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Search Results: 1 - 10 of 143416 matches for " Jackie K Chan "
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A Method of Drusen Measurement Based on the Geometry of Fundus Reflectance
R Theodore Smith, Takayuki Nagasaki, Janet R Sparrow, Irene Barbazetto, Caroline CW Klaver, Jackie K Chan
BioMedical Engineering OnLine , 2003, DOI: 10.1186/1475-925x-2-10
Abstract: An interactive semi-automated procedure was developed to level the macular background reflectance for the purpose of morphometric analysis of drusen. 12 color fundus photographs of patients with age-related macular degeneration and drusen were analyzed. After digitizing the photographs, the underlying background pattern in the green channel was leveled by an algorithm based on the elliptically concentric geometry of the reflectance in the normal macula: the gray scale values of all structures within defined elliptical boundaries were raised sequentially until a uniform background was obtained. Segmentation of drusen and area measurements in the central and middle subfields (1000 μm and 3000 μm diameters) were performed by uniform thresholds. Two observers using this interactive semi-automated software measured each image digitally. The mean digital measurements were compared to independent stereo fundus gradings by two expert graders (stereo Grader 1 estimated the drusen percentage in each of the 24 regions as falling into one of four standard broad ranges; stereo Grader 2 estimated drusen percentages in 1% to 5% intervals).The mean digital area measurements had a median standard deviation of 1.9%. The mean digital area measurements agreed with stereo Grader 1 in 22/24 cases. The 95% limits of agreement between the mean digital area measurements and the more precise stereo gradings of Grader 2 were -6.4 % to +6.8 % in the central subfield and -6.0 % to +4.5 % in the middle subfield. The mean absolute differences between the digital and stereo gradings 2 were 2.8 +/- 3.4% in the central subfield and 2.2 +/- 2.7% in the middle subfield.Semi-automated, supervised drusen measurements may be done reproducibly and accurately with adaptations of commercial software. This technique for macular image analysis has potential for use in clinical research.Color fundus photographs have been routinely employed for diagnostic purposes for many years, and fundus photo gradings are c
Consortium for the Human Information and Neurocognitive Endophenotype (CHINE) in mainland China: An example from neurological soft signs for neuropsychiatric disorders
Raymond C. K. Chan
Chinese Science Bulletin , 2011, DOI: 10.1007/s11434-011-4715-5
Abstract: Increasing efforts to identify alternate expressions of neuropsychiatric disorders that are broader than the DSM or ICD diagnostic criteria needed to diagnose them reflects a growing consensus that multidimensional expressions of neuropsychiatric disorders may advance the search for underlying etiological or modulatory factors. Endophenotypic research can be considered to be one of the most promising strategies to bridge the gap between genomic complexity and the phenotypic heterogeneity observed in neuropsychiatric disorders. However, the majority of endophenotype studies were limited to our western counterparts, very little has been done and initiated by scholars in mainland China. In this paper, we urge the need to establish a potential central consortium for endophenotypes to study neuropsychiatric disorders in mainland China. In particular, we illustrate a potential example of neurological soft signs in following the steps for building the consortium.
A review on human influenza A H5N1 infections in Hong Kong
Paul K. S. Chan
Science China Life Sciences , 2009, DOI: 10.1007/s11427-009-0063-y
Abstract: Avian influenza A H5N1 remains the most threatening virus that may cause another devastating pandemic in the foreseeable future. In 1997, Hong Kong was the first place to detect human infections due to this virus originated from birds. The experience and lessons learnt provide important information for controlling further outbreaks caused by avian influenza viruses.
Case 3
Elisa K. Chan
University of Toronto Medical Journal , 2003, DOI: 10.5015/utmj.v80i2.787
Abstract:
Associating Educational Psychology Theories in a Curriculum to maximise Student Participation
Cecilia K. Y Chan
Journal of Studies in Education , 2012, DOI: 10.5296/jse.v2i3.1712
Abstract: Psychology has existed for a long time in the academic field of engineering education although many teachers are unaware or unfamiliar with the psychological theories and associated terms. This paper discusses how psychology is related to engineering education, from the development of the curriculum to the delivery and assessment process and how each student and teacher affiliate with one another. It pays particular attention to the development of an electrical engineering first year degree program in Ireland and presents some humanistic approaches in targeting student motivation.
