The role of inertia in extensional fall of a viscous drop

In flows of very viscous fluids, it is often justifiable to neglect inertia and solve the resulting creeping-flow or Stokes equations. For drops hanging beneath a fixed wall and extending under gravity from an initial rest state, an inevitable consequence of neglect of inertia and surface tension is that the drop formally becomes infinite in length at a finite crisis time, at which time the acceleration of the drop, which has been assumed small relative to gravity g, formally also becomes infinite. This is a physical impossibility, and the acceleration must in fact approach the (finite) free-fall value g. However, we verify here, by a full Navier–Stokes computation and also with a slender-drop approximation, that the crisis time is a good estimate of the time at which the bulk of the drop goes into free fall. We also show that the drop shape at the crisis time is a good approximation to the final shape of the freely falling drop, prior to smoothing by surface tension. Additionally, we verify that the drop has an initial acceleration of g, which quickly decreases as viscous forces in the drop become dominant during the early stages of fall.Y. M. Stokes and E. O. Tuc

Exact and semiclassical approach to a class of singular integral operators arising in fluid mechanics and quantum field theory

A class of singular integral operators, encompassing two physically relevant cases arising in perturbative QCD and in classical fluid dynamics, is presented and analyzed. It is shown that three special values of the parameters allow for an exact eigenfunction expansion; these can be associated to Riemannian symmetric spaces of rank one with positive, negative or vanishing curvature. For all other cases an accurate semiclassical approximation is derived, based on the identification of the operators with a peculiar Schroedinger-like operator.Comment: 12 pages, 1 figure, amslatex, bibtex (added missing label eq.11

A Linguistic Phenomenon: Code-Switching in Media and Advertisement

The purpose of this paper is to examine the linguistic phenomenon of code-switching in two different forms of communication: social media and traditional advertising. Code-switching, most common among bilinguals, is the practice of expressing ourselves in conversation, the act of altering the languages we speak, or the ability to switch back and forth between two different languages simultaneously. We all do it, albeit, inadvertently at times, whether it is to fit in, stand out, be understood, emphasize a point, or deliver a message. Throughout this paper, I will analyze code-switching found in a popular actress’ social media account as well as its presence in global marketing advertisements, and thus, determine why code-switching has become the intensively researched linguistic phenomenon that it is today

A laminar roughness boundary condition

A modified slip boundary condition is obtained to represent the effects of small roughness-like perturbations to an otherwise-plane fixed wall which is acting as a boundary to steady laminar flow of a viscous fluid. In its simplest form, for low local Reynolds number and small roughness slope, this boundary condition involves a constant apparent backflow at the mean surface or, equivalently, represents a shift of the apparent plane boundary toward the flow domain. Extensions of the theory are also made to include finite local Reynolds number and finite roughness slope.E. O. Tuck and A. Kouzoubo

Femina Furisoa: Female Arena Performers and Their Role in Ancient Roman Spectacle

This thesis looks at what motivated elite males to include female arena performers, when male performers were the norm. This study will also look at the different ways in which female arena performers were presented for the audience and unpack why those personas were chosen for them. Gender, sexuality, and exotic ethnicities were all highlighted in the case of the female arena performer. What messaging was being sent to the spectators and how did it serve the sponsors to do so? The goal for the elite male sponsors was to gain favour with the people to increase his reputation, gain political support that would impact the trajectory of his political career, and to positively affect his legacy

Root Senescence in Red Clover (\u3cem\u3eTrifolium Pratense\u3c/em\u3e L.)

Legume root systems form a mosaic of living, ageing and dead roots and nodules. The balance between these stages alters during plant development. Stressful events (drought, temperature change, reduced carbon supply, etc.) disturb the balance (Butler et al., 1959). Effects of root and nodule death on soil structure, composition and leaching and on plant persistency are understood poorly. Plants with differing senescence patterns are useful tools to study these effects. Molecular studies of root senescence need detailed knowledge of the process and timing of root senescence and death. Biochemical and histochemical markers of senescence were used to generate preliminary results of the effects of reduced carbon input, temporary (by defoliation, D) or permanent (by defoliation and shading, DS) on red clover shoot survival and root death

