Quick-closing valve is actuated by explosive discharge

Remotely controlled plug-type valve shuts off a high-pressure, high-temperature gas flow in a few milliseconds. The valve is actuated by a commercially available electrically initiated squib of low explosive power. More rapid closure is attainable with squibs containing heavier explosive changes

Fluvial Systems Tied Together Through a Common Base Level: The Geomorphic Response of the Dirty Devil River, North Wash Creek, and the Colorado River to the Rapid Base Level Drop of Lake Powell

Fluvial adjustment to base level change has its roots in the fundamental concepts of geomorphology. This thesis explores the rate of erosion and sedimentation on the Colorado and Dirty Devil rivers and North Wash Creek under the current base level changes related to the drawdown conditions of Lake Powell. Through cross section and long profile resurveys, the current state of each system is captured and added to the historic record of sedimentation in Lake Powell. All three systems are generally forming narrow and deep incised channels driven by the rapid rate of base level fall. Cross sections that deviate from this are due to site-specific factors, such as channel armoring, the presence of local base levels, or bedrock canyon width in relation to active channel width. In all systems, sediment is being transported through the establishing fluvial regime and is deposited at or below the new base level. This has caused rapid downstream progradation of each delta front. The volume of sediment accumulation and erosion and rates through time are calculated for each system. Deposit volume is proportional to each systems drainage basin area, as are the rates and magnitudes of deposition and erosion. The percentage of sediment eroded versus deposited shows an inverse relationship, with North Wash eroding the greatest percentage of its delta. Field observations and repeat photography on the distribution, orientation, and activity of lateral slumping and mud cracks identify that thick beds of fine-grained and cohesive silts and clays are necessary for these features to form. These features act to destabilize sediment and, in the case of bank failure, deliver it directly to the channel

Super-Fermi Acceleration in Multiscale MHD Reconnection

We investigate the Fermi acceleration of charged particles in 2D MHD anti-parallel plasmoid reconnection, finding a drastic enhancement in energization rate $\dot{\varepsilon}$ over a standard Fermi model of $\dot{\varepsilon} \sim \varepsilon$. The shrinking particle orbit width around a magnetic island due to $\vec{E}\times\vec{B}$ drift produces a $\dot{\varepsilon}_\parallel \sim \varepsilon_\parallel^{1+1/2\chi}$ power law with $\chi \sim 0.75$. The increase in the maximum possible energy gain of a particle within a plasmoid due to the enhanced efficiency increases with the plasmoid size, and is by multiple factors of 10 in the case of solar flares and much more for larger plasmas. Including effects of the non-constant $\vec{E}\times\vec{B}$ drift rates leads to further variation of power law indices from $\gtrsim 2$ to $\lesssim 1$, decreasing with plasmoid size at the time of injection.Comment: 7 pages, 7 figure

NSAIDs and Their Interactions with Bacterial Growth

Non-steroidal anti-inflammatory drugs (NSAIDs) are common medications that are frequently used to suppress symptoms of viral and bacterial infections. The increase in concern of antibiotic resistance has led researchers to study the effects of NSAIDs on bacterial growth or on common antibiotics. This study aims to determine whether commonly used NSAIDs, ibuprofen and acetaminophen, have any antibacterial properties that might help suppress bacterial growth. In conjunction, this study also looks to see whether the combination of NSAIDs and an antibiotic can further reduce bacterial growth than if an antibiotic is used alone. Our procedure consisted of lab-grown Escherichia coli (E. coli) that was mixed with ibuprofen (8ug/ml), acetaminophen (15ug/ml), or ampicillin at either 8 or 15ug/ml. These concentrations are based on typical blood serum levels of each respective drug. UV spectrophotometer was used to determine bacterial growth through absorbance values (600nm). The results show larger absorbance values (meaning greater bacterial growth) when ibuprofen and acetaminophen are present. Data also shows that when NSAIDs are used in combination with ampicillin, absorbance values would be greater than if ampicillin was used alone. Possible mechanisms leading to these results could include horizontal gene transfer in E. coli or inhibiting the antibiotic effects of ampicillin. Future research should focus on determining the primary mechanism NSAIDs use to promote bacterial growth or inhibit antibiotics

Direct electron heating at moderate harmonic number for compact ignition devices

Direct electron heating of compact ignition devices by radio-frequency power in the 300-400 MHz,range is discussed. The possible advantage of this approach to heating an ignition device, as opposed to resonant heating of an ion population, is the insensitivity to the exact value of the magnitude field. Heating with central power deposition during a toroidal field ramp is therefore possible

Asymmetric Power Among Agents and the Generation and Maintenance of Cooperation in International Relations

The question addressed in this analysis is whether endowing agents with various forms of asymmetric power makes cooperation more likely across a variety of structural settings of conflict and cooperation present in international relations. To address this question, an agent-based model incorporating asymmetric power among agents in a set of (2 Â 2) games that represent different forms of conflict and cooperation prevalent in international relations (Chicken, Stag, Assurance, Deadlock, and Prisoner's Dilemma) is developed and analyzed via simulation. Simulation results indicate that the introduction of asymmetric power substantially increases the chances that both cooperative agents survive and cooperative worlds evolve. This is particularly the case when agents are endowed with the ability to selectively interact with other agents. Also, anticipated variations in outcomes across the game structures regarding the likelihood of cooperation are supported. Whether and how cooperation evolves in social settings characterized by the presence of selfish agents engaged in repeated relations without central authority has been of considerable importance to scholars of international politics and of interest to scholars across all the social sciences as well as philosophy, biology, and computer science. 1 International relations scholars have been particularly interested in various features of nation-states, the relations among nation-states, and the structural environment in which nation-states are embedded that make cooperation either possible or more likely. Studying the evolution of cooperation in the context of the Repeated Prisoner's Dilemma (RPD) has proven to be quite fruitful for international relations scholars. Yet, the RPD framework is also restrictive in a variety of ways. 3 For instance, while the RPD captures one important type of relationship among nation-states in the international system, there are a number of other structural settings that (1984), the Repeated Prisoner's Dilemma (RPD) has become the central metaphor for the evolution of cooperation in populations of selfish agents without central authority

Photoresponse of PbS nanoparticles-quaterthiophene films prepared by gaseous deposition as probed by XPS

Cataloged from PDF version of article.Semiconducting lead sulfide (PbS) nanoparticles were cluster beam deposited into evaporated quaterthiophene (4T) organic films, which in some cases were additionally modified by simultaneous 50 eV acetylene ion bombardment. Surface chemistry of these nanocomposite films was first examined using standard x-ray photoelectron spectroscopy (XPS). XPS was also used to probe photoinduced shifts in peak binding energies upon illumination with a continuous wave green laser and the magnitudes of these peak shifts were interpreted as changes in relative photoconductivity. The four types of films examined all displayed photoconductivity: 4T only, 4T with acetylene ions, 4T with PbS nanoparticles, and 4T with both PbS nanoparticles and acetylene ions. Furthermore, the ion-modified films displayed higher photoconductivity, which was consistent with enhanced bonding within the 4T organic matrix and between 4T and PbS nanoparticles. PbS nanoparticles displayed higher photoconductivity than the 4T component, regardless of ion modification. (C) 2012 American Vacuum Society