Feasibility Study of Prestressed Natural Fiber-Reinforced Polylactic Acid (PLA) Composite Materials

The feasibility of manufacturing high-performance, prestressed natural-fiber reinforced biopolymer composites is demonstrated in this work. The objective of this study was to illustrate that the specific mechanical properties of biopolymers, namely polylactic acid (PLA), can be enhanced by leveraging a combination of (a) additive manufacturing (3D printing) and (b) initial post-tensioning of continuous natural fiber reinforcement. In this study, both tensile and flexural PLA specimens of various cross-sectional geometries were 3D-printed with and without post-tensioning ducts. The mechanical properties of two continuous reinforcing fibers, jute and flax, were characterized prior to threading, post-tensioning to a prescribed level of stress, and anchoring using a mechanical loading frame. The effect of fiber type, matrix cross-sectional geometry, number of reinforcing strands, and degree of post-tensioning on the specific mechanical properties (e.g., strength-to-weight, stiffness-to-weight) of PLA were investigated using both tensile and flexural mechanical testing. Finite element models of a subgroup of the composite specimens were developed and the same experimental tests were simulated using the models. Additionally, analytical equations were derived for the prediction of composite tensile mechanical properties. Experimental results confirm that 3D-printed matrices improve the specific tensile and flexural mechanical properties of PLA composites and that these properties are further improved via initial fiber prestressing. The experimental data indicate statistically significant increases (p-value < 0.05) in specific strengths of 116% and 32% and specific stiffnesses of 62% and 29% in tension and flexure, respectively, compared to unreinforced PLA specimens. The results suggest that both additive manufacturing and fiber prestressing represent viable new methods for improving the mechanical performance of natural fiber-reinforced polymeric composites. Finite element model simulation results, as well as results from mechanics-based analytical equations, for mechanical behavior of the composite specimens aligned well with obtained data, thus further strengthening the validity of the experimental results. This study considered only mechanical behavior of natural fiber-reinforced biopolymeric composites; the need remains for future research in other aspects (e.g., long-term durability, economic constraints) in order to further demonstrate the viability of these novel composite materials for construction applications

Nucleo-cytoplasmic interactions that control nuclear envelope breakdown and entry into mitosis in the sea urchin zygote

In sea urchin zygotes and mammalian cells nuclear envelope breakdown (NEB) is not driven simply by a rise in cytoplasmic cyclin dependent kinase 1-cyclin B (Cdk1-B) activity; the checkpoint monitoring DNA synthesis can prevent NEB in the face of mitotic levels of Cdk1-B. Using sea urchin zygotes we investigated whether this checkpoint prevents NEB by restricting import of regulatory proteins into the nucleus. We find that cyclin B1-GFP accumulates in nuclei that cannot complete DNA synthesis and do not break down. Thus, this checkpoint limits NEB downstream of both the cytoplasmic activation and nuclear accumulation of Cdk1-B1. In separate experiments we fertilize sea urchin eggs with sperm whose DNA has been covalently cross-linked to inhibit replication. When the pronuclei fuse, the resulting zygote nucleus does not break down for \u3e180 minutes (equivalent to three cell cycles), even though Cdk1-B activity rises to greater than mitotic levels. If pronuclear fusion is prevented, then the female pronucleus breaks down at the normal time (average 68 minutes) and the male pronucleus with cross-linked DNA breaks down 16 minutes later. This male pronucleus has a functional checkpoint because it does not break down for \u3e120 minutes if the female pronucleus is removed just prior to NEB. These results reveal the existence of an activity released by the female pronucleus upon its breakdown, that overrides the checkpoint in the male pronucleus and induces NEB. Microinjecting wheat germ agglutinin into binucleate zygotes reveals that this activity involves molecules that must be actively translocated into the male pronucleus

Cross sectional, qualitative thematic analysis of patient perspectives of disease impact in juvenile idiopathic arthritis-associated uveitis

BACKGROUND: Chronic health conditions in children can have a significant impact on their quality of life. The aim of this study was to explore the subjective experience of children and young people being treated for chronic, non-infectious uveitis associated with a systemic disease such as juvenile idiopathic arthritis. METHODS: A semi-structured interview was conducted with 10 children and young people aged between 6 and 18 years of age and their parents. RESULTS: Preliminary thematic analysis indicated that both the treatment and complications of the disorder have a significant impact on the quality of life and emotional well-being of patients, not only in terms of the discomfort experienced but also in perceptions of social isolation, anxiety and sense of injustice. CONCLUSION: This study shows that themes including "impact on school", "social factors" and "emotional reactions" are important domains influencing health-related quality of life (HRQoL) in children with chronic uveitis. Inclusion of questions relating to these domains should be considered in future uveitis-specific tools examining HRQoL in these patients

