2,047 research outputs found
Tribological properties of gradient-density hydrogel surfaces
No full textSubmission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2023-12-01The student, Christopher Johnson, accepted the attached license on 2021-10-07 at 13:24.The student, Christopher Johnson, submitted this Dissertation for approval on 2021-10-07 at 14:23.This Dissertation was approved for publication on 2021-10-08 at 10:06.DSpace SAF Submission Ingestion Package generated from Vireo submission #17153 on 2022-04-06 at 17:16:39Made available in DSpace on 2022-04-29T21:42:55Z (GMT). No. of bitstreams: 3
JOHNSON-DISSERTATION-2021.pdf: 19081617 bytes, checksum: 93efe57449b7c5571d40b62f4826b73e (MD5)
DissertationOverleafSource_CLJ.zip: 20053500 bytes, checksum: d0769c95e33a6a51d3308850222a81f8 (MD5)
LICENSE.txt: 4216 bytes, checksum: 4bd9b28dba0d60ff2a10db6eb8fdf624 (MD5)
Previous issue date: 2021-10-08Embargo set by: Seth Robbins for item 123318
Lift date: 2024-04-29T21:43:01Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 123318
Lift date: 2024-04-29T21:44:44Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 123318
Lift date: 2024-04-29T21:46:25Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 123318
Lift date: 2024-04-29T21:47:53Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I OnlyHydrogels are soft hydrated polymer networks that are widely used in research and industry due to their similarity to biological tissues. As one of the leading materials used for tissue surrogates or biological interfaces, hydrogels exhibit useful properties such as biocompatibility, high elasticity, and low friction. While there is a continuously expanding body of research investigating hydrogels, some tribological studies are seemingly contradictory, even showing vastly different frictional behavior for the same hydrogel composition. One explanation for this comes from the ‘mold effect’, first mentioned in 2001, whereby the mold material alters the polymerization process of the hydrogel, imparting different properties to the surface in contact with it. The ‘mold effect’ was not considered or studied in detail until recent work published in 2019, where researchers found that the effect drastically reduced the stiffness of hydrogels polymerized against polymer molds compared to glass-molded hydrogels. Several studies in subsequent years finally determined that the ‘mold effect’ is due to absorbed oxygen within the mold surface interfering with the polymerization, inducing a dilute gradient-density surface layer exhibiting altered properties. However, the precise structure of the gradient surface layer, its contact response, and its effect on lubrication have not yet been characterized. Such knowledge would prove useful for designs of composite hydrogels utilizing the gradient surface layer for its special frictional properties. In order to fully characterize the hydrogel gradient surface layer, we first developed a method to view contact area of a probe on a hydrogel substrate in real time using particle exclusion microscopy. We then utilized this technique during indentation, creep, and sliding experiments on a standard hydrogel composition. Indentation experiments confirmed the dilute gradient nature of the surface layer, showing that it follows an evolving contact response with depth. This contact response could be approximated through piecewise modeling starting with a polymer brush contact model, then a Winkler foundation model, and finally the classic Hertzian contact model. Calculation of the contact area using these contact models verified that the indentation data was aligned with the piecewise model. This provided information regarding the polymer structure of the gradient layer: that it is composed of brush-like polymer segments swollen in water, where the polymer density and degree of crosslinking increase further into the depth. Creep experiments revealed that the gradient layer allows poroelastic relaxation even at pressures far below the reported osmotic pressure of the bulk crosslinked structure, which further supports the less-dense, ‘brushy’ nature of the gradient layer. Sliding experiments showed enhanced lubrication and strong speed dependence on the friction, but no dependence on the contact area. The lack of transient friction behavior also demonstrated the quick rehydration of the gradient layer during the phases out of contact. Indentation, creep, and sliding experiments were also conducted on four other hydrogels of varying monomer and crosslinker percent in order to determine the effect of composition on the gradient layer. All compositions exhibited a poroelastic gradient layer that followed the evolving contact model previously formulated. Stiffer compositions had thinner gradient layers whose response under shear was less consistent with changes to load and speed. Finally, we found that changing the monomer-to-crosslinker ratio was more effective at changing the consistency of the shear response and the gradient layer thickness. These findings prove that the dilute structure of the gradient layer provides enhanced lubrication under sliding conditions by improving hydrodynamic lubrication and reducing polymer-probe interactions. This knowledge can potentially be used to create hydrogels with a stiff load-bearing bulk that retains optimal lubrication across a wide range of operating conditions
Correction: Fabrication of asymmetrical diffusion dialysis membranes for rapid acid recovery with high purity
No full textDr Christopher D. Easton made a signicant contribution to the work published in Journal of Materials Chemistry A (titled “Fabrication of asymmetrical diffusion dialysis membranes for rapid acid recovery with high purity”, DOI: 10.1039/C5TA05185A), which included conducting the XPS experiments on the membrane samples, processing the XPS data, and interpreting the results in the context of the work. Therefore, Dr Easton should be added as a co-author. The new author list is Xiaocheng Lin, Ezzatollah Shamsaei, Biao Kong, Jefferson Zhe Liu, Tongwen Xu, Christopher D. Easton and Huanting Wang. We apologize to the readers forany inconvenience this may cause.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers
Zinc has insulin-mimetic properties which enhance spinal fusion in a rat model
No full textBACKGROUND CONTEXT: Previous studies have found that insulin or insulin-like growth factor treatment can stimulate fracture healing in diabetic and normal animal models, and increase fusion rates in a rat spinal fusion model. Insulin-mimetic agents, such as zinc, have demonstrated antidiabetic effects in animal and human studies, and these agents that mimic the effects of insulin could produce the same beneficial effects on bone regeneration and spinal fusion.
PURPOSE: The purpose of this study was to analyze the effects of locally applied zinc on spinal fusion in a rat model.
STUDY DESIGN/SETTING: Institutional Animal Care and Use Committee-approved animal study using Sprague-Dawley rats was used as the study design.
METHODS: Thirty Sprague-Dawley rats (450-500 g) underwent L4-L5 posterolateral lumbar fusion (PLF). After decortication and application of approximately 0.3 g of autograft per side, one of three pellets were added to each site: high-dose zinc calcium sulfate (ZnCaSO4), low-dose ZnCaSO4 (half of the high dose), or a control palmitic acid pellet (no Zn dose). Systemic blood glucose levels were measured 24 hours postoperatively. Rats were sacrificed after 8 weeks and the PLFs analyzed qualitatively by manual palpation and radiograph review, and quantitatively by micro-computed tomography (CT) analysis of bone volume and trabecular thickness. Statistical analyses with p-values set at .05 were accomplished with analysis of variance, followed by posthoc tests for quantitative data, or Mann-Whitney rank tests for qualitative assessments.
RESULTS: Compared with controls, the low-dose zinc group demonstrated a significantly higher manual palpation grade (p=.011), radiographic score (p=.045), and bone formation on micro-CT (172.9 mm3 vs. 126.7 mm3 for controls) (p3 vs. 126.7 mm3) (p<.01) versus controls, and was trending toward higher manual palpation scores (p=.058).
