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1. The Detector System of The Daya Bay Reactor Neutrino Experiment

Author

An, F. P., Bai, J. Z., Balantekin, A. B., Band, H. R., Beavis, D., Beriguete, W., Bishai, M., Blyth, S., Brown, R. L., Butorov, I., Cao, D., Cao, G. F., Cao, J., Carr, R., Cen, W. R., Chan, W. T., Chan, Y. L., Chang, J. F., Chang, L. C., Chang, Y., Chasman, C., Chen, H. Y., Chen, H. S., Chen, M. J., Chen, Q. Y., Chen, S. J., Chen, S. M., Chen, X. C., Chen, X. H., Chen, X. S., Chen, Y. X., Chen, Y., Cheng, J. H., Cheng, J., Cheng, Y. P., Cherwinka, J. J., Chidzik, S., Chow, K., Chu, M. C., Cummings, J. P., de Arcos, J., Deng, Z. Y., Ding, X. F., Ding, Y. Y., Diwan, M. V., Dong, L., Dove, J., Draeger, E., Du, X. F., Dwyer, D. A., Edwards, W. R., Ely, S. R., Fang, S. D., Fu, J. Y., Fu, Z. W., Ge, L. Q., Ghazikhanian, V., Gill, R., Goett, J., Gonchar, M., Gong, G. H., Gong, H., Gornushkin, Y. A., Grassi, M., Greenler, L. S., Gu, W. Q., Guan, M. Y., Guo, R. P., Guo, X. H., Hackenburg, R. W., Hahn, R. L., Han, R., Hans, S., He, M., He, Q., He, W. S., Heeger, K. M., Heng, Y. K., Higuera, A., Hinrichs, P., Ho, T. H., Hoff, M., Hor, Y. K., Hsiung, Y. B., Hu, B. Z., Hu, L. M., Hu, L. J., Hu, T., Hu, W., Huang, E. C., Huang, H. Z., Huang, H. X., Huang, P. W., Huang, X., Huang, X. T., Huber, P., Hussain, G., Isvan, Z., Jaffe, D. E., Jaffke, P., Jen, K. L., Jetter, S., Ji, X. P., Ji, X. L., Jiang, H. J., Jiang, W. Q., Jiao, J. B., Johnson, R. A., Joseph, J., Kang, L., Kettell, S. H., Kohn, S., Kramer, M., Kwan, K. K., Kwok, M. W., Kwok, T., Lai, C. Y., Lai, W. C., Lai, W. H., Langford, T. J., Lau, K., Lebanowski, L., Lee, J., Lee, M. K. P., Lei, R. T., Leitner, R., Leung, J. K. C., Leung, K. Y., Lewis, C. A., Li, B., Li, C., Li, D. J., Li, F., Li, G. S., Li, J., Li, N. Y., Li, Q. J., Li, S. F., Li, S. C., Li, W. D., Li, X. B., Li, X. N., Li, X. Q., Li, Y., Li, Y. F., Li, Z. B., Liang, H., Liang, J., Lin, C. J., Lin, G. L., Lin, P. Y., Lin, S. X., Lin, S. K., Lin, Y. C., Ling, J. J., Link, J. M., Littenberg, L., Littlejohn, B. R., Liu, B. J., Liu, C., Liu, D. W., Liu, H., Liu, J. L., Liu, J. C., Liu, S., Liu, S. S., Liu, X., Liu, Y. B., Lu, C., Lu, H. Q., Lu, J. S., Luk, A., Luk, K. B., Luo, T., Luo, X. L., Ma, L. H., Ma, Q. M., Ma, X. Y., Ma, X. B., Ma, Y. Q., Mayes, B., McDonald, K. T., McFarlane, M. C., McKeown, R. D., Meng, Y., Mitchell, I., Mohapatra, D., Kebwaro, J. Monari, Morgan, J. E., Nakajima, Y., Napolitano, J., Naumov, D., Naumova, E., Newsom, C., Ngai, H. Y., Ngai, W. K., Nie, Y. B., Ning, Z., Ochoa-Ricoux, J. P., Olshevskiy, A., Pagac, A., Pan, H. -R., Patton, S., Pearson, C., Pec, V., Peng, J. C., Piilonen, L. E., Pinsky, L., Pun, C. S. J., Qi, F. Z., Qi, M., Qian, X., Raper, N., Ren, B., Ren, J., Rosero, R., Roskovec, B., Ruan, X. C., Sands III, W. R., Seilhan, B., Shao, B. B., Shih, K., Song, W. Y., Steiner, H., Stoler, P., Stuart, M., Sun, G. X., Sun, J. L., Tagg, N., Tam, Y. H., Tanaka, H. K., Tang, W., Tang, X., Taychenachev, D., Themann, H., Torun, Y., Trentalange, S., Tsai, O., Tsang, K. V., Tsang, R. H. M., Tull, C. E., Tung, Y. C., Viaux, N., Viren, B., Virostek, S., Vorobel, V., Wang, C. H., Wang, L. S., Wang, L. Y., Wang, L. Z., Wang, M., Wang, N. Y., Wang, R. G., Wang, T., Wang, W., Wang, W. W., Wang, X. T., Wang, X., Wang, Y. F., Wang, Z., Wang, Z. M., Webber, D. M., Wei, H. Y., Wei, Y. D., Wen, L. J., Wenman, D. L., Whisnant, K., White, C. G., Whitehead, L., Whitten Jr., C. A., Wilhelmi, J., Wise, T., Wong, H. C., Wong, H. L. H., Wong, J., Wong, S. C. F., Worcester, E., Wu, F. F., Wu, Q., Xia, D. M., Xia, J. K., Xiang, S. T., Xiao, Q., Xing, Z. Z., Xu, G., Xu, J. Y., Xu, J. L., Xu, J., Xu, W., Xu, Y., Xue, T., Yan, J., Yang, C. G., Yang, L., Yang, M. S., Yang, M. T., Ye, M., Yeh, M., Yeh, Y. S., Yip, K., Young, B. L., Yu, G. Y., Yu, Z. Y., Zeng, S., Zhan, L., Zhang, C., Zhang, F. H., Zhang, H. H., Zhang, J. W., Zhang, K., Zhang, Q. X., Zhang, Q. M., Zhang, S. H., Zhang, X. T., Zhang, Y. C., Zhang, Y. H., Zhang, Y. M., Zhang, Y. X., Zhang, Z. J., Zhang, Z. Y., Zhang, Z. P., Zhao, J., Zhao, Q. W., Zhao, Y. F., Zhao, Y. B., Zheng, L., Zhong, W. L., Zhou, L., Zhou, N., Zhou, Z. Y., Zhuang, H. L., Zimmerman, S., and Zou, J. H.

