Modelling and quantifying Mode I interlaminar fracture in particle-toughened CFRPs

Four-dimensional time-resolved Synchrotron Radiation Computed Tomography (SRCT) has been used to capture Mode I delamination propagation in particle-toughened Carbon Fibre Reinforced Polymers (CFRPs). Digital Volume Correlation (DVC) was used in order to measure ply opening displacements at the crack tip, permitting the interlayer strain ahead of the crack tip to be quantified. Estimates at which toughening particles de-bonded and/or fractured were made, giving insight into the effects of particle type and particle size on the fracture mico-mechanisms. The experiments are complemented by a 2D plane-strain finite element (FE) model, which investigated the effects of particle strength and toughness on the ply opening displacement and crack path by modelling the particles as 1D cohesive segments. Previous work has shown that Mode I crack propagation in particle-toughened interlayers involves a process zone rather than a distinct crack tip. Therefore, Augmented Finite Element Method (A-FEM) elements were used in the simulation, since the elements can account for both bifurcating and merging cracks within a single element. The nodal displacements in the simulation were compared to the DVC results, illustrating a potential path through which more complex FE simulations may be validated against experimental results in the future

Predictors of employment in bipolar disorder : a systematic review

Background Severe work impairment can be present for a considerable proportion of the course of bipolar disorder (BD) and is costly for governments, services and individuals. Understanding predictors of employment in BD is therefore crucial as some may be susceptible to interventions. We conducted a systematic review of prospective studies in order to identify predictors of employment in people with BD. Methods We searched Medline, PsychInfo, EMBASE and Web of Science databases, hand searched 3 journals and used predetermined criteria to select papers for full text inclusion. Sixty seven papers were identified. Nine met inclusion criteria, with a total sample of 3184. Results Studies included in this review identified cognitive deficits (67%, n=4), depression (43%, n=3) and level of education (33%, n=2) as predictors of employment in BD patients. Bipolar depression not only affects whether someone is employed but also time off work. Even sub-syndromal depression appears to damage employment prospects. Verbal memory and executive functioning appear to be predictors of work functioning. Limitations Conclusions are based on a relatively small number of studies and are therefore subject to change with the addition of further studies. A formal meta-regression was not possible due to differences between measures of employment and work functioning. Conclusions Better assessment and management of depression and cognitive difficulties could improve the occupational functioning of BD patients. There is a need for high quality longitudinal studies specifically designed to investigate predictors of employment in large bipolar disorder samples

Effects of asenapine on depressive symptoms in patients with bipolar I disorder experiencing acute manic or mixed episodes: a post hoc analysis of two 3-week clinical trials

<p>Abstract</p> <p>Background</p> <p>Asenapine demonstrated superiority over placebo for mania in bipolar I disorder patients experiencing acute current manic or mixed episodes in 2 randomized, placebo-and olanzapine-controlled trials. We report the results of exploratory pooled post hoc analyses from these trials evaluating asenapine's effects on depressive symptoms in patients from these trials with significant baseline depressive symptoms.</p> <p>Methods</p> <p>In the original trials (A7501004 [NCT00159744], A7501005 [NCT00159796]), 977 patients were randomized to flexible-dose sublingual asenapine (10 mg twice daily on day 1; 5 or 10 mg twice daily thereafter), placebo, or oral olanzapine 5-20 mg once daily for 3 weeks. Three populations were defined using baseline depressive symptoms: (1) Montgomery-Asberg Depression Rating Scale (MADRS) total score ≥20 (n = 132); (2) Clinical Global Impression for Bipolar Disorder-Depression (CGI-BP-D) scale severity score ≥4 (n = 170); (3) diagnosis of mixed episodes (n = 302) by investigative site screening. For each population, asenapine and olanzapine were independently compared with placebo using least squares mean change from baseline on depressive symptom measures.</p> <p>Results</p> <p>Decreases in MADRS total score were statistically greater with asenapine versus placebo at days 7 and 21 in all populations; differences between olanzapine and placebo were not significant. Decreases in CGI-BP-D score were significantly greater with asenapine versus placebo at day 7 in all categories and day 21 in population 1; CGI-BP-D score reductions were significantly greater with olanzapine versus placebo at day 21 in population 1 and day 7 in populations 2 and 3.</p> <p>Conclusions</p> <p>These post hoc analyses show that asenapine reduced depressive symptoms in bipolar I disorder patients experiencing acute manic or mixed episodes with clinically relevant depressive symptoms at baseline; olanzapine results appeared to be less consistent. Controlled studies of asenapine in patients with acute bipolar depression are necessary to confirm the generalizability of these findings.</p