CONCLUSIONS: This study demonstrates the potential benefit of a locally applied insulin-mimetic agent, such as zinc, in a rat lumbar fusion model. Previous studies have demonstrated the benefits of local insulin application in the same model, and it appears that zinc has similar effects.Peer reviewe
Sweet taste and nutrient value subdivide rewarding dopaminergic neurons in Drosophila
No full textCo-author Christopher J. Burke is a doctoral student in the Neuroscience Program in the Morningside Graduate School of Biomedical Sciences (GSBS) at UMass Medical School.Dopaminergic neurons provide reward learning signals in mammals and insects [1-4]. Recent work in Drosophila has demonstrated that water-reinforcing dopaminergic neurons are different to those for nutritious sugars [5]. Here, we tested whether the sweet taste and nutrient properties of sugar reinforcement further subdivide the fly reward system. We found that dopaminergic neurons expressing the OAMB octopamine receptor [6] specifically convey the short-term reinforcing effects of sweet taste [4]. These dopaminergic neurons project to the beta'2 and gamma4 regions of the mushroom body lobes. In contrast, nutrient-dependent long-term memory requires different dopaminergic neurons that project to the gamma5b regions, and it can be artificially reinforced by those projecting to the beta lobe and adjacent alpha1 region. Surprisingly, whereas artificial implantation and expression of short-term memory occur in satiated flies, formation and expression of artificial long-term memory require flies to be hungry. These studies suggest that short-term and long-term sugar memories have different physiological constraints. They also demonstrate further functional heterogeneity within the rewarding dopaminergic neuron population.Neuroscienc
Early transition metal complexes of carbene donors linked to cyclopentadienyl ring analogues or amidine/amidinate moieties
No full textThe new indenyl-functionalised NHC potassium salt, 1-[3-(4, 7-dimethylindenylpropyl]-3-(2,6-diisopropylphenyl)imidazol-2-ylidenepotassium, has been synthesised. Complexes oftitanium, zirconium and chromium containing this ligand and the two carbon bridge analogue,1-[2-(4,7-dimethylindenyl)ethyl]-3-(2,6-diisopropylphenyl)imidazol-2 ylidene potassium,have been synthesised and characterised by X-ray crystallographic techniques. The followingcomplexes were tested as catalysts for the oligomerisation of ethylene in the presence ofMAO: 3-(2,6-diisopropylphenyl)-1-[2-(4,7-dimethylindenyl)ethyl]-imidazol-2-ylidene(tertbutylimido)titanium chloride, 3-(2,6-diisopropylphenyl)-1-[3-(4,7-dimethylindenyl)propyl]imidazol-2-ylidene(tert-butylimido)titanium chloride, 3-(2,6-diisopropylphenyl)-1-[3-(4,7-dimethylindenyl)propyl]imidazol-2-ylidenezirconiumtrichloride, 3-(2,6-diisopropylphenyl)-1-[2-(4,7-dimethylindenyl)ethyl]imidazol-2-ylidenezirconium trichloride, 3-(2,6-Diisopropylphenyl)-1-[2-(4,7-dimethylindenyl)ethyl]-imidazol-2-ylidenechromium dichloride, 3-(2,6-diisopropylphenyl)-1-[3-(4,7-(dimethylindenyl)propyl]imidazol-2-ylidene chromium dichloride, 3-(2,6-diisopropylphenyl)-1-[3-(4,7-dimethylindenyl)propyl]-imidazol-2-ylidene chromium methyl chloride and 3-(2,6-diisopropylphenyl)-1-[2-(4,7-dimethylindenyl)ethyl]-imidazol-2-ylidenevanadium dichloride.The following alkyl chromium complexes containing 1-[2-(4,7-dimethylindenyl)ethyl]-3-(2,6-diisopropylphenyl)imidazol-2 ylidene potassium have also been synthesised: 3-(2,6-diisopropylphenyl)-1-[2-(4,7-dimethylindenyl)ethyl]-imidazol-2-ylidene chromium phenylchloride and 3-(2,6-diisopropyl-phenyl)-1-[2-(4, 7-dimethylindenyl)ethyl]-imidazol-2-ylidenechromium dibenzyl. Chromium cations have been synthesised using as starting materials thechromium alkyl complexes. The Cr(II) complex 3-(2,6-diisopropyl-phenyl)-1-[2-(4, 7-dimethylindenyl)ethyl]-imidazol-2-ylidene chromium monochloride and a partially oxidiseddimerised product were also isolated. 