Jet Fuel Hedging Strategies for the Department of Defense Through Use of Financial Derivatives

The primary purpose of this research is to assess the practicality of utilizing some of the financial derivative products available on the market today in an effort to mitigate monetary losses due to the increasing price of jet fuel, thereby increasing stability in the DOD budget. The scope of this research will focus on the use of futures and call option contracts. Domestic jet fuel expenditure data was collected for Fiscal Years 1996 to 2007 and cross-referenced with the contract process of the previously mentioned financial hedging instruments during the same period of time. Results from the ex post facto analysis indicate that hedging with either heating oil futures or heating oil call options would have provided a tremendous overall savings to the DoD. Currently the DoD does not hedge its budget against fluctuation in the jet fuel spot market. The implication from this study is that the DoD should consider hedging its jet fuel exposure with either derivative, in particular call options as it is tailored for risk adverse customers

Individual-based chaos: Extensions of the discrete logistic model

Simple models of density-dependent population growth such as the discrete logistic map provide powerful demonstrations of complex population dynamics. Yet it is unclear whether the dynamics observed in such idealized systems would be present, under realistic conditions, in the context of demographic stochasticity, which is well known to exist in finite natural populations. Here, using a set of simple, individual-based models (IBM's) and their population-level iterative map counterparts, we computationally investigate the contribution of demographic stochasticity to density-dependent population dynamics in a simple model of seed production and recruitment. Notably, for a sufficiently large lattice, even in the presence of demographic stochasticity, many of the qualitative features of these idealized maps – including bifurcations – are still present. Demographic stochasticity and the constraints imposed by a finite lattice size appear to produce mixed dynamics that are partially stochastic, yet qualitatively similar to the deterministic models. The mechanistic assumptions and lattice sizes required to generate these dynamics cast doubt on whether they might be observable in annual plant populations. Nevertheless, we cannot rule out the theoretical possibility that such dynamics might be observable in ecological communities having similar mechanistic properties

Trunk muscle activity during drop jump performance in adolescent athletes with back pain

It was with great interest we read the recently published article “Trunk Muscle Activity during Drop Jump Performance in Adolescent Athletes with Back Pain.” Investigating back pain (BP) in adolescents is commendable as there is growing evidence that for many, an experience of BP as early as 14 years of age may relate to ongoing pain in adulthood (Coenen et al., 2017). Indeed, the conventional narrative is changing as individual physical factors such as posture, use of schoolbags, and hypermobility are only weakly associated with adolescent BP. Rather, factors which predict BP at a young age are considered to be multi-dimensional and include gender, negative BP beliefs and poor mental health (O\u27Sullivan et al., 2017; Smith et al., 2017). Mueller et al. (2017) have focused on a single physical factor (trunk muscle activation patterns) drawing inferences regarding BP prevention and treatment. This article prompts consideration of three essential aspects regarding research design and interpretation of findings: 1. Interpreting results from cross-sectional designs 2. Interpreting pain-related differences in motor behavior 3. Translating and conveying scientific results to the end-user (patients, healthcare professionals and policy makers)

Conceptualizations of Nature and Scientific Literacy, Part I: Research Methodology

If we may paraphrase and adapt from feminist scholars, there are voices of people that need to be heard if scholars intend to have a valid understanding of people and their behavior. The feminist scholars were of course seeking ways of making women’s voices heard but the importance of their work exceeds gender issues. It is important for restoring the image of people as persons rather than as objects of research. As we have undertaken it, the foundational perspective of worldview research is that one must hear from students and science teachers about themselves. We thus suggest it is important for science educators to understand the fundamental, culturally based beliefs about the world that students and teachers bring to class; because, science education is successful only to the extent that science can find a niche in the cognitive and cultural milieus of students. The purpose of this article is to present an new interpretive methodology for exploring worldview presuppositions about the natural world through the language and ideas voluntarily expressed by science teachers and students. The methodology addresses the broad question, What is it that people think about nature or the natural world? The research objective of the methodology is to map the qualitatively different conceptualizations of nature held by people and thus to better understand the place science finds in those conceptualizations. The methodology is a modified naturalistic inquiry, interview technique. The audio taped interviews are semi-structured in that an interview involves elicitation devices designed to encourage a person to talk at length about nature. The findings are assertions based on concept maps and first person interpretive narratives derived from the interviews. The intention is to develop working hypotheses in the form of interpretive assertions through an emergent design. While the method described here is specifically about the essence of nature, similar methodology is used for investigating other worldview categories with respect to science understanding.

