Search

Changes in old age that contribute to the complex issue of an increased metabolic cost of walking (mass-specific energy cost per unit distance traveled) in older adults appear to center at least in part on changes in gait biomechanics. However, age-related changes in energy metabolism, neuromuscular function and connective tissue properties also likely contribute to this problem, of which the consequences are poor mobility and increased risk of inactivity-related disease and disability. The U.S. National Institute on Aging convened a workshop in September 2021 with an interdisciplinary group of scientists to address the gaps in research related to the mechanisms and consequences of changes in mobility in old age. The goal of the workshop was to identify promising ways to move the field forward toward improving gait performance, decreasing energy cost, and enhancing mobility for older adults. This report summarizes the workshop and brings multidisciplinary insight into the known and potential causes and consequences of age-related changes in gait biomechanics. We highlight how gait mechanics and energy cost change with aging, the potential neuromuscular mechanisms and role of connective tissue in these changes, and cutting-edge interventions and technologies that may be used to measure and improve gait and mobility in older adults. Key gaps in the literature that warrant targeted research in the future are identified and discussed.

Bohmian mechanics is a deterministic theory of quantum mechanics that is based on a set of n velocity functions for n particles, where these functions depend on the wavefunction from the n-body time-dependent Schroedinger equation. It is well know that Bohmian mechanics is not applicable to stationary states, since the velocity field for stationary states is the zero function. Recently, an alternative to Bohmian mechanics has been formulated, based on a conservation of energy equation, where the velocity fields are not the zero function, but this formalism is only applicable to stationary states with real valued wavefunctions. In this paper, Bohmian mechanics is merged with the alternative to Bohmian mechanics. This is accomplished by introducing an interpretation of the Bohm quantum potential. The final formalism gives dynamic particles for all states, including stationary states. The final main working equation contains two kinetic energy terms and a term that contains a factor that can be interpreted as a pressure. The derivation is a simple n-body generalization of the recent generalization, or refinement, of the Madelung equations., Comment: 7 pages

Composite materials are an attractive material for use in the aerospace and automotive sectors, due to their high specific strength and specific stiffness. However, most composites fail suddenly in a brittle manner, which may result in catastrophic failure. This inherent lack of tailorability in the mechanical response of composites has made their widespread application limited. Aligned discontinuous composites (ADCs) are a new type of material that offers increased mechanical tailorability, as subtle changes to the ADC microstructure can change its stress-strain response from high-strength linear elastic behaviour, to a non-linear response with high levels of pseudo-ductility. This work aims to understand mechanisms for mechanical tailorability in ADCs, and determine the suitability of ADCs for applications in real-world structures. A Virtual Testing Framework (VTF) is used and developed throughout this thesis, to give an in-depth understanding of the behaviour of ADCs. The VTF consists of a multiscale framework to simulate complete ADC specimens with hybrid or non-hybrid reinforcement; final failure of ADCs is simulated in the VTF by a non-linear fracture mechanics failure criterion. The VTF is successfully validated throughout this thesis against a variety of experimental data with good agreement. The first study explores the use of different hybrid fibre-type arrangements, to explore their influence on the pseudo-ductile behaviour of hybrid ADCs. The addition of a fibre-migration algorithm (used to capture the effects of fibre movement in ADCs during their manufacture), and developments to the fracture-based failure criterion, enable the VTF to successfully capture the effects of various levels of fibre-type grouping. Hybrid ADCs with larger groups of low-elongation fibres demonstrate a more brittle response, whereas intimate intermingling of the fibre-types increases pseudo-ductility. The ultimate strength and pseudo-ductility are then maximised by employing a fibre-type arrangement where the low-elongation fibres are completely isolated from one-another. Having shown variability in the fibre-type arrangement has a significant influence on tailorability, the concept of variability is explored further. Several new sources of variability and defects are added to the VTF, and the non-linear fracture-based failure criterion is further improved to accurately predict the failure of any type of ADC microstructure. The VTF indicates that the most critical source of variability (i.e. the source of variability that most readily promotes premature failure) depends on the microstructural design of the composite: hybrid-fibre ADCs are most sensitive to the fibre-type arrangement, while short-fibre non-hybrid ADCs are most sensitive to variability in the fibre overlap lengths, and long-fibre non-hybrid ADCs are more sensitive to weaker fibres. The VTF is then coupled with an intelligent optimisation routine to maximise the mechanical performance of ADCs that feature inherent variability. The use of a surrogate model helps minimise the number of design iterations before optimal design(s) are converged upon; surrogate modelling is also demonstrated to be invaluable when assessing the optimality of materials which feature high levels of inherent variability (such as ADCs). The true tailorability of ADCs is showcased, with an initial stiffness of 505 GPa, an ultimate strength of 1.92 GPa, or an ultimate strain of 3.92 % all achievable in ADCs via single-objective optimisation. While significant trade-offs between competing mechanical performance characteristics are found, useful combinations of mechanical properties remain, with an optimal ultimate strength & ultimate strain combination of 982 MPa and 3.27 %, or an optimal combination of 720 MPa yield strength & 1.91 % pseudo-ductile strain all possible. ADCs are shown throughout this thesis to fail by translaminar fracture, yet the resistance of ADCs to translaminar cracks has never been measured; the translaminar fracture toughness is therefore a key material property that must be characterised, to enable accurate failure predictions using the VTF, and to enable the use of ADCs as part of a damage tolerant structure. Specially-designed compact tension tests are performed to measure the translaminar fracture toughness of hybrid and non-hybrid ADCs for the first time in literature. Results show that the translaminar fracture toughness of non-hybrid ADCs is significantly higher than hybrid ADCs, and that analytical predictions of the translaminar fracture toughness are sufficiently accurate to ensure realistic failure predictions using the VTF. The new understanding and optimisation of aligned discontinuous composites demonstrates the feasibility of ADCs as an alternative material for the aerospace and automotive sectors. The models developed as part of this study can be used to support the design of new materials, perform parametric studies, and perform intelligent optimisation campaigns. Open Access

