The covariant electromagnetic Casimir effect for real conducting cylindrical shells

Using covariant quantization of the electromagnetic field, the Casimir force per unit area experienced by a long conducting cylindrical shell, under both Dirichlet and Neumann boundary conditions, is calculated. The renormalization procedure is based on the plasma cut-off frequency for real conductors. The real case of a gold (silver) cylindrical shell is considered and the corresponding electromagnetic Casimir pressure is computed. It is discussed that the Dirichlet and Neumann problems should be considered separately without adding their corresponding results.     

Interactions between a dsDNA Oligonucleotide and Imidazolium Chloride Ionic Liquids: Effect of Alkyl Chain Length,Part I

Ionic liquids (ILs) have become nearly ubiquitous solvents and their interactions with biomolecules has been a focus of study. Here, we used the fluorescence emission of DAPI, a groove binding fluorophore, coupled with molecular dynamics (MD) simulations to report on interactions between imidazolium chloride ([Im_n,1]⁺) ionic liquids and a synthetic DNA oligonucleotide composed entirely of T/A bases (7(TA)) to elucidate the effects ILs on a model DNA duplex. Spectral shifts on the order of 500–1000 cm⁻¹, spectral broadening (~1000 cm⁻¹), and excitation and emission intensity ratio changes combine to give evidence of an increased DAPI environment heterogeneity on added IL. Fluorescence lifetimes for DAPI/IL solutions yielded two time constants 0.15 ns (~80% to 60% contribution) and 2.36–2.71 ns for IL up to 250 mM. With DNA, three time constants were required that varied with added IL (0.33–0.15 ns (1–58% contribution), ~1.7–1.0 ns (~5% contribution), and 3.8–3.6 ns (94–39% contribution)). MD radial distribution functions revealed that π-π stacking interactions between the imidazolium ring were dominant at lower IL concentration and that electrostatic and hydrophobic interactions become more prominent as IL concentration increased. Alkyl chain alignment with DNA and IL-IL interactions also varied with IL. Collectively, our data showed that, at low IL concentration, IL was primarily bound to the DNA minor groove and with increased IL concentration the phosphate regions and major groove binding sites were also important contributors to the complete set of IL-DNA duplex interactions.     

Surface Interaction of Ionic Liquids: Stabilization of Polyethylene Terephthalate-Degrading Enzymes in Solution

The effect of aqueous solutions of selected ionic liquids solutions on Ideonella sakaiensis PETase with bis(2-hydroxyethyl) terephthalate (BHET) substrate were studied by means of molecular dynamics simulations in order to identify the possible effect of ionic liquids on the structure and dynamics of enzymatic Polyethylene terephthalate (PET) hydrolysis. The use of specific ionic liquids can potentially enhance the enzymatic hydrolyses of PET where these ionic liquids are known to partially dissolve PET. The aqueous solution of cholinium phosphate were found to have the smallest effect of the structure of PETase, and its interaction with (BHET) as substrate was comparable to that with the pure water. Thus, the cholinium phosphate was identified as possible candidate as ionic liquid co-solvent to study the enzymatic hydrolyses of PET.     

Performance assessment of new perturbed hard-sphere equation of state for molten metals and ionic liquids: Application to pure and binary mixtures

This work addresses modeling the pressure–volume–temperature (PVT) properties of molten metals and ionic liquids (ILs) using a new perturbed hard-sphere equation of state (PHS EOS). Two temperature-dependent parameters appeared in the EOS, are correlated with two scaling constants σ and ε. Knowing these parameters, the proposed EOS is applied to these classes of liquids. The reliability of the proposed model is checked by comparing with 3177 experimental density data points. The average absolute deviations (AAD) of predicted densities of molten metals and ILs from literature data are found to be 1.35% and 0.56%, respectively. The extension of PHS EOS to binary metal alloys and IL + IL is also discussed. Generally, 609 data points for binary mixtures have been examined. The AAD of the predicted results are found to be 1.03%.     

