Geosocial Networking: A Case from Ann Arbor, Michigan

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91626/1/Geosocial.pd

Pneumatic Networks as Geographs

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86898/1/gean826.pd

The Effects of Ultraviolet Light Exposure on the Activity of Catalase in the Coelomocytes of Sea Urchins Lytechinus variegatus and Arbacia punctulata

Many sea urchins play important ecological roles in their environments, and it is important to study the impacts of environmental stressors on their physiology. Ultraviolet radiation (UVR) exposure has significant negative impacts on marine organisms including an increase in reactive oxygen species (ROS). Oxidative damage by ROS at the cellular level can cause lipid peroxidation, DNA fragmentation, and even cell death that may result in inflammation or disease. To prevent this cellular damage, organisms generate enzymes, such as catalase, that breakdown ROS into harmless substances. Elevated catalase activities under UVB, a range of UVR from 280–315 nm, exposure have been detected for many aquatic organisms. Yet, it is unknown whether UVB exposure affects the activity of these antioxidant enzymes in many sea urchin species. Lytechinus variegatus is well known for its covering behavior in response to UVR exposure whereas Arbacia punctulata does not cover with any materials and remains fully exposed. In this study, coelomocytes of L. variegatus and A. punctulata were exposed to UVB (302 nm) for one or two hours, and catalase activity was measured using colorimetric assays. Results suggest UVB exposure decreases catalase activity in the coelomocytes of L. variegatus (p = \u3c 0.0001, t-test) and A. punctulata (p = 0.0097, t-test). Percent difference calculations found a greater percent decrease in catalase activity occurring in the coelomocytes of L. variegatus than in A. punctulata (p = 0.0485, t-test). Whether these observed differences in antioxidant activity are associated with covering behavior is yet to be determined

ac Stark shift and multiphoton-like resonances in low-frequency driven optical lattices

We suggest that Bose-Einstein condensates in optical lattices subjected to ac forcing with a smooth envelope may provide detailed experimental access to multiphoton-like transitions between ac-Stark-shifted Bloch bands. Such transitions correspond to resonances described theoretically by avoided quasienergy crossings. We show that the width of such anticrossings can be inferred from measurements involving asymmetric pulses. We also introduce a pulse tracking strategy for locating the particular driving amplitudes for which resonances occur. Our numerical calculations refer to a currently existing experimental set-up [Haller et al., PRL 104, 200403 (2010)].Comment: 5 pages, 6 figure