Browsing by Subject "Kinetic parameters"

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Fire safety in sustainable buildings : status, options, alternatives
(2017-05) Roberts, Bonnie Colleen; Ezekoye, Ofodike A.; Webber, Michael E., 1971-; Ellison, Christopher J.; Ellzey, Janet L.
Sustainable design is a holistic goal of efficiency and optimization to reduce building energy consumption and environmental impact while improving occupant health and safety. Sustainable building construction is one of the fastest growing industries in the United States. Changes in materials, products, designs, and methodologies are occurring to accommodate this green progression. While these changes have energy and environmental benefits, questions have been raised about the impacts on fire safety. As sustainability is rapidly adopted in the building construction industry, so too must our understanding of fire safety implications. It is possible that a single fire event can negate several, if not all, elements of green design. Intermingling green design and fire safety such that they reinforce rather than undermine each other would produce a net benefit to both humans and the environment. Without this consideration, green design could unintentionally increase fire risk and damage. To begin addressing some of these concerns, a three-pronged approach was taken in this research. First, a detailed qualitative examination of the relationship between fire safety and sustainability in buildings was conducted, including a discussion on the status of the fire and sustainability communities and recommendations on areas for development and implementation to promote fire safe sustainable designs. This first analysis concludes that exchange between the sustainability and fire safety communities is inadequate. The fire safety community is focused on quantifying and tracking such implications with a concern for firefighter security and training, while the sustainability community is focused on meeting the minimum building code requirements for fire protection. Second, a quantitative analysis on thermal insulation, an essential building material, was performed to demonstrate the current options available to designers and regulators and, more generally, how to integrate both fire safety and sustainability in material selection. A pointed result of this work is that rockwool, an insulation popular in Europe but rarely used in the United States, consistently ranked as a top performer. In the third component of this work, an investigation into the viability of two alternative, reportedly environmentally benign flame retardants (FRs) was conducted for use on flexible polyurethane foam (PU), a prevalent material in interior furnishings. Several previously unknown characteristics of these unique FRs were discovered through this work, including dissimilarities to a conventional halogenated FR treatment. In summary, this research elucidates the current status of the nexus of fire safety and sustainability, offers an immediate method of selecting preferable material options, and validates sustainable FR alternatives.
Forces governing nucleic acid compaction investigated by quantitative crosslinking and FRET
(2022-05-06) Hamilton, Ian Scott; Russell, Rick, 1969-; Elber, Ron; Ren, Pengyu; Finkelstein, Ilya
Nucleic acid compaction is ubiquitous in biology, from chromatin and genome packing to RNA folding. Nature achieves these different processes in several different ways, but in all cases nucleic acid helices must be brought into contact or close proximity, often at a substantial free energy penalty. We developed quantitative disulfide crosslinking and tethered FRET techniques to measure the energetics of these fundamental interactions, and to explore the factors influencing them. We used a bimolecular crosslinking assay to measure the electrostatic repulsion governing unmediated encounters between DNA helices. By varying the length of the crosslinker probes, we established the size of the ion atmosphere surrounding the helices under different ionic conditions. We complemented these results with a FRET assay of the relative orientations of two DNA helices tethered by a short PEG linker. In the presence of Na⁺ or Mg²⁺, both bimolecular crosslinking and tethered FRET revealed a transition from a low salt regime dominated by electrostatic repulsion to a high salt electrically screened regime dominated by thermal motion. With Co(NH₃)₆³⁺, both assays revealed a transition to a net attractive regime with dilute phase characteristics consistent with previously observed Co-induced DNA condensates, suggesting that such condensates are the result of pairwise interhelical attraction. We also used an intramolecular crosslinking assay to measure the energetics of sharply bent conformations for a selection of RNA two-helix junctions. For model oligo-U bulges and junctions (Uₓ₌₂₋₇Uᵧ₌₀₋₃), junctions with more unpaired nucleotides on the longer strand (Uₓ) displayed more frequent sharp bending, with little dependence on the length of the shorter strand (Uᵧ). We probed different bent conformations by varying the crosslinker positions, identifying conformational preferences up to ~3 kcal/mol among different bent states. We also examined four naturally-occurring junction sequences (two from ribosomal RNAs and two from group I introns) that are sharply bent in their native folds. We found that these natural junction sequences do not selectively stabilize specific bent conformations corresponding to their native folds, instead exhibiting conformational lability, and behaving much like their oligo-U topological counterparts.