Prosocial Behavior and Posttraumatic Growth After Trauma

The purpose of this study was to examine prosocial behaviors of individuals who have or have not experienced individual traumas, and to assess whether experiencing multiple types of trauma will be related to prosocial behavior and posttraumatic growth. There were 118 undergraduate students who responded to an online survey comprised of three established measures. Participants indicated the nature of traumatic events through a checklist, with prosocial behavior and posttraumatic growth assessed through self-report questionnaires. There was no difference between those who experienced trauma and those who had not experienced trauma in their tendencies toward prosocial behavior. However, individuals who had experienced at least one traumatic event and who reported strong tendencies toward prosocial behavior did report higher levels of posttraumatic growth than those who reported weaker tendencies toward prosocial behavior. Although experiencing one or more than one type of traumatic event had no significant relationship with prosocial behavior, participants who experienced one type of traumatic event reported lower levels of posttraumatic growth than those who experienced more than one type of trauma. The potential for prosocial behavior to be linked more with posttraumatic growth than to traumatic experiences is discussed

Phase locked harmonic generation in the opaque region of GaAs

We demonstrate second and third harmonic generation from a GaAs substrate, well-below the absorption edge, in both transmission and reflection geometries. The pump is tuned at 1064 nm, in the transparency range, while the SH and the TH signals are tuned in the opaque spectral range of GaAs, at 532 nm and 355 nm, respectively. As expected, we find that the polarization of the generated signals is sensitive to the polarization of the pump. In our experiment, we work far from the phase matching condition and we account for both surface and bulk contributions, and show that the surface-generated SH components can be more intense than bulk-generated SH signals. The experimental results are contrasted with numerical simulations that include these two factors, using a hydrodynamic model that accounts for all salient aspects of the dynamics, including surface and bulk generated harmonic components.Peer ReviewedPostprint (published version

Study of the charge profile of thermally poled electrets

The charge profile of thermally poled electrets has been studied using two different methods, laser induced pressure pulse (LIPP) and pulsed electroacoustic (PEA), to gain insight into the mechanisms that are activated and assess which is the most appropriate method to study the charge profile. Disc--shaped PET samples have been conventionally poled to activate both the alpha and the rho relaxation and, right after, partially discharged up to a temperature Tpd. In this way, samples with a different combination of dipolar and space charge polarization have been obtained. Both LIPP and PEA reveal asymmetric profiles for Tpd below the glass transition temperature, that progressively become antisymmetric for higher temperatures. The shape and evolution of the charge profiles can be explained assuming injection of negative carriers from the anode that enhances the trapping of positive carriers near this electrode. It can be observed that PEA is able to detect a wider variety of polarization mechanisms in the system while LIPP gives a simpler picture of the charge profile.Comment: 19 pages, 11 figure

Laser Ultrasound Inspection Based on Wavelet Transform and Data Clustering for Defect Estimation in Metallic Samples

Laser-generated ultrasound is a modern non-destructive testing technique. It has been investigated over recent years as an alternative to classical ultrasonic methods, mainly in industrial maintenance and quality control procedures. In this study, the detection and reconstruction of internal defects in a metallic sample is performed by means of a time-frequency analysis of ultrasonic waves generated by a laser-induced thermal mechanism. In the proposed methodology, we used wavelet transform due to its multi-resolution time frequency characteristics. In order to isolate and estimate the corresponding time of flight of eventual ultrasonic echoes related to internal defects, a density-based spatial clustering was applied to the resulting time frequency maps. Using the laser scan beam’s position, the ultrasonic transducer’s location and the echoes’ arrival times were determined, the estimation of the defect’s position was carried out afterwards. Finally, clustering algorithms were applied to the resulting geometric solutions from the set of the laser scan points which was proposed to obtain a two-dimensional projection of the defect outline over the scan plane. The study demonstrates that the proposed method of wavelet transform ultrasonic imaging can be effectively applied to detect and size internal defects without any reference information, which represents a valuable outcome for various applications in the industry. View Full-TextPeer ReviewedPostprint (published version

Tailoring Čerenkov second-harmonic generation in bulk nonlinear photonic crystal

We investigate theoretically the Čerenkov-type second-harmonic generation in two-dimensional bulk nonlinear photonic crystal with longitudinal modulation of the (2) nonlinearity. We show that in this scheme the Čerenkov radiation can be achieved simultaneously at multiple directions with comparable intensities. The angles of emission are controllable by the spatial modulation of the nonlinearity. We propose a design of the periodically poled domain pattern, which maximizes the efficiency of the second-harmonic emission.The authors acknowledge the Australian Research Council for financial support. V. Roppo thanks Army Research Office (W911NF-10-2-0105) for the partial financial support

In situ decolorization monitoring of textile dyes for an optimized UV-LED/TiO2 reactor

Heterogeneous photocatalysis, using photocatalysts in suspension to eliminate diverse contaminants, including textile wastewater, has several advantages. Nevertheless, current absorbance and decolorization measurements imply sample acquisition by extraction at a fixed rate with consequent photocatalyst removal. This study presents online monitoring for the decolorization of six azo dyes, Orange PX-2R (OP2), Remazol Black B133 (RB), Procion Crimson H-EXL (PC), Procion Navy H-EXL (PN), Procion Blue H-EXL (PB), and Procion Yellow H-EXL (PY), analyzing the spectrum measured in situ by using the light scattering provided by the photocatalyst in suspension. The results obtained have corroborated the feasibility of obtaining absorbance and decolorization measurements, avoiding disturbances in the process due to a decrease in the volume in the reactor.Peer ReviewedPostprint (published version

Evaluation of the impact of an infrastructure on the city: the case of HST on Girona

Aquesta tesina detecta i fa una descripció exhaustiva de les conseqüències socioeconòmiques, urbanístiques i sobre la qualitat de vida que provocarà l'arribada d'una gran infraestructura a una ciutat, concretament, de la línia d'alta velooitat i d'una alternativa, basada en la millora de les prestacions de la línia convencional, a Girona

Resonant, broadband and highly efficient optical frequency conversion in semiconductor nanowire gratings at visible and UV wavelengths

Using a hydrodynamic approach we examine bulk- and surface-induced second and third harmonic generation from semiconductor nanowire gratings having a resonant nonlinearity in the absorption region. We demonstrate resonant, broadband and highly efficient optical frequency conversion: contrary to conventional wisdom, we show that harmonic generation can take full advantage of resonant nonlinearities in a spectral range where nonlinear optical coefficients are boosted well beyond what is achievable in the transparent, long-wavelength, non-resonant regime. Using femtosecond pulses with approximately 500 MW/cm2 peak power density, we predict third harmonic conversion efficiencies of approximately 1% in a silicon nanowire array, at nearly any desired UV or visible wavelength, including the range of negative dielectric constant. We also predict surface second harmonic conversion efficiencies of order 0.01%, depending on the electronic effective mass, bistable behavior of the signals as a result of a reshaped resonance, and the onset fifth order nonlinear effects. These remarkable findings, arising from the combined effects of nonlinear resonance dispersion, field localization, and phase-locking, could significantly extend the operational spectral bandwidth of silicon photonics, and strongly suggest that neither linear absorption nor skin depth should be motivating factors to exclude either semiconductors or metals from the list of useful or practical nonlinear materials in any spectral range.Comment: 12 pages, 4 figure