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During explosive movements and potentially injurious situations, the ability to rapidly generate torque is critical. Previous research has suggested that different phases of rate of torque development (RTD) are differentiately controlled. However, the extent to which supraspinal and spinal mechanisms predict RTD at different time intervals is unknown. RTD of the plantarflexors across various phases of contraction (i.e., 0-25, 0-50, 0-100, 0-150, 0-200, and 0-250 ms) was measured in 37 participants. The following predictor variables were also measured: (a) gain of the resting soleus H-reflex recruitment curve; (b) gain of the resting homonymous post-activation depression recruitment curve; (c) gain of the GABAergic presynaptic inhibition recruitment curve; (d) the level of postsynaptic recurrent inhibition at rest; (e) level of supraspinal drive assessed by measuring V waves; and (f) the gain of the resting soleus M wave. Stepwise regression analyses were used to determine which variables significantly predicted allometrically scaled RTD. The analyses indicated that supraspinal drive was the dominant predictor of RTD across all phases. Additionally, recurrent inhibition predicted RTD in all of the time intervals except 0-150 ms. These results demonstrate the importance of supraspinal drive and recurrent inhibition to RTD.

A 6.1-MV, 0.79-MA laser-triggered gas switch (LTGS) is used to synchronize the 36 modules of the $Z$ machine at Sandia National Laboratories. Each module includes one switch, which serves as the last command-fired switch of the module, and hence is used to determine the time at which each module electrically closes relative to the other modules. The switch is $\ensuremath{\sim}81\mathrm{\text{\ensuremath{-}}}\mathrm{cm}$ in length, $\ensuremath{\sim}45\mathrm{\text{\ensuremath{-}}}\mathrm{cm}$ in diameter, and is immersed in mineral oil. The outer switch envelope consists of six corrugated monomer-cast acrylic insulators and five contoured stainless-steel rings. The trigger electrodes are fabricated from copper-infused tungsten. The switch is pressurized with several atmospheres of sulfur hexafluoride (${\mathrm{SF}}_{6}$), which is turbulently purged within 2 seconds after every shot. Each switch is powered from a 6-MV, 0.78-MJ Marx generator which pulse charges a 24-nF intermediate-store water capacitor in $1.4\mathrm{\text{\ensuremath{-}}}\ensuremath{\mu}\mathrm{s}$. Closure of the switch allows power to flow into pulse-forming transmission lines. The power pulse is subsequently compressed by water switches, which results in a total accelerator output power in excess of 70-TW. A previous version of the LTGS performed exceptionally at a 5.4-MV, 0.7-MA level on an engineering test module used for switch development. It exhibited a $1\mathrm{\text{\ensuremath{-}}}\ensuremath{\sigma}$ jitter of $\ensuremath{\sim}5\text{ }\text{ }\mathrm{ns}$, a prefire and flashover rate less than 0.1%, and a lifetime in excess of 150 shots. When installed on the $Z$ accelerator, however, the switch exhibited a prefire probability of $\ensuremath{\sim}3%$, a flashover probability of $\ensuremath{\sim}7%$, and a 15-ns jitter. The difference in performance is attributed to several factors such as higher total charge transfer, exposure to more debris, and more stressful dynamic mechanical loading upon machine discharge. Under these conditions, the replacement lifetime was less than ten shots. Since refurbishment of $Z$ in October 2007, there have been three LTGS design iterations to improve the performance at 6.1-MV. The most recent design exhibits a prefire rate of less than 0.1%, a flashover rate of $\ensuremath{\sim}0.2%$, a single switch jitter of $\ensuremath{\sim}6\mathrm{\text{\ensuremath{-}}}\mathrm{ns}$, and a lifetime of greater than 75 shots. Modifications to achieve the performance improvement are detailed in this article.

A recent EPA-sponsored study of sediment and seafood contamination in Quincy Bay revealed elevated levels of several complex organic pollutants frequently of concern in human health assessments. A seafood consumption risk assessment was conducted using data from samples collected in Quincy Bay in the methodology developed for EPA's Office of Marine and Estuarine Protection for such assessments. Results showed estimated plausible, upperbound excess cancer risks in the 10(-5) to 10(-2) range. These results are comparable to those found in other seafood contamination risk assessments for areas where consumption advisories and fishing restrictions were implemented. Regulatory response included consumption advisories for lobster tomalley (hepatopancreas) and other types of locally caught seafood. Uncertainties inherent in seafood risk assessment in general and for the Quincy Bay case are discussed, along with implications for further action.