The influence of ice structure on thermo-elastic waves in saline ice

We formulate a structural model of saline ice and describe a model solution describing the propagation of thermo-elastic waves. Thermo-elastic waves are excited by periodical oscillations of the ice surface temperature. The properties of these thermo-elastic waves are determined by the mean ice temperature (background temperature), the ice salinity and the amount of liquid brine trapped in closed brine pockets. Results from an experiment, measuring thermo-elastic waves in ice, performed in the UNIS cold laboratory, are described. The characteristics of these thermo-elastic waves are compared with the theory. It is shown that amount of liquid brine trapped in closed brine pockets is an important variable in describing how the ice deforms under oscillating background temperature

Acoustic emissions from in situ compression and indentation experiments on sea ice

We present results from measurement of acoustic emissions (AE) during compression and indentation of natural sea ice in situ. We show that AE amplitudes are associated with load, so that periods of loading and unloading, and cyclic oscillations in loading during indentation, can be determined from AE records as well as from load measurements. We show that AE measured during these experiments obeys Gutenberg-Richter-type scaling laws, implying that the crack distribution within the sea ice is self-similar. We show that b-values, which indicate the ratio of small cracks to large cracks, decrease during loading, tending towards a value around 1 at failure, and increase again when loading is removed. This suggests that AE can be used to measure, non-invasively, damage and healing of natural sea ice. We conclude by discussion practical applications of these results, and opportunities for further development of AE measurement as a tool for understanding cracking in ice

Acoustic emissions from in situ compression and indentation experiments on sea ice

We present results from measurement of acoustic emissions (AE) during compression and indentation of natural sea ice in situ. We show that AE amplitudes are associated with load, so that periods of loading and unloading, and cyclic oscillations in loading during indentation, can be determined from AE records as well as from load measurements. We show that AE measured during these experiments obeys Gutenberg-Richter-type scaling laws, implying that the crack distribution within the sea ice is self-similar. We show that b-values, which indicate the ratio of small cracks to large cracks, decrease during loading, tending towards a value around 1 at failure, and increase again when loading is removed. This suggests that AE can be used to measure, non-invasively, damage and healing of natural sea ice. We conclude by discussion practical applications of these results, and opportunities for further development of AE measurement as a tool for understanding cracking in ice

The flexural strength of bonded ice

Funding Information: Financial support. This research has been supported by the Publisher Copyright: © Author(s) 2021.The flexural strength of ice surfaces bonded by freezing, termed freeze bond, was studied by performing four-point bending tests of bonded freshwater S2 columnar-grained ice samples in the laboratory. The samples were prepared by milling the surfaces of two ice pieces, wetting two of the surfaces with water of varying salinity, bringing these surfaces together, and then letting them freeze under a compressive stress of about 4 kPa. The salinity of the water used for wetting the surfaces to generate the bond varied from 0 to 35 ppt (parts per thousand). Freezing occurred in air under temperatures varying from -25 to -3 degrees C over periods that varied from 0.5 to similar to 100 h. Results show that an increase in bond salinity or temperature leads to a decrease in bond strength. The trend for the bond strength as a function of salinity is similar to that presented in Timco and O'Brien (1994) for saline ice. No freezing occurs at 3 degrees C once the salinity of the water used to generate the bond exceeds similar to 25 ppt. The strength of the saline ice bonds levels off (i.e., saturates) within 6-12 h of freezing; bonds formed from freshwater reach strengths that are comparable or higher than that of the parent material in less than 0.5 h.Peer reviewe

Experimental and natural evidence of SARS-CoV- 2-infection-induced activation of type I interferon responses

Type I interferons (IFNs) are our first line of defense against virus infection. Recent studies have suggested the ability of SARS-CoV-2 proteins to inhibit IFN responses. Emerging data also suggest that timing and extent of IFN production is associated withmanifestation of COVID-19 severity. In spite of progress in understanding how SARS-CoV-2 activates antiviral responses, mechanistic studies into wild-type SARS-CoV-2-mediated induction and inhibition of human type I IFN responses are scarce. Here we demonstrate that SARS-CoV-2 infection induces a type I IFN response in vitro and inmoderate cases of COVID-19. In vitro stimulation of type I IFN expression and signaling in human airway epithelial cells is associated with activation of canonical transcriptions factors, and SARS-CoV-2 is unable to inhibit exogenous induction of these responses. Furthermore, we show that physiological levels of IFNa detected in patients with moderate COVID-19 is sufficient to suppress SARS-CoV-2 replication in human airway cells.Medicine, Faculty ofNon UBCMedicine, Department ofRespiratory Medicine, Division ofReviewedFacultyResearcherPostdoctoralGraduat