Life Sciences Institute for High School Students and Teachers

A two-day institute will be developed and presented on campus in late fall or early spring semester for selected high school students and teachers. The program content and activities will be designed to focus on a theme within the Life Sciences. Each year a theme will be selected in consideration of all the programs and schools associated with the Life Sciences Initiative at VCU. This includes biology, genetics, health-care sciences, the behavioral sciences, and the integration of arts and social sciences as feasible. The institute will lead to high school students earning one undergraduate credit and teachers will earn one graduate credit for continuing education or advanced study. The program is designed to attract students to attend VCU for the Life Sciences. The high school teachers will serve as student sponsors and potential recruiters for students at their local high schools. The learning experiences will be designed so teachers can incorporate Life Sciences’ content into their high school classrooms. Given the team’s vision and mission, the proposed project is designed to enhance collaborative efforts among the Life Science disciplines and university outreach to high schools within and outside of Virginia

Visualization of defect-induced excitonic properties of the edges and grain boundaries in synthesized monolayer molybdenum disulfide

Atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDCs) are attractive materials for next generation nanoscale optoelectronic applications. Understanding nanoscale optical behavior of the edges and grain boundaries of synthetically grown TMDCs is vital for optimizing their optoelectronic properties. Elucidating the nanoscale optical properties of 2D materials through far-field optical microscopy requires a diffraction-limited optical beam diameter sub-micron in size. Here we present our experimental work on spatial photoluminescence (PL) scanning of large size ( $\geq 50$ microns) monolayer MoS$_2$ grown by chemical vapor deposition (CVD) using a diffraction limited blue laser beam spot (wavelength 405 nm) with a beam diameter as small as 200 nm allowing us to probe nanoscale excitonic phenomena which was not observed before. We have found several important features: (i) there exists a sub-micron width strip ($\sim 500$ nm) along the edges that fluoresces $\sim 1000 \%$ brighter than the region far inside; (ii) there is another brighter wide region consisting of parallel fluorescing lines ending at the corners of the zig-zag peripheral edges; (iii) there is a giant blue shifted A-excitonic peak, as large as $\sim 120$ meV, in the PL spectra from the edges. Using density functional theory calculations, we attribute this giant blue shift to the adsorption of oxygen dimers at the edges, which reduces the excitonic binding energy. Our results not only shed light on defect-induced excitonic properties, but also offer an attractive route to tailor optical properties at the TMDC edges through defect engineering.Comment: 10 pages, 4 figures in Journal of Physical Chemistry C, 201

Study of aircraft in intraurban transportation systems, volume 1

An analysis of an effective short range, high density computer transportation system for intraurban systems is presented. The seven county Detroit, Michigan, metropolitan area, was chosen as the scenario for the analysis. The study consisted of an analysis and forecast of the Detroit market through 1985, a parametric analysis of appropriate short haul aircraft concepts and associated ground systems, and a preliminary overall economic analysis of a simplified total system designed to evaluate the candidate vehicles and select the most promising VTOL and STOL aircraft. Data are also included on the impact of advanced technology on the system, the sensitivity of mission performance to changes in aircraft characteristics and system operations, and identification of key problem areas that may be improved by additional research. The approach, logic, and computer models used are adaptable to other intraurban or interurban areas

MODISTools - downloading and processing MODIS remotely sensed data in R

Remotely sensed data – available at medium to high resolution across global spatial and temporal scales – are a valuable resource for ecologists. In particular, products from NASA's MODerate-resolution Imaging Spectroradiometer (MODIS), providing twice-daily global coverage, have been widely used for ecological applications. We present MODISTools, an R package designed to improve the accessing, downloading, and processing of remotely sensed MODIS data. MODISTools automates the process of data downloading and processing from any number of locations, time periods, and MODIS products. This automation reduces the risk of human error, and the researcher effort required compared to manual per-location downloads. The package will be particularly useful for ecological studies that include multiple sites, such as meta-analyses, observation networks, and globally distributed experiments. We give examples of the simple, reproducible workflow that MODISTools provides and of the checks that are carried out in the process. The end product is in a format that is amenable to statistical modeling. We analyzed the relationship between species richness across multiple higher taxa observed at 526 sites in temperate forests and vegetation indices, measures of aboveground net primary productivity. We downloaded MODIS derived vegetation index time series for each location where the species richness had been sampled, and summarized the data into three measures: maximum time-series value, temporal mean, and temporal variability. On average, species richness covaried positively with our vegetation index measures. Different higher taxa show different positive relationships with vegetation indices. Models had high R2 values, suggesting higher taxon identity and a gradient of vegetation index together explain most of the variation in species richness in our data. MODISTools can be used on Windows, Mac, and Linux platforms, and is available from CRAN and GitHub (https://github.com/seantuck12/MODISTools)