Subjects
Physics - Instrumentation and Detectors, High Energy Physics - Experiment
Abstract

The Daya Bay experiment was the first to report simultaneous measurements of reactor antineutrinos at multiple baselines leading to the discovery of $\bar{\nu}_e$ oscillations over km-baselines. Subsequent data has provided the world's most precise measurement of $\rm{sin}^22\theta_{13}$ and the effective mass splitting $\Delta m_{ee}^2$. The experiment is located in Daya Bay, China where the cluster of six nuclear reactors is among the world's most prolific sources of electron antineutrinos. Multiple antineutrino detectors are deployed in three underground water pools at different distances from the reactor cores to search for deviations in the antineutrino rate and energy spectrum due to neutrino mixing. Instrumented with photomultiplier tubes (PMTs), the water pools serve as shielding against natural radioactivity from the surrounding rock and provide efficient muon tagging. Arrays of resistive plate chambers over the top of each pool provide additional muon detection. The antineutrino detectors were specifically designed for measurements of the antineutrino flux with minimal systematic uncertainty. Relative detector efficiencies between the near and far detectors are known to better than 0.2%. With the unblinding of the final two detectors' baselines and target masses, a complete description and comparison of the eight antineutrino detectors can now be presented. This paper describes the Daya Bay detector systems, consisting of eight antineutrino detectors in three instrumented water pools in three underground halls, and their operation through the first year of eight detector data-taking., Comment: 52 pages, 51 figures

Published
2015
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2. Improved Measurement of Electron Antineutrino Disappearance at Daya Bay

Author

Daya Bay Collaboration, An, F. P., An, Q., Bai, J. Z., Balantekin, A. B., Band, H. R., Beriguete, W., Bishai, M., Blyth, S., Brown, R. L., Cao, G. F., Cao, J., Carr, R., Chan, W. T., Chang, J. F., Chang, Y., Chasman, C., Chen, H. S., Chen, H. Y., Chen, S. J., Chen, S. M., Chen, X. C., Chen, X. H., Chen, X. S., Chen, Y., Chen, Y. X., Cherwinka, J. J., Chu, M. C., Cummings, J. P., Deng, Z. Y., Ding, Y. Y., Diwan, M. V., Draeger, E., Du, X. F., Dwyer, D., Edwards, W. R., Ely, S. R., Fang, S. D., Fu, J. Y., Fu, Z. W., Ge, L. Q., Gill, R. L., Gonchar, M., Gong, G. H., Gong, H., Gornushkin, Y. A., Gu, W. Q., Guan, M. Y., Guo, X. H., Hackenburg, R. W., Hahn, R. L., Hans, S., Hao, H. F., He, M., He, Q., Heeger, K. M., Heng, Y. K., Hinrichs, P., Hor, Y. K., Hsiung, Y. B., Hu, B. Z., Hu, T., Huang, H. X., Huang, H. Z., Huang, X. T., Huber, P., Issakov, V., Isvan, Z., Jaffe, D. E., Jetter, S., Ji, X. L., Ji, X. P., Jiang, H. J., Jiao, J. B., Johnson, R. A., Kang, L., Kettell, S. H., Kramer, M., Kwan, K. K., Kwok, M. W., Kwok, T., Lai, C. Y., Lai, W. C., Lai, W. H., Lau, K., Lebanowski, L., Lee, J., Lei, R. T., Leitner, R., Leung, J. K. C., Leung, K. Y., Lewis, C. A., Li, F., Li, G. S., Li, Q. J., Li, W. D., Li, X. B., Li, X. N., Li, X. Q., Li, Y., Li, Z. B., Liang, H., Lin, C. J., Lin, G. L., Lin, S. K., Lin, Y. C., Ling, J. J., Link, J. M., Littenberg, L., Littlejohn, B. R., Liu, D. W., Liu, J. C., Liu, J. L., Liu, Y. B., Lu, C., Lu, H. Q., Luk, A., Luk, K. B., Ma, Q. M., Ma, X. B., Ma, X. Y., Ma, Y. Q., McDonald, K. T., McFarlane, M. C., McKeown, R. D., Meng, Y., Mohapatra, D., Nakajima, Y., Napolitano, J., Naumov, D., Nemchenok, I., Ngai, H. Y., Ngai, W. K., Nie, Y. B., Ning, Z., Ochoa-Ricoux, J. P., Olshevski, A., Patton, S., Pec, V., Peng, J. C., Piilonen, L. E., Pinsky, L., Pun, C. S. J., Qi, F. Z., Qi, M., Qian, X., Raper, N., Ren, J., Rosero, R., Roskovec, B., Ruan, X. C., Shao, B. B., Shih, K., Steiner, H., Sun, G. X., Sun, J. L., Tagg, N., Tam, Y. H., Tanaka, H. K., Tang, X., Themann, H., Torun, Y., Trentalange, S., Tsai, O., Tsang, K. V., Tsang, R. H. M., Tull, C. E., Tung, Y. C., Viren, B., Vorobel, V., Wang, C. H., Wang, L. S., Wang, L. Y., Wang, L. Z., Wang, M., Wang, N. Y., Wang, R. G., Wang, W., Wang, X., Wang, Y. F., Wang, Z., Wang, Z. M., Webber, D. M., Wei, H. Y., Wei, Y. D., Wen, L. J., Whisnant, K., White, C. G., Whitehead, L., Williamson, Y., Wise, T., Wong, H. L. H., Worcester, E. T., Wu, F. F., Wu, Q., Xi, J. B., Xia, D. M., Xing, Z. Z., Xu, J., Xu, J. L., Xu, Y., Xue, T., Yang, C. G., Yang, L., Ye, M., Yeh, M., Yeh, Y. S., Young, B. L., Yu, Z. Y., Zhan, L., Zhang, C., Zhang, F. H., Zhang, J. W., Zhang, Q. M., Zhang, S. H., Zhang, Y. C., Zhang, Y. H., Zhang, Y. X., Zhang, Z. J., Zhang, Z. P., Zhang, Z. Y., Zhao, J., Zhao, Q. W., Zhao, Y. B., Zheng, L., Zhong, W. L., Zhou, L., Zhou, Z. Y., Zhuang, H. L., and Zou, J. H.

