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  1. Free, publicly-accessible full text available January 1, 2023
  2. Free, publicly-accessible full text available February 1, 2023
  3. Humans understand videos from both the visual and audio aspects of the data. In this work, we present a self supervised cross modal representation approach for learning audio visual correspondence (AVC) for videos in the wild. After the learning stage, we explore retrieval in both cross modal and intra modal manner with the learned representations. We verify our experimental results on the VGGSound dataset and our approach achieves promising results.
  4. Free, publicly-accessible full text available December 15, 2022
  5. Among high-valence metal oxides, LiCoO 2 and related materials are of environmental importance because of the rapidly increasing use of these materials as cathodes in lithium ion batteries. Understanding the impact of these materials on aqueous environments relies on understanding their redox chemistry because Co release is dependent on oxidation state. Despite the critical role that redox chemistry plays in cellular homeostasis, the influence of specific biologically relevant electron transporters such as nicotinamide adenine dinucleotide (NADH) and glutathione (GSH) on the transformation of engineered nanoparticles has not been widely considered previously. Here we report an investigation of the interaction of LiCoO 2 nanoparticles with NADH and GSH. Measurements of Co release using inductively coupled plasma-mass spectrometry (ICP-MS) show that exposing LiCoO 2 nanoparticles to either NADH or GSH increases solubilization of cobalt, while corresponding spectroscopic measurements show that NADH is concurrently oxidized to NAD + . To demonstrate that these effects are a consequence the high-valence Co(III) inLiCoO 2 nanoparticles, we performed control experiments using Co(II)-containing Co(OH) 2 and LiCoPO 4 , and dissolved Co 2+ /Li + ions. Additional experiments using molecules of similar structure to NADH and GSH, but that are not reducing agents, confirm that these transformationsmore »are driven by redox reactions and not by chelation effects. Our data show that interaction of LiCoO 2 with NADH and GSH induces release Co 2+ ions and alters the redox state of these biologically important transporters. Observation of NADH binding to LiCoO 2 using x-ray photoelectron spectroscopy (XPS) suggests a surface catalyzed reaction. The reciprocal reduction of LiCoO 2 to enable release of Co 2+ and corresponding oxidation of NADH and GSH as model redox-active biomolecules has implications for understanding the biological impacts of high-valence metal oxide nanomaterials.« less
  6. Lithium cobalt oxide (LiCoO 2 ), an example of nanoscale transition metal oxide and a widely commercialized cathode material in lithium ion batteries, has been shown to induce oxidative stress and generate intracellular reactive oxygen species (ROS) in model organisms. In this study, we aimed to understand the time-dependent roles of abiotic ROS generation and Co ions released in aqueous medium by LiCoO 2 NPs, and examined the induced biological responses in model bacterium, B. subtilis upon exposure. We found that the redox-active LiCoO 2 NPs produced abiotic ROS primarily through H 2 O 2 generation when freshly suspended. Subsequently, the freshly-suspended LiCoO 2 NPs induced additional DNA breakage, and changes in expression of oxidative stress genes in B. subtilis that could not be accounted for by the released Co ions alone. Notably, in 48 hour old LiCoO 2 suspensions, H 2 O 2 generation subsided while higher concentrations of Co ions were released. The biological responses in DNA damage and gene expression to the aged LiCoO 2 NPs recapitulated those induced by the released Co ions. Our results demonstrated oxidative stress mechanisms for bacteria exposed to LiCoO 2 NPs were mediated by the generation of distinct biotic and abioticmore »ROS species, which depended on the aqueous transformation state of the NPs. This study revealed the interdependent and dynamic nature of NP transformation and their biological consequences where the state of NPs resulted in distinct NP-specific mechanisms of oxidative injury. Our work highlights the need to capture the dynamic transformation of NPs that may activate the multiple routes of oxidative stress responses in cells.« less