Characterising resistance to fatigue crack growth in adhesive bonds by measuring release of strain energy

Measurement of the energy dissipation during fatigue crack growth is used as a technique to gain more insight into the physics of the crack growth process. It is shown that the amount of energy dissipation required per unit of crack growth is determined by Gmax, whereas the total amount of energy available for crack growth in a single cycle is determined by (Δ √g)2

Thickness effects on fibre-bridged fatigue delamination growth in composites

This paper provides an investigation on thickness effects on fibre-bridged fatigue delamination growth (FDG) in composite laminates. A modified Paris relation was employed to interpret experimental fatigue data. The results clearly demonstrated that both thickness and fibre bridging had negligible effects on FDG behaviors. Both energy principles and fractography analysis were subsequently performed to explore the physical reasons of this independence. It was found that the amount of energy release of a given crack growth was not only independent of fibre bridging, but also thickness. Fibre print was the dominant microscopic feature located on fracture surfaces, physically making the same energy dissipation during FDG. Furthermore, the present study provides extra evidence on the importance of using an appropriate similitude parameter in FDG studies. Particularly, the strain energy release rate (SERR) range applied around crack front was demonstrated as an appropriate similitude parameter for fibre-bridged FDG study

Образование в контексте идентификационных процессов (Субъект образования как следствие концептуальной рамки)

The available models for the prediction of fatigue crack growth in adhesive bonds rely on the similitude principle. In most cases, one of three similitude parameters based on the strain energy release rate (SERR) is used; i.e. Gmax, (Δ√G)2, or ΔG. In all cases it is usually observed that keeping the similitude parameter constant, and changing the R-ratio, results in a different crack growth rate. In this paper it is shown that this apparent ‘R-ratio’ effect is caused because the selected similitude parameter does not define a unique load cycle; a single value of the similitude parameter could correspond to infinitely many load cycles. The strain energy dissipation approach is used to show that the resistance to fatigue crack growth is related to the maximum applied load. The amount of energy available for crack growth is shown to be related to the applied cyclic work. With these relationships the R-ratio effects reported in literature can be qualitatively explained, purely in terms of the actual applied load cycle. Although it is possible that the material behaviour also depends on the R-ratio, the magnitude of these effects can only properly be determined if the applied load cycle is correctly described first.Structural Integrity & CompositesAerospace Structures & Material

Unobtrusive cot side sleep stage classification in preterm infants using ultra-wideband radar

Background: Sleep is an important driver of development in infants born preterm. However, continuous unobtrusive sleep monitoring of infants in the neonatal intensive care unit (NICU) is challenging.Objective: To assess the feasibility of ultra-wideband (UWB) radar for sleep stage classification in preterm infants admitted to the NICU.Methods: Active and quiet sleep were visually assessed using video recordings in 10 preterm infants (recorded between 29 and 34 weeks of postmenstrual age) admitted to the NICU. UWB radar recorded all infant's motions during the video recordings. From the baseband data measured with the UWB radar, a total of 48 features were calculated. All features were related to body and breathing movements. Six machine learning classifiers were compared regarding their ability to reliably classify active and quiet sleep using these raw signals.Results: The adaptive boosting (AdaBoost) classifier achieved the highest balanced accuracy (81%) over a 10-fold cross-validation, with an area under the curve of receiver operating characteristics (AUC-ROC) of 0.82.Conclusions: The UWB radar data, using the AdaBoost classifier, is a promising method for non-obtrusive sleep stage assessment in very preterm infants admitted to the NICU

Stillbirth differences according to regions of origin: an analysis of the German perinatal database, 2004-2007

Reeske A, Kutschmann M, Razum O, Spallek J. Stillbirth differences according to regions of origin: an analysis of the German perinatal database, 2004-2007. BMC Pregnancy and Childbirth. 2011;11(1): 63.Background: Stillbirth is a sensitive indicator for access to, and quality of health care and social services in a society. If a particular population group e. g. migrants experiences higher rates of stillbirth, this might be an indication of social deprivation or barriers to health care. This study examines differences in risk of stillbirth for women of different regions of origin compared to women from Germany in order to identify high risk groups/target groups for prevention strategies. Methods: We used the BQS dataset routinely compiled to examine perinatal outcomes in Germany nationwide. Participation of hospitals and completeness of data has been about 98% in recent years. Data on all live births and stillbirths were obtained for the period 2004 to 2007 (N = 2,670,048). We calculated crude and stratified mortality rates as well as corresponding relative mortality risks. Results: A significantly elevated stillbirth rate was found for women from the Middle East and North Africa (incl. Turkey) (RR 1.34, CI 1.22-1.55). The risk was slightly attenuated for low SES. An elevated risk was also found for women from Asia (RR 1.18, CI 1.02-1.65) and from Mediterranean countries (RR 1.14, CI 0.93-1.28). No considerable differences either in use and timing of antenatal care or preterm birth and low birthweight were observed between migrant and non-migrant women. After stratification for light for gestational age, the relative risk of stillbirth for women from the Middle East/North Africa increased to 1.63 (95% CI 1.25-2.13). When adjusted for preterm births with low birthweight, women from Eastern Europe and the Middle East/North Africa experienced a 26% (43%) higher risk compared with women from Germany. Conclusions: We found differences in risk of stillbirth among women from Middle East/North Africa, especially in association with low SES and low birthweight for gestational age. Our findings suggest a need for developing and evaluating socially and culturally sensitive health promotion and prevention programmes for this group. The findings should also stimulate discussion about the quality and appropriateness of antenatal and perinatal care of pregnant women and newborns with migrant backgrounds

