Convective heat transfer over thin ice covered coastal polynyas

Polynyas play an important role in the regional meteorology and oceanography of the high latitudes and in the global ocean circulation. Unique low-level observations of an Antarctic coastal polynya, the Ronne Polynya, were conducted using an instrumented aircraft. At the time of the observations, the polynya was mostly covered with thin ice perforated with holes and was composed of two distinct regimes: an inner region of newly formed and thin ice and an outer region of thicker more consolidated ice. The sensible heat flux over the polynya was similar to 100 W m(-2) and decreased with fetch, primarily as a result of the thickening ice cover. The mean sensible heat transfer and drag coefficients over the polynya were C-HN10 = (0.7 +/- 0.1) x 10(-3) and C-DN10 = (1.1 +/- 0.2) x 10(-3), respectively. The heat transfer coefficient is similar to that found over heterogeneous sea ice and is significantly lower than has been used in previous studies of heat fluxes over polynyas, which are often assumed to be open water. The transfer coefficients were not found to be a function of fetch or ice conditions as represented by the surface temperature and albedo. The data were used in an investigation of the output of sensible heat flux, potential temperature, and boundary layer depth from a simple fetch-dependent model. For this case study, surface temperatures and transfer coefficients appropriate to an ice-covered surface were required for an accurate simulation

Oligofructose improves small intestinal lipid-sensing mechanisms via alterations to the small intestinal microbiota

Background: Upper small intestinal dietary lipids activate a gut-brain axis regulating energy homeostasis. The prebiotic, oligofructose (OFS) improves body weight and adiposity during metabolic dysregulation but the exact mechanisms remain unknown. This study examines whether alterations to the small intestinal microbiota following OFS treatment improve small intestinal lipid-sensing to regulate food intake in high fat (HF)-fed rats. Results: In rats fed a HF diet for 4 weeks, OFS supplementation decreased food intake and meal size within 2 days, and reduced body weight and adiposity after 6 weeks. Acute (3 day) OFS treatment restored small intestinal lipid-induced satiation during HF-feeding, and was associated with increased small intestinal CD36 expression, portal GLP-1 levels and hindbrain neuronal activation following a small intestinal lipid infusion. Transplant of the small intestinal microbiota from acute OFS treated donors into HF-fed rats also restored lipid-sensing mechanisms to lower food intake. 16S rRNA gene sequencing revealed that both long and short-term OFS altered the small intestinal microbiota, increasing Bifidobacterium relative abundance. Small intestinal administration of Bifidobacterium pseudolongum to HF-fed rats improved small intestinal lipid-sensing to decrease food intake. Conclusion: OFS supplementation rapidly modulates the small intestinal gut microbiota, which mediates improvements in small intestinal lipid sensing mechanisms that control food intake to improve energy homeostasis. [MediaObject not available: see fulltext.] © 2023, The Author(s).Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

The international sinonasal microbiome study (ISMS): a multi-centre, multi-national characterization of sinonasal bacterial ecology

First published: 13 March 2020The sinonasal microbiome remains poorly defined, with our current knowledge based on a few cohort studies whose findings are inconsistent. Furthermore, the variability of the sinus microbiome across geographical divides remains unexplored. We characterise the sinonasal microbiome and its geographical variations in both health and disease using 16S rRNA gene sequencing of 410 individuals from across the world. Although the sinus microbial ecology is highly variable between individuals, we identify a core microbiome comprised of Corynebacterium, Staphylococcus, Streptococcus, Haemophilus, and Moraxella species in both healthy and chronic rhinosinusitis (CRS) cohorts. Corynebacterium (mean relative abundance = 44.02%) and Staphylococcus (mean relative abundance = 27.34%) appear particularly dominant in the majority of patients sampled. Amongst patients suffering from CRS with nasal polyps, a statistically significant reduction in relative abundance of Corynebacterium (40.29% vs 50.43%; p = 0.02) was identified. Despite some measured differences in microbiome composition and diversity between some of the participating centres in our cohort, these differences would not alter the general pattern of core organisms described. Nevertheless, atypical or unusual organisms reported in short-read amplicon sequencing studies and that are not part of the core microbiome should be interpreted with caution. The delineation of the sinonasal microbiome and standardised methodology described within our study will enable further characterisation and translational application of the sinus microbiota.Sathish Paramasivan, Ahmed Bassiouni ... Clare Cooksley, Mahnaz Ramezanpour, Sophia Moraitis ... Sarah Vreugde ... et al