Noria: A Highly Xe‐Selective Nanoporous Organic Solid

Separation of xenon and krypton is of industrial and environmental concern; the existing technologies use cryogenic distillation. Thus, a cost‐effective, alternative technology for the separation of Xe and Kr and their capture from air is of significant importance. Herein, we report the selective Xe uptake in a crystalline porous organic oligomeric molecule, noria, and its structural analogue, PgC‐noria, under ambient conditions. The selectivity of noria towards Xe arises from its tailored pore size and small cavities, which allows a directed non‐bonding interaction of Xe atoms with a large number of carbon atoms of the noria molecular wheel in a confined space.     

Spontaneous Reconstitution of Functional Transmembrane Proteins During Bioorthogonal Phospholipid Membrane Synthesis

Transmembrane proteins are critical for signaling, transport, and metabolism, yet their reconstitution in synthetic membranes is often challenging. Non‐enzymatic and chemoselective methods to generate phospholipid membranes in situ would be powerful tools for the incorporation of membrane proteins. Herein, the spontaneous reconstitution of functional integral membrane proteins during the de novo synthesis of biomimetic phospholipid bilayers is described. The approach takes advantage of bioorthogonal coupling reactions to generate proteoliposomes from micelle‐solubilized proteins. This method was successfully used to reconstitute three different transmembrane proteins into synthetic membranes. This is the first example of the use of non‐enzymatic chemical synthesis of phospholipids to prepare proteoliposomes.     

Profiling monoterpenol glycoconjugation in Vitis vinifera L. cv. Muscat of Alexandria using a novel putative compound database approach,high resolution mass spectrometry and collision induced dissociation fragmentation analysis

In this work we present a novel approach for the identification of plant metabolites using ultrahigh performance liquid chromatography coupled to accurate mass time-of-flight mass spectrometry. The workflow involves developing an in-house compound database consisting of exact masses of previously identified as well as putative compounds. The database is used to screen accurate mass spectrometry (MS) data to identify possible compound matches. Subsequent tandem MS data is acquired for possible matches and used for structural elucidation. The methodology is applied to profile monoterpene glycosides in Vitis vinifera cv. Muscat of Alexandria grape berries over three developmental stages. Monoterpenes are a subclass of terpenes, the largest class of plant secondary metabolites, and are found in two major forms in the plant, “bound” to one or more sugar moieties or “free” of said sugar moieties. In the free form, monoterpenes are noted for their fragrance and play important roles in plant defense and as attractants for pollinators. However, glycoconjugation renders these compounds odorless, and it is this form that the plant uses for monoterpene storage. In order to gain insight into monoterpene biochemistry and their fate in the plant an analysis of intact glycosides is essential. Eighteen monoterpene glycosides were identified including a monoterpene trisaccharide glycoside, which is tentatively identified here for this first time in any plant. Additionally, while previous studies have identified monoterpene malonylated glucosides in other grapevine tissue, we tentatively identify them for the first time in grape berries. This analytical approach can be readily applied to other plants and the workflow approach can also be used for other classes of compounds. This approach, in general, provides researchers with data to support the identification of putative compounds, which is especially useful when no standard is available.     

Absorbing Interface Conditions for the Simulation of Wave Propagation on Non-Uniform Meshes

We proposed absorbing interface conditions for the simulation of linear wave propagation on non-uniform meshes. Based on the superposition principle of second-order linear wave equations, we decompose the interface condition problem into two subproblems around the interface: for the first one the conventional artificial absorbing boundary conditions is applied, while for the second one, the local analytic solutions can be derived. The proposed interface conditions permit a two-way transmission of low-frequency waves across mesh interfaces which can be supported by both coarse and fine meshes, and perform a one-way absorption of high-frequency waves which can only be supported by fine meshes when they travel from fine mesh regions to coarse ones. Numerical examples are presented to illustrate the efficiency of the proposed absorbing interface conditions.     

