Microstructural Effects on Irradiation Creep of Reactor Core Materials.

The processes that control irradiation creep are dependent on the temperature and the rate of production of freely migrating point defects, affecting both the microstructure and the mechanisms of mass transport. Because of the experimental difficulties in studying irradiation creep, many different hypothetical models have been developed that either favour a dislocation slip or a mass transport mechanism. Irradiation creep mechanisms and models that are dependent on the microstructure, which are either fully or partially mechanistic in nature, are described and discussed in terms of their ability to account for the in-reactor creep behaviour of various nuclear reactor core materials. A rate theory model for creep of Zr-2.5Nb pressure tubing in CANDU reactors incorporating the as-fabricated microstructure has been developed that gives good agreement with measurements for tubes manufactured by different fabrication routes having very different microstructures. One can therefore conclude that for Zr-alloys at temperatures < 300 °C and stresses < 150 MPa, diffusional mass transport is the dominant creep mechanism. The most important microstructural parameter controlling irradiation creep for these conditions is the grain structure. Austenitic alloys follow similar microstructural dependencies as Zr-alloys, but up to higher temperature and stress ranges. The exception is that dislocation slip is dominant in austenitic alloys at temperatures < 100 °C because there are few barriers to dislocation slip at these low temperatures, which is linked to the enhanced recombination of irradiation-induced point defects.

Disparities in the timing of antenatal care initiation and associated factors in an ethnically dense maternal cohort with high levels of area deprivation.

BACKGROUND: Late access to antenatal care is a contributor to excess mortality and morbidity among ethnic minority mothers compared to White British in the UK. While individual ethnicity and socioeconomic disadvantage are linked to late antenatal care initiation, studies have seldom explored patterns of late initiation and associated factors in ethnically dense socially disadvantaged settings. This study investigated disparities in the timing of antenatal care initiation, and associated factors in an ethnically dense socially disadvantaged maternal cohort. METHODS: A retrospective cross-sectional study using routinely collected anonymous data on all births between April 2007-March 2016 in Luton and Dunstable hospital, UK (N = 46,307). Late initiation was defined as first antenatal appointment attended at > 12 weeks of gestation and further classified into moderately late (13-19 weeks) and extremely late initiation (≥ 20 weeks). We applied logistic and multinomial models to examine associations of late initiation with maternal and sociodemographic factors. RESULTS: Overall, one fifth of mothers (20.8%) started antenatal care at > 12 weeks of gestation. Prevalence of late initiation varied across ethnic groups, from 16.3% (White British) to 34.2% (Black African). Late initiation was strongly associated with non-White British ethnicity. Compared to White British mothers, the odds of late initiation and relative risk of extremely late initiation were highest for Black African mothers [adjusted OR = 3.37 (3.05, 3.73) for late initiation and RRR = 4.03 (3.51, 4.64) for extremely late initiation]. The odds did not increase with increasing area deprivation, but the relative risk of moderately late initiation increased in the most deprived ([RRR = 1.53 (1.37, 1.72)] and second most deprived areas [RRR = 1.23 (1.10, 1.38)]. Late initiation was associated with younger mothers and to a lesser extent, older mothers aged > 35 years. Mothers who smoked during pregnancy were at higher odds of late initiation compared to mothers who did not smoke. CONCLUSIONS: There is a need to intensify universal and targeted programmes/services to support mothers in ethnically dense socially disadvantaged areas to start antenatal care on time. Local variations in ethnic diversity and levels of social disadvantage are essential aspects to consider while planning services and programmes to ensure equity in maternity care provision.

Effect of Neutron Irradiation on the Mechanical Properties, Swelling and Creep of Austenitic Stainless Steels.

Austenitic stainless steels are used for core internal structures in sodium-cooled fast reactors (SFRs) and light-water reactors (LWRs) because of their high strength and retained toughness after irradiation (up to 80 dpa in LWRs), unlike ferritic steels that are embrittled at low doses (<1 dpa). For fast reactors, operating temperatures vary from 400 to 550 °C for the internal structures and up to 650 °C for the fuel cladding. The internal structures of the LWRs operate at temperatures between approximately 270 and 320 °C although some parts can be hotter (more than 400 °C) because of localised nuclear heating. The ongoing operability relies on being able to understand and predict how the mechanical properties and dimensional stability change over extended periods of operation. Test reactor irradiations and power reactor operating experience over more than 50 years has resulted in the accumulation of a large amount of data from which one can assess the effects of irradiation on the properties of austenitic stainless steels. The effect of irradiation on the intrinsic mechanical properties (strength, ductility, toughness, etc.) and dimensional stability derived from in- and out-reactor (post-irradiation) measurements and tests will be described and discussed. The main observations will be assessed using radiation damage and gas production models. Rate theory models will be used to show how the microstructural changes during irradiation affect mechanical properties and dimensional stability.

