Stochastic multi-scale models of competition within heterogeneous cellular populations: simulation methods and mean-field analysis

We propose a modelling framework to analyse the stochastic behaviour of heterogeneous, multi-scale cellular populations. We illustrate our methodology with a particular example in which we study a population with an oxygen-regulated proliferation rate. Our formulation is based on an age-dependent stochastic process. Cells within the population are characterised by their age. The age-dependent (oxygen-regulated) birth rate is given by a stochastic model of oxygen-dependent cell cycle progression. We then formulate an age-dependent birth-and-death process, which dictates the time evolution of the cell population. The population is under a feedback loop which controls its steady state size: cells consume oxygen which in turns fuels cell proliferation. We show that our stochastic model of cell cycle progression allows for heterogeneity within the cell population induced by stochastic effects. Such heterogeneous behaviour is reflected in variations in the proliferation rate. Within this set-up, we have established three main results. First, we have shown that the age to the G1/S transition, which essentially determines the birth rate, exhibits a remarkably simple scaling behaviour. This allows for a huge simplification of our numerical methodology. A further result is the observation that heterogeneous populations undergo an internal process of quasi-neutral competition. Finally, we investigated the effects of cell-cycle-phase dependent therapies (such as radiation therapy) on heterogeneous populations. In particular, we have studied the case in which the population contains a quiescent sub-population. Our mean-field analysis and numerical simulations confirm that, if the survival fraction of the therapy is too high, rescue of the quiescent population occurs. This gives rise to emergence of resistance to therapy since the rescued population is less sensitive to therapy

Proposal of a New Parameter for the Weathering Characterization of Carbonate Flysch-Like Rock Masses: The Potential Degradation Index (PDI)

The susceptibility of clay bearing rocks to weathering (erosion and/or differential degradation) is known to influence the stability of heterogeneous slopes. However, not all of these rocks show the same behaviour, as there are considerable differences in the speed and type of weathering observed. As such, it is very important to establish relationships between behaviour quantified in a laboratory environment with that observed in the field. The slake durability test is the laboratory test most commonly used to evaluate the relationship between slaking behaviour and rock durability. However, it has a number of disadvantages; it does not account for changes in shape and size in fragments retained in the 2 mm sieve, nor does its most commonly used index (Id2) accurately reflect weathering behaviour observed in the field. The main aim of this paper is to propose a simple methodology for characterizing the weathering behaviour of carbonate lithologies that outcrop in heterogeneous rock masses (such as Flysch slopes), for use by practitioners. To this end, the Potential Degradation Index (PDI) is proposed. This is calculated using the fragment size distribution curves taken from material retained in the drum after each cycle of the slake durability test. The number of slaking cycles has also been increased to five. Through laboratory testing of 117 samples of carbonate rocks, extracted from strata in selected slopes, 6 different rock types were established based on their slaking behaviour, and corresponding to the different weathering behaviours observed in the field.This work was funded by the University of Alicante under the project GRE14–04, the Ministerio de Economía y Competitividad del Gobierno de España in the framework of the projects TIN2014-55413-C2-2-P and TEC2011-28201-C02-02

Earth Observations for Geohazards: Present and Future Challenges

Earth Observations (EO) encompasses different types of sensors (e.g., Synthetic Aperture Radar, Laser Imaging Detection and Ranging, Optical and multispectral) and platforms (e.g., satellites, aircraft, and Unmanned Aerial Vehicles) and enables us to monitor and model geohazards over regions at different scales in which ground observations may not be possible due to physical and/or political constraints. EO can provide high spatial, temporal and spectral resolution, stereo-mapping and all-weather-imaging capabilities, but not by a single satellite at a time. Improved satellite and sensor technologies, increased frequency of satellite measurements, and easier access and interpretation of EO data have all contributed to the increased demand for satellite EO data. EO, combined with complementary terrestrial observations and with physical models, have been widely used to monitor geohazards, revolutionizing our understanding of how the Earth system works. This Special Issue presents a collection of scientific contributions focusing on innovative EO methods and applications for monitoring and modeling geohazards, consisting of four Sections: (1) earthquake hazards; (2) landslide hazards; (3) land subsidence hazards; and (4) new EO techniques and services.Part of this work was supported by the UK Natural Environmental Research Council (NERC) through the Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET, ref.: come30001) and the LICS and CEDRRIC projects (refs. NE/K010794/1 and NE/N012151/1, respectively), European Space Agency through the ESA-MOST DRAGON-4 projects (ref. 32244) and the Spanish Ministry of Economy and Competitiveness and EU FEDER funds under projects TIN2014-55413- C2-2-P and ESP2013-47780-C2-2-R

