Publications by authors named "J Andrew Schaber"

Castleman disease (CD) is a rare, benign lymphoproliferative disorder with characteristic histopathological features, but variable aetiology, presentation, treatment and prognosis. It is broadly classified based on its location and histopathological features, with unicentric hyaline vascular disease presenting most commonly. We present a case of primary, unicentric hepatic CD that was incidentally found on imaging and managed with laparoscopic resection.

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Concentrations of microplastics in aquatic environments continue to rise due to industrial production and pollution. While there are various concerns regarding potential deleterious effects of microplastics on ecosystems, several knowledge gaps remain, including the potential for microplastics to directly and indirectly affect biotic interactions and food web dynamics. We explored the effects of environmentally relevant microplastic concentrations on two co-exposed species of herbaceous freshwater crustaceous zooplankton, filter feeding Daphnia dentifera and selective phytoplankton grazers Arctodiaptomus dorsalis.

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Article Synopsis
  • This study investigates how residual carbon on p-GaN photocathodes affects their quantum efficiency, emphasizing the importance of a clean surface for achieving negative electron affinity.
  • The research utilizes an in-situ X-ray photoelectron spectrometer (XPS) to monitor changes on the photocathode surface during cleaning, activation, and degradation processes.
  • Despite the presence of carbon and oxygen contaminants from the manufacturing process, activating p-GaN with cesium allows for the formation of negative electron affinity and reveals the role of cesium carbide in photocathode performance degradation.
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As is well known, the quality of the photocathodes is essential for the stability and reliability of photoinjector operations. Especially for superconducting radio frequency photoinjectors (SRF guns), the photocathode represents one of the most critical parts. Benefiting from the fast development of photocathode technology in recent years, several SRF guns have been successfully operated or tested for beam generation at the kHz-MHz repetition rate.

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Article Synopsis
  • Accelerator scientists require photocathodes with high quantum efficiency (QE) and durability; p-GaN photocathodes, enhanced with cesium, have emerged as promising candidates due to their negative electron affinity surface.* -
  • In this study, p-GaN samples were cleaned and activated in an ultra-high vacuum (UHV) chamber, with subsequent analysis of their performance and surface characteristics using various microscopic techniques.* -
  • Results indicate that both wet chemical and thermal cleaning processes affect the cathodes' quality, but high QE and long storage life can be achieved at lower cleaning temperatures.*
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