71 results on '"Biggar S"'
Search Results
2. Bidirectional Reflectance Round-Robin in Support of the Earth Observing System Program
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Early, E, Barnes, P, Johnson, B, Butler, J, Bruegge, C, Biggar, S, Spyak, P, and Pavlov, M
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Laboratory measurements of the bidirectional reflectance distribution function (BRDRF) of diffuse reflectors are required to support calibration in the Earth Observing System (EOS) program of the National Aeronautics and Space Administration.
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- 1999
3. SeaWiFS technical report series. Volume 27: Case studies for SeaWiFS calibration and validation, part 3
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Hooker, Stanford B, Firestone, Elaine R, Acker, James G, Mueller, J. L, Fraser, R. S, Biggar, S. F, Thome, K. J, Slater, P. N, Holmes, A. W, and Barnes, R. A
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Oceanography - Abstract
This document provides brief reports, or case studies, on a number of investigations sponsored by the Calibration and Validation Team (CVT) within the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) Project. Chapter I describes a comparison of the irradiance immersion coefficients determined for several different marine environmental radiometers (MERs). Chapter 2 presents an analysis of how light absorption by atmospheric oxygen will influence the radiance measurements in band 7 of the SeaWiFS instrument. Chapter 3 gives the results of the second ground-based solar calibration of the instrument, which was undertaken after the sensor was modified to reduce the effects of internal stray light. (The first ground-based solar calibration of SeaWiFS is described in Volume 19 in the SeaWiFS Technical Report Series.) Chapter 4 evaluates the effects of ship shadow on subsurface irradiance and radiance measurements deployed from the deck of the R/V Weatherbird 11 in the Atlantic Ocean near Bermuda. Chapter 5 illustrates the various ways in which a single data day of SeaWiFS observations can be defined, and why the spatial definition is superior to the temporal definition for operational usage.
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- 1995
4. Preflight and Vicarious Calibration of Hyperspectral Imagers
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Thome, K. J., primary and Biggar, S. F., primary
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- 2007
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5. Ground-reference site and on-board methods for sensor absolute calibration in the 0.4 to 2.5 micron range
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Slater, P. N, Biggar, S. F, and Palmer, J. M
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Earth Resources And Remote Sensing - Abstract
The absolute radiometric calibration uncertainty requirement for several multispectral imaging sensors to be used in the Earth Observing System (EOS) program is +/- 2 percent (one sigma) with respect to the sun. Proposed in-flight absolute calibration methods are reviewed that have this uncertainty as their goal. In particular two methods are described as are recent improvements to them that concern reflectance- and radiance-based calibration using a carefully selected ground reference site. The magnitudes of the error sources are listed. A ratioing radiometer approach to monitoring the reflectance of a solar diffuser used for onboard calibration is discussed.
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- 1991
6. Improved evaluation of optical depth components from Langley plot data
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Biggar, S. F, Gellman, D. I, and Slater, P. N
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Instrumentation And Photography - Abstract
A simple, iterative procedure to determine the optical depth components of the extinction optical depth measured by a solar radiometer is presented. Simulated data show that the iterative procedure improves the determination of the exponent of a Junge law particle size distribution. The determination of the optical depth due to aerosol scattering is improved as compared to a method which uses only two points from the extinction data. The iterative method was used to determine spectral optical depth components for June 11-13, 1988 during the MAC III experiment.
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- 1990
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7. G418 The clinical spectrum of dorsal stream dysfunction in autism – a retrospective cohort study of 13 children
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Hay, IJN, primary, Assheton, D, additional, Biggar, S, additional, Ibrahim, H, additional, and Dutton, GN, additional
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- 2018
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8. ''When Cost Measures Contradict''
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Montgomery, W. D., primary, Smith, A. E., additional, Biggar, S. L., additional, and Bernstein, P. M., additional
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- 2003
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9. ''Measuring the Costs of Climate Change Policies''
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Montgomery, W. D., primary, Smith, A. E., additional, Biggar, S. L., additional, and Bernstein, P.M., additional
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- 2003
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10. Preflight and Vicarious Calibration of Hyperspectral Imagers
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ARIZONA UNIV TUCSON OPTICAL SCIENCES CENTER, Thome, K. J., Biggar, S. F., ARIZONA UNIV TUCSON OPTICAL SCIENCES CENTER, Thome, K. J., and Biggar, S. F.
- Abstract
This report describes the work period during the first year of the project to develop a comprehensive calibration/characterization plan describing methods to evaluate the alignment and focus of the optical elements, image quality based on the MTF of the system, stray light, spectral response, polarization sensitivity, detector-to-detector radiometric calibration in both a relative and absolute sense. In addition to the preflight characterization calibration plan, the work includes discussions of vicarious calibration approaches that act as a supplement to the onboard calibration systems to ensure that the sensor is behaving properly while in use., The original document contains color images.
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- 2007
11. Laboratory calibration of field reflectance panels
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Biggar, S. F, Labed, J, Santer, R. P, Slater, P. N, and Jackson, R. D
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Instrumentation And Photography - Abstract
A method used for calibrating field reflectance panels in the visible and shortwave infrared wavelength range is described. The directional reflectance factor of painted barium sulfate (BaSO4) panels is determined. The reference for this method is the hemispherical reflectance of pressed polytetrafluoroethylene (halon) powder prepared according to National Bureau of Standards (NBS) directions. The panels and a radiometer are mounted on rotation stages to measure the reflectance factor at different incidence and view angles. The sensor can be any laboratory or field filter radiometer small enough to mount on the apparatus. The method is used to measure the reflectance factors of halon and BaSO4 panels between 0.45 and 0.85 micrometers. These reflectance factors are compared to those measured by a field apparatus. The results agree to within 0.013 in reflectance at incidence angles between 15 and 75 degrees.
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- 1988
12. Reflectance- and radiance-based methods for the in-flight absolute calibration of multispectral sensors
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Slater, P. N, Biggar, S. F, Holm, R. G, Jackson, R. D, and Mao, Y
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Spacecraft Instrumentation - Abstract
Variations reported in the in-flight absolute radiometric calibration of the Coastal Zone Color Scanner (CZCS) and the Thematic Mapper (TM) on Landsat 4 are reviewed. At short wavelengths these sensors exhibited a gradual reduction in response, while in the midinfrared the TM showed oscillatory variations, according to the results of TM internal calibration. The methodology and results are presented for five reflectance-based calibrations of the Landsat 5 TM at White Sands, NM, in the period July 1984 to November 1985. These show a + or - 2.8 percent standard deviation for the six solar-reflective bands. Analysis and preliminary results of a second, independent calibration method, based on radiance measurements from a helicopter at White Sands, indicate that this is potentially an accurate method for corroborating the results from the reflectance-based method.
