Localized Stress Fluctuations Drive Shear Thickening in Dense Suspensions

The mechanical response of solid particles dispersed in a Newtonian fluid exhibits a wide range of nonlinear phenomena including a dramatic increase in the viscosity \cite{1-3} with increasing stress. If the volume fraction of the solid phase is moderately high, the suspension will undergo continuous shear thickening (CST), where the suspension viscosity increases smoothly with applied shear stress; at still higher volume fractions the suspension can display discontinuous shear thickening (DST), where the viscosity changes abruptly over several orders of magnitude upon increasing applied stress. Proposed models to explain this phenomenon are based in two distinct types of particle interactions, hydrodynamic\cite{2,4,5} and frictional\cite{6-10}. In both cases, the increase in the bulk viscosity is attributed to some form of localized clustering\cite{11,12}. However, the physical properties and dynamical behavior of these heterogeneities remains unclear. Here we show that continuous shear thickening originates from dynamic localized well defined regions of particles with a high viscosity that increases rapidly with concentration. Furthermore, we find that the spatial extent of these regions is largely determined by the distance between the shearing surfaces. Our results demonstrate that continuous shear thickening arises from increasingly frequent localized discontinuous transitions between coexisting low and high viscosity Newtonian fluid phases. Our results provide a critical physical link between the microscopic dynamical processes that determine particle interactions and bulk rheological response of shear thickened fluids

The art of the *engaging* video in science education

Using pre-recorded videos for content delivery in online or blended courses (or as a supplement to in-person courses), offers several advantages for students compared to synchronous lectures, including increased accessibility, adaptable pacing, and the flexibility to re-watch as needed. For instructors, it provides advantages in terms of increased re-useability and consistency across sections, editing/trimming of mistakes, and extended reach with no limit to the number of possible viewers. However, watching videos is typically a passive process that does not require students to engage with the material or each other. Since active engagement is well-established as providing a superior learning experience compared to passive watching and listening, this raises the question of whether it’s possible to produce videos that also promote active learning, in order to get the best of both worlds. This workshop is all about bringing together the best tips, tools and lessons learned in our science education community on how to make fun and engaging educational videos for our courses, without requiring excessive time, resources or technical expertise to produce. We\u27ll discuss the challenges and pitfalls of different types of videos, strategies to successfully overcome those difficulties, evidence of student learning, and the personal outcomes we\u27ve experienced from these efforts. The goal for this session will be to create a collaborative cheat sheet of best practices, principles, and available tools to enhance the quality and efficiency of our educational videography

Conceptual design of a fleet of autonomous regolith throwing devices for radiation shielding of lunar habitats

The National Aeronautics and Space Administration (NASA) in conjunction with Universities Space Research Association (USRA) has requested that the feasibility of a fleet of regolith tossing devices designed to cover a lunar habitat for radiation protection be demonstrated. The regolith, or lunar soil, protects the lunar habitat and its inhabitants from radiation. Ideally, the device will operate autonomously in the lunar environment. To prove the feasibility of throwing regolith on the Moon, throwing solutions were compared to traditional, Earth-based methods for moving soil. Various throwing configurations were investigated. A linear throwing motion combined with a spring and motor energizing system proved a superior solution. Three different overall configurations for the lunar device are presented. A single configuration is chosen and critical parameters such as operating procedure, system volume, mass, and power are developed. The report is divided into seven main sections. First, the Introduction section gives background information, defines the project requirements and the design criteria, and presents the methodology used for the completion of this design. Next, the Preliminary Analysis section presents background information on characteristics of lunar habitats and the lunar environment. Then, the Alternate Designs section presents alternate solutions to each of the critical functions of the device. Fourth, a detailed analysis of throwing the regolith is done to demonstrate its feasibility. Then, the three overall design configurations are presented. Next, a configuration is selected and the conceptual design is expanded to include system performance characteristics, size, and mass. Finally, the Conclusions and Recommendations for Future Work section evaluates the design, outlines the next step to be taken in the design process, and suggests possible goals for future design work

Understanding Recent Spikes and Longer Trends in American Murders

On September 7, 2016, four of the nation’s newspapers of record weighed in on the connected crises in crime and policing. The New York Times revealed the tensions between the Mayor’s office in Chicago and several community and professional groups over a plan to overhaul Chicago’s police disciplinary board – a plan developed in the wake of the shooting of an unarmed teenager, Laquan McDonald, and the release of a video of that killing. The Wall Street Journal related a vigorous defense of New York City’s “broken windows” policing strategy – a strategy that has been a recurring source of tension between the city’s minority communities and the police, and whose value in crime reduction has been sharply debated. The Washington Post’s lead editorial decried Chicago’s “deadliest month in two decades” that left city officials at odds over the basic elements of public safety policy and strategic responses to the seemingly intractable violence. The Chicago Tribune weighed in as well. In it, Chicago Police Superintendent Eddie Johnson declared that the crisis is “not a police issue, it’s a society issue,” pointing to the need for stricter gun controls

