An experimental assessment of the effect of current on wave buoy measurements

This is the final version. Available on open access from Elsevier via the DOI in this recordWave measurement buoys provide characterisation of wave climates that forms the basis for the design of offshore systems. These buoys are commonly subjected to currents which affect the resulting wave measurements, and if not accounted for will result in errors in the estimated sea state parameters. The present work provides results and observations from experiments aimed at assessing the impact that currents have on wave buoy measurements, thereby informing processing techniques to more accurately include this effect. Through scaled testing (circa 1:15) in a combined wave–current test tank, buoy motions (diameter, D = 0.24m) are recorded in current only, waves only, and combined wave–current including oblique conditions. From these, the wave-induced motions are extracted and compared against three prediction methods based on established transfer function approaches as well as a frequency-domain hydrodynamic coefficient (HC) model based on potential flow. The scaled buoy was observed to have large, complex, irregular oscillatory vortex-induced motions (VIM) exceeding the buoy diameter. Both the magnitude and frequency of these oscillations was found to be significantly altered by the mooring stiffness and configuration whilst the addition of collinear waves was found not to affect the magnitude of VIM. Furthermore, due to the lack of VIM heave response and a large difference between the frequencies of the vortex-induced and wave induced horizontal motions, it was found that the VIM did not significantly alter the interpretation of the wave climate for the tested conditions. The HC model was found to accurately capture the observed modified hydrodynamics for opposing wave–current conditions, where larger horizontal motions than (typically) predicted are observed for all frequencies. This behaviour is concluded to result from increased excitation forces owing to the higher wavenumbers. The experiments highlight the potential effects of VIM on wave measurement performance of wave buoys, along with the complex and mooring-dependent nature of the response. Altered dynamics in the presence of currents are described which must be accounted for to avoid errors and the presented prediction methods provide a mechanism to account for these effects in wave processing methodologies which can subsequently reduce uncertainty in our understanding of the offshore environment.Engineering and Physical Sciences Research Council (EPSRC

Women’s experiences of the Odon Device to assist vaginal birth and participation in intrapartum research:a qualitative study in a maternity unit in the Southwest of England

OBJECTIVE: To investigate women’s experiences of having a birth assisted by the Odon Device (an innovative device for assisted vaginal birth) and participation in intrapartum research. DESIGN: Qualitative semistructured interviews and observations undertaken in the context of case study work embedded in the ASSIST feasibility study. SETTING: A tertiary referral National Health Service (NHS) maternity unit in the Southwest of England, between 8 October 2018 and 26 January 2019. PARTICIPANTS: Eight women, four operators and 11 midwives participated with eight observations of the assisted vaginal birth, eight interviews with women in the postnatal period, 39 interviews/reflections with operators and 19 interviews with midwives. Women in the case study research were recruited from participants in the main ASSIST Study. INTERVENTION: The Odon Device, an innovative device for assisted vaginal birth. RESULTS: Thirty-nine case studies were undertaken. Triangulation of data sources (participant observation, interviews with women, operators and midwives) enabled the exploration of women’s experiences of the Odon Device and recruitment in the intrapartum trial. Experiences were overwhelmingly positive. Women were motivated to take part by a wish for a kinder birth, and because they perceived both the recruitment and research processes (including observation) to be highly acceptable, regardless of whether the Odon-assisted birth was successful or not. CONCLUSIONS: Interviews and observations from multiple stakeholders enabled insight into women’s experiences of an innovative device for assisted vaginal birth. Applying these qualitative methods more broadly may illuminate perspectives of key stakeholders in future intrapartum intervention research and beyond. TRIAL REGISTRATION NUMBER: ISRCTN10203171; ASSIST Study registration; https://doi.org/10.1186/ISRCTN10203171

The effect of maternal dietary fat content and omega-6 to omega-3 ratio on offspring growth and hepatic gene expression in the rat

© The Authors 2020. Omega-6 fatty acids have been shown to exert pro-adipogenic effects whereas omega-3 fatty acids work in opposition. Increasing intakes of LA (linoleic acid; omega-6) vs ALA (alpha-linolenic acid; omega-3) in Western diets has led to the hypothesis that consumption of this diet during pregnancy may be contributing to adverse offspring health. This study investigated the effects of feeding a maternal dietary LA:ALA ratio similar to that of the Western diet (9:1) compared to a proposed 'ideal' ratio (∼1:1.5), at two total fat levels (18% vs 36% fat w/w), on growth and lipogenic gene expression in the offspring. Female Wistar rats were assigned to one of the four experimental groups throughout gestation and lactation. Offspring were culled at 1 and 2 weeks of age for sample collection. Offspring of dams consuming a -36% fat diet were ∼20% lighter than those exposed to a 18% fat diet (

Expression of cholesterol packaging and transport genes in human and rat placenta: impact of obesity and a high-fat diet