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- 1987
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13. Absolute radiometric calibration of the Thematic Mapper
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Slater, P. N, Biggar, S. F, Holm, R. G, Jackson, R. D, and Mao, Y
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Earth Resources And Remote Sensing - Abstract
Calibration data for the solar reflective bands of the Landsat-5 TM obtained from five in-flight absolute radiometric calibrations from July 1984-November 1985 at White Sands, New Mexico are presented and analyzed. Ground reflectance and atmospheric data were utilized to predict the spectral radiance at the entrance pupil of the TM and the average number of digital counts in each TM band. The calibration of each of the TM solar reflective bands was calculated in terms of average digital counts/unit spectral radiance for each band. It is observed that for the 12 reflectance-based measurements the rms variation from the means as a percentage of the mean is + or - 1.9 percent; for the 11 measurements in the IR bands, it is + or - 3.4 percent; and the rms variation for all 23 measurements is + or - 2.8 percent.
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- 1986
14. Radiometric calibration of Advanced Land Imager using reflectance-based results between 2001 and 2005
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McCorkel, J., primary, Thome, K., additional, Biggar, S., additional, and Kuester, M., additional
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- 2006
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15. Radiometric calibration of Advanced Land Imager using reflectance-based results between 2001 and 2005.
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McCorkel, J., Thome, K., Biggar, S., and Kuester, M.
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- 2006
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16. Intra-rectal application of amifostine for prevention of late radiation rectal injury: preliminary results of a phase i dose escalation study
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Kaplan, I., primary, Han, S., additional, Tobi, M., additional, Vargas, B., additional, Stamos, B., additional, Kelly, L., additional, Biggar, S., additional, and Ben-Joef, E., additional
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- 2001
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17. Cell signaling can direct either binary or graded transcriptional responses
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Biggar, S. R., primary
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- 2001
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18. Characterization and field use of a CCD camera system for retrieval of bidirectional reflectance distribution function
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Nandy, P., primary, Thome, K., additional, and Biggar, S., additional
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- 2001
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19. Bidirectional Reflectance Round-Robin in Support of the Earth Observing System Program
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Early, E. A., primary, Barnes, P. Y., additional, Johnson, B. C., additional, Butler, J. J., additional, Bruegge, C. J., additional, Biggar, S. F., additional, Spyak, P. R., additional, and Pavlov, M. M., additional
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- 2000
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20. Continuous and widespread roles for the Swi-Snf complex in transcription
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Biggar, S. R., primary
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- 1999
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21. Initial results of the bidirectional reflectance characterization round-robin in support of EOS
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Johnson, B C, primary, Barnes, P Y, additional, O'Brian, T R, additional, Butler, J J, additional, Bruegge, C J, additional, Biggar, S, additional, Spyak, P R, additional, and Pavlov, M M, additional
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- 1998
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22. Calibration of a visible and near-infrared portable transfer radiometer
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Biggar, S F, primary
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- 1998
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23. A 400 nm to 2500 nm absolute spectral radiance comparison using filter radiometers
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Yoon, H W, primary, Johnson, B C, additional, Kelch, D, additional, Biggar, S, additional, and Spyak, P R, additional
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- 1998
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24. Field evaluation of a diffuse to global irradiance meter for vicarious calibration
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Smith, J., primary, Thome, K., additional, Crowther, B., additional, and Biggar, S., additional
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- 1998
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25. Instrument for retrieval of BRDF data for vicarious calibration
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Nandy, P., primary, Thome, K., additional, and Biggar, S., additional
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- 1998
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26. Purification and biochemical heterogeneity of the mammalian SWI-SNF complex.
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Wang, W., primary, Côté, J., additional, Xue, Y., additional, Zhou, S., additional, Khavari, P. A., additional, Biggar, S. R., additional, Muchardt, C., additional, Kalpana, G. V., additional, Goff, S. P., additional, Yaniv, M., additional, Workman, J. L., additional, and Crabtree, G. R., additional
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- 1996
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27. Intrarectal application of amifostine for the prevention of radiation-induced rectal injury
- Author
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Ben-Josef, E., Han, S., Tobi, M., Vargas, B.J., Stamos, B., Kelly, L., Biggar, S., and Kaplan, I.
- Abstract
Clinically symptomatic late injury to the rectal wall occurs in about one third of patients with prostate cancer treated with external beam irradiation. Reducing the physical dose to the anterior rectal wall without a similar reduction in the posterior peripheral zone is difficult because of the proximity of these structures. Based on our previous observations that intrarectal application of amifostine resulted in very high concentrations of amifostine and its active metabolite WR-1065 in the rectal wall of Copenhagen rats, the authors initiated a phase I clinical trial in 1998. Twenty-nine patients with localized prostate cancer were accrued. Eligibility criteria included histologically confirmed adenocarcinoma, a Karnofsky performance status of >=70, and no pelvic lymphadenopathy or distant metastases. The total dose to the prostate was 70.2 Gy (20 patients) and 73.8 Gy (9 patients). Therapy was delivered using a 4-field axial technique and 3-dimensional conformal planning. Amifostine was administered intrarectally as an aqueous solution 30 minutes before irradiation on the first 15 days of therapy. Amifostine dose was escalated, in cohorts, from 500 mg to 2,500 mg. Toxicity was evaluated using the Radiation Therapy Oncology Group late morbidity scale. All patients completed therapy with no amifostine-related toxicity at any dose level. The application was feasible and well tolerated. With a median follow-up time of 21 months, 9 patients (33%) had rectal bleeding (8 grade 1, 1 grade 2). Four patients (14%) had symptoms suggestive of radiation injury, which proved to be secondary to nonrelated processes. These included preexisting nonspecific proctitis (1 patient), diverticular disease of the sigmoid colon, rectal polyp (1 patient), and ulcerative colitis (1 patient). Symptoms developed significantly more often in patients receiving 500 to 1,000 mg than in patients receiving 1,500 to 2,500 mg amifostine (7 of 14 [50%] versus 2 of 13 [15%]; P=.0325, 1-sided x^2 test). Intrarectal application of amifostine is feasible and well tolerated. A complete lack of systemic toxicity obviates the need for close monitoring of patients during and after administration. Rectal symptomatology after external beam radiotherapy to the pelvis cannot be assumed to reflect late radiation damage, because it often is a manifestation of an unrelated pathologic process. The preliminary efficacy data are encouraging and suggest that intrarectal administration of amifostine may reduce radiation damage. Further clinical studies are warranted.
