Does Quartessence Ease Tensions?

Tensions between cosmic microwave background observations and the growth of the large-scale structure inferred from late-time probes pose a serious challenge to the concordance $\Lambda$CDM cosmological model. State-of-the-art data from the Planck satellite predicts a higher rate of structure growth than what preferred by low-redshift observables. Such tension has hitherto eluded conclusive explanations in terms of straightforward modifications to $\Lambda$CDM, e.g. the inclusion of massive neutrinos or a dynamical dark energy component. Here, we investigate models of 'quartessence' -- a single dark component mimicking both dark matter and dark energy -- whose non-vanishing sound speed inhibits structure growth at late times on scales smaller than its corresponding Jeans' length. In principle, this could reconcile high- and low-redshift observations. We put this hypothesis to test against temperature and polarisation spectra from the latest Planck release, SDSS DR12 measurements of baryon acoustic oscillations and redshift-space distortions, and cosmic shear correlation functions from KiDS. This the first time that any specific model of quartessence is applied to actual data. We show that, if we naively apply $\Lambda$CDM nonlinear prescription to quartessence, the combined data sets allow for tight constraints on the model parameters. Apparently, quartessence alleviates the tension between the total matter fraction and late-time structure clustering, although in fact the tension is transferred from the latter to the quartessence sound speed parameter. However, we found that this strongly depends upon information from nonlinear scales. Indeed, if we relax this assumption, quartessence models appear still viable. For this reason, we argue that the nonlinear behaviour of quartessence deserves further investigation and may lead to a deeper understanding of the physics of the dark Universe.Comment: 8 pages, 6 figures, 1 table; matching published versio

Mechanical behaviour of conditioned material for EPBS tunnelling

The rapid growth of the development of the cities all over the World, brought the necessity of bringing deeper the services and all the activities which are not strictly necessary above the ground like houses. This sudden demand of new tunnels obliged to push the excavation industry towards mechanized methods which allow to avoid settlements on the surface, where other structures and infrastructures are located. In this context EPB shield machines play a crucial role, as with a good control of this technology, a tunnel can be excavated basically everywhere, also below important structures. This implies the perfect knowledge of the geology but especially requires a precise study of the soil conditioning, in order to allow an effective counterpressure to the front. The development of preliminary laboratory tests, which means before the tunnel project starts, allows to assess the best conditioning set for each lithotype which can be encountered during the excavation. These tests are performed at room pressure, nevertheless recently the main goal is to study the conditioned mass at pressure conditions which can be found in an excavating chamber, which might influence the state of the mass itself. The aim of this work is the development of new techniques which can exactly reproduce this state, through the use and modification of techniques proper of the geotechnical engineering (shear and triaxial tests) and the design of new devices able to underline these aspects in detail. The new approach includes, as well as the consideration of a certain pressure condition, also the definition of an undrained condition used for testing, which allows to keep the conditioned mass in its original state for its study

Uso delle gallerie per la stabilizzione di versanti in frana

L'uso del sottosuolo per la gestione idrogeologica del territorio e per la bonifica delle frane è una so-luzione efficace ed ampiamente utilizzata nel mondo. Nel lavoro dopo un inquadramento generale dell'argomento vengono illustrati alcuni casi studio di particolare interesse

Willingness towards cognitive engagement: a preliminary study based on a behavioural entropy approach

Faced with a novel task some people enthusiastically embark in it and work with determination, while others soon lose interest and progressively reduce their efforts. Although cognitive neuroscience has explored the behavioural and neural features of apathy, the why’s and how’s of positive engagement are only starting to be understood. Stemming from the observation that the left hemisphere is commonly associated to a proactive (‘do something’) disposition, we run a preliminary study exploring the possibility that individual variability in eagerness to engage in cognitive tasks could reflect a preferred left- or right-hemisphere functioning mode. We adapted a task based on response-independent reinforcement and used entropy to characterize the degree of involvement, diversification, and predictability of responses. Entropy was higher in women, who were overall more active, less dependent on instructions, and never reduced their engagement during the task. Conversely, men showed lower entropy, took longer pauses, and became significantly less active by the end of the allotted time, renewing their efforts mainly in response to negative incentives. These findings are discussed in the light of neurobiological data on gender differences in behaviour

Willingness towards cognitive engagement: a preliminary study based on a behavioural entropy approach

