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- Member of: ASU Regents' Professors Open Access Works
- Member of: Harold Heath Collection
Description
Using a CH[subscript 4]-based membrane biofilm reactor (MBfR), we studied perchlorate (ClO[subscript 4]–) reduction by a biofilm performing anaerobic methane oxidation coupled to denitrification (ANMO-D). We focused on the effects of nitrate (NO[subscript 3]–) and nitrite (NO[subscript 2]–) surface loadings on ClO[subscript 4]– reduction and on the biofilm community’s mechanism for ClO[subscript 4]– reduction. The ANMO-D biofilm reduced up to 5 mg/L of ClO[subscript 4]– to a nondetectable level using CH[subscript 4] as the only electron donor and carbon source when CH[subscript 4] delivery was not limiting; NO[subscript 3]– was completely reduced as well when its surface loading was ≤0.32 g N/m[superscript 2]-d. When CH[subscript 4] delivery was limiting, NO[subscript 3]– inhibited ClO[subscript 4]– reduction by competing for the scarce electron donor. NO[subscript 2]– inhibited ClO[subscript 4]– reduction when its surface loading was ≥0.10 g N/m[superscript 2]-d, probably because of cellular toxicity. Although Archaea were present through all stages, Bacteria dominated the ClO[subscript 4]–-reducing ANMO-D biofilm, and gene copies of the particulate methane mono-oxygenase (pMMO) correlated to the increase of respiratory gene copies. These pieces of evidence support that ClO[subscript 4]– reduction by the MBfR biofilm involved chlorite (ClO[subscript 2]–) dismutation to generate the O[subscript 2] needed as a cosubstrate for the mono-oxygenation of CH[subscript 4].
ContributorsLuo, Yi-Hao (Author) / Chen, Ran (Author) / Wen, Li-Lian (Author) / Meng, Fan (Author) / Zhang, Yin (Author) / Lai, Chun-Yu (Author) / Rittmann, Bruce (Author) / Zhao, He-Ping (Author) / Zheng, Ping (Author) / Biodesign Institute (Contributor) / Swette Center for Environmental Biotechnology (Contributor)
Created2015-02-17
Description
Aim
To establish a chronology for late Quaternary avian extinction, extirpation and persistence in the Bahamas, thereby testing the relative roles of climate change and human impact as causes of extinction.
Location
Great Abaco Island (Abaco), Bahamas, West Indies.
Methods
We analysed the resident bird community as sampled by Pleistocene (> 11.7 ka) and Holocene (< 11.7 ka) fossils. Each species was classified as extinct (lost globally), extirpated (gone from Abaco but persists elsewhere), or extant (still resident on Abaco). We compared patterns of extinction, extirpation and persistence to independent estimates of climate and sea level for glacial (late Pleistocene) and interglacial (Holocene) times.
Results
Of 45 bird species identified in Pleistocene fossils, 25 (56%) no longer occur on Abaco (21 extirpated, 4 extinct). Of 37 species recorded in Holocene deposits, 15 (14 extirpated, 1 extinct; total 41%) no longer exist on Abaco. Of the 30 extant species, 12 were recovered as both Pleistocene and Holocene fossils, as were 9 of the 30 extirpated or extinct species. Most of the extinct or extirpated species that were only recorded from Pleistocene contexts are characteristic of open habitats (pine woodlands or grasslands); several of the extirpated species are currently found only where winters are cooler than in the modern or Pleistocene Bahamas. In contrast, most of the extinct or extirpated species recorded from Holocene contexts are habitat generalists.
Main conclusions
The fossil evidence suggests two main times of late Quaternary avian extirpation and extinction in the Bahamas. The first was during the Pleistocene–Holocene transition (PHT; 15–9 ka) and was fuelled by climate change and associated changes in sea level and island area. The second took place during the late Holocene (< 4 ka, perhaps primarily < 1 ka) and can be attributed to human impact. Although some species lost during the PHT are currently found where climates are cooler and drier than in the Bahamas today, a taxonomically and ecologically diverse set of species persisted through that major climate change but did not survive the past millennium of human presence.
