531 research outputs found
Inducing two-way shape memory effect in Nitinol-Polymer Composite
No full textTitle: Inducing Two-way Shape Memory Effect in NiTi-polymer Composite Author: Jakub Zeman Supervisor: Sneha Manjaree Samal, Ph.D., Institute of Physics of the Czech Academy of Sciences Abstract: Two-way shape memory effect (TWSME) allows material to ac- tively deform between two remembered shapes without the application of ex- ternal force. The most common stimulus is temperature change with several approaches to induce shape memory effect in the material. The approach stud- ied in this thesis utilizes Nitinol and shape memory polymer. By combining these two materials, bistable TWSME was induced in the composite. Bistable TWSME allows the material to be in both of its remembered shapes at a single temperature. The shape of the material depends on the temperature profile by which the target temperature was reached. To create the composite Nitinol foil was shape set and its surface laser lined to increase adhesion with the polymer. Out of the studied polymers, the best properties for the preparation of com- posite were exhibited by a blend of 60 % TPU and 40 % PCL by weight. The composite was then prepared by hot press and tested. Keywords: inducing two-way shape memory effect, Nitinol, shape memory polymer, composite
Correlations of sequences modulo one and statistics of geometrical objects associated to visible points
No full textThis thesis is divided into two major topics. In the first, we study the topic of distribution of sequences modulo one. In particular, we look at the spacing distributions between members of rational valued sequences modulo one. We come up with examples of many such sequences which behave as randomly chosen numbers from the unit interval. These include examples from the class of exponentially as well as sub-exponentially growing sequences. In the second part, we examine distribution questions for certain geometrical objects, for example, Farey-Ford and generalized Farey-Ford polygons and Farey-Ford parabolas associated to visible lattice points. As the names suggest, these objects are constructed based on the relation between visible points/Farey fractions and their geometrical interpretation in the form of Ford circles. We study the distribution of moments of various geometrical parameters associated to these objects by giving asymptotic formulas employing tools from analytic number theory.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2019-08-01The student, Sneha Chaubey, accepted the attached license on 2017-07-10 at 00:37.The student, Sneha Chaubey, submitted this Dissertation for approval on 2017-07-10 at 00:48.This Dissertation was approved for publication on 2017-07-10 at 14:55.DSpace SAF Submission Ingestion Package generated from Vireo submission #11355 on 2017-09-29 at 10:46:47Made available in DSpace on 2017-09-29T17:45:18Z (GMT). No. of bitstreams: 3
CHAUBEY-DISSERTATION-2017.pdf: 2390344 bytes, checksum: 85df40224274309f0069b1dd72da95f0 (MD5)
LICENSE.txt: 4210 bytes, checksum: e2fbd269832c3033a500ae5f693ca74d (MD5)
PROQUEST_LICENSE.txt: 4556 bytes, checksum: b9117e1cd9cca4c3ecb98e8b13e1c1a0 (MD5)
Previous issue date: 2017-07-10Embargo set by: Colleen Fallaw for item 103453
Lift date: 2019-09-29T17:48:06Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 103453
Lift date: 2020-03-02T19:56:41Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 103453
Lift date: 2020-03-02T19:59:52Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 103453
Lift date: 2020-03-02T20:02:46Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Only Restriction Lifted for Item 103453 on 2020-03-03T10:15:22Z
Vyvolání obousměrné tvarové paměti v NiTi-polymerovém kompozitu
