Browsing by Subject "Humidity"

Now showing 1 - 4 of 4

Austin climate data
(2009-10) Ward, Natalie
An overview of the climate conditions that impact on the energy efficiency of construction projects in Austin, Texas. Data is presented on various factors, including temperature, precipitation, daylight, and wind.
Impact of humidity and polymer blending on the gas transport properties of polybenzimidazoles
(2019-07-17) Moon, Joshua David; Freeman, B. D. (Benny D.); Paul, Donald R.; Sanchez, Isaac C; Riffle, Judy S; Lynd, Nathaniel A
Polybenzimidazoles (PBIs) are attractive polymers for gas separation membranes due to their high chemical and thermal stability and rigid, size-selective molecular structures. Opportunities exist for using PBIs for high temperature H₂/CO₂ separation, among other separations, where significant amounts of water are often present. However, PBIs are uniquely hydrophilic glassy polymers, and the impact of humidity on PBI gas transport properties is not well understood. Highly sorbing penetrants like water are often considered to affect molecular transport in polymers through phenomena such as competitive sorption, antiplasticization, and plasticization, but greater fundamental understanding is needed to relate these phenomena to other key concepts in polymer transport like free volume. Additionally, opportunities exist to improve low PBI gas permeabilities through material modification. This study investigates fundamentals of water sorption, dilation, and diffusion in PBIs to develop a systematic understanding of how water uptake affects molecular transport in hydrophilic glassy polymers. Water vapor sorption and swelling in PBIs were experimentally measured, which enabled direct evaluation of polymer free volume changes arising from water uptake. Gas transport properties were measured across a range of humidities using a custom experimental apparatus and correlated with humidity-induced free volume changes. This analysis enabled unique insight into the tradeoff between competitive sorption, antiplasticization, and plasticization effects of water sorption on PBI transport properties. Similar analysis could be used to investigate fundamentals of mixed penetrant sorption and diffusion in other polymers. Finally, a method of improving PBI gas separation properties by blending PBIs with a more permeable polymer was investigated. Commercial PBI was blended with an ortho-functional polyimide capable of undergoing thermal rearrangement at high temperatures. Films of PBI blended with a small fraction of polyimide exhibited matrix-droplet morphologies that enabled synergistic combination of PBI and polyimide gas separation properties. Heat treatment caused thermal rearrangement of the polyimide phase, increasing blend H₂ permeabilities, while also increasing structural order in the PBI phase, increasing blend H₂/CO₂ selectivities. The net result of heat treatment was simultaneous improvement in both H₂ permeability and H₂/CO₂ selectivity at ambient temperatures, surpassing the 2008 H₂/CO₂ upper bound
Standards of human comfort: relative and absolute
(2009-10) Fincher, Warren; Boduch, Michael
An examination of the factors that affect the quality of comfort in an architectural environment, including temperature, lighting, humidity, and air quality. The paper also considers the variability of individual and cultural perceptions of comfort in determining how designers might create an optimal living or work space.
Uncovering the neuromolecular basis for hygrotaxis in Caenorhabditis elegans
(2014-08) Russell, Joshua Coulter; Pierce-Shimomura, Jonathan T.; Aldrich, Richard W; Gross, Jeffery M; Atkinson, Nigel S.; Morikawa, Hitoshi
All terrestrial animals must find a proper level of moisture to ensure their health and survival. However, the molecular basis for sensing humidity is unknown in most animals. We used the model nematode Caenorhabditis elegans to uncover a novel mechanism to sense humidity. We found that C. elegans displayed a strong preference, orienting to gradients as shallow as 0.03% relative humidity per mm. Cell-specific ablation and rescue experiments demonstrate that orientation to humidity in C. elegans requires the obligatory combination of distinct mechanosensitive and thermosensitive pathways. The mechanosensitive pathway requires a conserved DEG/ENaC/ASIC mechanoreceptor complex in the FLP neuron pair. Because humidity levels influence the hydration of the worm’s cuticle, our results suggest that FLP may convey humidity information by reporting the degree that subcuticular dendritic sensory branches of FLP neurons are stretched by hydration. The thermosensitive pathway requires cGMP-gated channels in the AFD neuron pair. Because humidity levels affect evaporative cooling, AFD may convey humidity information by reporting thermal flux. Thus, humidity sensation arises as a metamodality in C. elegans that requires the integration of parallel mechanosensory and thermosensory pathways. This hygrosensation strategy, first proposed by Thunberg over 100 years ago, may be conserved because the underlying pathways have cellular and molecular equivalents across a wide range of species including insects and humans. Whereas well-fed worms raised in non-crowded conditions prefer high humidity levels starved worms prefer lower humidity ranges. Our results suggest a model in which social cues from pheromone signaling, along with the worm’s feeding state, influence cyclic guanosine monophosphate (cGMP), peptide, and protein kinase C signaling to produce opposite hygrotaxis behavior.