Dynamic concentration of motors in microtubule arrays

We present experimental and theoretical studies of the dynamics of molecular motors in microtubule arrays and asters. By solving a convection-diffusion equation we find that the density profile of motors in a two-dimensional aster is characterized by continuously varying exponents. Simulations are used to verify the assumptions of the continuum model. We observe the concentration profiles of kinesin moving in quasi two-dimensional artificial asters by fluorescent microscopy and compare with our theoretical results.Comment: 4pages, 4 figures revte

Sustainable Energy at Coastal Facilities

NPS NRP Project PosterThis research effort examined the paths to further adoption of sustainable energy at coastal facilities. It examined current technical, financial, legal, and policy challenges that have hindered past efforts to incorporate more renewable energy and that are priorities to be considered for future renewable energy projects. The research team gathered data and information through an examination of literature and interviews with subject matter experts familiar with coastal facilities and with experts in the renewable energy sector. The team conducted two case studies of US Coast Guard Station Monterey (CA) and Naval Air Station Corpus Christi (TX) to provide additional context for the adoption of sustainable renewable energy at coastal facilities. Additionally, research was conducted on mechanisms for microgrid financing to demonstrate how a facility may finance microgrid installation and further adoption of renewable energy and microgrids. Researchers found that there are some common core challenges for installing and using microgrids. These challenges include zoning issues, environmental considerations, infrastructure barriers, financing issues, conflicting safety standards, technical obstacles, and administrative hurdles. Researchers found that some challenges can be lessened, avoided, or accounted for with advance preparation and awareness ahead of time. Further analysis of region-specific challenges would provide more context for consideration of sustainable energy and implementation of microgrids. Further study is also required to understand the details of an appropriate financial acquisition agreement with a quantification of the benefits and costs of microgrids over time. Finally, the processes for contracting out microgrid design and construction and identifying suitable contractors is recommended.NAVFAC Engineering and Expeditionary Warfare CenterN4 - Fleet Readiness & LogisticsThis research is supported by funding from the Naval Postgraduate School, Naval Research Program (PE 0605853N/2098). https://nps.edu/nrpChief of Naval Operations (CNO)Approved for public release. Distribution is unlimited.

Sustainable Energy at Coastal Facilities

NPS NRP Technical ReportThis research effort examined the paths to further adoption of sustainable energy at coastal facilities. It examined current technical, financial, legal, and policy challenges that have hindered past efforts to incorporate more renewable energy and that are priorities to be considered for future renewable energy projects. The research team gathered data and information through an examination of literature and interviews with subject matter experts familiar with coastal facilities and with experts in the renewable energy sector. The team conducted two case studies of US Coast Guard Station Monterey (CA) and Naval Air Station Corpus Christi (TX) to provide additional context for the adoption of sustainable renewable energy at coastal facilities. Additionally, research was conducted on mechanisms for microgrid financing to demonstrate how a facility may finance microgrid installation and further adoption of renewable energy and microgrids. Researchers found that there are some common core challenges for installing and using microgrids. These challenges include zoning issues, environmental considerations, infrastructure barriers, financing issues, conflicting safety standards, technical obstacles, and administrative hurdles. Researchers found that some challenges can be lessened, avoided, or accounted for with advance preparation and awareness ahead of time. Further analysis of region-specific challenges would provide more context for consideration of sustainable energy and implementation of microgrids. Further study is also required to understand the details of an appropriate financial acquisition agreement with a quantification of the benefits and costs of microgrids over time. Finally, the processes for contracting out microgrid design and construction and identifying suitable contractors is recommended.NAVFAC Engineering and Expeditionary Warfare CenterN4 - Fleet Readiness & LogisticsThis research is supported by funding from the Naval Postgraduate School, Naval Research Program (PE 0605853N/2098). https://nps.edu/nrpChief of Naval Operations (CNO)Approved for public release. Distribution is unlimited.

