Characterization of Standard Reference Material 2941, uranyl-ion-doped glass, spectral correction standard for fluorescence

Standard Reference Material^® (SRM^®) 2941 is a cuvette-shaped, uranyl-ion-doped glass, recommended for use for relative spectral correction of emission and day-to-day performance validation of fluorescence spectrometers. Properties of this standard that influence its effective use or contribute to the uncertainty in its certified emission spectrum have been explored here. These properties include its photostability, absorbance, dissolution rate in water, anisotropy, temperature coefficient of fluorescence intensity, and fluorescence lifetimes. The expanded uncertainties in the certified spectrum are about 4% around the peak maximum at 526 nm, using an excitation wavelength of 427 nm. The SRM also exhibits a strong resistance to photodegradation, with no measurable decrease in fluorescence intensity even after 8 h of laser irradiation.     

New Tripodal, “Supercharged” Analogues of Adenosine Nucleotides: Inhibitors for the Fhit Ap3A Hydrolase

Methanetrisphosphonic acids provide a branch point for synthetic nucleotide analogues which can be exploited either to generate novel tripodal nucleotides or to incorporate additional negative charge into linear analogues relative to the parent nucleotide, as exemplified in the picture for ATP and diadenosine tetraphosphate (Ap₄A). These compounds show valuable discriminatory behavior as competitive inhibitors for the tumor suppressor protein Fhit and a second Ap_nA pyrophosphohydrolase. X=H, Cl, F.     

Adapting the spectral vanishing viscosity method for large-eddy simulations in cylindrical configurations

During the last decade the spectral vanishing viscosity (SVV) method has been adopted successfully for large-eddy-type simulations (LES) with high-order discretizations in both Cartesian and cylindrical coordinate systems. For the latter case, however, previous studies were confined to annular domains. In the present work, we examine the applicability of SVV in cylindrical coordinates to flows in which the axis region is included, within the setting of an exponentially convergent spectral element–Fourier discretization. In addition to the ‘standard’ SVV viscosity kernel, two modified kernels with enhanced stabilization in the axis region are considered. Three fluid flow examples are considered, including turbulent pipe flow. The results, on the one hand, show a surprisingly small influence of the SVV kernel, while on the other, they reveal the importance of spatial resolution in the axis region.     

Constant darkness is a circadian metabolic signal in mammals

Environmental light is the 'zeitgeber' (time-giver) of circadian behaviour. Constant darkness is considered a 'free-running' circadian state. Mammals encounter constant darkness during hibernation. Ablation of the master clock synchronizer, the suprachiasmatic nucleus, abolishes torpor, a hibernation-like state, implicating the circadian clock in this phenomenon. Here we report a mechanism by which constant darkness regulates the gene expression of fat catabolic enzymes in mice. Genes for murine procolipase (mClps) and pancreatic lipase-related protein 2 (mPlrp2) are activated in a circadian manner in peripheral organs during 12 h dark:12 h dark (DD) but not light-dark (LD) cycles. This mechanism is deregulated in circadian-deficient mPer1-/-/mPer2m/m mice. We identified circadian-regulated 5'-AMP, which is elevated in the blood of DD mice, as a key mediator of this response. Synthetic 5'-AMP induced torpor and mClps expression in LD animals. Torpor induced by metabolic stress was associated with elevated 5'-AMP levels in DD mice. Levels of glucose and non-esterified fatty acid in the blood are reversed in DD and LD mice. Induction of mClps expression by 5'-AMP in LD mice was reciprocally linked to blood glucose levels. Our findings uncover a circadian metabolic rhythm in mammals.     

Aqueous solutions containing amino acids and peptides. Part 19: The enthalpic coefficients for the interactions of N-acetylsarcosinamide with 2-(N-acetylamino)acyl amides at 25°C

Enthalpies of dilution both of solutions of N-acetylsarcosinamide and of ternary solutions equimolal in N-acetylsarcosinamide and N-acetylglycinamide, N-acetyl-L-alaninamide, N-acetyl-L-valinamide or N-acetyl-L-leucinamide have been determined by a microcalorimetric method. The results were employed to calculate the pairwise enthalpic coefficients for both homotactic (like-like) and heterotactic (like-unlike) solute interactions. These pairwise interaction coefficients have been analyzed by means of a group additivity approach and some comments on the utility of this, when applied to such systems, are made.