Task-specific ionic liquid for solubilizing metal oxides

Protonated betaine bis(trifluoromethylsulfonyl)imide is an ionic liquid with the ability to dissolve large quantities of metal oxides. This metal-solubilizing power is selective. Soluble are oxides of the trivalent rare earths, uranium(VI) oxide, zinc(II) oxide, cadmium(II) oxide, mercury(II) oxide, nickel(II) oxide, copper(II) oxide, palladium(II) oxide, lead(II) oxide, manganese(II) oxide, and silver(I) oxide. Insoluble or very poorly soluble are iron(III), manganese(IV), and cobalt oxides, as well as aluminum oxide and silicon dioxide. The metals can be stripped from the ionic liquid by treatment of the ionic liquid with an acidic aqueous solution. After transfer of the metal ions to the aqueous phase, the ionic liquid can be recycled for reuse. Betainium bis(trifluoromethylsulfonyl)imide forms one phase with water at high temperatures, whereas phase separation occurs below 55.5 degrees C (temperature switch behavior). The mixtures of the ionic liquid with water also show a pH-dependent phase behavior: two phases occur at low pH, whereas one phase is present under neutral or alkaline conditions. The structures, the energetics, and the charge distribution of the betaine cation and the bis(trifluoromethylsulfonyl)imide anion, as well as the cation-anion pairs, were studied by density functional theory calculations.     

Electrochemical study of gelatin as a matrix for the immobilization of horse heart cytochrome c

The aim of this paper is to emphasize the strength of gelatin as a stable matrix for redox enzymes. Cyclic voltammetry has been applied for a detailed electrochemical study of horse heart cytochrome c (HHC) entrapped in a gelatin matrix immobilized on a gold electrode. The influence of the HHC concentration, the mass percentage of the gelatin and the nature of the gelatin on the electrochemical behaviour of HHC have been described in detail. In addition, attenuated total reflection infrared (ATR-IR) spectroscopy was used to prove the immobilization on a qualitative and conformational level. The thickness of the gelatin film was determined using a non-contact optical profiler. These results open up new perspectives in the development of stable, biocompatible matrices for redox enzymes. The latter has its relevance in the field of biosensor development.     

Analysis of Stop-and-Wait ARQ for a wireless channel

In this paper, we study the behavior of the transmitter buffer of a system working under a Stop-and-Wait retransmission protocol. The buffer at the transmitter side is modeled as a discrete-time infinite-capacity queue. The numbers of information packets entering the buffer during consecutive slots are assumed to be independent and identically distributed random variables. The packets are sent over an unreliable channel and transmission errors occur in a correlated manner. Specifically, the probability of an erroneous transmission is modulated by a two-state Markov chain. An expression is derived for the probability generating function of the buffer content. This expression is then used to derive several queue-length characteristics and the mean packet delay. Numerical examples illustrate the strong effect of error correlation on the system performance. The obtained analytical results are also compared with appropriate simulations.      

Cationic Geminoid Peptide Amphiphiles Inhibit DENV2 Protease,Furin, and Viral Replication

Dengue is an important arboviral infectious disease for which there is currently no specific cure. We report gemini-like (geminoid) alkylated amphiphilic peptides containing lysines in combination with glycines or alanines (C₁₅H₃₁C(O)-Lys-(Gly or Ala)_nLys-NHC₁₆H₃₃, shorthand notation C₁₆-KX_nK-C₁₆ with X = A or G, and n = 0–2). The representatives with 1 or 2 Ala inhibit dengue protease and human furin, two serine proteases involved in dengue virus infection that have peptides with cationic amino acids as their preferred substrates, with IC₅₀ values in the lower µM range. The geminoid C₁₆-KAK-C₁₆ combined inhibition of DENV2 protease (IC₅₀ 2.3 µM) with efficacy against replication of wildtype DENV2 in LLC-MK2 cells (EC₅₀ 4.1 µM) and an absence of toxicity. We conclude that the lysine-based geminoids have activity against dengue virus infection, which is based on their inhibition of the proteases involved in viral replication and are therefore promising leads to further developing antiviral therapeutics, not limited to dengue.     

Regular Turán numbers and some Gan–Loh–Sudakov-type problems

Motivated by a Gan–Loh–Sudakov-type problem, we introduce the regular Turán numbers, a natural variation on the classical Turán numbers where we restrict ourselves to the class of regular graphs. Among other results, we prove a striking supersaturation version of Mantel's theorem in the case of a regular host graph of odd order. We also characterize the graphs for which the regular Turán numbers behave classically or otherwise.     

The Playground Shade Index: A New Design Metric for Measuring Shade and Seasonal Ultraviolet Protection Characteristics of Parks and Playgrounds

Current shading strategies used to protect outdoor playgrounds from harmful solar radiation include the placement of artificial cloth weaves or permanent roofing over a playground site, planting trees in proximity to playground equipment, and using vegetation or surface texture variations to cool playground surfaces. How and where an artificial shade structure is placed or a tree is planted to maximize the shade protection over specific playground areas, requires careful assessment of local seasonal sun exposure patterns. The Playground Shade Index (PSI) is introduced here as a design metric to enable shade and solar ultraviolet exposure patterns to be derived in an outdoor space using conventional aerial views of suburban park maps. The implementation of the PSI is demonstrated by incorporating a machine learning design tool to classify the position of trees from an aerial image, thus enabling the mapping of seasonal shade and ultraviolet exposure patterns within an existing 7180 m² parkland. This is achieved by modeling the relative position of the sun with respect to nearby buildings, shade structures, and the identified evergreen and deciduous tree species surrounding an outdoor playground.