12-hydroxy-1-azaperylene-limiting case of the ESIPT system: enol-keto tautomerization in S0 and S1 states

Absorption, fluorescence, and fluorescence excitation spectra of 12-hydroxy-1-azaperylene (HAP) and 1-azaperylene were studied in n-alkane matrices at 5 K. Two stable tautomers of HAP, each of them in n-nonane embedded in two sites, were identified and attributed to the enol and keto forms. Theoretical calculations of the energy and vibrational structure of the spectra suggest that tautomer A, with the (0, 0) transition energy at 18,980 ± 10 cm(-1) (and 19,060 ± 10 cm(-1) in the high energy site), should be identified as the keto form, whereas tautomer B, with the (0, 0) energy at 19,200 ± 20 cm(-1) (19,290 ± 20 cm(-1)), as the enol form. Observation of absorption and fluorescence of both tautomeric forms and lack of large Stokes shift of fluorescence of the keto form classify HAP as the limiting case of the excited-state intramolecular proton transfer system.     

Sonochemical coating of cotton and polyester fabrics with "antibacterial" BSA and casein spheres

A novel antibacterial coating for cotton and polyester fabrics has been developed by using drug-loaded proteinaceous microspheres made of bovine serum albumin and casein proteins. The microbubbles were created and anchored onto the fabrics (see figure) in a one-step reaction that lasts 3 min. The sonochemically produced "antibacterial fabrics" have been characterized. The efficiency of the sonochemical process in converting the native proteins into microspheres, encapsulating the drug, and coating the fabric has also been studied.     

Sartorymensin,a new indole alkaloid,and new analogues of tryptoquivaline and fiscalins produced by Neosartorya siamensis (KUFC 6349)

Seven new indole alkaloids including a new indoloazepinone derivative (2), two new quinazolinone derivatives (7, 8) and four new pyrazinoquinazolinone derivatives: epi-fiscalin C (10), epi-fiscalin A (12), neofiscalin A (13), epi-neofiscalin A (14) were isolated, together with 4-dihydroxy-3-methylacetophenone (1), tryptoquivaline (3), tryptoquivalines L (4), H (5), F (6) as well as fiscalins A (11) and C (9), from the culture of the fungus Neosartorya siamensis (KUFC 6349). The absolute configuration of the stereogenic carbons of the previously reported tryptoquivalines F, H, L was revised using the data obtained from an X-ray analysis of tryptoquivaline l and the NOESY correlations. The structures of the new pyrazinoquinazolinone derivatives (10, 12, 13, 14) were established based on 1D and 2D NMR spectral analysis, and the absolute configuration of their stereogenic carbons was determined by an X-ray crystallographic analysis of fiscalin C (9) and a new compound epi-fiscalin C (10), in conjunction with the correlations observed in their NOESY and long range COSY spectra. Compounds 2–8 and 12 were evaluated for their in vitro growth inhibitory activity on the human U373 and Hs683 glioblastoma, the A549 non-small cell lung cancer, the MCF-7 breast cancer and the SKMEL-28 melanoma cell lines by MTT colorimetric assay.     

A comparison of two-component and four-component approaches for calculations of spin-spin coupling constants and NMR shielding constants of transition metal cyanides

Relativistic density functional theory (DFT) calculations of nuclear spin-spin coupling constants and shielding constants have been performed for selected transition metal (11th and 12th group of periodic table) and thallium cyanides. The calculations have been carried out using zeroth-order regular approximation (ZORA) Hamiltonian and four-component Dirac-Kohn-Sham (DKS) theory with different nonrelativistic exchange-correlation functionals. Two recent approaches for representing the magnetic balance (MB) between the large and small components of four-component spinors, namely, mDKS-RMB and sMB, have been employed for shielding tensor calculations and their results have been compared. Relativistic effects have also been analysed in terms of scalar and spin-orbit contributions at the two-component level of theory, including discussion of heavy-atom-on-light-atom effects for (1)J(CN), σ(C), and σ(N). The results for molecules containing metals from 4th row of periodic table show that relativistic effects for them are small (especially for spin-spin coupling constants). The biggest effects are observed for the 6th row where nonrelativistic theory reproduces only about 50%-70% of the two-component ZORA results for (1)J(MeC) and about 75% for heavy metal shielding constants. It is important to employ a full Dirac picture for calculations of heavy metal shielding constants, since ZORA reproduces only 75%-90% of the DKS results. Smaller discrepancies between ZORA-DFT and DKS are observed for nuclear spin-spin coupling constants. No significant differences are observed between the results obtained using mDKS-RMB and sMB approaches for magnetic balance in four-component calculations of the shielding constants.     

