Prevalence of thinness and its effect on height velocity in schoolchildren.

OBJECTIVE: In contrast to childhood obesity, studies involving thin children are much fewer, especially in developed countries. Furthermore, most reports do not address the impact of childhood thinness on height velocity. This study investigated the prevalence of thinness and its effect on height velocity in schoolchildren in the United Arab Emirates (UAE). Weight and height were measured in 29,410 schoolchildren (50.5% females), as part of the health assessment (academic year 2014-2015). The body mass index (BMI) was classified as normal, thinness, overweight, or obese using cutoffs established by the International Obesity Task Force (IOTF), World Health Organization, and Centers for Disease Control. RESULTS: The median age was 10.2 years (range, 3-19). Using the IOTF scale, one-quarter of the children aged 4-6 years and one-third of the children aged 7-9 years were thin (BMI ≤ 18.5 kg/m2). Thinness was less prevalent (8-10%) in adolescents. Group peak height velocity was delayed 1-3 years in thin children and was higher in children with excess body fat. In conclusion thinness was the highest (25-33%) in children aged 4-9 years of age and their peak height velocity was delayed 1-3 years when compared to the other children.

Robust Surface-Engineered Tape-Cast and Extrusion Methods to Fabricate Electrically-Conductive Poly(vinylidene fluoride)/Carbon Nanotube Filaments for Corrosion-Resistant 3D Printing Applications.

We developed a poly(vinylidene fluoride)/carbon nanotube (PVDF-MWCNT) filament as a feed for printing of electrically-conductive and corrosion-resistant functional material by fused filament fabrication (FFF). Using an environment-friendly procedure to fabricate PVDF-MWCNT filament, we achieved the best reported electrical conductivity of printable PVDF-MWCNT filament of 28.5 S cm-1 (90 wt% PVDF and 10 wt% CNT). The PVDF-MWCNT filaments are chemically stable in acid, base, and salt solution, with no significant changes in electrical conductivity and mass of the filaments. Our processing method is robust and allow a uniform mixture of PVDF and CNT with a wide range of CNT percentage up to 99.9%. We demonstrated the printing of PVDF-MWCNT filaments to create 3D shapes; printed using a low-cost commercial consumer-grade FFF 3D printer. We found many adjustments of printer parameters are needed to print filament with CNT content >10 wt%, but easier printing for CNT content ≤10 wt%. Since this was due to printer limitation, we believed that PVDF-MWCNT with higher CNT percentage (to a certain limit) and larger electrical conductivity could be printed with a custom-built printer (for example stronger motor). PVDF-MWCNT filament shows higher electrical conductivity (28.5 S cm-1) than compressed composite (8.8 S cm-1) of the same 10 wt% of CNT, due to more alignment of CNT in the longitudinal direction of the extruded filament. Printable PVDF-MWCNT-Fe2O3 (with a functional additive of Fe2O3) showed higher electrical conductivity in the longitudinal direction at the filament core (42 S cm-1) compared to that in the longitudinal direction at the filament shell (0.43 S cm-1) for sample with composition of 60 wt% PVDF, 20 wt% CNT, and 20 wt% Fe2O3, due to extrusion skin effect with segregation of electrically insulating Fe2O3 at the shell surface of PVDF-MWCNT-Fe2O3.