Tuning ultrafast electron thermalization pathways in a van der Waals heterostructure

Ultrafast electron thermalization - the process leading to Auger recombination, carrier multiplication via impact ionization and hot carrier luminescence - occurs when optically excited electrons in a material undergo rapid electron-electron scattering to redistribute excess energy and reach electronic thermal equilibrium. Due to extremely short time and length scales, the measurement and manipulation of electron thermalization in nanoscale devices remains challenging even with the most advanced ultrafast laser techniques. Here, we overcome this challenge by leveraging the atomic thinness of two-dimensional van der Waals (vdW) materials in order to introduce a highly tunable electron transfer pathway that directly competes with electron thermalization. We realize this scheme in a graphene-boron nitride-graphene (G-BN-G) vdW heterostructure, through which optically excited carriers are transported from one graphene layer to the other. By applying an interlayer bias voltage or varying the excitation photon energy, interlayer carrier transport can be controlled to occur faster or slower than the intralayer scattering events, thus effectively tuning the electron thermalization pathways in graphene. Our findings, which demonstrate a novel means to probe and directly modulate electron energy transport in nanoscale materials, represent an important step toward designing and implementing novel optoelectronic and energy-harvesting devices with tailored microscopic properties.Comment: Accepted to Nature Physic

The importance of bracteoles in ensuring Atriplex halimus germination under optimal conditions

Atriplex halimus L. is a native halo-nitrophilous scrub that grows in salt-marsh environments and saline soils of the Mediterranean basin. The presence of bracteoles did not change the germination rate of seeds and fruits (seeds with bracteoles) in water, although bracteoles did slow down the process, from 2.5 to 5.7 days to reach the 50% of the final germination in seeds and fruits, respectively. Bracteoles prevented germination NaCl solutions greater than 0.3M. The seeds without bracteoles germinated at concentrations higher than 0.3M NaCl, but had smaller cotyledons than seeds germinated in water (3.1 and 5.6 mm, respectively), and all the roots had necrotic zones. The results showed that bracteoles play an important role in preventing seeds from germinating in NaCl concentrations higher than 0.3M, ensuring that they remained dormant and only germinated when freshwater was available. The recovery experiments showed that the seeds from the fruits that did not germinate in salt were not unviable, but remained dormant, awaiting the proper conditions to germinate. In the presence of water, the final germination was higher than 95%, and there was little necrosis found in the roots. The results showed how the presence of bracteoles prevented germination under unfavourable conditions for plant development

Development of an integrative cessation program for co-smokers of cigarettes and cannabis

BACKGROUND: Tobacco and cannabis use are strongly interrelated, but current national and international cessation programs typically focus on one substance, and address the other substance either only marginally or not at all. This study aimed to identify the demand for, and describe the development and content of, the first integrative group cessation program for co-smokers of cigarettes and cannabis. METHODS: First, a preliminary study using expert interviews, user focus groups with (ex-)smokers, and an online survey was conducted to investigate the demand for, and potential content of, an integrative smoking cessation program (ISCP) for tobacco and cannabis co-smokers. This study revealed that both experts and co-smokers considered an ISCP to be useful but expected only modest levels of readiness for participation.Based on the findings of the preliminary study, an interdisciplinary expert team developed a course concept and a recruitment strategy. The developed group cessation program is based on current treatment techniques (such as motivational interviewing, cognitive behavioural therapy, and self-control training) and structured into six course sessions.The program was evaluated regarding its acceptability among participants and course instructors. RESULTS: Both the participants and course instructors evaluated the course positively. Participants and instructors especially appreciated the group discussions and the modules that were aimed at developing personal strategies that could be applied during simultaneous cessation of tobacco and cannabis, such as dealing with craving, withdrawal, and high-risk situations. CONCLUSIONS: There is a clear demand for a double cessation program for co-users of cigarettes and cannabis, and the first group cessation program tailored for these users has been developed and evaluated for acceptability. In the near future, the feasibility of the program will be evaluated