5-(2-chloroethyl)- 1, 2, 3, 4-tetramethylcyclopentadieneand 5-(3-chloropropyl) 1, 2, 3, 4-tetramethylcyclopentadiene were synthesised and isolated asgeminal isomers for the first time.The trialkyl chromium complex, tribenzyl chromium tris(tetrahydrofuran) was synthesisedand also it was used as starting material for the complexes di(benzyl)chromium bis(1, 3-diisopropylimidazol-2-ylindene) and tri(benzyl)chromium TACN. All complexes werecharacterised by X-ray crystallography.The imidazolium salt 3-(2.6-diisopropylphenyl)-1-[N, N-bis(2,6-diisopropylphenyl)acetamidyl] imidazolium chloride was synthesised and used as a precursorfor the synthesis of amidinate-functionalised NHC zirconium and amidine-functionalisedNHC silver complexes. Double deprotonation of 3-(2,6-diisopropylphenyl)-1-[N, N’-bis(2,6-diisopropylphenyl)acetamidyl] imidazolium chloride gave the amidinate-functionalised NHCligand, 3-(2.6-diisopropylphenyl)-1-[2-N, N’bis(2,6diisopropylphenylamidinate)ethyl]imidazol-2-ylidenepotassium. Titanium, zirconium andchromium complexes containing this ligand were synthesised and characterised by X-raycrystallographic techniques. Transmetallation of the amidine-functionalised NHC silvercomplex with [Rh(COD)Cl]2 and [Ir(COD)Cl]2 gave the corresponding species. Rh(amidinefunctionalisedNHC)(COD)Cl reacted with Na(BAr)4 (Ar = 3,5-CF3C6H3) to give the cationRh(amidine-functionalised NHC)(COD)]+[BAr4]-. These species were also characterised byX-ray diffraction techniques
Freshly isolated Lin-SP cells express FAPs surface markers but are capable of myogenic differentiation.
No full text<p><b>A</b>: RT-PCR analysis of freshly isolated Lin- SP cells from wild type (WT) and <i>mdx<sup>5cv</sup></i> (MDX) muscle for myogenic markers (Pax7 and Myf5) and FAPs markers (PDGFRα and Sca1). Positive controls (PC) are sorted Sca1-positive cells for Sca1 and Lin- MP cells for Pax7, Myf5 and PDGFRα. Negative controls (NC) are sorted Sca1-negative cells for Sca1 and CD45-positive MP cells for Pax7, Myf5 and PDGFRα. <b>B, C</b>: FACS analysis of PDGFRα and Sca1 protein expression in Lin- SP cells (<b>B</b>) and Lin- MP cells (<b>C</b>) from wild type (WT) and <i>mdx<sup>5cv</sup></i> (MDX) muscle. Percentages of cells double positive (red) and double negative (green) for PDGFRα and Sca1 are shown. <b>D</b>: Confirmation by RT-PCR for PDGFRα expression in Lin- SP and Lin- MP cells sorted into PDGFRα-positive (Pα+) and PDGFRα-negative (Pα−) sub-fractions. <b>E</b>: <i>In vitro</i> myogenic differentiation of Lin- SP and MP cells sorted based on PDGFRα (Pα) expression. Cells were fixed after 14 days in culture and immunolabelled for α-actinin (green) to reveal myotubes. Cultures were counterstained with DAPI (blue) to visualize nuclei. Lin- MP Pα+ cells correspond to the previously characterized FAPs. Lin- MP Pα− cells are enriched in myogenic cells and also contain fibroblasts. Cultured wild type Lin- MP Pα− cells had 2,261 myotubes while cultured <i>mdx<sup>5cv</sup></i> Lin- MP Pα− cells had only 541 myotubes. Lin- SP Pα− cells did not survive in culture and are not shown. Scale bar = 400 μm. <b>E</b>: Cultures of Lin- SP Pα− cells were double labeled with antibodies to α-actinin (green) and collagen I (red) to visualize myotubes and fibroblasts, respectively. Cultures of Lin- SP Pα− cells from dystrophic muscle (MDX) do not contain myotubes but give rise to fibroblasts. Scale bar = 100 μm. <b>G</b>. Quantitative RT-PCR for Pax7 expression in Pdgfrα+ and Pdgfrα− Lin-SP cells, and Pdgfrα− Lin-MP cells. Data is presented as means +/− s.d. from 3 technical replicates.</p
How can we learn whether firm policies are working in africa ? challenges (and solutions?) for experiments and structural models
