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  • 1
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    Galanin neurons in the medial preoptic area govern parental behaviour (2014)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2014-05-16
    Description: Mice display robust, stereotyped behaviours towards pups: virgin males typically attack pups, whereas virgin females and sexually experienced males and females display parental care. Here we show that virgin males genetically impaired in vomeronasal sensing do not attack pups and are parental. Furthermore, we uncover a subset of galanin-expressing neurons in the medial preoptic area (MPOA) that are specifically activated during male and female parenting, and a different subpopulation that is activated during mating. Genetic ablation of MPOA galanin neurons results in marked impairment of parental responses in males and females and affects male mating. Optogenetic activation of these neurons in virgin males suppresses inter-male and pup-directed aggression and induces pup grooming. Thus, MPOA galanin neurons emerge as an essential regulatory node of male and female parenting behaviour and other social responses. These results provide an entry point to a circuit-level dissection of parental behaviour and its modulation by social experience.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4105201/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4105201/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wu, Zheng -- Autry, Anita E -- Bergan, Joseph F -- Watabe-Uchida, Mitsuko -- Dulac, Catherine G -- F32 DC010089/DC/NIDCD NIH HHS/ -- R01 DC003903/DC/NIDCD NIH HHS/ -- R01 DC009019/DC/NIDCD NIH HHS/ -- R01 DC013087/DC/NIDCD NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2014 May 15;509(7500):325-30. doi: 10.1038/nature13307.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, Department of Molecular and Cellular Biology, Center for Brain Science, Harvard University, Cambridge, Massachusetts 02138, USA. ; Department of Molecular and Cellular Biology, Center for Brain Science, Harvard University, Cambridge, Massachusetts 02138, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24828191" target="_blank"〉PubMed〈/a〉
    Keywords: Aggression/physiology ; Animals ; Copulation ; Female ; Galanin/deficiency/genetics/*metabolism ; Grooming/physiology ; Male ; Maternal Behavior/*physiology ; Mice ; Neurons/*metabolism ; Optogenetics ; Paternal Behavior/*physiology ; Pheromones/analysis ; Preoptic Area/*cytology/metabolism ; TRPC Cation Channels/deficiency/genetics ; Vomeronasal Organ/physiology
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 2
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    Development of a Mesoscale Finite Element Constitutive Model for Fiber Kinking (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: A mesoscale finite element material model is proposed to analyze structures that fail by the fiber kinking damage mode. To evaluate the assumptions of the mesoscale model, the results were compared with those of a high-fidelity micromechanical model. A direct comparison between the two models shows remarkable correlation, indicating that the key features of the fiber kinking phenomenon are appropriately accounted for in the mesoscale model. The mesoscale model is applied to structural analysis cases to demonstrate the capabilities of the model. A verification study is conducted with an unnotched compression specimen and preliminary validation is demonstrated with a notched compression specimen. The results show that the model is successful at representing the kinematics of fiber kinking while at the same time highlighting the need for further verification and validation.
    Keywords: Composite Materials
    Type: NF1676L-27418 , AIAA SciTech 2018; Jan 08, 2018 - Jan 12, 2018; Kissimmee, FL; United States
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  • 3
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    Mode I Cohesive Law Characterization of Through-Crack Propagation in a Multidirectional Laminate (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A method is proposed and assessed for the experimental characterization of through-the-thickness crack propagation in multidirectional composite laminates with a cohesive law. The fracture toughness and crack opening displacement are measured and used to determine a cohesive law. Two methods of computing fracture toughness are assessed and compared. While previously proposed cohesive characterizations based on the R-curve exhibit size effects, the proposed approach results in a cohesive law that is a material property. The compact tension specimen configuration is used to propagate damage while load and full-field displacements are recorded. These measurements are used to compute the fracture toughness and crack opening displacement from which the cohesive law is characterized. The experimental results show that a steady-state fracture toughness is not reached. However, the proposed method extrapolates to steady-state and is demonstrated capable of predicting the structural behavior of geometrically-scaled specimens.
