PRISM | Institutional Repository
Communities in PRISM
Select a community to browse its collections.
Recent Submissions
Item
Embargo
Regulation of Fatty Acid Biosynthesis by Protein Phosphorylation of the α-CT Subunit of ACCase in Arabidopsis thaliana
(2024-04-30) Wong, Lana; Moorhead, Gregory; Zaremberg, Vanina; Burkinshaw, Brianne
Reversible protein phosphorylation, the most common post-translational modification, is essential in mediating most cellular functions in living organisms. With recent advances in omics-based technologies and its applications to studying the phosphoproteome of particular organisms, many previously uncharacterized phosphoproteins, protein kinases and protein phosphatases have been identified. Shewanella-like protein phophatase 1 (SLP1), a novel Arabidopsis thaliana protein phosphatase localized to the chloroplast, is a protein of interest as it is predicted to play an antagonistic role to the constitutively active chloroplast localized kinase, casein kinase 2α4 (CK2α4). Through a quantitative mass spectrometry based phosphoproteomics study carried out by previous members of the Moorhead Lab, many putative substrates of AtSLP1 were identified, one of them being the alpha-carboxyltransferase (α-CT) subunit of heteromeric acetyl-CoA carboxylase (htACCase). HtACCase catalyzes the first committed step of de novo fatty acid biosynthesis, and like AtSLP1, is chloroplast localized. HtACCase has been known to interact with the chloroplast envelope membrane through association with an integral membrane protein, however, the identity of this protein has been a mystery until recently. Carboxyltransferase interactors (CTIs), a group of small plastidal proteins of the inner chloroplast envelope have been identified to interact with the α-CT subunit of htACCase in a light-dependent manner. The focus of the research presented here was to characterize α-CT as a substrate of both CK2α4 and SLP1 and to determine the role of protein phosphorylation in lipid metabolism. Here, initial steps were taken in employing phosphospecific antibodies against the S741 site on α-CT, with immunoblot analysis confirming previous findings from a phosphoproteomics study indicating hyperphosphorylation of α-CT in the absence of SLP1. To explore the relationship between protein phosphorylation and the membrane partitioning of ACCase with CTI, recombinant proteins were cloned for subsequent protein-protein interaction studies. By studying the effects of this post-translational modification, we will gain a better understanding of the role of protein phosphorylation in regulating fatty acid biosynthesis, which will ultimately uncover new ways to increase bio-oil production in crops.
Item
Open Access
A Thematic Analysis of New Graduate Nurse Related Posts on TikTok
(2024-04-24) Mei, Carol; Jackson, Jennifer; Risling, Tracie; Radford, Scott; Devey Burry, Robin
New graduate nurses (NGNs) are entering the nursing workforce with enthusiasm, vigour, and current evidenced based knowledge (Murray et al., 2019). Negative experiences within the first two years of practice can lead to NGN attrition (Chernomas et al., 2010; García‐Martín et al., 2021; Kim & Shin, 2020; Parker et al., 2014). Due to the popularity of social media, many NGNs are sharing their experiences in practice on the social networking platform, TikTok. Using Braun and Clarkes’ (2006, 2021a) reflexive thematic analysis, my study answered the research question, “How is the NGN experience of transition to practice portrayed on TikTok?” I generated three themes that depicted the transition to practice experience on TikTok: The NGN as an Individual, The NGN as a Clinical Nurse, and The NGN as a Professional. The results of my study demonstrated a gradual progression in the NGNs comfort within their new nursing scope. As NGNs entered practice, they were eager to begin their career, but many did not demonstrate an understanding regarding the complexities of the nursing profession. As a result, majority of the NGNs felt unprepared for practice. NGNs with RN preceptors had more positive experiences within their transition to practice as compared to those that did not. These findings have implications for future practice. NGNs should be prepared at the university level for the initial challenges of transition. Additionally, nurse managers should cultivate a supportive environment and use pairing processes for RN preceptors and NGNs to aid in their transition to clinical practice.
Item
Open Access
Experiences of Parents of Emergent Bilingual Children Facing Autism Inquiry
(2024-05-07) Chen, Yao; Guo, Shibao; Roy, Sylvie; Zhao, Xu
Parents are unique experts on their children and their developmental environment. This is especially the case of emergent bilingual children’s parents, who are promising untapped sources of knowledge and wisdom about their children’s language learning, social communication, and development. Emergent bilingual children from immigrant families are in the process of becoming bilinguals when taking the language assessment (Garcia, 2009). The immigrant parents co-construct their children’s bilingual and bicultural experiences.
