Bubbles pinned on electrodes: Friends or foes of aqueous electrochemistry?

Electrochemists and engineers regard adherent gas bubbles as redox-inactive and therefore blocking entities. Adhesion of bubbles at electrodes generally carries an energy penalty. But this is not always the case: bubbles pinned on an electrode surface initiate the oxidation of water-soluble species under conditions where such reactions would normally be considered impossible. Here we critically review the recent literature that is beginning to unveil the novel concept of on-water electrochemistry. Harnessing electrochemical reactivity of the water–gas–electrode interface has the potential to become a game-changer in organic electrosynthesis, accelerating the transition toward a sustainable chemical industry by simplifying the direct integration of renewable electricity into the production of commodity chemicals.     

Photoinduced electron transfer between anionic fluorophores and methyl viologen in homogeneous and microheterogeneous media

The rate and extent of photoinduced electron transfer change significantly as a result of confinement in nanovolumes. Study of such processes is an active area of research in physical chemistry. The effect is most interesting when the molecules that participate in PET are charged. In the present article, the modulation of PET has been studied for two anionic fluorophores: Lucifer Yellow CH and chlorin p₆ with Methylviologen dication. PET, manifested in the quenching of fluorescence of the fluorophores, has been modulated by incorporating the molecules in organized assemblies like micelles, reverse micelles and supramolecular hosts. The dynamics of the process has been monitored in the femtosecond to nanosecond timescale. The modulation of the electron transfer has been found to be occurring mainly due to the disruption of contact ion pairs formed between the fluorophores and the quencher.     

Biochemical localization of a protein involved in synthesis of Gluconacetobacter hansenii cellulose

Using subcellular fractionation and Western blot methods, we have shown that AcsD, one of the proteins encoded by the Acetobacter cellulose synthase (acs) operon, is localized in the periplasmic region of the cell. AcsD protein was heterologously expressed in Escherichia coli and purified using histidine tag affinity methods. The purified protein was used to obtain rabbit polyclonal antibodies. The purity of the subcellular fractions was assessed by marker enzyme assays.     

From homogenization to averaging in cellular flows

We consider an elliptic eigenvalue problem with a fast cellular flow of amplitude A  , in a two-dimensional domain with L²$L^2$ cells. For fixed A  , and L→∞$L\to \infty$, the problem homogenizes, and has been well studied. Also well studied is the limit when L   is fixed, and A→∞$A\to \infty$. In this case the solution equilibrates along stream lines.     

Embedding theorems on hyperelliptic varieties

In this paper, we investigate linear systems on hyperelliptic varieties. We prove analogues of well-known theorems on abelian varieties, like Lefschetz’s embedding theorem and higher k-jet embedding theorems. Syzygy or \(N_p\) -properties are also deduced for appropriate powers of ample line bundles. This is a first result on linear series, on hyperelliptic varieties.     

Manganese Oxide Octahedral Molecular Sieves (OMS‐2) Multiple Framework Substitutions: A New Route to OMS‐2 Particle Size and Morphology Control

Self‐assembled multidoped cryptomelane hollow microspheres with ultrafine particles in the size range of 4–6 nm, and with a very high surface area of 380 m² g^?1 have been synthesized. The particle size, morphology, and the surface area of these materials are readily controlled via multiple framework substitutions. The X‐ray diffraction and transmission electron microscopy (TEM) results indicate that the as‐synthesized multidoped OMS‐2 materials are pristine and crystalline, with no segregated metal oxide impurities. These results are corroborated by infrared (IR) and Raman spectroscopy data, which show no segregated amorphous and/or crystalline metal impurities. The field‐emission scanning electron microscopy (FESEM) studies confirm the homogeneous morphology consisting of microspheres that are hollow and constructed by the self‐assembly of pseudo‐flakes, whereas energy‐dispersive X‐ray (EDX) analyses imply that all four metal cations are incorporated into the OMS‐2 structure. On the other hand, thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC) demonstrate that the as‐synthesized multidoped OMS‐2 hollow microspheres are more thermally unstable than their single‐doped and undoped counterparts. However, the in‐situ XRD studies show that the cryptomelane phase of the multidoped OMS‐2 hollow microspheres is stable up to about 450°C in air. The catalytic activity of these microspheres towards the oxidation of diphenylmethanol is excellent compared to that of undoped OMS‐2 materials.     

Diversity-oriented, one-pot, multi-component synthesis of substituted uracil derivatives

Abstract  

With the emergence of high throughput screening of bioactive molecules, there is constant need for the development of new strategies for diversity-oriented synthesis. We describe here a novel one-pot multicomponent reaction for the synthesis of uracil derivatives using easily available starting materials. This new synthetic strategy provides easy access to diverse uracil derivatives in moderate to good yields.     

Buried channel charge-coupled device on gas-source MBE grown InP

The first epitaxial-channel InP CCDs on semi-insulating substrates have been demonstrated using gas-source MBE grown layers. Channel isolation was achieved using a mesa etch, and the two level overlapping gate structure was insulated using indirect plasma enhanced CVD grown SiO/sub 2/. Initial results indicate stable device operation with charge transfer efficiencies, at 1-3 MHz operating frequencies, of approximately 0.99.<>     

Effect of Noise on Analog Circuit Testing

The effect of test environment noise (tester noise) on test waveforms is considered. We show that tests generated ignoring the tester noise characteristics are prone to failure when actually applied to the circuit-under-test (CUT). The failure may result in the good circuit being declared faulty or the faulty circuit being declared good. This failure is independent of the fault model and nature of the test, i.e., AC or DC, time domain or frequency domain. We characterize the total noise at the primary outputs (PO's) of the circuit using second order statistics. We use the noise power spectrum and root mean square (RMS) values to make decisions about the test waveforms and recommend more noise-robust tests. For non-linear circuits we use the Central Limit Theorem of statistics to approximate narrow band noise at a primary input (PI) by a sum of sinusoidal distributions, and we use Monte-Carlo simulations to determine the noise at the PO's in the time domain. Results of experiments on an instrumentation amplifier, a biquadratic filter, and a Gilbert multiplier are presented, which prove that valid tests in a noise-free environment are invalid when tester noise is considered.