title: Effects of energy threshold and dead time on Compton camera performance

authors: Uche, Chibueze Zimuzo

subjects: Compton camera

abstract: We study the effects of energy threshold and dead time on the sensitivity and image resolution of the Compton camera. The simulation model includes the decay times, detection time jitters, energy threshold and detector dead time as well as basic detector parameters such as Doppler broadening, energy resolution and finite detector resolution. The GEANT4 toolkit was used to model the camera geometry and performance for two common nuclear medicine energies that correspond to 99mTc (140.5 keV) and ¹⁸F (511 keV) radiotracers. Results without the energy threshold and time effects show good agreement with previous studies. For 140.5 keV, the inclusion of energy threshold improved image resolution from 10.7 to 9.5 mm with a source-to-detector distance of 5 cm, while the inclusion of time effects made no further difference on resolution. The energy threshold reduced the sensitivity by 48%, and subsequent inclusion of time effects further reduced the sensitivity by 17%. At 511 keV, the application of energy threshold reduced the sensitivity by 6%, while the time effects dominated count rate losses with further reduction of 13%. However, the inclusion of the two effects had negligible impact on the resolution.

text: Effects of energy threshold and dead time on Compton camera performance We study the effects of energy threshold and dead time on the sensitivity and image resolution of the Compton camera. The simulation model includes the decay times, detection time jitters, energy threshold and detector dead time as well as basic detector parameters such as Doppler broadening, energy resolution and finite detector resolution. The GEANT4 toolkit was used to model the camera geometry and performance for two common nuclear medicine energies that correspond to 99mTc (140.5 keV) and ¹⁸F (511 keV) radiotracers. Results without the energy threshold and time effects show good agreement with previous studies. For 140.5 keV, the inclusion of energy threshold improved image resolution from 10.7 to 9.5 mm with a source-to-detector distance of 5 cm, while the inclusion of time effects made no further difference on resolution. The energy threshold reduced the sensitivity by 48%, and subsequent inclusion of time effects further reduced the sensitivity by 17%. At 511 keV, the application of energy threshold reduced the sensitivity by 6%, while the time effects dominated count rate losses with further reduction of 13%. However, the inclusion of the two effects had negligible impact on the resolution.

year: 2011

title: Effect of irrigation on yield and fruit quality of rabbiteye blueberry growing on mineral soils in New Zealand

authors: Kaneko, Teruko

abstract: An experiment was conducted to determine the effect of irrigation on fruit yield and quality, and to provide recommendations for the appropriate level of irrigation for 11-year-old Vaccinium ashei Reade var. ‘Maru’ (a Rabbiteye blueberry cultivar), growing on Horotiu silt loam at Oakberry Orchard near Hamilton, New Zealand. Water was applied twice daily by drip irrigation. The treatments were no irrigation, normal irrigation (one-drip line per row), and additional irrigation (two-drip lines per row). During the observation period (November 2013 to April 2014), rainfall was below normal, particularly during fruit ripening and harvest in February and March when drought conditions created differences in soil moisture vertically and horizontally among the three treatments.

text: Effect of irrigation on yield and fruit quality of rabbiteye blueberry growing on mineral soils in New Zealand An experiment was conducted to determine the effect of irrigation on fruit yield and quality, and to provide recommendations for the appropriate level of irrigation for 11-year-old Vaccinium ashei Reade var. ‘Maru’ (a Rabbiteye blueberry cultivar), growing on Horotiu silt loam at Oakberry Orchard near Hamilton, New Zealand. Water was applied twice daily by drip irrigation. The treatments were no irrigation, normal irrigation (one-drip line per row), and additional irrigation (two-drip lines per row). During the observation period (November 2013 to April 2014), rainfall was below normal, particularly during fruit ripening and harvest in February and March when drought conditions created differences in soil moisture vertically and horizontally among the three treatments.

year: 2014

title: !!!FR33D0M 0FF SP33CH!!!

