Gamma ray production in paraffin by cosmic rays

Gamma ray production in paraffin by cosmic ray

Solar gamma ray monitor for OSO-H (0.3-10 MeV)

A gamma ray experiment to be flown aboard the OSO-7 spacecraft is described along with a history of the development of the experiment, a description of the gamma ray detector and its operation, and a short preliminary review of the scientific information obtained during the instruments' lifetime. The gamma ray detector operated an average of 18 hours a day for approximately 15 months. The majority of the data was collected in the solar and antisolar direction, but data at right angles to the spacecraft-sun line was also accumulated. In all, at least two full scans of the celestial sphere were completed

A gamma ray monitor for the OSO-7 spacecraft

A 3 in. x 3 in. NaI(Tl) gamma ray (0.3 to 10 MeV) spectrometer with a CsI(Na) charged particle and anti-Compton shield has been developed for the Orbiting Solar Observatory (OSO-7) which was launched September 30, 1971. The instrument, designed for a rotating wheel compartment, utilizes a 377 channel quadratic PHA with accumulation times of 3, 1, or 0.5 minutes. Quick look and calibration data obtained via a direct data link to a minicomputer allows near real time monitoring and control of the experiment. Various commands changing the operating mode can be executed. The functions which can be commanded include: rotation of the quadrants in which data is collected by 90 deg; gain adjustment of the central detector over a 6:1 range; manual or automatic sequencing of calibrations; variations of accumulation times by telemetering selected channels; and selection of reference directions. A small X-ray detector covering the range 7.5 to 120 keV is also included

SMM detection of interstellar Al-26 gamma radiation

The gamma ray spectrometer on the Solar Maximum Mission Satellite has detected the interstellar Al-26 line when the Galactic center traversed its aperture. The center of the emission is consistent with the location of the Galactic center, but the spatial distribution is presently not well defined. The total flux in the direction of the Galactic center is 4.3 + or - 0.4) x .0001 gamma/sq cm-s-rad for an assumed population I distribution

Documentation of the data analysis system for the gamma ray monitor aboard OSO-H

The programming system is presented which was developed to prepare the data from the gamma ray monitor on OSO-7 for scientific analysis. The detector, data, and objectives are described in detail. Programs presented include; FEEDER, PASS-1, CAL1, CAL2, PASS-3, Van Allen Belt Predict Program, Computation Center Plot Routine, and Response Function Programs

