Electrochemical capacitive properties of micron-sized chemically grown cadmium oxide discrete crystals

Stable electrochemical capacitive properties of chemically grown cadmium oxide film electrode composed of micron-sized discrete crystals in 1 M Na₂SO₄ electrolyte with a specific capacitance of 1190 mF/g studied over 1000 cycles are reported. Structural and morphological characterizations of micron-sized discrete CdO crystals have been carried out using power X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. Electrochemical capacitive properties of micron-sized CdO discrete crystals on tin-doped indium oxide electrode have been investigated using cyclic voltammetry and chronopotentiometry.     

Prediction of wall-pressure fluctuation in turbulent flows with an immersed boundary method

The objective of this paper is to assess the accuracy and efficiency of the immersed boundary (IB) method to predict the wall pressure fluctuations in turbulent flows, where the flow dynamics in the near-wall region is fundamental to correctly predict the overall flow. The present approach achieves sufficient accuracy at the immersed boundary and overcomes deficiencies in previous IB methods by introducing additional constraints – a compatibility for the interpolated velocity boundary condition related to mass conservation and the formal decoupling of the pressure on this surfaces. The immersed boundary-approximated domain method (IB-ADM) developed in the present study satisfies these conditions with an inexpensive computational overhead. The IB-ADM correctly predicts the near-wall velocity, pressure and scalar fields in several example problems, including flows around a very thin solid object for which incorrect results were obtained with previous IB methods. In order to have sufficient near-wall mesh resolution for LES and DNS computations, the present approach uses local mesh refinement. The present method has been also successfully applied to computation of the wall-pressure space–time correlation in DNS of turbulent channel flow on grids not aligned with the boundaries. When applied to a turbulent flow around an airfoil, the computed flow statistics – the mean/RMS flow field and power spectra of the wall pressure – are in good agreement with experiment.     

Phenothiazine Scope: Steric Strain Induced Planarization and Excimer Formation

Phenothiazine derivatives based on the 10‐phenyl‐10H‐phenothiazine ( NAS ) chromophore, namely 7‐phenyl‐7H‐benzo[c]phenothiazine ( NAS‐1 ) and 12‐phenyl‐12H‐benzo[a]phenothiazine ( NAS‐2 ), were designed and synthesized. NAS‐1 and NAS‐2 are constitutional isomers with different steric strains imposed on the phenothiazine core moiety. In solution, the more‐strained NAS‐2 possesses a bent structure and undergoes photoinduced structural planarization (PISP). In the crystal, despite the absence of PISP, bent NAS‐2 exhibits prominent excimer emission as well as emission mechanochromism, which is not observed in the planar‐like NAS and NAS‐1 . This unconventional observation results from the bent core structure facilitating π–π stacking of the peripheral naphthalene moieties. Two‐photon‐coupled depth‐dependent emission shows spectral differences between the surface and kernel of the NAS‐2 crystal, and is believed to be a general phenomenon, at least in part, for materials exhibiting emission mechanochromism.     

Synthesis of syn-vicinal diamines via the stereoselective allylation of acyclic chiral α-amino aldimines

The stereoselective allylation of acyclic chiral α-amino aldimines affording vicinal diamines, mediated by various Lewis acids (TiCl₄, SnCl₄, MgBr₂·OEt₂, BF₃·OEt₂, ZnCl₂), is described. The TiCl₄-mediated allylation of an α-N-Boc aldimine afforded the allylation product with syn-selectivity, which in turn was used for the synthesis of an intermediate of an oseltamivir derivative.     

13C n.m.r. investigation on the first and second nitrogen protonation in the diazanaphthalenes

The ¹³C chemical shifts of the diazanaphthalenes have been recorded as a function of the pH value, providing classical titration curves. From these curves the pK₁ and pK₂ values have been determined taking into account the activity coefficients. The changes in ¹³C chemical shift under the influence of nitrogen protonation (Δδ) can be described by two protonation parameter sets.     

A facile one-pot synthesis of alkyl aryl sulfides from aryl bromides

A convenient one-pot synthetic method for the formation of alkyl aryl sulfides from various alkyl halides and lithium aryl thiolates that are prepared in situ by direct halogen-lithium exchange is reported. In particular, the method overcomes many of the problems encountered in previous reports; it is very quick, catalyst-free, and does not involve use of unstable aryl thiols.     

Identification, quantification and comparison of major non-polar lipids in normal and dry eye tear lipidomes by electrospray tandem mass spectrometry

Millions of individuals suffer from a health condition known as keratoconjunctivitis sicca (KCS, also known as 'dry eye'). Studies have indicated that the lipids in the tear film layer, which covers the outer portion of the eye, may be directly correlated with the existence of dry eye syndrome. By identifying and comparing the major, non-polar lipids in normal eye tears with a dry eye model, it may be possible to identify a symptom of, or a contributing factor to, dry eye. Electrospray tandem mass spectrometry (ES-MS/MS) was used to identify and compare the non-polar lipids, detected as lithium adducts, from normal and dry eye tear samples obtained from rabbits. A limited number of normal human tear samples were also examined for lipid content, and a close resemblance to rabbit was observed. Three distinct regions were delineated in the ES mass spectra of the non polar lipids, m/z 20-500, 500-800 and 800-1100. A common feature noted among identified lipid components was a glycerol backbone with fatty acyl substituents attached. Product ion spectra were obtained for lithiated monoacyl-, 1,2- and 1,3-diacyl- and triacylglyceride standards. Newly proposed structures and fragmentation pathways for the major product ions are presented for the 1,2- and 1,3-diglycerides, and also for the monoglyceride. New approaches to distinguishing asymmetric 1,2-diglycerides and 1,2- from 1,3-diglycerides are proposed. For the rabbit tear samples, the m/z 20-500 range contains monoester diols with empirical formulas C(n)H(2n)O(4), the m/z 500-800 range includes diesters with empirical formulas C(n)H(2n-2)O(5) and the m/z 800-1100 range contains triesters with empirical formulas C(n)H(2n-4)O(6). Also found in the extracts were three isoprene acetals (terpenoids).     

Total synthesis of sphingofungin F

[reaction: see text] A concise, stereocontrolled synthesis of sphingofungin F was achieved. Key features involve diastereoselective oxazoline formation catalyzed by palladium(0), MgBr(2)-promoted gamma-alkoxy allylic stannane addition, and palladium(0)-catalyzed coupling of a vinyl iodide with an organozinc reagent.     

Coherence switching in a four-level system: quantum switching

Dark resonance switching among three-laser interactions in a four-level system is observed by using an enhanced nondegenerate four-wave mixing technique. This coherence switching mechanism is based on simultaneous suppression and enhancement of two-photon absorption and has a novel application to high-speed optical switches.     

A formal total synthesis of dactylol

The tetracyclic epoxide 16 was prepared in stereocontrolled fashion from 4,4-dimethylcyclohexanone, the key steps being Saegusa ring expansion of its silyl enol ether to 5, ortho ester Claisen rearrangement of 7, and cyclization of 9 without rupture of the three-membered ring. Epoxide 16 had previously been transformed into dactylol, thus completing the formal total synthesis.