Getting the Swing of Surface Gravity

Sports are a popular and effective way to illustrate physics principles. Baseball in particular presents a number of opportunities to motivate student interest and teach concepts. Several articles have appeared in this journal on this topic, illustrating a wide variety of areas of physics. In addition, several websites and an entire book are available. In this paper we describe a student-designed project that illustrates the relative surface gravity on the Earth, Sun and other solar-system bodies using baseball. We describe the project and its results here as an example of a simple, fun, and student-driven use of baseball to illustrate an important physics principle

Hidden Markov models reveal complexity in the diving behaviour of short-finned pilot whales

This work was supported by award RC-2154 from the Strategic Environmental Research and Development Program and funding from the Naval Facilities Engineering Command Atlantic and NOAA Fisheries, Southeast Region. DS was supported by the United States Office of Naval Research grant N00014-12-1-0204, under the project entitled Multi-study Ocean acoustics Human effects Analysis (MOCHA).Diving behaviour of short-finned pilot whales is often described by two states; deep foraging and shallow, non-foraging dives. However, this simple classification system ignores much of the variation that occurs during subsurface periods. We used multi-state hidden Markov models (HMM) to characterize states of diving behaviour and the transitions between states in short-finned pilot whales. We used three parameters (number of buzzes, maximum dive depth and duration) measured in 259 dives by digital acoustic recording tags (DTAGs) deployed on 20 individual whales off Cape Hatteras, North Carolina, USA. The HMM identified a four-state model as the best descriptor of diving behaviour. The state-dependent distributions for the diving parameters showed variation between states, indicative of different diving behaviours. Transition probabilities were considerably higher for state persistence than state switching, indicating that dive types occurred in bouts. Our results indicate that subsurface behaviour in short-finned pilot whales is more complex than a simple dichotomy of deep and shallow diving states, and labelling all subsurface behaviour as deep dives or shallow dives discounts a significant amount of important variation. We discuss potential drivers of these patterns, including variation in foraging success, prey availability and selection, bathymetry, physiological constraints and socially mediated behaviour.Publisher PDFPeer reviewe

Real-time selective sequencing using nanopore technology

The Oxford Nanopore Technologies MinION sequencer enables the selection of specific DNA molecules for sequencing by reversing the driving voltage across individual nanopores. To directly select molecules for sequencing, we used dynamic time warping to match reads to reference sequences. We demonstrate our open-source Read Until software in real-time selective sequencing of regions within small genomes, individual amplicon enrichment and normalization of an amplicon set

Exploring crime in Toronto, Ontario with applications for law enforcement planning: Geographic analysis of hot spots and risk factors for expressive and acquisitive crimes

This thesis explores crime hot spots and identifies risk factors of expressive and acquisitive crimes in Toronto, Ontario at the census tract scale using official crime offence data from 2006. Four research objectives motivate this thesis: 1) to understand a number of local spatial cluster detection tests and how they can be applied to inform law enforcement planning and confirmatory research, 2) explore spatial regression techniques and applications in past spatial studies of crime, 3) to examine the influence of social disorganization and non-residential land use on expressive crime at the census tract scale, and 4) integrate social disorganization and routine activity theories to understand the small-area risk factors of acquisitive crimes. Research chapters are thematically linked by an intent to recognize crime as a spatial phenomenon, provide insight into the processes and risk factors associated with crime, and inform efficient and effective law enforcement planning

Spatiotemporal crime patterns and the urban environment: Evidence for planning and place-based policy