Subjects
High Energy Physics - Experiment, Nuclear Experiment
Abstract

We report an improved measurement of the neutrino mixing angle $\theta_{13}$ from the Daya Bay Reactor Neutrino Experiment. We exclude a zero value for $\sin^22\theta_{13}$ with a significance of 7.7 standard deviations. Electron antineutrinos from six reactors of 2.9 GW$_{\rm th}$ were detected in six antineutrino detectors deployed in two near (flux-weighted baselines of 470 m and 576 m) and one far (1648 m) underground experimental halls. Using 139 days of data, 28909 (205308) electron antineutrino candidates were detected at the far hall (near halls). The ratio of the observed to the expected number of antineutrinos assuming no oscillations at the far hall is $0.944\pm 0.007({\rm stat.}) \pm 0.003({\rm syst.})$. An analysis of the relative rates in six detectors finds $\sin^22\theta_{13}=0.089\pm 0.010({\rm stat.})\pm0.005({\rm syst.})$ in a three-neutrino framework., Comment: 21 pages, 24 figures. Submitted to and accepted by Chinese Physics C. Two typos were corrected. Description improved

Published
2012
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3. Observation of electron-antineutrino disappearance at Daya Bay

Author

An, F. P., Bai, J. Z., Balantekin, A. B., Band, H. R., Beavis, D., Beriguete, W., Bishai, M., Blyth, S., Boddy, K., Brown, R. L., Cai, B., Cao, G. F., Cao, J., Carr, R., Chan, W. T., Chang, J. F., Chang, Y., Chasman, C., Chen, H. S., Chen, H. Y., Chen, S. J., Chen, S. M., Chen, X. C., Chen, X. H., Chen, X. S., Chen, Y., Chen, Y. X., Cherwinka, J. J., Chu, M. C., Cummings, J. P., Deng, Z. Y., Ding, Y. Y., Diwan, M. V., Dong, L., Draeger, E., Du, X. F., Dwyer, D. A., Edwards, W. R., Ely, S. R., Fang, S. D., Fu, J. Y., Fu, Z. W., Ge, L. Q., Ghazikhanian, V., Gill, R. L., Goett, J., Gonchar, M., Gong, G. H., Gong, H., Gornushkin, Y. A., Greenler, L. S., Gu, W. Q., Guan, M. Y., Guo, X. H., Hackenburg, R. W., Hahn, R. L., Hans, S., He, M., He, Q., He, W. S., Heeger, K. M., Heng, Y. K., Hinrichs, P., Ho, T. H., Hor, Y. K., Hsiung, Y. B., Hu, B. Z., Hu, T., Huang, H. X., Huang, H. Z., Huang, P. W., Huang, X., Huang, X. T., Huber, P., Isvan, Z., Jaffe, D. E., Jetter, S., Ji, X. L., Ji, X. P., Jiang, H. J., Jiang, W. Q., Jiao, J. B., Johnson, R. A., Kang, L., Kettell, S. H., Kramer, M., Kwan, K. K., Kwok, M. W., Kwok, T., Lai, C. Y., Lai, W. C., Lai, W. H., Lau, K., Lebanowski, L., Lee, J., Lee, M. K. P., Leitner, R., Leung, J. K. C., Leung, K. Y., Lewis, C. A., Li, B., Li, F., Li, G. S., Li, J., Li, Q. J., Li, S. F., Li, W. D., Li, X. B., Li, X. N., Li, X. Q., Li, Y., Li, Z. B., Liang, H., Liang, J., Lin, C. J., Lin, G. L., Lin, S. K., Lin, S. X., Lin, Y. C., Ling, J. J., Link, J. M., Littenberg, L., Littlejohn, B. R., Liu, B. J., Liu, C., Liu, D. W., Liu, H., Liu, J. C., Liu, J. L., Liu, S., Liu, X., Liu, Y. B., Lu, C., Lu, H. Q., Luk, A., Luk, K. B., Luo, T., Luo, X. L., Ma, L. H., Ma, Q. M., Ma, X. B., Ma, X. Y., Ma, Y. Q., Mayes, B., McDonald, K. T., McFarlane, M. C., McKeown, R. D., Meng, Y., Mohapatra, D., Morgan, J. E., Nakajima, Y., Napolitano, J., Naumov, D., Nemchenok, I., Newsom, C., Ngai, H. Y., Ngai, W. K., Nie, Y. B., Ning, Z., Ochoa-Ricoux, J. P., Oh, D., Olshevski, A., Pagac, A., Patton, S., Pearson, C., Pec, V., Peng, J. C., Piilonen, L. E., Pinsky, L., Pun, C. S. J., Qi, F. Z., Qi, M., Qian, X., Raper, N., Rosero, R., Roskovec, B., Ruan, X. C., Seilhan, B., Shao, B. B., Shih, K., Steiner, H., Stoler, P., Sun, G. X., Sun, J. L., Tam, Y. H., Tanaka, H. K., Tang, X., Themann, H., Torun, Y., Trentalange, S., Tsai, O., Tsang, K. V., Tsang, R. H. M., Tull, C., Viren, B., Virostek, S., Vorobel, V., Wang, C. H., Wang, L. S., Wang, L. Y., Wang, L. Z., Wang, M., Wang, N. Y., Wang, R. G., Wang, T., Wang, W., Wang, X., Wang, Y. F., Wang, Z., Wang, Z. M., Webber, D. M., Wei, Y. D., Wen, L. J., Wenman, D. L., Whisnant, K., White, C. G., Whitehead, L., Whitten Jr., C. A., Wilhelmi, J., Wise, T., Wong, H. C., Wong, H. L. H., Wong, J., Worcester, E. T., Wu, F. F., Wu, Q., Xia, D. M., Xiang, S. T., Xiao, Q., Xing, Z. Z., Xu, G., Xu, J., Xu, J. L., Xu, W., Xu, Y., Xue, T., Yang, C. G., Yang, L., Ye, M., Yeh, M., Yeh, Y. S., Yip, K., Young, B. L., Yu, Z. Y., Zhan, L., Zhang, C., Zhang, F. H., Zhang, J. W., Zhang, Q. M., Zhang, K., Zhang, Q. X., Zhang, S. H., Zhang, Y. C., Zhang, Y. H., Zhang, Y. X., Zhang, Z. J., Zhang, Z. P., Zhang, Z. Y., Zhao, J., Zhao, Q. W., Zhao, Y. B., Zheng, L., Zhong, W. L., Zhou, L., Zhou, Z. Y., Zhuang, H. L., and Zou, J. H.