Leaving Elementary School with a Sense of Order in Nature

Ninth graders in Arizona high schools have just left their elementary, general science education and are at the start of more specialized secondary science education. They are beginning a course of study that will form the foundation for tertiary education and employment after high school graduation. The research asked, Who are these kids entering high school science courses? The researchers noted that one of the key objectives of elementary education is to foster in children the concept that nature is inherently orderly and thus amenable to scientific investigation. Since the concept of order or disorder is fundamental in one’s perception of reality, the researchers reasoned that the qualitative worldview interviews on nature would be revealing of these concepts. The research led to this assertion: After nine years of schooling, ninth graders show no consistent understanding of the order in nature on which science is predicated. Instead, students often name drop school science topics such as the ozone layer, rain forests, or the big bang theory

The Different Worlds of High School Biology and Physical Science Teachers

A science teacher not only presents scientific concepts, but tacitly creates a context in which scientific concepts are presented to the class. This context can be strongly influenced by teacher beliefs or worldview. In the current research, teacher worldviews with respect to the essence of nature were examined. Two biology and two physical science teachers individually sat for qualitative interviews. The same interview protocols were used in a concurrent study involving ninth graders at their high school. The analysis led to three assertions: (1) When compared with their students, the science teachers had a much more focused and less diverse conceptualization of the natural world. The students were much more likely to speak of aesthetic and spiritual elements of nature in contrast to their teachers who focused more on what one could know about nature. Teachers also spoke more in-depth on topics rather than the “name dropping” typical of the students. (2) The most interesting finding was that the physical science and biology teachers had considerably different conceptualizations of nature. The physical science teachers talked much more about all that scientists do know about nature and how successful science has been. (3) The biology teachers were much less sanguine about science, yet clearly enthusiastic. They showed greater concern about the environment and were more likely to speak of the aesthetics of nature

Achilles tendinopathy alters stretch shortening cycle behaviour during a sub-maximal hopping task

Objectives To describe stretch shortening cycle behaviour of the ankle and lower limb in patients with Achilles tendinopathy (AT) and establish differences with healthy volunteers. Design Between-subjects case-controlled. Methods Fifteen patients with AT (mean age 41.2 ± 12.7 years) and 11 healthy volunteers (CON) (mean age 23.2 ± 6.7 years) performed sub-maximal single-limb hopping on a custom built sledge-jump system. Using 3D motion analysis and surface EMG, temporal kinematic (lower limb stiffness, ankle angle at 80 ms pre-contact, ankle angle at contact, peak ankle angle, ankle stretch amplitude) and EMG measures (onset, offset and peak times relative to contact) were captured. Data between AT and CON were compared statistically using a linear mixed model. Results Patients with AT exhibited significantly increased lower limb stiffness when compared to healthy volunteers (p \u3c 0.001) and their hopping range was shifted towards a more dorsiflexed position (p \u3c 0.001). Furthermore, ankle stretch amplitude was greater in AT compared with healthy volunteers (p \u3c 0.001). A delay in muscle activity was also observed; soleus onset (p \u3c 0.001), tibialis anterior peak (p = 0.026) and tibialis anterior offset (p \u3c 0.001) were all delayed in AT compared with CON. Conclusions These findings indicate that patients with AT exhibit altered stretch-shortening cycle behaviour during sub-maximal hopping when compared with healthy volunteers. Patients with AT hop with greater lower limb stiffness, in a greater degree of ankle dorsiflexion and have a greater stretch amplitude. Likewise, delayed muscle activity is evident. These findings have implications in terms of informing the understanding of the pathoaetiology and management of AT

On the origins of the mitotic shift in proliferating cell layers

Background: During plant and animal development, monolayer cell sheets display a stereotyped distribution of polygonal cell shapes. In interphase cells these shapes range from quadrilaterals to decagons, with a robust average of six sides per cell. In contrast, the subset of cells in mitosis exhibits a distinct distribution with an average of seven sides. It remains unclear whether this ‘mitotic shift’ reflects a causal relationship between increased polygonal sidedness and increased division likelihood, or alternatively, a passive effect of local proliferation on cell shape. Methods: We use a combination of probabilistic analysis and mathematical modeling to predict the geometry of mitotic polygonal cells in a proliferating cell layer. To test these predictions experimentally, we use Flp-Out stochastic labeling in the Drosophila wing disc to induce single cell clones, and confocal imaging to quantify the polygonal topologies of these clones as a function of cellular age. For a more generic test in an idealized cell layer, we model epithelial sheet proliferation in a finite element framework, which yields a computationally robust, emergent prediction of the mitotic cell shape distribution. Results: Using both mathematical and experimental approaches, we show that the mitotic shift derives primarily from passive, non-autonomous effects of mitoses in neighboring cells on each cell’s geometry over the course of the cell cycle. Computationally, we predict that interphase cells should passively gain sides over time, such that cells at more advanced stages of the cell cycle will tend to have a larger number of neighbors than those at earlier stages. Validating this prediction, experimental analysis of randomly labeled epithelial cells in the Drosophila wing disc demonstrates that labeled cells exhibit an age-dependent increase in polygonal sidedness. Reinforcing these data, finite element simulations of epithelial sheet proliferation demonstrate in a generic framework that passive side-gaining is sufficient to generate a mitotic shift. Conclusions: Taken together, our results strongly suggest that the mitotic shift reflects a time-dependent accumulation of shared cellular interfaces over the course of the cell cycle. These results uncover fundamental constraints on the relationship between cell shape and cell division that should be general in adherent, polarized cell layers