Sustainable Energy at Coastal Facilities

NPS NRP Executive SummaryThis research effort examined the paths to further adoption of sustainable energy at coastal facilities. It examined current technical, financial, legal, and policy challenges that have hindered past efforts to incorporate more renewable energy and that are priorities to be considered for future renewable energy projects. The research team gathered data and information through an examination of literature and interviews with subject matter experts familiar with coastal facilities and with experts in the renewable energy sector. The team conducted two case studies of US Coast Guard Station Monterey (CA) and Naval Air Station Corpus Christi (TX) to provide additional context for the adoption of sustainable renewable energy at coastal facilities. Additionally, research was conducted on mechanisms for microgrid financing to demonstrate how a facility may finance microgrid installation and further adoption of renewable energy and microgrids. Researchers found that there are some common core challenges for installing and using microgrids. These challenges include zoning issues, environmental considerations, infrastructure barriers, financing issues, conflicting safety standards, technical obstacles, and administrative hurdles. Researchers found that some challenges can be lessened, avoided, or accounted for with advance preparation and awareness ahead of time. Further analysis of region-specific challenges would provide more context for consideration of sustainable energy and implementation of microgrids. Further study is also required to understand the details of an appropriate financial acquisition agreement with a quantification of the benefits and costs of microgrids over time. Finally, the processes for contracting out microgrid design and construction and identifying suitable contractors is recommended.NAVFAC Engineering and Expeditionary Warfare CenterN4 - Fleet Readiness & LogisticsThis research is supported by funding from the Naval Postgraduate School, Naval Research Program (PE 0605853N/2098). https://nps.edu/nrpChief of Naval Operations (CNO)Approved for public release. Distribution is unlimited.

Swimming in circles: Motion of bacteria near solid boundaries

Near a solid boundary, E. coli swims in clockwise circular motion. We provide a hydrodynamic model for this behavior. We show that circular trajectories are natural consequences of force-free and torque-free swimming, and the hydrodynamic interactions with the boundary, which also leads to a hydrodynamic trapping of the cells close to the surface. We compare the results of the model with experimental data and obtain reasonable agreement. In particular, we show that the radius of curvature of the trajectory increases with the length of the bacterium body.Comment: Also available at http://people.deas.harvard.edu/~lauga

Energy Transduction of Isothermal Ratchets: Generic Aspects and Specific Examples Close to and Far from Equilibrium

We study the energetics of isothermal ratchets which are driven by a chemical reaction between two states and operate in contact with a single heat bath of constant temperature. We discuss generic aspects of energy transduction such as Onsager relations in the linear response regime as well as the efficiency and dissipation close to and far from equilibrium. In the linear response regime where the system operates reversibly the efficiency is in general nonzero. Studying the properties for specific examples of energy landscapes and transitions, we observe in the linear response regime that the efficiency can have a maximum as a function of temperature. Far from equilibrium in the fully irreversible regime, we find a maximum of the efficiency with values larger than in the linear regime for an optimal choice of the chemical driving force. We show that corresponding efficiencies can be of the order of 50%. A simple analytic argument allows us to estimate the efficiency in this irreversible regime for small external forces.Comment: 16 pages, 10 figure

Tools for delivering entomopathogenic fungi to malaria mosquitoes: effects of delivery surfaces on fungal efficacy and persistence.

BACKGROUND\ud \ud Entomopathogenic fungi infection on malaria vectors increases daily mortality rates and thus represents a control measure that could be used in integrated programmes alongside insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS). Before entomopathogenic fungi can be integrated into control programmes, an effective delivery system must be developed.\ud \ud METHODS\ud \ud The efficacy of Metarhizium anisopliae ICIPE-30 and Beauveria bassiana I93-825 (IMI 391510) (2 × 10(10) conidia m(-2)) applied on mud panels (simulating walls of traditional Tanzanian houses), black cotton cloth and polyester netting was evaluated against adult Anopheles gambiae sensu stricto. Mosquitoes were exposed to the treated surfaces 2, 14 and 28 d after conidia were applied. Survival of mosquitoes was monitored daily.\ud \ud RESULTS\ud \ud All fungal treatments caused a significantly increased mortality in the exposed mosquitoes, descending with time since fungal application. Mosquitoes exposed to M. anisopliae conidia on mud panels had a greater daily risk of dying compared to those exposed to conidia on either netting or cotton cloth (p < 0.001). Mosquitoes exposed to B. bassiana conidia on mud panels or cotton cloth had similar daily risk of death (p = 0.14), and a higher risk than those exposed to treated polyester netting (p < 0.001). Residual activity of fungi declined over time; however, conidia remained pathogenic at 28 d post application, and were able to infect and kill 73 - 82% of mosquitoes within 14 d.\ud \ud CONCLUSION\ud \ud Both fungal isolates reduced mosquito survival on immediate exposure and up to 28 d after application. Conidia were more effective when applied on mud panels and cotton cloth compared with polyester netting. Cotton cloth and mud, therefore, represent potential substrates for delivering fungi to mosquitoes in the field

