A New Facility for Studying Shock Wave Passage over Dust Layers

To ensure safety regarding dust explosion hazards, it is important to study the dust lifting process experimentally and identify important parameters that will be valuable for development and validation of numerical predictions of this phenomenon. A new shock tube test section was developed and integrated into an existing shock tube facility. The test section allows for shadowgraph or laser scattering techniques to track dust layer particle motion. The test section is designed to handle an initial pressure of 1 atm with an incident shock wave velocity up to Mach 2 to mimic real world conditions. The test section features an easily removable dust pan and inserts to allow for adjustment of dust layer thickness. The design allows for the changing of experimental variables including initial pressure, Mach number, dust layer thickness and characteristics of the dust itself. A separate vacuum manifold was designed to protect existing equipment from negative side effects of the dust. A study was performed to demonstrate the capabilities of the new facility and to compare results with experimental trends formerly established in the literature. Forty-micron limestone dust with a layer thickness of 3.2 mm was subjected to Mach 1.22 and 1.38 shock waves, and a high-speed shadowgraph was used for flow visualization. Dust layer rise height was graphed with respect to shock wave propagation. Dust particles subjected to a Mach 1.38 shock wave rose more rapidly and to a greater height with respect to shock wave propagation than particles subjected to a Mach 1.22 shock wave. These results are in agreement with trends found in the literature, and a new area of investigation was identified

Folner tilings for actions of amenable groups

We show that every probability-measure-preserving action of a countable amenable group G can be tiled, modulo a null set, using finitely many finite subsets of G ("shapes") with prescribed approximate invariance so that the collection of tiling centers for each shape is Borel. This is a dynamical version of the Downarowicz--Huczek--Zhang tiling theorem for countable amenable groups and strengthens the Ornstein--Weiss Rokhlin lemma. As an application we prove that, for every countably infinite amenable group G, the crossed product of a generic free minimal action of G on the Cantor set is Z-stable.Comment: Minor revisions. Final versio

THE ECONOMIC MAJOR: WHO OFFERS IT AND WHAT IS REQUIRED OF STUDENTS?

This paper econometrically investigates what variables impact the probability a college/university offers an undergraduate major in economics, multiple tracks within the major, or economics minor. Data is collected from four-year, comprehensive institutions, with control variables accounting for whether the school is public, year founded, enrollment, if the school offers a business degree, and selectivity measures. In addition, data is collected on the requirements of economics majors across institutions. Regression is used to determine what institutional variables influence specific track requirements, such as math/statistics, econometrics, capstone course, and internship. Given the unique data set that has been created, this paper offers new information and several conclusions about the economics major

Senior Recital: Chris Marks

Senior Recital: Chris Markshttps://digitalcommons.kennesaw.edu/musicprograms/2444/thumbnail.jp

Institutional Identity and Self-Esteem among African American Males in College

This article explores the relationship between self-esteem and institutional identity among 411 Black male college freshmen. Institutional identity, especially a sense of belonging, did correlate with self-esteem at both Historically Black Colleges and Universities (HBCUs) and Predominately White Institutions (PWIs), though for different reasons

Borel asymptotic dimension and hyperfinite equivalence relations

A long standing open problem in the theory of hyperfinite equivalence relations asks if the orbit equivalence relation generated by a Borel action of a countable amenable group is hyperfinite. In this paper we prove that this question always has a positive answer when the acting group is polycyclic, and we obtain a positive answer for all free actions of a large class of solvable groups including the Baumslag--Solitar group BS(1,2) and the lamplighter group. This marks the first time that a group of exponential volume-growth has been verified to have this property. In obtaining this result we introduce a new tool for studying Borel equivalence relations by extending Gromov's notion of asymptotic dimension to the Borel setting. We show that countable Borel equivalence relations of finite Borel asymptotic dimension are hyperfinite, and more generally we prove under a mild compatibility assumption that increasing unions of such equivalence relations are hyperfinite. As part of our main theorem, we prove for a large class of solvable groups that all of their free Borel actions have finite Borel asymptotic dimension (and finite dynamic asymptotic dimension in the case of a continuous action on a zero-dimensional space). We also provide applications to Borel chromatic numbers, Borel and continuous Folner tilings, topological dynamics, and $C^*$-algebras

Tetra­aqua­bis{μ2-2,7-bis­[(2,6-diisopropyl­phen­yl)imino­meth­yl]naphthalene-1,8-diolato}di-μ3-hydroxido-di-μ2-hydroxido-bis­(trimethyl­phosphine oxide)tetra­nickel(II)–trimethyl­phosphine oxide–diethyl ether–water (1/2/2/2)

The title complex, [Ni4(C36H40N2O2)2(OH)4(C3H9OP)2(H2O)4]·2C4H10O·2C3H9OP·2H2O, is centrosymmetric with a central core that can be described as a defect double cubane. The four metal ions in the cluster are held together by four bridging hydroxide groups. Each NiII atom adopts a distorted octa­hedral geometry

Nicotine exploits a COPI-mediated process for chaperone-mediated up-regulation of its receptors

Chronic exposure to nicotine up-regulates high sensitivity nicotinic acetylcholine receptors (nAChRs) in the brain. This up-regulation partially underlies addiction and may also contribute to protection against Parkinson’s disease. nAChRs containing the α6 subunit (α6* nAChRs) are expressed in neurons in several brain regions, but comparatively little is known about the effect of chronic nicotine on these nAChRs. We report here that nicotine up-regulates α6* nAChRs in several mouse brain regions (substantia nigra pars compacta, ventral tegmental area, medial habenula, and superior colliculus) and in neuroblastoma 2a cells. We present evidence that a coat protein complex I (COPI)-mediated process mediates this up-regulation of α6* or α4* nAChRs but does not participate in basal trafficking. We show that α6β2β3 nAChR up-regulation is prevented by mutating a putative COPI-binding motif in the β3 subunit or by inhibiting COPI. Similarly, a COPI-dependent process is required for up-regulation of α4β2 nAChRs by chronic nicotine but not for basal trafficking. Mutation of the putative COPI-binding motif or inhibition of COPI also results in reduced normalized Förster resonance energy transfer between α6β2β3 nAChRs and εCOP subunits. The discovery that nicotine exploits a COPI-dependent process to chaperone high sensitivity nAChRs is novel and suggests that this may be a common mechanism in the up-regulation of nAChRs in response to chronic nicotine