No full textNázev práce: Vyvolání obousměrné tvarové paměti v NiTi-polymerovém kompozitu Autor: Jakub Zeman Katedra: Katedra fyziky materiálů, Matematicko-fyzikální fakulta, Uni- verzita Karlova Vedoucí bakalářské práce: Sneha Manjaree Samal, Ph.D., Fyzikální ústav Akademie věd České republiky Abstrakt: Obousměrná tvarová paměť umožňuje deformaci materiálu mezi dvěma zapamatovatelnými tvary bez působení vnějších sil, přičemž aktivaci změny tvaru se využívá nejčastěji změna teploty. Mezi řadou způsobů, jak dosáhnout obousměrné tvarové paměti, byla v této práci využita kombinace kovového materiálu Nitinol a vybraného polymeru s tvarovou pamětí. V kom- pozitním materiálu z těchto dvou složek bylo dosaženo bistabilní obousměrné tvarové paměti. Bistabilní obousměrná tvarová paměť je unikátní tím, že umožňuje existenci materiálu v obou zapamatovaných stavech při stejné teplotě. Bylo prokázáno, že rozhodujícím faktorem pro dosažení určitého tvaru je předešlý teplotní průběh kompozitního materiálu. Pro zlepšené spojení kovového Niti- nolu a polymerního materiálu byl povrch NiTi upraven laserem. Mezi několika studovanými polymery prokázal nejlepší vlastnosti polymer vyrobený ze dvou složek, a to 60...Title: Inducing Two-way Shape Memory Effect in NiTi-polymer Composite Author: Jakub Zeman Supervisor: Sneha Manjaree Samal, Ph.D., Institute of Physics of the Czech Academy of Sciences Abstract: Two-way shape memory effect (TWSME) allows material to ac- tively deform between two remembered shapes without the application of ex- ternal force. The most common stimulus is temperature change with several approaches to induce shape memory effect in the material. The approach stud- ied in this thesis utilizes Nitinol and shape memory polymer. By combining these two materials, bistable TWSME was induced in the composite. Bistable TWSME allows the material to be in both of its remembered shapes at a single temperature. The shape of the material depends on the temperature profile by which the target temperature was reached. To create the composite Nitinol foil was shape set and its surface laser lined to increase adhesion with the polymer. Out of the studied polymers, the best properties for the preparation of com- posite were exhibited by a blend of 60 % TPU and 40 % PCL by weight. The composite was then prepared by hot press and tested. Keywords: inducing two-way shape memory effect, Nitinol, shape memory polymer, composite 1Department of Physics of MaterialsKatedra fyziky materiálůMatematicko-fyzikální fakultaFaculty of Mathematics and Physic
Crosstalk between NDR kinase pathways coordinates cell cycle dependent actin rearrangements
No full textFirst author Sneha Gupta is a doctoral student in the Interdisciplinary Graduate Program in the Graduate School of Biomedical Sciences (GSBS) at UMass Medical School.Regulation of cytoskeletal remodeling is essential for cell cycle transitions. In fission yeast two NDR kinase signaling cascades, MOR and SIN, regulate the actin cytoskeleton to promote polarized growth during interphase and cytokinesis respectively. Our understanding of how these signaling pathways are coordinated to assist transition between the two cell-cycle stages is limited. Here, we review work from our laboratory, which reveals that cross talk between the SIN and MOR pathways is required for inhibition of interphase polarity programs during cytokinesis. Given the conservation of NDR kinase signaling pathways, our results may define general mechanisms by which these pathways are coordinated in higher organisms
Corrigendum to “Tribological behavior and biocompatibility of novel nickel-free stainless steel manufactured via laser powder bed fusion for biomedical applications” [Mater. Des. 242 (2024) 113013]
No full textThe authors wish to inform that the correct and only affiliation of the co-author Sneha Goel is the following: Advanced Materials for Nuclear Energy, VTT Technical Research Centre of Finland, Kivimiehentie 3, 02150 Espoo, Finland The correct affiliation has been replaced as above. The authors would like to apologise for any inconvenience caused.</p
Facebook: Is it undermining Indian culture?