authors: Smith, Hugh Lyal

subjects: Poetry

abstract: My title is “FR33D0M 0FF SP33CH”, a play on the saying “freedom of speech”. I write with the intent of voicing tough subjects that others haven’t or don’t, and often exposing things that I wouldn’t tell or share personally. “FR33D0M 0FF SP33CH” consists of 37 poems, 2 hooks and a chorus in this complete album. My earliest piece can date back to 2020 with the latest pieces being written in 2021. They express different visions of day-to-day life through points of view and alternating voices and perspectives. The topics range from anything like seeing a face in the smudge on a wall, to things like love, street styles and why I can’t sleep at night. They are to be read left to right, top to bottom -- but feel free to read them as you see fit, because it’s art after all and what you see is what you see. Those labelled “Mirrored” have been turned upside down to allow reading from either end and show the extent of form and variety my pieces can take. Some things may be explicit or hard to read, but I assure you that they are just certain views from different angles that I believe need to be shared. There is a strong political/cultural component to my mahi, a tough vocal attack on elements of society I believe are flawed and unjust, and an exposure of the addictions and abuses that colonial history and racial inequality lead to – but there’s also an intense celebration of the power of the Māori voice that remains, its beat and pride and resilience and ancestry, joined by a rich musical joy in the songs of the street I grew up in, their rhythms and rap, energy and power. It has taken me a long time to reach this level of writing in terms of technique, rhythm and content. I want the reader to see things through my shades and feel what it feels like to be me with an understanding of why I am and where I come from. To understand that, No, I don’t know everything, and I don’t expect anyone else to. But, Yes, this is what I saw, felt and how I interpreted it. So there it is and this is me, the bro Hugh. A lit ūrikā descendant of Ngāti Kuri, Ngāti Rēhia, Te Rārawa, Te Aupōuri and Ngāpuhi. Bred in the streets I-roam and made home. A dreamer of the future. Last but not least, your son, your brother, your bro and he who wrote the killer book that you are about to read. Churrr!!!

text: !!!FR33D0M 0FF SP33CH!!! My title is “FR33D0M 0FF SP33CH”, a play on the saying “freedom of speech”. I write with the intent of voicing tough subjects that others haven’t or don’t, and often exposing things that I wouldn’t tell or share personally. “FR33D0M 0FF SP33CH” consists of 37 poems, 2 hooks and a chorus in this complete album. My earliest piece can date back to 2020 with the latest pieces being written in 2021. They express different visions of day-to-day life through points of view and alternating voices and perspectives. The topics range from anything like seeing a face in the smudge on a wall, to things like love, street styles and why I can’t sleep at night. They are to be read left to right, top to bottom -- but feel free to read them as you see fit, because it’s art after all and what you see is what you see. Those labelled “Mirrored” have been turned upside down to allow reading from either end and show the extent of form and variety my pieces can take. Some things may be explicit or hard to read, but I assure you that they are just certain views from different angles that I believe need to be shared. There is a strong political/cultural component to my mahi, a tough vocal attack on elements of society I believe are flawed and unjust, and an exposure of the addictions and abuses that colonial history and racial inequality lead to – but there’s also an intense celebration of the power of the Māori voice that remains, its beat and pride and resilience and ancestry, joined by a rich musical joy in the songs of the street I grew up in, their rhythms and rap, energy and power. It has taken me a long time to reach this level of writing in terms of technique, rhythm and content. I want the reader to see things through my shades and feel what it feels like to be me with an understanding of why I am and where I come from. To understand that, No, I don’t know everything, and I don’t expect anyone else to. But, Yes, this is what I saw, felt and how I interpreted it. So there it is and this is me, the bro Hugh. A lit ūrikā descendant of Ngāti Kuri, Ngāti Rēhia, Te Rārawa, Te Aupōuri and Ngāpuhi. Bred in the streets I-roam and made home. A dreamer of the future. Last but not least, your son, your brother, your bro and he who wrote the killer book that you are about to read. Churrr!!!

year: 2021