Rock failure under shear loading conditions controls earthquake and faulting phenomena. We study the dynamics of microscale damage precursory to shear faulting in a quartz‐monzonite rock representative of crystalline rocks of the continental crust. Using a triaxial rig that is transparent to X‐rays, we image the mechanical evolution of centimeter‐size core samples by in situ synchrotron microtomography with a resolution of 6.5 μm. Time‐lapse three‐dimensional images of the samples inside the rig provide a unique data set of microstructural evolution toward faulting. Above a yield point there is a gradual weakening during which microfractures nucleate and grow until this damage span the whole sample. This leads to shear faults oriented about 30° to the main compressive stress in agreement with Anderson's theory and macroscopic failure. The microfractures can be extracted from the three‐dimensional images, and their dynamics and morphology (i.e., number, volume, orientation, shape, and largest cluster) are quantified as a function of increasing stress toward failure. The experimental data show for the first time that the total volume of microfractures, the rate of damage growth, and the size of the largest microfracture all increase and diverge when approaching faulting. The average flatness of the microfractures (i.e., the ratio between the second and third eigenvalues of their covariance matrix) shows a significant decrease near failure. The precursors to faulting developing in the future faulting zone are controlled by the evolving microfracture population. Their divergent dynamics toward failure is reminiscent of a dynamical critical transition.

We analyse the statistical distribution function for the height fluctuations of brittle fracture surfaces using extensive experimental data sampled on widely different materials and geometries. We compare a direct measurement of the distribution to a new analysis based on the structure functions. For length scales δ larger than a characteristic scale δ * , we find that the distribution of the height increments ∆h = h(x + δ) − h(x) is Gaussian. Self-affinity enters through the scaling of the standard deviation σ, which is proportional to δ ζ with a unique roughness exponent. Below the scale δ * we observe an effective multi-affine behavior of the height fluctuations and a deviation from a Gaussian distribution which is related to the discreteness of the measurement or of the material.

We propose a many-particle-inspired theory for granular outflows from a hopper and for the escape dynamics through a bottleneck based on a continuity equation in polar coordinates. If the inflow is below the maximum outflow, we find an asymptotic stationary solution. If the inflow is above this value, we observe queue formation, which can be described by a shock wave equation. We also address the experimental observation of intermittent outflows, taking into account the lack of space in the merging zone by a minimum function and coordination problems by a stochastic variable. This results in avalanches of different sizes even if friction, force networks, inelastic collapse, or delay-induced stop-and-go waves are not assumed. Our intermittent flows result from a random alternation between particle propagation and gap propagation. Erratic flows in congested merging zones of vehicle traffic may be explained in a similar way. Driven granular media display a rich spectrum of pattern formation phenomena. This includes collective oscillating states, convection patterns, the spontaneous segregation of different granular materials, and the formation of avalanches due to self-organized criticality [1]. Here, we will focus on jamming and clogging phenomena [2] related to arching [3] and on intermittent outflows through hoppers [4,5]. Similar phenomena are known from dense pedestrian crowds [6]. The escape dynamics of individuals from a room has been intensively studied, showing that in crowd stampedes, rooms are emptied in an irregular, strongly intermittent fashion [7]. This effect has been discovered in simulations performed with the social and the centrifugal force model [7,8], with cellular automata and lattice gas automata [9], and in a mean-field model [10]. It has also been experimentally confirmed [6,11]. However, analytical models of escape dynamics and granular bottleneck flows are lacking.In this Letter we will formulate such a model. Our goal is to gain a better understanding of (i) the resulting density profiles and (ii) the irregular outflows at bottlenecks. The model not only addresses the distribution of the avalanche sizes in the outflow from a bottleneck, but it also offers a possible explanation of the long-standing problem of perturbations forming in merging zones of freeway traffic flows [12,13], which are characterized by erratic, forward or backward moving shock waves [12]. It is believed that these can trigger stop-and-go waves in traffic flows [12,14]. Similar findings have been made in overcrowded pedestrian flows [11] and expected for merging flows in urban traffic and production networks.In all these cases, the competition of too many entities for little space leads to coordination problems. We are therefore looking for a minimal, common model capturing this feature. Hence, we will first abstract from specific system features such as the non-Newtonian character of real granular flows, nonslip boundary conditions, dissipative interactions, or force networks in quasistatic granular flows [15,16], ...

Basic personality traits are typically assessed through questionnaires. Here we consider phone-based metrics as a way to asses personality traits. We use data from smartphones with custom data-collection software distributed to 730 individuals. The data includes information about location, physical motion, face-to-face contacts, online social network friends, text messages and calls. The data is further complemented by questionnaire-based data on basic personality traits. From the phone-based metrics, we define a set of behavioural variables, which we use in a prediction of basic personality traits. We find that predominantly, the Big Five personality traits extraversion and, to some degree, neuroticism are strongly expressed in our data. As an alternative to the Big Five, we investigate whether other linear combinations of the 44 questions underlying the Big Five Inventory are more predictable. In a tertile classification problem, basic dimensionality reduction techniques, such as independent component analysis, increase the predictability relative to the baseline from 11% to 23%. Finally, from a supervised linear classifier, we were able to further improve this predictability to 33%. In all cases, the most predictable projections had an overweight of the questions related to extraversion and neuroticism. In addition, our findings indicate that the score system underlying the Big Five Inventory disregards a part of the information available in the 44 questions.

