On the limitations of transmissibility functions for damage localisation: the influence of completeness

Transmissibility functions are used to identify and locate damage in critical structures for health monitoring purposes. Their appeal over conventional signal or frequency response-based functions lie in a unique property; sub-structural invariance. It has been shown that the transmissibility of an assembled structure, when obtained correctly, can describe the dynamics of a sub-structure in a manner that is independent from the remainder of the assembly. It is this sub-structural invariance that enables transmissibility functions to locate damage in complex structures. Though a valuable property, sub-structural invariance relies on the notion of a complete interface representation; the interface that separates the sub-structure from the remaining assembly must be sufficiently instrumented so that all important interface dynamics can be captured. In practice, without considerable experimental effort, complete interface representations are not achievable. Importantly, the transmissibilities obtained in the presence of an incomplete interface are unable to discern between damage located interior, or exterior, to a particular sub-structure; they are no longer invariant. Hence, their ability to locate damage is compromised. In the present paper we introduce the notion of completeness in the context of transmissibility-based structural health monitoring, and examine its importance for the accurate localisation of damage through numerical and experimental examples

Haptoglobin phenotype and abnormal uterine artery Doppler in a racially diverse cohort

The anti-oxidant and proangiogenic protein haptoglobin (Hp) is believed to be important for implantation and pregnancy, although its specific role is not known. The three phenotypes (1-1, 2-1 and 2-2) differ in structure and function. Hp 2-2 is associated with increased vascular stiffness in other populations. We examined whether Hp phenotype is associated with abnormal uterine artery Doppler (UAD) in pregnancy

Vitamin D status and recurrent preterm birth: a nested case-control study in high-risk women

OBJECTIVE: To determine whether vitamin D status is associated with recurrent preterm birth, and any interactions between vitamin D levels and fish consumption. DESIGN: A nested case-control study, using data from a randomised trial of omega-3 fatty acid supplementation to prevent recurrent preterm birth. SETTING: Fourteen academic health centres in the USA. POPULATION: Women with prior spontaneous preterm birth. METHODS: In 131 cases (preterm delivery at <35 weeks of gestation) and 134 term controls, we measured serum 25-hydroxyvitamin D [25(OH)D] concentrations by liquid chromatography-tandem mass spectrometry (LC-MS) from samples collected at baseline (16-22 weeks of gestation). Logistic regression models controlled for study centre, maternal age, race/ethnicity, number of prior preterm deliveries, smoking status, body mass index, and treatment. MAIN OUTCOME MEASURES: Recurrent preterm birth at <37 and <32 weeks of gestation. RESULTS: The median mid-gestation serum 25(OH)D concentration was 67 nmol/l, and 27% had concentrations of <50 nmol/l. Serum 25(OH)D concentration was not significantly associated with preterm birth (OR 1.33; 95% CI 0.48-3.70 for lowest versus highest quartiles). Likewise, comparing women with 25(OH)D concentrations of 50 nmol/l, or higher, with those with <50 nmol/l generated an odds ratio of 0.80 (95% CI 0.38-1.69). Contrary to our expectation, a negative correlation was observed between fish consumption and serum 25(OH)D concentration (-0.18, P < 0.01). CONCLUSIONS: In a cohort of women with a prior preterm birth, vitamin D status at mid-pregnancy was not associated with recurrent preterm birth