In this Letter we consider a general quadratic parity-preserving theory for a general flat connection. Imposing a local symmetry under the general linear group singles out the general teleparallel ...equivalent of General Relativity carrying both torsion and non-metricity. We provide a detailed discussion on the teleparallel equivalents of General Relativity and how the two known equivalents, formulated on Weitzenböck and symmetric teleparallel geometries respectively, can be interpreted as two gauge-fixed versions of the general teleparallel equivalent. We then explore the viability of the general quadratic theory by studying the spectrum around Minkowski. The linear theory generally contains two symmetric rank-2 fields plus a 2-form and, consequently, extra gauge symmetries are required to obtain potentially viable theories.
•The thermal behavior of synthetic hydrocalumite (Ca2Al(OH)6Cl•2H2O) was studied.•The decomposition process of hydrocalumite is complex.•Formation of mayenite (Ca12Al14O33), CaOHCl and CaO was ...observed.•Formation of CaCl2 suggests decomposition to CaO and CaCl2, without emission of HCl.
Hydrocalumite (Ca2Al(OH)6Cl·2H2O) samples were prepared by the coprecipitation method, using Al3+ obtained from an aluminum slag, extracted in NaOH solutions and purified removing silica by precipitation with HCl. Hydrocalumite aging was assisted by microwave irradiation, and carried out under different temperatures. Very pure hydrocalumite was obtained under certain conditions, but samples impurified with katoite (Ca3Al2(OH)12) and calcite (CaCO3) were obtained in other cases. The thermal decomposition of hydrocalumite is complex and is not completely elucidated, compounds such as Ca12Al14O33 (mayenite), Ca(OH)Cl and CaO have been proposed. The thermal characterization of this system was studied, also considering samples impurified with katoite and calcite, as a valuable and rapid method for identifying these phases.
Display omitted
In this paper we explore generalizations of metric structures of the gravitational wave type to geometries containing an independent connection. The aim is simply to establish a new category of ...connections compatible, according to some criteria, to the known metric structures for gravitational waves and, additionally, provide some properties that can be useful for the search of solutions of this kind in different theories.
Trackways and tracemakers preserved together in the fossil record are rare. However, the co-occurrence of a drag mark, together with the dead animal that produced it, is exceptional. Here, we ...describe an 8.5 m long ammonite drag mark complete with the preserved ammonite shell (Subplanites rueppellianus) at its end. Previously recorded examples preserve ammonites with drag marks of < 1 m. The specimen was recovered from a quarry near Solnhofen, southern Germany. The drag mark consists of continuous parallel ridges and furrows produced by the ribs of the ammonite shell as it drifted just above the sediment surface, and does not reflect behaviour of the living animal.
Resilience has gained prominence in many fields of research and practice globally. In the water sector, efforts to build resilience have become a central feature of water governance. However, current ...scholarships frame resilience interventions in socio-ecological systems through adaptive governance. There is limited knowledge about what the adaptive governance agenda means as a technical approach to water governance in achieving resilience. This paper clarifies these linkages through a review of the literature. It identifies key attributes of adaptive governance for building resilience of socio-ecological systems and suggests the benefits of better articulating 'good governance' with 'adaptive governance' to foster water resilience.
Pointed arches are important architectural elements of both western and eastern historical built heritage. In this paper, the effects that different geometrical (slenderness and sharpness) and ...mechanical (friction and cohesion) parameters have on the in-plane structural response of masonry pointed arches are investigated through the implementation of an upper bound limit analysis approach capable of representing sliding between rigid blocks. Results, in terms of collapse multipliers are presented and quantitatively analyzed following a systematic statistical approach, whereas collapse mechanisms are qualitatively explored and three different outcomes are found; pure rotation, pure sliding and mixed collapse mechanisms. It is concluded that the capacity of the numerical approach implemented to reproduce sliding between blocks plays a major role in the better understanding of masonry pointed arches structural response.
•Collapse behavior of masonry arches accounting for rotation and sliding mechanisms.•Systematic statistical analysis on the in-plane response of pointed arches.•Pure rotation, pure sliding and combined collapse mechanisms were observed.•Prominence of sliding mechanism in pointed arches with significant thickness.•Larger concentrated loads are sustained closer to the pointed arches keystone.
The use of composite on the strengthening and retrofitting of masonry structures over the past few decades has gained considerable importance. In this paper, the influence of partial reinforcement on ...the structural response of masonry arches is studied. An upper bound limit analysis numerical approach has been implemented to compute the collapse multipliers and reproduce the collapse mechanisms of two different study cases by increasing the cohesion value of the reinforced inter-block joints. The results thus obtained, have been compared to numerical simulation outcomes reported by other authors on the literature. The numerical approach adopted on this work, which requires few input parameters, is relatively fast in comparison to alternative numerical simulation methods, provided good agreement in terms of collapse loads and mechanisms.
•Collapse behaviour of masonry arches subject to horizontal live loads.•Local reinforcement of masonry arches with different shapes.•Impact of the infill consideration for the reinforced and unreinforced scenarios.
In this paper we prove that the k-th order metric-affine Lovelock Lagrangian is not a total derivative in the critical dimension n=2k in the presence of non-trivial non-metricity. We use a bottom-up ...approach, starting with the study of the simplest cases, Einstein-Palatini in two dimensions and Gauss-Bonnet-Palatini in four dimensions, and focus then on the critical Lovelock Lagrangian of arbitrary order. The two-dimensional Einstein-Palatini case is solved completely and the most general solution is provided. For the Gauss-Bonnet case, we first give a particular configuration that violates at least one of the equations of motion and then show explicitly that the theory is not a pure boundary term. Finally, we make a similar analysis for the k-th order critical Lovelock Lagrangian, proving that the equation of the coframe is identically satisfied, while the one of the connection only holds for some configurations. In addition to this, we provide some families of non-trivial solutions.
PDF