Structural Snapshots of Cluster Growth from {U6} to {U38} During the Hydrolysis of UCl4

Herein we report the assembly of large uranium(IV) clusters with novel nuclearities and/or shapes from the controlled hydrolysis of UCl₄ in organic solution and in the presence of the benzoate ligands. {U₆}, {U₁₃}, {U₁₆}, {U₂₄}, {U₃₈} oxo and oxo/hydroxo clusters were isolated and crystallographically characterized. These structural snapshots indicate that larger clusters are slowly built from the condensation of octahedral {U₆} building blocks. The uranium/benzoate ligand ratio, the reaction temperature and the presence of base play an important role in determining the structure of the final assembly. Moreover, the isolation of different size cluster {U₆} (few hours), {U₁₆} (3 days), {U₂₄} (21 days) from the same solution in a chosen set of conditions shows that the assembly of uranium oxo clusters in hydrolytic conditions is time dependent.     

The mechanism of Fe induced bond stability of uranyl(v)

The stabilization of uranyl(v) (UO₂¹⁺) by Fe(ii) in natural systems remains an open question in uranium chemistry. Stabilization of U^VO₂¹⁺ by Fe(ii) against disproportionation was also demonstrated in molecular complexes. However, the relation between the Fe(ii) induced stability and the change of the bonding properties have not been elucidated up to date. We demonstrate that U(v) – oaxial bond covalency decreases upon binding to Fe(ii) inducing redirection of electron density from the U(v) – oaxial bond towards the U(v) – equatorial bonds thereby increasing bond covalency. Our results indicate that such increased covalent interaction of U(v) with the equatorial ligands resulting from iron binding lead to higher stability of uranyl(v). For the first time a combination of U M_4,5 high energy resolution X-ray absorption near edge structure (HR-XANES) and valence band resonant inelastic X-ray scattering (VB-RIXS) and ab initio multireference CASSCF and DFT based computations were applied to establish the electronic structure of iron-bound uranyl(v).

The role of Fe in the increased stability of uranyl(v) is clarified by using state of the art uranium metalorganic chemistry, advanced X-ray spectroscopic approaches and computations.     

Highly Substituted Δ3-1,2,3-Triazolines: Solid-State Emitters with Electrofluorochromic Behavior

Highly substituted Δ³-1,2,3-triazolines can be prepared by reaction of triarylvinyl Grignard reagents with functionalized organic azides. The heterocycles are fluorescent in the solid state, and—depending on the substituents—they can display aggregation-induced emission. Upon oxidation, the triazolines form stable radical cations with altered photophysical properties. Therefore, they represent rare examples of solid-state emitters with intrinsic electrofluorochromic behavior.     

A greedy algorithm for partition of unity collocation method in pricing American options

A greedy algorithm in combination with radial basis functions partition of unity collocation (GRBF‐PUC) scheme is used as a locally meshless method for American option pricing. The radial basis function partition of unity method (RBF‐PUM) is a localization technique. Because of having interpolation matrices with large condition numbers, global approximants and some local ones suffer from instability. To overcome this, a greedy algorithm is added to RBF‐PUM. The greedy algorithm furnishes a subset of best nodes among the points X. Such nodes are then used as points of trial in a locally supported RBF approximant for each partition. Using of greedy selected points leads to decreasing the condition number of interpolation matrices and reducing the burdensome in pricing American options.     

Generalized assignment problem: Truthful mechanism design without money

We propose truthful approximation mechanisms for strategic variants of the generalized assignment problem (GAP) in a payment-free environment. In GAP, a set of items has to be optimally assigned to a set of bins without exceeding the capacity of any singular bin. In our strategic variant, bins are held by strategic agents and each agent may hide its willingness to receive some items in order to obtain items of higher values. The model has applications in auctions with budgeted bidders.