1,721,079 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Identification Of A Critical Intermediate In Galvanic Exchange Reactions By Single-nanoparticle Resolved Kinetics
Get PDF\begin{wrapfigure}{r}{0pt}
\includegraphics[scale=0.25]{Graph2.eps}
\end{wrapfigure}
The realization of common materials transformations in nanocrystalline systems is fostering the development of novel nanostructures and allowing a deep look into the atomistic mechanisms involved. Galvanic corrosion is one such transformation. We studied galvanic replacement within individual metal nanoparticles by using plasmonic spectroscopy. This proved to be a powerful approach to studying materials transformations in the absence of ensemble averaging. Individual nanoscale units act as domains that can be interrogated optically in isolation, whereas the averaging of all such domains provides a bulk reaction trajectory. Single-nanoparticle reaction trajectories showed that a Ag nanoparticle exposed to Au makes an abrupt transition into a nanocage structure. The transition is limited by a critical structural event, which we identified by electron microscopy to comprise the formation of a nanosized void, similar to the pitting process commonly observed in the corrosion of metals. Trajectories also revealed a surprisingly strong nonlinearity of the reaction kinetics, which we explain by a model involving the critical coalescence of vacancies into a growing void. The critical void size for galvanic exchange to spontaneously proceed was found to be 20 atomic vacancies. In the future we hope to extend this approach to examine a wide variety of materials transformations and chemical reactions.Made available in DSpace on 2014-09-17T16:55:01Z (GMT). No. of bitstreams: 3
license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5)
16.pdf: 272027 bytes, checksum: 542037d32cb66b50e5a71356a81b4078 (MD5)
abstract.txt: 1753 bytes, checksum: ab435bf52be9093926b218e12b9ef2da (MD5)
Previous issue date: 2014-06-17Made available in DSpace on 2015-04-14T18:40:47Z (GMT). No. of bitstreams: 4
license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5)
TH09_Presentation.pptx: 59394860 bytes, checksum: 2f2e1b6fe42715003c68083f69b59582 (MD5)
TH09_Abstract.pdf: 272027 bytes, checksum: 542037d32cb66b50e5a71356a81b4078 (MD5)
TH09_Abstract.txt: 1753 bytes, checksum: ab435bf52be9093926b218e12b9ef2da (MD5)
Previous issue date: 2014-06-1
Detection of water binding to the oxygen evolving complex using low frequency SERS
Get PDFMade available in DSpace on 2017-07-27T20:15:33Z (GMT). No. of bitstreams: 2
2668.pdf: 13449 bytes, checksum: 24edc5194206c8c32aa289a74b3829fd (MD5)
license.txt: 4814 bytes, checksum: a3dad671d2baf2db10a2bec0f2e0c408 (MD5)
Previous issue date: 6Made available in DSpace on 2018-01-29T23:06:07Z (GMT). No. of bitstreams: 3
license.txt: 4814 bytes, checksum: a3dad671d2baf2db10a2bec0f2e0c408 (MD5)
2668.pdf: 13449 bytes, checksum: 24edc5194206c8c32aa289a74b3829fd (MD5)
979156.pptx: 11817862 bytes, checksum: f5c2315dd9d79c0408a043c27ac78e5e (MD5)
Previous issue date: 6The oxygen evolving complex (OEC) in Photosystem II (PSII) is a hallmark catalyst for efficiently splitting water to generate molecular oxygen. Much of what is known about the structure of the OEC has been provided by X-ray analysis of PSII at low temperatures, from which the mechanism of water splitting has been inferred. Surface-enhanced Raman scattering (SERS) offers an opportunity to build on our current understanding of this catalytic system as it can provide time-resolved, molecular vibrational information in a physiological environment. With low frequency SERS, we are able to separate the manganese oxide vibrational modes of the OEC from those in a complex, biological environment. With isotopically labelled water, we use SERS to identify water binding to the OEC. Raman spectra calculated by density functional theory support the assignment of water binding to a manganese atom outside of the cuboidal OEC. Detection of water binding sites on the OEC with SERS can not only compliment previous structural studies, but can also provide a powerful platform for in operando mechanistic studies
In-situ generated graphene as the catalytic site for visible-light mediated ethylene epoxidation on Ag nanocatalysts
Get PDFMade available in DSpace on 2018-01-29T23:03:16Z (GMT). No. of bitstreams: 3
license.txt: 4814 bytes, checksum: a3dad671d2baf2db10a2bec0f2e0c408 (MD5)
2590.pdf: 14814 bytes, checksum: effac3901766cb4b76eda61deb3b33be (MD5)
950530.pptx: 16801971 bytes, checksum: e85d3fb750a900c6a5c3b1f44b76f53d (MD5)
Previous issue date: 6Made available in DSpace on 2017-07-27T20:15:24Z (GMT). No. of bitstreams: 2
2590.pdf: 14814 bytes, checksum: effac3901766cb4b76eda61deb3b33be (MD5)
license.txt: 4814 bytes, checksum: a3dad671d2baf2db10a2bec0f2e0c408 (MD5)