No full textFirm productivity is low in African countries, prompting governments to try a number of active policies to improve it. Yet despite the millions of dollars spent on these policies, we are far from a situation where we know whether many of them are yielding the desired payoffs. This paper establishes some basic facts about the number and heterogeneity of firms in different sub-Saharan African countries and discusses their implications for experimental and structural approaches towards trying to estimate firm policy impacts. It shows that the typical firm program such as a matching grant scheme or business training program involves only 100 to 300 firms, which are often very heterogeneous in terms of employment and sales levels. As a result, standard experimental designs will lack any power to detect reasonable sized treatment impacts, while structural models which assume common production technologies and few missing markets will be ill-suited to capture the key constraints firms face. Nevertheless, the author suggests a way forward which involves focusing on a more homogeneous sub-sample of firms and collecting a lot more data on them than is typically collected.Microfinance,Small Scale Enterprise,E-Business,ICT Policy and Strategies,Banks&Banking Reform
In vitro cell-autonomous myogenic differentiation of muscle SP cells and Lin- SP cells.
No full text<p><b>A–C</b>: Phase pictures of wild type muscle SP cells cultured in EGM medium on Matrigel. Cells attached to Matrigel at days 3 (<b>A</b>), had significantly proliferated by day 7 (<b>B</b>), and differentiated into contracting multinucleated myotubes by day 11 (<b>C</b>). Scale bar = 50 μm. <b>D–F</b>: Immunostaining of muscle SP cultures for the myotube marker α-actinin (<b>D</b>; green) at day 11; for the myoblast marker myogenin (<b>E</b>; green) at day 5; and for the satellite cell marker Pax 7 (F; green) at day 3. Cells were counterstained with DAPI (blue) to visualize nuclei. Scale bar = 100 μm. <b>G</b>: Phase picture of day 11 cultures of primary myogenic cells in EGM medium on a Matrigel substrate showing formation of large numbers of myotubes. <b>H–I</b>: Isolation of muscle SP sub-populations by FACS. Total muscle mononuclear cells were labeled with antibodies to CD31 and CD45 and CD31+, CD45+ and Lin- cells were sorted first (<b>H</b>). Cells in each fraction were re-analyzed by FACS for incorporation of Hoechst and SP cells were isolated. The SP profile for the Lin- subset of cells in <b>H</b> is shown in <b>I</b>. MP cells are indicated. <b>J–L</b>: Phase pictures of day 11 cultures of CD45+ SP cells (<b>J</b>), CD31+ SP cells (<b>K</b>), and Lin- SP cells (<b>L</b>). Scale bar = 50 μm. <b>M</b>: Pax7 mRNA was detected by RT-PCR in RNA isolated from muscle SP and Lin-SP cells but not CD31+/CD45− SP cells, Lin- MP cells shown in <b>I</b> were used as a positive control since they contain satellite cells. RNA was isolated immediately after cell isolation by FACS from wild type muscles.</p
Implementing Temporary LED Construction Lighting
No full textThesis (Master's)--University of Washington, 2017-06LED lighting technology is continuing to grow and change every 6 months. While other manufacturers and consumers are finding creative ways to implement them in their products and everyday life, the construction industry has yet to widely adopt and embrace the technology as a temporary lighting source on their projects. Although initially expensive when compared with other construction lighting systems, the cost of LEDs is decreasing while improvements in LED luminaire efficiency increases. Furthermore, the energy, maintenance, and safety benefits of a temporary LED lighting system may be an overlooked consideration for general contractors and subcontractors as (1) the information has yet to be thoroughly studied and targeted at the construction industry, (2) initial costs of entry may be prohibitive when compared with older sources of luminance, and/or (3) general contractors and subcontractors may be satisfied with the status quo. Unfortunately, improvements in temporary lighting technology for building construction have been neglected academically and within the construction industry. However, the objective of this thesis is to serve as a guide by looking at the safety, energy and maintenance benefits of LED construction lighting, through literature review, lessons learned from two case studies, and independent investigation by the author. Literature review will provide a background on how LEDs work, what traditional lighting is, who regulates quality of luminance on jobsites, and how lighting affects the safety and health of workers. 