Fracture Characterization of Rolled Sheet Alloys in Shear Loading: Studies of Specimen Geometry, Anisotropy, and Rate Sensitivity

The final publication is available at Springer via http://dx.doi.org/10.1007/s11340-016-0211-9Two different shear sample geometries were employed to investigate the failure behaviour of two automotive alloy rolled sheets; a highly anisotropic magnesium alloy (ZEK100) and a relatively isotropic dual phase steel (DP780) at room temperature. The performance of the butterfly type specimen (Mohr and Henn Exp Mech 47:805–820, 16; Dunand and Mohr Eng Fract Mech 78:2919-2934, 17) was evaluated at quasi-static conditions along with that of the shear geometry of Peirs et al Exp Mech 52:729-741, (27) using in situ digital image correlation (DIC) strain measurement techniques. It was shown that both test geometries resulted in similar strain-paths; however, the fracture strains obtained using the butterfly specimen were lower for both alloys. It is demonstrated that ZEK100 exhibits strong anisotropy in terms of failure strain. In addition, the strain rate sensitivity of fracture for ZEK100 was studied in shear tests with strain rates from quasi-static (0.01 s−1) to elevated strain rates of 10 and 100 s−1, for which a reduction in fracture strain was observed with increasing strain rate.Cosma International, Automotive Partnership CanadaOntario Research FundNatural Sciences and Engineering Research Council of CanadaCanada Research Chairs SecretariatCanada Foundation for Innovatio

Evaluation of the middle ear in water buffaloes (Bubalus bubalis) by gross anatomy and cone-beam computed tomography

Background: The purpose of this study was to provide a description of gross middle ear morphology in water buffaloes, augmented with additional data on the osseous structures of middle ear derived from cone-beam computed tomography (CBCT). Materials and methods: Skulls of 10 young adult male water buffaloes were used to examine their middle ears. Results: Anatomical features noted included the presence of tympanic cells in the tympanic bulla, the location of malleus head and neck, and all of incus in the dorsal epitympanic recess, the oval tympanic membrane, absence of a prominent notch on the articular surface of malleus, positional variations of the lateral process of malleus relative to the muscular process and muscular process relative to the rostral process of malleus, absence of complete coverage of the articular facet of malleus head by incus body, and presence of the lenticular process of incus. In CBCT images, the osseous part of external acoustic meatus, the petrous part of temporal bone and the details of the ossicles were seen, except for stapes. Conclusions: Although tympanic membrane, malleus and stapes of water buffaloes are similar to those of ox, the incus of water buffaloes is more similar to that of goats. The heaviest ossicles among the ruminants studied belonged to water buffaloes; the mean length of malleus head and neck, total length and width of incus body as well as length of stapes head were greatest in water buffaloes too. The auditory ossicles of water buffaloes show ‘transitional type’ morphological characteristics. These features suggest a relatively wide frequency range of hearing, but not one biased towards especially low or especially high frequencies

Experimental fracture characterisation of an anisotropic magnesium alloy sheet in proportional and non-proportional loading conditions

The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.ijsolstr.2018.04.010. © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/A comprehensive experimental investigation was performed to characterize the fracture behaviour of a rare-earth magnesium alloy sheet, ZEK100-O, under both proportional and non-proportional loading conditions. This material possesses severe plastic anisotropy and tension-compression asymmetry that evolve with plastic deformation and is an excellent candidate to experimentally evaluate phenomenological fracture modelling strategies. Different types of specimen geometries were fabricated in different orientations with respect to the rolling direction of the sheet to reveal the anisotropic fracture response of the alloy. Moreover, three different types of plane-strain tension tests, namely, v-bend, butterfly, and Nakazima dome tests were conducted and compared in terms of their applicability for fracture characterization of sheet materials. To visualize directional dependency of the fracture response of the magnesium alloy, experimental fracture loci for different orientations were constructed. Furthermore, non-proportional tests were performed in which abrupt changes in stress state were imposed to study the role of the loading history on fracture behaviour of the alloy. The non-proportional tests entailed pre-straining the material in uniaxial and equi-biaxial tension up to a prescribed plastic work level, followed by extreme strain path changes to plane-strain tension and shear states. Non-proportional deformations with such severe strain path variations have not been reported in the literature for materials with complex anisotropic behaviour such as ZEK100-O. The results of which have enabled the direct experimental evaluation of phenomenological damage models without performing an inverse calibration from finite element simulations. Based on the results of the non-proportional tests, it was shown that simple damage indicators were unable to describe the influence of severe changes in the strain path on fracture.Cosma InternationalAutomotive Partnership CanadaOntario Research FundNatural Sciences and Engineering Research Council of CanadaCanada Research Chairs SecretariatCanada Foundation for Innovatio

In vitro intracellular trafficking of biodegradable nanoparticles dextran spermine in cancer cell lines.