No full textIncreasing parental intervention in order to diminish the detrimental effects of social media sitesSpring 2012Accompanied by video fil
Study of Diffusion in Confined Nanospace
No full textThe cellular environment is characterized by confinement and macro-molecular crowding: both concepts that have been studied separately. To understand kinetics of enzymatic reactions, there is a need to understand how the diffusional encounters of enzyme and substrate proceed in an environmentthat is confined and crowded simultaneously. The project carried out in this thesis is the first step towards achieving the ultimate goal of studying biochemical reactions in native cellular environment - Understanding diffusion in confinement. Despite multiple investigations of diffusion of analytes in confinement, there exists a research gap. There is inconsistency in the interpretation of the results and in the dependence of diffusion properties of analytes of different sizes in channels of different dimensions. Hence, to bridge the research gap, the main goal of this thesis project was to find the diffusion coefficient of 100 nm polystyrene beads in microchannel (200 µm wide and 4.5 µm high) and nanochannel (5 or 10 µm wide and 300 nm high). The Brownian motion of particles was observed using Confocal Laser Scanning Microscope. A preliminary study first confirmed the reliability and optimization of the particle tracking method of finding diffusion coefficient. Diffusion coefficient of the particles determined experimentally in microchannel (bulk system) was in agreement with the theoretical estimate and statistically significant. Experiments in the nanochannel revealed a reduction in the particle diffusion coefficient of about ∼52% compared to bulk, due to interactions with the confining depth(300 nm) of nanochannel. An interesting behaviour was also exhibited by particles diffusing close to the side wall along the width of nanochannels, which was not confining (5 or 10 µm). The diffusion coefficient in such a case reduced by around ∼90% relative to bulk. The reduction in both cases can be mainly attributed to hydrodynamic interactions. The experimental investigations of diffusion coefficient carried out in this study were in agreement with long standing theoretical predictions. However, the research gap could not be fully expelled.<br/
Hydrogel encapsulation of cells mimics the whole body response to LMHF vibrations
No full textLow-magnitude high-frequency (LMHF) vibrations show anabolic effects on bone when applied to the whole body in both animal and human studies. As such, it is being explored as a treatment for osteoporosis and osteopenia in vulnerable populations. In humans, whole-body vibrations have shown modest increases in the bone mineral density of postmenopausal women, children and adolescents, though it had no effect in young adults. These conflicting results prompted long term studies to establish the optimal frequency, magnitude and duration of the vibration. In vitro cellular studies have been carried out to study the physical and biologic mechanisms underlining these outcomes. But there are conflicting results of LMHF vibrations when applied to cell culture as well, with some studies showing no effect when cells are cultured in 2D monolayer as opposed to other studies reporting increased differentiation of progenitor cells towards an osteogenic lineage when cells are cultured in 3D scaffolds. It is worthy of note that the majority of scaffolds used in these studies are from natural sources, which in and of themselves may promote differentiation due to biochemical and microarchitectural cues. This master thesis seeks to explore the effect of Low magnitude high frequency vibrations on human mesenchymal stem cells (hMSCs) encapsulated within a 3D microsphere structure composed of synthetic polymer polyethylene glycol diacrylate (PEGDA). Synthetic PEGDA has no inherent cues and can serve as a “blank slate” to the entrapped cells. In this study, three different intensity vibrations of 0.3g, 3g and 6g at 100Hz were applied for 24 hours to the encapsulated hMSCs by means of a vibration unit. These cells were subsequently tested for adipocyte, chondrocyte and osteoblast differentiation over a period of 21 days. There was early onset of osteogenic differentiation in 0.3 g and 3 g test samples compared to control samples, while there was no osteogenic differentiation at all observed in 6g test samples. In addition, as the magnitude of acceleration applied increased, the osteogenic differentiation of the encapsulated hMSCs decreased. Thus, LMHF vibrations with low accelerations accelerated the osteogenic differentiation of encapsulated hMSCs, indicating that hydrogel-encapsulated hMSCs may mimic the whole body response to vibration, which paves the way for further in vitro LMHF experiments with encapsulated cells.M.S.Includes bibliographical referencesby Sneha Meht
