High-Definition Differential Ion Mobility Spectrometry with Resolving Power up to 500

As the resolution of analytical methods improves, further progress tends to be increasingly limited by instrumental parameter instabilities that were previously inconsequential. This is now the case with differential ion mobility spectrometry (FAIMS), where fluctuations of the voltages and gas pressure have become critical. A new high-definition generator for FAIMS compensation voltage reported here provides a stable and accurate output than can be scanned with negligible steps. This reduces the spectral drift and peak width, thus improving the resolving power (R) and resolution. The gain for multiply-charged peptides that have narrowest peaks is up to ~40 %, and R ~400–500 is achievable using He/N₂ or H₂/N₂ gas mixtures.      

An Untargeted Metabolomics Approach for Correlating Pulse Crop Seed Coat Polyphenol Profiles with Antioxidant Capacity and Iron Chelation Ability

Pulse crop seed coats are a sustainable source of antioxidant polyphenols, but are typically treated as low-value products, partly because some polyphenols reduce iron bioavailability in humans. This study correlates antioxidant/iron chelation capabilities of diverse seed coat types from five major pulse crops (common bean, lentil, pea, chickpea and faba bean) with polyphenol composition using mass spectrometry. Untargeted metabolomics was used to identify key differences and a hierarchical analysis revealed that common beans had the most diverse polyphenol profiles among these pulse crops. The highest antioxidant capacities were found in seed coats of black bean and all tannin lentils, followed by maple pea, however, tannin lentils showed much lower iron chelation among these seed coats. Thus, tannin lentils are more desirable sources as natural antioxidants in food applications, whereas black bean and maple pea are more suitable sources for industrial applications. Regardless of pulse crop, proanthocyanidins were primary contributors to antioxidant capacity, and to a lesser extent, anthocyanins and flavan-3-ols, whereas glycosylated flavonols contributed minimally. Higher iron chelation was primarily attributed to proanthocyanidin composition, and also myricetin 3-O-glucoside in black bean. Seed coats having proanthocyanidins that are primarily prodelphinidins show higher iron chelation compared with those containing procyanidins and/or propelargonidins.     

High-order sliding-mode observation for linear systems with unknown inputs

A high-order sliding-mode observer is designed for linear systems with unknown inputs. The concepts of strong observability and strong detectability are studied and their relation with the relative degree of a plant is established. High-order sliding-mode-based observers for linear time-invariant systems with unknown inputs satisfying the condition of strong observability or strong detectability are developed.     

Effect of buffer general acid-base catalysis on the stereoselectivity of ester and thioester H/D exchange in D2O

As part of a comprehensive investigation on the stereochemistry of base-catalyzed 1,2-elimination and H/D exchange reactions of carbonyl compounds, we have found that the stereoselectivity of H/D exchange of 3-hydroxybutyryl N-acetylcysteamine (3) in D(2)O is strongly influenced by the presence of buffers. This buffer effect is also operative with a simple acyclic ester, ethyl 3-methoxybutanoate (7). Buffers whose general-acid components are cyclic tertiary ammonium ions are particularly effective in changing the stereoselectivity. (2)H NMR analysis showed that without buffer, H/D exchange of 3 produces 81-82% of the 2R*, 3R* diastereomer of 2-deuterio 3 (the anti product). In the presence of 0.33 M 3-quinuclidinone buffer, only 44% of the 2R*, 3R* diastereomer was formed. With ester 7, the stereoselectivity went from 93-94% in DO(-)/D(2)O to 60% in the presence of buffer. Phosphate buffer, as well as others, also showed substantial effects. The results are put into the context of what is known about the mechanism of H/D exchange of esters and thioesters, and the relevance of the buffer effect on the mechanism of the enoyl-CoA hydratase reaction is discussed. It is likely that hydrogen bonding in the enolate-buffer acid encounter complex is an important stereochemical determinant in producing a greater amount of the 2R*, 3S* diastereomer (the syn product). Studies that involve the protonation of enolate anions in D(2)O need to include the buffer general acid in any understanding of the stereoselectivity.     

