San Diego State University

About: San Diego State University is a education organization based out in San Diego, California, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 12418 authors who have published 27950 publications receiving 1192375 citations. The organization is also known as: SDSU & San Diego State College.

Polystyrene plastic: a source and sink for polycyclic aromatic hydrocarbons in the marine environment.

Abstract: Polycyclic aromatic hydrocarbons (PAHs) on virgin polystyrene (PS) and PS marine debris led us to examine PS as a source and sink for PAHs in the marine environment. At two locations in San Diego Bay, we measured sorption of PAHs to PS pellets, sampling at 0, 1, 3, 6, 9, and 12 months. We detected 25 PAHs using a new analytical method with comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry. Several congeners were detected on samples before deployment. After deployment, some concentrations decreased (1,3-dimethylnaphthalene and 2,6-methylnaphthalene), while most increased [2-methylanthracene and all parent PAHs (PPAHs), except fluorene and fluoranthene], suggesting that PS debris is a source and sink for PAHs. When sorbed concentrations of PPAHs on PS are compared to the five most common polymers [polyethylene terephthalate (PET), high-density polyethylene (HDPE), polyvinyl chloride (PVC), low-density polyethylene (LDPE), and polypropylene (PP)], PS sorbed greater concentrations than PP, PET, and PVC, similar to HDPE and LDPE. Most strikingly, at 0 months, PPAHs on PS ranged from 8 to 200 times greater than on PET, HDPE, PVC, LDPE, and PP. The combination of greater PAHs in virgin pellets and large sorption suggests that PS may pose a greater risk of exposure to PAHs upon ingestion.

Bacterial carbon processing by generalist species in the coastal ocean.

Abstract: Metagenomics, or environmental genomics, has revolutionized our picture of microorganisms in the real world — as opposed to how they behave in laboratory cultivated 'clonal' cultures. A novel example of 'experimental metagenomics' is now reported, involving the creation of a 20-litre microcosm of sea water collected off Sapelo Island in the US state of Georgia. Manipulation of the system shows that this coastal microbial community is dominated by metabolic generalists capable of utilizing a wide variety of organic compounds, rather than by bacterial species that specialize in metabolizing a specific component of the dissolved organic carbon pool. This finding has important implications for identifying taxon–function relationships for carbon cycle-relevant processes and the construction of predictive models of ocean biogeochemistry. Experimental metagenomics is used to show that coastal communities are populated by taxa capable of metabolizing a wide variety of organic carbon compounds. It is concluded that metabolic generalists dominate coastal microbial communities, with important implications for identifying taxon–function relationships for carbon cycle-relevant processes and the construction of predictive models of ocean biogeochemistry. The assimilation and mineralization of dissolved organic carbon (DOC) by marine bacterioplankton is a major process in the ocean carbon cycle1. However, little information exists on the specific metabolic functions of participating bacteria and on whether individual taxa specialize on particular components of the marine DOC pool2. Here we use experimental metagenomics to show that coastal communities are populated by taxa capable of metabolizing a wide variety of organic carbon compounds. Genomic DNA captured from bacterial community subsets metabolizing a single model component of the DOC pool (either dimethylsulphoniopropionate or vanillate) showed substantial overlap in gene composition as well as a diversity of carbon-processing capabilities beyond the selected phenotypes. Our direct measure of niche breadth for bacterial functional assemblages indicates that, in accordance with ecological theory, heterogeneity in the composition and supply of organic carbon to coastal oceans may favour generalist bacteria. In the important interplay between microbial community structure and biogeochemical cycling, coastal heterotrophic communities may be controlled less by transient changes in the carbon reservoir that they process and more by factors such as trophic interactions and physical conditions.

Cold season emissions dominate the Arctic tundra methane budget

Abstract: Arctic terrestrial ecosystems are major global sources of methane (CH4); hence, it is important to understand the seasonal and climatic controls on CH4 emissions from these systems. Here, we report year-round CH4 emissions from Alaskan Arctic tundra eddy flux sites and regional fluxes derived from aircraft data. We find that emissions during the cold season (September to May) account for ≥50% of the annual CH4 flux, with the highest emissions from noninundated upland tundra. A major fraction of cold season emissions occur during the “zero curtain” period, when subsurface soil temperatures are poised near 0 °C. The zero curtain may persist longer than the growing season, and CH4 emissions are enhanced when the duration is extended by a deep thawed layer as can occur with thick snow cover. Regional scale fluxes of CH4 derived from aircraft data demonstrate the large spatial extent of late season CH4 emissions. Scaled to the circumpolar Arctic, cold season fluxes from tundra total 12 ± 5 (95% confidence interval) Tg CH4 y−1, ∼25% of global emissions from extratropical wetlands, or ∼6% of total global wetland methane emissions. The dominance of late-season emissions, sensitivity to soil environmental conditions, and importance of dry tundra are not currently simulated in most global climate models. Because Arctic warming disproportionally impacts the cold season, our results suggest that higher cold-season CH4 emissions will result from observed and predicted increases in snow thickness, active layer depth, and soil temperature, representing important positive feedbacks on climate warming.

A description of the social–ecological framework used in the trial of activity for adolescent girls (TAAG)

Abstract: Social–ecological (SE) models are becoming more widely used in health behavior research. Applying SE models to the design of interventions is challenging because models must be tailor-made for each behavior and population, other theories need to be integrated into multilevel frameworks, and empirical research to guide model development is limited. The purpose of the present paper is to describe a SE framework that guided the intervention and measurement plans for a specific study. The trial of activity for adolescent girls (TAAG) is a multi-center study of interventions to reduce the decline of physical activity in adolescent girls. The TAAG framework incorporates operant learning theory, social cognitive theory, organizational change theory and the diffusion of innovation model in a multi-level model. The explicit and practical model developed for TAAG has already benefited the study and may have elements that can generalize to other health promotion studies.

Epidermal Microfluidic Electrochemical Detection System: Enhanced Sweat Sampling and Metabolite Detection

Abstract: Despite tremendous recent efforts, noninvasive sweat monitoring is still far from delivering its early analytical promise. Here, we describe a flexible epidermal microfluidic detection platform fabricated through hybridization of lithographic and screen-printed technologies, for efficient and fast sweat sampling and continuous, real-time electrochemical monitoring of glucose and lactate levels. This soft, skin-mounted device judiciously merges lab-on-a-chip and electrochemical detection technologies, integrated with a miniaturized flexible electronic board for real-time wireless data transmission to a mobile device. Modeling of the device design and sweat flow conditions allowed optimization of the sampling process and the microchannel layout for achieving attractive fluid dynamics and rapid filling of the detection reservoir (within 8 min from starting exercise). The wearable microdevice thus enabled efficient natural sweat pumping to the electrochemical detection chamber containing the enzyme-modified e...