Tripeptide loop closure: a detailed study of reconstructions based on Ramachandran distributions

Tripeptide loop closure (TLC) is a standard procedure to reconstruct protein backbone conformations, by solving a zero dimensional polynomial system yielding up to 16 solutions. In this work, we first show that multiprecision is required in a TLC solver to guarantee the existence and the accuracy of solutions. We then compare solutions yielded by the TLC solver against tripeptides from the Protein Data Bank. We show that these solutions are geometrically diverse (up to 3 Angstroms RMSD with respect to the data), and sound in terms of potential energy. Finally, we compare Ramachandran distributions of data and reconstructions for the three amino acids. The distribution of reconstructions in the second angular space (φ2 , ψ2) stands out, with a rather uniform distribution leaving a central void. We anticipate that these insights, coupled to our robust implementation in the Structural Bioinformatics Library (https://sbl.inria.fr/doc/Tripeptide_loop_closure-user-manual.html), will boost the interest of TLC for structural modeling in general, and the generation of conformations of flexible loops in particular.

The response of zircon to the extreme pressures and temperatures of a lightning strike

Hypervelocity impacts can produce features in zircon that are not normally produced by endogenic processes. However, lightning can also induce extreme pressure–temperature excursions, and its effect on zircon has not been studied. With the aim to recognise features that form in response to extreme pressure–temperature excursions but are not unique to hypervelocity impacts, we imaged and undertook microstructural characterization of zircon in a fulgurite (a tubular body of glass and fused clasts that formed in response to a lightning strike). We document zircon with granular ZrO2 and rims of vermicular ZrO2, features which vary in abundance with increasing distance from the fulgurite’s central void. This indicates that these features formed in response to the lightning strike. Zircon dissociation to ZrO2 and SiO2 is a high-temperature, relatively low-pressure phenomenon, consistent with previous suggestions that lightning strikes involve extreme temperatures as well as pressures greater than those usually generated in Earth’s crust but rarely > 10 GPa. The rims of monoclinic ZrO2 record crystallographic evidence for precursor cubic ZrO2, demonstrating that cubic ZrO2 is not unique to hypervelocity impacts. Given the likelihood that this fulgurite experienced pressures of, at most, a few GPa, evidence for cubic ZrO2 indicates peak temperatures > 2000 °C.

The Possibility of Teaching Chinese Students of Architecture to Write (A House)

Writing, as the projection of a building, is integral to the discipline of architecture. In the specification, the architect describes the edifice from inside out so that it may materialise in accordance with the plan drawn up. There are other kinds of writing too, if not the writing of a house itself – a paper house built from words without even folding the surface of its flat ground. I propose to write this house by moving four times around my chosen site – an A4 sheet of white paper. Four times because tracing the contours of this field means turning a corner four times. Two times two, because when turning the paper itself, the writing splits across one side and the other. One times four, because writing a hole in the centre allows me to peep through this central void to charge the whole structure from within. And if, by then, the boundaryofthesitealsosplits,thenaspacewillemergebetweenitsdoublelinesandI willhavearrivedinanewlocation–possiblyanewkindofhouse.CanIwritethishouse?

Annular Post-Compression by FRP inside Mortar Joints and Vertical Post-Compression by Stainless Steel, for Seismic and Wind Retrofitting of Historical Masonry Chimney

This paper shows the efficiency of the vertical and annular post-compression for wind and seismic structural behavior improvement of slender masonry chimney. For this aim a case study approach regarding an old masonry chimney is used. The paper shows the safety analysis and the safety improvement obtained applying at the same time a vertical and an annular masonry post-compression. The vertical post-compression is obtained through the post-tensioning of twenty-four vertical stainless-steel thin bars. These bars are connected to the chimney masonry only at the basement and at the top. They are placed inside the central void and horizontally distributed along a circumference near the inside face of the masonry, but without to touch it. The annular post-compression is obtained post-tensioning forty-five annular aramidica “not twisted” cables, placed and glued (after the post-tensioning) inside horizontal mortar joints of the more external masonry brick layer.

On Transcendental Absenting

This chapter posits a certain “void” upon which the few scraps of philosophical discussion of dance are scattered. It argues that this central void operates like a caesura, determining a “before” and an “after” This void implicates an absence—and the absence of dance from philosophy coincided precisely with the birth of aesthetics. There was thus a moment when a new kind of discourse about art and the beautiful was established, when a new discipline was formed which reorganized the disparate empirical realities of practices and works according to the architectonics of the concept. It was also the moment when dance was excluded, positioned beyond classification and ultimately marginalized as an art form.