Bacterial transport in porous media: New aspects of the mathematical model

Transport of bacteria is an important aspect from scientific, industrial and environmental point of view. In this work, a one-dimensional mathematical model based on linear equilibrium adsorption of bacteria has been developed to predict bacterial transport through porous media. This model is more realistic than existing models because of its coupling both physicochemical and biological phenomena. Two important biological phenomena, the growth and decay of bacterial cells and chemotactic/chemotaxis of bacteria along with physicochemical properties have been adequately incorporated which are quite new aspects in our model. In agreement with experimental study by [D.K. Powelson, R.J. Simpson, C.P. Gerba, J. Environ. Qual. 19 (1990) 396], model simulations indicated that enhancement of breakthrough occurs due to increase in flow velocity, cell concentration, substrate concentration, respectively. It has also been found that chemo tactic has a significant effect on bacterial transport, especially under conditions of considerable substrate gradient and at low pore velocity. The importance of threshold concentration of captured cells (σ₀) on bacterial transport has also been identified which is also a new aspect in our model.     

Gravimetric determination of palladium with quinolinimide as a reagent

Summary Quinolinimide which is found to be a selective reagent for palladium forms a complex of the composition Pd(C₇H₃O₂N₂)₂. The reagent quantitatively precipitates palladium from solutions of p_H 0.5 to 2.5 in presence of common ions as well as platinium metals, except tin which, however, can be kept in solution by complexing with citric acid. The palladium complex being stable up to 307° C can be directly weighed.

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Zusammenfassung Chinolinimid wird als selektives Reagens für Palladium vorgeschlagen. Bei p_H-Werten zwischen 0,5 und 2,5 kann Palladium quantitativ in Form des Komplexes Pd(C₇H₃O₂N₂)₂ gefällt werden, wobei die meisten anderen Ionen, auch die der Platinmetalle, in Lösung bleiben. Zinn stört, kann aber mit Citronensäure maskiert werden. Der Palladiumkomplex ist bis 307° C stabil und kann direkt ausgewogen werden.

     

Turn on Fluorescence Sensing of Zn2+ Based on Fused Isoindole-Imidazole Scaffold

Optical chemosensors caused a revolution in the field of sensing due to their high specificity, sensitivity, and fast detection features. Imidazole derivatives have offered promising features in the literature as they bear suitable donor/acceptor groups for the selective analytes in the skeleton. In this work, an isoindole-imidazole containing a Schiff base chemosensor (1-{3-[(2-Diethylamino-ethylimino)-methyl]-2-hydroxy-5-methyl-phenyl}-2H-imidazo[5,1-a]isoindole-3,5-dione) was designed and synthesized. The complete sensing phenomena have been investigated by means of UV-Vis, fluorescence, lifetime measurement, FT-IR, NMR and ESI-MS spectroscopic techniques. The optical properties of the synthesized ligand were investigated in 3:7 HEPES buffer:DMSO medium and found to be highly selective and sensitive toward Zn²⁺ ion through a fluorescence turn-on response with detection limit of 0.073 μm. Furthermore, this response is effective in gel form also. The competition studies reveal that the response of the probe for Zn²⁺ ion is unaffected by other relevant metal ions. The stoichiometric binding study was performed utilizing Job’s method which indicated a 1:1 sensor–Zn²⁺ ensemble. Computational calculations were performed to pinpoint the mechanism of sensing.     

Crystal and molecular structure ofo-aminobenzoato (o-(p-dimethylaminobenzalidine)benzoato)(o-ammoniobenzoate)dimethyltin(IV), an example of a mixed carboxylate complex of tin

The structure of the title compound, [Me₂Sn(O₂CC₆H₄NH₂-o)(O₂CC₆H₄(N=C(H)C₆H₄NMe₂-p)-o)(^–O₂CC₆H₄NH₃-o)], has been determined at room temperature. The structure features a distorted trigonal bipyramidal coordination geometry for Sn, defined by three O atoms derived from chemically different, monodentate carboxylate ligands and two methyl groups. Crystals are monoclinic, space groupP2₁/n witha=14.718(5),b=10.981(4),c=20.321(3) Å, =110.74(2)°,Z=4; refinement on 2480 reflections gaveR=0.046.     

