Lanthanide complexes as luminogenic probes to measure sulfide levels in industrial samples

A series of lanthanide-based, azide-appended complexes were investigated as hydrogen sulfide-sensitive probes. Europium complex 1 and Tb complex 3 both displayed a sulfide-dependent increase in luminescence, while Tb complex 2 displayed a decrease in luminescence upon exposure to NaHS. The utility of the complexes for monitoring sulfide levels in industrial oil and water samples was investigated. Complex 3 provided a sensitive measure of sulfide levels in petrochemical water samples (detection limit ∼ 250 nM), while complex 1 was capable of monitoring μM levels of sulfide in partially refined crude oil.     

Modulating the Binding of Polycyclic Aromatic Hydrocarbons Inside a Hexacationic Cage by Anion–π Interactions

We report the template‐directed synthesis of BlueCage⁶⁺, a macrobicyclic cyclophane composed of six pyridinium rings fused with two central triazines and bridged by three paraxylylene units. These moieties endow the cage with a remarkably electron‐poor cavity, which makes it a powerful receptor for polycyclic aromatic hydrocarbons (PAHs). Upon forming a 1:1 complex with pyrene in acetonitrile, however, BlueCage?6 PF₆ exhibits a lower association constant K_a than its progenitor ExCage?6 PF₆. A close inspection reveals that the six PF₆^? counterions of BlueCage⁶⁺ occupy the cavity in a fleeting manner as a consequence of anion–π interactions and, as a result, compete with the PAH guests. This conclusion is supported by a one order of magnitude increase in the K_a value for pyrene in BlueCage⁶⁺ when the PF₆^? counterions are replaced by much bulkier anions. The presence of anion–π interactions is supported by X‐ray crystallography, and confirms the presence of a PF₆^? counterion inside its cavity.     

One-pot synthesis of vinylisoxazolidines from simple hydroxylamines and conjugated carbonyls

Herein is reported the highly chemo- and regioselective synthesis of 3-vinyl-4-formyl and 3-vinyl-5-formylisoxazolidines from enals, hydroxylamines and dipolarophiles under thermal conditions. The reaction works in high yields for a large array of substituted enals and a variety of dipolarophiles. The reaction provides the respective isoxazolidines with high chemoselectivity, stereospecificity and diastereoselectivity without significant purification. The substitution pattern on the dipolarophile directs the regioselectivity of the reaction to provide either 3,4- or 3,5-substituted isoxazolidine isomers. This method provides access to a wide variety of highly substituted, stereochemically dense isoxazolidine scaffolds from the selective reaction of the three proposed components.     

On a core concept of Arhangel'ski?

Arhangel'ski? [A.V. Arhangel'ski?, Locally compact spaces of countable core and Alexandroff compactification, Topology Appl. 154 (2007) 625-634] has introduced a weakening of σ-compactness: having a countable core, for locally compact spaces, and asked when it is equivalent to σ-compactness. We settle several problems related to that paper.     

Dollar vs. percentage markup pricing schemes under a dominant retailer

We investigate two very common pricing schemes for a Stackelberg-dominant retailer: percentage-markup and dollar-markup. We show that when a dominant retailer switches from dollar to percentage markup, the channel’s “overall pie” and the retailer’s “pie-piece” are both enlarged. In contrast, the manufacturer will be forced to levy a lower wholesale price, thus receiving a smaller pie-piece despite the larger pie. The preceding statements hold regardless of whether the demand is deterministic or stochastic. However, the effects of switching to percentage markup on the retail price and sales volume will depend not only on whether the demand is stochastic, but also on the assumed demand-curve shape and on whether demand stochasticity is “additive” or “multiplicative”. Besides presenting a comprehensive set of answers on the comparative performance of dollar- and percentagemarkups, our results also highlight the often overlooked importance of choosing between: (i) dollar- and percentage-markup; and (ii) the formats of the assumed stochasticity and demand curves.     

