Resonant two photon ionization of phenanthrene via its transientS 2 state

We report the vibrationally resolved photoelectron spectrum of phenanthrene obtained by two photon ionization via theS ₂ electronic state. The experiments were performed with picosecond laser pulses with a bandwidth sufficiently large to span a significant fraction of the intermediate resonance state. Therefore the photoelectron spectrum is dominated by signal corresponding to the unrelaxed intermediate resonance, in spite of this state's 420 fs lifetime.     

Regioselective synthesis of 3,4,6,7-tetrahydro-3,3-dimethyl-9-phenyl-2H-xanthene-1,8(5H,9H)-diones through ascorbic acid catalyzed three-component domino reaction

An efficient, three-component domino reaction of dimedone 1, aromatic aldehydes (2a–o), and 1,3-cyclohexanedione 1a in the regio-selective synthesis of 3,3-dimethyl-9-phenyl-2H-xanthene-1,8(5H,9H)-diones (3a–o) is reported. The desired product, 3 is efficiently promoted by ascorbic acid as an organo catalyst.     

N‐Methylpyrrolidone Hydroperoxide/Cs2CO3 as an Excellent Reagent System for the Hydroxy‐Directed Diastereoselective Epoxidation of Electron‐Deficient Olefins

This report introduces N‐methylpyrrolidone hydroperoxide (NMPOOH)/base as an excellent reagent system for hydroxy‐directed syn selective epoxidation of electron‐deficient olefins, characterized by high diastereoselectivity, short reaction times and remarkable chemoselectivity, especially in presence of oxidatively labile nitrogen or sulfur atoms. NMPOOH also proves efficient in the oxidation of electron‐deficient aromatic aldehydes, in the removal of oxazolidinone chiral auxiliary, and in the functionalization of alkenes and alkynes, showing wide application potential.     

Structural characterization of interfacial n-octanol and 3-octanol using molecular dynamic simulations

Structurally isomeric octanol interfacial systems, water/vapor, 3-octanol/vapor, n-octanol/vapor, 3-octanol/water, and n-octanol/water are investigated at 298 K using molecular dynamics simulation techniques. The present study is intended to investigate strongly associated liquid/liquid interfaces and probe the atomistic structure of these interfaces. The octanol and water molecules were initially placed randomly into a box and were equilibrated using constant pressure techniques to minimize bias within the initial conditions as well as to fully sample the structural conformations of the interface. An interface formed via phase separation during equilibration and resulted in a slab geometry with a molecularly sharp interface. However, some water molecules remained within the octanol phase with a mole fraction of 0.12 after equilibration. The resulting "wet" octanol interfaces were analyzed using density profiles and orientational order parameters. Our results support the hypothesis of an ordered interface only 1 or 2 molecular layers deep before bulk properties are reached for both the 3-octanol and water systems. However, in contrast to most other interfacial systems studied by molecular dynamics simulations, the n-octanol interface extends for several molecular layers. The octanol hydroxyl groups form a hydrogen-bonding network with water which orders the surface molecules toward a preferred direction and produces a hydrophilic/hydrophobic layering. The ordered n-octanol produces an oscillating low-high density of oxygen atoms out of phase with a high-low density of carbon atoms, consistent with an oscillating dielectric. In contrast, the isomeric 3-octanol has only a single carbon-rich layer directly proximal to the interface, which is a result of the different molecular topology. Both 3-octanol and n-octanol roughen the water interface with respect to the water/vapor interface. The "wet" octanol phases, in the octanol/water systems reach bulk properties in a shorter distance than the "dry" octanol/vapor interfaces.     

On external-memory MST, SSSP and multi-way planar graph separation

Recently external memory graph problems have received considerable attention because massive graphs arise naturally in many applications involving massive data sets. Even though a large number of I/O-efficient graph algorithms have been developed, a number of fundamental problems still remain open.The results in this paper fall in two main classes. First we develop an improved algorithm for the problem of computing a minimum spanning tree (MST) of a general undirected graph. Second we show that on planar undirected graphs the problems of computing a multi-way graph separation and single source shortest paths (SSSP) can be reduced I/O-efficiently to planar breadth-first search (BFS). Since BFS can be trivially reduced to SSSP by assigning all edges weight one, it follows that in external memory planar BFS, SSSP, and multi-way separation are equivalent. That is, if any of these problems can be solved I/O-efficiently, then all of them can be solved I/O-efficiently in the same bound. Our planar graph results have subsequently been used to obtain I/O-efficient algorithms for all fundamental problems on planar undirected graphs.     

Voltammetric Monitoring of Protein Aggregation from Solution Using Tris‐(2,2′‐Bipyridine) Osmium(II) Chloride Complex as an Electrocatalytic Mediator

The present work evaluates the feasibility of tracking protein aggregation voltammetrically by taking advantage of the intrinsic electroactivity of tyrosine residues. The electrocatalytic current due to the oxidation of tyrosine, mediated by tris‐(2,2′‐bipyridine)osmium(II) chloride, is used to report changes in protein aggregation state. We demonstrate, by the use of square wave voltammetry, that this system is able to differentiate between peptides containing equimolar tyrosine concentrations, and even detect tyrosine within large entities such as antibodies and insoluble amyloid fibrils. We also determine the aggregation time course of a model peptide, amyloid beta, detecting species with sizes from monomeric to insoluble aggregate. The method offers the prospect of monitoring biopharmaceutical aggregation and has potential to establish itself as a technique that is orthogonal to existing methods of aggregation detection.     

Measuring structural inhomogeneity of a helical conjugated polymer at high pressure and temperature

We report on X‐ray scattering measurements of helical poly[9,9‐bis(2‐ethylhexyl)‐fluorene‐2,7‐diyl] by mapping the sample with 10 μm spatial resolution from 0.3 GPa to 36 GPa. We follow the strongest 00l reflection, which moves toward higher scattering angles with pressure indicating planarization of helical polyfluorene. Lateral inhomogeneity is increased for >10 GPa concomitant with the solidification of the pressure transmitting medium (a 4:1 mixture of methanol and ethanol). We also follow the 00l reflection with increasing temperature at the constant pressure of 4.3 GPa in neon. We observe a sharp shift toward higher scattering angles indicative of a phase transition at 167–176 °C. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 392–396     

Potential anti-tubercular agents: Hexahydro-3-phenyl indazol-2-yl(pyridin-4-yl)methanones from anti-tubercular drug isoniazid and bis(substituted-benzylidene)cycloalkanones

A series of indazol-2-yl(pyridin-4-yl)methanones,4 were acquired from 2,6-bisbenzylidene cyclohexanones,3 and anti-tubercular drug(isoniazid),and their anti-tubercular impacts were screened.Among the test compounds used against Mycobacterium tuberculosis H37 Ra cell line in the microplate alamar blue assay,the compounds 4g-j revealed moderate anti-tubercular activity with MIC 12.5 μg/mL,comparable to standard drugs(streptomycin,MIC,6.25 u.g/mL,pyrazinamide,isoniazid and ciprofloxacin with MICs of 3.125 μg/mL).