Synthesis,Structure, Bonding,and Reactivity of Metal Complexes Comprising Diborane(4) and Diborene(2): [{Cp*Mo(CO)2}2{μ‐η2:η2‐B2H4}] and [{Cp*M(CO)2}2B2H2M(CO)4], M=Mo,W

The reaction of [(Cp*Mo)₂(μ‐Cl)₂B₂H₆] ( 1 ) with CO at room temperature led to the formation of the highly fluxional species [{Cp*Mo(CO)₂}₂{μ‐η²:η²‐B₂H₄}] ( 2 ). Compound 2, to the best of our knowledge, is the first example of a bimetallic diborane(4) conforming to a singly bridged C_s structure. Theoretical studies show that 2 mimics the Cotton dimolybdenum–alkyne complex [{CpMo(CO)₂}₂C₂H₂]. In an attempt to replace two hydrogen atoms of diborane(4) in 2 with a 2e [W(CO)₄] fragment, [{Cp*Mo(CO)₂}₂ B₂H₂W(CO)₄] ( 3 ) was isolated upon treatment with [W(CO)₅?thf]. Compound 3 shows the intriguing presence of [B₂H₂] with a short B?B length of 1.624(4) Å. We isolated the tungsten analogues of 3 , [{Cp*W(CO)₂}₂B₂H₂W(CO)₄] ( 4 ) and [{Cp*W(CO)₂}₂B₂H₂Mo(CO)₄] ( 5 ), which provided direct proof of the existence of the tungsten analogue of 2 .     

Rare Tautomers of 1‐Methyluracil and 1‐Methylthymine: Tuning Relative Stabilities through Coordination to PtII Complexes

We have computationally explored how the relative stabilities of 1‐methyluracil (1‐MeUH) tautomers can be tuned through coordination of these tautomers to Pt^II complexes with a particular set of ligands. This has been done using density functional theory at the BP86/TZ2P level. Thus, we have examined the water/1‐MeUH exchange reactions of [Pt^II(A)(B)(C)(OH₂)]^q + 1‐MeUH to uncover: i) which tautomers are best stabilized by the Pt^II complex, and ii) how the net charge q in the complex affects the reaction energy. The net charge q depends on the ligands A, B, and C, which can be the neutral NH₃ or anionic Cl^?. To reveal the effect of solvation, all reaction systems are studied both in the gas phase and in water. Also the stabilization of tautomers of 1‐methylthymine (1‐MeTH) by cisplatin is investigated. The calculations reveal that relative energies of the metal (here: Pt^II)‐complexed forms of the various tautomers (here: of 1‐MeUH and 1‐MeTH) do not parallel those of the free tautomers. Rather, a rare nucleobase tautomer, despite its low natural abundance, may become favored over the predominant one when complexed to a metal ion.     

From Intramolecular (Circular) in an Isolated Molecule to Intermolecular Hole Delocalization in a Two‐Dimensional Solid‐State Assembly: The Case of Pillarene

To achieve long‐range charge transport/separation and, in turn, bolster the efficiency of modern photovoltaic devices, new molecular scaffolds are needed that can self‐assemble in two‐dimensional (2D) arrays while maintaining both intra‐ and intermolecular electronic coupling. In an isolated molecule of pillarene, a single hole delocalizes intramolecularly via hopping amongst the circularly arrayed hydroquinone ether rings. The crystallization of pillarene cation radical produces a 2D self‐assembly with three intermolecular dimeric (sandwich‐like) contacts. Surprisingly, each pillarene in the crystal lattice bears a fractional formal charge of +1.5. This unusual stoichiometry of oxidized pillarene in crystals arises from effective charge distribution within the 2D array via an interplay of intra‐ and intermolecular electronic couplings. This important finding is expected to help advance the rational design of efficient solid‐state materials for long‐range charge transfer.