The visual boundary of Z^2

We introduce ideas from geometric group theory related to boundaries of groups. This is a mostly expository paper. We consider the visual boundary of a free abelian group, and show that it is an uncountable set with the trivial topology

Evaluating Future Dangerousness and Need for Treatment: The Roles of Expert Testimony, Attributional Complexity, and Victim Type

In the current study, we explored the effect of risk-assessment testimony, attributional complexity, and victim type on participants’ perceptions of the dangerousness of a sexually violent person and his need for treatment. Participants read details of a hypothetical sexual assault of a female minor and of an adult. Expert testimony of his risk assessment consisted of clinical opinion versus structured-clinical judgment (SCJ) versus actuarial assessment. Participants perceived clinical-opinion and SCJ testimony as equally influential when forming judgments of future dangerousness. In the context of treatment, however, participants relied on actuarial testimony when judging potential for risk. In addition, attributional complexity (AC) moderated perceptions of sexual risk. Overall, results point to the need for continued refinement of assessment techniques when determining dangerousness and need for treatment

An Examination of the Individual and Contextual Characteristics Associated with Active Shooter Events

In recent years, the US has experienced a substantial number of mass shooting incidents. This type of shooting incident has been termed “active shooter event” and encompasses shootings that occur in school settings as well as public settings and workplace venues. Much of the recent published literature addressing active shooter events appears to focus on tactical issues, such as training for and responding to this type of incident. Very little research, however, has examined the individual and contextual characteristics associated with active shooter events. In the current study we examine a number of factors related to 88 active shooting events involving 92 perpetrators. Our findings indicate a history of psychological and behavioral issues reported in more than 50% of the active shooters studied. In addition, 60% of shooters had evidence of additional stressors beyond those associated with psychological and behavioral issues. These findings highlight the need to continue to explore potential risk factors associated with this form of violence

Inertial frames without the relativity principle

Ever since the work of von Ignatowsky circa 1910 it has been known (if not always widely appreciated) that the relativity principle, combined with the basic and fundamental physical assumptions of locality, linearity, and isotropy, leads almost uniquely to either the Lorentz transformations of special relativity or to Galileo's transformations of classical Newtonian mechanics. Thus, if one wishes to entertain the possibility of Lorentz symmetry breaking within the context of the class of local physical theories, then it seems likely that one will have to abandon (or at the very least grossly modify) the relativity principle. Working within the framework of local physics, we reassess the notion of spacetime transformations between inertial frames in the absence of the relativity principle, arguing that significant and nontrivial physics can still be extracted as long as the transformations are at least linear. An interesting technical aspect of the analysis is that the transformations now form a groupoid/pseudo-group --- it is this technical point that permits one to evade the von Ignatowsky argument. Even in the absence of a relativity principle we can nevertheless deduce clear and compelling rules for the transformation of space and time, rules for the composition of 3-velocities, and rules for the transformation of energy and momentum. As part of the analysis we identify two particularly elegant and physically compelling models implementing "minimalist" violations of Lorentz invariance --- in the first of these minimalist models all Lorentz violations are confined to carefully delineated particle physics sub-sectors, while the second minimalist Lorentz-violating model depends on one free function of absolute velocity, but otherwise preserves as much as possible of standard Lorentz invariant physics.Comment: V1: 42 pages; V2: now 43 pages; added 8 references, added brief discussion of Carroll kinematics, added brief discussion of Robertson-Mansouri-Sexl framework, added various minor clarifications. V3: now 51 pages; added another 34 references; more discussion of DSR and relative locality; various clarifications and extensions; this version accepted for publication in JHE

Spawning Characteristics of Yellow Perch during Periods of Water Level Fluctuations in a Hydropower Reservoir

