In the current paper, we propose a new three-dimensional strength criterion for rocks expressed in terms of the first principal stress invariant, I1, and the second and third invariants of the deviatoric stress tensor, J2 and J3. The design of this constitutive model conjugates the characteristics of two of the most well-known and widely used criteria in geotechnical engineering: Hoek-Brown and Matsuoka-Nakai. Its material parameters can be calibrated based on conventional axisymmetric compression and extension tests. Experimental polyaxial test data from a dozen different rock types were used to validate the current criterion.

This paper aims at contributing towards a better understanding of the non-uniform elastoplastic torsion mechanism of I-section beams. The particular case of cantilevers subjected to an end torque is analysed, which constitutes a simple yet interesting problem, since the maximum torque is very close to the so-called Merchant upper bound (MUB), with added independent maximum bishear and Saint-Venant torques. Consequently, it turns out that the maximum torque can be significantly higher than that for uniform plastic torsion. Besides the MUB, several solutions are presented and compared, namely (i) a stress resultant-based solution stemming from the warping beam theory differential equilibrium equation and (ii) solutions obtained with several beam finite elements that allow for a coarse/refined description of warping. It is found that all models are in very close agreement in terms of maximum torque (including the MUB) and stress resultants. However, the beam finite elements that allow for bishear, even with a simplified warping function, are further capable of reproducing quite accurately the stress field, as a comparison with a 3D solid finite element solution shows. Although the paper is primarily concerned with the small displacement case, the influence of considering finite rotations is also addressed.

The cellulosome is an elaborate multi-enzyme structure secreted by many anaerobic microorganisms for the efficient degradation of lignocellulosic substrates. It is composed of multiple catalytic and non-catalytic components that are assembled through high-affinity protein-protein interactions between the enzyme-borne dockerin (Doc) modules and the repeated cohesin (Coh) modules present in primary scaffoldins. In some cellulosomes, primary scaffoldins can interact with adaptor and cell-anchoring scaffoldins to create structures of increasing complexity. The cellulosomal system of the ruminal bacterium, Ruminococcus flavefaciens, is one of the most intricate described to date. An unprecedent number of different Doc specificities results in an elaborate architecture, assembled exclusively through single-binding-mode type-III Coh-Doc interactions. However, a set of type-III Docs exhibits certain features associated with the classic dual-binding mode Coh-Doc interaction. Here, the structure of the adaptor scaffoldin-borne ScaH Doc in complex with the Coh from anchoring scaffoldin ScaE is described. This complex, unlike previously described type-III interactions in R. flavefaciens, was found to interact in a dual-binding mode. The key residues determining Coh recognition were also identified. This information was used to perform structure-informed protein engineering to change the electrostatic profile of the binding surface and to improve the affinity between the two modules. The results show that the nature of the residues in the ligand-binding surface plays a major role in Coh recognition and that Coh-Doc affinity can be manipulated through rational design, a key feature for the creation of designer cellulosomes or other affinity-based technologies using tailored Coh-Doc interactions.

This paper investigates the implementation of the Extended-Matsuoka–Nakai yield criterion on a strict Limit Analysis finite element formulation. The current approach is based on a three-field mixed finite element model and the Alternating Direction Method of Multipliers optimization algorithm. With the support of duality principles two variants are derived, the lower bound and the upper bound element. The main novelty of this work is the development of an efficient iterative predictor–corrector scheme, customized for the Extended-Matsuoka–Nakai. This scheme is an indispensable requirement for this formulation. To conclude four numerical examples are presented to assess the effectiveness and efficiency of the numerical tool.

A numerical implementation of the upper-bound theorem of limit analysis is applied to determine two-dimensional (2D) and three-dimensional (3D) active horizontal earth pressure coefficients considering seismic actions through a horizontal seismic coefficient. Results are obtained for vertical wall, horizontal soil, different friction angles of the soil, soil-to-wall friction ratios, horizontal seismic coefficients and wall width-to-height ratios. The few cases for which 3D active earth pressure coefficients are available in the literature using upper-bound methods were used for comparison with the corresponding earth pressure coefficients obtained in this study. This showed a general improvement of these results, which allows expecting a good accuracy for the set of cases studied. The ratios between the 3D and 2D horizontal active earth pressure coefficients are found to be practically independent of the soil-to-wall friction ratio. An equation is proposed for calculating these ratios. This equation can be easily used in the design of geotechnical structures requiring the determination of 3D active earth pressure coefficients.