Subjects
High Energy Physics - Experiment
Abstract

The Daya Bay Reactor Neutrino Experiment has measured a non-zero value for the neutrino mixing angle $\theta_{13}$ with a significance of 5.2 standard deviations. Antineutrinos from six 2.9 GW$_{\rm th}$ reactors were detected in six antineutrino detectors deployed in two near (flux-weighted baseline 470 m and 576 m) and one far (1648 m) underground experimental halls. With a 43,000 ton-GW_{\rm th}-day livetime exposure in 55 days, 10416 (80376) electron antineutrino candidates were detected at the far hall (near halls). The ratio of the observed to expected number of antineutrinos at the far hall is $R=0.940\pm 0.011({\rm stat}) \pm 0.004({\rm syst})$. A rate-only analysis finds $\sin^22\theta_{13}=0.092\pm 0.016({\rm stat})\pm0.005({\rm syst})$ in a three-neutrino framework., Comment: 5 figures. Version to appear in Phys. Rev. Lett

Published
2012
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4. The chemistry of the hypersilyl and related ligands

Author

Chan, W. T. K.

Subjects
546.3
Abstract

This thesis is mainly focused on the investigation of the chemistry and reactivity of the hypersilyl ligand {[(Me3Si)3Si]-}, and the rationalisation of the use of siloxanes as precursors ([(R2SiO)n]). A total of ten new compounds have been prepared from these studies, and X-ray crystallography forms a central basis of the analysis of these species, along with NMR spectroscopy and various other analytical techniques. The first novel compound described is [(Ph3Si)(Me3Si)2SiK.18-crown-6] (3). Despite isolating 3 in pure both crystalline and powder form the difficulty in synthesising the compound in large scale meant that its reactivity could not be investigated fully. A series of Si-M complexes was made in the form of [(Me3Si)3Si.MX3]-[K.18-crown-6]+ (4-6, M = Al or Ga, X = Cl or Br), as well as [(Ph3Si)(Me3Si)2Si.GaCl3]-[K.18-crown-6]+ through the reaction of the respective silyl anion with the corresponding group 13 halides. Due to yield considerations, 6 was chosen as a precursor to study the thermal decomposition behaviour of this type of compounds. The reaction between (Me3Si)3SiK.18-crown-6 (1a) with (P4) led to the formation of the unusual {P8[(Me3Si)3Si]2.K.18-crown-6}-[K.18-crown-6.(THF)2]+ (8). The discovery of 8 allows an investigation into the relatively poorly understood mechanism for this type of reaction, and a proposed mechanism, supported by computational calculations, is discussed. The reaction between hypersilyl potassium (1a) and mesityl nitrile gave 6,8-dimethyl-1-amino-3-mesityl-isoquinoline. Finally, the unexpected formation of [2-PySi(Me)2LiO]6 and {[18-crown-6.]GaCl4}∞ are also described.

Published
2009

7. Combined dietary and exercise intervention for control of serum cholesterol in the workplace

Author

Angotti, C. M, Chan, W. T, Sample, C. J, and Levine, M. S

Subjects
Life Sciences (General)
Abstract

PURPOSE: To elucidate a potential combined dietary and exercise intervention affect on cardiovascular risk reduction of the National Aeronautics and Space Administration Headquarters employees. DESIGN: A nonexperimental, longitudinal, clinical-chart review study (1987 to 1996) of an identified intervention group and a reference (not a control) group. SETTING: The study group worked in an office environment and participated in the annual medical examinations. SUBJECTS: An intervention group of 858 people with initially elevated serum cholesterol, and a reference group of 963 people randomly sampled from 10% of the study group. MEASURES: Serum cholesterol data were obtained for both groups, respectively, from pre- and postintervention and annual examinations. The reference group was adjusted by statistical exclusion of potential intervention participants. Regression equations (cholesterol vs. study years) for the unadjusted/adjusted reference groups were tested for statistical significance. INTERVENTION: An 8-week individualized, combined dietary and exercise program was instituted with annual follow-ups and was repeated where warranted. RESULTS: Only the unadjusted (but not the adjusted) reference group with initial mean total serum cholesterol levels above 200 mg/dL shows a significant 9-year decline trend and significant beta coefficient tests. An intervention effect is suggested. Mean high density lipoprotein cholesterol rose slightly in the intervention group but was maintained in the reference group. CONCLUSION: With potential design limitations, the NASA intervention program focusing on a high risk group may be associated to some degree, if not fully, with an overall cardiovascular risk profile improvement.

Published
2000

9. Termination Factor for Iterative Noise Reduction in MRI Images Using Histograms of Second-order Derivatives.

Author

Chan, W. T. and Sim, K. S.

