Comparison of Quasi-static and Cyclic Fatigue Delamination Resistance of Carbon Fiber Reinforced Polymer-matrix Laminates under Different Mode Loading

AbstractDelamination resistance data from different carbon-fiber reinforced polymer-matrix (CFRP) composites are compared for different loading modes, i.e., quasi-static and cyclic fatigue, opening tensile mode I, in-plane shear mode II, and fixed-ratio mixed-mode I/II. For this, data from round robin tests conducted at the authors laboratories will be complemented by selected results from literature. Questions related to delamination resistance of CFRP composites with implications for composite structural design and testing include, e.g., the determination of threshold values in cyclic fatigue, the question of conservative mode (mode I versus mode II), approaches for data analysis, and possible analogies in short crack cyclic fatigue between fracture behavior of structural metal alloys and CFRP. The scatter in Paris-type law data analysis of cyclic fatigue tests and the resulting apparent threshold behavior that has implications for composite structural design will be presented. Load measurement resolution yields the major contribution to scatter in displacement controlled fatigue tests. The analogous displacement resolution for load controlled tests is discussed and limitations in test control and of power law displacement data fitting for analysis are pointed out

CHARACTERIZATION OF THE DAMPING BEHAVIOR OF THIN FILMS WITH DYNAMIC MECHANIC ANALYSIS IN BENDING MODE

ABSTRACT Usually damped structures, consisting of a constrained layer damping (CLD) and free layer damping (FLD) design, are characterized via dynamic mechanic analysis (DMA) in bending mode. Since laminates with thicknesses from 10 to 100 µm exhibit a very low bending stiffness it isn't possible to determine their damping properties in bending mode with standard DMA setups. Therefore in the present work the main objective was to introduce a new method to overcome this drawback. Two main geometries were used, such as a variation of the bending mode where the laminates were clamped at the outer supports and on the other hand a set-up where the geometry of a support of loudspeakers was replicated, which was called "speaker" mode. The damping behavior of the laminates then was characterized via the mechanical loss factor tan δ and subsequently compared to results in DMA shear mode. The second objective was to characterize the influence of the design, with a 2-layer laminate consisting of a free layer damping design and a 3-layer laminate with a constrained layer damping design. A method in DMA "speaker" mode was successfully set up. The test parameters were chosen in order to resemble the support of loudspeakers. Therefore with the laminates two beads with a height of approximately 1 mm were formed symmetrically in gaps of 3 mm between the outer fixtures and the drive shaft. Furthermore in the test the laminates were loaded with a dynamic displacement of 600 µm. Due to the low bending stiffness of the laminates the highest test frequency was limited to 10 Hz. In accordance with literature for the 2-layer laminates significant lower damping levels were found than for the 3-layer laminates. Whereas the constrained layer damping laminate (3-layer) showed a good correlation between measurements in "speaker" and in shear mode, the 2-layer laminate showed a significant loss factor increase at high temperatures in shear mode, which was related to entropy elastic effects. Keywords: constrained layer damping, dynamic mechanic analysis, thin laminates, mechanical damping, bending mode NOMENCLATURE CLD constrained layer damping. DMA dynamic mechanic analysis. FLD free layer damping. tan δ mechanical loss factor

Climate extremes and grassland potential productivity

The considerable interannual variability (IAV) (~5 PgC yr−1) observed in atmospheric CO2 is dominated by variability in terrestrial productivity. Among terrestrial ecosystems, grassland productivity IAV is greatest. Relationships between grassland productivity IAV and climate drivers are poorly explained by traditional multiple-regression approaches. We propose a novel method, the perfect-deficit approach, to identify climate drivers of grassland IAV from observational data. The maximum daily value of each ecological or meteorological variable for each day of the year, over the period of record, defines the \u27perfect\u27 annual curve. Deficits of these variables can be identified by comparing daily observational data for a given year against the perfect curve. Links between large deficits of ecosystem activity and extreme climate events are readily identified. We applied this approach to five grassland sites with 26 site-years of observational data. Large deficits of canopy photosynthetic capacity and evapotranspiration derived from eddy-covariance measurements, and leaf area index derived from satellite data occur together and are driven by a local-dryness index during the growing season. This new method shows great promise in using observational evidence to demonstrate how extreme climate events alter yearly dynamics of ecosystem potential productivity and exchanges with atmosphere, and shine a new light on climate–carbon feedback mechanisms

