Investigating the micromechanisms of mode II delamination in composite laminates

The use of composite materials in primary aerospace structures is continually increasing due to their high stiffness and high strength to weight ratios. However, composite laminates are susceptible to delamination which can lead to the loss of global stiffness and potentially to catastrophic failure. Delamination is therefore a critical damage mechanism to account for when determining the durability and damage tolerance of composite materials. A large amount of research has already been carried out to investigate delamination and a number of failure criteria have been developed to predict delamination growth. However, the majority of these criteria are not based on the physical mechanisms that cause interlaminar fracture. Thus to be able to confidently predict delamination growth in real world applications a physically based failure criteria would be more appropriate. The key to developing physically based criteria is through fractographic observations to determine the dominant failure mechanisms of delamination. Thus the purpose of this research was to characterise the failure process of mode II shear fracture, and in particular to determine the formation of cusp features prevalent to mode II dominated fracture. A polyvinylchloride foam was used to macro-simulate mode II interlaminar failure of composite laminates. The in-situ fracture process was characterised successfully and the energy absorbed during cusp formation was determined. Results were compared with cusp formation in two carbon-fibre/epoxy laminates and the post fracture morphology of all the materials was similar. In addition the influence of parameters such as, material type, inter-fibre spacing, fibre diameter and ply orientation on the frequency, morphology and size of cusp formation were also investigated. Results indicated that cusp formation was via the initiation, saturation and propagation of tensile microcracks and that neither the cusp formation process nor the energy associated with crack formation was found to be influenced by the parameters studied

miR-196b target screen reveals mechanisms maintaining leukemia stemness with therapeutic potential.

We have shown that antagomiR inhibition of miRNA miR-21 and miR-196b activity is sufficient to ablate MLL-AF9 leukemia stem cells (LSC) in vivo. Here, we used an shRNA screening approach to mimic miRNA activity on experimentally verified miR-196b targets to identify functionally important and therapeutically relevant pathways downstream of oncogenic miRNA in MLL-r AML. We found Cdkn1b (p27Kip1) is a direct miR-196b target whose repression enhanced an embryonic stem cell–like signature associated with decreased leukemia latency and increased numbers of leukemia stem cells in vivo. Conversely, elevation of p27Kip1 significantly reduced MLL-r leukemia self-renewal, promoted monocytic differentiation of leukemic blasts, and induced cell death. Antagonism of miR-196b activity or pharmacologic inhibition of the Cks1-Skp2–containing SCF E3-ubiquitin ligase complex increased p27Kip1 and inhibited human AML growth. This work illustrates that understanding oncogenic miRNA target pathways can identify actionable targets in leukemia

Remembering Dr. Linda Most

Featured article collecting tributes to Dr. Linda Most, who passed away in December 2024. Dr. Most was an associate professor and the former head of the Valdosta State University MLIS program, longtime chair of the Georgia State Board for the Certification of Librarians, and a trustee for the South Georgia Regional Library

Teaching Government Information in Information Literacy Credit Classes

This paper reviews the teaching of credit-bearing information literacy courses and government information, reports questionnaire responses from librarians who teach these courses, and argues that revising the ways we teach government information in for-credit courses will help students achieve information literacy. A focus on government information as critical thinking and subject access resources, rather than as unique documents collections or formats, can remove barriers for researchers, particularly in classes that allow students an entire term to develop skills. In addition, librarians will increase their comfort levels addressing government information and develop ways to teach students to use these resources within a meaningful context for their research. The ability to find, evaluate, and effectively use government information resources will empower students to become lifelong learners, seekers, and even engaged citizens, whatever their post-graduation information needs may be

Before I Was a Library Worker: Past Lives

Responses include as contributors Jeff Fisher, Amy Shaw, Jonathan Harwell, Kristy Greene, Tera Ray, Linda Bridges, Wendy Wilmoth, Nancy Shore, Allison Robinson, Rachel Schrauben Yeates, Stephanie Burnham, Rebecca Ballard, Aspasia Luster, Sarah Trowbridge, Willis Smith, Anna Cogdill, Richard Coleman, Ben Bryson, Tonya Aumack, Bel Outwater, Lisa Mosley, Szilvia Somodi, Sara Whitaker, Laura Carscaddon, Kevin Reagan, Bridget Smit

Sharing Our Library Workspaces

This article about library workspaces features photo contributions and descriptions from Joy Bolt, Raymond Goslow, Elizabeth McKinney, Angela E. Megaw, and Rachel Zion