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- 2002
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28. Purification and biochemical heterogeneity of the mammalian SWI-SNF complex
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Weidong Wang, Côté, J., Xue, Y., Zhou, S., Khavari, P. A., Biggar, S. R., Muchardt, C., Kalpana, G. V., Goff, S. P., Yaniv, M., Workman, J. L., and Crabtree, G. R.
29. Absolute Radiometric Calibration Of The NOAA AVHRR Sensors
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Teillet, P M., primary, Slater, P N., additional, Mao, Y, additional, Ding, Y, additional, Yuan, B, additional, Bartell, R J., additional, Biggar, S F., additional, Santer, R P., additional, Jackson, R D., additional, and Moran, M S., additional
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- 1988
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30. Absolute Radiometric Calibration Of The Thematic Mapper
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Slater, P N., primary, Biggar, S F., additional, Holm, R G., additional, Jackson, R D., additional, Mao, Y, additional, Moran, M S., additional, Palmer, J M., additional, and Yuan, B, additional
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- 1986
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31. Laboratory Calibration Of Field Reflectance Panels
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Biggar, S F., primary, Labed, J, additional, Santer, R P., additional, Slater, P. N., additional, Jackson, R D., additional, and Moran, M S., additional
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- 1988
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32. G418 The clinical spectrum of dorsal stream dysfunction in autism – a retrospective cohort study of 13 children
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Hay, IJN, Assheton, D, Biggar, S, Ibrahim, H, and Dutton, GN
- Abstract
AimsBilateral dysfunction of the parieto-occipital cortex, linked to the visual cortex by the dorsal stream, variably produces simultanagnosia (SIM), optic ataxia (OA), and gaze apraxia. This triad, rarely reported in childhood, comprises ‘Balint syndrome’. ‘Dorsal stream dysfunction’ (DSD) describes milder degrees of this disorder.This study aimed to determine the character and severity of DSD in a cohort of autistic children and to identify possible prognostic indicators for targeting specialist support.Methods13 able children with autism, sequentially receiving a tertiary neuro-ophthalmic diagnosis of DSD, were followed up over 6 years. Records were retrospectively reviewed for neurodevelopmental and neuro-ophthalmic examination results.Age-inappropriate configural disruption of elements of drawings was identified in the Beery-VMI Test of Visual-Motor Integration (VMI) as evidence of SIM and standard VMI scores (VMIS) were used to measure the severity of SIM. Still-frame analysis of video was used to confirm diagnoses of OA using the criterion of impaired terminal grip size relative to the target grasped. Severity of visual functional impairment was rated on mean individual Cerebral Visual Impairment Inventory scores (MCVIS) using as reference the 90th percentile cut-off MCVIS of 0.74 for the typically developing population.Correlation between MCVIS and VMIS was determined by linear regression analysis. Method agreement analysis for OA in central vision and motor coordination impairment (MCI), measured by the Beery Motor Coordination assessment, was determined by Cohen’s weighted Kappa statistic (K).ResultsSignificant correlation was found between MCVIS and VMIS: r=−0.77 [95%CI: −0.93 to −0.83], p=0.002. Five children required specialist visual impairment (VI) support. The MCVIS for this group (3.05)differed significantly from the MCVIS for the non-support group (1.91)[difference 95% CI 0.74–1.55], p<0.0001. Agreement for severe MCI (≤5 th percentile) with central OA was significant: K=1 [95% CI: 0.46 to 1.54], p=0.0002.ConclusionsSIM may account for the visual perceptual impairment seen in ASD and OA may underpin motor impairment. MCVIS and VMIS may be useful indicators of the need for specialist VI support.
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- 2018
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33. Laser-based system for ground-based measurement of backscatter surface reflectance.
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Biggar, S., Thome, K., Geis, J., and Burkhart, C.
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- 2004
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34. 'Virtually daily grief'-understanding distress in health practitioners involved in a regulatory complaints process: a qualitative study in Australia.
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Biggar S, van der Gaag A, Maher P, Evans J, Bondu L, Kar Ray M, Phillips R, Tonkin A, Schofield C, Ayscough K, Hardy M, Anderson S, Saar E, and Fletcher M
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- Humans, Retrospective Studies, Australia, Decision Making, Grief, Patient Satisfaction
- Abstract
Protection of the public is the paramount aim for health practitioner regulation, yet there has been growing concern globally on the association between regulatory complaints processes and practitioner mental health and wellbeing. The objective was to understand the experience, particularly distress, of health practitioners involved in a regulatory complaints process to identify potential strategies to minimise future risk of distress. Semi-structured qualitative interviews were conducted with health practitioners in Australia who had recently been through a regulatory complaints process, together with a retrospective analysis of documentation relating to all identified cases of self-harm or suicide of health practitioners who were involved in such a process over 4 years. Data from interviews and the serious incident analysis found there were elements of the regulatory complaints process contributing to practitioner distress. These included poor communication, extended time to close the investigation, and the management of health-related concerns. The study found external personal circumstances and pre-existing conditions could put the practitioner at greater risk of distress. There were found to be key moments in the process-triggers-where the practitioner was at particular risk of severe distress. Strong support networks, both personal and professional, were found to be protective against distress. Through process improvements and, where appropriate, additional support for practitioners, we hope to further minimise the risk of practitioner distress and harm when involved in a regulatory complaints process. The findings also point to the need for improved partnerships between regulators and key stakeholders, such as legal defence organisations, indemnity providers, employers, and those with lived experience of complaints processes. Together they can improve the support for practitioners facing a complaint and address the stigma, shame, and fear associated with regulatory complaints processes. This project provides further evidence that a more compassionate approach to regulation has the potential to be better for all parties and, ultimately, the wider healthcare system., (© The Author(s) 2023. Published by Oxford University Press on behalf of International Society for Quality in Health Care.)
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- 2023
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35. Consumers' and health providers' views and perceptions of partnering to improve health services design, delivery and evaluation: a co-produced qualitative evidence synthesis.