PIDDosome-induced p53-dependent ploidy restriction facilitates hepatocarcinogenesis

Polyploidization frequently precedes tumorigenesis but also occurs during normal development in several tissues. Hepatocyte ploidy is controlled by the PIDDosome during development and regeneration. This multi-protein complex is activated by supernumerary centrosomes to induce p53 and restrict proliferation of polyploid cells, otherwise prone for chromosomal instability. PIDDosome deficiency in the liver results in drastically increased polyploidy. To investigate PIDDosome-induced p53-activation in the pathogenesis of liver cancer, we chemically induced hepatocellular carcinoma (HCC) in mice. Strikingly, PIDDosome deficiency reduced tumor number and burden, despite the inability to activate p53 in polyploid cells. Liver tumors arise primarily from cells with low ploidy, indicating an intrinsic pro-tumorigenic effect of PIDDosome-mediated ploidy restriction. These data suggest that hyperpolyploidization caused by PIDDosome deficiency protects from HCC. Moreover, high tumor cell density, as a surrogate marker of low ploidy, predicts poor survival of HCC patients receiving liver transplantation. Together, we show that the PIDDosome is a potential therapeutic target to manipulate hepatocyte polyploidization for HCC prevention and that tumor cell density may serve as a novel prognostic marker for recurrence-free survival in HCC patients

Adjuvant nab-Paclitaxel + Gemcitabine in Resected Pancreatic Ductal Adenocarcinoma: Results From a Randomized, Open-Label, Phase III Trial

PURPOSE: This randomized, open -label trial compared the efficacy and safety of adjuvant nabpaclitaxel + gemcitabine with those of gemcitabine for resected pancreatic ductal adenocarcinoma (ClinicalTrials.gov identifier: NCT01964430). METHODS: We assigned 866 treatment -naive patients with pancreatic ductal adenocarcinoma to nab-paclitaxel (125 mg/m2) + gemcitabine (1,000 mg/m(2)) or gemcitabine alone to one 30-40 infusion on days 1, 8, and 15 of six 28 -day cycles. The primary end point was independently assessed disease -free survival (DFS). Additional end points included investigator-assessed DFS, overall survival (OS), and safety. RESULTS: Two hundred eighty-seven of 432 patients and 310 of 434 patients completed nabpaclitaxel + gemcitabine and gemcitabine treatment, respectively. At primary data cutoff (December 31, 2018; median follow-up, 38.5 [interquartile range [IQR], 33.8-43 months), the median independently assessed DFS was 19.4 (nab-paclitaxel + gemcitabine) versus 18.8 months (gemcitabine; hazard ratio [HR], 0.88; 95% CI, 0.729 to 1.063; P =.18). The median investigator-assessed DFS was 16.6 (IQR, 8.4-47.0) and 13.7 (IQR, 8.3-44.1) months, respectively (HR, 0.82; 95% CI, 0.694 to 0.965; P=.02). The median OS (427 events; 68% mature) was 40.5 (IQR, 20.7 to not reached) and 36.2 (IQR, 17.7-53.3) months, respectively (HR, 0.82; 95% CI, 0.680 to 0.996; P =.045). At a 16 -month follow-up (cutoff, April 3, 2020; median follow-up, 51.4 months [IQR, 47.0-57.0]), the median OS (511 events; 81% mature) was 41.8 (nab-paclitaxel + gemcitabine) versus 37.7 months (gemcitabine; HR, 0.82; 95% CI, 0.687 to 0.973; P =.0232). At the 5 -year follow-up (cutoff, April 9, 2021; median follow-up, 63.2 months [IQR, 60.1-68.7]), the median OS (555 events; 88% mature) was 41.8 versus 37.7 months, respectively (HR, 0.80; 95% CI, 0.678 to 0.947; P =.0091). Eighty-six percent (nab-paclitaxel + gemcitabine) and 68% (gemcitabine) of patients experienced grade >= 3 treatment -emergent adverse events. Two patients per study arm died of treatment -emergent adverse events. CONCLUSION: The primary end point (independently assessed DFS) was not met despite favorable OS seen with nab-paclitaxel + gemcitabine

