An exploration in Ramsey theory

We present several introductory results in the realm of Ramsey Theory, a subfield of Combinatorics and Graph Theory. The proofs in this thesis revolve around identifying substructure amidst chaos. After showing the existence of Ramsey numbers of two types, we exhibit how these two numbers are related. Shifting our focus to one of the Ramsey number types, we provide an argument that establishes the exact Ramsey number for h(k, 3) for k ≥ 3; this result is the highlight of this thesis. We conclude with facts that begin to establish lower bounds on these types of Ramsey numbers for graphs requiring more substructure

Out-of-plane electron transport in finite layer MoS2

Ballistic electron emission microscopy (BEEM) has been used to study the processes affecting electron transport along the [0001] direction of finite layer MoS2 flakes deposited onto the surface of Au/Si(001) Schottky diodes. Prominent features present in the differential spectra from the MoS2 flakes are consistent with the density of states of finite layer MoS2 calculated using density functional theory. The ability to observe the electronic structure of the MoS2 appears to be due to the relatively smooth density of states of Si in this energy range and a substantial amount of elastic or quasi-elastic scattering along the MoS2/Au/Si(001) path. Demonstration of these measurements using BEEM suggests that this technique could potentially be used to study electron transport through van der Waals heterostructures, with applications in a number of electronic devices

Exploration of counter examples of balanced sets

Mathematicians are often intrigued with patterns, many times finding themselves looking for pieces of structure within a data set. This research project is no different in that we have explored our vast data set for substructure. Our goal is to identify the following: how many data points are necessary to guarantee our set has a balanced set/substructure? Naturally rephrasing the previous question, we also ask ourselves what is the largest set that does not have a balanced subset/substructure? This alternate phrasing set us down our current path. We focused on the largest sets with no balanced substructure and what they look like. After brute force checking all Z5 × Z5 maximal sets, we found 7 nonisomorphic graphs that did not have balanced substructure. Using those examples as starting points, we then extended into Z7 × Z7. When successful, our goal was to classify examples in Zp × Zp which have no balanced substructure. Currently, we believe there are four classifications of maximal sets with no balance substructure for any Zp × Zp. The main proof to follow focuses on one of these classifications called Kick I

“Lessons that simply cannot be lectured”: Highlighting the experiences and benefits of undergraduates engaged in community psychology research

Globally, Community Psychology (CP) currently struggles with a lack of visibility and a shortage of platforms from which to engage future researchers and practitioners. Many of these future researchers and practitioners study psychology as part of their undergraduate education, making psychology departments in undergraduate institutions an ideal point of exposure. Discouragingly, however, undergraduate students are unlikely to be exposed to CP in their course curriculums forcing students to seek out opportunities for exposure elsewhere (Jimenez, 2016; Glantsman, McMahon & Njoku et al., 2015). This is especially true of Community Psychology within the United States. This study aimed to explore how students got involved in CP research and the benefits of that involvement. A total of 34 former undergraduate research assistants involved in CP research teams at Michigan State University completed a 20-item online questionnaire comprised of open- and closed-ended questions. Quantitative data were analyzed descriptively and qualitative data were analyzed using an iterative coding process. Results showed that the majority of students had no experience in CP and merely stumbled upon the research. Despite this, respondents reported gaining many skills, competencies, and knowledge during their time on the research teams. Respondents particularly benefited from: 1) gaining hands-on and community-based research skills; 2) attaining transferable skills they could carry with them in future positions; 3) acquiring CP-specific competencies; and 4) cultivating greater awareness and passion for social issues. Finally, the majority of respondents discussed how their involvement on CP research teams honed in their interest and passions and/or shaped their professional trajectory.  These findings provide preliminary evidence of the benefits of CP research involvement at an undergraduate level and has important implications for how CP as a field may choose to invest in undergraduate research opportunities.&nbsp

“Lessons that simply cannot be lectured”: Highlighting the experiences and benefits of undergraduates engaged in community psychology research

Globally, Community Psychology (CP) currently struggles with a lack of visibility and a shortage of platforms from which to engage future researchers and practitioners. Many of these future researchers and practitioners study psychology as part of their undergraduate education, making psychology departments in undergraduate institutions an ideal point of exposure. Discouragingly, however, undergraduate students are unlikely to be exposed to CP in their course curriculums forcing students to seek out opportunities for exposure elsewhere (Jimenez, 2016; Glantsman, McMahon & Njoku et al., 2015). This is especially true of Community Psychology within the United States. This study aimed to explore how students got involved in CP research and the benefits of that involvement. A total of 34 former undergraduate research assistants involved in CP research teams at Michigan State University completed a 20-item online questionnaire comprised of open- and closed-ended questions. Quantitative data were analyzed descriptively and qualitative data were analyzed using an iterative coding process. Results showed that the majority of students had no experience in CP and merely stumbled upon the research. Despite this, respondents reported gaining many skills, competencies, and knowledge during their time on the research teams. Respondents particularly benefited from: 1) gaining hands-on and community-based research skills; 2) attaining transferable skills they could carry with them in future positions; 3) acquiring CP-specific competencies; and 4) cultivating greater awareness and passion for social issues. Finally, the majority of respondents discussed how their involvement on CP research teams honed in their interest and passions and/or shaped their professional trajectory.  These findings provide preliminary evidence of the benefits of CP research involvement at an undergraduate level and has important implications for how CP as a field may choose to invest in undergraduate research opportunities.&nbsp