Social communication/interaction (SC/I) deficits are the main diagnostic criteria of Autism Spectrum Disorder (ASD). Parents’ perspectives on their children’s SC/I, including language skills, were rarely considered in the ASD evaluation. Informed by sociocultural theory (Vygotsky,1993), translanguaging (Garcia, 2009), and the middle-range theory (Merton, 1968), this research explores how immigrant parents describe their emergent bilingual children’s diagnosis of ASD. Data for the study were collected through semi-structured interviews and artifacts with 12 immigrant parents of 13 emergent bilingual children, documenting the nature and extent of immigrant children’s social communication and development, and interaction with the environment. Thematic and moment analysis (Wei, 2011) were used for data analysis. Results of the study revealed that, from the parents’ perspectives, the current ASD assessment tools and procedures marginalized emergent bilingual children. First, this study showed that the assessors in autism diagnosis often failed to recognize emergent bilingual children’s translanguaging practices and other social communication development features. Secondly, the cultural bias and expected SC/I development milestones in ASD assessment tools disadvantaged emergent bilingual children. Thirdly, the current ASD diagnosis often overlooks immigrant parent knowledge. The study suggested that immigrant parent knowledge could expand bilingual children’s SC/I evaluation. It hopes to inspire academics and communities to the interpretive paradigm (Vasilachis de Gialdino, 2009) on SC/I evaluation of emergent bilingual children in the ASD diagnostic process.
Item
Embargo
Chemically and Electrochemically Synthesized Graphene-Based Inks for 3D Printing of Advanced Electronics and Electromagnetic Shields
(2024-04-26) Erfanian, Elnaz; Sundararaj, Uttandaraman; Natale, Giovanniantonio; Bryant, Steve; Ewoldt, Randy H; Kim, Keekyoung
This thesis explores new approaches for the development of graphene-based inks for 3D printing of macro-scale patterned scaffolds for advanced applications, e.g., electronics and electromagnetic (EM) shields. These approaches include multiscale design of the inks, from nano-scale chemistry to micro-scale assembly. To achieve this, the chemical features of the nanosheets were fine-tuned by synthesizing different graphenes via both the electrochemical and chemical synthesis methods. The electrochemical method is considered safer, faster, and more environmentally friendly than chemical methods, primarily yielding pristine graphene with high electrical conductivity. However, due to the lack of surface functional groups, electrochemically synthesized graphene is challenging to disperse in water. In contrast, the chemical method produces highly oxidized graphene nanosheets, GO, which are easily dispersible in water due to their oxygen-containing functional groups but feature low electrical conductivity. In the first part of this thesis, graphene oxide (GO) is synthesized using modified Hummer method, selected for its water dispersibility, the most environmentally friendly medium. The resulting nanosheets exhibit both hydrophobic and hydrophilic characteristics; the hydrophobicity stems from the carbon basal plane, while the hydrophilicity originates from their functional groups. This duality makes it ideal for stabilizing Pickering emulsions featuring yield stress and proper rheological features, required for printing. Hence, utilizing emulsion templating, a non-printable graphene oxide dispersion was transformed into a printable yield-stress fluid, with the printing quality adjustable by modifying operational conditions. Although printable inks were developed by emulsion templating, the main constituent of these inks is GO, which is not conductive, limiting the application potential of the printed structure. GO can be transformed to reduced GO (rGO) via harsh chemical or thermal reduction post-processing methods. Thus, the second part of the thesis addresses the challenges of enhancing electrical conductivity in the conventional GO-based systems. Herein, an electrochemical synthesis approach was adopted, eliminating the need for harmful chemicals. However, this method introduced problems related to the graphene's limited water dispersibility. In this regard, electrochemically synthesized graphene (EGO) posed challenges in 3D printing, particularly its tendency to form droplets rather than a continuous filament. Thus, bio-based materials, i.e., TEMPO-oxidized cellulose nanofibrils (TOCNF), were employed as dispersants and rheological modifiers to improve the water compatibility of the highly conductive, nonpolar, electrochemically synthesized graphene nanosheets. A meticulous balance and optimization of TOCNF and EGO concentrations were required to achieve a printable ink that maintains the post-printed structure. This formulation allowed the identification of a 'window of printability,' creating a roadmap for fabricating 3D printed EGO-TOCNF ink. The high-fidelity printed structures maintained their form during drying and post-processing steps, enabling the fabrication of aerogels with tunable nano- and micro-scale designs. Hence, the multi-scale materials design