The Changing Landscape for Stroke\ua0Prevention in AF: Findings From the GLORIA-AF Registry Phase 2

Background GLORIA-AF (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients with Atrial Fibrillation) is a prospective, global registry program describing antithrombotic treatment patterns in patients with newly diagnosed nonvalvular atrial fibrillation at risk of stroke. Phase 2 began when dabigatran, the first non\u2013vitamin K antagonist oral anticoagulant (NOAC), became available. Objectives This study sought to describe phase 2 baseline data and compare these with the pre-NOAC era collected during phase 1. Methods During phase 2, 15,641 consenting patients were enrolled (November 2011 to December 2014); 15,092 were eligible. This pre-specified cross-sectional analysis describes eligible patients\u2019 baseline characteristics. Atrial fibrillation disease characteristics, medical outcomes, and concomitant diseases and medications were collected. Data were analyzed using descriptive statistics. Results Of the total patients, 45.5% were female; median age was 71 (interquartile range: 64, 78) years. Patients were from Europe (47.1%), North America (22.5%), Asia (20.3%), Latin America (6.0%), and the Middle East/Africa (4.0%). Most had high stroke risk (CHA2DS2-VASc [Congestive heart failure, Hypertension, Age  6575 years, Diabetes mellitus, previous Stroke, Vascular disease, Age 65 to 74 years, Sex category] score  652; 86.1%); 13.9% had moderate risk (CHA2DS2-VASc = 1). Overall, 79.9% received oral anticoagulants, of whom 47.6% received NOAC and 32.3% vitamin K antagonists (VKA); 12.1% received antiplatelet agents; 7.8% received no antithrombotic treatment. For comparison, the proportion of phase 1 patients (of N = 1,063 all eligible) prescribed VKA was 32.8%, acetylsalicylic acid 41.7%, and no therapy 20.2%. In Europe in phase 2, treatment with NOAC was more common than VKA (52.3% and 37.8%, respectively); 6.0% of patients received antiplatelet treatment; and 3.8% received no antithrombotic treatment. In North America, 52.1%, 26.2%, and 14.0% of patients received NOAC, VKA, and antiplatelet drugs, respectively; 7.5% received no antithrombotic treatment. NOAC use was less common in Asia (27.7%), where 27.5% of patients received VKA, 25.0% antiplatelet drugs, and 19.8% no antithrombotic treatment. Conclusions The baseline data from GLORIA-AF phase 2 demonstrate that in newly diagnosed nonvalvular atrial fibrillation patients, NOAC have been highly adopted into practice, becoming more frequently prescribed than VKA in Europe and North America. Worldwide, however, a large proportion of patients remain undertreated, particularly in Asia and North America. (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients With Atrial Fibrillation [GLORIA-AF]; NCT01468701

Relationships between the decomposition behaviour of renewable fibres and their reinforcing effect in composites processed at high temperatures

Engineering polymers reinforced with renewable fibres (RF) are an attractive class of materials, due to their excellent mechanical performance and low environmental impact. However, the successful preparation of such composites has proven to be challenging due to the low thermal stability of RF. The aim of the present study was to investigate how different RF behaves under increased processing temperatures and correlate the thermal properties of the fibres to the mechanical properties of composites. For this purpose, hemp, flax and Lyocell fibres were compounded into polypropylene (PP) using a co-rotating twin screw extruder and test specimens were injection moulded at temperatures ranging from 180 °C to 260 °C, with 20 K steps. The decomposition behaviour of fibres was characterised using non-isothermal and isothermal simultaneous thermogravimetric analysis/differential scanning calorimetry (TGA/DSC). The prepared composites were investigated using optical microscopy (OM), colorimetry, tensile test, Charpy impact test, dynamic mechanical analysis (DMA) and melt flow rate (MFR). Composites exhibited a decrease in mechanical performance at processing temperatures above 200 °C, with a steep decrease observed at 240 °C. Lyocell fibres exhibited the best reinforcement effect, especially at elevated processing temperatures, followed by flax and hemp fibres. It was found that the retention of the fibre reinforcement effect at elevated temperatures can be well predicted using isothermal TGA measurements