ContributorsSteadman, David W. (Author) / Franklin, Janet (Author) / College of Liberal Arts and Sciences (Contributor) / School of Geographical Sciences and Urban Planning (Contributor)
Created2015-03-01
Description
UV photolysis was used to relieve inhibition of biomass growth by sulfadiazine (SD), a broad-spectrum anti-microbial. To investigate the effects of SD on biomass growth, three substrates—glucose alone (G), glucose plus sulfadiazine (G+SD), and glucose plus photolyzed SD (G+PSD)—were used to culture the bacteria acclimated to glucose. The biomass was strongly inhibited when SD was added into the glucose solution, but inhibition was relieved to a significant degree when the SD was treated with UV irradiation as a pretreatment. The biomass growth kinetics were described well by the Monod model when glucose was used as a substrate alone, but the kinetics followed a hybrid Aiba model for non-competitive inhibition when SD was added to the solution. When photolyzed SD was added to glucose solution to replace original SD, the growth still followed Aiba inhibition, but inhibition was significantly relieved: the maximum specific growth rate (μ[subscript max]) increased by 17 %, and the Aiba inhibition concentration increased by 60 %. Aniline, a major product of UV photolysis, supported the growth of the glucose-biodegrading bacteria. Thus, UV photolysis of SD significantly relieved inhibition by lowering the SD concentration and by generating a biodegradable product.
ContributorsPan, Shihui (Author) / Yan, Ning (Author) / Zhang, Yongming (Author) / Rittmann, Bruce (Author) / Biodesign Institute (Contributor) / Swette Center for Environmental Biotechnology (Contributor)
Created2015-05-01
Description
In the face of rising rates of substance use among Mexican youth and rapidly narrowing gender differences in use, substance use prevention is an increasingly urgent priority for Mexico. Prevention interventions have been implemented in Mexico but few have been rigorously evaluated for effectiveness. This article presents the long term effects of a Mexico-based pilot study to test the feasibility of a linguistically specific (Mexican Spanish) adapted version of keepin’ it REAL, a school-based substance abuse prevention model program. University affiliated researchers from Mexico and the US collaborated on the study design, program implementation, data collection, and analysis. Students and their teachers from two middle schools (secundarias) in Guadalajara participated in this field trial of Mantente REAL (translated to Spanish). The schools were randomly assigned to treatment and control conditions. The sample of 431 students reported last 30 day substance use at three times (one pretest and two posttests). Changes in substance use behaviors over time were examined using growth curve models. Long term desired intervention effects were found for alcohol and marijuana use but not for cigarettes. The intervention effects were greater for girls than for boys in slowing the typical developmental increase over time in alcohol use. Marijuana effects were based on small numbers of users and indicate a need for larger scale studies. These findings suggest that keepin’ it REAL is a promising foundation for cultural program adaptation efforts to create efficacious school-based universal prevention interventions for middle school students in Mexico.
ContributorsMarsiglia, Flavio (Author) / Kulis, Stephen (Author) / Booth, Jaime (Author) / Nuno-Gutierrez, Bertha L. (Author) / Robbins, Danielle (Author) / College of Public Service and Community Solutions (Contributor) / School of Social Work (Contributor) / College of Liberal Arts and Sciences (Contributor) / Sanford School of Social and Family Dynamics (Contributor) / Southwest Interdisciplinary Research Center (Contributor)
Created2015-04-01
Description
Sustainable production of microalgae for biofuel requires efficient phosphorus (P) utilization, which is a limited resource and vital for global food security. This research tracks the fate of P through biofuel production and investigates P recovery from the biomass using the cyanobacterium Synechocystis sp. PCC 6803. Our results show that Synechocystis contained 1.4% P dry weight. After crude lipids were extracted (e.g., for biofuel processing), 92% of the intracellular P remained in the residual biomass, indicating phospholipids comprised only a small percentage of cellular P. We estimate a majority of the P is primarily associated with nucleic acids. Advanced oxidation using hydrogen peroxide and microwave heating released 92% of the cellular P into orthophosphate. We then recovered the orthophosphate from the digestion matrix using two different types of anion exchange resins. One resin impregnated with iron nanoparticles adsorbed 98% of the influent P through 20 bed volumes, but only released 23% during regeneration. A strong-base anion exchange resin adsorbed 87% of the influent P through 20 bed volumes and released 50% of it upon regeneration. This recovered P subsequently supported growth of Synechocystis. This proof-of-concept recovery process reduced P demand of biofuel microalgae by 54%.