Evidence suggests that sub-optimal maternal nutrition has implications for the developing offspring. We have previously shown that exposure to a low-protein diet during gestation was associated with upregulation of genes associated with cholesterol transport and packaging within the placenta. This study aimed to elucidate the effect of altering maternal dietary linoleic acid (LA; omega-6) to alpha-linolenic acid (ALA; omega-6) ratios as well as total fat content on placental expression of genes associated with cholesterol transport. The potential for maternal body mass index (BMI) to be associated with expression of these genes in human placental samples was also evaluated. Placentas were collected from 24 Wistar rats at 20-day gestation (term = 21–22-day gestation) that had been fed one of four diets containing varying fatty acid compositions during pregnancy, and from 62 women at the time of delivery. Expression of 14 placental genes associated with cholesterol packaging and transfer was assessed in rodent and human samples by quantitative real time polymerase chain reaction. In rats, placental mRNA expression of ApoA2, ApoC2, Cubn, Fgg, Mttp and Ttr was significantly elevated (3–30 fold) in animals fed a high LA (36% fat) diet, suggesting increased cholesterol transport across the placenta in this group. In women, maternal BMI was associated with fewer inconsistent alterations in gene expression. In summary, sub-optimal maternal nutrition is associated with alterations in the expression of genes associated with cholesterol transport in a rat model. This may contribute to altered fetal development and potentially programme disease risk in later life. Further investigation of human placenta in response to specific dietary interventions is required

Why rogue waves occur atop abrupt depth transitions

Abrupt depth transitions (ADTs) have recently been identified as potential causes of ‘rogue’ ocean waves. When stationary and (close-to) normally distributed waves travel into shallower water over an ADT, distinct spatially localized peaks in the probability of extreme waves occur. These peaks have been predicted numerically, observed experimentally, but not explained theoretically. Providing this theoretical explanation using a leading-order-physics-based statistical model, we show, by comparing to new experiments and numerical simulations, the peaks arise from the interaction between linear free and second-order bound waves, also present in the absence of the ADT, and new second-order free waves generated due to the ADT

The ASSIST Study - The BD Odon Device for assisted vaginal birth: a safety and feasibility study.

BACKGROUND: Assisted vaginal birth is a vital health intervention that can result in better outcomes for mothers and their babies when complications arise in the second stage of labour. Unfortunately, instruments for assisted vaginal birth (forceps and ventouse) are often not utilised in settings where there is most clinical need, resulting in maternal and neonatal morbidity and mortality which could have been prevented. The BD Odon Device is a new device for assisted vaginal birth that may be able to address this unmet need. However, before dissemination, the device requires evaluation in robust clinical trials. A feasibility study to investigate the clinical impact, safety, and acceptability of the BD Odon Device for assisted vaginal birth is therefore planned. This will provide further information on acceptability, recruitment, and the outcome data required to design a future randomised controlled trial of the BD Odon Device versus Kiwi ventouse. METHODS: Forty women who require an assisted vaginal birth for a recognised clinical indication will have the birth assisted with the BD Odon Device. The primary outcome is successful vaginal birth completed with the BD Odon Device. Secondary clinical outcomes include maternal and neonatal outcomes, and maternal and practitioner satisfaction. Safety data will be reviewed following every birth. DISCUSSION: A future randomised controlled trial of the BD Odon Device versus the current standard instrument (the Kiwi ventouse) is planned. The findings of the ASSIST Study will inform the randomised controlled trial design. TRIAL REGISTRATION: ISRCTN, ISRCTN10203171 . Prospectively registered on 27 July 2018

Experimental data of bottom pressure and free surface elevation including waves and current interaction

This is the final version. Available on open access from MDPI via the DOI in this recordData Availability Statement: The data presented in this study are openly available: https://doi.org/10.7488/ds/3120.Abstract: Force plates are commonly used in tank testing to measure loads acting on the foundation of a structure. These targeted measurements are overlaid by the hydrostatic and dynamic pressure acting on the force plate induced by the waves and currents. This paper presents the dataset of bottom force measurement with a six degree-of-freedom force plate (AMTI OR6-7 1000, surface area 0.464 m×0.508 m) combined with synchronised measurements of surface elevation and current velocity. The data covers a wave frequencies between 0.2 to 0.7 Hz and wave direction between 0◦ and 180◦ . These variations are provided for 0 and 0.2 m/s current speed and a variation of current in the absence of waves covering 0 to 0.45 m/s. The dataset can be utilised as a validation dataset for models predicting bottom pressure based on free surface elevation. Additionally, the dataset provides the wave and current induced load acting on the specific load cell and a fixed water depth of 2 m, which can subsequently be removed to obtain the often-desired measurement of structural loadsEngineering and Physical Sciences Research Council (EPSRC