Homozygous α0-thalassemia is a serious autosomal recessive disorder with poor fetal outcome and severe maternal complications. Conventionally, prenatal diagnosis is performed by an invasive test. A non-invasive approach using serial ultrasonography can effectively reduce the need for invasive tests in unaffected pregnancies. For two-dimensional ultrasound prediction, a total of 777 at-risk fetuses were studied from 12 to 20 weeks between 1995 and 2006. At 12–15 weeks’ gestation, the highest sensitivity (98.3%) was achieved by the combination of fetal cardiothoracic ratio (CTR) and/or middle cerebral artery peak systolic velocity (MCA-PSV) at a false-positive rate of 15.8%. At 16–20 weeks’ gestation, the sensitivity of CTR was 100.0%, but the false-positive rate was 5.2%. In contrast, the false-positive rate of MCA-PSV alone was 1.4% and that of the combination of CTR and MCA-PSV was 0%, although their sensitivities were less than 65%. In a cross-sectional retrospective study of 546 samples at-risk and control (268 fetal and 278 neonatal cord blood), the degree of anemia was only mild in 27.5% of the affected fetuses (see chapter 3 for definition of mild anemia). Because MCA-PSV is not very predictive of mild anemia, this may be one of the reasons why MCA-PSV is not very sensitive in predicting an affected pregnancy. A total of 832 at-risk pregnancies were studied using same noninvasive approach at Maternal and Neonatal Hospital of Guangzhou (MNH) and Tsan Yuk Hospital (TYH). The overall sensitivity and specificity of the noninvasive approach was 100% and 95.6% respectively. At MNH, the need for an invasive test was reduced by 78.6%, and all the affected pregnancies were diagnosed before 24 weeks’ gestation. After adequate training and monitoring the quality of the subsequent ultrasound examinations, the results achieved at MNH were comparable to TYH, with at-risk pregnancies including the affected ones being seen at a more advanced gestation at MNH. In a retrospective review of 361 women at risk of carrying an affected fetus, 311 (86.2%) opted for the non-invasive approach using CTR and/or placenta. The cost saving of this non-invasive approach was relatively small (HK$ 2,651) in comparison to the cost of the whole prenatal screening program. On the other hand, the non-invasive approach was more expensive than the direct invasive approach for low MCV couples, as well as couples discordant for α-thalassemia and β-thalassemia. ages. These results support the adoption of non-invasive approach in which routine invasive test or karyotyping is no longer performed. A total of 106 at-risk pregnancies and normal controls were prospectively studied using three-dimensional ultrasonography. Placental volume (PV) at 11-14 weeks, and PV/CRL quotient at 9-14 weeks’ gestation of affected pregnancies were significantly greater than unaffected pregnancies (P<0.05). Using a cut-off point of 1.2ml/mm for PV/CRL quotient to predict an affected pregnancy, the sensitivity, and specificity was 96.2%, and 100.0% respectively. / published_or_final_version / Obstetrics and Gynaecology / Master / Doctor of Medicine

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A novel segmented electrodes linear ultrasonic motor (USM) was developed. Using a planar vibration mode concept to achieve elliptical motion at the USM drive-tip, an attempt to decouple the components of the drive-tip trajectory was made. The proposed design allows greater control of the drive-tip trajectory without altering the excitation voltage. Finite element analyses were conducted on the proposed design to estimate the performance of the USM. The maximum thrust force and speed are estimated to be 46N and 0.5370m/s, respectively. During experimental investigation, the maximum thrust force and speed observed were 36N and 0.223m/s, respectively, at a preload of 70N. Furthermore, the smallest step achievable was 9nm with an 18μs impulse. Nevertheless, the proposed design allowed the speed of the USM to vary while keeping the thrust force relatively constant and allowed the USM to achieve high resolution without a major sacrifice of thrust force.

A novel segmented electrodes linear ultrasonic motor (USM) was developed. Using a planar vibration mode concept to achieve elliptical motion at the USM drive-tip, an attempt to decouple the components of the drive-tip trajectory was made. The proposed design allows greater control of the drive-tip trajectory without altering the excitation voltage. Finite element analyses were conducted on the proposed design to estimate the performance of the USM. The maximum thrust force and speed are estimated to be 46N and 0.5370m/s, respectively. During experimental investigation, the maximum thrust force and speed observed were 36N and 0.223m/s, respectively, at a preload of 70N. Furthermore, the smallest step achievable was 9nm with an 18μs impulse. Nevertheless, the proposed design allowed the speed of the USM to vary while keeping the thrust force relatively constant and allowed the USM to achieve high resolution without a major sacrifice of thrust force.

Dissertation (MHSc--Health Science) -- Auckland University of Technology, 2003. / Also held in print (137 leaves ; 30 cm.) in North Shore Campus Theses Collection (T 616.07543 JEF)

Thesis (M. Sc.)--Victoria University (Melbourne, Vic.), 2006. / Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 1987.

Thesis (M.S.)--University of Michigan, 1987.

Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Laurence J. Jacobs; Committee Member: Jianmin Qu; Committee Member: Jin-Yeon Kim. Part of the SMARTech Electronic Thesis and Dissertation Collection.