Simulating the influences of groundwater on regional geomorphology using a distributed, dynamic, landscape evolution modelling platform

A dynamic landscape evolution modelling platform (CLiDE) is presented that allows a variety of Earth system interactions to be explored under differing environmental forcing factors. Representation of distributed surface and subsurface hydrology within CLiDE is suited to simulation at sub-annual to centennial time-scales. In this study the hydrological components of CLiDE are evaluated against analytical solutions and recorded datasets. The impact of differing groundwater regimes on sediment discharge is examined for a simple, idealised catchment, Sediment discharge is found to be a function of the evolving catchment morphology. Application of CLiDE to the upper Eden Valley catchment, UK, suggests the addition of baseflow-return from groundwater into the fluvial system modifies the total catchment sediment discharge and the spatio-temporal distribution of sediment fluxes during storm events. The occurrence of a storm following a period of appreciable antecedent rainfall is found to increase simulated sediment fluxes

Double Blind Study Investigating the Effect of Different Voice Prostheses on Ease of Swallowing and Residue Post Laryngectomy.

Voice prostheses have been examined for their effect on voice production but there is little datum on their effect on swallow function. This study investigated the difference between six commonly available voice prostheses in terms of swallowing. Laryngectomy patients had up to six voice prostheses placed in a random order over two visits. Swallowing was evaluated for each prosthesis using FEES (Fibreoptic Endoscopic Evaluation of Swallowing). After each prosthesis trial, patients self-evaluated their experience of swallowing. Three independent experts indicated which prosthesis they considered best for swallowing for each patient and judged residue on the voice prosthesis and in the upper esophagus. Raters were blinded to participant details, voice prosthesis type and scores of other raters. On patient self-evaluation, scores were equally distributed across all prostheses for swallowing. Experts most frequently chose the Blom Singer Low pressure and Blom Singer Classic Indwelling voice prostheses as best for swallowing but consensus was poor for most patients. Experts found that the Blom Singer Classic Indwelling and the Provox Vega had least residue on the voice prosthesis on thin liquid (p ≤ 0.001) and soft (p = 0.001), respectively. Experts also found that the Blom Singer Low Pressure had least residue in the upper esophagus on soft consistency (p ≤ 0.001). While self-evaluation by patients did not identify a consistently preferred prosthesis for swallow, many patients expressed personal preferences, suggesting benefits to involving patients in the choice of prosthesis. Some voice prostheses may be associated with lower levels of residue on the prosthesis and upper esophagus with certain consistencies

Processive Movement by a Kinesin Heterodimer with an Inactivating Mutation in One Head†

ABSTRACT: A single molecule of the motor enzyme kinesin-1 keeps a tight grip on its microtubule track, making tens or hundreds of discrete, unidirectional 8 nm steps before dissociating. This high duty ratio processive movement is thought to require a mechanism in which alternating stepping of the two head domains of the kinesin dimer is driven by alternating, overlapped cycles of ATP hydrolysis by the two heads. The R210K point mutation in Drosophila kinesin heavy chain was reported to disrupt the ability of the enzyme active site to catalyze ATP P-O bond cleavage. We expressed R210K homodimers as well as isolated R210K heads and confirmed that both are essentially inactive. We then coexpressed tagged R210K subunits with untagged wild-type subunits and affinity purified R210K/wild-type heterodimers together with the inactive R210K homodimers. In contrast to the R210K head or homodimer, the heterodimer was a highly active (&gt;50 % of wild-type) microtubule-stimulated ATPase, and the heterodimer displayed high duty ratio processive movement in single-molecule motility experiments. Thus, dimerization of a subunit containing the inactivating mutation with a functional subunit can complement the mutation; this must occur either by lowering or by bypassing kinetic barriers in the ATPase or mechanical cycles of the mutant head. The observations provide support for kinesin-1 gating mechanisms in which one head stimulates the rate of essential processes in the other