Compaction behaviour of clay

This paper presents an experimental study of the compaction behaviour of non-active clay. One-dimensional static compaction tests were carried out at high and medium water content with matric suction monitoring using Trento high-capacity tensiometers. At lower water contents, a transistor psychrometer was used to measure post-compaction suction. Samples were compacted on the dry side of optimum to cover a wide range of compaction water contents and vertical stresses. Three water content regions were identified in the compaction plane depending on whether post-compaction suction increased, decreased or remained constant as the degree of saturation was increased at constant water content. Hydraulic paths of specimens subjected to loading-unloading cycles at constant water content have clearly shown that post-compaction suction may increase as the degree of saturation increases. This non-intuitive behaviour was demonstrated to be associated with the coupling between mechanical and water retention behaviour. To this end, a coupled mechanical water retention model was formulated. Irreversible one-dimensional mechanical paths were modelled by a boundary surface in the space average skeleton vertical stress, modified suction and void ratio. Irreversible hydraulic 'wetting' paths were modelled by a boundary surface in the space suction, degree of saturation, and void ratio. This study was completed by investigating the pore size distribution of compacted samples through MIP tests

Flavour Condensates in Brane Models and Dark Energy

In the context of a microscopic model of string-inspired foam, in which foamy structures are provided by brany point-like defects (D-particles) in space-time, we discuss flavour mixing as a result of flavour non-preserving interactions of (low-energy) fermionic stringy matter excitations with the defects. Such interactions involve splitting and capture of the matter string state by the defect, and subsequent re-emission. Quantum fluctuations of the D-particles induce a non-trivial space-time background; in some circumstances this could be akin to a cosmological Friedman-Robertson Walker expanding-Universe, with weak (but non-zero) particle production. Furthermore the D-particle medium can induce an MSW type effect. We have argued previously, in the context of bosons, that the so-called flavour vacuum is the appropriate state to be used, at least for low-energy excitations, with energies/momenta up to a dynamically determined cutoff scale. In this work we evaluate the flavour-vacuum expectation value (condensate) of the stress-energy tensor of the (1/2)-spin fields with mixing in an effective low-energy Quantum Field Theory in this foam-induced curved space-time. We demonstrate, at late epochs of the Universe, that the fermionic vacuum condensate behaves as a fluid with negative pressure and positive energy, but alone it cannot lead to present-day accelerating Universes. One needs flavoured boson contributions for this purpose.Comment: 19 pages revtex, three eps figures incorporate

Flavour-Condensate-induced Breaking of Supersymmetry in Free Wess-Zumino Fluids

Recently we argued that a particular model of string-inspired quantum space-time foam (D-foam) may induce oscillations and mixing among flavoured particles. As a result, rather than the mass-eigenstate vacuum, the correct ground state to describe the underlying dynamics is the flavour vacuum, proposed some time ago by Blasone and Vitiello as a description of quantum field theories with mixing. At the microscopic level, the breaking of target-space supersymmetry is induced in our space-time foam model by the relative transverse motion of brane defects. Motivated by these results, we show that the flavour vacuum, introduced through an inequivalent representation of the canonical (anti-) commutation relations, provides a vehicle for the breaking of supersymmetry (SUSY) at a low-energy effective field theory level; on considering the flavour-vacuum expectation value of the energy-momentum tensor and comparing with the form of a perfect relativistic fluid, it is found that the bosonic sector contributes as dark energy while the fermion contribution is like dust. This indicates a strong and novel breaking of SUSY, of a non-perturbative nature, which may characterize the low energy field theory of certain quantum gravity models.Comment: Discussion added in sections II and IV on quantum-gravity induced flavour mixing, references added, conclusions unchange

Price Commitments in Standard Setting under Asymmetric Information

Many observers have voiced concerns that standards create essentiality and thus monopoly power for the holders of standard essential patents (SEPs). To address these concerns, Lerner and Tirole (2015) advocate structured price commitments, whereby SEP holders commit to the maximum royalty they would charge were their technology included in the standard. We consider a setting in which a technology implementer holds private information about demand. In this setting, price commitments increase efficiency not only by curbing SEP holders' market power, but also by alleviating distortions in the design of the royalty scheme. In the absence of price commitments, the SEP holder distorts the implementer's output downward in the low-demand state to reduce the high-demand type's information rent. Price commitments reduce this distortion

