Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons

Open Access. Powered by Scholars. Published by Universities.®

Articles 1 - 8 of 8

Full-Text Articles in Physical Sciences and Mathematics

Homogenization Techniques For Population Dynamics In Strongly Heterogeneous Landscapes, Brian P. Yurk, Christina A. Cobbold Dec 2017

Homogenization Techniques For Population Dynamics In Strongly Heterogeneous Landscapes, Brian P. Yurk, Christina A. Cobbold

Faculty Publications

An important problem in spatial ecology is to understand how population-scale patterns emerge from individual-level birth, death, and movement processes. These processes, which depend on local landscape characteristics, vary spatially and may exhibit sharp transitions through behavioural responses to habitat edges, leading to discontinuous population densities. Such systems can be modelled using reaction–diffusion equations with interface conditions that capture local behaviour at patch boundaries. In this work we develop a novel homogenization technique to approximate the large-scale dynamics of the system. We illustrate our approach, which also generalizes to multiple species, with an example of logistic growth within a periodic …


Hydrogen-Bonding-Directed Ordered Assembly Of Carboxylated Poly(3-Alkylthiophene)S, David W. Bilger, Jose A. Figueroa, Neil D. Redeker, Amrita Sarkar, Morgan Stefik, Shanjuu Zhang Nov 2017

Hydrogen-Bonding-Directed Ordered Assembly Of Carboxylated Poly(3-Alkylthiophene)S, David W. Bilger, Jose A. Figueroa, Neil D. Redeker, Amrita Sarkar, Morgan Stefik, Shanjuu Zhang

Faculty Publications

Hydrogen-bonding-induced ordered assembly of poly(3-alkylthiophene)s derivatives bearing carboxylic acid groups has been investigated from diluted and concentrated solutions to solid films using ultraviolet–visible absorption spectroscopy, polarized optical microscopy, and four-point probe conductivity measurements. In dilute solutions, the polymer undergoes a spontaneous structural transition from disordered coil-like to ordered rodlike conformations, which is evidenced by time-dependent chromism. Many factors such as alkyl-chain length, types of solvents, and temperature are studied to understand the assembly behavior. Transition kinetics of the assembly process reveals a universal second-order rate law, indicating an intermolecular origin due to hydrogen bonding. When more concentrated, hydrogen bonding drives …


Blockade Of Cb1 Cannabinoid Receptor Alters Gut Microbiota And Attenuates Inflammation And Diet-Induced Obesity, Pegah Mehrpouya-Bahrami, Kumaraswamy Naidu Chitrala, Mitra S. Ganewatta, Chuanbing Tang, E Angela Murphy, Reilly Enos, Kandy T. Velazquez, Jamie Mccellan, Mitzi Nagarkatti, Prakash Nagarkatti Nov 2017

Blockade Of Cb1 Cannabinoid Receptor Alters Gut Microbiota And Attenuates Inflammation And Diet-Induced Obesity, Pegah Mehrpouya-Bahrami, Kumaraswamy Naidu Chitrala, Mitra S. Ganewatta, Chuanbing Tang, E Angela Murphy, Reilly Enos, Kandy T. Velazquez, Jamie Mccellan, Mitzi Nagarkatti, Prakash Nagarkatti

Faculty Publications

Obesity is characterized by chronic low-grade, systemic inflammation, altered gut microbiota, and gut barrier disruption. Additionally, obesity is associated with increased activity of endocannabinoid system (eCB). However, the clear connection between gut microbiota and the eCB system in the regulation of energy homeostasis and adipose tissue inflammation and metabolism, remains to be established. We investigated the effect of treatment of mice with a cannabinoid receptor 1 (CB1) antagonist on Diet-Induced Obesity (DIO), specifically whether such a treatment that blocks endocannabinoid activity can induce changes in gut microbiota and anti-inflammatory state in adipose tissue. Blockade of CB1 attenuated DIO, inflammatory cytokines …


A Lab-On-Chip Phosphate Analyzer For Long-Term In Situ Monitoring At Fixed Observatories: Optimization And Performance Evaluation In Estuarine And Oligotrophic Coastal Waters, Maxime Grand, Geraldine Clinton-Bailey, Alexander Beaton, Allison Schaap, Thomas Johengen, Mario Tamburri, Douglas Connelly, Matthew Mowlem, Eric Achterberg Aug 2017

A Lab-On-Chip Phosphate Analyzer For Long-Term In Situ Monitoring At Fixed Observatories: Optimization And Performance Evaluation In Estuarine And Oligotrophic Coastal Waters, Maxime Grand, Geraldine Clinton-Bailey, Alexander Beaton, Allison Schaap, Thomas Johengen, Mario Tamburri, Douglas Connelly, Matthew Mowlem, Eric Achterberg