Quick Guide To Quattro Pro for Windows: For Mouse Users

Research Methods/ Statistical Methods,

From Superman to Brahman: The Religious Shift of The Matrix Mythology

In this article, we argue two points: 1) that the religious images, symbols and allusions of The Matrix mythology shift decidedly from the West to the East; and 2) that the Western end of this shift is grounded not in the Christian religious tradition, but in Nietzschean humanism. This humanism explicit in the opening lines of the history of the Matrix myth, as found in The Animatrix, retains its dominance through The Matrix and into Reloaded, at which point the myth turns increasingly eastward and ends in the cyclical images of Vedic and Puranic creation and dissolution

Terminal Sterilization of Anterior Cruciate Ligament (ACL) Allografts: A Systematic Review of Outcomes

Introduction. Anterior cruciate ligament (ACL) injuries are common and reconstruction can be completed with either autograft or allograft tissue. However, there is concern about an increased failure rate with allograft tissue. The purpose of this study was to systematically review the available evidence to determine the effect of irradiation and level of dose on the failure rates of allograft in ACL reconstruction. Methods. A literature search was performed using PubMed, Scopus, and Web of Science from January 2000 to September 2013. Inclusion criteria consisted of the following: (1) primary, unilateral, single-bundle allograft ACL procedure, (2) studies with data documenting graft type and terminal sterilization technique, (3) subjective assessments of outcome, and (4) objective assessments of outcome. Studies without reported subjective and objective outcomes and those pertaining to revision ACL reconstruction were excluded. Failures were defined and compared between irradiated and non-irradiated grafts, as well as between grafts irradiated with 1.2 - 1.8 Mrad and those with 2.0 - 2.5 Mrad. Results. Of the 242 articles identified via initial search, 17 studies met the final inclusion criteria. A total of 1,090 patients were evaluated in this study, all having undergone unilateral primary ACL reconstruction with allograft tissue with 155 failures. The failure rate between non-irradiated (98/687, 14.7%) and irradiated (57/408, 14.0%) was not statistically significant (p = 0.86). Grafts in the high-dose irradiation group (27/135, 20.0%) had a statistically significant higher (p < 0.001) rate of failure than those in the low-dose irradiation group (30/273, 10.6%). Conclusion. The irradiation of an allograft increases the risk of failure after an ACL reconstruction but the use of lower doses of radiation decreases that risk

Economic analysis of flood and center pivot irrigation system modifications, An

Presented at the Central Plains irrigation short course and exposition on February 4, 1997 at the Colby Community Building in Colby, Kansas.Includes bibliographical references.An after-tax net present value(NPV) analysis of investing in three irrigation system modifications for the production of corn, grain sorghum, wheat, and alfalfa is conducted. Modifying a high pressure center pivot with low-drift nozzles and adding surge valves to a gated pipe system is economically feasible for each crop

Multisensory Integration Sites Identified by Perception of Spatial Wavelet Filtered Visual Speech Gesture Information

Perception of speech is improved when presentation of the audio signal is accompanied by concordant visual speech gesture information. This enhancement is most prevalent when the audio signal is degraded. One potential means by which the brain affords perceptual enhancement is thought to be through the integration of concordant information from multiple sensory channels in a common site of convergence, multisensory integration (MSI) sites. Some studies have identified potential sites in the superior temporal gyrus/sulcus (STG/S) that are responsive to multisensory information from the auditory speech signal and visual speech movement. One limitation of these studies is that they do not control for activity resulting from attentional modulation cued by such things as visual information signaling the onsets and offsets of the acoustic speech signal, as well as activity resulting from MSI of properties of the auditory speech signal with aspects of gross visual motion that are not specific to place of articulation information. This fMRI experiment uses spatial wavelet bandpass filtered Japanese sentences presented with background multispeaker audio noise to discern brain activity reflecting MSI induced by auditory and visual correspondence of place of articulation information that controls for activity resulting from the above-mentioned factors. The experiment consists of a low-frequency (LF) filtered condition containing gross visual motion of the lips, jaw, and head without specific place of articulation information, a midfrequency (MF) filtered condition containing place of articulation information, and an unfiltered (UF) condition. Sites of MSI selectively induced by auditory and visual correspondence of place of articulation information were determined by the presence of activity for both the MF and UF conditions relative to the LF condition. Based on these criteria, sites of MSI were found predominantly in the left middle temporal gyrus (MTG), and the left STG/S (including the auditory cortex). By controlling for additional factors that could also induce greater activity resulting from visual motion information, this study identifies potential MSI sites that we believe are involved with improved speech perception intelligibility