Treatment and outcomes of an Australian cohort of outpatients with bipolar 1 or schizoaffective disorder over twenty-four months : implications for clinical practice

Background The Bipolar Comprehensive Outcomes Study (BCOS) is a 2-year, prospective, non-interventional, observational study designed to explore the clinical and functional outcomes associated with &lsquo;real-world&rsquo; treatment of participants with bipolar I or schizoaffective disorder. All participants received treatment as usual. There was no study medication.Methods Participants prescribed either conventional mood stabilizers (CMS; n&thinsp;=&thinsp;155) alone, or olanzapine with, or without, CMS (olanzapine&thinsp;&plusmn;&thinsp;CMS; n&thinsp;=&thinsp;84) were assessed every 3&thinsp;months using several measures, including the Young Mania Rating Scale, 21-item Hamilton Depression Rating Scale, Clinical Global Impressions Scale &ndash; Bipolar Version, and the EuroQol Instrument. This paper reports 24-month longitudinal clinical, pharmacological, functional, and socioeconomic data.Results On average, participants were 42 (range 18 to 79) years of age, 58%; were female, and 73%; had a diagnosis of bipolar I. Polypharmacy was the usual approach to pharmacological treatment; participants took a median of 5 different psychotropic medications over the course of the study, and spent a median proportion of time of 100%; of the study on mood stabilizers, 90%; on antipsychotics, 9%; on antidepressants, and 5%; on benzodiazepines/hypnotics. By 24&thinsp;months, the majority of participants had achieved both symptomatic and syndromal remission of both mania and depression. Symptomatic relapse rates were similar for both the CMS alone (65%;) and the olanzapine&thinsp;&plusmn;&thinsp;CMS (61%;) cohorts.Conclusions Participants with bipolar I or schizoaffective disorder in this study were receiving complex medication treatments that were often discordant with recommendations made in contemporary major treatment guidelines. The majority of study participants demonstrated some clinical and functional improvements, but not all achieved remission of symptoms or syndrome.<br /

Fludarabine, cytarabine, granulocyte colony-stimulating factor, and idarubicin with gemtuzumab ozogamicin improves event-free survival in younger patients with newly diagnosed aml and overall survival in patients with npm1 and flt3 mutations

Purpose To determine the optimal induction chemotherapy regimen for younger adults with newly diagnosed AML without known adverse risk cytogenetics. Patients and Methods One thousand thirty-three patients were randomly assigned to intensified (fludarabine, cytarabine, granulocyte colony-stimulating factor, and idarubicin [FLAG-Ida]) or standard (daunorubicin and Ara-C [DA]) induction chemotherapy, with one or two doses of gemtuzumab ozogamicin (GO). The primary end point was overall survival (OS). Results There was no difference in remission rate after two courses between FLAG-Ida + GO and DA + GO (complete remission [CR] + CR with incomplete hematologic recovery 93% v 91%) or in day 60 mortality (4.3% v 4.6%). There was no difference in OS (66% v 63%; P = .41); however, the risk of relapse was lower with FLAG-Ida + GO (24% v 41%; P < .001) and 3-year event-free survival was higher (57% v 45%; P < .001). In patients with an NPM1 mutation (30%), 3-year OS was significantly higher with FLAG-Ida + GO (82% v 64%; P = .005). NPM1 measurable residual disease (MRD) clearance was also greater, with 88% versus 77% becoming MRD-negative in peripheral blood after cycle 2 (P = .02). Three-year OS was also higher in patients with a FLT3 mutation (64% v 54%; P = .047). Fewer transplants were performed in patients receiving FLAG-Ida + GO (238 v 278; P = .02). There was no difference in outcome according to the number of GO doses, although NPM1 MRD clearance was higher with two doses in the DA arm. Patients with core binding factor AML treated with DA and one dose of GO had a 3-year OS of 96% with no survival benefit from FLAG-Ida + GO. Conclusion Overall, FLAG-Ida + GO significantly reduced relapse without improving OS. However, exploratory analyses show that patients with NPM1 and FLT3 mutations had substantial improvements in OS. By contrast, in patients with core binding factor AML, outcomes were excellent with DA + GO with no FLAG-Ida benefit

Assessment of laminate damage micromechanisms using high resolution synchrotron radiation computed tomography &amp; laminography

