temperature. [BMIM][PF6] renders a more nativelike enzyme structure at the same water content of 5-10% (w/w) as previously found for hexane, and the system displays a similar bell-shape-like dependence with the water content in the IL media. [BMIM][PF6] is shown to increase significantly the protein thermostability at high temperatures, especially at low hydration. Our analysis indicates that the enzyme is less stabilized in [BMIM][NO(3)] relative to [BMIM][PF6] at both temperatures, most likely due to the strong affinity of the [NO(3)]- anion toward the protein main chain. These findings are in accordance with the experimental knowledge for these two ionic liquids. We also show that these ILs "strip off" most of the water from the enzyme surface in a degree similar to that found for polar organic solvents such as acetonitrile, and that the remaining waters at the enzyme surface are organized in many small clusters.     

Effect of Water Hardness on Catechin and Caffeine Content in Green Tea Infusions

The health benefits of green tea are associated with its high catechin content. In scientific studies, green tea is often prepared with deionized water. However, casual consumers will simply use their local tap water, which differs in alkalinity and mineral content depending on the region. To assess the effect of water hardness on catechin and caffeine content, green tea infusions were prepared with synthetic freshwater in five different hardness levels, a sodium bicarbonate solution, a mineral salt solution, and deionized water. HPLC analysis was performed with a superficially porous pentafluorophenyl column. As water hardness increased, total catechin yield decreased. This was mostly due to the autoxidation of epigallocatechin (EGC) and epigallocatechin gallate (EGCG). Epicatechin (EC), epicatechin gallate (ECG), and caffeine showed greater chemical stability. Autoxidation was promoted by alkaline conditions and resulted in the browning of the green tea infusions. High levels of alkaline sodium bicarbonate found in hard water can render some tap waters unsuitable for green tea preparation.     

Theoretical study on the HACA chemistry of naphthalenyl radicals and acetylene: The formation of C12H8, C14H8, and C14H10 species

The hydrogen-abstraction-C₂H₂-addition (HACA) chemistry of naphthalenyl radicals has been studied extensively, but there is a significant discrepancy in product distributions reported or predicted in literature regarding appearance of C₁₄H₈ and C₁₄H₁₀ species. Starting from ab initio calculations, a comprehensive theoretical model describing the HACA chemistry of both 1- and 2-naphthalenyl radicals is generated. Pressure-dependent kinetics are considered in the C₁₂H₉, C₁₄H₉, and C₁₄H₁₁ potential energy surfaces including formally direct well-skipping pathways. On the C₁₂H₉ PES, reaction pathways were found connecting two entry points: 1-naphthalenyl (1-C₁₀H₇) + acetylene (C₂H₂) and 2-C₁₀H₇ + C₂H₂. A significant amount of acenaphthylene is predicted to be formed from 2-C₁₀H₇ + C₂H₂, and the appearance of C₁₄H₈ isomers is predicted in the model simulation, consistent with high-temperature experimental results from Parker et al. At 1500 K, 1-C₁₀H₇ + C₂H₂ mostly generates acenaphthylene through a formally direct pathway, which predicted selectivity of 66% at 30 Torr and 56% at 300 Torr. The reaction of 2-C₁₀H₇ with C₂H₂ at 1500 K yields 2-ethynylnaphthalene as the most dominant product, followed by acenaphthylene mainly generated via isomerization of 2-C₁₀H₇ to 1-C₁₀H₇. Both the 1-C₁₀H₇ and 2-C₁₀H₇ reactions with C₂H₂ form some C₁₄H₈ products, but negligible phenanthrene and anthracene formation is predicted at 1500 K. A rate-of-production analysis reveals that C₁₄H₈ formation is strongly affected by the rates of H-abstraction from acenaphthylene, 1-ethynylnaphthalene, and 2-ethynylnaphthalene, so the kinetics of these reactions are accurately calculated at the high level G3(MP2,CC)//B3LYP/6-311G^** level of theory. At intermediate temperatures like 800 K, acenaphthylene + H are the leading bimolecular products of 1-C₁₀H₇ + C₂H₂, and 1-acenaphthenyl radical is the most abundant C₁₂H₉ isomer due to its stability. The predicted product distribution of 2-C₁₀H₇ + C₂H₂ at 800 K, in contrast to the results of Parker et al is predicted to consist primarily of species containing three fused benzene rings—for example, phenanthrene and anthracene—as the leading products, indicating HACA chemistry is valid from two to three ring polycyclic aromatic hydrocarbons under some conditions. Further experiments are needed for validation.