Subjects
MAGNETIC resonance imaging, HISTOGRAMS, PARTICLE image velocimetry
Abstract

Histograms of second-order derivatives are generated from the pixel data of MRI images. The histograms are then used to calculate a factor that is to be used for iterative processing. The factor is intended to limit the number of iterations, with the goal of preventing further loss of detail. The factor uses two conditions that depend on the profiles of the histograms. The methodology uses sample MRI images and versions of these images with Rician noise introduced into them. The noisy images are subjected to iterative noise reduction with a recursive averaging filter. The control tests in the methodology use the ground truth images to limit the number of iterations, with PSNR and SSIM peaks used as the measurements for determining when the iterations stop. The other tests use the proposed termination factor for the limitation. The results of the tests are compared to determine the effectiveness of the termination factor. The proposed termination factor does not cause divergence, but there are still different numbers of iterations in the case of MRI images with image subjects that have discrete regions and details resembling noise. The tests also reveal that differences between the histograms of derivatives and Laplace curves have to be retained in order to prevent loss of information. [ABSTRACT FROM AUTHOR]

Published
2021

10. Contrast Measurement with Histograms of Second-order Derivatives of Pixels for Magnetic Resonance Images.

Author

Chan, W. T., Sim, K. S., and Abas, F. S.

Subjects
*HISTOGRAMS, *PIXELS, *MAGNETIC resonance imaging, *LAPLACE distribution, *IMAGE intensifiers
Abstract

Second-order derivatives are used to obtain more information from the pixels in a magnetic resonance image. This information is the difference between the values of pixels, which is a factor in the measurement of the level of contrast in the image. This information is presented in the form of a histogram of second-order values, which expresses differences in pixel values caused by contrast between details in the image. The proposed method of contrast measurement utilizes a Laplace curve together with the histogram, both of which are generated with image data. The curve and histogram are used to determine a measurement quantity that expresses the level of contrast and the presence of details in the image. The measurement quantity, which is a score, describes the change of contrast in the image as contrast enhancement is applied. This score is compared with other established contrast scores that utilize data from an individual image, without comparison to another image. These other scores are average local contrast, root mean square contrast and Michelson contrast. The goal of the comparison is to determine the performance of the proposed score at detecting the occurrence of excessive gain as contrast enhancement is applied on an MRI image. Sample MRI images, including images from established databases, are used for the testing and comparison. The proposed score performs better than average local contrast and root mean square contrast and provides results that do not diverge as gain is increased. [ABSTRACT FROM AUTHOR]

Published
2019

11. CASE-BASED REASONING APPROACH IN BID DECISION MAKING

Author

Chua, D. K. H., Li, D. Z., and Chan, W. T.

Subjects
Contractors -- Behavior, Decision-making -- Models, Construction and materials industries, Engineering and manufacturing industries, Science and technology
Abstract

Since contractors' bidding behaviors are affected by numerous factors related both to the specific features of the project and dynamically changed situations, bidding decision problems are highly unstructured. No clear rules can be found in delivering a bidding decision. In this problem domain, decisions are commonly made based upon intuition and past experience. Case-based reasoning (CBR) is a subbranch of artificial intelligence. It solves new problems by matching against similar problems that have been encountered and resolved in the past. It is a useful tool in dealing with complex and unstructured problems, which are difficult if not impossible to be theoretically modeled. This paper presents a case-based reasoning bidding system that helps contractors with the dynamic information varying with the specific features of the job and the new situation. In this system, bid cases are represented by sets of attributes derived from a preliminary survey of several experienced bidders, focusing, respectively, on two reasoning subgoals: (1) Risk; and (2) competition. Through the system, similar cases can be retrieved to assess the possible level of competition and risk margin. A hypothetical example is explained and evaluated to demonstrate the feasibility of the method. The effectiveness of this system is tested by a Monte Carlo simulation in comparison to the conventional statistical method.