Previous issue date: 6Despite the harsh conditions for chemical conversion, ethylene oxide produced from ethylene epoxidation on Ag-based heterogeneous catalyst constitutes one of the largest volume chemicals in chemical industry. Recently, photocatalytic epoxidation of ethylene over plasmonic Ag nanoparticles enables the chemical conversion under significantly decreased temperature and ambient pressure conditions. Yet a detailed understanding of the photocatalytic process at the reactant/catalyst interface is under debate. Surface enhanced Raman spectroscopy (SERS) is a powerful vibrational spectroscopy technique that enables the localized detection of rare and/or transient chemical species with high sensitivity under in situ and ambient conditions. Using SERS, we are able to monitor at individual sites of an Ag nanocatalyst the visible-light-mediated adsorption and epoxidation of ethylene. From detected intermediates, we find that the primary step in the photoepoxidation is the transient formation of graphene catalyzed by the Ag surface. Density functional theory (DFT) simulations that model the observed SERS spectra suggest that the defective edge sites of the graphene formed on Ag constitute the active site for C2H4 adsorption and epoxidation. Further studies with pre-formed graphene/Ag catalyst composites confirm the indispensable role of graphene in visible-light-mediated ethylene epoxidation. Carbon is often thought to be either an innocent support or a poison for metallic catalysts; however our studies reveal a surprising role for crystalline carbon layers as potential co-catalysts. _x000d_
_x000d
Transformations in inorganic nanomaterials: role of defects, surfaces, and size
Get PDFAs our ability to synthesize and manipulate nanomaterials increases, so does our ability to investigate the properties and transformations of materials as they evolve in size from precise clusters akin to molecules to extended solids exhibiting bulk-like properties. In this thesis, we look at a how critical features of nanomaterials like size, shape, surface chemistry or ligand shell, and defect profile affect properties and transformations on the nanoscale. In Chapter 1, we investigate the mechanism of cation exchange in an ensemble of CdSe nanocrystals with Ag+ and Cu+ in solution. We find that the generation of defects induced by non-native cations is a critical intermediate in the exchange reaction and that positive co-operativity stemming from interactions between charged defects results in an abrupt chemical transformation of the entire nanocrystal, i.e. a particle-by-particle exchange rather than an atom-by-atom mechanism. In Chapter 2, we leverage the high sensitivity of excitonic absorption of ultrasmall CdSe clusters to changes in surface chemistry to optically probe cation exchange and identify a stable, long-lived intermediate in the cation exchange transformation. The stability of the intermediate was found to be dependent on the ligand coating on the initial clusters, leading to a better understanding of how ligand passivation can play a role in chemical reactions occurring at the solid-liquid interface. In Chapter 3, we probe how the optical and structural properties of the semiconductor, cuprous selenide are affected by a decrease in crystallite size and find an ultrasmall form of cuprous selenide in which a disordered phase, known to exist in the bulk at high temperature, is stable at ambient conditions suggesting that the order-to-disorder phase transition temperature is depressed in ultrasmall Cu2Se clusters. Finally, in Chapters 4 and 5, we explore how the structure of metamolecules consisting of complex assemblies of hexagonal Au nanoplates and Au nanospheres affects their localized surface plasmon resonance properties. . We find using electrodynamic simulations combined with correlated electron microscopy/optical spectroscopy at the single-construct level that the nature and strength of plasmonic coupling within the resulting assembly is strongly dependent on the site of attachment of the nanosphere/s and the nanosphere size. In addition to the large, regio-selective polarizability of Au nanoplates, we also uncover a synergy in the polarizing effect of multiple nanospheres. The dissertation ends with an outlook of the scientific impact and potential future studies that may emanate from the work presented here.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2018-05-01The student, Sarah White, accepted the attached license on 2016-04-19 at 14:13.The student, Sarah White, submitted this Dissertation for approval on 2016-04-19 at 14:30.This Dissertation was approved for publication on 2016-04-21 at 08:50.DSpace SAF Submission Ingestion Package generated from Vireo submission #9345 on 2016-07-07 at 14:17:26Made available in DSpace on 2016-07-07T21:17:46Z (GMT). No. of bitstreams: 3
WHITE-DISSERTATION-2016.pdf: 8036351 bytes, checksum: 36131fce08a5b9e75f2896356858c80f (MD5)
LICENSE.txt: 4208 bytes, checksum: 8e3d1b54595bcb4e80b1487964c9bcba (MD5)
PROQUEST_LICENSE.txt: 4554 bytes, checksum: 9658f00f87f39a2425aaffdf16ca0284 (MD5)
Previous issue date: 2016-04-21Embargo set by: Seth Robbins for item 93285
Lift date: 2018-07-07T21:18:16Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemLimited Restriction Lifted for Item 93285 on 2018-07-08T09:15:33Z
Variations on the Author
Get PDF“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
Colloidal metal-organic frameworks: synthesis and assembly