Individual accumulation of heterogeneous risks explains perinatal inequalities within deprived neighbourhoods

Dutch' figures on perinatal mortality and morbidity are poor compared to EU-standards. Considerable within-country differences have been reported too, with decreased perinatal health in deprived urban areas. We investigated associations between perinatal risk factors and adverse perinatal outcomes in 7,359 pregnant women participating in population-based prospective cohort study, to establish the independent role, if any, for living within a deprived urban neighbourhood. Main outcome measures included perinatal death, intrauterine growth restriction (IUGR), prematurity, congenital malformations, Apgar at 5 min < 7, and pre-eclampsia. Information regarding individual risk factors was obtained from questionnaires, physical examinations, ultrasounds, biological samples, and medical records. The dichotomous Dutch deprivation indicator was additionally used to test for unexplained deprived urban area effects. Pregnancies from a deprived neighbourhood had an increased risk for perinatal death (RR 1.8, 95% CI [1.1; 3.1]). IUGR, prematurity, Apgar at 5 min < 7, and pre-eclampsia also showed higher prevalences (P < 0.05). Residing within a deprived neighbourhood was associated with increased prevalence of all measured risk factors. Regression analysis showed that the observed neighbourhood related differences in perinatal outcomes could be attributed to the increased risk factor prevalence only, without a separated role for living within a deprived neighbourhood. Women from a deprived neighbourhood had significantly more 'possibly avoidable' risk factors. To conclude, women from a socioeconomically deprived neighbourhood are at an increased risk for adverse pregnancy outcomes. Differences regarding possibly avoidable risk factors imply that preventive strategies may prove effective

A novel amplitude binning strategy to handle irregular breathing during 4DMRI acquisition: improved imaging for radiotherapy purposes.

Background For radiotherapy of abdominal cancer, four-dimensional magnetic resonance imaging (4DMRI) is desirable for tumor definition and the assessment of tumor and organ motion. However, irregular breathing gives rise to image artifacts. We developed a outlier rejection strategy resulting in a 4DMRI with reduced image artifacts in the presence of irregular breathing.Methods We obtained 2D T2-weighted single-shot turbo spin echo images, with an interleaved 1D navigator acquisition to obtain the respiratory signal during free breathing imaging in 2 patients and 12 healthy volunteers. Prior to binning, upper and lower inclusion thresholds were chosen such that 95% of the acquired images were included, while minimizing the distance between the thresholds (inclusion range (IR)). We compared our strategy (Min95) with three commonly applied strategies: phase binning with all images included (Phase), amplitude binning with all images included (MaxIE), and amplitude binning with the thresholds set as the mean end-inhale and mean end-exhale diaphragm positions (MeanIE). We compared 4DMRI quality based on: Data included (DI); percentage of images remaining after outlier rejection. Reconstruction completeness (RC); percentage of bin-slice combinations containing at least one image after binning. Intra-bin variation (IBV); interquartile range of the diaphragm position within the bin-slice combination, averaged over three central slices and ten respiratory bins. IR. Image smoothness (S); quantified by fitting a parabola to the diaphragm profile in a sagittal plane of the reconstructed 4DMRI. A two-sided Wilcoxon's signed-rank test was used to test for significance in differences between the Min95 strategy and the Phase, MaxIE, and MeanIE strategies.Results Based on the fourteen subjects, the Min95 binning strategy outperformed the other strategies with a mean RC of 95.5%, mean IBV of 1.6 mm, mean IR of 15.1 mm and a mean S of 0.90. The Phase strategy showed a poor mean IBV of 6.2 mm and the MaxIE strategy showed a poor mean RC of 85.6%, resulting in image artifacts (mean S of 0.76). The MeanIE strategy demonstrated a mean DI of 85.6%.Conclusions Our Min95 reconstruction strategy resulted in a 4DMRI with less artifacts and more precise diaphragm position reconstruction compared to the other strategies.Trial registration Volunteers: protocol W15_373#16.007; patients: protocol NL47713.018.14