Published
2001

13. Observation of Electron-Antineutrino Disappearance at Daya Bay

Author

Center for Neutrino Physics, Physics, An, F. P., Bai, J. Z., Balantekin, A. B., Band, H. R., Beavis, D., Beriguete, W., Bishai, M., Blyth, S., Boddy, K., Brown, R. L., Cai, B., Cao, G. F., Cao, J., Carr, Rachel E., Chan, W. T., Chang, J. F., Chang, Y., Chasman, C., Chen, H. S., Chen, H. Y., Chen, S. J., Chen, S. M., Chen, X. C., Chen, X. H., Chen, X. S., Chen, Y., Chen, Y. X., Cherwinka, J. J., Chu, M. C., Cummings, J. P., Deng, Z. Y., Ding, Y. Y., Diwan, M. V., Dong, L., Draeger, E., Du, X. F., Dwyer, D. A., Edwards, W. R., Ely, S. R., Fang, S. D., Fu, J. Y., Fu, Z. W., Ge, L. Q., Ghazikhanian, V., Gill, R. L., Goett, J., Gonchar, M., Gong, G. H., Gong, H., Gornushkin, Y. A., Greenler, L. S., Gu, W. Q., Guan, M. Y., Guo, X. H., Hackenburg, R. W., Hahn, R. L., Hans, S., He, M., He, Q., He, W. S., Heeger, K. M., Heng, Y. K., Hinrichs, P., Ho, T. H., Hor, Y. K., Hsiung, Y. B., Hu, B. Z., Hu, T., Huang, H. X., Huang, H. Z., Huang, P. W., Huang, X., Huang, X. T., Huber, Patrick, Isvan, Z., Jaffe, D. E., Jetter, S., Ji, X. L., Ji, X. P., Jiang, H. J., Jiang, W. Q., Jiao, J. B., Johnson, R. A., Kang, L., Kettell, S. H., Kramer, M., Kwan, K. K., Kwok, M. W., Kwok, T., Lai, C. Y., Lai, W. C., Lai, W. H., Lau, K., Lebanowski, L., Lee, J., Lee, M. K. P., Leitner, R., Leung, J. K. C., Leung, K. Y., Lewis, C. A., Li, B., Li, F., Li, G. S., Li, J., Li, Q. J., Li, S. F., Li, W. D., Li, X. B., Li, X. N., Li, X. Q., Li, Y., Li, Z. B., Liang, H., Liang, J., Lin, C. J., Lin, G. L., Lin, S. K., Lin, S. X., Lin, Y. C., Ling, J. J., Link, Jonathan M., Littenberg, L., Littlejohn, B. R., Liu, B. J., Liu, C., Liu, D. W., Liu, H., Liu, J. C., Liu, J. L., Liu, S., Liu, X., Liu, Y. B., Lu, C., Lu, H. Q., Luk, A., Luk, K. B., Luo, T., Luo, X. L., Ma, L. H., Ma, Q. M., Ma, X. B., Ma, X. Y., Ma, Y. Q., Mayes, B., McDonald, K. T., McFarlane, M. C., McKeown, R. D., Meng, Y., Mohapatra, D., Morgan, J. E., Nakajima, Y., Napolitano, J., Naumov, D., Nemchenok, I., Newsom, C., Ngai, H. Y., Ngai, W. K., Nie, Y. B., Ning, Z., Ochoa-Ricoux, J. P., Oh, D., Olshevski, A., Pagac, A., Patton, S., Pearson, C., Pec, V., Peng, J. C., Piilonen, Leo E., Pinsky, L., Pun, C. S. J., Qi, F. Z., Qi, M., Qian, X., Raper, N., Rosero, R., Roskovec, B., Ruan, X. C., Seilhan, B., Shao, B. B., Shih, K., Steiner, H., Stoler, P., Sun, G. X., Sun, J. L., Tam, Y. H., Tanaka, H. K., Tang, X., Themann, H., Torun, Y., Trentalange, S., Tsai, O., Tsang, K. V., Tsang, R. H. M., Tull, C., Viren, B., Virostek, S., Vorobel, V., Wang, C. H., Wang, L. S., Wang, L. Y., Wang, L. Z., Wang, M., Wang, N. Y., Wang, R. G., Wang, T., Wang, W., Wang, X., Wang, Y. F., Wang, Z., Wang, Z. M., Webber, D. M., Wei, Y. D., Wen, L. J., Wenman, D. L., Whisnant, K., White, C. G., Whitehead, L., Whitten, C. A., Wilhelmi, J., Wise, T., Wong, H. C., Wong, H. L. H., Wong, J., Worcester, E., Wu, F. F., Wu, Q., Xia, D. M., Xiang, S. T., Xiao, Q., Xing, Z. Z., Xu, G., Xu, J., Xu, J. L., Xu, W., Xu, Y., Xue, T., Yang, C. G., Yang, L., Ye, M., Yeh, M., Yeh, Y. S., Yip, K., Young, B. L., Yu, Z. Y., Zhan, L., Zhang, C., Zhang, F. H., Zhang, J. W., Zhang, Q. M., Zhang, K., Zhang, Q. X., Zhang, S. H., Zhang, Y. C., Zhang, Y. H. Percival, Zhang, Y. X., Zhang, Z. J., Zhang, Z. P., Zhang, Z. Y., Zhao, J., Zhao, Q. W., Zhao, Y. B., Zheng, L., Zhong, W. L., Zhou, L., Zhou, Z. Y., Zhuang, H. L., Zou, J. H., Center for Neutrino Physics, Physics, An, F. P., Bai, J. Z., Balantekin, A. B., Band, H. R., Beavis, D., Beriguete, W., Bishai, M., Blyth, S., Boddy, K., Brown, R. L., Cai, B., Cao, G. F., Cao, J., Carr, Rachel E., Chan, W. T., Chang, J. F., Chang, Y., Chasman, C., Chen, H. S., Chen, H. Y., Chen, S. J., Chen, S. M., Chen, X. C., Chen, X. H., Chen, X. S., Chen, Y., Chen, Y. X., Cherwinka, J. J., Chu, M. C., Cummings, J. P., Deng, Z. Y., Ding, Y. Y., Diwan, M. V., Dong, L., Draeger, E., Du, X. F., Dwyer, D. A., Edwards, W. R., Ely, S. R., Fang, S. D., Fu, J. Y., Fu, Z. W., Ge, L. Q., Ghazikhanian, V., Gill, R. L., Goett, J., Gonchar, M., Gong, G. H., Gong, H., Gornushkin, Y. A., Greenler, L. S., Gu, W. Q., Guan, M. Y., Guo, X. H., Hackenburg, R. W., Hahn, R. L., Hans, S., He, M., He, Q., He, W. S., Heeger, K. M., Heng, Y. K., Hinrichs, P., Ho, T. H., Hor, Y. K., Hsiung, Y. B., Hu, B. Z., Hu, T., Huang, H. X., Huang, H. Z., Huang, P. W., Huang, X., Huang, X. T., Huber, Patrick, Isvan, Z., Jaffe, D. E., Jetter, S., Ji, X. L., Ji, X. P., Jiang, H. J., Jiang, W. Q., Jiao, J. B., Johnson, R. A., Kang, L., Kettell, S. H., Kramer, M., Kwan, K. K., Kwok, M. W., Kwok, T., Lai, C. Y., Lai, W. C., Lai, W. H., Lau, K., Lebanowski, L., Lee, J., Lee, M. K. P., Leitner, R., Leung, J. K. C., Leung, K. Y., Lewis, C. A., Li, B., Li, F., Li, G. S., Li, J., Li, Q. J., Li, S. F., Li, W. D., Li, X. B., Li, X. N., Li, X. Q., Li, Y., Li, Z. B., Liang, H., Liang, J., Lin, C. J., Lin, G. L., Lin, S. K., Lin, S. X., Lin, Y. C., Ling, J. J., Link, Jonathan M., Littenberg, L., Littlejohn, B. R., Liu, B. J., Liu, C., Liu, D. W., Liu, H., Liu, J. C., Liu, J. L., Liu, S., Liu, X., Liu, Y. B., Lu, C., Lu, H. Q., Luk, A., Luk, K. B., Luo, T., Luo, X. L., Ma, L. H., Ma, Q. M., Ma, X. B., Ma, X. Y., Ma, Y. Q., Mayes, B., McDonald, K. T., McFarlane, M. C., McKeown, R. D., Meng, Y., Mohapatra, D., Morgan, J. E., Nakajima, Y., Napolitano, J., Naumov, D., Nemchenok, I., Newsom, C., Ngai, H. Y., Ngai, W. K., Nie, Y. B., Ning, Z., Ochoa-Ricoux, J. P., Oh, D., Olshevski, A., Pagac, A., Patton, S., Pearson, C., Pec, V., Peng, J. C., Piilonen, Leo E., Pinsky, L., Pun, C. S. J., Qi, F. Z., Qi, M., Qian, X., Raper, N., Rosero, R., Roskovec, B., Ruan, X. C., Seilhan, B., Shao, B. B., Shih, K., Steiner, H., Stoler, P., Sun, G. X., Sun, J. L., Tam, Y. H., Tanaka, H. K., Tang, X., Themann, H., Torun, Y., Trentalange, S., Tsai, O., Tsang, K. V., Tsang, R. H. M., Tull, C., Viren, B., Virostek, S., Vorobel, V., Wang, C. H., Wang, L. S., Wang, L. Y., Wang, L. Z., Wang, M., Wang, N. Y., Wang, R. G., Wang, T., Wang, W., Wang, X., Wang, Y. F., Wang, Z., Wang, Z. M., Webber, D. M., Wei, Y. D., Wen, L. J., Wenman, D. L., Whisnant, K., White, C. G., Whitehead, L., Whitten, C. A., Wilhelmi, J., Wise, T., Wong, H. C., Wong, H. L. H., Wong, J., Worcester, E., Wu, F. F., Wu, Q., Xia, D. M., Xiang, S. T., Xiao, Q., Xing, Z. Z., Xu, G., Xu, J., Xu, J. L., Xu, W., Xu, Y., Xue, T., Yang, C. G., Yang, L., Ye, M., Yeh, M., Yeh, Y. S., Yip, K., Young, B. L., Yu, Z. Y., Zhan, L., Zhang, C., Zhang, F. H., Zhang, J. W., Zhang, Q. M., Zhang, K., Zhang, Q. X., Zhang, S. H., Zhang, Y. C., Zhang, Y. H. Percival, Zhang, Y. X., Zhang, Z. J., Zhang, Z. P., Zhang, Z. Y., Zhao, J., Zhao, Q. W., Zhao, Y. B., Zheng, L., Zhong, W. L., Zhou, L., Zhou, Z. Y., Zhuang, H. L., and Zou, J. H.