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Merner B, Schonfeld L, Virgona A, Lowe D, Walsh L, Wardrope C, Graham-Wisener L, Xafis V, Colombo C, Refahi N, Bryden P, Chmielewski R, Martin F, Messino NM, Mussared A, Smith L, Biggar S, Gill M, Menzies D, Gaulden CM, Earnshaw L, Arnott L, Poole N, Ryan RE, and Hill S
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- Humans, Community Participation, Caregivers, Health Services, Health Personnel
- Abstract
Background: Partnering with consumers in the planning, delivery and evaluation of health services is an essential component of person-centred care. There are many ways to partner with consumers to improve health services, including formal group partnerships (such as committees, boards or steering groups). However, consumers' and health providers' views and experiences of formal group partnerships remain unclear. In this qualitative evidence synthesis (QES), we focus specifically on formal group partnerships where health providers and consumers share decision-making about planning, delivering and/or evaluating health services. Formal group partnerships were selected because they are widely used throughout the world to improve person-centred care. For the purposes of this QES, the term 'consumer' refers to a person who is a patient, carer or community member who brings their perspective to health service partnerships. 'Health provider' refers to a person with a health policy, management, administrative or clinical role who participates in formal partnerships in an advisory or representative capacity. This QES was co-produced with a Stakeholder Panel of consumers and health providers. The QES was undertaken concurrently with a Cochrane intervention review entitled Effects of consumers and health providers working in partnership on health services planning, delivery and evaluation., Objectives: 1. To synthesise the views and experiences of consumers and health providers of formal partnership approaches that aimed to improve planning, delivery or evaluation of health services. 2. To identify best practice principles for formal partnership approaches in health services by understanding consumers' and health providers' views and experiences., Search Methods: We searched MEDLINE, Embase, PsycINFO and CINAHL for studies published between January 2000 and October 2018. We also searched grey literature sources including websites of relevant research and policy organisations involved in promoting person-centred care., Selection Criteria: We included qualitative studies that explored consumers' and health providers' perceptions and experiences of partnering in formal group formats to improve the planning, delivery or evaluation of health services., Data Collection and Analysis: Following completion of abstract and full-text screening, we used purposive sampling to select a sample of eligible studies that covered a range of pre-defined criteria, including rich data, range of countries and country income level, settings, participants, and types of partnership activities. A Framework Synthesis approach was used to synthesise the findings of the sample. We appraised the quality of each study using the CASP (Critical Appraisal Skill Program) tool. We assessed our confidence in the findings using the GRADE-CERQual (Confidence in the Evidence from Reviews of Qualitative research) approach. The Stakeholder Panel was involved in each stage of the review from development of the protocol to development of the best practice principles., Main Results: We found 182 studies that were eligible for inclusion. From this group, we selected 33 studies to include in the final synthesis. These studies came from a wide range of countries including 28 from high-income countries and five from low- or middle-income countries (LMICs). Each of the studies included the experiences and views of consumers and/or health providers of partnering in formal group formats. The results were divided into the following categories. Contextual factors influencing partnerships: government policy, policy implementation processes and funding, as well as the organisational context of the health service, could facilitate or impede partnering (moderate level of confidence). Consumer recruitment: consumer recruitment occurred in different ways and consumers managed the recruitment process in a minority of studies only (high level of confidence). Recruiting a range of consumers who were reflective of the clinic's demographic population was considered desirable, particularly by health providers (high level of confidence). Some health providers perceived that individual consumers' experiences were not generalisable to the broader population whereas consumers perceived it could be problematic to aim to represent a broad range of community views (high level of confidence). Partnership dynamics and processes: positive interpersonal dynamics between health providers and consumers facilitated partnerships (high level of confidence). However, formal meeting formats and lack of clarity about the consumer role could constrain consumers' involvement (high level of confidence). Health providers' professional status, technical knowledge and use of jargon were intimidating for some consumers (high level of confidence) and consumers could feel their experiential knowledge was not valued (moderate level of confidence). Consumers could also become frustrated when health providers dominated the meeting agenda (moderate level of confidence) and when they experienced token involvement, such as a lack of decision-making power (high level of confidence) Perceived impacts on partnership participants: partnering could affect health provider and consumer participants in both positive and negative ways (high level of confidence). Perceived impacts on health service planning, delivery and evaluation: partnering was perceived to improve the person-centredness of health service culture (high level of confidence), improve the built environment of the health service (high level of confidence), improve health service design and delivery e.g. facilitate 'out of hours' services or treatment closer to home (high level of confidence), enhance community ownership of health services, particularly in LMICs (moderate level of confidence), and improve consumer involvement in strategic decision-making, under certain conditions (moderate level of confidence). There was limited evidence suggesting partnering may improve health service evaluation (very low level of confidence). Best practice principles for formal partnering to promote person-centred care were developed from these findings. The principles were developed collaboratively with the Stakeholder Panel and included leadership and health service culture; diversity; equity; mutual respect; shared vision and regular communication; shared agendas and decision-making; influence and sustainability., Authors' Conclusions: Successful formal group partnerships with consumers require health providers to continually reflect and address power imbalances that may constrain consumers' participation. Such imbalances may be particularly acute in recruitment procedures, meeting structure and content and decision-making processes. Formal group partnerships were perceived to improve the physical environment of health services, the person-centredness of health service culture and health service design and delivery. Implementing the best practice principles may help to address power imbalances, strengthen formal partnering, improve the experiences of consumers and health providers and positively affect partnership outcomes., (Copyright © 2023 The Authors. Cochrane Database of Systematic Reviews published by John Wiley & Sons, Ltd. on behalf of The Cochrane Collaboration.)
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- 2023
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36. Finding space for kindness: public protection and health professional regulation.
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Biggar S, Fletcher M, Van Der Gaag A, and Austin Z
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- 2022
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37. Interventions for promoting participation in shared decision-making for children and adolescents with cystic fibrosis.
