On Unbounded Tolerable Solution Sets

We prove that the nonempty tolerable solution set of the interval linear system Ax = b is unbounded if and only if the interval matrix of the system has linearly dependent degenerate columns. Also, we prove that the tolerable solution set may be represented as a sum of the linear subspace {c ε ℝⁿ ∨ Ac = 0} and a bounded convex polyhedron and propose a way for suitable estimation of unbounded tolerable solution sets.     

Comparison of the NMR spectroscopy solution structures of pyranosyl-rNA and its nucleo-delta-peptide analogue

The design of polymers that could mimic biomolecules in their ability to form assemblies similar to ribo- and deoxyribonucleic acids has become an attractive field of chemical research, and NMR spectroscopy has played a vital role in the determination of the three-dimensional structure of these newly designed nonnatural polymers. The structure of a self-complementary octamer duplex of pyranosyl-RNA (pRNA) has been determined by using NMR spectroscopy experimental data and an Xplor structure calculation protocol. The structure has been compared with the structure of a duplex formed by a designed nucleo-delta-peptide analogue of pRNA. The two duplexes assume one predominant conformation and show a high structural similarity. The conformation type of both structures agrees with those predicted based on qualitative conformational analysis and both structures show a good convergence toward the average torsion angles derived by NMR spectroscopy.     

Classical conditioning after cerebellar lesions in humans.

Explored classical conditioning in human Ss who had lesions in their cerebellar circuitry. Seven patients with damage to cerebellar structures and matched control Ss underwent simple delay tone–airpuff conditioning. Eyelid CR acquisition was severely disrupted in the patient group, whereas autonomic CRs and slow cortical potentials developing between the CS and the unconditioned stimulus/stimuli (UCS) were unaffected. Results are consistent with animal studies and earlier case reports indicating that intact cerebellar structures are necessary for the acquisition of classically conditioned motor responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Microscale elastic strain evolution following damage in Ti-SiC composites

Fiber fractures are crucial in initiating damage zones that ultimately determine the strength and lifetime of fiber-reinforced metal matrix composites. The evolution of damage in a metal matrix composite (MMC) comprised of a row of unidirectional SiC fibers (32 vol pct) surrounded by a Ti matrix was examined, for the first time, using X-ray microdiffraction. Multiple strain maps including both phases were collected in situ under applied tensile stress. The elastic axial strains were then compared to predictions from a modified shear-lag model, which, unlike other shear-lag models, considers the elastic response of both constituents. The strains showed good correlation with the model. The results confirmed, for the first time, both the need and validity of this new model specifically developed for large scale multifracture simulations of MMCs. The results also provided unprecedented insight for the model, revealing the necessity of incorporating such factors as plasticity of the matrix, residual stress in the composite, and selection of the load sharing parameter.     

Handtools and chain saws outproduce hydraulic units

Field tests assessed forest fireline construction capabilities of two power-assisted tooling systems—a chain saw system and a hydraulic power unit system. These were compared with the conventional handtool system as to fireline construction rate, cost, and other considerations. Note: Irene A. Althaus is a Natural Resource Economist assigned to the Pacific Southwest Forest and Range Experiment Station, Forest Service, U. S. Department of Agriculture, Berkeley, California, stationed at Riverside, California. Robert W. Weaver is Fire Research Coordinator with the California Department of Forestry, Sacramento, California.     

Discontinuity and correlation: A reply to Eysenck.

"Our original point was to underscore Eysenck's own carefully stated reservations concerning the application of criterion analysis. We erred in not making this sufficiently clear. Here, we have tried to rectify this error and to amplify a suggestion made implicitly in the earlier paper (see 33: 1700), for an experimental approach to the validation of factor analytic procedures in relation to discrete genotypic determinants of human behavior." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Redesigning structural vibration modes by inverse perturbation subject to minimal change theory

If first-order perturbation theory for the vibration modes of a structure is to be inverted so as to design a new structure having desired changes in vibration modes, it is essential to keep the structural changes as small as possible. This not only helps keep the changes within the approximation of first-order perturbation analysis but also avoids ill-conditioning of the simultaneous equations that must be solved for a new design. The calculus of variations may be used to find the minimal changes, and it specifies a unique set of functions, derived from pairs of vibration modes, that are optimal for expressing the structural changes needed to accomplish a given set of changes in vibration modes. This theory is put into practice for a cantilever plate for which vibration-mode data is obtained by holographic vibration analysis.     

Solution structure and stability of tryptophan-containing nucleopeptide duplexes

Covalently linked peptide-oligonucleotide hybrids were used as models for studying tryptophan-DNA interactions. The structure and stability of several hybrids in which peptides and oligonucleotides are linked through a phosphodiester bond between the hydroxy group of a homoserine (Hse) side chain and the 3'-end of the oligonucleotide, have been studied by both NMR and CD spectroscopy and by restrained molecular dynamics methods. The three-dimensional solution structure of the complex between Ac-Lys-Trp-Lys-Hse(p3'dGCATCG)-Ala-OH (p=phosphate, Ac=acetyl) and its complementary strand 5'dCGTAGC has been determined from a set of 276 experimental NOE distances and 33 dihedral angle constraints. The oligonucleotide structure is a well-defined duplex that belongs to the B-form family of DNA structures. The covalently linked peptide adopts a folded structure in which the tryptophan side chain stacks against the 3'-terminal guanine moiety, which forms a cap at the end of the duplex. This stacking interaction, which resembles other tryptophan-nucleobase interactions observed in some protein-DNA complexes, is not observed in the single-stranded form of Ac-Lys-Trp-Lys-Hse(p3'dGCATCG)-Ala-OH, where the peptide chain is completely disordered. A comparison with the pure DNA duplex, d(5'GCTACG3')-(5'CGTAGC3'), indicates that the interaction between the peptide and the DNA contributes to the stability of the nucleopeptide duplex. The different contributions that stabilize this complex have been evaluated by studying other nucleopeptide compounds with related sequences.     

Mathematical Knowledge Management in HELM

The paper describes the general philosophy and the main architectural and technological solutions adopted in the HELM Project for the management of large repositories of mathematical knowledge. The leitmotiv is the extensive use of XML technology, and the exploitation of information in the Web way, that is without a central authority, with few basic rules, in a scalable, adaptable, and extensible manner.