Comment on the Calculation of the Angular Momentum and Mass for the (Anti-) Self Dual Charged Spinning $BTZ$ Black Hole
Kevin C. K. Chan
Physics , 1995, DOI: 10.1016/0370-2693(96)00145-1
Abstract: A recent paper [M. Kamata and T. Koikawa, Phys. Lett. {\bf B353} (1995) 196.] claimed to obtain the charged version of the $(2+1)$-dimensional spinning $BTZ$ black hole solution by assuming a (anti-) self dual condition imposed on the electric and magnetic fields. We point out that the angular momentum and mass diverge at spatial infinity and as a consequence the solution is unphysical
Modifications of the BTZ black hole by a dilaton/scalar
Kevin C. K. Chan
Physics , 1996, DOI: 10.1103/PhysRevD.55.3564
Abstract: We investigate some modifications of the static BTZ black hole solution due to a chosen asymptotically constant dilaton/scalar. New classes of static black hole solutions are obtained. One of the solutions contains the Martinez-Zanelli conformal black hole solution as a special case. Using quasilocal formalism, we calculate their mass for a finite spatial region that contains the black hole. Their temperatures are also computed. Finally, using some of the curvature singularities as examples, we investigate whether a quantum particle behaves singularly or not.
Is mass conformally invariant?
Kevin C. K. Chan
Physics , 1997,
Abstract: By using the Garfinkle, Horowitz and Strominger black hole solutions as examples, we illustrate that, with respect to the reference action functional proposed by Hawking and Horowitz, the asymptotic mass parameter is not invariant between two conformally related static spherically symmetric metrics.
Mass transfer effects in hygroscopic measurements of aerosol particles
M. N. Chan,C. K. Chan
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2005,
Abstract: The tandem differential mobility analyzer (TDMA) has been widely utilized to measure the hygroscopicity of laboratory-generated and atmospheric submicrometer particles. An important concern in investigating the hygroscopicity of the particles is if the particles have attained equilibrium state in the measurements. We present a literature survey to investigate the mass transfer effects in hygroscopicity measurements. In most TDMA studies, a residence time in the order of seconds is used for humidification (or dehumidification). NaCl and (NH4)2SO4 particles are usually used to verify the equilibrium measurements during this residence time, which is presumed to be sufficient for other particles. There have been observations that not all types of submicrometer particles, including atmospheric particles, attain their equilibrium sizes within this time scale. We recommend that experimentation with different residence times be conducted and that the residence time should be explicitly stated in future TDMA measurements. Mass transfer effects may also exist in the measurements of other properties related to the water uptake of atmospheric particles such as relative humidity dependent light scattering coefficients and cloud condensation nuclei activity.
Mass transfer effects in hygroscopic measurements of aerosol particles
M. N. Chan,C. K. Chan
Atmospheric Chemistry and Physics Discussions , 2005,
Abstract: The tandem differential mobility analyzer (TDMA) has been widely utilized to measure the hygroscopicity of laboratory-generated and atmospheric submicrometer particles. An important concern in investigating the hygroscopicity of the particles is if the particles have attained equilibrium state in the measurements. We present a literature survey to investigate the mass transfer effects in hygroscopicity measurements. In most TDMA studies, a residence time in the order of seconds is used for humidification (or dehumidification). NaCl and (NH4)2SO4 particles are usually used to verify the equilibrium measurements during this residence time, which is presumed to be sufficient for other particles. There have been observations that not all types of submicrometer particles, including atmospheric particles, attain their equilibrium sizes within this time scale. We recommend that experimentation with different residence times be conducted and that the residence time should be explicitly stated in future TDMA measurements. Mass transfer effects may also exist in the measurements of other properties related to the water uptake of atmospheric particles such as relative humidity dependent light scattering coefficients and cloud condensation nuclei activity.
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