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The cohesive zone model (CZM) is widely employed for simulating delamination and debonding behaviour in engineering structures. However, the choice of CZM shape impacts the accuracy of simulation results. Therefore, the selection of a suitable Traction-Separation Law (TSL) with appropriate cohesive parameters is crucial. This study focuses on simulating the mode II delamination of unidirectional carbon/epoxy composites under varying moisture content levels (0%, 2.2%, 3.8%, and 5.3%) using the End Notched Flexure (ENF) test. Trapezoidal TSL (TTSL) with varying pseudo-plasticity parameter (Γ) was implemented and compared. A guideline was proposed in this study to aid in the selection of cohesive parameters, and a relationship between these parameters and moisture content was established. The results indicate that Γ = 0.99 yields a more accurate force-displacement response compared to Γ = 0. The estimated cohesive zone length falls within the range of 2.0–2.4 mm. During crack growth, the analysis reveals that, at the peak force, a region approximately 0.5–0.6 mm ahead of the crack tip undergoes total failure. Simultaneously, damage initiation occurs in the region 2.3–2.4 mm beyond the complete failure zone.

In this study, a latent and tacky epoxy resin (EP) modified with siloxane core-shell-particles was developed and investigated. The use of EP as a towpreg matrix for winding of cryogenic composite vessels requires a certain toughness to resist microcracking. First, the mechanical properties at +90 °C, +22 °C, −50 °C and −196 °C were examined, with emphasis on the fracture toughness at cryogenic temperatures. Although the modulus of the resin increased dramatically, the KIC also increased by + 100% at −196 °C. Compression testing revealed that the associated yield point increased up to 500 MPa at −196 °C. The yield point of the modified resins was reduced by almost 10% which leads to easier yielding and enabling toughening mechanisms. Thus, the KIC value clearly is not the primary property that needs to be improved in cryogenics. Second, the radius of the plastic zone around the crack tip (Rp) was calculated. It decreased mathematically from 1.9 μm to 0.4 μm, due to a reduced energy dissipation resulting from a smaller spatial expansion of the plastic deformation zone. Finally, an optimum value of 3% by volume of polydimethylsiloxane was identified, demonstrating an increase of the Rp to 1.8 μm at −196 °C and proving the necessity of combinatorial methods to understand temperature-dependent failure of epoxy matrices.

To understand the bioaccumulation and food web dynamics of persistent organic pollutants (POPs) as a function of species, age and sex in Antarctic mammals, blubber samples of 3 killer whales (Type C) and 77 pinnipeds (Weddell, Ross and crabeater seals) were collected from the Southern Ocean, Antarctica. They were analyzed for polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs). ΣDDTs, Σ29PCBs and chlordanes (12 – 4,600, 13 – 1,600, and < 1.5 – 1,700 ng/g lipid, respectively) were the most abundant POPs. Killer whales typically displayed several times greater concentrations of POPs compared to seals, except for PBDEs. PCBs and PBDEs were consistently higher in adult crabeater and Weddell seal males, and in adult female Ross seals than in other sex and age groups reflecting an age accumulation and possible influence of segregated diet, foraging areas, and metabolic transformation rates. POPs concentrations significantly correlated with gene transcription of nuclear receptors involved in detoxification of contaminants and immune relevant cell mediators in the crabeater seals, indicating possible immunotoxic and deleterious health effects. This represents one of the largest studies on POPs in Antarctic marine predators and highlights the complexity of POPs bioaccumulation.

In this study, application relevant toughened epoxy-amine formulations were investigated regarding their mechanical behavior at low temperatures and compared to a non-toughened reference. The application-oriented resins are based on reactive diluent-modified diglycidylether of bisphenol A (DGEBA) which were tested at 22 °C and −50 °C in regard to their fracture toughness (KIC) and fatigue crack propagation (da/dN) behavior. The E′ and E’’ moduli and the corresponding glass transition temperatures Tg were determined via dynamic mechanical thermal analyses (DMTA) which also described the influence of the block copolymeric toughener on the epoxy resin network. The plastic zone size, calculated during crack propagation, reveals the temperature dependent toughener-matrix interaction. The prevailing energy dissipation mechanisms were correlated with the changes of E’. SEM micrographs confirm the superior performance of the toughened system at −50 °C by the decrease of the fatigue cack propagation slopes and highlight the trends of the materials low temperature behavior.

Abstract Background Even clearly resectable pancreatic cancer still has an unfavorable prognosis. Neoadjuvant or perioperative therapies might improve the prognosis of these patients. Thus, evaluation of perioperative chemotherapy in resectable pancreatic cancer in a prospective, randomized trial is warranted. A substantial improvement in overall survival of patients with metastatic pancreatic cancer with FOLFIRINOX and nab-paclitaxel/gemcitabine vs standard gemcitabine has been demonstrated in phase III-trials. Indeed nab-paclitaxel/gemcitabine has a more favorable toxicity profile compared to the FOLFIRINOX protocol and appears applicable in a perioperative setting. Methods NEONAX is an interventional, prospective, randomized, controlled, open label, two sided phase II study with an unconnected analysis of the results in both experimental arms against a fixed survival probability (38% at 18 months with adjuvant gemcitabine), NCT02047513. NEONAX will enroll 166 patients with resectable pancreatic ductal adenocarcinoma (≤ cT3, N0 or N1, cM0) in two arms: Arm A (perioperative arm): 2 cycles nab-paclitaxel (125 mg/m2)/gemcitabine (1000 mg/m2, d1, 8 and 15 of an 28 day-cycle) followed by tumor surgery followed by 4 cycles nab-paclitaxel/gemcitabine, Arm B (adjuvant arm): tumor surgery followed by 6 cycles nab-paclitaxel/gemcitabine. The randomization (1:1) is eminent to avoid allocation bias between the groups. Randomization is stratified for tumor stage (ct1/2 vs. cT3) and lymph node status (cN0 vs. cN1). Primary objective is disease free survival (DFS) at 18 months after randomization. Key secondary objectives are 3-year overall survival (OS) rate and DFS rate, progression during neoadjuvant therapy, R0 and R1 resection rate, quality of life and correlation of DFS, OS and tumor regression with pharmacogenomic markers, tumor biomarkers and molecular analyses (ctDNA, transcriptome, miRNA-arrays). In addition, circulating tumor-DNA will be analyzed in patients with the best and the worst responses to the neoadjuvant treatment. The study was initiated in March 2015 in 26 centers for pancreatic surgery in Germany. Discussion The NEONAX trial is an innovative study on resectable pancreatic cancer and currently one of the largest trials in this field of research. It addresses the question of the role of intensified perioperative treatment with nab-paclitaxel plus gemcitabine in resectable pancreatic cancers to improve disease-free survival and offers a unique potential for translational research. Trial registration ClinicalTrials.gov: NCT02047513, 08/13/2014.

I. INTRODUCTION II. BACKGROUND A. Ethical Approaches to Intellectual Property Theory 1. Utilitarianism 2. Labor Theory 3. Personhood Theory 4. Social Planning Theory B. Human Rights Ethics and Access to [...]