Metal objects mapping after small charge explosions. A study on AISI 304Cu steel with two different grain sizes

Evidence of exposure of a metal component to a small charge explosion can be detected by observing microstructural modifications; they may be present even if the piece does not show noticeable overall plastic deformations. Particularly, if an austenitic stainless steel (or another metal having a face-centered cubic structure and a low stacking fault energy) is exposed to an explosive shock wave, high-speed deformation induces primarily mechanical twinning, whereas, in nonexplosive events, a lower velocity plastic deformation first induces slip. The occurrence of mechanical twins can be detected even if the surface is damaged or oxidized in successive events. In the present research, optical metallography (OM) and scanning electron microscopy (SEM), and scanning tunneling microscopy (STM) were used to detect microstructural modifications caused on AISI 304Cu steel disks by small-charge explosions. Spherical charges of 54.5 or 109 g TNT equivalent mass were used at explosive-to-target distances from 6.5 to 81.5 cm, achieving peak pressures from 160 to 0.5 MPa. Explosions induced limited or no macro-deformation. Two alloy grain sizes were tested. Surface OM and SEM evidenced partial surface melting, zones with recrystallization phenomena, and intense mechanical twinning, which was also detected by STM and X-ray diffraction. In the samples' interior, only twins were seen, up to some distance from the explosion impinged surface and again, at the shortest charge-to-sample distances, in a thin layer around the reflecting surface. For forensic science locating purposes after explosions, the maximum charge-to-target distance at which the phenomena disappear was singled out for each charge or grain size and related to the critical resolved shear stress for twinning.     

The “net” of the Internet: Risk Factors for Cyberbullying among Secondary-School Students in Greece

Cyberbullying is one of the most common threats an adolescent might face online with serious negative consequences at the social, emotional and educational level. Despite the intense study of the phenomenon over the past decade, most researchers ask for new directions in research that will focus on risk and protective factors. This study attempted to investigate the predictive effect of internet use, parental mediation, school-bullying and victimisation, gender and empathy on cyberbullying and cybervictimisation in two measurements, 4 months apart. Data collection was conducted using a self-report questionnaire. Four hundred and forty secondary school students, aged 12–14, participated in the study. The students were randomly selected from six public schools located in the Greater Metropolitan Area of Thessaloniki in Greece. Results showed that involvement in traditional bullying as a victim or as a perpetrator is the factor with the highest predictability for cyberbullying and cybervictimisation, which also remains stable across time. This finding points to the urgent need for designing and implementing programmes against all forms of bullying both offline and on line.     

Facilitating the entry of communities in the herbal medicine sector: GMCL in India

The medicinal plant sector is on the increase in many developing countries. Despite this, the existing supply chain is unable to improve the livelihoods of the gatherers. This article considers Gram Mooligai Company Limited (GMCL), the first community-based enterprise active in the herbal sector. GMCL promotes a more equitable sharing of benefits in the sector, while also aiming for a more sustainable use of natural resources. The article draws conclusions and lessons about supporting such types of enterprises, reforming the herbal-sector supply chain, and promoting new forms of partnership between ayurvedic firms and communities.