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The isotopic composition of water in hydrated minerals, such as gypsum and jarosite, has numerous applications in studies of recent climate change, ore formation, and soil development. However, oxygen and hydrogen isotope analysis of water of crystallization is currently a complex procedure. Commonly used techniques involve offline extraction of water from hydrated minerals and subsequent isotope analysis. Such methods are time-consuming, require relatively large sample sizes, and the stepwise procedure has to be carried out with extreme caution to avoid erroneous results. We present a novel online method for the oxygen and hydrogen isotope analysis of water of crystallization in hydrous minerals. Gypsum (CaS[O.sub.4] x 2[H.sub.2]O) samples, 2 mg in size, are reacted in a simply modified carbon reducing furnace connected to a continuous-flow mass spectrometer system. Analysis time is less than 10 min/sample. The precision (2 std dev mean) of our method for 2-mg gypsum (30 [micro]mol of [H.sup.2]O) samples is 0.3 [per thousand] for oxygen and less than 1.4 [per thousand] for hydrogen isotope measurements. For oxygen isotope analysis alone, samples as small as 0.2 mg of gypsum can be analyzed with a precision of 0.3 [per thousand].

Sulfur isotope measurements offer comprehensive information on the origin and history of natural materials. Tunable laser spectroscopy is a powerful analytical technique for isotope analysis that has proven itself readily adaptable for in situ terrestrial and planetary measurements. Measurements of [[delta].sup.34]S in S[O.sub.2] were made using tunable laser spectroscopy of combusted gas samples from six sulfur-bearing solids with [[delta].sup.34]S ranging from -34 to +22%0 (also measured with mass spectrometry). Standard deviation between laser and mass spectrometer measurements was 3.7 [per thousand] for sample sizes of 200 [+ or -] 75 nmol S[O.sub.2]. Although S[O.sub.2](g) decreased 9% over 15 rain upon entrainment in the analysis cell from wall uptake, observed fractionation was insignificant (+0.2 [+ or -] 0.6 [per thousand]). We also describe a strong, distinct [sup.33]S[O.sub.2] rovibrational transition in the same spectral region, which may enable simultaneous [[delta].sup.34]S and [DELTA].sup.33]S measurements.

A new method to measure iron reduction at a distance based on depositing microbial iron [Fe(III)] (hydr)oxide within nanoporous glass beads is developed. It shows that CymA and menaquinone are required for both direct and indirect mineral reduction, whereas MtrB and OmcB contribute to but are not absolutely required for iron reduction at a distance.

The effects of an environmental strain of Pseudomonas aeruginosa on Ti[O.sub.2] nanoparticle agglomerates formed in aqueous media are studied. The results have provided a novel role for bacteria in the environmental transport of engineered nanoparticles, such as growth-independent, bacterially mediated size and mass alterations of Ti[O.sub.2] nanoparticle agglomerates.

Nanoscale titanium dioxide (TiO2) is increasingly used in consumer goods and is entering waste streams, thereby exposing and potentially affecting environmental microbes. Protozoans could either take up TiO2 directly from water and sediments or acquire TiO2 during bactivory (ingestion of bacteria) of TiO2-encrusted bacteria. Here, the route of exposure of the ciliated protozoan Tetrahymena thermophila to TiO2 was varied and the growth of, and uptake and accumulation of TiO2 by, T. thermophila were measured. While TiO2 did not affect T. thermophila swimming or cellular morphology, direct TiO2 exposure in rich growth medium resulted in a lower population yield. When TiO2 exposure was by bactivory of Pseudomonas aeruginosa, the T. thermophila population yield and growth rate were lower than those that occurred during the bactivory of non-TiO2-encrusted bacteria. Regardless of the feeding mode, T. thermophila cells internalized TiO2 into their food vacuoles. Biomagnification of TiO2 was not observed; this was attributed to the observation that TiO2 appeared to be unable to cross the food vacuole membrane and enter the cytoplasm. Nevertheless, our findings imply that TiO2 could be transferred into higher trophic levels within food webs and that the food web could be affected by the decreased growth rate and yield of organisms near the base of the web. [ABSTRACT FROM AUTHOR]

Under many aqueous conditions, metal oxide nanoparticles attract other nanoparticles and grow into fractal aggregates as the result of a balance between electrostatic and Van Der Waals interactions. Although particle coagulation has been studied for over a century, the effect of light on the state of aggregation is not well understood. Since nanoparticle mobility and toxicity have been shown to be a function of aggregate size, and generally increase as size decreases, photo-induced disaggregation may have significant effects. We show that ambient light and other light sources can partially disaggregate nanoparticles from the aggregates and increase the dermal transport of nanoparticles, such that small nanoparticle clusters can readily diffuse into and through the dermal profile, likely via the interstitial spaces. The discovery of photoinduced disaggregation presents a new phenomenon that has not been previously reported or considered in coagulation theory or transdermal toxicological paradigms. Our results show that after just a few minutes of light, the hydrodynamic diameter of TiO2 aggregates is reduced from ~280 nm to ~230 nm. We exposed pigskin to the nanoparticle suspension and found 200 mg kg-1 of TiO2 for skin that was exposed to nanoparticles in the presence of natural sunlight and only 75 mg kg-1 for skin exposed to dark conditions, indicating the influence of light on NP penetration. These results suggest that photoinduced disaggregation may have important health implications. [ABSTRACT FROM AUTHOR]

Sulfur isotope measurements offer comprehensive information on the origin and history of natural materials. Tunable laser spectroscopy is a powerful analytical technique for isotope analysis that has proven itself readily adaptable for in situ terrestrial and planetary measurements. Measurements of δ34S in SO2 were made using tunable laser spectroscopy of combusted gas samples from six sulfur-bearing solids with δ34S ranging from -34 to +22‰ (also measured with mass spectrometry). Standard deviation between laser and mass spectrometer measurements was 3.7‰ for sample sizes of 200 ± 75 nmol SO2. Although SO2(g) decreased 9% over 15 min upon entrainment in the analysis cell from wall uptake, observed fractionation was insignificant (+0.2 ‰± 0.6‰). We also describe a strong, distinct 33SO2 rovibrational transition in the same spectral region, which may enable simultaneous δ34S and Δ33S measurements. [ABSTRACT FROM AUTHOR]

Ultrasmall (mean diameter, 2.7 nm) gold nanoparticles conjugated to doxorubicin (Au-Dox) are up to 20-fold more cytotoxic to B16 melanoma cells than the equivalent concentration of doxorubicin alone, and act up to six times more quickly. Ultrasmall Au-Dox enters the cell endocytic vesicles and is also seen free in the cytoplasm and nuclei. This is in distinct contrast to larger particles reported in previous studies, which are excluded from the nucleus and which show no increased toxicity over Dox alone. Cell death with Au-Dox is confirmed to be apoptotic by TUNEL staining and ultrastructural examination using transmission electron microscopy. To further explore the mechanism of action, two other cell lines were examined: HeLa cells which are highly sensitive to Dox, and HeLa cells overexpressing Bcl-2 which show impaired apoptosis and Dox resistance. Interestingly, the Dox-sensitive cells show a slightly decreased sensitivity to Au-Dox relative to Dox alone, whereas the Dox-resistant cells are not resistant to Au-Dox. These results have implications for the design of chemotherapeutic nanoparticles, suggesting that it is possible to selectively target apoptosis-resistant cancer cells while at the same time reducing cytotoxicity to normal cells.