Faculty Publications

The development of phosphate sensors suitable for long-term in situdeployments in natural waters, is essential to improve our understanding of the distribution, fluxes, and biogeochemical role of this key nutrient in a changing ocean. Here, we describe the optimization of the molybdenum blue method for in situ work using a lab-on-chip (LOC) analyzer and evaluate its performance in the laboratory and at two contrasting field sites. The in situ performance of the LOC sensor is evaluated using hourly time-series data from a 56-day trial in Southampton Water (UK), as well as a month-long deployment in the subtropical oligotrophic waters of …


Strong Linkages Between Surface And Deep-Water Dissolved Organic Matter In The East/Japan Sea, Tae-Hoon Kim, Guebuem Kim, Yuan Shen, Ronald Benner May 2017

Strong Linkages Between Surface And Deep-Water Dissolved Organic Matter In The East/Japan Sea, Tae-Hoon Kim, Guebuem Kim, Yuan Shen, Ronald Benner

Faculty Publications

Vertical and horizontal distributions of total dissolved amino acids (TDAAs), dissolved organic carbon (DOC), and dissolved organic nitrogen (DON) were measured in the East/Japan Sea (EJS). The euphotic zone of this sea is N-limited, and the N : P ratio is ∼ 13 below 200 m depth. Elevated TDAA concentrations (137 ± 34 nM) and DOC-normalized yields (0.8 ± 0.2 % of DOC) were observed in deep waters ( ≥  1000 m) of the EJS and compared with those in the deep North Pacific Ocean. Significantly high TDAA concentrations and yields were observed in a region of deep-water formation, indicating …


Time Lags Associated With Effects Of Oceanic Conditions On Seabird Breeding In The Salish Sea Region Of The Northern California Current System, Rashida S. Smith, Lynelle M. Weldon, James L. Hayward, Shandelle M. Henson Apr 2017

Time Lags Associated With Effects Of Oceanic Conditions On Seabird Breeding In The Salish Sea Region Of The Northern California Current System, Rashida S. Smith, Lynelle M. Weldon, James L. Hayward, Shandelle M. Henson

Faculty Publications

No abstract provided.


Hierarchical Corannulene-Based Materials: Energy Transfer And Solid-State Photophysics, Allison M. Rice, W. Brett Fellows, Ekaterina A. Dolgopolova, Andrew B. Greytak, Aaron K. Vannucci, Mark D. Smith, Stavros G. Karakalos, Jeanette A. Krause, Stanislav M. Avdoshenko, Alexey A. Popov, Natalia B. Shustova Prof. Dr. Mar 2017

Hierarchical Corannulene-Based Materials: Energy Transfer And Solid-State Photophysics, Allison M. Rice, W. Brett Fellows, Ekaterina A. Dolgopolova, Andrew B. Greytak, Aaron K. Vannucci, Mark D. Smith, Stavros G. Karakalos, Jeanette A. Krause, Stanislav M. Avdoshenko, Alexey A. Popov, Natalia B. Shustova Prof. Dr.

Faculty Publications

We report the first example of a donor–acceptor corannulene-containing hybrid material with rapid ligand-to-ligand energy transfer (ET). Additionally, we provide the first time-resolved photoluminescence (PL) data for any corannulene-based compounds in the solid state. Comprehensive analysis of PL data in combination with theoretical calculations of donor–acceptor exciton coupling was employed to estimate ET rate and efficiency in the prepared material. The ligand-to-ligand ET rate calculated using two models is comparable with that observed in fullerene-containing materials, which are generally considered for molecular electronics development. Thus, the presented studies not only demonstrate the possibility of merging the intrinsic properties of π-bowls, …


Climate Warming Can Accelerate Carbon Fluxes Without Changing Soil Carbon Stocks, Susan E. Ziegler, Ronald Benner, Sharon A. Billings, Kate A. Edwards, Michael Philben, Xinbiao Zhu, Jerome Laganière Feb 2017

Climate Warming Can Accelerate Carbon Fluxes Without Changing Soil Carbon Stocks, Susan E. Ziegler, Ronald Benner, Sharon A. Billings, Kate A. Edwards, Michael Philben, Xinbiao Zhu, Jerome Laganière

Faculty Publications

Climate warming enhances multiple ecosystem C fluxes, but the net impact of changing C fluxes on soil organic carbon (SOC) stocks over decadal to centennial time scales remains unclear. We investigated the effects of climate on C fluxes and soil C stocks using space-for-time substitution along a boreal forest climate gradient encompassing spatially replicated sites at each of three latitudes. All regions had similar SOC concentrations and stocks (5.6 to 6.7 kg C m−2). The three lowest latitude forests exhibited the highest productivity across the transect, with tree biomass:age ratios and litterfall rates 300 and 125% higher than those in …