The objective of the present study is to evaluate the effect of cationic dextran on the proliferation rate and biosynthetic activities of HT29, a human colonic adenocarcinoma, and MCF7, a human breast cancer cell line. Cationic dextran was prepared by means of reductive-amination between oxidised dextran and the natural oligoamine, spermine. Biological evaluations including cell proliferation assay, and cell cycle were studied. Flow cytometery was performed in order to determine the biological behaviour of cationic dextran after internalised into the cells. Our results clearly indicated that the cationic dextran was not toxic to the cells when the concentration was 5 μg/ml or lower. The results of the cell cycle flow cytometery indicated that the means of R2 in HT29, MCF7 and HeLa cells were less than 5 three days after treatment with 5 μg/ml of cationic dextran. We conclude that the toxicity of cationic dextran is dose dependent and it is not toxic at concentration lower than 5 μg/ml, and tolerable by the cells, and it can be used as a tool for gene delivery

Evaluation and calibration of anisotropic yield criteria in shear Loading: Constraints to eliminate numerical artefacts

The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.ijsolstr.2017.06.029 © 2017. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Many anisotropic phenomenological yield functions have been proposed in the literature in which their predictive capabilities strongly depend on the experimental calibration data as well as the calibration procedure to identify the anisotropy parameters. In this paper, emphasis is placed upon the experimental and numerical calibration procedure of anisotropic yield functions in the region of shear loading (zero hydrostatic stress with equal and opposite in-plane principal strains and stresses). Conventional anisotropic calibration procedures are shown to introduce non-physical artefacts into constitutive models which manifest as a non-zero hydrostatic stress or through-thickness strains generated under in-plane shear stress that violate the definition of the shear loading condition. To overcome this issue, a new physically necessary constraint is applied on the plastic potential to enforce equal and opposite principal strains in the shear state and correct the shear region of anisotropic yield functions. Using this necessary constraint, the widely used Yld2000-2d anisotropic yield function was calibrated using an associated flow rule for aluminum alloy sheet using published data for AA2090-T3 to demonstrate how enforcing this constraint can be readily implemented to correct the shear region of the anisotropic yield surface. Furthermore, to investigate the influence of the shear constraint, an AA7075-T6 alloy was experimentally characterized in uniaxial tension, equal-biaxial tension and shear. It was revealed that with the additional shear constraints, non-physical artefacts of plane-stress anisotropic yield functions such as Yld2000-2d can be removed during the calibration procedure. However, due to the additional shear constraints, available anisotropic models may become over-constrained and alternate yield functions with more flexibility or non-associated flow rules may be required.Honda R&D AmericasCosma InternationalAlcoa Technical CenterAutomotive Partnership CanadaOntario Research FundNatural Sciences and Engineering Research Council of CanadaCanada Research Chairs SecretariatCanada Foundation for Innovatio

Constitutive characterization of a rare-earth magnesium alloy sheet (ZEK100-O) in shear loading: Studies of anisotropy and rate sensitivity

The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.ijmecsci.2017.04.013 © 2017. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Rare-earth magnesium alloys such as ZEK100-O offer improved ductility over other conventional magnesium alloys at room temperature; however, they exhibit significant anisotropy and complex yield behaviour. In this work, a systematic investigation of anisotropy of ZEK100-O rolled sheet in shear loading was conducted at room temperature under quasi-static conditions, as the shear deformation of these alloys is not well understood. Furthermore, uniaxial tensile and compressive characterization of the material was performed to provide context for its behaviour under shear loading. It was revealed that ZEK100-O exhibits strong anisotropy in shear which is markedly different than tensile anisotropy with unique trends that suggest the activation of different deformation mechanisms. To characterize shear anisotropy in HCP materials such as ZEK100-O, the shear response of the material should be investigated in three orientations of 0° (or 90°), 45°, and 135° with respect to the rolling direction. The selection and analysis of these directions is discussed in terms of the principal stress directions and activation of different deformations mechanisms. In order to further investigate this behaviour, the microstructure of the deformed specimens was studied using Electron Backscattered Diffraction (EBSD) analysis to quantify the active twinning systems in different test orientations. Moreover, the CPB06 yield criterion with two linear transformations was calibrated with experimental data to describe the complex anisotropic behaviour of ZEK100-O. It was established that the material exhibits asymmetry not only in tension-compression regions represented by the 1st and 3rd quadrants of yield locus but also in shear regions represented by the 2nd and 4th quadrants. Finally, the strain rate sensitivity of ZEK100-O was studied in shear tests at elevated strain rates of 10s−1 and 100s−1, at which positive rate sensitivity was observed.Cosma International/Automotive Partnership Canada/Natural Sciences and Engineering Research Council of Canada [APCPJ 417811-11]Ontario Research Fund [RE01-054]Canada Research Chairs Secretariat [950-220425]Canada Foundation for Innovation (30337