In search of physical parameters influenced by flow patterns in a heterogeneous two-phase mixture in microchannels using concomitant measurements

Space transportation systems require high-performance thermal protection and fluid management for systems ranging from cryogenic fluid devices to primary structures, and for propulsion systems exposed to extremely high temperatures, and other space systems, e.g., integrated circuits and cooling/environment control devices for advanced space suits. Although considerable developmental effort is underway to bring promising technologies to a readiness level for practical use, new and innovative methods are still needed. One such method is the Advanced Micro Cooling Module (AMCM), essentially a compact two-phase heat exchanger constructed of microchannels and designed to rapidly remove large quantities of heat from critical systems by incorporating phase transition. This paper describes the results of experimental research in two-phase flow phenomena, encompassing both an experimental and an analytical approach to the incorporation of flow patterns for air–water mixtures flowing in microchannels. Specifically addressed are: (1) design and construction of a sensitive two-phase experimental system which measures both ac and dc components of in situ physical mixture parameters including spatial concentration, using concomitant methods; (2) data acquisition and analysis in the amplitude, time, and frequency domains; and (3) analysis of results including evaluation of in situ physical parameters, and assessment of their validity for application in flow pattern determination.     

Probabilistic modeling of forced ignition of alternative jet fuels

Fast and reliable high altitude re-ignition is a critical requirement for the development of alternative jet fuels (AJFs). To achieve stable combustion, a spark kernel needs to transit in a partially or fully extinguished flow to develop a flame front. Understanding the relight characteristics of the AJFs is complicated by the chaoticity of the turbulent flow and variations in the spark properties. The focus of this study is the prediction of such characteristics by high-fidelity simulations, with a specific focus on fuel composition effect on the ignition process. For this purpose, a previously developed computational framework is applied, which utilizes high-fidelity LES simulations, a hybrid tabulation approach for modeling forced ignition and detailed quantification of uncertainty resulting from initial and boundary conditions to predict ignition probability. The method is applied to two alternative fuels (named C1 and C5) and Jet-A fuel (named A2) under gaseous conditions. Results show that the mixing of kernel and fuel–air mixture is not affected by the ignition process, but chemistry effects strongly dominate ignition probability. In particular, C1 exhibits much lower ignition probability than the other two fuels, especially at lean operating conditions. More importantly, this behavior is contradictory to ignition delay experiments which predict longer delay times for C5 compared to C1. Comparisons with experiments show that the comprehensive modeling approach captures the ignition trends. Analysis of kernel trajectories in composition space shows that the variations are caused by the relative effects of kernel mixing, response to strain, and ignition properties of the fuel.     

Synthetic Studies on Selectin Ligands/Inhibitors: One-Pot Synthesis of the Mono- and Oligo-Sulfated 2-(Tetradecyl)Hexadecyl β-D-Galacto- and Lactopyranosides as the Sulfatide Mimetics 1

Abstract

The ¹³C NMR spectra of inulin oligomers in D₂O with degree of polymerization (DP) of 3 through 9, along with two other inulin oligomer mixtures of average DP = 17 and DP = 31 were recorded. Significant variations in the chemical shift of some fructofuranose carbon signals indicates that unlike glucans, simple helical structures are not the predominant conformation for inulin oligomers—at least up to DP = 9. Models of the DP = 5 oligomer show that it should prefer a single helical conformation which however, would not be accessible to longer DP oligomers due to severe steric interactions.     

Effect of Headgroups on Small‐Ion Permeability across Archaea‐Inspired Tetraether Lipid Membranes

This paper examines the effects of four different polar headgroups on small‐ion membrane permeability from liposomes comprised of Archaea‐inspired glycerolmonoalkyl glycerol tetraether (GMGT) lipids. We found that the membrane‐leakage rate across GMGT lipid membranes varied by a factor of ≤1.6 as a function of headgroup structure. However, the leakage rates of small ions across membranes comprised of commercial bilayer‐forming 1‐palmitoyl‐2‐oleoyl‐sn‐glycerol (PO) lipids varied by as much as 32‐fold within the same series of headgroups. These results demonstrate that membrane leakage from GMGT lipids is less influenced by headgroup structure, making it possible to tailor the structure of the polar headgroups on GMGT lipids while retaining predictable leakage properties of membranes comprised of these tethered lipids.