Analysis of routinely collected data: Determining associations of maternal risk factors and infant outcomes with gestational diabetes, in Pakistani, Indian, Bangladeshi and white British pregnant women in Luton, England.

OBJECTIVE: This study aims to compare the prevalence of gestational diabetes in Indian, Pakistani, Bangladeshi and British women in Luton, England and further examine associations in maternal risk factors (age BMI, smoking status and birth outcome), with gestational diabetes, with maternal ethnicity. DESIGN: A retrospective analysis using routinely collected secondary data from Ciconia Maternity information System (CMiS), between 2008 and 2013. The ethnicity of women recorded as Indian, Pakistani, Bangladeshi and white British, residing in [removed] were included in the study. The outcomes for n=15,211 cases were analysed using adjusted standardised residuals, Pearson Chi-square, frequencies and percentages of women with gestational diabetes. RESULTS: The prevalence of gestational diabetes was significantly higher in the sample of Bangladeshi (2.1%) and Pakistani (1.4%) compared to Indian (1%) and white British (0.4%) women. Of the women diagnosed with gestational diabetes, 48.7% of the women diagnosed with gestational diabetes in this cohort were Pakistani, compared with 28.3% of Bangladeshi, 6.6% of Indian and 16.4% of white British (χ2= 84.57 df=6, p<0.001). A number of significant Pearson Chi-square associations were found between Pakistani women diagnosed with gestational diabetes and BMI over 30kg/m2 (χ2= 43.1 df=4, p<0.001) and an early gestational age at delivery (24-37 weeks) (χ2= 4.084 df=1, p=0.043). CONCLUSIONS: There are important differences in the prevalence rates of gestational diabetes which varied by maternal ethnicity. Of the women who had GDM, 48.7% were Pakistani, compared with 28.3% Bangladeshi, 16.4% white British and 6.6% Indian. It is essential policy makers and service providers target GDM screening and associated interventions and future research seeks to understand the reasons behind these differences.

A qualitative study exploring the experiences of bereavement after stillbirth in pakistani, bangladeshi and white british mothers living in luton, UK.

AIM: This study aims to explore the experiences of bereavement after stillbirth of Pakistani, Bangladeshi and White British mothers in a town with multi-ethnic populations in England. PARTICIPANTS: A purposive sample of Pakistani, Bangladeshi and White British mothers aged over 16 (at time of infant birth), who suffered a stillbirth in the preceding 6-24 months and residing in a specified postcode area were invited to take part in the study, by an identified gatekeeper (audit midwife) from the local National Health Service Trust, in addition to local bereavement charities. DESIGN: Qualitative methods using face-to-face semi-structured interviews were undertaken, recorded and transcribed verbatim. Using framework analysis, several themes were identified. FINDINGS: There were three main themes identified from the data; 1. knowledge and information of pregnancy and perinatal mortality; 2. attitudes and perceptions to pregnancy and perinatal mortality and 3. experiences with maternity care. The findings revealed mostly similarities in the bereavement experiences of the Pakistani, Bangladeshi and White British mothers. A few cultural and religious differences were identified. CONCLUSIONS: This study found important similarities in bereavement experiences of Pakistani, Bangladeshi and White British mothers and highlights considerations for policy makers and maternity services in how the timing of bereavement after care is provided, including advice surrounding the infant post-mortem. 209.

Ethnic differences in risk factors for adverse birth outcomes between Pakistani, Bangladeshi, and White British mothers.

