1,720,982 research outputs found
Assembly and self-organization of nanomaterials
No full textThe increasing interest in nanoscience and nanotechnology has prompted intense investigations into appropriate fabrication techniques. Self-organized, bottom-up growth of nanomaterials using plasma nanofabrication techniques1–10 has proven to be one of the most promising approaches for the construction of precisely tailored nanostructures (i.e., quantum dots,11–13 nanotubes,14–17 nanowires,18–20 etc.) arrays. Thus the primary aim of this chapter is to show how plasmas may be used to achieve a high level of control during the self-organized growth of a range of nanomaterials, from zero-dimensional quantum dots (Section 15.2) to one- and two-dimensional nanomaterials (Section 15.3) to nanostructured films (Section 15.4)..
Cathodic Arc Discharge for Synthesis of Carbon Nanoparticles
No full textIn this chapter, the authors report further experimental details and several physical analyses of the floating powder and propose a model for the formation mechanism. They discussed the ability to analyze carbon nanoparticle formation in terms of a charged dusty plasma process. The detected carbon nanoparticles using a Langmuir probe technique are in agreement with the presence of fullerene-sized molecules in the plasma. The plasma can also be visually observed to surround the anode, indicating the direction of plasma expansion. There is a plasma zone between electrodes surrounded by a gas bubble due to vaporization of the surrounding liquid, as the arc temperature is estimated to be around 4000 K. The extremely sharp temperature gradient in the gas bubbles emanating from the hot plasma region to the gas–water interface is essential to cause rapid solidification of the vaporized carbon. Subsequent to the formation of onions, carbon particles coagulate into larger van der Waals crystals
A hybrid particle method for the kinetic treatment of magnetized plasma sheaths
Full text linkSubmission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2022-11-15 without embargo termsThe student, Xin Zhi Tan, accepted the attached license on 2022-07-19 at 14:19.The student, Xin Zhi Tan, submitted this Thesis for approval on 2022-07-19 at 15:18.This Thesis was approved for publication on 2022-07-20 at 10:48.DSpace SAF Submission Ingestion Package generated from Vireo submission #18382 on 2022-11-15 at 18:21:43The guiding center approximation is commonly adopted in fusion particle codes to resolve the motion of charged particles in the core and at the plasma edge of a magnetic fusion device. However, the guiding center approximation does not hold in regions where the field gradients are large, such as the plasma sheath and presheath formed in front of a material surface. Here we present a new hybrid Lagrangian method, which converts the guiding center particles into finite-orbit particles once they reach a region close to the boundary, where the field gradients become large. The domain is divided into a guiding center region and a full-orbit region, and the conversion of the particle is performed both ways. We present numerical results from an implementation of this new scheme within the hPIC Particle-in-Cell developed at Illinois. We show that the approach can accurately resolve the full orbit physics of the plasma sheath, still allowing us to treat the vast majority of the plasma bulk with the usual guiding-center approximation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Initial results for dose-to-clear reduction using the integrated circuit manufacturing with plasma activated chemical treatment (IMPACT) tool
Full text linkSubmission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2025-08-01The student, Christian Williams, accepted the attached license on 2023-07-20 at 14:26.The student, Christian Williams, submitted this Thesis for approval on 2023-07-20 at 14:40.This Thesis was approved for publication on 2023-07-21 at 07:31.DSpace SAF Submission Ingestion Package generated from Vireo submission #19753 on 2023-12-04 at 17:35:59Lithographic processes have come a long way over the past couple of decades in an effort to keep up with Moore's law. Despite the many advances that have been made when it comes to the lithography aspect,(sources, optics, etc.) of semiconductor manufacturing, there are still many issues that must be addressed when it comes to the chemicals that are used in this field. This work investigated the viability of an atmospheric plasma jet (in both dielectric barrier discharge and direct-current discharge configurations) as a means to reduce the dose of light necessary to activate the chemically-amplified photoresist such that it is more easily removable through the application of a development solution. Preliminary density-functional theory (DFT) models indicated that there is a weakening of the bonds in a simple pentane structure if there is a negatively charged species that is injected near a polymer structure. Solvated electrons were thought to be the key to inducing this sort