ContributorsGifford, McKay (Author) / Liu, Jianyong (Author) / Rittmann, Bruce (Author) / Vannela, Raveender (Author) / Westerhoff, Paul (Author) / Ira A. Fulton Schools of Engineering (Contributor) / School of Sustainable Engineering and the Built Environment (Contributor) / Biodesign Institute (Contributor) / Swette Center for Environmental Biotechnology (Contributor)
Created2015-03-01
Description
Preserving a system’s viability in the presence of diversity erosion is critical if the goal is to sustainably support biodiversity. Reduction in population heterogeneity, whether inter- or intraspecies, may increase population fragility, either decreasing its ability to adapt effectively to environmental changes or facilitating the survival and success of ordinarily rare phenotypes. The latter may result in over-representation of individuals who may participate in resource utilization patterns that can lead to over-exploitation, exhaustion, and, ultimately, collapse of both the resource and the population that depends on it. Here, we aim to identify regimes that can signal whether a consumer–resource system is capable of supporting viable degrees of heterogeneity. The framework used here is an expansion of a previously introduced consumer–resource type system of a population of individuals classified by their resource consumption. Application of the Reduction Theorem to the system enables us to evaluate the health of the system through tracking both the mean value of the parameter of resource (over)consumption, and the population variance, as both change over time. The article concludes with a discussion that highlights applicability of the proposed system to investigation of systems that are affected by particularly devastating overly adapted populations, namely cancerous cells. Potential intervention approaches for system management are discussed in the context of cancer therapies.
ContributorsKareva, Irina (Author) / Morin, Benjamin (Author) / Castillo-Chavez, Carlos (Author) / Simon M. Levin Mathematical, Computational and Modeling Sciences Center (Contributor) / College of Liberal Arts and Sciences (Contributor) / School of Human Evolution and Social Change (Contributor) / Julie Ann Wrigley Global Institute of Sustainability (Contributor)
Created2015-02-01
Description
Wall-bounded turbulence manifests itself in a broad range of applications, not least of which in hydraulic systems. Here we briefly review the significant advances over the past few decades in the fundamental study of wall turbulence over smooth and rough surfaces, with an emphasis on coherent structures and their role at high Reynolds numbers. We attempt to relate these findings to parallel efforts in the hydraulic engineering community and discuss the implications of coherent structures in important hydraulic phenomena.
ContributorsAdrian, Ronald (Author) / Marusic, Ivan (Author) / Ira A. Fulton Schools of Engineering (Contributor) / School for the Engineering of Matter, Transport and Energy (Contributor)
Created2012-09-10
Description
Vortex organization in the outer layer of a turbulent boundary layer overlying sparse, hemispherical roughness elements is explored with two-component particle-image velocimetry (PIV) in multiple streamwise-wall-normal measurement planes downstream and between elements. The presence of sparse roughness elements causes a shortening of the streamwise length scale in the near-wall region. These measurements confirm that vortex packets exist in the outer layer of flow over rough walls, but that their organization is altered, and this is interpreted as the underlying cause of the length-scale reduction. In particular, the elements shed vortices which appear to align in the near-wall region, but are distinct from the packets. Further, it is observed that ejection events triggered in the element wakes are more intense compared to the ejection events in smooth wall. We speculate that this may initiate a self-sustaining mechanism leading to the formation of hairpin packets as a much more effective instability compared to those typical of smooth-wall turbulence.