AIM: Reducing poor maternal and infant outcomes in pregnancy is the aim of maternity care. Adverse health behaviours lead to increased risk and can adversely mediate birth outcomes. This study examines whether risk factors are similar, different, or clustered according to maternal ethnicity. DESIGN: Retrospective analysis of routinely collected data (2008-2013). METHODS: We analysed data routinely collected data from a local University Hospital Ciconia Maternity information System (CMiS), for White British, Pakistani, and Bangladeshi women (N = 15,211) using cross-tabulations, ANCOVA, adjusted standardized residuals (ASR), and Pearson's chi-squared statistics. RESULTS: The results demonstrate distinct clusters of risk factors between White British, Pakistani, and Bangladeshi mothers. Additionally, Pakistani mothers had the highest number of statistically significant risk factors, according to maternal ethnicity, showing that 49% of women in this cohort that were diagnosed with diabetes were Pakistani, 21.5% of White British women smoked and results showed that Bangladeshi mothers delivered the lightest weight infants (adjusted mean: 3,055.4 g). CONCLUSIONS: This study showed differences in the risk factors between White British, Pakistani, and Bangladeshi mothers. The identified risk factors were clustered by maternal ethnicity. IMPACT: Identification of these risk factor clusters can help policymakers and clinicians direct resources and may help reduce ethnic variation found in these populations that might be attributed to adverse health behaviours and increased risk factors.

Understanding the consumption of folic acid during preconception, among Pakistani, Bangladeshi and white British mothers in Luton, UK: a qualitative study.

BACKGROUND: To review the similarities and differences in Pakistani, Bangladeshi and White British mothers health beliefs (attitudes, knowledge and perceptions) and health behaviour regarding their consumption of folic acid pre-conception, to reduce the risk of neural tube defects. METHODS: Our study used a descriptive qualitative research approach, implementing face-to-face focus group discussions with Pakistani, Bangladeshi or White British mothers (normal birth outcomes and mothers with poor birth outcomes) and semi-structured interviews or focus groups with service providers using semi-structured topic guides. This method is well suited for under researched areas where in-depth information is sought. There were three sample groups: 1. Pakistani, Bangladeshi and White British mothers with normal birth outcomes (delivery after 37 weeks of gestation, in the preceding 6 to 24 months, weighing 2500 g and living within a specified postcode area in Luton, UK). 2. Pakistani Bangladeshi and white British bereaved mothers who had suffered a perinatal mortality (preceding 6 to 24 months, residing within a specificied postcode area). 3. Healthcare professionals working on the local maternity care pathway (i.e. services providing preconception, antenatal, antepartum and postpartum care). Transcribed discussions were analysed using the Framework Analysis approach. RESULTS: The majority of mothers in this sample did not understand the benefits or optimal time to take folic acid pre-conception. Conversely, healthcare professionals believed the majority of women did consume folic acid, prior to conception. CONCLUSIONS: There is a need to increase public health awareness of the optimal time and subsequent benefits for taking folic acid, to prevent neural tube defects.

Differences in the pregnancy gestation period and mean birth weights in infants born to Indian, Pakistani, Bangladeshi and white British mothers in Luton, UK: a retrospective analysis of routinely collected data.

OBJECTIVE: To compare mean birth weights and gestational age at delivery of infants born to Indian, Pakistani, Bangladeshi and white British mothers in Luton, UK. DESIGN: Retrospective analysis using routinely recorded secondary data in Ciconia Maternity information System, between 2008 and 2013. SETTING: Luton, UK. PARTICIPANTS: Mothers whose ethnicity was recorded as white British, Bangladeshi, Pakistani or Indian and living in Luton, aged over 16, who had a live singleton birth over 24 weeks of gestation were included in the analysis (n=14 871). OUTCOME MEASURES: Primary outcome measures were mean birth weight and gestational age at delivery. RESULTS: After controlling for maternal age, smoking, diabetes, gestation age, parity and maternal height and body mass index at booking, a significant difference in infants' mean birth weight was found between white British and Indian, Pakistani and Bangladeshi infants, F(3, 12 287)=300.32, p<0.0001. The partial Eta-squared for maternal ethnicity was η2=0.067. The adjusted mean birth weight for white British infants was found to be 3377.89 g (95% CI 3365.34 to 3390.44); Indian infants, 3033.09 g (95% CI 3038.63 to 3103.55); Pakistani infants, 3129.49 g (95% CI 3114.5 to 3144.48); and Bangladeshi infants, 3064.21 g (95% CI 3041.36 to 3087.06). There was a significant association in preterm delivery found in primipara Indian mothers, compared with Indian mothers (Wald=8.192, df 1, p<0.005). CONCLUSIONS: Results show important differences in adjusted mean birth weight between Indian, Pakistani, Bangladeshi and white British women. Moreover, an association was found between primipara Indian mothers and preterm delivery, when compared with Pakistani, Bangladeshi and white British women.