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Malone H, Biggar S, Javadpour S, Edworthy Z, Sheaf G, and Coyne I
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- Adolescent, Child, Child, Preschool, Humans, Self-Management, Cystic Fibrosis, Decision Making, Patient Participation
- Abstract
Background: Shared decision-making is important in child and adolescent healthcare because there is growing international recognition of children and young people's rights to be included in decisions that affect them. In order for young people to participate effectively in shared decision-making they need to develop the skills of engagement with healthcare professionals and confidence in interacting with them. They also need to learn how to manage their condition and treatments on their own when they move into adulthood. Children and young people who participate in shared decision-making in healthcare are likely to be more informed, feel more prepared, and experience less anxiety about the unknown. Significant improvements in cystic fibrosis (CF) survival over recent decades, due to improved therapies and better management of care, means that young people with CF are routinely transitioning to adult healthcare where increasing emphasis on self-management brings greater complexity in decision-making. We need to know what interventions are effective in promoting shared decision-making for young people with CF., Objectives: To assess the effectiveness of interventions that promote participation in shared decision-making for children and adolescents (aged between four and 18 years) with CF., Search Methods: We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Cystic Fibrosis Trials Register, compiled from electronic database searches and handsearches of journals and conference abstract books. We also searched the reference lists of articles and reviews addressing shared decision-making.Date of most recent search: 12 March 2019.We searched PubMed, CINAHL (EBSCO), Embase (Elsevier), PsycINFO (EBSCO), WHO ICTRP, ASSIA (ProQuest), ERIC (ProQuest), ProQuest Dissertations and Theses, and ClinicalTrials.gov. We contacted study authors with published relevant research in shared decision-making for adults to ask if they were aware of any published or ongoing studies on the promotion of the intervention for children or adolescents (or both) with CF.Date of most recent search: 19 March 2019., Selection Criteria: We planned to include randomised controlled trials (RCTs) (but not cross-over RCTs) of interventions promoting shared decision-making for children and adolescents with CF aged between four and 18 years, such as information provision, booklets, two-way interaction, checking understanding (by the participant), preparation to participate in a healthcare decision, decision-aids, and training interventions or educational programs. We planned to include interventions aimed at children or adolescents (or both), parents or healthcare professionals or any combination of these groups provided that the focus was aimed at promoting shared decision-making for children and adolescents with CF., Data Collection and Analysis: Two authors independently reviewed papers identified in the searches., Main Results: No eligible RCTs were identified for inclusion in this systematic review., Authors' Conclusions: We were unable to identify RCTs with evidence which would support healthcare policy-making and practice related to implementation of shared decision-making for children and adolescents (aged between four and 18 years) with CF). We hope that having identified this gap in research, awareness will increase amongst researchers of the need to design high-quality shared decision-making interventions for young people with CF, perhaps adapted from existing models for adults, and to test these interventions and children's preferences in RCTs. It is also important to target health professionals with evidence-based education programmes on shared decision-making and a need for international consensus on addressing the variability in education programmes.
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- 2019
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38. Ultra-portable field transfer radiometer for vicarious calibration of earth imaging sensors.
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Thome K, Wenny B, Anderson N, McCorkel J, Czapla-Myers J, and Biggar S
- Abstract
A small portable transfer radiometer has been developed as part of an effort to ensure the quality of upwelling radiance from test sites used for vicarious calibration in the solar reflective. The test sites are used to predict top-of-atmosphere reflectance relying on ground-based measurements of the atmosphere and surface. The portable transfer radiometer is designed for one-person operation for on-site field calibration of instrumentation used to determine ground-leaving radiance. The current work describes the detector- and source-based radiometric calibration of the transfer radiometer highlighting the expected accuracy and SI-traceability. The results indicate differences between the detector-based and source-based results greater than the combined uncertainties of the approaches. Results from recent field deployments of the transfer radiometer using a solar radiation based calibration agree with the source-based laboratory calibration within the combined uncertainties of the methods. The detector-based results show a significant difference to the solar-based calibration. The source-based calibration is used as the basis for a radiance-based calibration of the Landsat-8 Operational Land Imager that agrees with the OLI calibration to within the uncertainties of the methods.
- Published
- 2018
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- View/download PDF
39. The view from the elevator.
- Author
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Biggar S
- Subjects
- Adolescent, Child, Child, Preschool, Cross Infection prevention & control, Humans, Hospitals, Pediatric, Organizational Policy, Siblings, Visitors to Patients
- Published
- 2017
- Full Text
- View/download PDF
40. Design and Evaluation of a Soft and Wearable Robotic Glove for Hand Rehabilitation.
- Author
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Biggar S and Yao W
- Subjects
- Equipment Design, Equipment Failure Analysis, Feasibility Studies, Hand, Hand Strength, Humans, Man-Machine Systems, Pilot Projects, Robotics methods, Self-Help Devices, Therapy, Computer-Assisted methods, Artificial Limbs, Exoskeleton Device, Gloves, Protective, Neurological Rehabilitation instrumentation, Robotics instrumentation, Therapy, Computer-Assisted instrumentation
- Abstract
In the modern world, due to an increased aging population, hand disability is becoming increasingly common. The prevalence of conditions such as stroke is placing an ever-growing burden on the limited fiscal resources of health care providers and the capacity of their physical therapy staff. As a solution, this paper presents a novel design for a wearable and adaptive glove for patients so that they can practice rehabilitative activities at home, reducing the workload for therapists and increasing the patient's independence. As an initial evaluation of the design's feasibility the prototype was subjected to motion analysis to compare its performance with the hand in an assessment of grasping patterns of a selection of blocks and spheres. The outcomes of this paper suggest that the theory of design has validity and may lead to a system that could be successful in the treatment of stroke patients to guide them through finger flexion and extension, which could enable them to gain more control and confidence in interacting with the world around them.
- Published
- 2016
- Full Text
- View/download PDF
41. Design and calibration of field deployable ground-viewing radiometers.
- Author
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Anderson N, Czapla-Myers J, Leisso N, Biggar S, Burkhart C, Kingston R, and Thome K
- Abstract
Three improved ground-viewing radiometers were built to support the Radiometric Calibration Test Site (RadCaTS) developed by the Remote Sensing Group (RSG) at the University of Arizona. Improved over previous light-emitting diode based versions, these filter-based radiometers employ seven silicon detectors and one InGaAs detector covering a wavelength range of 400-1550 nm. They are temperature controlled and designed for greater stability and lower noise. The radiometer systems show signal-to-noise ratios of greater than 1000 for all eight channels at typical field calibration signal levels. Predeployment laboratory radiance calibrations using a 1 m spherical integrating source compare well with in situ field calibrations using the solar radiation based calibration method; all bands are within ±2.7% for the case tested.
