Explore the vast range of titles available.

In many geotechnical problems, the stress state may be approximated by a simple shear stress state. Owing to that, simple shear tests, in which the principal axes of stresses and strains are free to rotate, should be preferred to investigate the soil mechanical behaviour. However, the most common simple shear devices (rigid boundaries) do not allow to completely know the stress state of the specimen. Therefore, the interpretation of this test type has always been developed only theoretically. In order to improve the basic understanding of simple shear stress paths, a more innovative simple shear device with flexible boundaries was used in this research. The specimen is enclosed with an unreinforced membrane and confined by cell pressure. The diameter is kept constant through a sophisticated control system, which well approximates a K 0 condition. The undrained monotonic and cyclic simple shear tests on an Italian sand are presented and discussed. Based on some hypotheses, the stress state is reasonably determined and represented by Mohr’s circles. The theoretical interpretations show that the soil failure—under monotonic and cyclic loading—is reached when the effective intermediate principal stress is midway between the major and minor principal effective stresses ( b  = 0.5; θ  = 0), while the principal stress directions tend to reach a slope of 45°. Finally, the mechanical response of the tested sand is compared with the results of triaxial tests from a static and cyclic point of view. In agreement with several results reported in the literature, the friction angle in critical state conditions is higher in simple shear tests compared to that achieved in triaxial tests due to the rotation of principal stress directions. Moreover, the results of cyclic simple shear tests, in terms of liquefaction resistance (CRR 15  ≈ 0.13), are consistent with those performed in cyclic triaxial conditions.

Within the European project LIQUEFACT some activities have been devoted to the experimental verification of the effectiveness of two techniques in the mitigation of soil liquefaction susceptibility: induced partial saturation (IPS) and horizontal drains. After a preliminary check of their efficiency via centrifuge tests, the two techniques have been studied by means of some large scale shaking tests carried out in a field trial located in the Emilia-Romagna Region (Italy). A preliminary extensive in situ and laboratory investigation was necessary to identify the shallow liquefiable soil layer in which the mitigation techniques and the monitoring instrumentations (pore pressure transducers and geophones) had to be installed. Both techniques required the installation of horizontal well screens via a directional controlled drilling technique: the pipes were used as drainage systems (linear HDL and rhomboidal configurations HDR) or for the air injection in the area treated with IPS technique. The in situ experimental evidences showed that both techniques are able to avoid liquefaction triggering, that on the contrary was attained during the tests in the untreated testing area. The processing of in situ data highlighted that the efficiency of the two techniques is strictly related to chosen arrangement of the horizontal drains and the induced degree of saturation.

The simultaneous generation, dissipation and redistribution of excess pore pressures within the layers of a soil deposit, due to a seismic event, can significantly modify the seismic response of the whole deposit. The reliable estimate of the excess pore pressure induced by shaking within the soil is important to predict the behaviour of the soil at a large scale, and consequently, earthquake effects on built environment. Recently, pore pressure energy-based models are developing. Despite several advantages, their calibration is generally complex. The paper aims to provide a simple calibration procedure of the pore pressure energy-based prediction model developed by Berrill and Davis (1985), in order to make easier and more common the use to practitioners. The energy-based model of Berrill and Davis (1985) has been calibrated in this study by means of a dataset of 46 undrained cyclic triaxial and simple shear tests carried out on different sandy soils. The best fitting procedure with the envelope of the experimental curves has been adopted. The experimental evidences show that the two parameters (α and β) on which the model depends, are linked and can be related to the results of CPT or SPT in situ tests. The paper introduces two relationships to compute the calibration parameters from the well-known equivalent cone tip resistance (qc1Ncs) or the corrected SPT blow count ((N1)60cs). The applicability of the proposed procedure at a large scale has been discussed interpreting the results of cyclic simple shear tests on undisturbed sandy specimens from an energetic perspective. The validity of the calibration procedure has been finally verified performing 1D non-linear site response analyses by means of DEEPSOIL code, reproducing two centrifuge tests and three case histories. The close matching between the simulations of the excess pore pressure time histories with the experimental data of the centrifuge tests, together with the simulated excess pore pressure profiles of three case histories compared with the results achieved by using another 1D non-linear code demonstrates the effectiveness of the simplified procedure to calibrate the pore pressure energy-based prediction model of Berrill and Davis (1985).

Many catalytic reactions under fixed conditions exhibit oscillatory behaviour. The oscillations are often attributed to dynamic changes in the catalyst surface. So far, however, such relationships were difficult to determine for catalysts consisting of supported nanoparticles. Here, we employ a nanoreactor to study the oscillatory CO oxidation catalysed by Pt nanoparticles using time-resolved high-resolution transmission electron microscopy, mass spectrometry and calorimetry. The observations reveal that periodic changes in the CO oxidation are synchronous with a periodic refacetting of the Pt nanoparticles. The oscillatory reaction is modelled using density functional theory and mass transport calculations, considering the CO adsorption energy and the oxidation rate as site-dependent. We find that to successfully explain the oscillations, the model must contain the phenomenon of refacetting. The nanoreactor approach can thus provide atomic-scale information that is specific to surface sites. This will improve the understanding of dynamic properties in catalysis and related fields. Many catalytic reactions exhibit oscillatory behaviour but these oscillations are not well understood for catalysts consisting of supported nanoparticles. The study of oscillatory CO oxidation catalysed by Pt nanoparticles now reveals that periodic changes in the CO oxidation are synchronous with a periodic refacetting of the Pt nanoparticles.