A comparison of antenatal classifications of 'overweight' and 'obesity' prevalence between white British, Indian, Pakistani and Bangladeshi pregnant women in England; analysis of retrospective data.

BACKGROUND: Maternal obesity increases women's risk of poor birth outcomes, and statistics show that Pakistani and Bangladeshi women (who are born or settled) in the UK experience higher rates of perinatal mortality and congenital anomalies than white British or white Other women. This study compares the prevalence of maternal obesity in Indian, Pakistani, Bangladeshi and white British women using standard and Asian-specific BMI metrics. METHOD: Retrospective cross-sectional analysis using routinely recorded secondary data in Ciconia Maternity information System (CMiS), between 2008 and 2013. Mothers (n = 15,205) whose ethnicity was recorded as white British, Bangladeshi, Pakistani or Indian. Adjusted standardised residuals and Pearson Chi-square. MAIN OUTCOME MEASURES: Percentage of mothers stratified by ethnicity (Indian, Pakistani, Bangladeshi and white British) who are classified as overweight or obese using standard and revised World Health Organisation BMI thresholds. RESULTS: Compared to standard BMI thresholds, using the revised BMI threshold resulted in a higher prevalence of obesity: 22.8% of Indian and 24.3% of Bangladeshi and 32.3% of Pakistani women. Pearson Chi-square confirmed that significantly more Pakistani women were classified as 'obese' compared with white British, Indian or Bangladeshi women (χ 2  = 499,88 df = 9, p < 0.001). CONCLUSIONS: There are differences in the prevalence of obese and overweight women stratified by maternal ethnicity of white British, Indian, Pakistani and Bangladeshi. Using revised anthropometric measures in Indian, Pakistani and Bangladeshi women has clinical implications for identifying risks associated with obesity and increased complications in pregnancy.

Selected maternal morbidities in women with a prior caesarean delivery planning vaginal birth or elective repeat caesarean section: a retrospective cohort analysis using data from the UK Obstetric Surveillance System.

OBJECTIVE: To conduct a secondary analysis of data from the UK Obstetric Surveillance System (UKOSS) to estimate the rates of specific maternal risks associated with planned vaginal birth after caesarean (VBAC) and elective repeat caesarean section (ERCS). DESIGN: A retrospective cohort analysis using UKOSS data from 4 studies conducted between 2005 and 2012. SETTING: All hospitals with consultant-led maternity units in the UK. POPULATION: Pregnant women who had a previous caesarean section. METHOD: Women who had undergone a previous caesarean section were divided into 2 exposure groups: planned VBAC and ERCS. We calculated the incidence of each of the 4 outcomes of interest with 95% CIs for the 2 exposure groups using proxy denominators (total estimated VBAC and ERCS maternities in a given year). Incidences were compared between groups using χ(2) test or Fisher's exact test and risk ratios with 95% CI. MAIN OUTCOME MEASURES: Severe maternal morbidities: peripartum hysterectomy, severe sepsis, peripartum haemorrhage and failed tracheal intubation. RESULTS: The risks of all complications examined in both groups were low. The rates of peripartum hysterectomy, severe sepsis, peripartum haemorrhage and failed tracheal intubation were not significantly different between the 2 groups in absolute or relative terms. CONCLUSIONS: While the risk of uterine rupture in the VBAC and ERCS groups is well understood, this national study did not demonstrate any other clear differences in the outcomes we examined. The absolute and relative risks of maternal complications were small in both groups. Large epidemiological studies could further help to assess whether the incidence of these rare outcomes would significantly differ between the VBAC and ERCS groups if a larger number of cases were to be examined. In the interim, this study provides important information to help pregnant women in their decision-making process.

"Benign" hypergammaglobulinemic purpura is not benign in pregnancy.

A woman presented at 25 weeks gestation in her first pregnancy with severe preeclampsia and an intrauterine death. It later emerged that she had Waldenstrom's benign hypergammaglobulinemic purpura. We discuss the implications of this diagnosis in pregnancy and explore possible management options during subsequent pregnancies.