Faced with a novel task some people enthusiastically embark in it and work with determination, while others soon lose interest and progressively reduce their efforts. Although cognitive neuroscience has explored the behavioural and neural features of apathy, the why’s and how’s of positive engagement are only starting to be understood. Stemming from the observation that the left hemisphere is commonly associated to a proactive (‘do something’) disposition, we run a preliminary study exploring the possibility that individual variability in eagerness to engage in cognitive tasks could reflect a preferred left- or right-hemisphere functioning mode. We adapted a task based on response-independent reinforcement and used entropy to characterize the degree of involvement, diversification, and predictability of responses. Entropy was higher in women, who were overall more active, less dependent on instructions, and never reduced their engagement during the task. Conversely, men showed lower entropy, took longer pauses, and became significantly less active by the end of the allotted time, renewing their efforts mainly in response to negative incentives. These findings are discussed in the light of neurobiological data on gender differences in behaviour

Ultrasonic measurements for assessing the elastic parameters of two-component grout used in full-face mechanized tunnelling

The use of shield machines and instantaneous segment linings for tunnel construction is one of the most used tunnelling methods today. Despite a large number of applications in different tunnelling projects all around the world, knowledge of the behaviour of two-component grout is quite limited, mainly due to the fast hardening process that inhibits using the classic approach for concrete characterization. In the present work, an innovative approach based on ultrasonic measurements is introduced, aimed to characterize the elastic properties of this innovative backfilling material. Specifically, ultrasonic pulse velocity was applied to two-component grout samples to describe the interesting and fast evolution of the material from the mixing phase until 6 months of curing using geophysics parameters. The dynamic Young’s modulus (E) and the dynamic shear modulus (G) exhibited a clear increasing trend, starting from values of a few tens of MPa to final values equal to 1000 MPa and 340 MPa, respectively. The Poisson’s ratio (ν), close to the value of incompressible materials (0.5) at the short curing time, exhibited a decreasing trend, reaching roughly 0.445 after 3 months of curing

Study of the shear strength evolution over time of two-component backfilling grout in shield tunnelling

The two-component backfilling system is the most commonly used method to fill the annular void created during the advancement of shield machines. This unavoidable void, strictly linked to the technology of shield machines, must be filled continuously in order to avoid mostly surface displacements and lining movements. Today, this technology is the most frequently used due to operative and technical advantages, which lead to economic savings. However, despite intensive use of this backfilling technology, very little information is currently available concerning the evolution of the material in function of the curing time. Historically, the uniaxial compressive strength has been used as the main parameter for testing the compliance of a certain grout with the site-specific technical requirements, but nowadays shear strength is also starting to be considered by designers even if this topic has never been investigated. In this work, a laboratory test campaign focused on shear strength and its evolution in function of curing was performed. These tests put alight the fast mechanical growing of the twocomponent grout from the shear strength point of view and it should be remarked that at the current state of research there are no investigations concerning the shear strength in the context of a drainage approach. Both short and long curing times were investigated according to the direct shear test, performed under drained conditions. The Mohr-Coulomb failure envelope model was selected for the study and its widening in time highlights the peculiarity of this technology. Starting from a liquid phase at t0, values of cohesion (c') and friction angle (phi') grow in function of curing, reaching 126 kPa and 22 degrees at 3 h and exceeding 270 kPa and 40 degrees at 28 days

Maintenance and risk management of rockfall protection net fences through numerical study of deteriorations

Rockfall protection net fences are key protection systems in mountainous areas worldwide to ensure the safety of infrastructures, roads and urban areas against rockfall. Management of the maintenance of rockfall protection net fences is fundamental for public administrations in order to guarantee risk mitigation. This paper deals with the assessment of the installation problems and deterioration of rockfall protection net fences, using numerical modelling in order to evaluate the influence of these issues on their behaviour. A percentage of the residual efficiency is assessed as a useful tool for risk analysis and maintenance planning

Evaluation of the Geo-Mechanical Properties Property Recovery in Time of Conditioned Soil for EPB-TBM Tunneling

The soil conditioning is a process of fundamental importance during the excavation of tunnels with Earth Pressure Balance full face machine. The soil conditioning is achieved through the addition of foam at the excavation face and in the bulk chamber that modifies the natural soil properties from solid-like to fluid-like with a pulpy behavior. Clearly, a material with a pulpy or fluid-like consistency is not suitable for the construction of embankments of landfill or for other civil purposes. It is therefore important to have a procedure able to identify how long it is necessary before the conditioned soil recovers its geo-mechanical properties, since this knowledge is needed at the design stages from a logistic point of view. The paper proposes and discusses a procedure to find out whether and when the conditioned soil gets back to its original properties. The procedure foresees direct shear tests, vane tests, Proctor tests, and rotational mixer tests at different time schedules from the production of the conditioned soil in the laboratory. The conditioned soil samples have been cured in a controlled environment up to 60 days from the conditioning. Thanks to these tests, it is possible to assess if and when the soil recovers its natural behavior or if a permanent alteration is induced. The proposed procedure has been applied to a standard alluvial soil showing that most of the original properties of the soil are recovered already after seven days from the conditioning. The carried-out tests have shown that the procedure is feasible and easy to apply