of behavior. Preliminary data showed promising results, however the change observed in the dose of light necessary to remove the photoresist were difficult to replicate. While the initial set of results was not able to be replicated, a systematic approach was developed to control and account for as many variables as possible, which will serve as the foundation for future work in the same area of research. Verification that any potential effects that were due only to the plasma and not the gas flow were performed using a rheometer, to ensure that the viscosity was not somehow altered and would therefore lead to a reduction in the film thickness. While slight differences were seen in the viscosity between the gas flow control samples and the treated/reference samples, there was no noticeable effect on the size of the transferred pattern. The side lengths of the hexagons present were measured using a D optical profilometer and then the area of the hexagon was calculated using these measurements, initially using a vacuum ultra-violet (VUV) light source as a stand-in for an extreme ultra-violet (EUV) light source while the tool was being assembled and tested. Once the EUV source was constructed, additional experiments were conducted using it as the lightography source. Because the mask that was used in the initial experiments was no longer usable due to the necessity of a zirconium EUV filter, the measurement technique to compare the treated and non-treated samples was altered such that the amount of photoresist removal was quantified through cross-sectional scanning electron microscope (SEM) images of the coated silicon wafer in conjunction with image measurement software. Future work is proposed for the improvement of the EUV source, as well as other applications in the field of semiconductor manufacturing where the IMPACT tool may have some promise
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Harnessing redox electro-sorbents and reactive separations for efficient PFAS remediation in water systems
Full text linkSubmission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2025-02-04 without embargo termsThe student, Paola Baldaguez Medina, accepted the attached license on 2024-06-15 at 08:21.The student, Paola Baldaguez Medina, submitted this Dissertation for approval on 2024-06-15 at 08:37.This Dissertation was approved for publication on 2024-06-28 at 08:57.DSpace SAF Submission Ingestion Package generated from Vireo submission #20840 on 2025-02-04 at 21:03:29Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants with profound health and ecological implications. Redox-polymer materials have emerged as promising solutions for PFAS remediation, offering tailored electrochemical approaches to tackle the challenges posed by these persistent micropollutants. In this study, we present innovative strategies utilizing redox-polymer materials for efficient PFAS removal and destruction. Our investigation begins with the selective electrochemical separation and mineralization of PFAS, particularly GenX, using a redox-copolymer composed of poly(4-methacryloyloxy-2,2,6,6-tetramethylpiperidin-1-oxyl-co-4-methacryloyloxy-2,2,6,6-tetramethylpiperidine) (PTMA-co-PTMPMA). The copolymer's amine functional groups enhance affinity towards anionic PFAS, while redox-active nitroxide radicals enable controlled adsorption and desorption under electrochemical conditions. Optimized electrochemical parameters yield enhanced kinetics and substantial uptake capacities (>475 mg/g). Further exploration focuses on evaluating PTMA-co-PTMPMA for targeted electrochemical removal of PFAS contaminants, emphasizing regeneration capabilities and transitioning to continuous flow cell configurations. The study elucidates electrochemical mechanisms governing PFAS capture and release across diverse pH and water matrices, showcasing the copolymer's efficacy under varying environmental conditions. Additionally, we investigate redox-active metallopolymers to enhance electrochemical reversibility and electrosorption uptake in PFAS remediation. Synthesized metallopolymers with tailored redox potentials demonstrate superior PFAS capture and regeneration efficiencies, highlighting structure-property relationships impacting electron density and contaminant affinity. Innovative PFAS remediation techniques are then showcased, including up-concentration and utilization of PTMA-containing polymers as adsorbents. Integration of advanced oxidative processes with boron-doped diamond (BDD) electrodes achieves complete defluorination post-up-concentration, demonstrating energy-efficient solutions for comprehensive PFAS treatment. Through these investigations, this thesis underscores the efficacy and versatility of redox-polymer materials in addressing complex PFAS contamination scenarios. These findings contribute significant insights towards advancing sustainable and efficient PFAS remediation strategies crucial for safeguarding public health and environmental integrity
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