Mixed Conduction in an N-Type Organic Semiconductor in the Absence of Hydrophilic Side-Chains

Organic electrochemical transistors (OECTs) are the building blocks of biosensors, neuromorphic devices, and complementary circuits. One rule in the materials design for OECTs is the inclusion of a hydrophilic component in the chemical structure to enable ion transport in the film. Here, it is shown that the ladder-type, side-chain free polymer poly(benzimidazobenzophenanthroline) (BBL) performs significantly better in OECTs than the donor–acceptor type copolymer bearing hydrophilic ethylene glycol side chains (P-90). A combination of electrochemical techniques reveals that BBL exhibits a more efficient ion-to-electron coupling and higher OECT mobility than P-90. In situ atomic force microscopy scans evidence that BBL, which swells negligibly in electrolytes, undergoes a drastic and permanent change in morphology upon electrochemical doping. In contrast, P-90 substantially swells when immersed in electrolytes and shows moderate morphology changes induced by dopant ions. Ex situ grazing incidence wide-angle X-ray scattering suggests that the particular packing of BBL crystallites is minimally affected after doping, in contrast to P-90. BBL's ability to show exceptional mixed transport is due to the crystallites’ connectivity, which resists water uptake. This side chain-free route for the design of mixed conductors could bring the n-type OECT performance closer to the bar set by their p-type counterparts.     

A note on saltwater intrusion in coastal aquifers

Transport of contaminants in aquifers has received considerable attention over the past few years. In coastal aquifers, a dispersion zone between saline water and fresh water exists where the flow of water and transport of salt ions are coupled. The flow pattern of two miscible fluids of different unit weights is characterized by the cyclic flow at the shore boundary. The width of the dispersion zone may be considerable, with the sharp interface assumption leading to erroneous results. A finite element model was applied to two prepublished problems for purposes of obtaining a better understanding of the saline water intrusion phenomenon. The effect of lowering the piezometric head due to excessive pumping was investigated. Physical parameters were extracted from the studies conducted by Kawatani and Rouve and Stoessinger, and comparison with their results was made.

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Resumé Pendant les dernières quelques années, le transport des contaminants dans les aquifères a reçu une attention considerable. Aux aquifères de la côte, il existe des zones où l'eau salé et l'eau douce se dispersent quand le flux de l'eau et le transport des ions du sel s'unissent. Le patron de flux [flow pattern] des fluides miscibles qui ont des différents unités de poids est characterisé par le flux cyclique au bord de la côte la largeur de la region de dispersion est considerable, et les suppositions de 'interface tranchante [sharp interface] peut conduire a des faux résultats. Pour mieux comprendre le phénomène de l'instrusion de l'eau salé, le modèle des éléments limités [finite element] a été appliqué dans deux problèmes dejà publiés. L'effet de l'abaissement piezométrique à cause du pompage excessif a été étudiés. Les paramètres physique ont été extraits des cas dejà étudiés, conduits par Rouven-Stoessinger et Kawatani, et la comparaisons avec leurs résultats a été fait.

     

Comparative study: Correlating extraction efficiency of simple diacid chelates for Hg(II), Cd(II), and pb(II) ions with the number of (CH2) units connecting COO− groups

Four dicarboxylic chelates (MAL, SUC, ADP, and SUP) were employed to explore the effect of (CH₂) extension on extraction efficiency of the corresponding dicarboxylates for Hg(II), Cd(II), and pb(II) ions. Binding effectiveness (extraction efficiency) for the forementioned ions was determined by measuring the percent of extraction.

The efficiency of extraction was found to depend on number of (CH₂) units within the chelate. This result was deduced after correlating the extraction efficiency with the number of (CH₂) units in the diacid chelate. Parameters like charge density distribution and HOMO energy were found to support the proceeded conclusion.     

Impacts of the Mississippi River spillway opening on faecal coliform concentration in Lake Pontchartrain

This study focuses on explaining the role of the periodic opening of the Bonnet Carré Spillway on the faecal coliform levels in Lake Pontchartrain. Water quality data were collected by the Lake Pontchartrain Basin Foundation to analyse the faecal coliform bacteria levels, turbidity, salinity, temperature, and dissolved oxygen in the lake water. The results show that the faecal coliform concentrations were lower during the spillway opening than the preceding and subsequent months. Statistical analysis shows the dilution effect, characterized by an effective reduction in faecal coliform concentrations due to increase in water turbidity, coupled with decrease in water salinity and dissolved oxygen because of spillway opening. It is also indicated that the combine effect of more than one factor produces a significantly greater reduction in the faecal coliform than each factor acting independently. Periodic spikes in faecal coliform concentrations were observed at sampling points located near the outlets of streams and drainage canals with high settlement densities. A positive correlation (r = 0.78467) was found between the average faecal coliform counts and average monthly precipitations, highlighting the role of precipitation run‐offs. The results of this study indicate that the spillway opening contributed to a reduction in the faecal coliform concentration in the lake's surface water during the studied periods.     

