Assessment of structural analysis technology for static collapse of elastic cylindrical shells

The prediction of the ultimate load-carrying capability for compressively loaded shell structures is a challenging nonlinear analysis problem. Selected areas of finite element technology research and nonlinear solution technology are assessed. Herein, a finite element analysis procedure is applied to four cylindrical shell collapse problems which have been used by computational structural mechanics researchers in the past. This assessment will focus on a number of different shell element formulations and on different approaches used to account for geometric nonlinearities. The results presented confirm that these aspects of nonlinear shell analysis can have a significant effect on the predicted nonlinear structural response. All analyses were performed using a single software system which allowed a convenient assessment of different element formulations with a consistent approach to solving the discretized nonlinear equations.     

The number of rounds needed to exchange information within a graph

In [3] Cederbaum proposes the problem of finding a labelling of a connected graph G which minimizes the number of rounds needed to exchange information between all the points, where a round consists of the vertices of G each broadcasting once in order of their labels. In this paper we give a complete solution to the problem.     

Cyclohexanecarboxamide

The title compound, C₇H₁₃NO, forms R²₂(8) N—H...O hydrogen‐bonded dimers and C4 N—H...O‐linked chains, which are further stabilized by a C—H...O interaction. The combination of these interactions results in a hydrogen‐bonded network parallel to (100), with a motif that can be described by the secondary graph set R⁴₆(16). The existence of the same hydrogen‐bonding motif in 1‐phenylcyclopentanecarboxamide and 1‐(2‐bromophenyl)cyclohexanecarboxamide [Lemmerer & Michael (2008). CrystEngComm, 10 , 95–102 indicates that replacing the H atom on position 1 with a more bulky group does not necessarily disrupt the observed hydrogen‐bonding pattern. The presence of a C—H...O interaction to stabilize the R⁴₆(16) network does, however, seem to be required. In addition, the title compound is isomorphous with a previously published structure of cyclopentanecarboxamide [Winter et al. (1981). Acta Cryst. B 37 , 2183–2185].     

Nonlinear Instability for the Critically Dissipative Quasi-Geostrophic Equation

We prove that linear instability implies non-linear instability in the energy norm for the critically dissipative quasi-geostrophic equation.     

Stimulus set effects in the similarity ratings of unfamiliar complex sounds

This study examined the effect of the distribution of values for various acoustic properties on the similarity ratings obtained in a paired-comparison study of complex sounds. Listeners rated the similarity of tones and tone complexes in one of four sets. Across the four sets both component frequency and the number of components in the stimuli were drawn from distributions that were either categorical or noncategorical. Other acoustic properties were distributed similarly in all sets. Solutions suggested that frequency was most important to the ratings, followed by the number of components in each critical band. Results suggest that when the values of an acoustic property are distributed categorically, its importance to similarity ratings increases relative to that observed with a less categorical distribution.     

Fluorescent 1,10-phenanthroline-containing oligonucleotides distinguish between perfect and mismatched base pairing

[structure: see text] A fluorescent deoxyuridine analogue is sensitive to the polarity of its environment and exhibits a distinct emission profile in single- vs double-stranded oligonucleotides. Emission-monitored denaturation curves of internally modified dU(phen) duplexes are characteristic of the base opposite dU(phen) and distinguish between perfect and mismatched complementary oligonucleotides.     

Rational design to block amino acid editing of a tRNA synthetase

Investigations in chemical biology have focused on the synthesis of custom-designed proteins with site-specific incorporation of novel amino acids. Their success requires stable production of misacylated tRNAs. Utilization of aminoacyl-tRNA synthetases has been hindered because of enzyme molecular recognition mechanisms that ensure high fidelity of protein synthesis. Leucyl-tRNA synthetase naturally misaminoacylates chemically diverse standard and nonstandard amino acids, but contains a separate amino acid editing active site to hydrolyze incorrectly mischarged tRNAs. In this work, a rational mutagenesis design to block enzyme editing is described and involves substitution of bulky amino acids into the amino acid binding pocket of the hydrolytic active site. These engineered enzymes stably misacylated isoleucine to tRNALeu. The use of these mutant leucyl-tRNA synthetases has the potential to produce pools of mischarged tRNAs that are linked to nonstandard amino acids for in vitro translation. In addition, since many of the leucyl-tRNA synthetases do not interact with or rely upon the tRNA anticodon for identity, these enzymes may offer an excellent scaffold for the development of orthogonal tRNA synthetase/tRNA pairs that can potentially be used to customize protein synthesis.