Anthropogenic tracers, endocrine disrupting chemicals, and endocrine disruption in Minnesota lakes

Concentrations of endocrine disrupting chemicals and endocrine disruption in fish were determined in 11 lakes across Minnesota that represent a range of trophic conditions and land uses (urban, agricultural, residential, and forested) and in which wastewater treatment plant discharges were absent. Water, sediment, and passive polar organic integrative samplers (POCIS) were analyzed for steroidal hormones, alkylphenols, bisphenol A, and other organic and inorganic molecular tracers to evaluate potential non-point source inputs into the lakes. Resident fish from the lakes were collected, and caged male fathead minnows were deployed to evaluate endocrine disruption, as indicated by the biological endpoints of plasma vitellogenin and gonadal histology. Endocrine disrupting chemicals, including bisphenol A, 17β-estradiol, estrone, and 4-nonylphenol were detected in 90% of the lakes at part per trillion concentrations. Endocrine disruption was observed in caged fathead minnows and resident fish in 90% of the lakes. The widespread but variable occurrence of anthropogenic chemicals in the lakes and endocrine disruption in fish indicates that potential sources are diverse, not limited to wastewater treatment plant discharges, and not entirely predictable based on trophic status and land use.     

A new route for mass production of uniform metal nanoparticles in water by means of laser light induced processes

In this contribution, we report a new route for mass fabrication of metal nanoparticles with monodisperse shape and narrow size distribution in water applying exclusively physical processes. For this purpose, we have combined pulsed laser ablation with the technique of selective laser tailoring. For example, pulsed laser ablation from a gold plate in water results in a large amount of nanoparticles with radii in the range of R = 75 nm with a relatively broad size distribution of sigma = 31%. This broad size distribution has been subsequently narrowed in a single irradiation step to sigma = 20% without a significant change of the mean nanoparticle radius utilizing selective laser tailoring. The main advantage of the laser based process, besides rapid processing, is that no chemicals, which are undesired for many applications, are necessary. Hence, mass production of nanoparticles with narrow size and monodisperse shape distribution in water becomes feasible.     

Comparison of pressure and heat resistance of Clostridium botulinum and other endospores in mashed carrots

Inactivation of bacterial endospores in food requires a combination of pressure and moderate heat. Endospore resistance of seven Clostridium botulinum strains was compared with those of Bacillus spp. (B. cereus, B. subtilis, B. licheniformis, B. smithii, B. amyloliquefaciens) and Thermoanaerobacterium thermosaccharolyticum with respect to pressure (600 to 800 MPa) and temperature (80 to 116 degrees C) treatments in mashed carrots. A large variation was observed in the pressure resistance of C. botulinum spores. Their reduction after treatments with 600 MPa at 80 degrees C for 1 s ranged from more than 5.5 log units to no reduction. Spores of the proteolytic C. botulinum TMW 2.357 exhibited a greater resistance to pressure than spores from all other bacteria examined, with the exception of B. amyloliquefaciens. Heat resistance of spores did not correlate with pressure resistance, either within strains of C. botulinum or when C. botulinum spores were compared with spores of T. thermosaccharolyticum. A quantitative release of dipicolinic acid was observed from C. botulinum spores on combined pressure and temperature treatments only after inactivation of more than 99.999% of the spores. Thus, dipicolinic acid is released by a physicochemical rather than a physiological process. The resistance of spores to combined pressure and temperature treatments correlated with their ability to retain dipicolinic acid. B. amyloliquefaciens, a mesophilic organism that forms highly pressure-resistant spores is proposed as a nonpathogenic target organism for high-pressure process development.     

Effect of Absolute Configuration on the Optical and NMR Properties of Oligonucleotides Containing Benzo[a]Pyrene Adducts at N 6 of Deoxyadenosine

For oligonucleotide duplexes derived from trans opening of benzo[a]pyrene diol epoxides (BaP DEs) by the exocyclic N⁶-amino group of deoxyadenosine (dA), the hydrocarbon is intercalated toward the 5′-end of the modified strand when the configuration at the site of attachment of the base to the hydrocarbon (C-10) is R, and toward the 3′-end when this configuration is S. In oligonucleotide 11-mer duplexes modified by BaP DE-1 (benzylic 7-OH and epoxide oxygen cis) and DE-2 (7-OH and epoxide oxygen trans), as well as 7,8,9,10-tetrahydro BaP 9,10-epoxide, 10R adducts had consistently higher (5–9d°C) T_m values than the corresponding 10S adducts. Dodecamer duplexes from the HPRT gene with trans opened 10S (but not those with 10R) BaP DE-2 adducts at either of two adjacent dA residues exhibited blue shifts at ～350 nm at temperatures well below the T_m. We propose that these blue shifts result from a conformation in which the hydrocarbon is not stacked with the DNA bases.     

Sintering behavior,microstructure and thermoelectric properties of calcium cobaltite thick films for transversal thermoelectric multilayer generators

The sintering behavior and the thermoelectric performance of Ca₃Co₄O₉ multilayer laminates were studied, and a multilayer thermoelectric generator was fabricated. Compacts and multilayer samples with anisotropic microstructure and residual porosity were obtained after conventional sintering at 920 °C, whereas dense and isotropic multilayer samples were prepared by firing at 1200 °C and reoxidation at 900 °C. A hot-pressed sample has a dense and anisotropic microstructure. Samples sintered at 920 °C exhibit low electrical conductivity due to the low density, whereas the Seebeck coefficient is not sensitive to preparation conditions. However, thermal conductivity of multilayers is very low, and, hence acceptable ZT values are obtained. A transversal multilayer thermoelectric generator (TMLTEG) was fabricated by stacking layers of Ca₃Co₄O₉ green tapes, AgPd conductor printing, and co-firing at 920 °C. The TMLTEG has a power output of 3 mW at ΔT = 200 K in the temperature interval of 25 °C to 300 °C.