Reduction and analysis of data collected during the electromagnetic tornado experiment

Progress is reviewed on the reduction and analysis of tornado data collected on analog tape. The strip chart recording of 7 tracks from all available analog data for quick look analysis is emphasized

Determination of mass outflow from a thunderstorm complex using ATS 3 pictures

Satellite cloud photography for determining mass outflow and tornado formatio

U.S. East Coast Trough Indices at 500 hPa and New England Winter Climate Variability

Using monthly gridded 500-hPa data, two synoptic indices are defined to better understand the principle mechanisms controlling intraseasonal to multiannual winter climate variability in NewEngland (NE). The “trough axis index” (TAI) is created to quantify the mean longitudinal position of the common East Coast pressure trough, and the “trough intensity index” (TII) is calculated to estimate the relative amplitude of this trough at 42.5°N. The TAI and TII are then compared with records for NE regional winter precipitation, temperature, and snowfall with the goal of understanding physical mechanisms linking NE winter climate with regional sea surface temperatures (SST), the North Atlantic Oscillation (NAO), and the Pacific–North American (PNA) teleconnection pattern. The TAI correlates most significantly with winter precipitation at inland sites, such that a western (eastern)trough axis position is associated with greater (lower) average monthly precipitation. Also, significant correlations between the TAI and both NE regional SSTs and the NAO suggest that longitudinal shifting of the trough is one possible mechanism linking the North Atlantic with NE regional winterclimate variability. The NE winter temperature is significantly correlated with the TII, regional SSTs, and the NAO. While the PNA also correlates with the TII, NE winter climate variables are apparently unrelated to the PNA index

Chemistry of Tropical Root Crops: Significance for Nutrition and Agriculture in the Pacific

Crop Production/Industries,

Upper Limits on the Extragalactic Background Light from the Gamma-Ray Spectra of Blazars

The direct measurement of the extragalactic background light (EBL) is difficult at optical to infrared wavelengths because of the strong foreground radiation originating in the Solar System. Very high energy (VHE, E$>$100 GeV) gamma rays interact with EBL photons of these wavelengths through pair production. In this work, the available VHE spectra from six blazars are used to place upper limits on the EBL. These blazars have been detected over a range of redshifts and a steepening of the spectral index is observed with increasing source distance. This can be interpreted as absorption by the EBL. In general, knowledge of the intrinsic source spectrum is necessary to determine the density of the intervening EBL. Motivated by the observed spectral steepening with redshift, upper limits on the EBL are derived by assuming that the intrinsic spectra of the six blazars are $\propto E^{-1.8}$. Upper limits are then placed on the EBL flux at discrete energies without assuming a specific spectral shape for the EBL. This is an advantage over other methods since the EBL spectrum is uncertain.Comment: 33 pages, 14 figures, accepted by Ap

Between Thought and Expression, a Magnetoencephalography Study of the "Tip-of-the-Tongue" Phenomenon

“Tip-of-the-tongue” (TOT) is the phenomenon associated with the inaccessibility of a known word from memory. It is universally experienced, increases in frequency with age, and is most common for proper nouns. It is a good model for the symptom of anomia experienced much more frequently by some aphasic patients following brain injury. Here, we induced the TOT state in older participants while they underwent brain scanning with magnetoencephalography to investigate the changes in oscillatory brain activity associated with failed retrieval of known words. Using confrontation naming of pictures of celebrities, we successfully induced the TOT state in 29% of trials and contrasted it with two other states: “Know” where the participants both correctly recognized the celebrity's face and retrieved their name and “Don't Know” when the participants did not recognize the celebrity. We wished to test Levelt's influential model of speech output by carrying out two analyses, one epoching the data to the point in time when the picture was displayed and the other looking back in time from when the participants first articulated their responses. Our main findings supported the components of Levelt's model, but not their serial activation over time as both semantic and motor areas were identified in both analyses. We also found enduring decreases in the alpha frequency band in the left ventral temporal region during the TOT state, suggesting ongoing semantic search. Finally, we identified reduced beta power in classical peri-sylvian language areas for the TOT condition, suggesting that brain regions that encode linguistic memories are also involved in their attempted retrieval

Carbon flux on coral reefs: effects of large shifts in community structure

The effect of replacement of live coral cover by epilithic algae on patterns and magnitudes of carbon flux is examined for the shallow front slope of a midshelf reef in the Great Barrier Reef (GBR) complex of Australia. A steady-state network of carbon exchange among 19 trophic compartments is constructed for the coral-dominated state. From this, 2 scenarios for patterns of carbon flux when algae dominate are derived, viz. (1) the increase in algal production is channeled to detrital pathways (grazers do not respond), and (2) grazers utilise the increase in production of algal carbon so that transfers to detritus and grazers are in the same proportion as occurs when coral cover is high. The 3 models summarise current knowledge of carbon flux on GBR reef fronts and are compared using network analysis. Because fluxes in the reef front zone are dominated by exogenous imports and exports as a result of the high volume of water passing around and over the reef, the analyses ignore advective fluxes across the zone that are not internalised.The shift in structure to an algae-dominated system realises lower rates of benthic primary production, and thus system slze and activity (i.e. total system throughput, internal throughput, development capacity and ascendancy) are reduced, suggest- ing a disturbed system. With loss of coral cover, the proportion of the total flow that is recycled and transferred to the detritus pool increases (although the structure of recycling is not affected), and the balance of pathways in the network is changed: average path length increases, while the average trophic level of most of the second order consumers, and trophic efiiciencies of most trophic categories, decreases. Also, there are marked changes in dependencies of particular trophic groups on others. The analysis shows that, in the coral-dominated state, carbon fixed by zooxanthellae is used indirectly by most organisms in the system, even those seemingly remotely connected. Differences between the coral- and algae-dominated systems were much greater than differences between the 2 scenarios for the algae-dominated state. However, the exact fate of additional algae-derived carbon In the system is an important consideration since the 2 scenarios for the algae-dominated state yielded dissimilar values for some parameters (e.g. flow diversity, trophic dependencies and effective trophic levels of some com- partments, relative importance of recycling, trophic efficiency of some trophic categories)

Multiwavelength Observations of a Flare from Markarian 501

We present multiwavelength observations of the BL Lacertae object Markarian 501 (Mrk 501) in 1997 between April 8 and April 19. Evidence of correlated variability is seen in very high energy (VHE, E > 350 GeV) gamma-ray observations taken with the Whipple Observatory gamma-ray telescope, data from the Oriented Scintillation Spectrometer Experiment of the Compton Gamma-Ray Observatory, and quicklook results from the All-Sky Monitor of the Rossi X-ray Timing Explorer while the Energetic Gamma-Ray Experiment Telescope did not detect Mrk 501. Short term optical correlations are not conclusive but the U-band flux observed with the 1.2m telescope of the Whipple Observatory was 10% higher than in March. The average energy output of Mrk 501 appears to peak in the 2 keV to 100 keV range suggesting an extension of the synchrotron emission to at least 100 keV, the highest observed in a blazar and ~100 times higher than that seen in the other TeV-emitting BL Lac object, Mrk 421. The VHE gamma-ray flux observed during this period is the highest ever detected from this object. The VHE gamma-ray energy output is somewhat lower than the 2-100 keV range but the variability amplitude is larger. The correlations seen here do not require relativistic beaming of the emission unless the VHE spectrum extends to >5 TeV.Comment: 10 pages, 2 figures, accepted for publication in ApJ Letter