Laminated fibre reinforced polymer composite materials are increasingly being applied within critical structures, with a corresponding demand for reliable damage prediction tools to reduce the time and cost associated with product development. The present work is carried out to underpin the evolution of micromechanically-based models by providing developers with a resource of 4D (time &amp; spatially resolved) microstructural and micromechanical data obtained from high-resolution synchrotron radiation computed tomography of essentially standard materials. The intention is to share data with the composites community as part of the public materials data repository that is currently being developed within the University of Southampton’s School of Engineering Sciences. Testing was conducted at the European Synchrotron Radiation Facility (ESRF) during in-situ loading of [90/0]s laminate in both small tensile coupon and larger plate forms. Image processing has been used to visualize the evolution of transverse ply cracks, longitudinal splits, inter-ply delaminations and associated interactions. Methods for full-field and full-volume crack displacement (e.g. mode I &amp; II opening) are discussed

Optimization of micro and nanoimprint de-embossing by elastic fracture modelling

A semi-analytical model is presented for the de-embossing phase of the nanoimprint patterning process. The model is based on established principles of elastic fracture mechanics as developed for fibre-bridged cracking in composites. De-embossing is idealized as a steady-state fracture process, which enables the energy change to be considered by reference to a unit cell of a cylindrical polymer post, de-embossing from an axisymmetric stamp. The model provides predictions of the achievable limits for de-embossing as a function of key geometrical variables such as feature size, area ratio and aspect ratio and material properties such as interfacial adhesion, shear strength, polymer yield strength and the ratio of the elastic moduli of the polymer and the stamp. Process 'maps' have been created showing de-embossing limits. A strong dependence of the achievable aspect ratio on the pattern area ratio and the interfacial shear stress is seen. For polymer yield stresses similar to that of PMMA, the critical interfacial strain energy release rate has little effect on de-embossing. Large area and aspect ratios are predicted to be achievable by keeping the ratio of polymer and stamp Young's moduli between 0.015 and 2.5. The model provides key insights into the physical origins of previously observed limits on the achievable aspect ratios and area ratios achieved by imprint patternin

Modeling of thermally driven resonance at multiscales

Understanding the mechanisms of thermally driven resonance is a key for designing many engineering and physical systems especially at small scales. This paper focuses on the modeling aspects of such phenomena using the classical Fourier diffusion theory. Critical analysis revealed that the thermally induced resonant excitation is characterized by the generation of multiple wave trains with a constant phase shift as opposed to the single standing wave generated in a mechanically driven resonant response. The hypothesis proposed herein, underpin a broad range of scientific and technological developments and the analytical treatment enables design of thermally driven resonant systems with improved performanc

Material selection for optimal design of thermally actuated pneumatic and phase change microactuators

This paper discusses a methodology to select materials which deliver the best performance for thermally actuated pneumatic and phase change microactuators. The material selection is based on performance metrics estimated using simple closed form solutions for classical linear elastic theory for axisymmetric plates/membranes and lumped heat capacity thermal models. Although the elastic moduli of the diaphragm materials dictate the volume expansion for a given temperature rise, their influence on the achievable pressure difference is much less. It is found that engineering polymers are most suitable for thermopneumatically actuated diaphragms for delivering large displacements and work for the achievable pressures at frequencies of a few hundreds of Hertz. The membrane stresses due to in-plane pre-tension are found to have an adverse effect on the actuator performance. The material issues which constrain the performance limits of phase change actuators are also assessed, and the promising characteristics of paraffin waxes for microsystem applications are discussed

Fibre failure assessment in carbon fibre reinforced polymers under fatigue loading by synchrotron X-ray computed tomography

In situ fatigue experiments using synchrotron X-ray computed tomography (SRCT) are used to assess the underpinning micromechanisms of fibre failure in double notch carbon/epoxy coupons. Observations showed fibre breaks along the 0º ply splits, associated with the presence and failure of bridging fibres, as well as fibres failed in the bulk composite within the 0º plies. A tendency for cluster formation, with multiple adjacent breaks in the bulk composite was observed when higher peak loads were applied, exceeding 70% of the ultimate tensile strength. Ex situ fatigue tests were used to assess the accumulation and distribution of fibre breaks for different loading conditions, varying peak load and number of cycles. A direct comparison with the quasi-static case for an equivalent peak load, considering the same material system and geometry, has shown that fatigue produces a significantly higher number of fibre breaks. This supports the hypothesis that fibre breaks are indeed caused by the load cycling