The CREMA collaboration is pursuing a measurement of the ground-state hyperfine splitting (HFS) in muonic hydrogen (μp) with 1 ppm accuracy by means of pulsed laser spectroscopy to determine the two-photon-exchange contribution with 2×10-4 relative accuracy. In the proposed experiment, the μp atom undergoes a laser excitation from the singlet hyperfine state to the triplet hyperfine state, then is quenched back to the singlet state by an inelastic collision with a H2 molecule. The resulting increase of kinetic energy after the collisional deexcitation is used as a signature of a successful laser transition between hyperfine states. In this paper, we calculate the combined probability that a μp atom initially in the singlet hyperfine state undergoes a laser excitation to the triplet state followed by a collisional-induced deexcitation back to the singlet state. This combined probability has been computed using the optical Bloch equations including the inelastic and elastic collisions. Omitting the decoherence effects caused by the laser bandwidth and collisions would overestimate the transition probability by more than a factor of two in the experimental conditions. Moreover, we also account for Doppler effects and provide the matrix element, the saturation fluence, the elastic and inelastic collision rates for the singlet and triplet states, and the resonance linewidth. This calculation thus quantifies one of the key unknowns of the HFS experiment, leading to a precise definition of the requirements for the laser system and to an optimization of the hydrogen gas target where μp is formed and the laser spectroscopy will occur.

Here, we describe the first pterosaur remains from Angola, an assemblage of fourteen bones from the Lower Maastrichtian marine deposits of Bentiaba, Namibe Province. One new species is introduced, Epapatelo otyikokolo, gen. et sp. nov., which comprises an articulated partial left humerus and ulna as well as an articulated left ulna and radius (from a second individual). Phylogenetic analysis confirms a non-nyctosaurid pteranodontian attribution for this new taxon and supports a new apomorphy-based clade, Aponyctosauria, which is here defined. Late Cretaceous pteranodontians are rare in Sub-Saharan Africa and throughout the Southern Hemisphere. Preliminary histological analysis also reveals a likely sub-adult age for one of the specimens. This fossil assemblage provides a first glimpse of Angolan pterosaur paleobiodiversity providing further insight into the Gondwanan ecosystems of the Upper Cretaceous.

We exhibit faithful representations of the hypoplactic, stalactic, taiga, sylvester, Baxter and right patience sorting monoids of each finite rank as monoids of upper triangular matrices over any semiring from a large class including the tropical semiring and fields of characteristic 0. By analysing the image of these representations, we show that the variety generated by a single hypoplactic (respectively, stalactic or taiga) monoid of rank at least 2 coincides with the variety generated by the natural numbers together with a fixed finite monoid (respectively, F) and forms a proper subvariety of the variety generated by the plactic monoid of rank 2.

The inexorable increase of energy demand and the efficiency bottleneck of monocrystalline silicon solar cell technology is promoting the research and development of alternative photovoltaic materials. Copper-arsenic-sulfide (CAS) compounds are still rather unexplored in the literature, yet they have been regarded as promising candidates for use as p-type absorber in solar cells, owing to their broad raw material availability, suitable bandgap and high absorption coefficient. Here, a comprehensive study is presented on the structural and optoelectronic properties of CAS thin-films deposited via radio-frequency magnetron co-sputtering, using a commercial Cu target together with a Cu-As-S target with material obtained from local resources, specifically from mines in the Portuguese region of the Iberian Pyrite Belt. Raman and X-ray diffraction analysis confirm that the use of two targets results in films with pronounced stoichiometry gradients, suggesting a transition from amorphous CAS compounds to crystalline djurleite (Cu31S16), with the increasing proximity to the Cu target. Resistivity values from 4.7 mΩ·cm to 17.4 Ω·cm are obtained, being the lowest resistive films, those with pronounced sub-bandgap free-carrier absorption. The bandgap values range from 2.20 to 2.65 eV, indicating promising application as wide-bandgap semiconductors in third-generation (e.g., multi-junction) photovoltaic devices.

This paper presents an experimental study about the fire behaviour of reinforced concrete (RC) slabs strengthened with carbon fibre reinforced polymer (CFRP) strips, applied according to three different techniques: externally bonded reinforcement (EBR); near-surface mounted (NSM), and continuous reinforcement embedded at the ends (CREatE), a new technique that prevents premature CFRP debonding. The main goals of this study were three-fold: to understand and compare the fire behaviour of the strengthening techniques, namely the CREatE technique (yet to be studied); to assess the efficiency of the fire protection schemes (constant thickness vs. increased thickness at the CFRP anchorage zones) in extending the fire resistance of the CFRP systems; and, based on the experimental results and data available in the literature, to propose “critical” temperatures for the fire design of CFRP-strengthened RC members. The results obtained show that: (i) without protection, the CREatE technique presented higher fire resistance than the alternative NSM and EBR techniques (24 min vs. 16 min and 2 min); (ii) with fire protection, regardless of its geometry, the NSM and CREatE techniques presented a similar fire resistance (both above 120 min), higher than the EBR technique (less than 60 min); and (iii) the “critical” temperatures for each technique were defined as 1.0Tg, 2.5Tg and 3.0Tg for EBR, NSM and CREatE, respectively, with Tg being the glass transition temperature of the adhesive, defined based on the onset of the storage modulus curve decay from dynamic mechanical analysis. © 2021 Elsevier Ltd