- Published
- 2013
- Full Text
- View/download PDF
42. Induction of apoptosis in retinoid-refractory acute myelogenous leukemia by a novel AHPN analog.
- Author
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Zhang Y, Dawson MI, Ning Y, Polin L, Parchment RE, Corbett T, Mohamed AN, Feng KC, Farhana L, Rishi AK, Hogge D, Leid M, Peterson VJ, Zhang XK, Mohammad R, Lu JS, Willman C, VanBuren E, Biggar S, Edelstein M, Eilender D, and Fontana JA
- Subjects
- Adamantane analogs & derivatives, Animals, Antineoplastic Agents pharmacology, Caspases metabolism, Cell Division drug effects, Female, Humans, Mice, Mice, Inbred Strains, Neoplasm Transplantation, Neoplastic Stem Cells drug effects, Poly(ADP-ribose) Polymerases metabolism, Signal Transduction, Tumor Cells, Cultured, Adamantane pharmacology, Apoptosis, Cinnamates pharmacology, Drug Resistance, Neoplasm, Leukemia, Myeloid, Acute drug therapy, Retinoids pharmacology
- Abstract
Acute myelogenous leukemia (AML) is a heterogeneous disease consisting of a variety of different leukemic subtypes. While acute promyelocytic leukemia displays marked sensitivity to the differentiating effects of trans-retinoic acid (tRA), other subtypes of AML display resistance. We now describe a novel compound (E)-4-[3-(1-adamantyl)-4-hydroxyphenyl]-3-chlorocinnamic acid (3-Cl-AHPC/MM002) that induces apoptosis in the tRA-resistant leukemia cell lines M07e, KG-1, and HL-60R, and in tRA-resistant patient leukemic blasts. The 3-Cl-AHPC totally inhibits leukemia colony formation at concentrations that inhibit committed human bone marrow stem cell proliferation, that is, granulocyte/macrophage colony-forming units (CFU-GMs) by only 30%. Exposure to 3-Cl-AHPC results in caspase activation and the cleavage of poly(adenosine diphosphate) (poly(ADP)) ribose polymerase. While activation of the extracellular signal-regulated kinase (ERK) and p38 pathways is not necessary for 3-Cl-AHPC-mediated apoptosis, maximal apoptosis requires c-Jun N-terminal kinase (JNK) activation. The 3-Cl-AHPC-mediated cleavage of the antiapoptotic B-cell leukemia XL (Bcl-XL) protein to a proapoptotic 18-kDa product is found in both the M07e cell line and patient leukemic blasts. The 3-Cl-AHPC treatment of mice bearing the AML 1498 cell line results in a 3.3-log kill in the leukemic blasts. While 3-Cl-AHPC does not activate retinoic nuclear receptors, it is a potent inducer of apoptosis in AML cells and may represent a novel therapy in the treatment of this disease.
- Published
- 2003
- Full Text
- View/download PDF
43. Induction of apoptosis of human B-CLL and ALL cells by a novel retinoid and its nonretinoidal analog.
- Author
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Zhang Y, Dawson MI, Mohammad R, Rishi AK, Farhana L, Feng KC, Leid M, Peterson V, Zhang XK, Edelstein M, Eilander D, Biggar S, Wall N, Reichert U, and Fontana JA
- Subjects
- Acetylation, Antineoplastic Agents pharmacokinetics, Apoptosis drug effects, Cell Division drug effects, Dose-Response Relationship, Drug, Esters, Humans, Hydrolysis, Kinetics, Retinoids pharmacokinetics, Tumor Cells, Cultured, Antineoplastic Agents toxicity, Leukemia, Lymphocytic, Chronic, B-Cell pathology, Precursor Cell Lymphoblastic Leukemia-Lymphoma pathology, Retinoids toxicity
- Abstract
We have recently described a novel retinoid 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalenecarboxylic acid (CD437/AHPN) that induces apoptosis in a number of malignant cell types. We now describe our studies examining the effects of CD437 and a nonretinoidal analog (MM002) on the in vitro proliferation of the ALL-REH cell line, the in vitro and in vivo growth of a novel Epstein-Barr virus-negative (EBV(-)) B-cell chronic lymphocytic leukemia (B-CLL) cell line (WSU-CLL), and primary cultures of human B-CLL and acute lymphoblastic leukemia (ALL) cells. CD437 and MM002 induce apoptosis in both cell lines, as indicated by the activation of caspase-2 and caspase-3, cleavage of poly(adenosine diphosphate-ribose) (poly(ADP-ribose)) polymerase, increase in annexin V binding, and subsequent nuclear fragmentation. CD437-mediated apoptosis was not associated with the modulation of Bcl-2, Bax, or Mcl-1 levels, but was associated with the cleavage of the antiapoptotic protein Bcl-X(L) to a proapoptotic 18-kD form. This cleavage of Bcl-X(L) was dependent on caspase-3 activation since Bcl-X(L) cleavage and apoptosis were inhibited by the caspase-3 inhibitor Z-DVED-fmk. CD437 markedly inhibited the growth of WSU-CLL cells in severe combined immunodeficiency (SCID) mice. Tumor growth inhibition, growth delay, and log cell kill were 85.7%, 21 days, and 2.1, respectively, in the treated mice. Moreover, 1 of the 5 treated mice was tumor-free longer than 150 days and thus was considered cured. Exposure of primary cultures of both B-CLL and ALL cells obtained from patients to CD437 and MM002 resulted in their apoptosis. These results suggest that CD437 and MM002 analogs may have a potential role in the treatment of B-CLL and ALL.