Effective thermal properties of fibre reinforced materials

The thermal behaviour of an elastic matrix reinforced with synthetic micro or macro fibres subjected to a constant heat flow is investigated in the present work. Steady-state condition for the heat flux is considered and isotropic thermal conductivity for both the matrix and fibres is assumed. Owing to the geometry of the system, reference is made to bipolar cylindrical coordinates. Various boundary conditions can be considered on the contours of the fibres. In particular, for a matrix reinforced with two fibres taken as insulated inclusions, a vanishing heat flow across the contour of the fibres must be imposed. After the temperature field has benn determined analytically, a homogeneization procedure is performed in order to find the equivalent thermal properties of the fibre reinforced composite material

THE ROLE OF CYCLOOXYGENASE-1 (COX-1) AND CYCLOOXYGENASE-2 (COX-2) IN A VENOUS THROMBOSIS MOUSE MODEL

Background: Deep vein thrombosis (DVT) is a serious national health problem, and pulmonary thromboembolism (PE) represents the life-threatening most common complication. Venous thromboembolism (VTE), including both these conditions, is traditionally treated with anticoagulant drugs. In particular, vitamin K antagonists and heparins are usually used in the reduction of thrombus development and in secondary prevention. However, the use of these drugs has several limitations: wide variability dose/response relationship between patients and in the same patient, multiple interactions with other drugs/foods, variability of daily doses, need of periodic withdrawals of blood during therapy, problems of overdosing. Then, the discovery of new drugs for VTE needs. The cyclooxygenase isoenzymes, COX-1 and COX-2, catalyse the formation of prostaglandins and, thromboxane from arachidonic acid, and play a critical role in thrombosis. Recent meta-analysis suggests that low-dose aspirin (ASA) reduces the rate of VTE recurrence. In contrast, the clinical use of COX-2 inhibitors seems associated with increased risk of venous thrombosis. However, the role of COX-1 and COX-2 in venous thrombosis remain unclear. Aim: We investigated the impact of COX-1 and COX-2 enzymes in venous thrombosis in order to identify the molecular mechanisms responsible for this effect and develop new therapeutic strategies to prevent venous thrombosis. In particular, we focused on the impact of inhibition of COX-pathway on leukocyte activation, important regulators of formation and propagation of venous thrombus. Methods and Results: Using in vivo and in vitro approaches, we provide evidence that: a) thromboxane, produced by platelets, triggers activation of leukocytes, with consequent development and propagation of venous thrombus induced by inferior vena cava ligation. In particular, we showed that ASA, by inhibiting irreversibly platelet COX-1, prevents platelet thromboxane production resulting in decreased venous thrombosis. b) COX-2 deletion induces platelet hyper-activity and hyper-coagulation state, associated with a reduced fibrinolysis and formation of bigger thrombi. In this scenario, the high levels of tissue factor observed in leukocytes of COX-2KO mouse may explain the positive association observed between administration of COX-2 inhibitors and VTE. Thanking advantage of an accurate, and clinically relevant, technique such as ultrasonography, we are setting a method helpful to monitor thrombus growing and to better understand the pathophysiology of venous thromboembolism. Conclusion: In conclusion, data obtained show that the inhibition of COX-1 and COX-2 in a venous thrombosis mouse model could lead to opposite effect on the thrombus development, stabilization and resolution. In particular, COX-1 inhibition is responsible of an impairment development and growth of venous thrombus, with a mechanism most likely dependent of TXA2/TP pathway. In contrast, COX-2 inhibition caused an increased in thrombus development, growing accompanied with reduction in the thrombus resolution. All data obtained support evidences that both COX-1 and COX-2 play a key role in DVT, opening the way to novel therapeutic approaches