Single-charge tunneling is a decoherence mechanism affecting superconducting qubits, yet the origin of excess quasiparticle excitations (QPs) responsible for this tunneling in superconducting devices ...is not fully understood. We measure the flux dependence of charge-parity (or, simply, “parity”) switching in an offset-charge-sensitive transmon qubit to identify the contributions of photon-assisted parity switching and QP generation to the overall parity-switching rate. The parity-switching rate exhibits a qubit-state-dependent peak in the flux dependence, indicating a cold distribution of excess QPs that are predominantly trapped in the low-gap film of the device. Moreover, we find that the photon-assisted process contributes significantly to both parity switching and the generation of excess QPs by fitting to a model that self-consistently incorporates photon-assisted parity switching as well as interfilm QP dynamics.
The risk of photoactivated PAH toxicity in contaminated aquatic systems has not been well characterized. To document risk, amphipods (Gammarus spp.) were collected from two polycyclic aromatic ...hydrocarbon (PAH)‐contaminated sites in the lower St. Louis River and Duluth Harbor, USA (Hog Island and USX) as well as a reference site (Chipmunk Cove) and were exposed in two separate, replicate tests to controlled intensities of solar radiation for 3 d. Contaminated site organisms died significantly faster compared to control site organisms. In all tests, mortality was strongly related to ultraviolet‐A (UV‐A; 320–400 nm) dose. Ultraviolet‐B (280–320 nm) radiation did not increase mortality. To compare susceptibility among populations, regressions of arcsine‐transformed, proportionate mortality versus UV dose were completed for each, and the slopes were statistically compared. Response slopes for the two contaminated site populations were both significantly greater than the reference site population (p = 0.0001 for test 1; p = 0.0002 for test 2). These results indicate that organisms residing in PAH‐contaminated environments can accumulate PAH concentrations sufficient to be at risk for photoactivated toxicity. Although amphipods are not typically at risk of PAH‐photoactivated toxicity because they are largely protected from exposure to sunlight, they are representative surrogates for species that may be similarly protected at some life stages (and thus able to accumulate significant PAH tissue concentrations) but not at others.
Selenium has been shown to reduce cancer incidence in animal models and more recent data indicate that it may be protective in humans as well. However, little is known about the mechanism by which ...selenium prevents cancer. Cytosolic glutathione peroxidase (GPX1), a selenium-containing antioxidant enzyme, has been implicated in the development of cancer of the head and neck, lung, and breast, in part because of allelic loss at the GPX1 locus. The study of allelic loss at the GPX1 locus in colon cancer was investigated by examining loss of heterozygosity (LOH) in DNA extracted from both tumor and adjacent histopathologically normal tissue obtained by laser capture microdissection. Tissue samples were obtained from 53 colon cancer patients. Two highly polymorphic markers, alanine codon repeats and a proline-leucine polymorphism (198P/L) present in the GPX1 gene, were used to examine LOH at this locus. Analysis of both polymorphisms identified LOH at GPX1 in a significant percentage of colorectal cancer (42%). These results indicated that LOH at the GPX1 locus is a common event in cancer development and that GPX1 or other tightly linked genes may be involved in the etiology of this disease.
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