Equistrong Tower Design

The September 11, 2001 events attracted the attention of civil engineers of the world to the problem of safety of towers and skyscrapers. According to recent studies, the WTC collapse was caused by man-made explosions on a critical floor located much lower than the floors hit by terrorist planes which supports the wide-spread rumor in the U.S. that MASAD agents used the aftermath mess-up after the crush of the planes, put some explosives in the critical floor and detonated them in a while. These or any other possible calamities must be technically treated which can be achieved by drastic increase of safety factor of tower design. In the present paper a new approach to the optimal design of towers is advanced based on the principle of equistrength. Introductive Section 1 provides a short overview of the theory of equistrong structures given in the book by Cherepanov and Ershov (1977). In Section 2, a continuum model is used for the design of equistrong towers. The same problem is studied in Section 3 with an account of the discrete, floor-by-floor structure of equistrong towers. Conclusion emphasizes that the equistrong tower designs allow developers to achieve the maximum possible safety factor. Current designs of skyscrapers including WTC towers are as primitive as the Tower of Babylon

Application of general formulas for the correction of a lattice-translocation defect in crystals of a lentiviral integrase in complex with LEDGF.

The symmetry inherent to many biological macromolecular assemblies has been implicated in a range of crystal pathologies, including lattice-translocation defects (LTDs). Crystals suffering from classic LTDs contain two lattices that are shifted with respect to each other but nonetheless remain within the length of coherent interference. LTD introduces an undesirable intensity modulation into diffraction data, resulting in scrambled or partially scrambled electron densities. In this report, LTD theory is extended and a new general method for determining defect fractions is developed based on the heights of the non-origin peaks observed in native Patterson maps. The application of this method to crystals of lentiviral integrase in complex with its cofactor, where the observed translocation vector does not equal a small integral fraction of a unit-cell edge, is reported and its general application to all classic LTD cases is predicted

Key determinants of target DNA recognition by retroviral intasomes

BACKGROUND: Retroviral integration favors weakly conserved palindrome sequences at the sites of viral DNA joining and generates a short (4–6 bp) duplication of host DNA flanking the provirus. We previously determined two key parameters that underlie the target DNA preference for prototype foamy virus (PFV) and human immunodeficiency virus type 1 (HIV-1) integration: flexible pyrimidine (Y)/purine (R) dinucleotide steps at the centers of the integration sites, and base contacts with specific integrase residues, such as Ala188 in PFV integrase and Ser119 in HIV-1 integrase. Here we examined the dinucleotide preference profiles of a range of retroviruses and correlated these findings with respect to length of target site duplication (TSD). RESULTS: Integration datasets covering six viral genera and the three lengths of TSD were accessed from the literature or generated in this work. All viruses exhibited significant enrichments of flexible YR and/or selection against rigid RY dinucleotide steps at the centers of integration sites, and the magnitude of this enrichment inversely correlated with TSD length. The DNA sequence environments of in vivo-generated HIV-1 and PFV sites were consistent with integration into nucleosomes, however, the local sequence preferences were largely independent of target DNA chromatinization. Integration sites derived from cells infected with the gammaretrovirus reticuloendotheliosis virus strain A (Rev-A), which yields a 5 bp TSD, revealed the targeting of global chromatin features most similar to those of Moloney murine leukemia virus, which yields a 4 bp duplication. In vitro assays revealed that Rev-A integrase interacts with and is catalytically stimulated by cellular bromodomain containing 4 protein. CONCLUSIONS: Retroviral integrases have likely evolved to bend target DNA to fit scissile phosphodiester bonds into two active sites for integration, and viruses that cut target DNA with a 6 bp stagger may not need to bend DNA as sharply as viruses that cleave with 4 bp or 5 bp staggers. For PFV and HIV-1, the selection of signature bases and central flexibility at sites of integration is largely independent of chromatin structure. Furthermore, global Rev-A integration is likely directed to chromatin features by bromodomain and extraterminal domain proteins. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12977-015-0167-3) contains supplementary material, which is available to authorized users

Resonance Chiral Lagrangian analysis of τ−→η(′)π−π0ντ\tau^- \to \eta^{(\prime)} \pi^- \pi^0 \nu_\tau decays

The hadronization structure of $\tau^- \to \eta \pi^- \pi^0 \nu_\tau$ decays is analyzed using Chiral Perturbation Theory with resonances, considering only the contribution of the lightest meson resonances at leading order in the $1/N_C$ expansion. After imposing the asymptotic behavior of vector spectral functions ruled by QCD, unknown effective couplings are determined by fitting the $\tau^- \to \eta \pi^- \pi^0 \nu_\tau$ branching ratio and decay spectrum to recent data. Predictions for the partner decay $\tau^- \to \eta^\prime \pi^- \pi^0 \nu_\tau$ and the low-energy behavior of the cross section $\sigma (e^+e^-\to \eta\pi^+\pi^-)$ are also discussed.Comment: 21 pages, 5 figures, v2: Title changed, references added and rewriting of some sentences. It matches the published version in PR

BIOACTIVITY OF SYNTHETIC HUMIC-LIKE SUBSTANCES ON EARLY STAGES PLANT GROWTH

Biostimulating properties of humic acids and humic-like substances are of significant interest in the field of plant biochemistry, while the nature of their actions at various levels of the substance organization is not sufficiently studied. The use of natural humates as growth regulators is associated with a number of limitations, in particular, their preservation of natural genesis, low solubility in water, a narrow range of active concentrations, insufficient biological activity [1], as well as the labour intensity of substances isolation from natural raw materials, which suggests the relevance of the development of synthetic growth regulating compositions, including based on products of sugar-amine reactions [2]

The Kagome Antiferromagnet with Defects: Satisfaction, Frustration, and Spin Folding in a Random Spin System

It is shown that site disorder induces noncoplanar states, competing with the thermal selection of coplanar states, in the nearest neighbor, classical kagome Heisenberg antiferromagnet (AFM). For weak disorder, it is found that the ground state energy is the sum of energies of separately satisfied triangles of spins. This implies that disorder does not induce conventional spin glass behavior. A transformation is presented, mapping ground state spin configurations onto a folded triangular sheet (a new kind of ``spin origami'') which has conformations similar to those of tethered membranes.Comment: REVTEX, 11 pages + 3 pictures upon reques

Structural features of highly stable reproducible C₆₀ fullerene aqueous colloid solution probed by various techniques

The method of preparation of highly stable reproducible C₆₀ fullerene aqueous colloid solution is described. The structural organization of C₆₀ fullerenes in aqueous solution was studied and analyzed in detail using various techniques such as chemical analysis, UV/VIS spectroscopy, atomic force and scanning tunneling microscopy, dynamic light scattering, and zeta potential method