Emission studies of pyrene solutions

Emission spectra of pyrene in hexane have been obtained over a temperature range (from 130 to 260 K) that has not been explored before for concentrations ranging from 10^?4 mole/? to 2 × 10^?2 mole/?. A conventional and new approximation which does not depend on the experimental set-up response functions has been used for evaluating pyrene excimer association energy W_DM and other pyrene parameters. In both methods W_DM agrees quite satisfactorlly, at all concentrations used, with that reported in the literature and obtained by other techniques. However, both approximation fail to yield the right values of the rate parameters at concentrations ? 2 g/?. This set the upper limit of sample solubility to be at C = 2g/? for our range of temperature. Furthermore, the new approximation can probably be used at higher concentration (for higher range of temperature) and even may be used for other organic molecules. There was also no difference in the ratio of the excimer (I_D) to monomer (I_M) quantum yields when an intense laser beam was used as a source of excitation rather than a super-pressure Hg-lamp. This suggested that the concentrations we used might not be large enough. As a result, the laser beam would not create enough density of excited molecules to affect the ratio of I_D/I_M.     

Three-dimensional blow-up solutions of the Navier-Stokes equations

In this paper we extend the plane blow-up results of Grundy& McLaughlin (1997) to the three-dimensional Navier-Stokes equations.Using a solution structure originally due to Lin we first providenumerical evidence for the existence of blow-up solutions on- < x, z < , 0 y 1 with boundary conditions on y = 0and y = 1 involving derivatives of the velocity components.The formulation enables us to consider plane and radial flowas special cases. Various features of the computations are isolatedand are used to construct a formal asymptotic solution closeto blow-up. We show that the numerical and asymptotic analysesprovide a mutually consistent global picture which supportsthe conclusion that, for the family of problems we considerhere, blow-up in fact can take place in three dimensions butat an inverse linear rate rather than the faster inverse squareof the plane case.     

Long-term retention of ice-nucleating active Pseudomonas fluorescens by overwintering colorado potato beetles

Ice nucleating-active Pseudomonas fluorescens F264C was fed to Colorado potato beetles to determine bacterial retentioin in the beetle gut and its effect on the cold hardiness of this insect pest. The bacrterium was present in beetles recovered after overwintering in the field, seven months after their exposure to P. fluorescens. Retention was evident not only in the detection of the P. fluorescens ice nucleating gene, inaW, in bacterial cultures from beetle guts but also in the elevated supercooling points of some treated beetles.     

Mixing quantification by visual imaging analysis

This paper reports on development of a method for quantifying two measures of mixing, the scale and intensity of segregation, through flow visualization, video recording, and software analysis. This non-intrusive method analyzes a planar cross section of a flowing system from an instantaneous data record, thereby eliminating the need for statistical analysis of a large number of point measurements at multiple locations throughout the system to characterize the mixing. The method is applied to a cold flow model of a high temperature, gas/solid reactor so that reactor design and operation can be optimized to promote reaction efficiency. This method may be useful for studying a variety of mixing systems in which multiphase components or tracers are visually distinguishable.List of symbols mixing coefficient (defined by Eq. (17)) - standard deviation - a mixing coefficient (defined by Eq. (16)) - C(k, m) sample grayscale covariance (defined by Eq. (3)) - d distance (defined by Eq. (8)) - D divisor (defined by Eq. (3)) - d ^* value of d for which R _I (d) approaches zero - D ₅₀ mass median diameter - I intensity of segregation (defined by Eq. (20)) - M sample size (defined by Eq. (16)) - n number of contiguous pixels - n ^* value of n for which SSE _Q /SSE _L is maximized - n _c number of columns of pixels - N_R number of rows of pixels - P number of pixels per linear distance - r radius of Cold Flow Model - R(k, m) sample correlation function (defined by Eq. (5)) - R _C (k) column correlation function (defined by Eq. (7)) - R _I (d) isotropic correlation function (defined by Eq. (9)) - R _R (m) row correlation function (defined by Eq. (6)) - SSE _Q residual sum of squared errors from the least squares fit of the quadratic model to Eq. (14) - SSE _L residual sum of squared errors from the least squares fit of the linear model to Eq. (14) - S _y ² sample grayscale variance (defined by Eq. (2)) - S _c column scale of segregation (defined by Eqs. (7) and (13)) - S _D Danckwerts' scale of segregation (defined by Eq. (10)) - S _R row scale of segregation (defined by Eqs. (6) and (13)) - S _s scale measure developed in this paper (defined by Eq. (13)) - V _n sample variance of contiguous pixels (defined by Eq. (11)) - V _n ^* normalized variance function (defined by Eq. (12)) - sample grayscale mean (defined by Eq. (1)) - Y _i,j grayscale value at pixel (i,j)     

Low-lying (K π = 0+) states of gadolinium isotopes

The sd-interacting boson approximation (sd-IBA) and the df-interacting boson approximation (df-IBA) can be related to each other and the states of the interacting boson approximation model can be identified with the fully symmetric states in the sdf interacting boson approximation model. A systematic study of the sdf-IBA model showed that the constructed Hamiltonian can successfully describe the strong octupole correlations in the deformed nuclei. We showed that the interacting boson approximation may account for many of these K ^π ?=?0⁺ states. It was found that the calculated energy spectra of the gadolinium isotopes agree quite well with the experimental data. The observed B(E2) values were also calculated and compared with the experimental data.     

Efforts Toward the Direct Experimental Characterization of Enzyme Microenvironments: Tyrosine100 in Dihydrofolate Reductase

State secrets : Site‐specific deuteration and FTIR studies reveal that Tyr100 in dihydrofolate reductase plays an important role in catalysis, with a strong electrostatic coupling occuring between Tyr100 and the charge that develops in the hydride‐transfer transition state (see picture, NADP⁺ purple, Tyr100 green). However, relaying correlated motions that facilitate catalysis from distal sites of the protein to the hydride donor may also be involved.

     

PHOTOREACTIVITY OF 5-GERANOXYPSORALEN AND LACK OF PHOTOREACTION WITH DNA

5-Geranoxypsoralen, commonly called bergamottin, a major furocoumarin contained in bergamot oil, is reported in vitro as a highly photoreactive psoralen. In ethanol, it exhibits quite a high triplet state quantum yield (approximately 0.37). The triplet state is involved in subsequent photochemistry which depends on the initial concentration and on the presence of oxygen. In contrast to most psoralens, absorption and fluorescence data suggest that 5-geranoxypsoralen does not interact with DNA in the dark. No UVA-induced interstrand cross-links in DNA were shown.     

A Facile System for Encoding Unnatural Amino Acids in Mammalian Cells

A shuttle system has been developed to genetically encode unnatural amino acids in mammalian cells using aminoacyl‐tRNA synthetases (aaRSs) evolved in E. coli. A pyrrolysyl‐tRNA synthetase (PylRS) mutant was evolved in E. coli that selectively aminoacylates a cognate nonsense suppressor tRNA with a photocaged lysine derivative. Transfer of this orthogonal tRNA–aaRS pair into mammalian cells made possible the selective incorporation of this unnatural amino acid into proteins.