• 3D-printed tubes with complex internal fins for heat transfer enhancement—CFD analysis and performance evaluation

      Wei, Chao; Vasquez Diaz, Gabriel Alexander; Wang, Kun; Li, Peiwen; Univ Arizona, Dept Aerosp & Mech Engn (AMER INST MATHEMATICAL SCIENCES-AIMS, 2019-12-27)
      Additive manufacturing (AM), also known as 3D printing technology, is applied to fabricate complex fin structures for heat transfer enhancement at inner surface of tubes, which conventional manufacturing technology cannot make. This work considered rectangular fins, scale fins, and delta fins with staggered alignment at the inner wall of heat transfer tubes for heat transfer enhancement of internal flows. Laminar flow convective heat transfer at 500 < Re < 2000 has been numerically studied, and heat transfer performance of the tubes with 3D-printed interrupted fins has been compared to that with conventional straight continuous fins and smooth tubes. The benefit from heat transfer enhancement and the loss due to increased pumping pressure is evaluated using the total entropy generation rate in the control volume of heat transfer tube. The heat transfer coefficient in tubes with interrupted fins in staggered arrangement can have 2.6 times of that of smooth tube and 1.4 times of that with conventional continuous straight fins. The entropy generation in the tubes with interrupted fins in staggered arrangement only has 30-50% of that of smooth tube or tube with traditional continuous straight fins. The benefit of using interrupted fins in staggered arrangement is significant.
    • Cigarette smoke extract is a Nox agonist and regulates ENaC in alveolar type 2 cells

      Downs, Charles A.; Alli, Abdel A.; Johnson, Nicholle M.; Helms, My N.; Univ Arizona, Coll Nursing; Univ Arizona, Coll Med, Div Translat & Regenerat Med (AMER INST MATHEMATICAL SCIENCES-AIMS, 2016)
      There is considerable evidence that cigarette smoking is the primary etiology of chronic obstructive pulmonary disease (COPD), and that oxidative stress occurs in COPD with the family of tissue nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox) enzymes playing a significant role in lung pathogenesis. The purpose of this study was to determine the effects of cigarette smoke extract (CSE) on Nox signaling to epithelial sodium channels (ENaCs). Pre-treatment with diphenyleneiodonium (DPI), a pan-Nox inhibitor, prevented stimulatory effects of CSE on ENaC activity; open probability (Po) changed from 0.36 +/- 0.09 to 0.11 +/- 0.02; n=10, p=0.01 following CSE and DPI exposure. Likewise, Fulvene-5 (which inhibits Nox2 and Nox4 isoforms) decreased the number of ENaC per patch (from 2.75 +/- 0.25 to 1 +/- 0.5, n=9, p=0.002) and open probability (0.18 +/- 0.08 to 0.02 +/- 0.08, p=0.04). Cycloheximide chase assays show that CSE exposure prevented alpha-ENaC subunit degradation, whereas concurrent CSE exposure in the presence of Nox inhibitor, Fulvene 5, resulted in normal proteolytic degradation of alpha-ENaC protein in primary isolated lung cells. In vivo, co-instillation of CSE and Nox inhibitor promoted alveolar flooding in C57Bl6 mice compared to accelerated rates of fluid clearance observed in CSE alone instilled lungs. Real-time PCR indicates that mRNA levels of Nox2 were unaffected by CSE treatment while Nox4 transcript levels significantly increased 3.5 fold in response to CSE. Data indicate that CSE is an agonist of Nox4 enzymatic activity, and that CSE-mediated Nox4 plays an important role in altering lung ENaC activity.
    • Discrete time darwinian dynamics and semelparity versus iteroparity

      M. Cushing, J.; Univ Arizona, Dept Math, Interdisciplinary Program Appl Math (AMER INST MATHEMATICAL SCIENCES-AIMS, 2019)
      We derive and analyze a Darwinian dynamic model based on a general difference equation population model under the assumption of a trade-off between fertility and survival. Both inherent and density dependent terms are functions of a phenotypic trait (subject to Darwinian evolution) and its population mean. We prove general theorems about the existence and stability of extinction equilibria and the bifurcation of positive equilibria when extinction equilibria destabilize. We apply these results, together with the Evolutionarily Stable Strategy (ESS) Maximum Principle, to the model when both semelparous and iteroparous traits are available to individuals in the population. We find that if the density terms in the population model are trait independent, then only semelparous equilibria are ESS. When density terms do depend on the trait, then in a neighborhood of a bifurcation point it is again the case that only semelparous equilibria are ESS. However, we also show by simulations that ESS iteroparous (and also non-ESS semelparous) equilibria can arise outside a neighborhood of bifurcation points when density effects depend in a hierarchical manner on the trait.
    • Hyperoxia impairs pro-angiogenic RNA production in preterm endothelial colony-forming cells

      Ahern, Megan A.; Black, Claudine P.; Seedorf, Gregory J.; Baker, Christopher D.; Shepherd, Douglas P.; Univ Arizona, Dept Physiol (AMER INST MATHEMATICAL SCIENCES-AIMS, 2017)
      Disruptions in the response of endothelial progenitor cells to changes in oxygen environment may present a possible mechanism behind multiple pediatric pulmonary disease models, such as bronchopulmonary dysplasia. Using high-throughput fixed single-cell protein and RNA imaging, we have created "stop-motion" movies of Thymosin. 4 (T beta 4) and Hypoxia Inducible Factor 1 alpha (HIF-1 alpha) protein expression and vascular endothelial growth factor (vegf) and endothelial nitric oxide synthase (eNOS) mRNA in human umbilical cord-derived endothelial colony-forming cells (ECFC). ECFC were grown in vitro under both room air and hyperoxia (50% O-2). We find elevated basal T beta 4 protein expression in ECFC derived from prematurely born infants versus full term infants. T beta 4 is a potent growth hormone that additionally acts as an actin sequestration protein and regulates the stability of HIF-1 alpha. This basal level increase of T beta 4 is associated with lower HIF1 alpha nuclear localization in preterm versus term ECFC upon exposure to hyperoxia. We find altered expression in the pro-angiogenic genes vegf and eNOS, two genes that HIF-1 alpha acts as a transcription factor for. This provides a potential link between a developmentally regulated protein and previously observed impaired function of preterm ECFC in response to hyperoxia.
    • Lending Sociodynamics and Drivers of the Financial Business Cycle

      J. Hawkins, Raymond; Kuang, Hengyu; Univ Arizona, Coll Opt Sci (AMER INST MATHEMATICAL SCIENCES-AIMS, 2017)
      We extend sociodynamic modeling of the financial business cycle to the Euro Area and Japan. Using an opinion-formation model and machine learning techniques we find stable model estimation of the financial business cycle using central bank lending surveys and a few selected macroeconomic variables. We find that banks have asymmetric response to good and bad economic information, and that banks adapt to their peers' opinions when changing lending policies.