Get PDFThis thesis is an exercise in exploring the potential of metal-organic framework (MOF) as building blocks for developing anisotropic colloidal assembly system using morphology variation in general and distinct facet in particular. Our attempt to enrich the field is from two directions: synthetic development of MOF as colloidal-sized particles and mechanistic understanding of anisotropic particle assembly.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2018-08-01The student, Melinda Sindoro, accepted the attached license on 2016-05-05 at 16:00.The student, Melinda Sindoro, submitted this Dissertation for approval on 2016-05-05 at 16:05.This Dissertation was approved for publication on 2016-05-06 at 15:49.DSpace SAF Submission Ingestion Package generated from Vireo submission #9602 on 2016-11-10 at 12:18:54Made available in DSpace on 2016-11-10T18:27:16Z (GMT). No. of bitstreams: 6
SINDORO-DISSERTATION-2016.pdf: 7582497 bytes, checksum: 88821c30ca304794fa1ac95fa3522703 (MD5)
LICENSE.txt: 4212 bytes, checksum: e16976e08ea5b2e3e7dd24f66ed06416 (MD5)
Rightslink - 1.pdf: 137932 bytes, checksum: 881e825f96e669e12c6bde93c1b016e5 (MD5)
Rightslink - 2.pdf: 137891 bytes, checksum: 0c5a2321ad147e4dfc23ddb4edf3eb4f (MD5)
Rightslink - 3.pdf: 177041 bytes, checksum: ba1fb21ed6ef377a7d1423162ce50fc6 (MD5)
Rightslink - 4.pdf: 137785 bytes, checksum: d4878713422a056f098f1662db17f9d3 (MD5)
Previous issue date: 2016-05-06Embargo set by: Seth Robbins for item 95304
Lift date: 2018-11-10T18:28:02Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemLimited Restriction Lifted for Item 95304 on 2018-11-11T10:15:19Z
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Exploring condensed phases in engineered semiconducting nanocrystals
Get PDFThe Jain lab employs a topotactic method called cation exchange to produce semiconductor nanocrystals (NCs) in novel morphologies, compositions, and crystallographic phases. My dissertation research focuses on the understanding of the physical properties and phase transitions of these new nanomaterials prepared by cation exchange. In Chapter 1, I describe the countless possibilities of the exploration of physicochemical properties and applications of molecularly precise semiconductor nanoclusters, a class of materials that we were able to expand with the help of cation exchange. In Chapter 2, I discuss how ultrasmall copper selenide (Cu2-xSe) NCs prepared by cation exchange of cadmium selenide NCs exhibit a disordered cationic sub-lattice under ambient conditions. This behavior is quite unlike larger NCs or the bulk, suggesting an interesting effect of crystallite size and strain on the stability of super-ionic phases. In Chapter 3, I describe my investigations of Li-doping of Cu2-xSe NCs and how this doping influences the crystal structure and consequently the phase transition behavior. A close-to-ambient-temperature transition from the non-superionic to superionic phase transition also appears to be present in the final lithium selenide (Li2Se) NCs formed from this doping reaction. In Chapter 4, I explain on the basis of optical spectra measurements and density functional theory (DFT) calculations how HgSe NCs, prepared using cation exchange in a novel wurtzite phase, differ from their natural zinc-blende counterparts. The latter is a semi-metal, whereas the newer phase obtained from cation exchange is found to have an inverted band structure along with a finite band-gap, making it a potential 3D topological insulator. In Chapter 5, I extend the understanding of ion exchange reactions to an “anion exchange” process in zinc oxide (ZnO) NCs. As a detour from the central thesis of my dissertation, in Chapter 6, I present my work on electrodynamic simulations of optical properties of nanostructures, which helped demonstrate that localized surface plasmons can be imaged in real space with nanometer resolution using a scanning tunneling microscope (STM) coupled to a laser.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2020-12-01The student, Progna Banerjee, accepted the attached license on 2018-11-23 at 13:07.The student, Progna Banerjee, submitted this Dissertation for approval on 2018-11-23 at 13:29.This Dissertation was approved for publication on 2018-11-27 at 08:38.DSpace SAF Submission Ingestion Package generated from Vireo submission #13088 on 2019-02-08 at 11:38:51Made available in DSpace on 2019-02-08T18:39:46Z (GMT). No. of bitstreams: 4
BANERJEE-DISSERTATION-2018.pdf: 18102144 bytes, checksum: c620cd9fe8819a563baae4e216a14039 (MD5)
Banerjee_Progna_2018_phd.docx: 41055308 bytes, checksum: 8bcc235b597de7589eddfd7e740692f9 (MD5)
LICENSE.txt: 4212 bytes, checksum: bdd135dfa8247b446c7bc4b6fd7ee448 (MD5)
PROQUEST_LICENSE.txt: 4558 bytes, checksum: ae3dc0a3b06a054cb97a8ad3e4f22440 (MD5)
Previous issue date: 2018-11-27Embargo set by: Seth Robbins for item 109937
Lift date: 2021-02-08T18:40:00Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 109937
Lift date: 2021-02-08T18:42:23Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 109937
Lift date: 2021-02-08T18:43:54Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 109937
Lift date: 2021-02-08T18:44:50Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemLimited Restriction Lifted for Item 109937 on 2021-02-09T10:15:34Z
- …
