Modal nudging in nonlinear elasticity: tailoring the elastic post-buckling behaviour of engineering structures

The buckling and post-buckling behaviour of slender structures is increasingly being harnessed for smart functionalities. Equally, the post-buckling regime of many traditional engineering structures is not being used for design and may therefore harbour latent load-bearing capacity for further structural efficiency. Both applications can benefit from a robust means of modifying and controlling the post-buckling behaviour for a specific purpose. To this end, we introduce a structural design paradigm termed modal nudging, which can be used to tailor the post-buckling response of slender engineering structures without any significant increase in mass. Modal nudging uses deformation modes of stable post-buckled equilibria to perturb the undeformed baseline geometry of the structure imperceptibly, thereby favouring the seeded post-buckling response over potential alternatives. The benefits of this technique are enhanced control over the post-buckling behaviour, such as modal differentiation for smart structures that use snap-buckling for shape adaptation, or alternatively, increased load-carrying capacity, increased compliance or a shift from imperfection sensitivity to imperfection insensitivity. Although these concepts are, in theory, of general applicability, we concentrate here on planar frame structures analysed using the nonlinear finite element method and numerical continuation procedures. Using these computational techniques, we show that planar frame structures may exhibit isolated regions of stable equilibria in otherwise unstable post-buckling regimes, or indeed stable equilibria entirely disconnected from the natural structural response. In both cases, the load-carrying capacity of these isolated stable equilibria is greater than the natural structural response of the frames. Using the concept of modal nudging it is possible to “nudge” the frames onto these equilibrium paths of greater load-carrying capacity. Due to the scale invariance of modal nudging, these findings may impact the design of structures from the micro- to the macro-scale

Thermal and mechanical properties of chitosan nanocomposites with cellulose modified in ionic liquids

In this paper, ionic liquid treatment was applied to produce nanometric cellulose particles of two polymorphic forms. A complex characterization of nanofillers including wide-angle X-ray scattering, Fourier transform infrared spectroscopy, and particle size determination was performed. The evaluated ionic liquid treatment was effective in terms of nanocrystalline cellulose production, leaving chemical and supermolecular structure of the materials intact. However, nanocrystalline cellulose II was found to be more prone to ionic liquid hydrolysis leading to formation larger amount of small particles. Each nanocrystalline cellulose was subsequently mixed with a solution of chitosan, so that composite films containing 1, 3, and 5% mass/mass of nanometric filler were obtained. Reference samples of chitosan and chitosan with micrometric celluloses were also solvent casted. Thermal, mechanical, and morphological properties of films were tested and correlated with properties of filler used. The results of both, tensile tests and thermogravimetric analysis showed a significant discrepancy between composites filled with nanocrystalline cellulose I and nanocrystalline cellulose II

Tooling design and microwave curing technologies for the manufacturing of fiber-reinforced polymer composites in aerospace applications

The increasing demand for high-performance and quality polymer composite materials has led to international research effort on pursuing advanced tooling design and new processing technologies to satisfy the highly specialized requirements of composite components used in the aerospace industry. This paper reports the problems in the fabrication of advanced composite materials identified through literature survey, and an investigation carried out by the authors about the composite manufacturing status in China’s aerospace industry. Current tooling design technologies use tooling materials which cannot match the thermal expansion coefficient of composite parts, and hardly consider the calibration of tooling surface. Current autoclave curing technologies cannot ensure high accuracy of large composite materials because of the wide range of temperature gradients and long curing cycles. It has been identified that microwave curing has the potential to solve those problems. The proposed technologies for the manufacturing of fiber-reinforced polymer composite materials include the design of tooling using anisotropy composite materials with characteristics for compensating part deformation during forming process, and vacuum-pressure microwave curing technology. Those technologies are mainly for ensuring the high accuracy of anisotropic composite parts in aerospace applications with large size (both in length and thickness) and complex shapes. Experiments have been carried out in this on-going research project and the results have been verified with engineering applications in one of the project collaborating companies

Recent advances and perspectives on starch nanocomposites for packaging applications

Starch nanocomposites are popular and abundant materials in packaging sectors. The aim of this work is to review some of the most popular starch nanocomposite systems that have been used nowadays. Due to a wide range of applicable reinforcements, nanocomposite systems are investigated based on nanofiller type such as nanoclays, polysaccharides and carbonaceous nanofillers. Furthermore, the structures of starch and material preparation methods for their nanocomposites are also mentioned in this review. It is clearly presented that mechanical, thermal and barrier properties of plasticised starch can be improved with well-dispersed nanofillers in starch nanocomposites

Zebrafish screen identifies novel compound with selective toxicity against leukemia

To detect targeted antileukemia agents we have designed a novel, high-content in vivo screen using genetically engineered, T-cell reporting zebrafish. We exploited the developmental similarities between normal and malignant T lymphoblasts to screen a small molecule library for activity against immature T cells with a simple visual readout in zebrafish larvae. After screening 26 400 molecules, we identified Lenaldekar (LDK), a compound that eliminates immature T cells in developing zebrafish without affecting the cell cycle in other cell types. LDK is well tolerated in vertebrates and induces long-term remission in adult zebrafish with cMYC-induced T-cell acute lymphoblastic leukemia (T-ALL). LDK causes dephosphorylation of members of the PI3 kinase/AKT/mTOR pathway and delays sensitive cells in late mitosis. Among human cancers, LDK selectively affects survival of hematopoietic malignancy lines and primary leukemias, including therapy-refractory B-ALL and chronic myelogenous leukemia samples, and inhibits growth of human T-ALL xenografts. This work demonstrates the utility of our method using zebrafish for antineoplastic candidate drug identification and suggests a new approach for targeted leukemia therapy. Although our efforts focused on leukemia therapy, this screening approach has broad implications as it can be translated to other cancer types involving malignant degeneration of developmentally arrested cells