Abstract

The Daya Bay Reactor Neutrino Experiment has measured a nonzero value for the neutrino mixing angle 0(13) with a significance of 5.2 standard deviations. Antineutrinos from six 2.9 GW(th) reactors were detected in six antineutrino detectors deployed in two near (flux-weighted baseline 470 m and 576 m) and one far (1648 m) underground experimental halls. With a 43 000 ton-GW(th)-day live-time exposure in 55 days, 10 416 (80 376) electron-antineutrino candidates were detected at the far hall (near halls). The ratio of the observed to expected number of antineutrinos at the far hall is R = 0.940 +/- 0.011(stat.) +/- 0.004(syst.). A rate-only analysis finds sin(2)2 theta(13) = 0.092 +/- 0.016(stat.) +/- 0.005(syst.) in a three-neutrino framework.

Published
2012

16. The Role of Systems Thinking in Systems Engineering, Design and Management.

Author

Chan, W. T.

Subjects
*SYSTEMS theory, *SYSTEMS engineering, *ENGINEERING design, *CIVIL engineering, *SERVICE life
Abstract

Systems thinking is a widely recognized and subscribed-to concept. Many benefits are ascribed to systems thinking and its result - the holistic solution. Yet, there is a wide range of opinion as to what systems thinking really is, and how its benefits can be realized in engineering practice. In fact, the concept of what constitutes a „system? is wide and variable. The purpose of the paper is to draw together diverse perspectives of systems thinking useful in engineering, and to present a set of core concepts that are useful in the successful design and operation of engineered systems. These concepts will be illustrated with examples drawn from the author?s experience in teaching and research on engineered systems. [ABSTRACT FROM AUTHOR]

Published
2015
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19. The structures and stabilities of singlet and triplet dithiatriazines: a computational study

Author

Hoffmeyer, R. E., Chan, W.-T., Goddard, J. D., and Oakley, R. T.

Abstract

Abinitiomolecular orbital and Møller–Plesset perturbation theory calculations have been carried out on two model dithiatriazines RCN3S2(R = H, NH2). With geometry optimization and the inclusion of electron correlation both of these dithiatriazines are predicted to be ground state singlets. Both molecules have low-lying triplet excited states, with energy gaps of 6.6 (R = H) and 13.0 (R = NH2) kcal mol−1. The singlet dithiatriazines distort from high (C2v) to low (Cs) symmetry, and these changes are important in determining the relative energies of the singlet and triplet molecules. The structural distortions experienced by these molecules are related to Hartree–Fock and Jahn–Teller instabilities in other thiazene heterocycles.

Published
1988
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26. Salinity-dependent toxicities of zinc oxide nanoparticles to the marine diatom Thalassiosira pseudonana.

Author

Yung MM, Wong SW, Kwok KW, Liu FZ, Leung YH, Chan WT, Li XY, Djurišić AB, and Leung KM

Subjects
Diatoms drug effects, Nanoparticles toxicity, Salinity, Water Pollutants, Chemical toxicity, Zinc Oxide toxicity
Abstract

This study comprehensively investigated the influences of salinity, exposure concentration and time on the aggregate size, surface charge and dissolution of zinc oxide nanoparticles (ZnO-NPs; 20nm) in seawater, and examined the interacting effect of salinity and waterborne exposure of ZnO-NPs on the marine diatom Thalassiosira pseudonana for 96h. We found that aggregate sizes of ZnO-NPs significantly increased with increasing salinity, but generally decreased with increasing exposure concentration. Ion release decreased with increasing salinity, whereas the surface charge of the particles was not affected by salinity. The increased aggregate size and decreased ion release with increasing salinity, and consequently lower concentration of bioavailable zinc ions, resulted in decreased toxicity of ZnO-NPs at higher salinity in general in terms of growth inhibition (IC50) and chlorophyll fluorescence (EC50 - ФPo and EC50 - Ф2). However, IC50s and EC50s of ZnO-NPs were smaller than those of Zn(2+) (from ZnO-NPs ultrafiltrate and ZnCl2), indicating that dissolved Zn(2+) can only partially explain the toxicity of ZnO-NPs. SEM images showed that ZnO-NPs attached on the diatom frustule surface, suggesting that the interaction between the nanoparticles and the cell surface may acerbate the toxicity of ZnO-NPs. Our results linked the physicochemical characteristics of ZnO-NPs in seawater with their toxicities to the marine diatom and highlighted the importance of salinity as an influential environmental factor governing the aggregation, dissolution and the toxicity of ZnO-NPs., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Published
2015
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27. Mad honey poisoning mimicking acute myocardial infarction.