An approach for characterising the weathering behaviour of Flysch slopes applied to the carbonatic Flysch of Alicante (Spain)

Various studies indicate that most of the slope instabilities affecting Flysch heterogeneous rock masses are related to differential weathering of the lithologies that make up the slope. Therefore, the weathering characteristics of the intact rock are of great importance for the study of these types of slopes and their associated instability processes. The main aim of this study is to characterise the weathering properties of the different lithologies outcropping in the carbonatic Flysch of Alicante (Spain), in order to understand the effects of environmental weathering on them, following slope excavation. To this end, 151 strata samples obtained from 11 different slopes, 5–40 years old, were studied. The lithologies were identified and their mechanical characteristics obtained using field and laboratory tests. Additionally, the slaking properties of intact rocks were determined, and a classification system proposed based on the first and fifth slake cycles (Id1 and Id5 respectively) and an Index of Weathering (IW5), defined in the study. Information obtained from the laboratory and the field was used to characterise the weathering behaviour of the rocks. Furthermore, the slaking properties determined from laboratory tests were related to the in-situ weathering properties of rocks (i.e., the weathering profile, patterns and length, and weathering rate). The proposed relationship between laboratory test results, field data, and in-situ observations provides a useful tool for predicting the response of slopes to weathering after excavation during the preliminary stages of design.This work was partially funded by the University of Alicante under the projects vigrob-157 uausti10–18, uausti11–11 and gre09–40 and by the Generalitat Valenciana within project gv/2011/044

Upgrading the prediction of jet grouting column diameter using deep learning with an emphasis on high energies

This article proposed a new method to estimate the diameter of jet grouting columns. The method uses the largest data collection of column diameters measured to date and includes a large amount of new data that fills the existing gap of data for high injection energies. The dataset was analysed using a deep neural network that took into account the problem’s key parameters (i.e. type of soil, soil resistance, type of jet and specific energy in the nozzle). As a result, three different neural networks were selected, one for each type of jet, according to the errors and consistency associated with each. Finally, using the trained networks, a number of design charts were developed to determine the diameter of a jet grouting column as a function of the soil properties and the jet system. These charts allow generating an optimal jet grouting design, improving the prediction of the diameter of jet columns especially in the high energy triple fluid.This work was supported by the Spanish Ministry of Economy and Competitiveness, the State Agency of Research and the European Funds for Regional Development under project TEC2017-85244-C2-1-P

Understanding unethical behaviors at the university level: a multiple regression analysis

Unethical behaviors such as corruption pose an important challenge for students, professors, and other university members. We aimed to clarify students' willingness to engage in corruption in a Spanish public university. In all, 3,475 undergraduate, postgraduate, and PhD students completed an online questionnaire assessing four corruption scenarios: favoritism, bribery, fraud, and embezzlement. Multiple regression analysis suggested that justifiability, risk perception, and perceived corruption played a key role in explaining corrupt intention. Behavioral intention to engage in corruption is a complex phenomenon explained by not only peers' behaviors, but also individuals' justifications of their acts and risk perceptions

Assessing water-induced changes in tensile behaviour of porous limestones by means of uniaxial direct-pull test and indirect methods

Understanding the uniaxial tensile behaviour of rocks and its water-induced variation are key issues for designing effective mining and civil engineering structures and for assessing numerous geotechnical hazards. However, these aspects remain poorly analysed because conducting uniaxial direct pull tests is a difficult and time-consuming laboratory task that requires the use of sophisticated equipment and complex rock sample preparation and processing. This work attempts to expand knowledge by determining several tensile properties of three porous limestone lithotypes under dry and water-saturated conditions through two different approaches: by conducting direct tensile tests and by means of indirect methods (i.e. Brazilian and point load tests). The results revealed that water saturation generated important reductions in their uniaxial tensile strength (UTS), tensile elastic modulus (Et), Brazilian tensile strength (BTS) and point load strength index (Is(50)). In addition, their petrological characteristics and mineralogical composition are used to discuss the main causes of the observed tensile softening. Furthermore, highly accurate correlation functions were established between the direct tensile strength parameters (UTS and Et) and the indirect ones (BTS and Is(50)) for the whole set of tested rocks. The proposed relationships are a novel and useful contribution to geomechanics because they enable the estimation of pure tensile parameters using alternative, cheap, rapid and versatile tests.This work was partially supported by the Vicerrectorado de Investigación y Transferencia del Conocimiento of the University of Alicante through the projects UAEEBB2018-09, UAUSTI18-21, UAUSTI20-20 and UAUSTI19-25

