Laser pulse annealing of ion-implanted GaAs

GaAs single-crystals wafers are implanted at room temperature with 400-keV Te + ions to a dose of 1×10^15 cm^–2 to form an amorphous surface layer. The recrystallization of this layer is investigated by backscattering spectrometry and transmission electron microscopy after transient annealing by Q-switched ruby laser irradiation. An energy density threshold of about 1.0 J/cm^2 exists above which the layer regrows epitaxially. Below the threshold the layer is polycrystalline; the grain size increases as the energy density approaches threshold. The results are analogous to those reported for the elemental semiconductors, Si and Ge. The threshold value observed is in good agreement with that predicted by the simple model successfully applied previously to Si and Ge

FLUOROQUINOLONES IN WATER: REMOVAL ATTEMPS BY INNOVATIVE AOPS

The photocatalytic activity of TiO2 semiconductor immobilized onto the surface of glass borosilicate tubes was evaluated for measuring levofloxacin, which is an antibiotic used to treat a number of bacterial infection

Radiosounding: Possible change in aerological data due to instrument change

radiosounding system allows to measure the profile of some meteorological quantities (temperature, humidity, pressure) from the ground up to a certain altitude. Such systems are continuously used by meteorological services in order to perform periodical measurements during the day, at pre-determined times. The evolution of instrumentation technology leads to a fast obsolescence of equipment through time, so that, inevitably, new instrumentation replaces the old one. The new VAISALA Radiosound RS92 has been recently introduced to substitute previous model RS90. The RS90 is currently used by many national and international institutes, including the Italian Air Force Meteorological Service (Servizio Meteorologico dell’Aeronautica Militare). In order to assess the way in which the substitution of RS90s with the new RS92s would affect measures performed by the altitude observation network with regard also to the historical series, several comparative measurements have been conducted by the “Reparto Sperimentazioni di Meteorologia Aeronautica” at Vigna di Valle (Rome). During this testing series, Company VAISALA has given a remarkable level of cooperation by a continuous presence of technicians. The entire test has been performed according to WMO (World Meteorological Organization) protocols

Joint inversion of seismic and electrical data in saturated porous media

Joint inversion strategies and physical constraints on model parameters may be used to mitigate equivalence problems caused by solution non-uniqueness. This strategy is quite a common practice in exploration geophysics, where dedicated rock physical studies are usually carried out, while it is not so frequent in near surface geophysics. We use porosity as a constraint among seismic wave velocities and electrical resistivity in a deterministic joint inversion algorithm for surface wave dispersion, P-wave traveltimes and apparent resistivity from vertical electrical sounding. These data are often available for near surface characterization. We show that the physical constraint among model parameters leads to internally consistent geophysical models in which solution non-uniqueness is mitigated. Moreover, an estimate of soil porosity is obtained as a relevant side product of the procedure. In particular, we consider a clean sand deposit and hence the appropriate formulations for the computation of porosity from seismic velocities and resistivity are implemented in the algorithm. We first demonstrate how the non-uniqueness of the solution is reduced in a synthetic case and then we applied the algorithm to a real-case study. The algorithm is here developed for one-dimensional condition and for granular soils to better investigate the physical constraint only, but it can be extended to the two-dimensional or three-dimensional case as well as to other materials with the adoption of proper rock physical relationships

Slender precast voided slabs under walking-induced vibration

Disturbance/discomfort caused by vibrations, induced by pedestrian walking on slabs in residential/office buildings, is a typical design issue for lightweight slender slabs, including prestressed concrete ones. Precast slabs are typically made with pretensioned members which allow for only partial collaboration in the transverse slab direction, which becomes even less effective when they are dry-assembled without cast-in-situ topping since it relies on the arrangement of mutual mechanical connections only. This study investigates through tests and numerical analyses the response of slender precast long-span slabs made with voided members, dry-assembled with mechanical connections, when subjected to vibrations generated by human activities. A parametric set of dynamic modal and time-history analyses encompassing floor member geometry, connection arrangement, mass, and damping, is carried out. The numerical models are validated against results from an experimental test program carried out on two decks of a prototype precast building. The tests and the numerical models allowed to characterize the fundamental dynamic properties of the slab and its vibrational performance, identifying the most efficient technological solutions among those investigated to mitigate human-induced vibrations

Learning by observation: insights from Williams syndrome.

Observing another person performing a complex action accelerates the observer's acquisition of the same action and limits the time-consuming process of learning by trial and error. Observational learning makes an interesting and potentially important topic in the developmental domain, especially when disorders are considered. The implications of studies aimed at clarifying whether and how this form of learning is spared by pathology are manifold. We focused on a specific population with learning and intellectual disabilities, the individuals with Williams syndrome. The performance of twenty-eight individuals with Williams syndrome was compared with that of mental age- and gender-matched thirty-two typically developing children on tasks of learning of a visuo-motor sequence by observation or by trial and error. Regardless of the learning modality, acquiring the correct sequence involved three main phases: a detection phase, in which participants discovered the correct sequence and learned how to perform the task; an exercise phase, in which they reproduced the sequence until performance was error-free; an automatization phase, in which by repeating the error-free sequence they became accurate and speedy. Participants with Williams syndrome beneficiated of observational training (in which they observed an actor detecting the visuo-motor sequence) in the detection phase, while they performed worse than typically developing children in the exercise and automatization phases. Thus, by exploiting competencies learned by observation, individuals with Williams syndrome detected the visuo-motor sequence, putting into action the appropriate procedural strategies. Conversely, their impaired performances in the exercise phases appeared linked to impaired spatial working memory, while their deficits in automatization phases to deficits in processes increasing efficiency and speed of the response. Overall, observational experience was advantageous for acquiring competencies, since it primed subjects' interest in the actions to be performed and functioned as a catalyst for executed action

Dynamic load tests on the North-South axis cable-stayed bridge with a non-symmetric central pylon.

Abstract The new cable-stayed bridge built for the North-South axis road of Bari in order to overpass the railway of RFI and Ferrotramviaria s.p.a. has been recently built and opened to the traffic. The bridge is 626 m long and the central cable-stayed bays have a total length of 225 m. They are supported by cables connected to a central upside down Y-shaped pylon. The peculiarity is that this column is about 60° rotated with respect to the axis of the bridge deck. A dynamic load tests was developed previously to open the bridge to conventional traffic. 26 piezoelectric accelerometers have been utilized in different positions of the cables-stayed bays to record the accelerations produced by environmental forces and by the impact produced by a loaded truck passing over a bump. Operational Modal Analysis has been applied by mean of Artemis software to determine the first fundamental frequencies and the mode shapes. The main frequency of this non-symmetric pylon is the main frequency of all the stayed bridge

The Polito Surface Wave flat-file Database (PSWD): statistical properties of test results and some inter-method comparisons

The compilation and maintenance of experimental databases are of crucial importance in all research fields, allowing for researchers to develop and test new methodologies. In this work, we present a flat-file database of experimental dispersion curves and shear wave velocity profiles, mainly from active surface wave testing, but including also data from passive surface wave testing and invasive methods. The Polito Surface Wave flat-file Database (PSWD) is a gathering of experimental measurements collected within the past 25 years at different Italian sites. Discussion on the database content is reported in this paper to evaluate some statistical properties of surface wave test results. Comparisons with other methods for shear wave velocity measurements are also considered. The main novelty of this work is the homogeneity of the PSWD in terms of processing and interpretation methods. A common processing strategy and a new inversion approach were applied to all the data in the PSWD to guarantee consistency. The PSWD can be useful for further correlation studies and is made available as a reference benchmark for the validation and verification of novel interpretation procedures by other researchers