Automated measurement of net water uptake from baseline and follow-up CTs in patients with large vessel occlusion stroke

Quantifying the extent and evolution of cerebral edema developing after stroke is an important but challenging goal. Lesional net water uptake (NWU) is a promising CT-based biomarker of edema, but its measurement requires manually delineating infarcted tissue and mirrored regions in the contralateral hemisphere. We implement an imaging pipeline capable of automatically segmenting the infarct region and calculating NWU from both baseline and follow-up CTs of large-vessel occlusion (LVO) patients. Infarct core is extracted from CT perfusion images using a deconvolution algorithm while infarcts on follow-up CTs were segmented from non-contrast CT (NCCT) using a deep-learning algorithm. These infarct masks were flipped along the brain midline to generate mirrored regions in the contralateral hemisphere of NCCT; NWU was calculated as one minus the ratio of densities between regions, removing voxels segmented as CSF and with HU outside thresholds of 20-80 (normal hemisphere and baseline CT) and 0-40 (infarct region on follow-up). Automated results were compared with those obtained using manually-drawn infarcts and an ASPECTS region-of-interest based method that samples densities within the infarct and normal hemisphere, using intraclass correlation coefficient (ρ). This was tested on serial CTs from 55 patients with anterior circulation LVO (including 66 follow-up CTs). Baseline NWU using automated core was 4.3% (IQR 2.6-7.3) and correlated with manual measurement (ρ = 0.80

Time-resolved studies define the nature of toxic IAPP intermediates, providing insight for anti-amyloidosis therapeutics

Islet amyloidosis by IAPP contributes to pancreatic β-cell death in diabetes, but the nature of toxic IAPP species remains elusive. Using concurrent time-resolved biophysical and biological measurements, we define the toxic species produced during IAPP amyloid formation and link their properties to induction of rat INS-1 β-cell and murine islet toxicity. These globally flexible, low order oligomers upregulate pro-inflammatory markers and induce reactive oxygen species. They do not bind 1-anilnonaphthalene-8-sulphonic acid and lack extensive β-sheet structure. Aromatic interactions modulate, but are not required for toxicity. Not all IAPP oligomers are toxic; toxicity depends on their partially structured conformational states. Some anti-amyloid agents paradoxically prolong cytotoxicity by prolonging the lifetime of the toxic species. The data highlight the distinguishing properties of toxic IAPP oligomers and the common features that they share with toxic species reported for other amyloidogenic polypeptides, providing information for rational drug design to treat IAPP induced β-cell death

Ecological study on the Persian Gulf Martyres Lake, Tehran

The ecological study of the Persian Gulf Martyres Lake carried out at the 5 stations between 2013 and 2014. This study identified 35 phytoplankton taxa. The diatoms taxa was dominated and their abundance recorded highest (2000 000 cell. L^-1) in the lake. The annual phytoplankton abundance was measured as 2500 000 cell. L^-1 during the study. The total nitrogen and water temperature were the significant a biotic parameters to increase cyanophytes abundance. Furthermore, 37 zooplankton taxa were identified. The Rotatoria abundance was dominated zooplankton. The annual zooplankton abundance was measured as 72 ind.l-1. Based on the CCA, there was no correlation between Rotatoria abundance and a biotic parameters. The study benthos showed Ephemeroptera and Diptera abundance were dominated; artificial bottom and lack of sediment and organic matters were the main reasons in decreasing of the benthos density. The Chitgar lake is the poorest lake in Iran due to low density of plankton and benthos organisms. The estimation of fish production was 123 kg/ha and for the lake was determaind 16 tonne. The finding display, invasive species was the main fish Chitgar lake that would be negative effect and increase eutriphication trend in the lake. Phosphorus parameter was limited parameters and trophy level recorded low due to high N/P ration in the lake. In overall the Chitgar lake situation is in Oligotrophic category with the low trophy level