- Published
- 2002
- Full Text
- View/download PDF
44. A pilot study of topical intrarectal application of amifostine for prevention of late radiation rectal injury.
- Author
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Ben-Josef E, Han S, Tobi M, Shaw LM, Bonner HS, Vargas BJ, Prokop S, Stamos B, Kelly L, Biggar S, and Kaplan I
- Subjects
- Adenocarcinoma drug therapy, Administration, Topical, Amifostine administration & dosage, Amifostine pharmacology, Analysis of Variance, Dose-Response Relationship, Drug, Dose-Response Relationship, Radiation, Humans, Intestinal Mucosa metabolism, Male, Mercaptoethylamines pharmacology, Multivariate Analysis, Prostatic Neoplasms drug therapy, Prostatic Neoplasms metabolism, Radiation-Protective Agents pharmacology, Rectum pathology, Rectum radiation effects, Telangiectasis pathology, Time Factors, Adenocarcinoma radiotherapy, Prostatic Neoplasms radiotherapy
- Abstract
Purpose: Clinical symptomatic late injury to the rectal wall occurs in about one-third of patients with prostate cancer treated with external beam irradiation. Reducing the physical dose to the anterior rectal wall without a similar reduction in the posterior peripheral zone is difficult because of the proximity of the prostate to the anterior rectal wall. On the basis of our previous observations in an animal model that intrarectal application of amifostine resulted in very high concentrations of amifostine and its active metabolite WR-1065 in the rectal wall, a Phase I dose-escalation clinical trial was undertaken., Methods and Materials: Twenty-nine patients with localized prostate cancer were accrued. Eligibility criteria included histologically confirmed adenocarcinoma, Karnofsky performance status >or=70, and no pelvic lymphadenopathy or distant metastases. The total dose to the prostate was 70.2 Gy in 20 patients and 73.8 Gy in 9 patients. Therapy was delivered using a 4-field technique with three-dimensional conformal planning. Amifostine was administered intrarectally as an aqueous solution 30 min before irradiation on the first 15 days of therapy. Amifostine was escalated in cohorts from 500 to 2500 mg. Proctoscopy was performed before therapy and at 9 months after completion. Most patients underwent repeat proctoscopy at 18 months. On Days 1 and 10 of radiotherapy, serum samples were collected for pharmacokinetic studies. The clinical symptoms (Radiation Therapy Oncology Group scale) and a proctoscopy score were assessed during follow-up., Results: All patients completed therapy with no amifostine-related toxicity at any dose level. The application was feasible and well tolerated. No substantial systemic absorption occurred. With a median follow-up of 26 months, 9 patients (33%) developed rectal bleeding (8 Grade 1, 1 Grade 2). At 9 months, 16 and 3 patients developed Grade 1 and Grade 2 telangiectasia, respectively. This was mostly confined to the anterior rectal wall. No visible mucosal edema, ulcerations, or strictures were noted. No significant differences were found between the proctoscopy findings at 9 and 18 months. Four patients (14%) developed symptoms suggestive of radiation damage that, on sigmoidoscopy, proved to be secondary to unrelated processes. These included preexisting nonspecific proctitis (n = 1), diverticular disease of the sigmoid colon (n = 1), rectal polyp (n = 1), and ulcerative colitis (n = 1). Symptoms developed significantly more often in patients receiving 500-1000 mg than in patients receiving 1500-2500 mg amifostine (7 [50%] of 14 vs. 2 [15%] of 13, p = 0.0325, one-sided chi-square test)., Conclusion: Intrarectal application of amifostine is feasible and well tolerated. Systemic absorption of amifostine and its metabolites is negligible, and close monitoring of patients is not required with rectal administration. Proctoscopy is superior to symptom score as a method of assessing radiation damage of the rectal wall. The preliminary efficacy data are encouraging, and further clinical studies are warranted.
- Published
- 2002
- Full Text
- View/download PDF
45. SeaWiFS transfer-to-orbit experiment.
- Author
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Barnes RA, Eplee RE Jr, Biggar SF, Thome KJ, Zalewski EF, Slater PN, and Holmes AW
- Abstract
We present the results of an experiment designed to measure the changes in the radiometric calibration of the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) from the time of its manufacture to the time of the start of on-orbit operations. The experiment uses measurements of the Sun at the manufacturer's facility to predict the instrument outputs during solar measurements immediately after launch. Because an onboard diffuser plate is required for these measurements, the experiment measures changes in the instrument-diffuser system. There is no mechanism in this experiment to separate changes in the diffuser from changes in the instrument. For the eight SeaWiFS bands, the initial instrument outputs on orbit averaged 0.8% higher than predicted with a standard deviation of 0.9%. The greatest difference was 2.1% (actual output higher than predicted) for band 3. The estimated uncertainty for the experiment is 3%. Thus the transfer-to-orbit experiment shows no changes in the radiometric sensitivities of the SeaWiFS bands--at the 3% level--from the completion of the instrument's manufacture to its insertion into orbit.
- Published
- 2000
- Full Text
- View/download PDF
46. Chemically regulated transcription factors reveal the persistence of repressor-resistant transcription after disrupting activator function.
- Author
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Biggar SR and Crabtree GR
- Subjects
- Animals, Calcineurin metabolism, Cell Cycle drug effects, Fungal Proteins genetics, Fungal Proteins metabolism, Gene Silencing, Histone Deacetylases, Immunosuppressive Agents pharmacology, Mice, Mitosis drug effects, Models, Biological, Promoter Regions, Genetic, Protein Structure, Tertiary, Recombinant Fusion Proteins metabolism, Sirolimus pharmacology, Tacrolimus pharmacology, Time Factors, Transcription Factors genetics, Transcription Factors metabolism, Yeasts metabolism, beta-Galactosidase metabolism, DNA-Binding Proteins, Gene Expression Regulation drug effects, Nuclear Proteins, Repressor Proteins, Saccharomyces cerevisiae Proteins, Transcription Factors physiology, Transcription, Genetic drug effects, Transcriptional Activation
- Abstract
Control of gene expression often requires that transcription terminates rapidly after destruction, inactivation, or nuclear export of transcription factors. However, the role of transcription factor inactivation in terminating transcription is unclear. We have developed a means of conducting order of addition and co-occupancy experiments in living cells by rapidly exchanging proteins bound to promoters. Using this approach, we found that, following specific disruption of activator function, transcription from active promoters decayed slowly, persisting through multiple cell divisions. This persistent transcriptional activity raised the question of what mechanisms return promoters to inactive states. By exchanging or directing co-occupancy of protein complexes bound to a promoter, we found that the transcriptional inhibitor, Ssn6-Tup1, lost its effectiveness as a repressor following activator dissociation. Similar experiments with another repressor, the histone deacetylase Sin3-Rpd3, reinforced this distinction between repression in the presence and absence of an activator. These results suggest that although repressors such as Ssn6-Tup1 and Sin3-Rpd3 prevent activation of gene expression, other mechanisms of repression return promoters to inactive states following the dissociation or inactivation of a transcriptional activator.
- Published
- 2000
- Full Text
- View/download PDF
47. Evaluation of the Applicability of Solar and Lamp Radiometric Calibrations of a Precision Sun Photometer Operating Between 300 and 1025 nm.
- Author
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Schmid B, Spyak PR, Biggar SF, Wehrli C, Sekler J, Ingold T, Mätzler C, and Kämpfer N
- Abstract
Over a period of 3 years a precision Sun photometer (SPM) operating between 300 and 1025 nm was calibrated four times at three different high-mountain sites in Switzerland, Germany, and the United States by means of the Langley-plot technique. We found that for atmospheric window wavelengths the total error (2varsigma-statistical plus systematic errors) of the calibration constants V(0) (lambda), the SPM voltage in the absence of any attenuating atmosphere, can be kept below 1.6% in the UV-A and blue, 0.9% in the mid-visible, and 0.6% in the near-infrared spectral region. For SPM channels within strong water-vapor or ozone absorption bands a modified Langley-plot technique was used to determine V(0) (lambda) with a lower accuracy. Within the same period of time, we calibrated the SPM five times using irradiance standard lamps in the optical labs of the Physikalisch-Meteorologisches Observatorium Davos and World Radiation Center, Switzerland, and of the Remote Sensing Group of the Optical Sciences Center, University of Arizona, Tucson, Arizona. The lab calibration method requires knowledge of the extraterrestrial spectral irradiance. When we refer the standard lamp results to the World Radiation Center extraterrestrial solar irradiance spectrum, they agree with the Langley results within 2% at 6 of 13 SPM wavelengths. The largest disagreement (4.4%) is found for the channel centered at 610 nm. The results of these intercomparisons change significantly when the lamp results are referred to two different extraterrestrial solar irradiance spectra that have become recently available.
