University of North Texas

About: University of North Texas is a education organization based out in Denton, Texas, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 11866 authors who have published 26984 publications receiving 705376 citations. The organization is also known as: Fight, North Texas & UNT.

Development and Application of Wood Flour-Filled Polylactic Acid Composite Filament for 3D Printing

Abstract: This paper presents the development of wood flour (WF)-filled polylactic acid (PLA) composite filaments for a fused deposition modeling (FDM) process with the aim of application to 3D printing. The composite filament consists of wood flour (5 wt %) in a PLA matrix. The detailed formulation and characterization of the composite filament were investigated experimentally, including tensile properties, microstructure, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The feedstock filaments of this composite were produced and used successfully in an assembled FDM 3D printer. The research concludes that compared with pure PLA filament, adding WF changed the microstructure of material fracture surface, the initial deformation resistance of the composite was enhanced, the starting thermal degradation temperature of the composite decreased slightly, and there were no effects on the melting temperature. The WF/PLA composite filament is suitable to be printed by the FDM process.

Mindfulness is associated with fewer PTSD symptoms, depressive symptoms, physical symptoms, and alcohol problems in urban firefighters.

Abstract: Objective This study investigated the association between mindfulness, other resilience resources, and several measures of health in 124 urban firefighters. Method Participants completed health measures of posttraumatic stress disorder (PTSD) symptoms, depressive symptoms, physical symptoms, and alcohol problems and measures of resilience resources including mindfulness, optimism, personal mastery, and social support. The Mindful Awareness and Attention Scale (MAAS; Brown & Ryan, 2003) was used to assess mindfulness. Participants also completed measures of firefighter stress, number of calls, and years as a firefighter as control variables. Hierarchical multiple regressions were conducted with the health measures as the dependent variables with 3 levels of independent variables: (a) demographic characteristics, (b) firefighter variables, and (c) resilience resources. Results The results showed that mindfulness was associated with fewer PTSD symptoms, depressive symptoms, physical symptoms, and alcohol problems when controlling for the other study variables. Personal mastery and social support were also related to fewer depressive symptoms, firefighter stress was related to more PTSD symptoms and alcohol problems, and years as a firefighter were related to fewer alcohol problems. Conclusions Mindfulness may be important to consider and include in models of stress, coping, and resilience in firefighters. Future studies should examine the prospective relationship between mindfulness and health in firefighters and others in high-stress occupations.

Role of bifunctional ammonia-lyase in grass cell wall biosynthesis

Abstract: L-Phenylalanine ammonia-lyase (PAL) is the first enzyme in the biosynthesis of phenylpropanoid-derived plant compounds such as flavonoids, coumarins and the cell wall polymer lignin. The cell walls of grasses possess higher proportions of syringyl (S)-rich lignins and high levels of esterified coumaric acid compared with those of dicotyledonous plants, and PAL from grasses can also possess tyrosine ammonia-lyase (TAL) activity, the reason for which has remained unclear. Using phylogenetic, transcriptomic and in vitro biochemical analyses, we identified a single homotetrameric bifunctional ammonia-lyase (PTAL) among eight BdPAL enzymes in the model grass species Brachypodium distachyon. (13)C isotope labelling experiments along with BdPTAL1-downregulation in transgenic plants showed that the TAL activity of BdPTAL1 can provide nearly half of the total lignin deposited in Brachypodium, with a preference for S-lignin and wall-bound coumarate biosynthesis, indicating that PTAL function is linked to the characteristic features of grass cell walls. Furthermore, isotope dilution experiments suggest that the pathways to lignin from L-phenylalanine and L-tyrosine are distinct beyond the formation of 4-coumarate, supporting the organization of lignin synthesis enzymes in one or more metabolons.

Efficient measurement of the percolation threshold for fully penetrable discs

Abstract: We study the percolation threshold for fully penetrable discs by measuring the average location of the frontier for a statistically inhomogeneous distribution of fully penetrable discs. We use two different algorithms to efficiently simulate the frontier, including the continuum analogue of an algorithm previously used for gradient percolation on a square lattice. We find that φc = 0.676 339 ± 0.000 004, thus providing an extra significant digit of accuracy to this constant. (Some figures in this article appear in colour in the electronic version; see www.iop.org)