    Keywords: Composite Materials
    Type: NF1676L-18222 , US-Japan Conference on Composite Materials; Sep 08, 2014 - Sep 10, 2014; La Jolla, CA; United States|ASTM-D30 Meeting; Sep 08, 2014 - Sep 10, 2014; La Jolla, CA; United States|American Society for Composites Technical Conference; Sep 08, 2014 - Sep 10, 2014; La Jolla, CA; United States
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  • 4
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    In-Situ Observations of Longitudinal Compression Damage in Carbon-Epoxy Cross Ply Laminates Using Fast Synchrotron Radiation Computed Tomography (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The role of longitudinal compressive failure mechanisms in notched cross-ply laminates is studied experimentally with in-situ synchrotron radiation based computed tomography. Carbon/epoxy specimens loaded monotonically in uniaxial compression exhibited a quasi-stable failure process, which was captured with computed tomography scans recorded continuously with a temporal resolutions of 2.4 seconds and a spatial resolution of 1.1 microns per voxel. A detailed chronology of the initiation and propagation of longitudinal matrix splitting cracks, in-plane and out-of-plane kink bands, shear-driven fiber failure, delamination, and transverse matrix cracks is provided with a focus on kink bands as the dominant failure mechanism. An automatic segmentation procedure is developed to identify the boundary surfaces of a kink band. The segmentation procedure enables 3-dimensional visualization of the kink band and conveys the orientation, inclination, and spatial variation of the kink band. The kink band inclination and length are examined using the segmented data revealing tunneling and spatial variations not apparent from studying the 2-dimensional section data.
    Keywords: Composite Materials
    Type: ASC Paper-49 , NF1676L-26427 , American Society for Testing and Materials (ASTM) D30 Meeting; Oct 23, 2017 - Oct 25, 2017; West Lafayette, IN; United States|American Society for Composites Technical Conference; Oct 23, 2017 - Oct 25, 2017; West Lafayette, IN; United States
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  • 5
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    Implementation of a Matrix Crack Spacing Parameter in a Continuum Damage Mechanics Finite Element Model (2018)
    In:  CASI
    Details
    Publication Date: 2020-01-08
    Description: Continuum Damage Mechanics (CDM) based progressive damage and failure analysis (PDFA) methods have demonstrated success in a variety of finite element analysis (FEA) implementations. However, the technical maturity of CDM codes has not yet been proven for the full design space of composite materials in aerospace applications. CDM-based approaches represent the presence of damage by changing the local material stiffness definitions and without updating the original mesh or element integration schemes. Without discretely representing cracks and their paths through the mesh, damage in models with CDM-based materials is often distributed in a region of partially damaged elements ahead of stress concentrations. Having a series of discrete matrix cracks represented by a softened region may affect predictions of damage propagation and, thus, structural failure. This issue can be mitigated by restricting matrix damage development to discrete, fiber-aligned rows of elements; hence CDM-based matrix cracks can be implemented to be more representative of discrete matrix cracks. This paper evaluates the effect of restricting CDM matrix crack development to discrete, fiber-aligned rows where the spacing of these rows is controlled by a user-defined crack spacing parameter. Initially, the effect of incrementally increasing matrix crack spacing in a unidirectional center notch coupon is evaluated. Then, the lessons learned from the center notch specimen are applied to open-hole compression finite element models. Results are compared to test data, and the limitations, successes, and potential of the matrix crack spacing approach are discussed.
    Keywords: Composite Materials
    Type: NF1676L-31287 , American Society for Composites (ASC) Annual Technical Conference; Sep 24, 2018 - Sep 26, 2018; Seattle, WA; United States|US-Japan Conference on Composite Materials; Sep 24, 2018 - Sep 26, 2018; Seattle, WA; United States|Proceedings of the American Society for Composites; 1500
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  • 6
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    Cohesive Laws for Analyzing Through-Crack Propagation in Cross Ply Laminates (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The laminate cohesive approach (LCA) is a methodology for the experimental characterization of cohesive through-the-thickness damage propagation in fiber-reinforced polymer matrix composites. LCA has several advantages over other existing approaches for cohesive law characterization, including: visual measurements of crack length are not required, structural effects are accounted for, and LCA can be applied when the specimen is too small to achieve steady-state fracture. In this work, the applicability of this method is investigated for two material systems: IM7/8552, a conventional prepreg, and AS4/VRM34, a non-crimp fabric cured using an out-of-autoclave process. The compact tension specimen configuration is used to propagate stable Mode I damage. Trilinear cohesive laws are characterized using the fracture toughness and the notch tip opening displacement. Test results are compared for the IM7/8552 specimens with notches machined by waterjet and by wire slurry saw. It is shown that the test results are nearly identical for both notch tip preparations methods, indicating that significant specimen preparation time and cost savings can be realized by using the waterjet to notch the specimen instead of the wire slurry saw. The accuracy of the cohesive laws characterized herein are assessed by reproducing the structural response of the test specimens using computational methods. The applicability of the characterization procedure for inferring lamina fracture toughness is also discussed.