ContributorsGuala, Michael (Author) / Tomkins, Christopher D. (Author) / Christensen, Kenneth T. (Author) / Adrian, Ronald (Author) / Ira A. Fulton Schools of Engineering (Contributor) / School for the Engineering of Matter, Transport and Energy (Contributor)
Created2012-09-09
Description
The dynamic importance of spanwise vorticity and vortex filaments has been assessed in steady, uniform open-channel flows by means of particle image velocimetry (PIV). By expressing the net force due to Reynolds’ turbulent shear stress, ∂(−[bar over uv]) ∂y, in terms of two velocity-vorticity correlations, [bar over vω[subscript z]] and [bar over wω[subscript y]], the results show that both spanwise vorticity [bar over ω[subscript z]] and the portion of it that is due to spanwise filaments make important contributions to the net force and hence the shape of the mean flow profile. Using the swirling strength to identify spanwise vortex filaments, it is found that they account for about 45% of [bar over vω[subscript z]], the remainder coming from non-filamentary spanwise vorticity, i.e. shear. The mechanism underlying this contribution is the movement of vortex filaments away from the wall. The contribution of spanwise vortex filaments to the Reynolds stress is small because they occupy a small fraction of the flow. The contribution of the induced motion of the spanwise vortex filaments is significant.
ContributorsChen, Qigang (Author) / Adrian, Ronald (Author) / Zhong, Qiang (Author) / Li, Danxun (Author) / Wang, Xingkui (Author) / Ira A. Fulton Schools of Engineering (Contributor) / School for the Engineering of Matter, Transport and Energy (Contributor)
Created2013-11-30
Description
Herbivores face various nutritional challenges in their life cycles, challenges that may become increasingly acute under ongoing environmental changes.
Here, focusing on calcium, phosphorus and nitrogen, we used nutritional geometry to analyse individual-based data on foraging and extraction efficiencies, and combined these with data on reproduction and migratory behaviour to understand how a large herbivorous carnivore can complete its life cycle on a narrow and seemingly low quality bamboo diet.
Behavioural results showed that pandas during the year switched between four main food categories involving the leaves and shoots of two bamboo species available. Nutritional analysis suggests that these diet shifts are related to the concentrations and balances of calcium, phosphorus and nitrogen. Notably, successive shifts in range use and food type corresponded with a transition to higher concentrations and/or a more balanced intake of these multiple key constituents.
Our study suggests that pandas obligatorily synchronize their seasonal migration and reproduction with the disjunct nutritional phenologies of two bamboo species. This finding has potentially important implications for habitat conservation for this species and, more generally, draws attention to the need for understanding the nutritional basis of food selection in devising management plans for endangered species.
Here, focusing on calcium, phosphorus and nitrogen, we used nutritional geometry to analyse individual-based data on foraging and extraction efficiencies, and combined these with data on reproduction and migratory behaviour to understand how a large herbivorous carnivore can complete its life cycle on a narrow and seemingly low quality bamboo diet.
Behavioural results showed that pandas during the year switched between four main food categories involving the leaves and shoots of two bamboo species available. Nutritional analysis suggests that these diet shifts are related to the concentrations and balances of calcium, phosphorus and nitrogen. Notably, successive shifts in range use and food type corresponded with a transition to higher concentrations and/or a more balanced intake of these multiple key constituents.
Our study suggests that pandas obligatorily synchronize their seasonal migration and reproduction with the disjunct nutritional phenologies of two bamboo species. This finding has potentially important implications for habitat conservation for this species and, more generally, draws attention to the need for understanding the nutritional basis of food selection in devising management plans for endangered species.
ContributorsNie, Yonggang (Author) / Zhang, Zejun (Author) / Raubenheimer, David (Author) / Elser, James (Author) / Wei, Wei (Author) / Wei, Fuwen (Author) / College of Liberal Arts and Sciences (Contributor) / School of Life Sciences (Contributor)
Created2015-01-01