Predicting Multi-trophic Consequences of an Emerging Disease

There are numerous examples of how exotic insect pests and pathogens have altered the dominance of native tree species and the ecological processes and function related to those species. While targeted species may persist in a functionally altered state via vegetative sprouting, the widespread decimation of a species can have dramatic direct and indirect consequences for organisms in multiple trophic levels. Devastation due to alien insect herbivores poses the greatest threat to native insect larvae that specialize on the impacted host species. The loss of pollinators whose larvae feed on impacted species and provide services for native plants may also be a serious but yet undocumented indirect threat of these exotic invasions. The disruption of mutualistic relationships between native species will have negative consequences for those species and could potentially benefit exotic species. In the southeastern US, laurel wilt disease (LWD) is impacting numerous species in the Lauraceae family, with the majority of cases observed on Persea borbonia, a common sub-canopy tree found in many Coastal Plain habitats. This species is also known to be the primary larval host of the palamedes swallowtail (Papilio palamedes). While infection rates and crown dieback are catastrophically high (\u3e90%), basal resprouting is a common response in P. borbonia. The exotic Cinnamomum camphora is the only Lauraceae species that has shown resistance to LWD and could benefit from opportunities to replace P. borbonia and other Lauraceae species threatened by LWD. The primary objectives of this study were four fold: 1) to quantify P. borbonia sprouting responses in the field and greenhouse and determine the effect of P. borbonia removal on the composition and abundance of woody and herbaceous plant species in the understory layer, 2) to test the relative suitability of C. camphora as an alternative larval host for P. palamedes, 3) to determine the reliance of the Platanthera ciliaris on P. palamedes for successful pollination and the relative availability of alternative long-tongued pollinators, and 4) to forecast how disease-induced shifts in the relative abundance of native (P. borbonia) and exotic (C. camphora) fruit may alter patterns of consumption and subsequent dispersal of C. camphora by birds. The field component (Grand Bay National Estuarine Research Reserve (GBNERR), Jackson County, MS) of chapter two involved the removal of P. borbonia main stems to mimic the impacts of LWD which resulted in a significant increase (~50%) in light transmission. All treated individuals produced sprouts and the size and number of sprouts was positively related to initial tree size. Following the removal of P. borbonia from treatment plots, Ilex vomitoria showed the greatest increase in basal area after two years. Both woody seedlings and herbaceous plants showed no significant trends in composition and/or abundance over time. In the greenhouse (Southern Illinois University, Carbondale, IL), the stem and leaf biomass of vegetative sprouts was significantly greater in a high-nutrient treatment. Light treatments had no effect on sprout production. Results from chapter two suggest that the loss of P. borbonia from the canopy layer may have little direct effect on plant community dynamics. In addition, I found that sprout production is vigorous in P. borbonia and the capacity to persist and tolerate future disturbances may be enhanced on more nutrient-rich sites. In chapter three, I used laboratory experiments and field observations to compare larval performance and adult female preference of P. palamedes between C. camphora and P. borbonia foliage. My results indicate moderate survivorship on C. camphora (46%) compared to P. borbonia (87%) and there were no differences in first and fourth instar growth rates between treatments. Fourth instars consumed less C. camphora foliage than P. borbonia, but metabolic efficiency did not differ between treatments. In the field and laboratory, I found no oviposition preference for C. camphora relative to P. borbonia. While females laid eggs on C. camphora during laboratory trials, the same number of eggs was also laid on inanimate objects. I conclude that C. camphora is suitable for larval development but host-switching to this species by P. palamedes will be primarily constrained by oviposition behaviors. In chapter four, I monitored pollinator visitation and measured nectar spur lengths of P. ciliaris flowers and proboscis lengths of its floral visitors (at GBNERR). Papilio palamedes was the primary visitor (44 visits) but Phoebis sennae was also observed (4 visits). There were no significant differences among P. ciliaris nectar spurlength and the proboscis lengths of P. palamedes and P. sennae. Fruit set was 55 ± 10.8% with access to pollinators and 0% on bagged inflorescences (pollinators excluded). Although I found a positive relationship between visitation and inflorescence size, there was no such pattern in fruit set, indicating that fruit set was not limited by pollinator visitation within the range of visitation rates I observed. Phoebis sennae may provide supplemental pollination service but is likely constrained by habitat preferences that do not always overlap with those of P. cilaris. Although additional observations are needed, my results suggest that expected LWD-induced declines of P. palamedes will threaten the reproductive success and persistence of P. ciliaris populations. In chapter five, I investigated redundancy between C. camphora and P. borbonia with respect to fruit characteristics (physical and chemical) and selectivity by frugivorous birds (at GBNERR). Across two winter survey periods I observed fruit removal from artificial infructescences. I manipulated background species upon which displays were hung (Myrica cerifera and Triadica sebifera) and the accessibility of the displays. Using motion-activated cameras I confirmed foraging bouts on both P. borbonia and C. camphora fruits by three bird species (Dumetella carolinensis, Turdus migratorius, and Catharus guttatus). There was no significant difference in selectivity between fruit types during year one of my surveys but there was a significant preference for C. camphora in year two, which coincided with significantly lower mean daily temperatures. Background tree species and accessibility had no apparent effect on fruit preference. Total polyphenols and pulp:seed ratio were significantly higher in C. camphora fruit. I conclude that the fruits of C. camphora and P. borbonia represent nearly substitutable resources for native birds. However, native species may prefer C. camphora fruit in times of energetic stress. The decline of P. borbonia will likely increase the consumption and dispersal of C. camphora fruits. Additional studies are required to determine if such changes could ultimately increase the distribution and abundance of this exotic species. Combined, the chapters of this dissertation present substantial empirical evidence for the potential multi-trophic level impacts of an exotic plant disease. While it remains unclear how dramatic these impacts will be, the approach used here is vital for understanding and mitigating the long-term ecological effects of species/disease invasions

