Attention-Deficit Hyperactivity Disorder and Comorbid Mental Health Conditions Associated with Increased Risk of Injury.

Background: To describe the influence of attention-deficit hyperactivity disorder (ADHD) and comorbid mental health conditions on the risk of selected injuries. Methods: A retrospective cohort study design was employed using medical claim data from the Deseret Mutual Benefit Administrators (DMBA). Mental health conditions, injury, medication, and demographic data were extracted from claim files for ages 4-64, years 2016-2020. Results: Approximately 51.8% of individuals with ADHD had one or more comorbid mental health conditions (anxiety [37.0%], depression [29.9%], autism spectrum disorder (ASD) [3.6%], bipolar disorder [4.7%], obsessive compulsive disorder (OCD) [2.4%], schizophrenia [0.9%], and manic disorder [0.2%]). The rate of injury was 1.33 (95% CI 1.27-1.39) for ADHD only versus no ADHD and 1.62 (95% CI 1.56-1.68) for ADHD and comorbid mental health conditions versus no ADHD, after adjusting for age, sex, salary, and year. Cases with ADHD but no comorbid mental health conditions versus no ADHD were at increased risk of each of 12 types of injury. The increased risk was noticeably more pronounced for ADHD cases with one or more comorbid mental health conditions versus no ADHD. The greatest increased risk of injury was among ADHD cases with comorbid schizophrenia, followed by bipolar disorder and OCD. Comorbid autism disorder does not increase the risk of injury, but lowers it. Finally, the number of comorbid mental health conditions among ADHD cases was positively associated with increased injury rates (6% for one, 30% for two, 65% for three, and 129% for four). Conclusions: ADHD is positively associated with an increased risk of injury. Comorbid mental health conditions further increase the risk of injury among those with ADHD.

Graphene Strained by Defects.

Using graphene nanomechanical resonators we demonstrate the extent to which the mechanical properties of multilayer graphene films are controllable, in real time, through introduction and rearrangement of defects. We show both static and re-entrant (cyclical) changes in the tensile stress using a combination of ion implantation, chemical functionalization, and thermal treatment. While the dramatic increase in static tensile stress achievable through laser annealing can be of importance for various MEMS applications, we view the direct observation of a time-variable stress as even more significant. We find that defect-rich films exhibit a slow relaxation component of the tensile stress that remains in the resonator long after the laser exposure is finished (trelax ≈ 100 s ≫ tcooling), analogous to a wind-up toy. We attribute this persistent component of the time-variable stress to a set of metastable, multivacancy structures formed during the laser anneal. Our results indicate that significant stress fields generated by multivacancies, in combination with their finite lifetime, could make them a powerful and flexible tool in nanomechanics.

Removal of sodium dodecyl sulfate surfactant from aqueous dispersions of single-wall carbon nanotubes.

A reagent-based treatment method was developed for the removal of sodium dodecyl sulfate (SDS) from aqueous dispersions of single-wall carbon nanotubes (SWCNTs). Based on a survey of various reagents, organic solvents emerged as the most effective at interrupting the SDS:SWCNT interaction without producing deleterious side reactions or causing precipitation of the surfactant. Specifically, treatment with acetone or acetonitrile allows for the facile isolation of SWCNTs with near complete removal of SDS through vacuum filtration, resulting in a 100x reduction in processing time. These findings were validated via quantitative analysis using thermogravimetric analysis, Raman spectroscopy, 4-point probe electrical measurement, and X-ray photoelectron spectroscopy. Subsequent thermal oxidation further enhances the purity of the reagent treated samples and yields bulk SWCNT samples with >95% carbonaceous purity. The proposed reagent treatment method thus demonstrates potential for large volume SWCNT processing.

Modification of Silver/Single-Wall Carbon Nanotube Electrical Contact Interfaces via Ion Irradiation.

Introduction of defects via ion irradiation ex situ to modify silver/single-wall carbon nanotube (Ag-SWCNT) electrical contacts and the resulting changes in the electrical properties were studied. Two test samples were fabricated by depositing 0.1 µm Ag onto SWCNT thin films with average thicknesses of 10 and 60 nm, followed by ion irradiation (150 keV 11B+ at 5 × 1014 ions/cm2). The contact resistance (Rc) between the Ag and SWCNT thin films was determined using transfer length method (TLM) measurements before and after ion irradiation. Rc increases for both test samples after irradiation, while there is no change in Rc for control structures with thick Ag contacts (1.5 µm), indicating that changes in Rc originate from changes in the SWCNT films and at the Ag-SWCNT interface caused by ion penetration through the Ag contact electrodes. Rc increases by ∼4× for the 60 nm SWCNT structure and increases by ∼2.4× for the 10 nm SWCNT structure. Raman spectroscopy measurements of the SWCNTs under the contacts compared to the starting SWCNT film show that the degradation of the 10 nm SWCNT structure was less significant than that of the 60 nm SWCNT structure, suggesting that the smaller change in Rc for the 10 nm SWCNT structure is a result of the thickness-dependent damage profile in the SWCNTs. Despite the increase in overall contact resistance, further TLM analysis reveals that the specific contact resistance actually decreases by ∼3.5-4× for both test samples, suggesting an enhancement of the electrical properties at the Ag-SWCNT interface. Irradiation simulations provide a physical description of the underlying mechanism, revealing that Ag atoms are forward-scattered into the SWCNTs, creating an Ag/C interfacial layer several nanometers in depth. The collective results indicate competing effects of improvement of the Ag-SWCNT interface versus degradation of the bulk SWCNT films, which has implications for scaled high-performance devices employing thinner SWCNT films.