Water level fluctuations alter reservoir ecosystems causing direct and indirect effects on fish populations. The dewatering of eggs, a direct impact of lake level drawdowns, can affect reproductive success of species that spawn in littoral zones, such as Yellow Perch. I examined relationships between water level fluctuations and spawning characteristics of Yellow Perch in a Central Appalachian hydropower reservoir, where water levels were permitted to be drawn down to 4 m and 2.1 m below the full pool elevation in March and April, respectively. Daily presences of egg masses were recorded on artificial spawning structures at two sites for the spring spawning seasons of 2019 and 2020. Spawning structures were placed at different distances from the shoreline, spanning water depths with and without the potential for dewatering based on the lowest permitted levels for lake elevation drawdowns. Generalized Estimation Equations (GEE) were used to analyze egg mass presence and six covariates: Secchi disk depth, distance to the shore, water temperature, water depth, lunar illumination, and lake level fluctuation. I also examined the proportion of egg masses in potential dewatering zones based on the minimum lake elevation drawdowns permitted for March and April. Data supported an additive effects model of Year + Water depth + Lunar illumination + Water temperature. The predicted probability of egg mass presence was negatively associated with water depth and lunar illumination, and positively associated with water temperature. A year effect, in part, reflected a between-year difference in the timing of spawning, where the number of egg masses during April exceeded that of March in 2019, a relationship that was reversed in 2020. During the 27-day spawning period in 2019, 52% (54 of 104) of egg masses had the potential to be dewatered, whereas 70% (30 of 43) had the potential to be dewatered in the 22-day spawning period of 2020. Our results have direct implications for fishery and hydropower management, as data on the characteristics and timing of spawning of yellow perch relative to water level fluctuations inform decisions regarding management of fish populations and lake level drawdown regulations

The cost of music

What is the cost of music in the so-called Anthropocene? We approach this question by focusing on the case of sound-recording formats. We consider the cost of recorded music through two overlapping lenses: economic cost, on the one hand, and environmental cost, on the other. The article begins by discussing how the price of records has changed from the late 19th to the 21st century and across the seven most economically significant playback formats: phonograph cylinder, gramophone disc, vinyl LP, cassette tape, compact disc, digital audio files on hard drive, and streaming from the cloud. Our case study territory is the United States, and we chart the gradual decline in the price of recorded music up to the present. We then examine the environmental and human costs of music by looking at what recordings are made out of, where those materials come from, and what happens to them when they are disposed of. Despite what rhetorics of digital dematerialisation tell us, we show that the labour conditions in the digital electronics and IT industries are as inhumane as ever, while the amount of greenhouse gases released by the US recording industry could actually be higher today than at the height of any previous format. We conclude by asking the obvious (but by no means straightforward) question: what are musicians and fans to do

Micro-Controlled Autonomous Vehicle Group

Our purpose is to design and build an autonomous microcontrolled land vehicle. It will be able to navigate from a given starting point to a desired location avoiding obstacles in its way. The course we plan to operate in has a flat surface and no more than five static obstacles. Our design considerations are the vehicle platform, motors, type of microcontroller, obstacle avoidance sensors, navigational sensors, and basic program behavior. We chose the Handy Board to control out vehicle, which is based on the Motorola 68HC11 microcontroller. It is a universal board that will meet our interfacing requirements. Obstacles will be detected using four infrared sensors places around the front of the vehicle. Four algorithms for completing out goal are discussed. We chose to use a navigation method involving optical encoders to determine distance and direction traveled. This paper describes the design process for our rover, the reasons for the hardware we selected, and how these decisions successfully allowed us to achieve our objectives

PRETA Air: Hazardous Air Pollutants

This report shows that people living in a 10-county region of southwestern Pennsylvania have a significantly higher than acceptable risk of developing cancer due to exposure to toxic air pollution released by manufacturing processes, energy production and diesel combustionThe Pittsburgh Regional Environmental Threats Analysis Report -- funded by The Heinz Endowments -- analyzes publicly available data on hazardous air pollutants (HAPs), also known as air toxics. Air toxics include approximately 200 pollutants identified by the U.S. Environmental Protection Agency (EPA) as known or suspected to cause cancer or other serious health effects, such as respiratory, neurological and reproductive disorders. The report is the third in a series as part of a project examining major threats to human health and the environment in southwestern Pennsylvania

PEER SUPPORT SYSTEMS

Using peer support in the classroom is an effective instructional strategy that helps bridge the gap for students with disabilities while supporting inclusion. This research to practice presentation discusses ways to implement peer supports in English Language Arts, music, and technical education courses to meet the instructional needs of all learners within our content areas. We will utilize a universal design for learning approach with an anti-ableist and anti-racist lens. We will include research related to this instructional strategy and provide specific examples that reach across content areas