Author

Chen SP, Lam YH, Ng VC, Lau FL, Sze YC, Chan WT, and Mak TW

Subjects
Abdominal Pain etiology, Atropine therapeutic use, Chest Pain etiology, Electrocardiography, Humans, Male, Middle Aged, Diterpenes urine, Honey poisoning, Myocardial Infarction diagnosis
Abstract

We report a case of acute poisoning in a 48-year-old man who presented with chest pain, abdominal pain, dizziness, sweatiness, blurred vision, and severe hypotension after ingestion of honey. His electrocardiogram showed sinus bradycardia and transient ST elevation. He made a good recovery after treatment with atropine and close monitoring. Grayanotoxin was detected in his urine and the honey he ingested, which confirmed a diagnosis of mad honey poisoning. This is a condition prevalent in the Black Sea region around Turkey but rarely seen locally. Although mad honey poisoning is life-threatening, early use of atropine is life-saving. Such poisoning may present with ST elevation in the electrocardiogram and symptoms mimicking acute myocardial infarction. It is therefore essential for clinicians to recognise this unusual form of poisoning and avoid the disastrous use of thrombolytic therapy.

Published
2013
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28. Outbreak of hypoglycaemia: sexual enhancement products containing oral hypoglycaemic agent.

Author

Poon WT, Lam YH, Lee HH, Ching CK, Chan WT, Chan SS, Lai CK, Tse ML, Chan AY, and Mak TW

Subjects
Administration, Oral, Adult, Aged, Aged, 80 and over, Drug Combinations, Glyburide administration & dosage, Hong Kong, Humans, Hypoglycemia chemically induced, Hypoglycemic Agents administration & dosage, Male, Middle Aged, Piperazines administration & dosage, Purines administration & dosage, Purines adverse effects, Retrospective Studies, Sildenafil Citrate, Sulfones administration & dosage, Vasodilator Agents administration & dosage, Disease Outbreaks statistics & numerical data, Glyburide adverse effects, Hypoglycemia epidemiology, Hypoglycemic Agents adverse effects, Piperazines adverse effects, Sexual Behavior, Sulfones adverse effects, Vasodilator Agents adverse effects
Abstract

Objectives: To describe a cluster of Hong Kong subjects with hypoglycaemia, after they had taken various non-prescription sildenafil products containing glibenclamide., Design: Retrospective study., Setting: A tertiary referral centre for clinical toxicology analysis in Hong Kong., Patients: All men referred to the laboratory for investigation of suspected drug-induced hypoglycaemia from December 2007 to September 2008., Main Outcome Measures: The characteristics of these patients, including their clinical presentations, outcomes, drug history, urine toxicology analysis results, and in some instances, analysis results of unused products., Results: A total of 144 male patients were referred for suspected drug-induced hypoglycaemia. Sildenafil and glibenclamide, or their metabolites, were detected in the urine specimens of 68 (47%) patients, none of whom had been prescribed either drug by a registered medical practitioner. Among these subjects, 24 (35%) denied any use of sexual enhancement products despite repeated questioning. Eight patients had repeated exposure resulting in re-admission. The sources of these sexual enhancement products included pharmacies in Mainland China, friends, local pharmacies, peddlers, or were unknown. Three patients died, one remains in a vegetative state and one suffered cognitive impairment; the remaining 63 recovered fully. Twenty-five unused sexual enhancement products of seven different kinds were recovered for analysis. The median (range) of sildenafil and glibenclamide per unit dose was 64 (0.05-198) mg and 70 (0-158) mg, respectively., Conclusion: These illegal products pose a severe and continued threat to society and therefore deserve widespread vigilance, so that such products can be eradicated at their source.

Published
2009

29. Persistence of Mycobacterium tuberculosis in macrophages and mice requires the glyoxylate shunt enzyme isocitrate lyase.

Author

McKinney JD, Höner zu Bentrup K, Muñoz-Elías EJ, Miczak A, Chen B, Chan WT, Swenson D, Sacchettini JC, Jacobs WR Jr, and Russell DG

Subjects
Animals, Fatty Acids metabolism, Isocitrate Lyase genetics, Lung microbiology, Macrophage Activation, Macrophages immunology, Mice, Mice, Inbred BALB C, Mice, Inbred C57BL, Mice, Knockout, Mutagenesis, Mycobacterium tuberculosis enzymology, Mycobacterium tuberculosis immunology, Mycobacterium tuberculosis pathogenicity, Recombinant Fusion Proteins genetics, Recombinant Fusion Proteins metabolism, Tuberculosis enzymology, Tuberculosis immunology, Virulence genetics, Bacterial Proteins, Isocitrate Lyase physiology, Macrophages microbiology, Mycobacterium tuberculosis physiology, Tuberculosis microbiology
Abstract

Mycobacterium tuberculosis claims more human lives each year than any other bacterial pathogen. Infection is maintained in spite of acquired immunity and resists eradication by antimicrobials. Despite an urgent need for new therapies targeting persistent bacteria, our knowledge of bacterial metabolism throughout the course of infection remains rudimentary. Here we report that persistence of M. tuberculosis in mice is facilitated by isocitrate lyase (ICL), an enzyme essential for the metabolism of fatty acids. Disruption of the icl gene attenuated bacterial persistence and virulence in immune-competent mice without affecting bacterial growth during the acute phase of infection. A link between the requirement for ICL and the immune status of the host was established by the restored virulence of delta icl bacteria in interferon-gamma knockout mice. This link was apparent at the level of the infected macrophage: Activation of infected macrophages increased expression of ICL, and the delta icl mutant was markedly attenuated for survival in activated but not resting macrophages. These data suggest that the metabolism of M. tuberculosis in vivo is profoundly influenced by the host response to infection, an observation with important implications for the treatment of chronic tuberculosis.

Published
2000
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