Using Gas Modifiers to Significantly Improve Sensitivity and Selectivity in a Cylindrical FAIMS Device

Recent reports describing enhanced performance when using gas additives in a DMS device (planar electrodes) have indicated that comparable benefits are not attainable using FAIMS (cylindrical electrodes), owing to the non-homogeneous electric fields within the analyzer region. In this study, a FAIMS system (having cylindrical electrodes) was modified to allow for controlled delivery of gas additives. An experiment was carried out that illustrates the important distinction between gas modifiers present as unregulated contaminants and modifiers added in a controlled manner. The effect of contamination was simulated by adjusting the ESI needle position to promote incomplete desolvation, thereby permitting ESI solvent vapor into the FAIMS analyzer region, causing signal instability and irreproducible CV values. However, by actively controlling the delivery of the gas modifier, reproducible CV spectra were obtained. The effects of adding different gas modifiers were examined using 15 positive ions having mass-to-charge (m/z) values between 90 and 734. Significant improvements in peak capacity and increases in ion transmission were readily attained by adding acetonitrile vapor, even at trace levels (≤0.1%). Increases in signal intensity were greatest for the low m/z ions; for the six lowest molecular weight species, signal intensities increased by ～10- to over 100-fold compared with using nitrogen without gas additives, resulting in equivalent or better signal intensities compared with ESI without FAIMS. These results confirm that analytical benefits derived from the addition of gas modifiers reported with a uniform electric field (DMS) also are observed using a non-homogenous electric field (FAIMS) in the analyser region.

Exploring the Potential of Fulvalene Dimetals as Platforms for Molecular Solar Thermal Energy Storage: Computations,Syntheses, Structures,Kinetics, and Catalysis

A study of the scope and limitations of varying the ligand framework around the dinuclear core of FvRu₂ in its function as a molecular solar thermal energy storage framework is presented. It includes DFT calculations probing the effect of substituents, other metals, and CO exchange for other ligands on ΔH_storage. Experimentally, the system is shown to be robust in as much as it tolerates a number of variations, except for the identity of the metal and certain substitution patterns. Failures include 1,1′,3,3′‐tetra‐tert‐butyl ( 4 ), 1,2,2′,3′‐tetraphenyl ( 9 ), diiron ( 28 ), diosmium ( 24 ), mixed iron‐ruthenium ( 27 ), dimolybdenum ( 29 ), and ditungsten ( 30 ) derivatives. An extensive screen of potential catalysts for the thermal reversal identified AgNO₃–SiO₂ as a good candidate, although catalyst decomposition remains a challenge.     

The Use of Corporate Planning Models: Past,Present and Future

The use of corporate planning models is widespread and will continue to expand greatly in the future. The proliferation of these models has been due to the increasing availability of computer-macro and micro-and also to management's awareness of D.S.S. (decision support systems) and M.I.S. (management information systems), which quickly enhanced the applications and practicality of modelling for all types and sizes of business. This paper provides an overview of the concept, developments and the future of corporate planning models.     

Synthesis and X-ray crystal structures of new trirhenium nonachloride chalcogenide clusters

The acetone adduct of trirhenium nonachloride, Re₃Cl₉ (acet)₃, where acet=acetone, reacts in acetone solution at room temperature with tetrabutylammonium chalcogenides [N(C₄H₉)₄]₂E, where E=S, Se and Te, producing the tetrabutylammonium salts of the new cluster anions [Re₃ (μ₃-E) (μ₂-Cl)₃Cl₆]²−. In the crystallographically determined structures of these compounds, triangles of rhenium atoms are capped by single chalcogen atoms, giving anions of near C_3v symmetry. The compound where E=S is also formed in the reaction of Re₃Cl₉ with [N(C₄H₉)₄]₂ [MoS₄] by sulfide transfer.