Emergence of the persistent spin helix in semiconductor quantum wells

According to Noethers theorem, for every symmetry in nature there is a corresponding conservation law. For example, invariance with respect to spatial translation corresponds to conservation of momentum. In another well-known example, invariance with respect to rotation of the electrons spin, or SU(2) symmetry, leads to conservation of spin polarization. For electrons in a solid, this symmetry is ordinarily broken by spin-orbit coupling, allowing spin angular momentum to flow to orbital angular momentum. However, it has recently been predicted that SU(2) can be achieved in a two-dimensional electron gas, despite the presence of spin-orbit coupling. The corresponding conserved quantities include the amplitude and phase of a helical spin density wave termed the persistent spin helix. SU(2) is realized, in principle, when the strength of two dominant spin-orbit interactions, the Rashba (strength parameterized by \alpha) and linear Dresselhaus (\beta_1), are equal. This symmetry is predicted to be robust against all forms of spin-independent scattering, including electron-electron interactions, but is broken by the cubic Dresselhaus term (\beta_3) and spin-dependent scattering. When these terms are negligible, the distance over which spin information can propagate is predicted to diverge as \alpha approaches \beta_1. Here we observe experimentally the emergence of the persistent spin helix in GaAs quantum wells by independently tuning \alpha and \beta_1. Using transient spin-grating spectroscopy, we find a spin-lifetime enhancement of two orders of magnitude near the symmetry point.........Comment: Will be published in Nature on April 2, 200

Deer mouse hemoglobin exhibits a lowered oxygen affinity owing to mobility of the E helix. Corrigendum

In the article by Inoguchi et al. (2013) the affiliation for two of the authors, Angela Fago and Roy E. Weber, was given incorrectly. The correct affiliation is Zoophysiology, Department of Bioscience, Aarhus University, Aarhus, Denmark

Deer mouse hemoglobin exhibits a lowered oxygen affinity owing to mobility of the E helix

The deer mouse, Peromyscus maniculatus, exhibits altitude-associated variation in hemoglobin oxygen affinity. To examine the structural basis of this functional variation, the structure of the hemoglobin was solved. Recombinant hemoglobin was expressed in Escherichia coli and was purified by ion-exchange chromatography. Recombinant hemoglobin was crystallized by the hangingdrop vapor-diffusion method using polyethylene glycol as a precipitant. The obtained orthorhombic crystal contained two subunits in the asymmetric unit. The refined structure was interpreted as the aquo-met form. Structural comparisons were performed among hemoglobins from deer mouse, house mouse and human. In contrast to human hemoglobin, deer mouse hemoglobin lacks the hydrogen bond between α1Trp14 in the A helix and α1Thr67 in the E helix owing to the Thr67Ala substitution. In addition, deer mouse hemoglobin has a unique hydrogen bond at the α1β1 interface between residues α1Cys34 and β1Ser128

Nerfstudio: A Modular Framework for Neural Radiance Field Development

Neural Radiance Fields (NeRF) are a rapidly growing area of research with wide-ranging applications in computer vision, graphics, robotics, and more. In order to streamline the development and deployment of NeRF research, we propose a modular PyTorch framework, Nerfstudio. Our framework includes plug-and-play components for implementing NeRF-based methods, which make it easy for researchers and practitioners to incorporate NeRF into their projects. Additionally, the modular design enables support for extensive real-time visualization tools, streamlined pipelines for importing captured in-the-wild data, and tools for exporting to video, point cloud and mesh representations. The modularity of Nerfstudio enables the development of Nerfacto, our method that combines components from recent papers to achieve a balance between speed and quality, while also remaining flexible to future modifications. To promote community-driven development, all associated code and data are made publicly available with open-source licensing at https://nerf.studio.Comment: Project page at https://nerf.studi

Conferencing the international at the World Pacifist Meeting in India, 1949

This paper considers how the act of conferencing was central to imagining, negotiating and contesting post-war pacifism as an internationalist project. The paper contends that internationalism and the international conference are inexorably entwined. Through studying the conference geographers can explore the situated historical and political geographies of internationalism which belies its otherwise transcendent or universalist claims. A reading of the 1949 World Pacifist Meeting in India is used to make two key arguments. Firstly, it shows how conferences operate as stage-managed events through which to script and perform an alternative vision of internationalism. Half conference, half pilgrimage, the global composition of delegates was arranged to suggest a space ‘singularly free from any sense of geographical limitation’. Yet total immersion in the rich cultural and historical context of India marked an uneven internationalist arena, where the ‘Land of Gandhi’ was held with unparalleled revere. Secondly, whilst geographers and others have turned to conferencing in recent years, this has largely been contained to ‘summitry’ and high-end diplomacy. This paper calls for geographers to consider a wider range of conferencing spaces and practices, and argues that studying ‘other conferences’ by necessity opens up consideration of other forms of internationalism. The paper concludes that the World Pacifist Meeting’s delegates imagined an alternative form of internationalism, exemplified by an alternative form of international conference, which sought to challenge state-centric readings of global power relations