2 Next, the thesis incorporates two case studies, both of which were conducted at the behest of the University of Washington’s (UW) Capital Planning and Development office (CPD). The first case study was generated in 2014. The study, written by UW Construction Management graduate student Yi Jie Huang, focused on the temporary construction lighting at the UW’s Bothell Phase 3 Project. The report looks at: (1) the system’s installation method; (2) labor, material, and energy cost; (3) stakeholder interviews; and (4) a qualitative survey of the workers. The second case study, written by UW Construction Management and Occupational Safety and Health graduate student Christopher Mak, further updates the UW’s narrative on LED lighting, and illustrates the history and reasoning behind implementing low-voltage LEDs on their projects. The report homes in on the LED utilization at the UW’s Animal Research and Care Facility (ARCF) construction site. Like the report on the Bothell Phase 3 project, the second case study looks at: (1) installation method; (2) labor, material, and energy costs; and (3) conducts a qualitative survey of workers. Finally, the author ran three quantitative studies looking at light levels, energy use, and lighting quality. Data collected is displayed and interpreted within. The final issue the author looks at is the possibility of glare, which arose during qualitative data analysis of both case studies’ responses. Glare emanating from white LEDs is a potential safety hazard and an environmental quality problem. Moreover, defining hazardous amounts of glare can be subjective and hard to quantify. The author implements a glare quantifying methodology using HDR photography, and uses the technique to gauge the quality of light emanating from ARCF’s new LEDs. The thesis concludes with lessons learned regarding how users can better implement temporary LED lighting to their full benefit from the trials and tribulations experienced by the UW, observations made by the author, and from the Seattle City Light inspection and energy incentive process
Multimodal Multiplexed Immunoimaging with Nanostars to Detect Multiple Immunomarkers and Monitor Response to Immunotherapies
No full textThe overexpression of immunomarker programmed cell death protein 1 (PD-1) and engagement of PD-1 to its ligand, PD-L1, are involved in the functional impairment of cluster of differentiation 8+ (CD8+) T cells, contributing to cancer progression. However, heterogeneities in PD-L1 expression and variabilities in biopsy-based assays render current approaches inaccurate in predicting PD-L1 status. Therefore, PD-L1 screening alone is not predictive of patient response to treatment, which motivates us to simultaneously detect multiple immunomarkers engaged in immune modulation. Here, we have developed multimodal probes, immunoactive gold nanostars (IGNs), that accurately detect PD-L1+ tumor cells and CD8+ T cells simultaneously in vivo, surpassing the limitations of current immunoimaging techniques. IGNs integrate the whole-body imaging of positron emission tomography with high sensitivity and multiplexing of Raman spectroscopy, enabling the dynamic tracking of both immunomarkers. IGNs also monitor response to immunotherapies in mice treated with combinatorial PD-L1 and CD137 agonists and distinguish responders from those nonresponsive to treatment. Our results showed a multifunctional nanoscale probe with capabilities that cannot be achieved with either modality alone, allowing multiplexed immunologic tumor profiling critical for predicting early response to immunotherapies.This article is published as Ou, Yu-Chuan, Xiaona Wen, Christopher A. Johnson, Daniel Shae, Oscar D. Ayala, Joseph A. Webb, Eugene C. Lin, et al. "Multimodal Multiplexed Immunoimaging with Nanostars to Detect Multiple Immunomarkers and Monitor Response to Immunotherapies." ACS Nano 14, no. 1 (2020). DOI: 10.1021/acsnano.9b07326.</p
- …