    Keywords: Composite Materials
    Type: NF1676L-20373 , International Conference on Composite Materials (ICCM20); Jul 19, 2015 - Jul 24, 2015; Copenhagen; Denmark
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  • 7
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    A Continuum Damage Mechanics Model to Predict Kink-Band Propagation Using Deformation Gradient Tensor Decomposition (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A new model is proposed that represents the kinematics of kink-band formation and propagation within the framework of a mesoscale continuum damage mechanics (CDM) model. The model uses the recently proposed deformation gradient decomposition approach to represent a kink band as a displacement jump via a cohesive interface that is embedded in an elastic bulk material. The model is capable of representing the combination of matrix failure in the frame of a misaligned fiber and instability due to shear nonlinearity. In contrast to conventional linear or bilinear strain softening laws used in most mesoscale CDM models for longitudinal compression, the constitutive response of the proposed model includes features predicted by detailed micromechanical models. These features include: 1) the rotational kinematics of the kink band, 2) an instability when the peak load is reached, and 3) a nonzero plateau stress under large strains.
    Keywords: Composite Materials
    Type: Paper No. 106 , NF1676L-23490 , American Society for Composites Technical Conference; Sep 19, 2016 - Sep 22, 2016; Williamsburg, VA; United States
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  • 8
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    Modeling Fiber Kinking at the Microscale and Mesoscale (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A computational micromechanics (CMM) model is employed to interrogate the assumptions of a recently developed mesoscale continuum damage mechanics (CDM) model for fiber kinking. The CMM model considers an individually discretized three dimensional fiber and surrounding matrix accounting for nonlinearity in the fiber, matrix plasticity, fiber/matrix interface debonding, and geometric nonlinearity. Key parameters of the CMM model were measured through experiments. In particular, a novel experimental technique to characterize the in situ longitudinal compressive strength of carbon fibers through indentation of micropillars is presented. The CDM model is formulated on the basis of Budiansky's fiber kinking theory (FKT) with a constitutive deformation-decomposition approach to alleviate mesh size sensitivity. In contrast to conventional mesoscale CDM models that prescribe a constitutive response directly, the response of the proposed model is an outcome of material nonlinearity and large rotations of the fiber direction following FKT. Comparison of the predictions from the CMM and CDM models shows remarkable correlation in strength, post-peak residual stress, and fiber rotation, with less than 10% difference between the two models in most cases. Additional comparisons are made with several fiber kinking models proposed in the literature to highlight the efficacy of the two models. Finally, the CMM model is exercised in parametric studies to explore opportunities to improve the longitudinal compression strength of a ply through the use of nonconventional microstructures.
    Keywords: Composite Materials
    Type: NF1676L-31270 , NASA/TP-2018-220105 , L-20964
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  • 9
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    Multiscale Fiber Kinking: Computational Micromechanics and a Mesoscale Continuum Damage Mechanics Models (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In this work, the fiber kinking phenomenon, which is known as the failure mechanism that takes place when a fiber reinforced polymer is loaded under longitudinal compression, is studied. A computational micromechanics model is employed to interrogate the assumptions of a recently developed mesoscale continuum damage mechanics (CDM) model for fiber kinking based on the deformation gradient decomposition (DGD) and the LaRC04 failure criteria.
    Keywords: Composite Materials
    Type: NF1676L-27598 , ECCOMAS Thematic Conference on the Mechanical Response of Composites; Sep 20, 2017 - Sep 22, 2017; Eindhoven; Netherlands
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