Magnetothermodynamics In SSX: Measuring The Equations Of State Of A Compressible Magnetized Plasma

Magnetothermodynamics is the study of compression and expansion of magnetized plasma with an eye toward identifying equations of state (EOSs) for magneto-inertial fusion experiments. We present recent results from Swarthmore Spheromak Experiment (SSX) experiments on the thermodynamics of compressed magnetized plasmas called Taylor states. In these experiments, we generate twisted flux ropes of magnetized, relaxed plasma accelerated from one end of a 1.5-m-long copper flux conserver and observe their compression in a closed conducting boundary installed at the other end. Plasma parameters are measured during compression. The instances of ion heating during compression are identified by constructing a pressure-volume diagram using measured density, temperature, and volume of the magnetized plasma. While we only measure compression up to 30%, we speculate that if higher compression ratios could be achieved, the compressed Taylor states could form the basis of a new kind of fusion engine. The theoretically predicted magnetohydrodynamic (MHD) and double-adiabatic [Chew-Goldberger-Low (CGL)] EOSs are compared to experimental measurements to estimate the adiabatic nature of the compressed plasma. Since our magnetized plasmas relax to an equilibrium described by MHD, one might expect their thermodynamics to be governed by the corresponding EOS. However, we find that the MHD EOS is not supported by our data. Our results are more consistent with the parallel CGL EOS suggesting that these weakly collisional plasmas have most of their proton energy in the direction parallel to the magnetic field

Magnetothermodynamics In SSX: Measuring The Equations Of State Of A Compressible Magnetized Plasma

Magnetothermodynamics is the study of compression and expansion of magnetized plasma with an eye toward identifying equations of state (EOSs) for magneto-inertial fusion experiments. We present recent results from Swarthmore Spheromak Experiment (SSX) experiments on the thermodynamics of compressed magnetized plasmas called Taylor states. In these experiments, we generate twisted flux ropes of magnetized, relaxed plasma accelerated from one end of a 1.5-m-long copper flux conserver and observe their compression in a closed conducting boundary installed at the other end. Plasma parameters are measured during compression. The instances of ion heating during compression are identified by constructing a pressure-volume diagram using measured density, temperature, and volume of the magnetized plasma. While we only measure compression up to 30%, we speculate that if higher compression ratios could be achieved, the compressed Taylor states could form the basis of a new kind of fusion engine. The theoretically predicted magnetohydrodynamic (MHD) and double-adiabatic [Chew-Goldberger-Low (CGL)] EOSs are compared to experimental measurements to estimate the adiabatic nature of the compressed plasma. Since our magnetized plasmas relax to an equilibrium described by MHD, one might expect their thermodynamics to be governed by the corresponding EOS. However, we find that the MHD EOS is not supported by our data. Our results are more consistent with the parallel CGL EOS suggesting that these weakly collisional plasmas have most of their proton energy in the direction parallel to the magnetic field

USING CALLING ACTIVITY TO PREDICT CALLING ACTIVITY: A CASE STUDY WITH THE ENDANGERED HOUSTON TOAD (BUFO [ANAXYRUS] HOUSTONENSIS)

Understanding anuran calling activity patterns is important for maximizing efficiency and value of call survey data collection and analyses. Previous studies have primarily focused on identifying and quantifying abiotic variables that influence anuran calling activity, and investigating relationships between calling activity and population estimates. In this study we investigated the use of a predictor pond approach to guide call survey effort. In this approach, calling activity at a subset of breeding sites (e.g., ponds) is used as a predictor of calling activity at additional breeding sites, with the goal being to minimize sampling effort while simultaneously maximizing sampling efficiency. We explored the efficiency of this approach using call survey data collected on the endangered Houston Toad (Bufo [Anaxyrus] houstonensis) at 15 known breeding ponds over 9 survey years. We found that if calling activity at 3 predictor ponds was used to decide if additional call surveys would occur at the remaining 12 ponds, we would have hypothetically correctly assumed calling activity was not occurring at non-predictor ponds on 92.1% of survey nights, and we would have hypothetically detected 93.9% of the total number of detected individuals over the 9 survey years. We found the predictor pond approach performed well in our case study, and believe it could be a valuable tool for many anuran monitoring programs

Fast High Resolution Echelle Spectroscopy Of A Laboratory Plasma

An echelle diffraction grating and a multianode photomultiplier tube are paired to construct a high resolution (R=lambda/delta lambda approximate to 2.5x10(4)) spectrograph with fast time response for use from the UV through the visible. This instrument has analyzed the line shape of C III impurity ion emission at 229.687 nm over the lifetime (approximate to 100 mu s) of the hydrogen plasmas produced at SSX. The ion temperature and line of sight average velocity are inferred from the observed thermal broadening and Doppler shift of the line. The time resolution of these measurements is about 1 mu s, sufficient to observe the fastest magnetohydrodynamic activity

Magnetothermodynamics: An Experimental Study Of The Equations Of State Applicable To A Magnetized Plasma

