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The work described in this thesis is a study of imperfections in high purity, low dislocation content synthetic quartz single crystals which are grown on a commercial scale by the General Electric Company. Hydrogen and metal ion impurities in quartz were studied using low temperature transmission Fourier Transform Infrared Spectroscopy, (FTIR). Incorporation of impurities in quartz was investigated using crystals which were doped with Al, Fe, Cr, Co, Ti, P, Cu and K. Orientation of hydroxyl impurities was determined using polarised infrared spectroscopy. Deuterated quartz crystals were grown and studied as analogues to high purity crystals. X-ray diffraction topography was used to evaluate crystal quality and to perform a study of quartz which had been treated by electrodiffusion, or sweeping. Crystal lattice strain and sweeping damage was studied using double crystal topography at the Synchrotron Radiation Source, (SRS), at the Daresbury Laboratory. Metal ion impurities were sh own to incorporate interstitially into quartz crystals. The only exceptions were aluminium and iron, which incorporated substitutionally. All the impurities studied introduced hydrogen impurities such as hydroxyl ions and water molecules into quartz. A relationship between impurity concentration and hydrogen content was clearly indicated. The 3200 cm-1 broad absorption band characteristic of impure and fast grown synthetic quartz was strongly implicated as being due to interstitially incorporated water molecules. The major hydrogen impurities in quartz were sodium hydroxide molecules which were preferentially aligned along the X, Y and Z growth axes. Hydroxyl ions were not incorporated directly from the growth solution. Sweeping was shown to induce the formation of a negative space charge in treated quartz which gave rise to inhomogeneous lattice strain. The strain was gradually relieved upon prolonged exposure to x-rays. A mechanism for the production and relief of lattice strain has been proposed. Sweeping produced surface damage on mechanically polished crystals but not on those treated by chemical polishing using hydrofluoric acid. No further detrimental effects of sweeping were observed. Double crystal topographic studies revealed two possible bulk defects in Quartz. The first of these was a previously unreported planar defect parallel to the X-Y plane of quartz. The second was possibly a planar defect associated with the cellular growth cells in the (00.1) growth sector of quartz. The validity of these observations was put in doubt by the possibility of defect projection from the silicon monochromator which had been used in double crystal studies.

Congenital Heart Defects (CHDs), structural heart defects that are present at birth, are prevalent in approximately 1% of live births. While, historically, the presence of such defects was associated with a heightened risk of mortality, advances in medicine have allowed nearly 85% of individuals with CHDs to live into adulthood. As such, many of these individuals are reaching reproductive age and are becoming pregnant. In order to understand the implications of pregnancy among women with CHDs, a literature review was undertaken in order to elucidate the conditions that may present to the mother, as a product of the underlying defect, as well as to discern the impact of a maternal CHD on the child. Pregnancy induces hemodynamic alterations, such as an increase in stroke volume and heart rate (and thus cardiac output), and brings about an increase in blood volume. In populations with CHD, these hemodynamic changes may induce particular risks to the mother, as her cardiac condition may obstruct her ability to cope to with the heightened stress on the heart. Moreover, given that the heart may not function in an ideal manner, a less than ideal environment is present in-utero. Women with CHD suffer from elevated cardiovascular and obstetric complications, with the risk of some cardiovascular events extending into the post-partum period. During pregnancy, approximately 11% of women with CHD will experience a cardiovascular complication; this risk is highest among those with complex forms of the defect. Arrhythmia, specifically, is the most common complication, and will occur in 4.5% of pregnancies. Heart failure is also frequent, occurring in 4% to 5% of pregnancies, with the highest risk presenting in those patients with Eisenmenger syndrome and those with cyanotic forms of CHD. Pulmonary edema and thrombolytic events are also present in this population with a higher prevalence than in a healthy pregnant population. In the 6-month period after delivery, 12% of women with CHD will experience a cardiac event, with arrhythmia and heart failure as the most common complications. Obstetric complications occur in approximately 5% of pregnancies among women with CHDs, with 11% experiencing premature labor, 8.4% experiencing post-partum hemorrhage and 5.5% experiencing pregnancy-induced hypertension. Miscarriage occurs in 15% of pregnancies, with a dose-response type relationship associated with the severity of the underlying defect, as miscarriage occurs in up to 66% of pregnancies in those with Fontan palliation. Premature rupture of membranes occurs in 3.5% of pregnancies, with half of these cases occurring to patients with transposition of the great arteries. Termination of pregnancy also occurs in 5% to 8% of pregnancies, given high risk of complications to both mother and fetus. While preeclampsia is expected to occur in approximately 2-3% of pregnancies, this risk does not exceed what occurs in a healthy population. With regard to the impact of maternal CHD on the fetus, events occurring to the fetus/neonate include preterm delivery, small for gestational age, respiratory distress syndrome, intraventricular hemorrhage, and neonatal death. Between 1.5% and 2% of pregnancies will terminate in fetal mortality. Premature birth is likely in 12% to 20% births, with of 8% of neonates born as small for gestational age. Moreover, 3.5% of children born to mothers with CHD will present with CHD, themselves. Long-term effects of maternal CHD are not well-described. Despite these complications, pregnancy among women with CHD is well-tolerated and only in very few cases of those presenting with severe defects, is pregnancy counter-indicated. However, in order to mitigate risks, pre-pregnancy counseling is recommended in all women with CHD, regardless of severity of the defect. Counseling should include an overview of the form of defect, any surgical or medicinal interventions undertaken in response to the defect, an echocardiography, an exercise stress test, among other evaluations. Monitoring of the pregnancy should continue throughout gestation and delivery should occur in a specialized care facility and the mother and fetus should be monitored by a consortium of cardiologists, obstetricians, anesthesiologists, midwives. Monitoring of the mother should extend into the post-partum period until any cardiovascular or hemodynamic pregnancy-related alterations have returned to normal.