Conical intersection seams in polyenes derived from their chemical composition

The knowledge of conical intersection seams is important to predict and explain the outcome of ultrafast reactions in photochemistry and photobiology. They define the energetic low-lying reachable regions that allow for the ultrafast non-radiative transitions. In complex molecules it is not straightforward to locate them. We present a systematic approach to predict conical intersection seams in multifunctionalized polyenes and their sensitivity to substituent effects. Included are seams that facilitate the photoreaction of interest as well as seams that open competing loss channels. The method is based on the extended two-electron two-orbital method [A. Nenov and R. de Vivie-Riedle, J. Chem. Phys. 135, 034304 (2011)]. It allows to extract the low-lying regions for non-radiative transitions, which are then divided into small linear segments. Rules of thumb are introduced to find the support points for these segments, which are then used in a linear interpolation scheme for a first estimation of the intersection seams. Quantum chemical optimization of the linear interpolated structures yields the final energetic position. We demonstrate our method for the example of the electrocyclic isomerization of trifluoromethyl-pyrrolylfulgide.     

Transport and deposition of colliding particles in turbulent channel flows

The purpose of this paper is twofold: (i) to present statistical models that describe particle–turbulence interactions as well as particle–particle collisions and (ii) to gain a better understanding of the effect of inter-particle collisions on transport, deposition, and preferential concentration of heavy particles in turbulent channel flows. The models presented are based on a kinetic equation for the probability density function of the particle velocity distribution in anisotropic turbulent flow. The model predictions compare reasonable well with numerical simulations and properly reproduce the crucial trends of computations.     

Application of Rheological Models in Prediction of Turbulent Slurry Flow

The paper deals with fully developed steady turbulent flow of slurry in a circular straight and smooth pipe. The Kaolin slurry consists of very fine solid particles, so the solid particles concentration, and density, and viscosity are assumed to be constant across the pipe. The mathematical model is based on the time averaged momentum equation. The problem of closure was solved by the Launder and Sharma k-ε turbulence model (Launder and Sharma, Lett Heat Mass Transf 1:131–138, 1974) but with a different turbulence damping function. The turbulence damping function, used in the mathematical model in the present paper, is that proposed by Bartosik (1997). The mathematical model uses the apparent viscosity concept and the apparent viscosity was calculated using two- and three-parameter rheological models, namely Bingham and Herschel–Bulkley. The main aim of the paper is to compare measurements and predictions of the frictional head loss and velocity distribution, taking into account two- and three-parameter rheological models, namely Bingham and Herschel–Bulkley, if the Kaolin slurry possesses low, moderate, and high yield stress. Predictions compared with measurements show an observable advantage of the Herschel–Bulkley rheological model over the Bingham model particularly if the bulk velocity decreases.     

Relative Topological Pinsker Factors and Entropy Pairs

 A relative version of the topological m-Pinsker factor is given and its relationships with other notions of relative Pinsker factors are investigated. Relative topological Pinsker factors (of various kinds) of relative products are described. (Received 4 December 2000; in revised form 1 June 2001)     

Randomized allocation processes

Many dynamic resource allocation and on‐line load balancing problems can be modeled by processes that sequentially allocate balls into bins. The balls arrive one by one and are to be placed into bins on‐line without using a centralized controller. If n balls are sequentially placed into n bins by placing each ball in a randomly chosen bin, then it is widely known that the maximum load in bins is ln n /ln ln n?(1+o(1)) with high probability. Azar, Broder, Karlin, and Upfal extended this scheme, so that each ball is placed sequentially into the least full of d randomly chosen bins. They showed that the maximum load of the bins reduces exponentially and is ln ln n/In d+Θ(1) with high probability, provided d<2. In this paper we investigate various extensions of these schemes that arise in applications in dynamic resource allocation and on‐line load balancing. Traditionally, the main aim of allocation processes is to place balls into bins to minimize the maximum load in bins. However, in many applications it is equally important to minimize the number of choices performed (the allocation time). We study adaptive allocation schemes that achieve optimal tradeoffs between the maximum load, the maximum allocation time, and the average allocation time. We also investigate allocation processes that may reallocate the balls. We provide a tight analysis of a natural class of processes that each time a ball is placed in one of d randomly chosen bins may move balls among these d bins arbitrarily. Finally, we provide a tight analysis of the maximum load of the off‐line process in which each ball may be placed into one of d randomly chosen bins. We apply this result to competitive analysis of on‐line load balancing processes. ©2001 John Wiley & Sons, Inc. Random Struct. Alg., 18: 297–331, 2001     

Efficient Synthesis of Functionalized 2H-Thiopyrans via Hetero-Diels-Alder Reactions of an Enaminothione with Electrophilic Olefins

Summary.  The hetero-Diels-Alder reaction of 3-dimethylamino-1-(2-thienyl)-2-propene-1-thione (diene) with substituted β-nitrostyrenes, as well as maleic and fumaric acids (dienophiles) yielded 3,4-dihydro-2H-thiopyran derivatives. The treatment of some of those cycloadducts with acetic acid caused elimination of dimethylamine, affording stable 2H-thiopyrans. A reaction of the diene with maleic anhydride furnished a cycloadduct which underwent spontaneous rearrangement to form an N,N-dimethylamide derivative. Cycloadditions of the diene to maleimide, N-phenylmaleimide, maleic acid monoanilide, diethyl maleate, fumarate, and butenolide carried out in the presence of acetic anhydride were followed by elimination of dimethylamine under formation of stable 2H-thiopyran derivatives. Received February 19, 2001. Accepted (revised) March 12, 2001