The interaction of two light filaments propagating in air is simulated. Simulations show that the interaction of the two light filaments displays interesting features such as attraction, fusion, repulsion, and spiral propagation, depending on the relative phase shift and the crossing angle between them. A long and stable channel can be formed by fusing two in-phase light filaments. The channel becomes unstable with the increase of the crossing angle and phase shift. The interaction of two light filaments in different planes is studied and the spiral propagation is observed.

The propagation of tightly focused femtosecond laser pulse with numerical aperture of 0.12 in air is investigated experimentally. The formation and evolution of the filament bunch are recorded by time-resolved shadowgraph with laser energy from 2.4 mJ to 47 mJ. The distribution of electron density in breakdown area is retrieved using Nomarski interferometer. It is found that intensity clamping during filamentation effect still play a role even under strong external focusing. The electron density in some interaction zones is higher than 3 × 10(19) cm(-3), which indicates that each air molecule there is ionized.

The incidence of neurodevelopmental disorders especially in children has been on the rise in recent decades, which is possibly caused by many different factors. In order to further explain this situation and arouse enough attention, this review will specifically elaborate genetic aspects and pathogenic hypothesis of these two kinds of neurodevelopmental diseases in children, autism and attention deficit hyperactivity disorder (ADHD) while analyzing the relationship between different environmental toxins and these two disorders. The effects of these pathogenic factors such as heavy metal lead, mercury, polyvinyl chloride (PVC) and polychlorinated biphenyls (PCBs) and their strong pathogenicity will be explained in detail through literature data retrieval and analysis. In addition, other neurotransmitter such as norepinephrine (NE) and serotonin (5-HT) signaling factors coming down to these two neurodevelopmental disorders and how their abnormal concentration present in the blood as well as the completely opposite results among experimental groups and control group will be elaborated. Furthermore, other high-risk and high-exposure factors may contribute to both diseases, such as alcohol and smoking abuse among parents, air pollutants PM2.5 and PM10 in the environment will also be discussed in the review. Since these environmental toxins and other harmful substances discussed in the paper have been linked to an increasing number of children with autism and ADHD in recent decades, from the medical perspective, this review will put forward certain succinct points to the aspects of minimizing relevant exposure or risks in clinical and daily life, as well as feasible suggestions in public health area for children, parents and prospective parents, to curb the growth of these two diseases in part by raising awareness in the population and reducing unnecessary exposure.

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