Effect of water saturation on strength and deformability of building calcarenite stones: Correlations with their physical properties

Stone construction elements are frequently in moist environments or in direct contact with water. Design and test standards have traditionally ignored the water impact on rock materials. However, several studies have shown that moisture can cause drastic strength reductions and deformability increase in some sedimentary rocks. For that reason, the main objectives of this work are: a) to quantify and understand the influence of water saturation on strength and deformability of four porous calcarenite building stones widely used in SE Spain; b) to establish correlations between physical and mechanical properties of these rock materials in dry and saturated states and c) to compare the results with previous findings. The results showed a very significant reduction of mechanical properties such as unconfined compressive strength, Young’s modulus and point load strength index when these stones undergo saturated. In addition, significant correlations between physical properties (density, porosity, P wave velocity and dynamic elastic parameters) and the mentioned mechanical properties were established in dry and saturated conditions. Additionally, relationships among the mechanical properties of stones in both states are also proposed.This work was supported by the Vicerrectorado de Investigación y Transferencia del Conocimiento of the University of Alicante through Predoctoral grant FPUUA53-2018 and the projects UAUSTI18-21 and UAEEBB2018-09

Advances in the understanding of the role of degree of saturation and water distribution in mechanical behaviour of calcarenites using magnetic resonance imaging technique

A thorough knowledge of the variations of mechanical properties of rock materials with their water content is essential for evaluating the structural behaviour and durability of stone constructions exposed to different moist environments during their lifetime and for solving a broad range of rock mechanics issues. In this study, the effect of degree of saturation (Sr) and water distribution inside pore network on mechanical parameters such as Uniaxial Compressive Strength, Young’s modulus, Brazilian Tensile Strength and Point Load Strength Index was assessed for three varieties of a calcarenite. To this aim, the corresponding mechanical tests and Magnetic Resonance Imaging technique were applied during different time intervals in specimens prepared with different Sr values through two different wetting procedures: (1) the oven drying of saturated samples and (2) the water immersion of dry samples. In general terms, the results showed that for small Sr values (≤50%) the specimens wetted using the drying process exhibit greater mechanical properties reductions than those moistened through the immersion process while for higher Sr values (>50%) the decreases are quite similar for both wetting procedures. As a consequence, different negative exponential functions can be used to describe the relationship between water content and mechanical parameters of calcarenites depending on the wetting procedure used. These results can be explained by the different water distributions inside the partial-saturated specimens and the main involved water-weakening mechanisms. Additionally, slightly different correlation functions between the mechanical parameters were established for specimens moistened using each of the wetting processes.This research was supported by the Vice-rector of Research and Knowledge Transfer of the University of Alicante through predoctoral grant FPUUA53-2018 and projects UAUSTI18-21, UAUSTI19-25, UAUSTI20-20, UAEEBB2018-09 and GRE18-15 and by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project TEC2017-85244-C2-1-P

Tiburzio Spannocchi’s project for the fortifications of Fuenterrabía in 1580

Fuenterrabía (Hondarribia) is a town located on the Franco-Spanish border. Between the 16th and 19th centuries it was considered to be one of the most outstanding strongholds in the Basque Country due to its strategic position. The bastion system of fortification was extremely prevalent in this stronghold. It was one of the first Spanish towns to adopt the incipient Renaissance designs of the bastion. The military engineers subsequently carried out continuous fortification projects that enabled the structure to withstand the advances being made in artillery and siege tactics. After the construction of the citadel of Pamplona had begun in 1571, following the design of the prestigious military engineer, Jacobo Palear Fratín and being revised by Viceroy Vespasiano Gonzaga, the aforementioned engineer undertook an ambitious project commissioned by Felipe II to modernise the fortifications of Fuenterrabía. Neither the plans nor the report of this project have been conserved, but in the year 2000, César Fernández Antuña published the report written by Spannocchi on the state of the fortifications of Fuenterrabía when he arrived to the Spanish peninsula, discovered in the Archivo Histórico Provincial de Zaragoza. This document conducts an in-depth analysis of Spannocchi’s project and how it was related to Fratín’s previous project. It concludes that this project encountered problems in updating the new bastions at the end of the 16th century, and identifies the factors which prevented the stronghold from being extended as was the case in Pamplona after Fratín’s project