Most rocks are formed at pressures and temperatures exceeding those at the Earth's surface (Figure 1.1). When such rocks are brought to the surface through uplifting process, they become thermodynamically unstable with respect to the prevailing conditions. Weathering refers to the in situ breakdown and transformation of rocks to equilibrate with the conditions at or near the surface of the Earth. The principle agent of rock weathering is water, and the driving force for weathering is solar energy. Weathering is an important part of the rock cycle together with erosion, which are the processes by which rock debris is transported from the weathering site by agents such as ice, water and wind. When weathering products are transported by erosion and subsequently deposited on riverbeds, lakes and oceans, they are called sediment, which may transform to sedimentary rock through burial and cementation. Even slight variations in rock properties and climatic conditions may lead to significant differences in weathering rates. This leads to the formation of topological features, both on small and large scales, and thereby directly affects the shape of the world we live in. When organic matter becomes part of the sediment and is transformed into sedimentary rock, nutrients and building-blocks which are essential for life becomes locked in the rock cycle. Weathering is the process by which these nutrients are released back into the biosphere, and it is therefore critical for the existence of life on the planet [1]. Weathering also affects the long term global climate because precipitation of carbonates during weathering binds CO 2 from the atmosphere [1, 2]. On shorter timescales, weathering has a direct effect on the human society through its destructive effect on concrete and building stones [3]. Weathering also produces some stunningly beautiful and intriguing patterns that we observe around us (e.g. Figure 1.2c-e). Patterns trigger our fracturing Mechanical dissolution Chemical growth increased reactive surface area increased transport changed stress state effect on dissolution and growth rates Figure 1.3: Feedback between mechanical and chemical weathering processes. Fracturing may increase the reactive surface area and transport of reactive species, thereby accelerating the chemical processes. Dissolution and growth may change the stress state of the rock in such a way that fractures form. There is also a feedback between the state of stress of a solid surface and the dissolution or growth of that surface.

Ecological systems comprise an astonishing diversity of species that cooperate or compete with each other forming complex mutual dependencies. The minimum requirements to maintain a large species diversity on long time scales are in general unknown. Using lichen communities as an example, we propose a model for the evolution of mutually excluding organisms that compete for space. We suggest that chain-like or cyclic invasions involving three or more species open for creation of spatially separated sub-populations that subsequently can lead to increased diversity. In contrast to its non-spatial counterpart, our model predicts robust co-existence of a large number of species, in accordance with observations on lichen growth. It is demonstrated that large species diversity can be obtained on evolutionary timescales, provided that interactions between species have spatial constraints. In particular, a phase transition to a sustainable state of high diversity is identified.Introduction.-Interactions between biological species may well be as old as life itself [1-3] with competition and predation as major determinants for species diversity [4,5]. Competitive exclusion [6,7] has been suggested to reduce ecosystem diversity when several species compete for the same resources. Real ecosystems, on the other hand, consist of multiple species and have a robustness that may even increase with diversity [8,9]. To obtain robustness of ecosystem diversity in theoretical models one needs first of all to limit the exponential growth by assuming a maximum carrying capacity for the population of each species [10]. Extreme version of such models [11,12] indeed predicts a sustainable but fragile coexistence of multiple species.A more robust way to maintain high diversity is to include space [13][14][15][16][17][18] e.g. in combination with hypercycles [19] or predator-prey cycles [20][21][22][23]. Studying ecosystems in marine hard-substrate environments Jackson & Buss [24] suggested that non-transitive allelopathic relationships between species could maintain species diversity on a longer timescale than pure hierarchical predation relationships. This was confirmed in a model on two-dimensional lattice where sessile species compete for space [25,26]. As in the "Buss" model [25,26] we consider a 2-dimensional lattice where the competition for resources is a zero sum game about available space. In our model, however, the focus is on the dynamic balance between an introduction of new species and exclusion of older species. With this complementary model we, for the first time show that: a) There is a sharp transition from multiple to single species as the number of interactions is increased. b) Both cycles and chain-like (hierarchical) relationships lead to spatial fragmentation of species population thus creating isolated niches for new species and increased diversity.The model is inspired by the spatial dynamics of lichen communities. Lichens have existed for as long as ∼600 million years [27] and are organisms consisting of fungi and ...

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In healthy blood vessels with a laminar blood flow, the endothelial cell division rate is low, only sufficient to replace apoptotic cells. The division rate significantly increases during embryonic development and under halted or turbulent flow. Cells in barrier tissue are connected and their motility is highly correlated. Here we investigate the long-range dynamics induced by cell division in an endothelial monolayer under non-flow conditions, mimicking the conditions during vessel formation or around blood clots. Cell divisions induce long-range, well-ordered vortex patterns extending several cell diameters away from the division site, in spite of the system’s low Reynolds number. Our experimental results are reproduced by a hydrodynamic continuum model simulating division as a local pressure increase corresponding to a local tension decrease. Such long-range physical communication may be crucial for embryonic development and for healing tissue, for instance around blood clots.