Synthesis of 4,4′-aryldihydrazono-3-(3′-pyridyl)-2-pyrazolin-4,5-diones and 1-aryl-3-(3′-pyridyl)-4,4′-arylbisazo-5-aryliminopyrazoles and their application as disazo disperse dyes. Part II

3-(3′-Pyridyl)-2-pyrazoline-4,5-dione 4,4′(4,4′-biphenylenedihydrazone and p-phenylenedihydrazone) and its derivatives ( IIa-e, IIIa-e ) were obtained by the coupling reaction of tetrazotised benzidine and p-diamonobenzene with 3-(3′-pyridyl)-2-pyrazolin-5-ones ( Ia-e ). Similarly, bis-azo compounds containing pyrazole nucleous as, 1-aryl-3-(3′-pyridyl)-4,4′-arylbisazo-5-aryliminopyrazoles ( VIa-i and VIIa-i ) were prepared by the interaction of the corresponding chloro compound ( IV and V ) with aromatic amines. The compounds so obtained ( II, III, VI and VII ) are used as disazo disperse dyes for dyeing polyester fibres fast yellow-orange shades. Their fastness properties towards washing, rubbing, acid-alkaline perspiration and light were investigated.     

Slip-Form Application to Concrete Structures

Because of superior speed and productivity, slip forms were extensively utilized as a potential formwork candidate in constructing concrete structures for the past few decades. Typical projects that employ this formwork technique are: Core of high-rise buildings, silos, telecommunication towers, cooling towers, heavy concrete offshore platforms, etc. The research presented in this paper aims at studying slip-form application to cores and silos, assessing its productivity, and determining its appropriate speed as well as auxiliary resource combinations. Simulation models are developed in which the potential control units in a slip-form system are described for cores and silos. Data are collected from several case study projects. A set of charts has been developed to predict productivity considering different stoppages, core cross section area, slipping (jacking) rate, and concrete placing methods. These charts play an essential role in managing slip-form application to cores and silos. Results show that the developed simulation models predict the productivity of case study projects with 99.70 and 99.30% accuracy for cores and silos, respectively. The presented research is relevant to both researchers and practitioners. It provides practitioners with charts that assist in scheduling and managing the required resources for slip-form application. In addition, it provides researchers with simulation models and framework for implementing slip forms to core and silo construction.     

Optical constants of thermally evaporated Se–Sb–Te films using only their transmission spectra

Amorphous Se_82 ? xTe₁₈Sb_x thin films with different compositions (x = 0, 3, 6 and 9 at.%) were deposited onto glass substrates by thermal evaporation. The transmission spectra, T(λ), of the films at normal incidence were obtained in the spectral region from 400 to 2500 nm. Based on the use of the maxima and minima of the interference fringes, a straightforward analysis proposed by Swanepoel has been applied to derive the optical constants and the film thickness. The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple and DiDomenico model. Tauc relation for the allowed non-direct transition describes the optical transition in the studied films. With increasing antimony content the refractive index increases while the optical band gap decreases. The optical band gap decreases from 1.62 to 1.26 eV with increasing antimony content from 0 to 9 at.%. The chemical-bond approach has been applied successfully to interpret the decrease of the optical gap with increasing antimony content.     

Dehydration of 2-(2-Arylethyl)-2-hydroxy-4-oxopentanoic Acids and their hydrazones to form heterocycles

Dehydration of 2-(2-arylethyl)-2-hydroxy-4-oxopentanoic acids 1 with hydrochloric acid/acetic acid, affords 3-(2-arylethyl)-5-hydroxy-5-methyl-2(5H)-furanones 4 . Compounds of type 1 and 4 represent suitable precursors for the formation of pyridazin-3-ones 7 as they smoothly react with hydrazine. A new series of s-triazolo[4,3-b]pyridazin-3-ones 12 and tetrazolo[1,5-b]pyridazines 15 are obtained from the 3-chloropyridazines 11 upon treatment with semicarbazide and sodium azide, respectively. Reaction of 11 with phenyl- acetyl-hydrazine provides 3-benzyl-6-phenyl-8-(2-phenyl-ethyl)-s-triazolo[4,3-b]pyridazine 13 via dehydrative cyclization of the intermediate 14 which was clarified to exhibit tautomeric equilibria between enol–hydrazine form A and keto–hydrazine form B by means of ¹H and ¹³C NMR spectroscopy. Attempts to synthesize 3-alloxy-pyridazines 18 by reacting 11 with sodium alloxide afford N-allyl compounds 17 .     

Effect of micro-mixing on the yield of intermediates in triplet consecutive/competitive reactions

Micro-mixing calculations based upon a simplified non-deforming one-dimensional diffusion-reaction formulation are presented for the sequence of three reactions denoted by A + B → R + B → S + B → T. This triplet reaction under micro-mixing is posed as five simultaneous parabolic partial differential equations which have been solved using a general purpose NAG library algorithm. The primary product R has an improved yield under perfect mixing conditions. The ultimate product T is shown to be always favoured by the perfect segregation of micro-mixing. By contrast, the central intermediate S gives high yields under micro-mixing at low conversions, but perfect mixing is preferable at higher conversions. In addition, predictions show that yield improvements for S might be possible by an engineered stretching of fluid lamellae and by the combination of micro-mixing followed by perfect mixing, especially at intermediate levels of conversion. The calculations are relevant to multi-step halogenations and they help to explain how the anomolous appearance of a tri-halogenated species ahead of mono- and di-halogenated ones in a stirred vessel can be attributed to micro-mixing.