Preparing future engineers for challenges of the 21st century: Sustainable engineering

The field of engineering is changing rapidly as the growing global population puts added demands on the earth's resources: engineering decisions must now account for limitations in materials and energy as well as the need to reduce discharges of wastes. This means educators must revise courses and curricula so engineering graduates are prepared for the new challenges as practicing engineers. The Center for Sustainable Engineering has been established to help faculty members accommodate such changes through workshops and new educational materials, including a free access website with peer-reviewed materials.     

Determinants of chorus tenure in barking treefrogs (Hyla gratiosa)

In all species of anuran amphibians studied to date, male mating success is positively correlated with male chorus tenure (the number of nights that a male is present in breeding aggregations), yet males spend only a small portion of the total breeding season in choruses. Three hypotheses might explain abbreviated chorus tenure in anuran amphibians: (1) mortality, (2) energy limitations, and (3) movement among choruses. I tested these hypotheses in a study of the barking treefrog (Hyla gratiosa), a species with very abbreviated chorus tenure. Mortality accounted for the short tenures of some males: an estimated 20% of males died while calling in the chorus. Energy limitations were an important determinant of chorus tenure. Males lost weight over successive nights in the chorus, and males with longer chorus tenures were in better condition on their first night in the chorus, lost condition more slowly, and were in poorer condition on their last night in the chorus than were males with shorter chorus tenures. Males that I fed crickets as they left the chorus returned sooner and for more nights than did control (unfed) males. Movement between ponds did not explain abbreviated chorus tenure: less than 16% of the males called at more than one pond, and these males increased their chorus tenures by a median of only 2.5 nights by calling in another chorus. Thus, abbreviated chorus tenure in H. gratiosa appears to be primarily the result of energy limitations, with mortality playing a secondary role.     

Determination of selected fate and aquatic toxicity characteristics of acrylic acid and a series of acrylic esters

Acrylic acid, methyl acrylate, ethyl acrylate, and butyl acrylate are commercially important and widely used materials. This paper reports the results of a series of fate and aquatic toxicity studies. The mobility in soil of acrylic acid and its esters ranged from 'medium' to 'very high'. Calculated bioconcentration factors ranged from 1 to 37, suggesting a low bioconcentration potential. Acrylic acid and methyl acrylate showed limited biodegradability in the five day biochemical oxygen demand (BOD5) test, while ethyl acrylate and butyl acrylate were degraded easily (77% and 56%, respectively). Using the OECD method 301D 28-d closed bottle test, degradability for acrylic acid was 81% at 28 days, while the acrylic esters ranged from 57% to 60%. Acrylic acid degraded rapidly to carbon dioxide in soil (t1/2 < 1 day). Toxicity tests were conducted using freshwater and marine fish, invertebrates, and algae. Acrylic acid effect concentrations for fish and invertebrates ranged from 27 to 236 mg/l. Effect concentrations (LC50 or EC50) for fish and invertebrates using methyl acrylate, ethyl acrylate, and butyl acrylate ranged from 1.1 to 8.2 mg/l. The chronic MATC for acrylic acid with Daphnia magna was 27 mg/l based on length and young produced per adult reproduction day and for ethyl acrylate was 0.29 mg/l based on both the reproductive and growth endpoints. Overall these studies show that acrylic acid and the acrylic esters studied can rapidly biodegrade, have a low potential for persistence or bioaccumulation in the environment, and have low to moderate toxicity.     

Migration behavior of naturally occurring radionuclides at the Nopal I uranium deposit, Chihuahua, Mexico

Oxidation of pyrite at the Nopal I uranium deposit, Peña Blanca district, Chihuahua, Mexico has resulted in the formation of Fe-oxides/hydroxides. Anomalous U concentrations (i.e. several hundred to several thousand ppm) measured in goethite, hematite, and amorphous Fe-oxyhydroxides in a major fracture that crosscuts the deposit and the absence of U minerals in the fracture suggest that U was retained during secondary mineral growth or sorbed on mineral surfaces. Mobilization and transport of U away from the deposit is suggested by decreasing U concentrations in fracture-infilling materials and in goethite and hematite with distance from the deposit. Greater than unity ²³⁴U/²³⁸U activity ratios measured in fracture-infilling materials indicate relatively recent ( < 1 Ma) U uptake from fluids that carried excess ²³⁴U. Systematic decreases in ²³⁴U/²³⁸U activity ratios of fracture materials with distance from the deposit suggest a multistage mobilization process, such as remobilization of U from ²³⁴U-enriched infill minerals or differential or diminished transport of U-bearing solutions containing excess ²³⁴U.     

Biotransformation of the fungicide pentachloronitrobenzene by Tetrahymenathermophila

The protozoan, $\text{Tetrahymena}$$\text{thermophila}$, metabolizes pentachloronitrobenzene to several products, including nitrite, pentachlorothioanisole and pentachloroaniline. The latter two metabolites were identified by gas chromatographymass spectrometry. Pentachlorothioanisole may be produced via a glutathione-dependent pathway, and two key enzymes of this pathway, glutathione transferase and thiol S-methyltransferase, have been detected in crude extracts of this microorganism.     

Place and exile: resource conflicts and sustainability in Gaelic Ireland and Scotland

This paper reflects on two controversial resource projects – the Bellanaboy gas refinery (Ireland) and the Barvas Moor wind farm (Scotland) – and critical arguments made by key local actors. Although risk, health, environment and development dominated the official decision-making processes, these actors articulated views which cut across or existed beyond such orthodox ideas and framings. Focusing on these, I show that the Gaelic concepts of dùthchas and deoraíocht, summarised as place and exile, help to explain why some residents decided to protest. This paper illustrates the role that history, culture and language can play in conflicts, emphasises the need for greater sensitivity to these and suggests that place and exile can inform alternative visions of sustainability.     

Metachronal swimming in Antarctic krill: gait kinematics and system design

Metachronal swimming, in which adjacent appendages stroke in sequence, is widespread among crustaceans inhabiting the transitional flow realm in which both viscosity and inertia effects are important. However, the design and operation of this propulsion system in response to various hydrodynamic, energetic, and behavioral needs have not been well investigated. We examine free-swimming Antarctic krill (Euphausia superba) as a model species and identify three distinct behavioral swimming gaits. The pleopod kinematics of these gaits, hovering, fast-forward swimming, and upside-down swimming, are quantified via image analysis of high-speed video. Pleopod stroke amplitude and frequency were found to vary significantly among these swimming modes. In order to increase swimming speed, krill were found first to increase stroke amplitude and secondarily to increase beat frequency. The kinematics of these distinct swimming modes provide insight as we consider multi-appendage metachronal swimming from a design standpoint. The ratio of the distance between adjacent appendage bases and appendage length is identified as a key parameter in metachrony, the value of which is constrained to a narrow range for a wide variety of species.