Mixed-conducting properties of annealed polyacrylonitrile activated by n-doping of conjugated domains

Critical limiting factors in next generation electrode materials for rechargeable batteries include short lifetimes, poor reaction reversibility, and safety concerns. Many of these challenges are caused by detrimental interactions at the interfaces between electrode materials and the electrolyte. Thermally annealed polyacrylonitrile has recently shown empirical success in mitigating such detrimental interactions when used in conjunction with alloy anode materials, though the mechanisms by which it does so are not well understood. This is a common problem in the battery community: an additive or a coating improves certain battery characteristics, but without a deeper understanding of how or why, design rules to further motivate the design of new chemistries can''t be developed. Herein, we systematically investigate the effect of heating parameters on the properties of annealed polyacrylonitrile to identify the structural basis for such beneficial properties. We find that sufficiently long annealing times and control over temperature result in the formation of conjugated imine domains. When sufficiently large, the conjugated domains can be electrochemically reduced in a Li-ion half-cell battery, effectively n-doping the polymeric matrix and allowing it to become a mixed-conductor, with the ability to conduct both the Li-ions and electrons needed for reversible lithiation of an interdispersed alloy active material like antimony. Not only do those relationships inform design principles for annealed polyacrylonitrile containing electrodes, but they also identify new strategies in the development of mixed-conducting materials for use in next generation battery electrodes.

Thermal annealing of polyacrylonitrile results in the formation of conjugated imine domains. When of sufficient size, these conjugated domains can be electrochemically activated to exhibit both electronic and ionic conductivity.     

Design,Synthesis and Biological Activity of Benzimidazole and Aminophenol Based Factor Xa Inhibitors

The serine protease factor Xa (FXa) is a key enzyme in the blood coagulation cascade, acting at the convergent point of the extrinsic and intrinsic pathways. The serine protease factor Xa (FXa) is a key enzyme in the blood coagulation cascade, acting at the convergent point of the extrinsic and intrinsic pathways. In our search for Fxa inhibitors as novel anticoagulants we identified the active isomer of the published FXa inhibitor, 2,7-bis-(4-amidinobenzilidine)-cycloheptan-l-one (BABCH), as the (Z, Z) isomer (ZK-805412, FXa Ki=0.66 nM). This photochemically labile (Z, Z) isomer has served as a conformationally rigid template for the development of distinct classes of potent, selective and orally active FXa inhibitors. Template evolution, in vitro SAR studies as well as our efforts to optimize in vivo parameters will be discussed.     

Oxygen Sensors Based on a Quenching of Tris-(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) in Fluorinated Polymers

Luminescence quenching of Ru(II) complexes by oxygen has proved a powerful method of quantitative oxygen analysis. It has become clear that the polymer support for the sensor molecule plays a pivotal role in the sensor performance. The current work is devoted to understanding how the physical and photophysical properties of a sensor respond to changes in polymer composition. An oxygen quenching study was conducted on [Ru(Ph₂phen)₃]Cl₂(Ph₂phen=4,7-diphenyl-1,10-phenanthroline), in copolymer supports consisting of GP-163 (a polydimethylsiloxane (PDMS) with varying amounts of pendant acrylate groups) combined with a number of alkyl methacrylates with long chain alkyl or fluorinated alkyl esters. Increasing the chain length or the degree of fluorination on the hydrocarbon chains enhances performance. However, there is an optimal chain length for the fluorinated hydrocarbons for sensitivity, linearity, and physical properties. Too long a chain yields reduced quenching sensitivity and yields cloudy polymers. All systems showed some degree of heterogeneity as indicated by nonlinear Stern-Volmer quenching plots, but their intensity quenching data could be successfully fit with a two-site model.     

Shellability of Interval Orders

An finite interval order is a partially ordered set whose elements are in correspondence with a finite set of intervals in the line, with disjoint intervals being ordered by their relative position. We show that any such order is shellable in the sense that its (not necessarily pure) order complex is shellable.     

Using Culturally Responsive Stories in Mathematics: Responses From the Target Audience

This study examined how Black students responded to the utilization of culturally responsive stories in their mathematics class. All students in the two classes participated in mathematics lessons that began with an African American story (culturally responsive to this population), followed by mathematical discussion and concluded with solving problems that correlated to the story. The researcher observed and recorded responses by students during each part of these lessons with protocols. Students independently reflected weekly by answering five questions to share their perspective on the African American stories. The teacher reflected on each lesson as well, describing thoughts on how these students responded to the story in each lesson. This paper examines the analyzed data from the target audience: Black students. Results revealed that Black students responded to the use of African American stories with high self‐rated levels of engagement and enjoyment and that the stories helped them think about mathematics to varying degrees. Since students who are engaged and are thinking about mathematics are more likely to achieve mathematical understanding, the researcher concludes that this strategy should continue to be tested in diverse classrooms with an emphasis on student reflection to determine if the outcomes are transferable and generalizable.