Co-infection by hepatitis C virus in human immunodeficiency virus infected patients in southwest of Iran

Background: Hepatitis C virus (HCV) has emerged as the cause of the second major epidemic of viral infection after human immunodeficiency virus (HIV) within the past two decades, and co-infection of HIV and HCV represents a growing problem for the future. The purpose of this study was to investigate the prevalence of HCV antibodies (anti-HCV) in patients with HIV in Fars province. Patients and methods: A total of 101 HIV-1-positive individuals (89 males, 12 females) from Fars province (Counseling Behavioral Modification Center in Shiraz) were included in the study. They were distributed according to risk factors for HIV infection as follows: 35(34.6%) IVDUs, 2(2%) sexual high-risk behavior, 50(49.5%) a combination of IVDUs and sexual behavior, 12(12%) from HIV positive partners and 2(2%) unknown. Detection of HCV antibodies was carried out by a third generation enzyme-linked immunosorbent assay. Results: Totally, 87 (84 males, 3 females) of 101 HIV-infected patients (86.1%) had antibodies to HCV. The prevalence of HCV antibodies was higher among the males (83.2%) than the females (3%). The prevalence of HCV antibodies was 94.4% in IVDUs, 96% in individuals with both IVDUs and sexual behavior risk factors and 25% in women who had HIV-positive partner. All unknown cases were positive for HCV and none of individuals who had sexual high-risk behavior were infected with HCV. Conclusion: The overall prevalence of HCV infection in HIV-positive individuals was 84.1%. The consistently high prevalence of HCV infection observed in HIV infected individuals supports the routine screening for HCV and continuous educational programs in these patients, especially among IVDUs in Iran. © 2010 IDTMRC, Infectious Diseases and Tropical Medicine Research Center

Enrichment of live unlabelled cardiomyocytes from heterogeneous cell populations using manipulation of cell settling velocity by magnetic field

The majority of available cardiomyocyte markers are intercellular proteins, limiting our ability to enrich live cardiomyocytes from heterogeneous cell preparations in the absence of genetic labeling. Here, we describe enrichment of live cardiomyocytes from the hearts of adult mice in a label-free microfluidic approach. The separation device consisted of a vertical column (15 mm long, 700 μm diameter), placed between permanent magnets resulting in a field strength of 1.23 T. To concentrate the field at the column wall, the column was wrapped with 69 μm diameter nickel wire. Before passing the cells through the column, the cardiomyocytes in the cell suspension had been rendered paramagnetic by treatment of the adult mouse heart cell preparation with sodium nitrite (2.5 mM) for 20 min on ice. The cell suspension was loaded into the vertical column from the top and upon settling, the non-myocytes were removed by the upward flow from the column. The cardiomyocytes were then collected from the column by applying a higher flow rate (144 μl/min). We found that by applying a separation flow rate of 4.2 μl/min in the first step, we can enrich live adult cardiomyocytes to 93% ± 2% in a label-free manner. The cardiomyocytes maintained viability immediately after separation and upon 24 h in culture. © 2013 American Institute of Physics

Anti�HER2 single domain antibody-conjugated dendrimers for targeted delivery of truncated-Bid transgene to breast cancer cells

To combine the targeted gene delivery and cell-specific transcriptional targeting, a delivery system was designed based on Generation 5 polyamidoamine dendrimer (PAMAM), poly(ethylene glycol), and anti-HER2 (human epidermal growth factor receptor 2) variable domains of camelid heavy chain antibodies (single domain antibody, VHHs). Anti-HER2 VHHs were covalently attached to the distal ends of poly(ethylene glycols) in PAMAM-poly(ethylene glycol) structure. The prepared immunotargeted nanobiopolymer was then used to condense gene construct, encoding a transcriptionally targeted truncated-Bid killer gene under the control of the breast cancer�specific MUC1 (transmembrane glycoprotein mucin 1) promoter. Transfection and transcription efficiencies of the engineered dendriplexes were quantified by truncated-Bid gene expression measurements, using real-time polymerase chain reaction. The engineered dendriplexes exhibited desirable physicochemical characteristics evaluated by dynamic light scattering and agarose gel retardation assay. Flow cytometry results showed a significantly higher uptake of VHH-modified dendriplexes than untargeted particles in HER2-positive cell lines. In vitro gene expression studies using PAMAM-poly(ethylene glycol)-VHH in complex with a luciferase expressing plasmid resulted in 1.6- and 4.8-fold higher transfection efficiencies than intact PAMAM dendrimers in BT-474 and SK-BR-3 (both as HER2-positive cell lines), respectively. Transfection by PAMAM-poly(ethylene glycol)-VHH/pMUC1-truncated-Bid also increased the level of truncated-Bid gene expression at 2.2- and 3.6-folds in BT-474 and SK-BR-3 cell lines, respectively, compared to the untargeted PAMAM treatment. A remarkable cell death was also observed in case of HER2-positive cells transfected by the targeted dendriplexes, indicating not only an effective targeted delivery but also a better transcriptional targeting efficiency of truncated-Bid killer gene, when expressed under the control of MUC1 promoter. © The Author(s) 2018