This chapter examines the tendency of readers of Thoreau's 1864 book "The Maine Woods" to read the landscape through which Thoreau travels as pristine wilderness. I argue, by contrast, that Thoreau presented a social landscape, a "working-forest" avant-la-lettre.

Supplemental Material, Appendix_S3_Short,_follow-up_survey for More “Bank” for the Buck: Microtargeting and Normative Appeals to Increase Social Marketing Efficiency by Alexander L. Metcalf, Justin W. Angle, Conor N. Phelan, B. Allyson Muth, and James C. Finley in Social Marketin Quarterly

Supplemental Material, Appendix_S2 for More “Bank” for the Buck: Microtargeting and Normative Appeals to Increase Social Marketing Efficiency by Alexander L. Metcalf, Justin W. Angle, Conor N. Phelan, B. Allyson Muth, and James C. Finley in Social Marketin Quarterly

This chapter explores Thoreau’s engagement with Free Soil ideology and contextualizes Thoreau’s ecologically oriented social reform. Thoreau, I argue, transforms the Free Soil position that slaveholding degrades labor and landscapes, making it more attentive to Transcendentalist ethics and ecological volatility. More specifically, the ecological vision of antislavery that Thoreau articulates in “Slavery in Massachusetts” and the individualist, anticapitalist free soil project that he fashions in "Walden" both point toward his embrace of John Brown as the apotheosis of a uniquely Thoreauvian version of Free Soil.

This essay addresses the ecological valences within Thoreau’s political writings, arguing specifically that his antislavery essays, from the beginning of his abolitionist commitment, reflect a concern that slavery is an environmental problem best addressed through an ecologically inflected protest.

This essay surveys Thoreau's antislavery writings from across his career and demonstrates the ecological concerns central to Thoreau's abolitionist commitment.

This essay situates "The Narrative of the Life and Adventures of Henry Bibb, An American Slave" within the political context of the antislavery Free Soil movement, arguing that Bibb's representations of land and labor reflect the concerns of Free Soil. In particular, it argues that Bibb's narrative simultaneously critiques Free Soil ideology for its lack of a full-throated call for immediate abolition and its privileging of the white working class over both free and enslaved Black people. In addition, these aspects of Bibb’s Free Soil critique— both in condemning slavery and in reflexively challenging elements of Free Soil ideology—are more ecological than established Free Soil discourse, reflecting a deeper, more sensitive, and more radical understanding of material interconnection in regards to bodies, means of production, and topographies.

This essay argues that Thoreau witnesses a series of clashes across the three essays collected in "The Maine Woods" and that Thoreau positions himself with a variety of contact zones, enabling him both to navigate the landscapes of northern Maine and recount his experiences to his audiences.

Community-based forestry and community-based natural resource management have become increasingly common terms in both the scientific and popular press. However, as with so many other concepts currently in vogue, rarely do studies invoking them incorporate either a grounded theoretical understanding or practical inclusion of the central term: community. Community emerges through communication and interaction among people who care about each other and the place they live. In its purest form, community is marked by its multiple and often conflicting perspectives. This article draws upon recent research experience with the Ford Foundation's community-based forestry initiative to illustrate the importance of solidly framing community in order to successfully link forest ecosystem management with community well-being.

Symposium Presentation (for Acquisition Research Program) Symposium Presentation Naval Postgraduate School Acquisition Research Program Approved for public release; distribution is unlimited.

Using an approach based on many body perturbation theory, the correlation energy $\cEco$ is expressed as an explicit functional of $\rho_1$, $v$, and $v_s$, where $\rho_1$ is the one-particle density matrix from the noninteracting, or reference, determinantal-state; $v$ is the external potential from the interacting, or target, state; $v_s$ is the (kernel of the) external potential from the noninteracting determinantal-state. In other words we have $\cEco[\rho_1,v,v_s]$. Anther possibility is the following explicit functional: $\cEco[\rho_1,v_{\text{co}},v_s]$, where $v_{\text{co}}$ is the (kernel of the) correlation potential from the noninteracting Hamiltonian. The proposed method can, in principle, be used to compute $\cEco$ in a very accurate and efficient manner, since, like the Kohn--Sham approach, there are no virtual orbitals to consider. However, in contrast to the Kohn--Sham approach, $\cEco$ is a known, explicit functional that can be approximated in a systematic manner. For simplicity, we only consider noninteracting closed-shell states and target states that are nondegenerate, singlet ground-states; so, in that case, $\rho_1$ denotes the spin-less one-particle density matrix from the determinantal reference state.

