A New Review of Old Novae

Novae are certainly very exciting at the time of their eruptions, and there is much work left to be done in understanding all of the details of that part of their existence, but there is also much to be learned by looking at the systems decades, centuries, and even millennia after their peak. I give a brief overview of some of the history and motivation behind studying old novae and long-term nova evolution, and then focus on the state of the field today. Exciting new results are finally starting to shed some light on the secular behavior of post-nova systems, although as is often the case in astronomy, the observations are at times conflicting. As is always the case, we need more observations and better theoretical frameworks to truly understand the situation

Experimental characterization of friction properties of materials for innovative beam-to-column dissipative connection for low-damage RC structures

Low-damage design of structures in seismic-prone areas is becoming an efficient strategy to obtain "earthquake-proof" buildings, i.e. buildings that, even in the case of severe seismic actions, experience a low or negligible amount of damage. Besides the safeguard of human lives, this design strategy aims also to limit the downtime of buildings, which represents a significant source of economic loss, and to ensure an immediate occupancy in the aftermath of an earthquake. In this context, focusing on moment-resisting frames (MRFs), several solutions have been developed for the beam-to-column connections (BCCs) of steel and precast/prestressed concrete structures, but very few for cast-in-situ reinforced concrete (RC) structures. This paper focuses on a recently-proposed friction-based BCC for MRFs made with hybrid steel-trussed concrete beams (HSTCBs). The latter are made by a spatial lattice built using V-shaped rebars and a steel bottom plate, which eases the introduction of a friction dissipative device. HSTCBs are usually characterized by a small effective depth, which leads to a large amount of longitudinal rebars. The latter, together with a small-sized beam-column joint, make it potentially subjected to severe damage, which reduces its dissipative capacity. The shear force acting on the joint can be reduced by endowing the BCC with a friction device, with the aim of increasing the lever arm of the bending moment transferred between beam and joint, preventing the latter from damage. To evaluate the mechanical performance of the above connection, two experimental programs have been carried out at the Structures Laboratory of the University of Palermo. The first one focused on the characterization of the friction properties of two different materials (thermal sprayed aluminum and brass), by means of a linear dissipative device subjected to cyclic load. The second one tested a beam-to-column subassembly endowed with the recently-proposed connection in which the dissipative device was made with the best performing friction material tested before. The results of the cyclic tests are presented and commented, showing the promising performance of such connection in providing a low-damage behavior and a satisfactory dissipative capacity

Proton momentum distribution in a protein hydration shell

The momentum distribution of protons in the hydration shell of a globular protein has been measured through deep inelastic neutron scattering at 180 and 290 K, below and above the crossover temperature T-c=1.23T(g), where T-g=219 K is the glass transition temperature. It is found that the mean kinetic energy of the water hydrogens shows no temperature dependence, but the measurements are accurate enough to indicate a sensible change of momentum distribution and effective potential felt by protons, compatible with the transition from a single to a double potential well. This could support the presence of tunneling effects even at room temperature, playing an important role in biological function

Low-Damage Friction Connections in Hybrid Joints of Frames of Reinforced-Concrete Buildings

Seismic-resilient buildings are increasingly designed following low-damage and free-from-damage design strategies that aim to protect the structure’s primary load-bearing systems under ultimate-level seismic loads. With this scope, damping devices are located in accessible and easy-to-inspect sites within the main structural frames where the damage concentrates, allowing the primary structure to remain mostly undamaged or easily repairable after a severe earthquake. This paper analyses the effects of friction-damping devices in structural joints of RC buildings endowed with hybrid steel-trussed concrete beams (HSTCBs) and standard RC columns. The study proposes innovative solutions to be adopted into RC moment-resisting frames (MRFs) at beam-to-column connections (BCCs) and column-base connections (CBCs). The cyclic behaviour of the joint is analysed through 3D finite element models, while pushover and non-linear time history analyses are performed on simple two-storey and two-span MRFs endowed with the proposed devices. The main results show that the BCC endowed with curved slotted holes and Perfobond connectors is the most effective in preventing the damage that might occur in beam, column, and joint, and it is adequate to guarantee good dissipative properties. For CBCs, the results showed that the re-centering system with friction pads is the most effective in containing the peak and residual drifts, preventing the plasticization of the column base

Innovative connections for steel-concrete-trussed beams: a patented solution

The most recent design strategies welcome the adoption of innovative techniques for seismic energy input mitigation, aiming to achieve high dissipation capacity, prevent the structure from collapse and ensure the serviceability of the construction. Friction damper devices have been widely adopted in framed steel structures for decades, while their introduction in different structural types is still under investigation. This paper presents the outcomes of innovative research supported by the industry and conducted on beam-to-column connections of RC structures in which the beams are Hybrid Steel-Trussed Concrete Beams (HSTCBs) and the columns are classical RC pillars. An innovative solution, recently patented, has been found for the mitigation of the effects of seismic cyclic actions on small-sized beam-column joints, typically characterised by a large amount of longitudinal reinforcement due to the small effective depth of the beam. This paper collects the main featuring steps of the innovative research, which has led to the patented solution. The calculation procedure for designing the proposed connection is shown, and the validation through 3D finite element modelling is described. For the structural analysis of the joint, several monotonic and cyclic simulations have been carried out with the scope of investigating different design moment values. The finite element results proved that the patented solution is effective in preventing beam, column and joint from damage and it is suitable for exhibiting adequate dissipative capacity ensured by a flexural behaviour dominated by wide and stable hysteresis loops

Seismic Performance of Earthquake-Resilient RC Frames Made with HSTC Beams and Friction Damper Devices

Seismic behavior of RC frames with hybrid steel-trussed concrete beams is affected by panel zone damage due to a large amount of longitudinal reinforcement. Here the seismic efficiency of innovative frames characterized by friction damper devices (FDDs) at beam-to-column connections is compared against traditional frame. Three configurations are investigated: FDDs alone; FDDs with column-to-foundation connections having preloaded threaded bars and disk springs; FDDs with self-centering friction devices. Non-linear analyses show that FDDs alone prevent plastic hinge formation at beam ends and beam–column joint damage. FDDs with self-centering friction devices effectively limit both peak and residual drifts, avoiding column base plasticization

Combined acl and segond repair in combined acute proximal acl tears and segond fracture

A renewed interest in anterior cruciate ligament preservation has been noted using arthroscopic primary repair in patients with proximal tears, but the main concern remained the control of the rotational instability. Segond fracture occurs in less than 10% of cases of acute anterolateral instability, but it can result in continued rotation instability. The aim of this study is to describe the surgical technique to acutely repair both the anterior cruciate ligament and Segond fracture in the acute setting

Classification of sedimentary and igneous rocks by laser induced breakdown spectroscopy and nanoparticle-enhanced laser induced breakdown spectroscopy combined with principal component analysis and graph theory

In this work, results are presented on the application of standard LIBS and Nanoparticle-Enhanced LIBS (NELIBS) to the classification of rocks (igneous and sedimentary). The classification of the spectra obtained with the two methods was performed using Principal Component Analysis (PCA) and Graph Theory method. The results obtained confirmed the advantages of the LIBS technique in geological applications, showing that excellent classification of the rocks analyzed (more than 99% of the spectra correctly classified) can be obtained using standard LIBS coupled to Graph Theory analysis, while NELIBS spectra, analyzed with the same technique, provide acceptable results, but with 10% of the spectra not classified. These findings are particularly interesting given the application of the LIBS technique in investigating natural samples having porous and/or rough surfaces