Background Neonatal adrenal hemorrhage is a relatively uncommon condition (0.2–0.55%). Various risk factors have been reported in addition to birth asphyxia, such as sepsis, coagulation disorders, traumatic delivery, and perinatal injuries. Adrenal hemorrhage usually affects the right adrenal gland (about 70% of cases) while it involves the bilateral adrenal gland only in 10% of cases. In most cases, the event is asymptomatic but, in others, it may be so devastating to determine death by bleeding or adrenal insufficiency. Case presentation A case of bilateral neonatal adrenal hemorrhage, with adrenal insufficiency, but with no important risk factors and favorable evolution in a male infant. Conclusions This case emphasizes the importance of keeping a non-interventional attitude, avoiding early surgery but carrying out a serial sonographic follow-up. Serial ultrasound monitoring is the most reliable approach during conservative management.

Nowadays dredged materials are increasingly seen as a resource, and strategies and methodologies for their beneficial reuse are being developed throughout the world. When dealing with fine grained sediments, electro-osmotic treatment is very promising to this aim, being able to speed up dewatering and to remove contaminants. The paper presents the first results of an experimental activity started to get an insight on the ability of electric treatment to strengthen fine grained dredged soils. A special oedometer was adopted to this aim, capable of applying different combinations of mechanical and electric loads to the soil, and large enough to allow the final retrieval of specimens to be tested in a triaxial cell. Both the oedometric and the triaxial test results obtained on a soft dredged material at a very high water content indicate that the application of a low voltage produces a negligible volumetric reduction but a complete change in the mechanical behaviour of the treated soil. Upon electro-osmotic consolidation, the soil—still having a very high void ratio—behaves as being over-consolidated, with a brittle behaviour in the triaxial tests and a large increase of the yielding strength in the oedometric tests. It is argued that such a sharp change in the macro-mechanical response of the treated soil is not related to the amount of water removed but to the change in soil microstructure caused by the removal of part of the electrically bonded water during the electroosmotic process.

We describe the setup for the broadband millimeter/submillimeter characterization of the quasi-optical elements and the dielectric materials commonly used in microwave receivers operated in microwave astronomy. The setup is made of a large aperture (100 mm) Fourier transform spectrometer coupled to a transition edge superconducting detector. The system has been assembled and characterized in different configurations and operation modes for the acquisition of interferograms from various kinds of samples. After the initial test runs, the configuration is now being updated to ensure a broader range of measurements, including reflectance and scattering. We plan to first use this testbed for the characterization of the dielectric materials used in the LSPE/SWIPE experiment, devoted to the study the polarization of the Cosmic Microwave Background.

Large radio and mm–wave telescopes use very sensitive detectors requiring cryogenic cooling to reduce detector noise. Pulse Tubes (PT) cryocoolers are widely used to reach temperatures of a few K, defining the base temperature of further sub–K stages. This technology represents an effective solution for continuous operation, featuring high stability and reduced vibration levels on the detectors. However, the compressor used to operate the PT is a significant source of microphonics and electrical noise, making its use at the focus of large steerable telescopes not advisable. This calls for long flexible helium lines between the compressor, operated at the base of the radio telescope, and the cold–head, mounted in the receivers cabin with the receiver detectors. The distance between the receiver cabin and the base can be >100 m long for large radio telescopes. In the framework of our development of the MIllimetric Sardinia radio Telescope Receiver based on Array of Lumped elements kids (MISTRAL), a W–band camera working at the Gregorian focus of the 64 m aperture Sardinia Radio Telescope (SRT) with an array of Lumped Elements Kinetic Inductance Detectors (LEKID), we have developed a cryogenic system based on a PT refrigerator as the first cooling stage. Here we describe the MISTRAL cryogenic system and focus on the validation of the use of a commercial PT Cryocooler with 100 m helium lines running from the cold head to the compressor unit. The configuration allows us to operate the 0.9 W PT reaching below 4.2 K with 0.5 W dissipation.

The MIllimetric Sardinia radio Telescope Receiver based on Array of Lumped elements KIDs, MISTRAL, is a cryogenic W-band (77–103 GH) LEKID camera which will be integrated at the Gregorian focus of the 64 m aperture Sardinia Radio Telescope, in Italy, in Autumn 2022. This instrument, thanks to its high angular resolution ( ∼ 13 arcsec ) and the wide instantaneous field of view ( ∼ 4 arcmin ), will allow continuum surveys of the mm-wave sky with a variety of scientific targets, spanning from extragalactic astrophysics to solar system science. In this contribution, we will describe the design of the MISTRAL camera, with a particular focus on the optimisation and test of a prototype of the focal plane.

In this paper, we present beam pattern tests performed on the SWIPE multi-mode bolometric detector pixel assembly. A 20-mm-aperture horn is coupled to a large detector absorber (10 mm diameter) with a TES sensor located on the side. The pixel assembly has been tested at the bolometer base temperature of 340 mK, inside a custom cryogenic test bed, looking at a Gunn oscillator (128 GHz) located in the far field. We developed a custom cryogenic neoprene absorber, in addition to the stack of standard metal meshes low-pass filters, to reduce the background on the detector at a level similar to the one expected in flight, allowing to measure the main beam of the pixel assembly. The measured FWHM is 21 ∘ , slightly narrower than the expected one (24 ∘ ), due to vignetting produced by the filters stack.