- Published
- 1998
- Full Text
- View/download PDF
48. Small molecule-dependent genetic selection in stochastic nanodroplets as a means of detecting protein-ligand interactions on a large scale.
- Author
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Borchardt A, Liberles SD, Biggar SR, Crabtree GR, and Schreiber SL
- Subjects
- Antifungal Agents chemistry, Antifungal Agents pharmacology, Cell Membrane Permeability, Ligands, Molecular Weight, Polyenes chemistry, Polyenes pharmacology, Saccharomyces cerevisiae drug effects, Saccharomyces cerevisiae growth & development, Sirolimus, Viscosity, Proteins chemistry, Proteins genetics
- Abstract
Background: Understanding the cellular role of a protein often requires a means of altering its function, most commonly by mutating the gene encoding the protein. Alternatively, protein function can be altered directly using a small molecule that binds to the protein, but no general method exists for the systematic discovery of small molecule ligands. Split-pool synthesis provides a means of synthesizing vast numbers of small molecules. Synthetic chemists will soon be able to synthesize natural product-like substances by this method, so compatible screening methods that detect the activity of minute quantities of molecules among many inactive ones will be in demand., Results: We describe two advances towards achieving the above goals. First, a technique is described that uses a simple spray gun to create 5000-8000 droplets randomly, each having a volume of 50-200 nanoliters. The individual 'nanodroplets' contain a controlled number of cells and many also contain individual synthesis beads. As small molecules can be photochemically released from the beads in a time-dependent manner, the concentration of ligands that the cells are exposed to can be controlled. The spatial segregation of nanodroplets prevents the mixing of compounds from other beads so the effects of each molecule can be assayed individually. Second, a small molecule-dependent genetic selection involving engineered budding yeast cells was used to detect intracellular protein-ligand interactions in nanodroplets., Conclusions: The technique described here should facilitate the discovery of new cell-permeable ligands, especially when combined with a positive selection assay that detects intracellular binding of small molecules to proteins. Using 'anchored combinatorial libraries', it may be possible to screen entire libraries of natural product-like molecules against the entire collection of proteins encoded within cDNA libraries in a single experiment.
- Published
- 1997
- Full Text
- View/download PDF
49. Radiometric Measurement Comparison Using the Ocean Color Temperature Scanner (OCTS) Visible and Near Infrared Integrating Sphere.
- Author
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Johnson BC, Sakuma F, Butler JJ, Biggar SF, Cooper JW, Ishida J, and Suzuki K
- Abstract
As a part of the pre-flight calibration and validation activities for the Ocean Color and Temperature Scanner (OCTS) and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) ocean color satellite instruments, a radiometric measurement comparison was held in February 1995 at the NEC Corporation in Yokohama, Japan. Researchers from the National Institute of Standards and Technology (NIST), the National Aeronautics and Space Administration/Goddard Space Flight Center (NASA/GSFC), the University of Arizona Optical Sciences Center (UA), and the National Research Laboratory of Metrology (NRLM) in Tsukuba, Japan used their portable radiometers to measure the spectral radiance of the OCTS visible and near-infrared integrating sphere at four radiance levels. These four levels corresponded to the configuration of the OCTS integrating sphere when the calibration coefficients for five of the eight spectral channels, or bands, of the OCTS instrument were determined. The measurements of the four radiometers differed by -2.7 % to 3.9 % when compared to the NEC calibration of the sphere and the overall agreement was within the combined measurement uncertainties. A comparison of the measurements from the participating radiometers also resulted in agreement within the combined measurement uncertainties. These results are encouraging and demonstrate the utility of comparisons using laboratory calibration integrating sphere sources. Other comparisons will focus on instruments that are scheduled for spacecraft in the NASA study of climate change, the Earth Observing System (EOS).
- Published
- 1997
- Full Text
- View/download PDF
50. Dimeric ligands define a role for transcriptional activation domains in reinitiation.
- Author
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Ho SN, Biggar SR, Spencer DM, Schreiber SL, and Crabtree GR
- Subjects
- Alkaline Phosphatase genetics, Binding Sites, Calcineurin, Calmodulin-Binding Proteins metabolism, Carrier Proteins genetics, Carrier Proteins metabolism, DNA metabolism, DNA-Binding Proteins genetics, DNA-Binding Proteins metabolism, Dimerization, Genes, Reporter, Heat-Shock Proteins genetics, Heat-Shock Proteins metabolism, Humans, Jurkat Cells, Ligands, Phosphoprotein Phosphatases metabolism, Polyenes pharmacology, Protein Binding, Recombinant Fusion Proteins genetics, Recombinant Fusion Proteins metabolism, Saccharomyces cerevisiae genetics, Sirolimus, Tacrolimus analogs & derivatives, Tacrolimus chemistry, Tacrolimus metabolism, Tacrolimus pharmacology, Tacrolimus Binding Proteins, Transcription Factors chemistry, Transfection, Transcription Factors physiology, Transcription, Genetic physiology, Transcriptional Activation physiology
- Abstract
Eukaryotic transcriptional activators mediate transcriptional induction through stabilization of the preinitiation complex, probably through direct interactions with basal transcription factors. In vitro studies on the role of an activator in the maintenance of on-going transcription (reinitiation) have been contradictory, suggesting that, after formation of a preinitiation complex, an activator may or may not be necessary for transcription to be maintained. We have developed a means of regulating transcription in living cells through the use of both homodimeric and heterodimerizing synthetic ligands that allow the ligand-dependent association and disassociation of a transcriptional activation domain with a promoter. Here we report that maintaining the transcription of endogenous genes in vivo, in both yeast and human cells, requires the continuous presence of the activation domain. The use of synthetic ligands as a transcriptional on-off switch represents a powerful means of controlling the transcription in vitro and in vivo for both experimental and therapeutic purposes.
- Published
- 1996
- Full Text
- View/download PDF
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