Bis(2-hydroxyacetophenone)ethylenediimine as a neutral carrier in a coated-wire membrane electrode for lead(II).

A coated-wire ion-selective electrode (CWISE), based on a Schiff base as a neutral carrier, was successfully developed for the detection of Pb(II) in aqueous solution. CWISE exhibited a linear response with a Nernstian slope of 29.4 +/- 0.5 mV/decade within the concentration range of 1.0 x 10(-5) - 1.0 x 10(-1) M lead ion. CWISE has shown detection limits of 5.0 x 10(-6) M. The electrode exhibited good selectivity over a number of alkali, alkaline earth, transition and heavy metal ions. This sensor yielded a steady potential within 10 to 20 s at a linear dynamic range. The electrode was suitable for use in aqueous solutions in a pH range of 2.0 to 5.0. Applications of this electrode for the determination of lead in real samples and as indicator electrode for potentiometric titration of Pb2+ ion using K2CrO4 are reported.     

On the mass spectrum of noncommutative Schwinger model in Euclidean ℝ<Superscript>2</Superscript> space

The mass spectrum of noncommutative QED in two-dimensional Euclidean ?² space is derived first in a perturbative approach at one-loop level and then in a nonperturbative approach using the equivalent bosonized noncommutative effective action. It turns out that the mass spectrum of noncommutative QED in two dimensions reduces to a single non-interacting meson with mass \(M_{\gamma}=\frac{g}{\sqrt{\pi}}\), as in commutative Schwinger model.     

Magnesium-Free Immobilization of DNA Origami Nanostructures at Mica Surfaces for Atomic Force Microscopy

DNA origami nanostructures (DONs) are promising substrates for the single-molecule investigation of biomolecular reactions and dynamics by in situ atomic force microscopy (AFM). For this, they are typically immobilized on mica substrates by adding millimolar concentrations of Mg²⁺ ions to the sample solution, which enable the adsorption of the negatively charged DONs at the like-charged mica surface. These non-physiological Mg²⁺ concentrations, however, present a serious limitation in such experiments as they may interfere with the reactions and processes under investigation. Therefore, we here evaluate three approaches to efficiently immobilize DONs at mica surfaces under essentially Mg²⁺-free conditions. These approaches rely on the pre-adsorption of different multivalent cations, i.e., Ni²⁺, poly-l-lysine (PLL), and spermidine (Spdn). DON adsorption is studied in phosphate-buffered saline (PBS) and pure water. In general, Ni²⁺ shows the worst performance with heavily deformed DONs. For 2D DON triangles, adsorption at PLL- and in particular Spdn-modified mica may outperform even Mg²⁺-mediated adsorption in terms of surface coverage, depending on the employed solution. For 3D six-helix bundles, less pronounced differences between the individual strategies are observed. Our results provide some general guidance for the immobilization of DONs at mica surfaces under Mg²⁺-free conditions and may aid future in situ AFM studies.     

Thick junction broadband organic photodiodes

Inorganic semiconductor‐based broadband photodetectors are ubiquitous in imaging technologies such as digital cameras and photometers. Herein a broadband organic photodiode (OPD) that has performance metrics comparable or superior to inorganic photodiodes over the same spectral range is reported. The photodiode with an active layer comprised of a poly[N‐9′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)]:[6,6]‐phenyl‐C₇₁‐butyric acid methyl ester bulk heterojunction blend had a dark current < 1 nA/cm², specific detectivity of ∼10¹³ Jones, reverse bias −3 dB frequency response of 100 kHz to 1 MHz, and state‐of‐the‐art Linear Dynamic Range for organic photodiodes of nine orders of magnitude (180 dB). The key to these performance metrics was the use of a thick junction (700 nm), which flattened the spectral response, reduced the dark current and decreased performance variations. The strategy also provides a route to large area defect free “monolithic” structures for low noise integrated photo‐sensing, position determination, or contact, non‐focal imaging.     

Droplet formation in quickly stretched liquid filaments

Film splitting necessarily occurs in roll coating and unwanted droplets can occur at high machine speeds when the resulting filaments break up. To study this ‘misting’ problem, an apparatus was designed and built to simulate filament fluid mechanics. The device creates a filament by elongating a liquid bridge and stretches the filament at a high and constant rate of acceleration to mimic coating machine kinematics. Filament breakup was observed using a high-speed video camera and the images were analyzed to yield droplet size and number. With Newtonian fluids, a single droplet formed at Ohnesorge (Oh) numbers less than 0.1 and more and smaller droplets were produced at Oh numbers above 0.1. Associative polymer solutions, prepared as weakly elastic fluids to represent industrial coatings, produced even more and smaller droplets, but only for Ohnesorge numbers in the range of 0.01 to 0.1.     

Nuclear Quadrupole Resonance and Stereochemistry II. Vicinal cis- and trans-dichloro derivatives of carbocyclic systems

The ³⁵Cl quadrupole resonance frequencies of sets of isomeric vicinal dichloro derivatives of carbocyclic molecules are presented. In all cases except one – cis- and trans-1, 2-dichloro-acenaphthene – the configuration has only a small effect on the resonance frequency. This implies that the frequency-differences in cyclic α-chloroethers reported in Part I of this series [1] are indeed due to a specific interaction with the oxygen atom. The difference between the acenaphthenes may be due to hyperconjugation between the C? Cl bond and the aromatic system.     

C4−H alkoxylation of 6-bromoindole and its application to the synthesis of breitfussin B

Subjecting 6-bromoindole to an iridium-catalysed triborylation-diprotodeborylation sequence followed by Chan-Evans-Lam coupling gives 6-bromo-4-methoxyindole in good overall yield. This indole C4?H alkoxylation process was used in a formal synthesis of the natural product breitfussin B.     

Asymmetric motion of a transversely isotropic thermoelastic half-space under time-harmonic buried source

With the aid of complete representations in terms of two scalar potential functions, the governing equations of coupled thermoelasticity are uncoupled into a sixth- and second-order partial differential equations in cylindrical coordinate system, which are solved by virtue of Fourier series expansion and Hankel integral transforms. Utilizing the transformed stresses-, displacements- and temperature-potential functions relationships, these functions are derived and represented in terms of improper line integrals. The general solutions are changed for point and circular patch load and heat flux Green’s functions in order to derive the related displacement and temperature Green’s functions. Some numerical evaluations of Greens functions are represented to portray the dependency of response on thermo-mechanical coupling as well as the anisotropy of the medium.     

Gauging of SL(2,R) WZNW models and the Liouville field

We consider the gauging of theSL(2, R) WZNW model by its nilpotent subgroupE(1). The resulting space-time of the corresponding sigma model is seen to collapse to the one-dimensional field theory of Liouville.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 98. No. 3, pp. 337–342, March, 1994.     

A kinetic study of the electron-transfer in the reaction of tribenzylchlorotin with[CoW_(12)O_(40)]~(5-)

A kinetic study of the electron-transfer in the reaction of tribenzylchlorotin with potassium 12-tungsto cobalt(Ⅲ) ate ion, K_5[CoW_(12)O_(40)],abbreviated as Co(Ⅲ)W,has been performed in different solvents.The studies were carried out in methanol, ethanol,acetonitrile and acetic acid/water.The rate constants,reaction rates and activation parameters were calculated. Our findings show that the rate of disappearance of the Co(Ⅲ) is pseudo-first order.The kinetic data is strongly affected by used solvents.T...