Hasil untuk "physics.ed-ph"

Jin-Zhi Du, Xiao-Jiao Du, Chengqiong Mao et al.

T. A. Krulwich, G. Sachs, E. Padan

Y. Al-Degs, M. El‐Barghouthi, A. El‐Sheikh et al.

A. Airapetian, V. Dodonov, L. Micu et al.

S. Ohkuma, B. Poole

J. A. Thomas, R. Buchsbaum, A. Zimniak et al.

J. Koufman

I. Tannock, D. Rotin

D. Houben, Laurent Evrard, P. Sonnet

Kateryna Zhalnina, Raquel Dias, Patrícia Dörr de Quadros et al.

G. Aad, E. Abat, B. Abbott et al.

Kun Wang, Jun Yin, D. Shen et al.

W. Guo, Chun-hua Lu, R. Orbach et al.

Binbin Liu, P. Mørkved, Å. Frostegård et al.

The N(2)O : N(2) product ratio of denitrification is negatively correlated with soil pH, but the mechanisms involved are not clear. We compared soils from field experiments where the pH had been maintained at different levels (pH 4.0-8.0) by liming (> or = 20 years), and quantified functional gene pools (nirS, nirK and nosZ), their transcription and gas kinetics (NO, N(2)O and N(2)) of denitrification as induced by anoxic incubation with and without a carbon substrate (glutamate). Denitrification in unamended soil appeared to be based largely on the activation of a pre-existing denitrification proteome, because constant rates of N(2) and N(2)O production were observed, and the transcription of functional genes was below the detection level. In contrast, glutamate-amended soils showed sharp peaks in the transcripts of nirS and nosZ, increasing the rates of denitrification and pH-dependent transient accumulation of N(2)O. The results indicate that the high N(2)O : N(2) product ratio at low pH is a post-transcriptional phenomenon, because the transcription rate of nosZ relative to that of nirS was higher at pH 6.1 than at pH 8.0. The most plausible explanation is that the translation/assembly of N(2)O reductase is more sensitive to low pH than that of the other reductases involved in denitrification.

Špela Zupančič, Z. Lavrič, J. Kristl

Shiyi Zhang, Andrew M Bellinger, D. Glettig et al.

Devices resident in the stomach -- which are used for a variety of clinical applications including nutritional modulation for bariatrics, ingestible electronics for diagnosis and monitoring, and gastric retentive dosage forms for prolonged drug delivery -- typically incorporate elastic polymers to compress the devices during delivery through the esophagus and other narrow orifices in the digestive system. However, in the event of accidental device fracture or migration, the non-degradable nature of these materials risks intestinal obstruction. Here, we show that an elastic, pH-responsive supramolecular gel remains stable and elastic in the acidic environment of the stomach but can be dissolved in the neutral-pH environment of the small and large intestines. In a large animal model, prototype devices with these materials as the key component demonstrated prolonged gastric retention and safe passage. These enteric elastomers should increase the safety profile for a wide range of gastric retentive devices.

D. Johnson, T. Kanao, S. Hedrich et al.

Many different species of acidophilic prokaryotes, widely distributed within the domains Bacteria and Archaea, can catalyze the dissimilatory oxidation of ferrous iron or reduction of ferric iron, or can do both. Microbially mediated cycling of iron in extremely acidic environments (pH < 3) is strongly influenced by the enhanced chemical stability of ferrous iron and far greater solubility of ferric iron under such conditions. Cycling of iron has been demonstrated in vitro using both pure and mixed cultures of acidophiles, and there is considerable evidence that active cycling of iron occurs in acid mine drainage streams, pit lakes, and iron-rich acidic rivers, such as the Rio Tinto. Measurements of specific rates of iron oxidation and reduction by acidophilic microorganisms show that different species vary in their capacities for iron oxido-reduction, and that this is influenced by the electron donor provided and growth conditions used. These measurements, and comparison with corresponding data for oxidation of reduced sulfur compounds, also help explain why ferrous iron is usually used preferentially as an electron donor by acidophiles that can oxidize both iron and sulfur, even though the energy yield from oxidizing iron is much smaller than that available from sulfur oxidation. Iron-oxidizing acidophiles have been used in biomining (a technology that harness their abilities to accelerate the oxidative dissolution of sulfidic minerals and thereby facilitate the extraction of precious and base metals) for several decades. More recently they have also been used to simultaneously remediate iron-contaminated surface and ground waters and produce a useful mineral by-product (schwertmannite). Bioprocessing of oxidized mineral ores using acidophiles that catalyze the reductive dissolution of ferric iron minerals such as goethite has also recently been demonstrated, and new biomining technologies based on this approach are being developed.

Sayaka Ono, Ryutro Imai, Yukiko Ida et al.

J. Ban, Mijung Lee, W. Im et al.

T. Kennedy, J. L. MacLean, Juewen Liu