Rapid-acting antidepressant drugs modulate affective bias in rats

How rapid-acting antidepressants (RAADs), such as ketamine, induce immediate and sustained improvements in mood in patients with major depressive disorder (MDD) is poorly understood. A core feature of MDD is the prevalence of cognitive processing biases associated with negative affective states, and the alleviation of negative affective biases may be an index of response to drug treatment. Here, we used an affective bias behavioral test in rats, based on an associative learning task, to investigate the effects of RAADs. To generate an affective bias, animals learned to associate two different digging substrates with a food reward in the presence or absence of an affective state manipulation. A choice between the two reward-associated digging substrates was used to quantify the affective bias generated. Acute treatment with the RAADs ketamine, scopolamine, or psilocybin selectively attenuated a negative affective bias in the affective bias test. Low, but not high, doses of ketamine and psilocybin reversed the valence of the negative affective bias 24 hours after RAAD treatment. Only treatment with psilocybin, but not ketamine or scopolamine, led to a positive affective bias that was dependent on new learning and memory formation. The relearning effects of ketamine were dependent on protein synthesis localized to the rat medial prefrontal cortex and could be modulated by cue reactivation, consistent with experience-dependent neural plasticity. These findings suggest a neuropsychological mechanism that may explain both the acute and sustained effects of RAADs, potentially linking their effects on neural plasticity with affective bias modulation in a rodent model

Marine yeast (Candida sake) cultured on herring brine side streams is a promising feed ingredient and omega-3 source for rainbow trout (Oncorhynchus mykiss)

A major challenge for the aquaculture industry is the supply of sustainable feeds. A promising model to achieve this is to utilize circular flows where feed ingredients, such as single cell protein, are cultivated using side streams of the food industry. The aim of this study was to evaluate the marine yeast Candida sake, produced on herring brine side streams, as a source of protein and immune stimulant in feed for salmonid fish. The dry C. sake product contained 54% protein (3.3% lysine and 0.8% methionine) and 13% lipids (1.1% eicosapentaenoic, EPA, and 1% docosahexaenoic acid, DHA). Four experimental diets were designed and tested in a 9-week feeding trial using juvenile rainbow trout (Oncorhynchus mykiss). A control diet containing both fish and plant-based ingredients constituted the base feed to which 20% (to evaluate effects on digestibility, growth and intestinal physiology), 20% heat-treated (to evaluate effects of downstream processing) and 3% (to evaluate immune stimulatory properties, replacing 3% soy protein concentrate) C. sake was added. The apparent digestibility coefficient of C. sake for protein, fat and gross energy was above 80%, and for amino acids above 90% regardless of treatment, suggesting a high bioavailability of C. sake. All three yeast containing diets performed equally to the control regarding specific growth rate, feed conversion ratio and functional intestinal health. These results suggest that C. sake is a promising alternative protein source for circular feeds in the salmonid industry. The presence of EPA and DHA represents an added value. The heat treatment increased the apparent digestibility coefficient of dry matter by 8% but decreased amino acid digestibility by on average 3%, indicating that heat treatment may not be the optimal downstream processing technique. Furthermore, the inclusion of 3% C. sake increased the intestinal lamina propria width and TGF-beta transcription, indicating an immune stimulating effect. Future research is needed to understand these immune modulatory effects of C. sake supplementation

Rethinking the employability of international graduate migrants: reflections on the experiences of Zimbabweans with degrees from England

The last decade has seen the rise of literatures that have focused on the rapid expansion of the numbers of international students in higher education globally and the growing policy discourse around improving graduate employability. However, both, inevitably, have limitations. Together, they tend to homogenise international learners and see them narrowly as simply economic actors. More recently, however, there have been signs of important new developments in both literatures, drawing on interactive employability and capability accounts that stress both agency and structure in more satisfactory ways. We seek to further the development of an account that bridges the new wave of student mobility research and the capability-employability account. In doing so, we offer two further elements to the literature. First, we aim to bridge the gap between international higher education accounts and those of migration and diasporic studies. Second, we deliberately focus on a group that is marginal to the mainstream discourse but who are migrants that have engaged in international higher education in order to improve their labour market prospects, amongst other motivations. We do this through examining the stories of five Zimbabweans who embarked on additional higher educational studies in England after migrating to the country. Through this unique approach, we offer an important new perspective on how the debates on international higher education, employability and migration can be taken forward through closer articulation between these accounts

Evaluation of Dynamic Cell Processes and Behavior Using Video Bioinformatics Tools

Just as body language can reveal a person’s state of well-being, dynamic changes in cell behavior and morphology can be used to monitor processes in cultured cells. This chapter discusses how CL-Quant software, a commercially available video bioinformatics tool, can be used to extract quantitative data on: (1) growth/proliferation, (2) cell and colony migration, (3) reactive oxygen species (ROS) production, and (4) neural differentiation. Protocols created using CL-Quant were used to analyze both single cells and colonies. Time-lapse experiments in which different cell types were subjected to various chemical exposures were done using Nikon BioStations. Proliferation rate was measured in human embryonic stem cell colonies by quantifying colony area (pixels) and in single cells by measuring confluency (pixels). Colony and single cell migration were studied by measuring total displacement (distance between the starting and ending points) and total distance traveled by the colonies/cells. To quantify ROS production, cells were pre-loaded with MitoSOX Red™, a mitochondrial ROS (superoxide) indicator, treated with various chemicals, then total intensity of the red fluorescence was measured in each frame. Lastly, neural stem cells were incubated in differentiation medium for 12 days, and time lapse images were collected daily. Differentiation of neural stem cells was quantified using a protocol that detects young neurons. CLQuant software can be used to evaluate biological processes in living cells, and the protocols developed in this project can be applied to basic research and toxicological studies, or to monitor quality control in culture facilities