Ethnea -- an instance-based ethnicity classifier based on geo-coded author names in a large-scale bibliographic database
No full textWe present a nearest neighbor approach to ethnicity classification. Given an author name, all of its instances (or the most similar ones) in PubMed are identified and coupled with their respective country of affiliation, and then probabilistically mapped to a set of 26 predefined ethnicities. The dominant ethnicity (or pair of ethnicities) is assigned as the class. The predictions are also used to upgrade Genni (Smith, Singh, and Torvik, 2013) to provide ethnicity-specific gender predictions for cases like Italian vs. English Andrea, Turkish vs. Korean Bora, Israeli vs. Nordic Eli, and Slavic vs. Japanese Renko. Ethnea and Genni 2.0 are available at http://abel.lis.illinois.eduSubmitted by Vetle Torvik ([email protected]) on 2016-03-01T22:17:31Z
No. of bitstreams: 1
ethnea.pdf: 37528 bytes, checksum: 9e335dd76af81c5c3d9de0503f06627c (MD5)Made available in DSpace on 2016-03-01T22:17:32Z (GMT). No. of bitstreams: 1
ethnea.pdf: 37528 bytes, checksum: 9e335dd76af81c5c3d9de0503f06627c (MD5)
Previous issue date: 2016-03NIH P01AG039347NSF 1348742Ope
3D Printing with Bioplastics
No full textAdditive Manufacturing (AM) is undergoing a radical evolution. AM businesses such as Ultimaker (UM) are speeding up industrial production through digital design and local manufacturing to enable industries to produce “what they need, where they need it, and when they need it” (“Ultimaker”, 2019), while also being cost-effective. AM is perceived as a key sustainable technology as it enables efficient design and is believed to make less waste (“AMFG”, 2020), thus putting Ultimaker in a position to offer sustainability enhancements for their clients’ manufacturing processes. One topic of debate for AM sustainability, and the topic of investigation for this thesis, is whether bioplastics are more sustainable than fossil-based plastics for Fused Depositon Modeling (FDM) 3D Printing. Although PLA, a commonly used FDM material, is bio-based, it was hitherto unclear how much using this material and other BBPs can reduce the ecological impact of the 3D printing (3DP) process. This investigation was conducted in three phases- First, gaining an understanding of the context through literature review, market analysis and expert interviews. Second, material tests conducted to compare energy use and material properties of 3DP filaments. Third, a synthesis of findings from the first two phases into a material guide and recommendations for reducing the environmental impact of 3DPrinting. Whereas polymers are classified as bio-based/fossil-based and biodegradable/non-biodegradable, the 3DP filament materials available in the market often contain additives, fillers, or other polymers which make them difficult to categorize in a single type (Rohringer, 2020). Hence, a variety of polymers were selected for conducting material studies- including 3 UM-standard filaments, and 5 new filaments. Both environmental and functional properties were studied. For environmental impacts, literature showed that across the different parts of the 3DP filament life cycle, electricity use of the printer is the biggest contributor to ecological impact (Faludi et al., 2015). This motivated the investigation of energy use of a UM printer while printing selected materials. For functionality, expert interviews highlighted tensile properties, dimensional accuracy, and ease of printing as the most important criteria in the material selection process- thus motivating comparison tests for the same. An energy use comparison test revealed that electricity use is mainly influenced by build plate heating. More research is recommended to minimize build-plate heating for UM printers through solutions such as insulating the build chamber, or localized heating of build plate. The print quality and tensile tests affirm BIOPETG as a potential drop in replacement for UM-CPE. For both tests, new materials performed slightly worse, albeit often at acceptable levels, as compared to UM-standard materials. However, this can be attributed to the rudimentary level of print process optimization conducted for the new materials. Thus, it is recommended that these materials go through an elaborate optimization process in order to gain a more accurate impression of functional performance. As the final outcome of this investigation, the data collected was compiled into a material guide containing material properties and sustainability indicators. This visual can be referred by end-users like engineers, designers and production professionals to make appropriate material choices for their applications.Integrated Product Desig
- …