of this work provided a unique opportunity to control the mechanical and electrical properties of the printed structures. Aerogels with a compression modulus ranging from 250-1096 kPa were obtained, and for the optimized ink, an EMI shielding effectiveness as high as 55.6 dB was achieved, eliminating the need for post-printing reduction processes. Although TOCNF bestows printability to graphene-based suspensions, it deteriorates the overall electrical conductivity due to its insulating nature. Thus, the third part of the thesis addresses the drawbacks of multicomponent inks, including the compromise in electrical conductivity when incorporating additives into graphene. A highly conductive all-graphene 3D printable aqueous ink was developed using a novel two-step electrochemical method with a specially designed intercalation step to control the surface functionality of the synthesized graphene nanosheets. Comprehensive characterization revealed the significant impact of graphene nanosheets’ physicochemical properties on the homogeneity, rheology, electrical conductivity, and EMI shielding effectiveness of their resultant aqueous-based inks. Phosphoric acid treatment was found to be the most effective in enhancing both printability and conductivity, achieving an electrical conductivity of 158 S/cm and an EMI shielding effectiveness of 50 dB at a 50 µm thickness, without the need for any post-processing reduction. Systematic experimentation with varying durations of phosphoric acid intercalation established that 10-minute intercalation produces inks with superior 3D printing fidelity, which can be converted to 3D patterned aerogels. This innovative approach enables rapid, continuous, and scalable manufacturing of lightweight, porous materials, avoiding environmentally harmful reductant chemistries or high-temperature processing. The elimination of a reduction step in the fabrication process aligns with industrial demands for energy-efficient production processes and high output rates, marking a significant advancement in the field of materials science. Thus, this work offers promising prospects for the application of graphene-based inks in advanced manufacturing technologies.
Item
Open Access
Investigating Tempo-Oxidized Cellulose Nanofiber Lubricating Greases Using Microscopy, Rheology, and Tribology
(2024-05-01) Uhryn, Jackson John Luke; Egberts, Philip; Trifkovic, Milana; Johansen, Craig; Natale, Giovanniantonio
Lubricating grease plays a significant role limiting the negative effects of friction and wear present in moving components across a multitude of industries and applications. However, current materials commonly used to formulate greases often pose environmental risks during operation and disposal efforts. Additionally, due to the complex colloidal structures that form the backbone of grease, a detailed understanding of underlying lubricating mechanisms remains elusive, especially if considering greases composed of nanoparticle constituents. This thesis focuses on using sustainable materials such as cellulose nanofibers and organically modified nanoclay to formulate lubricating grease. Special detail is given concerning formulation failures and successes highlighting the role of surface modification using oleic acid and interfacial stabilization from clay particles. The performance of these greases are systematically characterized using two forms of microscopy, laser scanning confocal microscopy and cryogenic scanning electron microscopy, to understand microstructure networking behavior that ultimately governs their response under mechanical stress. Rheological characterization is performed to quantitatively evaluate grease behavior under dynamic stress/strain. Lastly, tribological characterization is performed to evaluate friction and wear performance of formulated samples. Care has been taken to link all three avenues of characterization to help provide a more detailed understanding of underlying mechanisms governing these specific grease systems. It was observed that most greases are composed of networks between tightly held spheroid bundles of cellulose and oleic acid while clay interfacially adsorbs at the interface and prevents large scale aggregates from forming. However at high concentrations of cellulose and oleic acid (>10% and 0.75 OA:TOCN ratio, respectively), the dispersion effect is so great that agglomerates form bundle-like structures which significantly alter rheological and tribological responses. Rheological flow curves and amplitude sweeps indicate two main competing factors, aggregate size and number of interfacial connections, are responsible for differences in network dynamics. Overall morphology also plays an important role indicated by the high storage moduli obtained for fiber-like samples (≈ 35 kPa). Stribeck and steady sliding wear curves revealed excellent boundary lubrication coefficient of friction performance in the range of 0.05-0.10 for all samples courtesy of both oleic acid and nanoparticle surface activity/tribofilm generation. It also revealed interesting high wear behavior at high relative concentrations of oleic acid. For example, wear scar diameter roughly increases 6x at 0.75 OA:TOCN ratio compared to both 0.25 and 0.50 ratios.