title: Toward a reconnection model for solar flare statistics

authors: Wheatland, M.S.

subjects: MHD—sun

abstract: A model to account for observed solar flare statistics in terms of a superposition of independent random flaring elements (assumed to be sites of magnetic reconnection in the coronal magnetic field and hence termed “separators”) is described. A separator of length  is assumed to flare as a Poisson process in time, with a rate v(l) inversely proportional to the Alfvén transit time for the structure. It is shown that a relationship ξ∞lk between the mean energy of events ξ at a separator and the separator length implies a relationship E∞Tk between individual waiting times τ and energies E of events at the separator. The most plausible K=2 model is found to be compatible with simple pictures for magnetohydrodynamic energy storage prior to magnetic reconnection in a current sheet with anomalous (turbulent) resistivity. Formal inversion of the observed flare frequency-energy distribution is shown to imply a distribution P(l) ∞l-1 of the separator lengths in active regions. A simulation confirms the basic results of the model. It is also demonstrated that a model comprising time-dependent separator numbers N=N(t) can reproduce an observed power-law tail in the flare waiting-time distribution, for large waiting times.

text: Toward a reconnection model for solar flare statistics A model to account for observed solar flare statistics in terms of a superposition of independent random flaring elements (assumed to be sites of magnetic reconnection in the coronal magnetic field and hence termed “separators”) is described. A separator of length  is assumed to flare as a Poisson process in time, with a rate v(l) inversely proportional to the Alfvén transit time for the structure. It is shown that a relationship ξ∞lk between the mean energy of events ξ at a separator and the separator length implies a relationship E∞Tk between individual waiting times τ and energies E of events at the separator. The most plausible K=2 model is found to be compatible with simple pictures for magnetohydrodynamic energy storage prior to magnetic reconnection in a current sheet with anomalous (turbulent) resistivity. Formal inversion of the observed flare frequency-energy distribution is shown to imply a distribution P(l) ∞l-1 of the separator lengths in active regions. A simulation confirms the basic results of the model. It is also demonstrated that a model comprising time-dependent separator numbers N=N(t) can reproduce an observed power-law tail in the flare waiting-time distribution, for large waiting times.

year: 2003-09

title: Synthesis, biological evaluation, and structure−activity relationships of dithiolethiones as inducers of cytoprotective phase 2 enzymes

authors: Munday, Rex

subjects: dithiolethiones

abstract: Dithiolethiones are a family of promising cancer chemopreventive agents, and induction of phase 2 enzymes is key to their chemopreventive activities. Two dithiolethiones have been evaluated in humans for cancer prevention. While some chemopreventive activities were detected in several human studies, potential side effects are a concern. Herein, we report structure−activity relationships of 25 dithiolethiones. Several compounds show exceedingly potent and bladder specific activity in phase 2 enzyme induction. Structural features responsible for such activity, as well as those inhibiting the activity, are discussed. Moreover, the compounds activate and depend on Nrf2 for their inductive activities. Nrf2 is a major transcriptional stimulator of cytoprotective genes and is critical for cancer prevention. Thus, several new dithiolethiones that are highly promising for bladder cancer prevention have been identified. Because the compounds act specifically in the bladder, the likelihood of potential systemic toxicity may be low.

text: Synthesis, biological evaluation, and structure−activity relationships of dithiolethiones as inducers of cytoprotective phase 2 enzymes Dithiolethiones are a family of promising cancer chemopreventive agents, and induction of phase 2 enzymes is key to their chemopreventive activities. Two dithiolethiones have been evaluated in humans for cancer prevention. While some chemopreventive activities were detected in several human studies, potential side effects are a concern. Herein, we report structure−activity relationships of 25 dithiolethiones. Several compounds show exceedingly potent and bladder specific activity in phase 2 enzyme induction. Structural features responsible for such activity, as well as those inhibiting the activity, are discussed. Moreover, the compounds activate and depend on Nrf2 for their inductive activities. Nrf2 is a major transcriptional stimulator of cytoprotective genes and is critical for cancer prevention. Thus, several new dithiolethiones that are highly promising for bladder cancer prevention have been identified. Because the compounds act specifically in the bladder, the likelihood of potential systemic toxicity may be low.

year: 2010

title: Kuta (Eleocharis sphacelata, Cyperaceae), a locally important and highly valued weaving plant

authors: Wehi, Priscilla M.

subjects: Northland (N.Z.)

abstract: This article introduces and discusses kuta (Eleocharis sphacelata, Cyperaceae), a tall spikerush found on the margins of shallow lakes in New Zealand, which, although often overlooked, is considered in Northland to be a valuable weaving resource.

text: Kuta (Eleocharis sphacelata, Cyperaceae), a locally important and highly valued weaving plant This article introduces and discusses kuta (Eleocharis sphacelata, Cyperaceae), a tall spikerush found on the margins of shallow lakes in New Zealand, which, although often overlooked, is considered in Northland to be a valuable weaving resource.

year: 2006