Measuring the equations of state of a compressed magnetized plasma is important for both advancing fusion experiments and understanding natural systems such as stellar winds. In this paper, we present results from our experiments on the thermodynamics of compressed magnetized plasmas; we call these studies “magnetothermodynamics.” In these experiments, we generate parcels of relaxed, magnetized plasma at one end of the linear Swarthmore Spheromak eXperimental device and observe their compression in a closed conducting boundary installed at the other end. Plasma parameters are measured during compression. Instances of ion heating during compression are identified by constructing a pressure-volume diagram using the measured density, temperature, and volume of the magnetized plasma. An axial scan of the ion temperature at upstream locations suggests that the increase in ion temperature arises due to the compression of the magnetized plasma in the conducting boundary. The theoretically predicted magnetohydrodynamic (MHD) and double adiabatic equations of state are compared with experimental measurements to estimate the adiabatic nature of the compressed plasma. The equilibrium of our magnetized plasmas is well-described by magnetohydrodynamics; however, we find that the MHD equation of state is not supported by our data. Our results are more consistent with the parallel Chew-Goldberger-Low equation of state, suggesting that there is significant anisotropy in the ion distribution function

Lidar Measurements of On-Shore Wind Diffusion

The concept to place electric power generating stations on the oceans off the coast of the United States has instilled new efforts in research for improved understanding of the diffusion properties of the atmosphere in the ocean-air interface. The Atomic Energy Commission has instigated a program by the Meteorology Group at Brookhaven National Laboratory to investigate the low level, on-shore wind systems that dominate many of the coastal regions. Analytical techniques and specialized instrumentation from previous studies at Brookhaven are being used in this new program. The Brookhaven Lidar system is used to measure some of the physical properties of the oil-fog plume originating from a portable smoke generator on a boat off the coast. The oil-fog plume is used as a tracer which can be observed, photographed and measured to determine the diffusive power of the atmosphere associated with the ocean-air interface and the discontinuities found in the ocean-land boundary. This paper will describe the program rather briefly and the oil-fog scattering measurements that have been made with the Lidar system

The resurrection of group selection as a theory of human cooperation

Two books edited by members of the MacArthur Norms and Preferences Network (an interdisciplinary group, mainly anthropologists and economists) are reviewed here. These books in large part reflect a renewed interest in group selection that has occurred among these researchers: they promote the theory that human cooperative behavior evolved via selective processes which favored biological and/or cultural group-level adaptations as opposed to individual-level adaptations. In support of this theory, an impressive collection of cross-cultural data are presented which suggest that participants in experimental economic games often do not behave as self-interested income maximizers; this lack of self-interest is regarded as evidence of group selection. In this review, problems with these data and with the theory are discussed. On the data side, it is argued that even if a behavior seems individually-maladaptive in a game context, there is no reason to believe that it would have been that way in ancestral contexts, since the environments of experimental games do not at all resemble those in which ancestral humans would have interacted cooperatively. And on the theory side, it is argued that it is premature to invoke group selection in order to explain human cooperation, because more parsimonious individual-level theories have not yet been exhausted. In summary, these books represent ambitious interdisciplinary contributions on an important topic, and they include unique and useful data; however, they do not make a convincing case that the evolution of human cooperation required group selection

Facilitation of Learning Spatial Relations among Goal Locations does not Require Visual Exposure to the Configuration of Goal Locations

Human participants searched in a virtual-environment open-field search task for four hidden goal locations arranged in a diamond configuration located in a 5 x 5 matrix. Participants were randomly assigned to one of three groups: Pattern Only, Landmark + Pattern, or Cues + Pattern. All participants experienced a Training phase followed by a Testing phase. During Training, visual cues were coincident with goal locations for the Cues + Pattern group, and a single visual cue at a non-goal location maintained a consistent spatial relationship with the goal locations for the Landmark + Pattern group. All groups were then tested in the absence of visual cues. Presence of the visual cue(s) during Training facilitated acquisition of the task, but the Landmark + Pattern group and the Cues + Pattern group did not differ when their visual cues were removed during Testing and performed superior to the Pattern Only group. Results suggest learning based upon the spatial relations among locations may not be susceptible to cue-competition effects and facilitation of learning spatial relations by visual cues does not require visual exposure to the configuration of goal locations

Far-Ultraviolet Emission from Elliptical Galaxies at z=0.33

We present far-ultraviolet (far-UV) images of the rich galaxy cluster ZwCl1358.1+6245, taken with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope (HST). When combined with archival HST observations, our data provide a measurement of the UV-to-optical flux ratio in 8 early-type galaxies at z=0.33. Because the UV flux originates in a population of evolved, hot, horizontal branch (HB) stars, this ratio is potentially one of the most sensitive tracers of age in old populations -- it is expected to fade rapidly with lookback time. We find that the UV emission in these galaxies, at a lookback time of 3.9 Gyr, is significantly weaker than it is in the current epoch, yet similar to that in galaxies at a lookback time of 5.6 Gyr. Taken at face value, these measurements imply different formation epochs for the massive ellipticals in these clusters, but an alternative explanation is a "floor" in the UV emission due to a dispersion in the parameters that govern HB morphology.Comment: 4 pages, Latex. 2 figures. Uses corrected version of emulateapj.sty and apjfonts.sty (included). Accepted for publication in ApJ Letter