Crime and disorder influence individual quality of life, community social cohesion, and processes of neighbourhood and urban change. Existing studies that analyze local crime and disorder patterns generally focus only on where crime and disorder events occur. However, understanding the spatiotemporal patterning of crime and disorder, or both where and when events occur, is central to the design, implementation, and evaluation of crime prevention policies and programs. This dissertation explores the connections between local spatiotemporal patterns of crime and disorder, the urban environment, and urban planning through three research articles. Each article makes theoretical contributions that improve understanding of how characteristics of the urban environment influence crime and disorder, methodological contributions that advance spatiotemporal modeling of small-area crime data, and policy-oriented contributions that inform place-based crime prevention initiatives in urban planning, local government, and law enforcement. The first research article examines if, and how, physical disorder, social disorder, property crime, and violent crime share a common spatial pattern and/or a common time trend. Three multivariate models are compared and the results of the best-fitting model show that all crime and disorder types share a common spatial pattern and a common time trend. The shared spatial pattern is found to explain the largest proportion of variability for all types of crime and disorder, and type-specific spatiotemporal hotspots of crime and disorder are identified and investigated to contextualize broken windows theory. This study supports collective efficacy theory, which contends that multiple crime and disorder types are associated with same underlying processes, and highlights specific areas where crime prevention interventions should be designed to address all, or only one, type(s) of crime and disorder. The second article quantifies the time-varying relationships between land use and property crime for twelve seasons at the small-area scale. A set of spatiotemporal regression models with time-constant and time-varying regression coefficients are compared and the results of the best-fitting model show that parks and eating and drinking establishments exhibit recurring seasonal relationships, where parks are more positively associated with property crime during spring/summer and eating and drinking establishments are more positively associated with property crime during autumn/winter. Local land use composition is shown to have a more substantial impact on the spatial, rather than the spatiotemporal, patterning of crime. Applied to policy, the results of this article inform the design and coordination of time-constant and time-varying crime prevention initiatives as implemented by urban planning and law enforcement agencies, respectively. The third article investigates the spatiotemporal patterning of violent crime across multiple spatial scales. Violent crime data are measured at the small-area scale (lower-level units) and small-areas are nested in neighbourhoods, electoral wards, and patrol zones (higher-level units). A cross-classified multilevel model is applied to accommodate the three higher-level units that are non-hierarchical and have overlapping boundaries. Accounting for sociodemographic, built environment, and civic engagement characteristics, planning neighborhoods, electoral wards, and patrol zones are found to explain approximately fourteen percent of the total spatiotemporal variation of violent crime. Planning neighborhoods are the most important source of variation amongst the higher-level units. This article advances understanding of the multiscale processes that influence where and when violent crime events occur and provides area-specific crime risk information within the geographical frameworks used by policymakers in urban planning (neighbourhoods), local government (wards), and law enforcement (patrol zones). Broadly, this dissertation advances research focused on the connections between crime and disorder and the urban environment by (1) quantifying the degree to which spatiotemporal crime and disorder patterns are stable and/or dynamic, (2) examining the relationships between crime and disorder and local sociodemographic and built environment characteristics, (3) illustrating a set of statistical models that make sense of spatiotemporal crime and disorder patterns at the small-area scale, and (4) providing local spatiotemporal information that can be used to design and implement place-based crime prevention initiatives in urban planning, local government, and law enforcement

Representability of the local motivic Brouwer degree

We study which quadratic forms are representable as the local degree of a map f:An→An with an isolated zero at 0 , following the work of Kass and Wickelgren who established the connection to the quadratic form of Eisenbud, Khimshiashvili, and Levine. Our main observation is that over some base fields k , not all quadratic forms are representable as a local degree. Empirically the local degree of a map f:An→An has many hyperbolic summands, and we prove that in fact this is the case for local degrees of low rank. We establish a complete classification of the quadratic forms of rank at most 7 that are representable as the local degree of a map over all base fields of characteristic different from 2 . The number of hyperbolic summands was also studied by Eisenbud and Levine, where they establish general bounds on the number of hyperbolic forms that must appear in a quadratic form that is representable as a local degree. Our proof method is elementary and constructive in the case of rank 5 local degrees, while the work of Eisenbud and Levine is more general. We provide further families of examples that verify that the bounds of Eisenbud and Levine are tight in several cases