Maternal care and birth outcomes among ethnic minority women in Finland

<p>Abstract</p> <p>Background</p> <p>Care during pregnancy and labour is of great importance in every culture. Studies show that people of migrant origin have barriers to obtaining accessible and good quality care compared to people in the host society. The aim of this study is to compare the access to and use of maternity services, and their outcomes among ethnic minority women having a singleton birth in Finland.</p> <p>Methods</p> <p>The study is based on data from the Finnish Medical Birth Register in 1999–2001 linked with the information of Statistics Finland on woman's country of birth, citizenship and mother tongue. Our study data included 6,532 women of foreign origin (3.9% of all singletons) giving singleton birth in Finland during 1999–2001 (compared to 158,469 Finnish origin singletons).</p> <p>Results</p> <p>Most women have migrated during the last fifteen years, mainly from Russia, Baltic countries, Somalia and East Europe. Migrant origin women participated substantially in prenatal care. Interventions performed or needed during pregnancy and childbirth varied between ethnic groups. Women of African and Somali origin had most health problems resulted in the highest perinatal mortality rates. Women from East Europe, the Middle East, North Africa and Somalia had a significant risk of low birth weight and small for gestational age newborns. Most premature newborns were found among women from the Middle East, North Africa and South Asia. Primiparous women from Africa, Somalia and Latin America and Caribbean had most caesarean sections while newborns of Latin American origin had more interventions after birth.</p> <p>Conclusion</p> <p>Despite good general coverage of maternal care among migrant origin women, there were clear variations in the type of treatment given to them or needed by them. African origin women had the most health problems during pregnancy and childbirth and the worst perinatal outcomes indicating the urgent need of targeted preventive and special care. These study results do not confirm either healthy migrant effect or epidemiological paradox according to which migrant origin women have considerable good birth outcomes.</p

Systemic pro-inflammatory cytokine status following therapeutic hypothermia in a piglet hypoxia-ischemia model

BACKGROUND: Inflammatory cytokines are implicated in the pathogenesis of perinatal hypoxia-ischemia (HI). The influence of hypothermia (HT) on cytokines after HI is unclear. Our aim was to assess in a piglet asphyxia model, under normothermic (NT) and HT conditions: (i) the evolution of serum cytokines over 48 h and (ii) cerebrospinal fluid (CSF) cytokine levels at 48 h; (iii) serum pro/anti-inflammatory cytokine profile over 48 h and (iv) relation between brain injury measured by magnetic resonance spectroscopy (MRS) and brain TUNEL positive cells with serum cytokines, serum pro/anti-inflammatory cytokines and CSF cytokines. METHODS: Newborn piglets were randomized to NT (n = 5) or HT (n = 6) lasting 2-26 h after HI. Serum samples were obtained 4-6 h before, during and at 6-12 h intervals after HI; CSF was obtained at 48 h. Concentrations of interleukin (IL)-1beta, -4, -6, -8, -10 and TNF-alpha were measured and pro/anti-inflammatory status compared between groups. White matter and thalamic voxel lactate/N-acetyl aspartate (Lac/NAA) (a measure of both oxidative metabolism and neuronal loss) were acquired at baseline, after HI and at 24 and 36 h. RESULTS: Lac/NAA was reduced at 36 h with HT compared to NT (p = 0.013 basal ganglia and p = 0.033 white matter). HT showed lower serum TNF-alpha from baseline to 12 h (p < 0.05). Time-matched (acquired within 5 h of each other) serum cytokine and MRS showed correlations between Lac/NAA and serum IL-1beta and IL-10 (all p < 0.01). The pro/anti-inflammatory ratios IL-1beta/IL-10, IL-6/IL-10, IL-4/IL-10 and IL-8/IL-10 were similar in NT and HT groups until 36 h (24 h for IL-6/IL-10); after this, 36 h pro/anti-inflammatory cytokine ratios in the serum were higher in HT compared to NT (p < 0.05), indicating a pro-inflammatory cytokine surge after rewarming in the HT group. In the CSF at 48 h, IL-8 was lower in the HT group (p < 0.05). At 48 h, CSF TNF-alpha correlated with Lac/NAA (p = 0.02) and CSF IL-8 correlated with white matter TUNEL positive cell death (p = 0.04). CONCLUSIONS: Following cerebral HI, there was a systemic pro-inflammatory surge after rewarming in the HT group, which is counterintuitive to the putative neuroprotective effects of HT. While serum cytokines were variable, elevations in CSF inflammatory cytokines at 48 h were associated with MRS Lac/NAA and white matter cell death