A generalization of the Kohn--Sham approach is derived where the correlation-energy functional depends on the one-particle density matrix of noninteracting states and on the external potential from the interacting target-state. The one-particle equations contain the exact exchange potential, a nonlocal correlation potential, and an additional operator involving the correlation density. The electronic-energy functional has multiple solutions: Any one-particle density matrix delivering the target-state density yields a solution. In order to obtain the Kohn--Sham solution, the nonlocal operators are converted into local ones using an approach developed by Sala and Gorling. Since the exact exchange-potential is used, and the N--representability problem does not arise--in contrast to the Kohn--Sham approach--errors from Coulomb self-interactions do not occur, nor the need to introduce functionals defined by a constraint search. Furthermore, the approach does not use the Hohenberg-Kohn theorem. A density functional formalism is also derived that assumes that the one-particle density matrices of interest have v-representable (non-interacting) densities and that these density matrices can be written as an explicit functional of the electron density. For simplicity, we only consider noninteracting closed-shell states and target states that are nondegenerate, singlet ground-states., Comment: Trivial changes made from version 1, 19 Pages, submitted to Phys. Rev. A

Brueckner orbitals, and the density of the Brueckner reference-state, are shown to satify the same cusp condition -- involving the nuclear charges -- as natural- and Hartree--Fock-orbitals. Using the cusp condition, the density of a determinantal state can be used to determine the external potential, if the determinantal state is from either Hartee--Fock or Brueckner-orbital theory, as well as, determinant states obtained by many other formalisms that are defined by a one-body operator, if a portion of the one-body operator -- the portion not associated with the kinetic energy or external potential -- generates a well behaved function when acting on an occupied orbital. Using this relationship involving a determinant and its external potential, a variation of Reference--State One--Particle Density--Matrix Theory (physics/0308056) is formulated, where the trial wavefunctions are universal, in the Kohn-Sham sense, since they do not depend on the external potential. The resulting correlation-energy functionals, are also, universal, except for a relatively small term involving the portion of the expectation value of the external potential with the trial wavefunctions that appears beyond the first order. The same approximate energy functionals that were shown to be valid for the previous v-dependent, Reference--State One--Particle Density--Matrix Theory (physics/0308084), are shown to be valid for the current approach, except that the use of the LYP and Colle--Salvetti functional appear more natural within the current approach, since these functionals are universal ones. And since the BLYP and B3LYP functionals contain the LYP functional, these approaches are also better suited with the current approach., Comment: 44 Pages

During the past year, members of the Sustainable Forestry Partnership, in cooperation with other forestry schools, with funding from the several private foundations and USDA, have been exploring approaches for enhancing graduate education programs to foster adoption of Sustainable Forest Management curriculum concepts. Ten National Association of Professional Forestry Schools and Colleges (NAPFSC) members have conducted two focus groups to gain understanding of curriculum opportunities and challenges. The findings from these focus groups will be reported out at a national conference in Kansas City in November 2001. That assembled group will begin to discuss ways and approaches for cooperating across institutions to share resources to engage expanded opportunities for enhancing education on sustainable forestry. We will quickly present the findings from the Kansas City workshop, and then explore how we can further the discussion, foster partnerships, and consider how we can develop and implement new reaching strategies.

As college instructors have recognized the benefits provided by cooperative and active learning, many have shifted from their traditional teaching style, dominated by lectures, to a new style where students work together and learn from each other as well as from the instructor. One strategy commonly used to implement cooperative learning in the classroom is to require students to work in teams to complete a class project. This strategy is particularly attractive to natural resources educators because natural resource issues are generally complex and interdisciplinary providing a natural setting for teaching concepts regarding natural resources ecology and management using student team projects. Further, natural resources agencies are seeking to employ individuals who have the skills to work in interdisciplinary teams to address current problems. Thus, assigning projects to student teams in natural resources classes can serve several important purposes: it can aid student mastery of the subject matter by creating a cooperative learning environment; it can provide a hands-on, problem solving context for student learning; and it can provide students with the necessary skills and experience to work effectively in teams as professionals. Although using student team projects has many potential benefits, the effectiveness of this approach as a teaching tool can vary greatly. We reflect on our experiences with using the team approach in three different courses: Fishery Management, designed for junior and senior level students; Natural Resources Decisions, a capstone course designed for seniors in the School of Forest Resources; and Watershed Management Planning, a graduate level course. As a result of our collective experiences in these three courses, we propose that investing a relatively small amount of class time to introduce students to the concept of a team and how teams work can increase the effectiveness of teaching by using student team projects.