Neutral pion production in solar flares

The Gamma-Ray Spectrometer (GRS) on SMM has detected more than 130 flares with emission approx 300 keV. More than 10 of these flares were detected at photon energies 10 MeV. Although the majority of the emission at 10 MeV must be from electron bremsstrahlung, at least two of the flares have spectral properties 40 MeV that require gamma rays from the decay of neutral pions. It is found that pion production can occur early in the impulsive phase as defined by hard X-rays near 100 keV. It is also found in one of these flares that a significant portion of this high-energy emission is produced well after the impulsive phase. This extended production phase, most clearly observed at high energies, may be a signature of the acceleration process which produces solar energetic particles (SEP's) in space

Search for gamma ray lines from SS433

Data obtained with the Gamma Ray Spectrometer (0.3 to 9 MeV) aboard the Solar Maximum Mission satellite from 1980 to 1985 for evidence of the reported Doppler shifted lines from SS433 were examined. The data base covers a total of 468 days when SS433 was in the field of view and includes times of quiescent and flaring radio activity. In 9 day integrations of the SMM data no evidence is found for gamma ray line emission from SS433. The 99% confidence upper limits for 9 day integrations of the shifted 1.37 and 6.1 MeV lines are 0.0013 gamma/sq cm-s and 0.0007 gamma/sq cm-s, respectively. The 360 day time averaged upper limits are 0.0002 gamma/sq cm-s x 0.0001 gamma/sq cm-s for both lines

Orchid–pollinator Interactions and Potential Vulnerability to Biological Invasion

Mutualistic relationships between plants and their pollinators have played a major role in the evolution of biodiversity. While the vulnerability of these relationships to environmental change is a major concern, studies often lack a framework for predicting impacts from emerging threats (e.g. biological invasions). The objective of this study was to determine the reliance of Platanthera ciliaris (orange-fringed orchid) on Papilio palamedes (Palamedes swallowtail butterfly) for pollination and the relative availability of alternative pollinators. Recent declines of P. palamedes larval host plants due to laurel wilt disease (LWD) could endanger P. ciliaris populations that rely heavily on this butterfly for pollination.We monitored pollinator visitation and fruit set and measured nectar spur lengths of P. ciliaris flowers and proboscis lengths of its floral visitors in Jackson County, MS, USA. Papilio palamedes was the primary visitor with minimal visitation by Phoebis sennae (cloudless sulfur butterfly). Lengths of P. ciliaris nectar spurs were similar to proboscis lengths of both pollinator species. Fruit set was moderate with access to pollinators (55+10.8 %), yet failed (0 %) when pollinators were excluded. Visitation increased with inflorescence size, but there was no such pattern in fruit set, indicating that fruit set was not limited by pollinator visitation within the range of visitation rates we observed. Our results are supported by historical data that suggest P. palamedes and P. sennae are important pollinators of P. ciliaris. Although P. sennae may provide supplemental pollination service, this is likely constrained by habitat preferences that do not always overlap with those of P. cilaris. Observed declines of P. palamedes due to LWD could severely limit the reproductive success and persistence of P. ciliaris and similar orchid species populations. This empirical-based prediction is among the first to document exotic forest pests and pathogens as an indirect threat to plant–pollinator interactions

Monte Carlo calibration of the SMM gamma ray spectrometer for high energy gamma rays and neutrons

The Gamma Ray Spectrometer (GRS) on the Solar Maximum Mission spacecraft was primarily designed and calibrated for nuclear gamma ray line measurements, but also has a high energy mode which allows the detection of gamma rays at energies above 10 MeV and solar neutrons above 20 MeV. The GRS response has been extrapolated until now for high energy gamma rays from an early design study employing Monte Carlo calculations. The response to 50 to 600 MeV solar neutrons was estimated from a simple model which did not consider secondary charged particles escaping into the veto shields. In view of numerous detections by the GRS of solar flares emitting high energy gamma rays, including at least two emitting directly detectable neutrons, the calibration of the high energy mode in the flight model has been recalculated by the use of more sophisticated Monte Carlo computer codes. New results presented show that the GRS response to gamma rays above 20 MeV and to neutrons above 100 MeV is significantly lower than the earlier estimates