RESUMO
Few-layer rippled hexagonal boron nitride (h-BN) membranes were processed with hydrogen plasma, which exhibit distinct and pronounced changes in its electronic properties after the plasma treatment. The bandgaps of the h-BN membrane reduced from ~5.6 eV at 0 s to ~4.25 eV at 250 s, which is a signature of transition from the insulating to the semiconductive regime. It typically required 250 s of plasma treatment to reach the saturation. It illustrates that two-dimensional material with engineered electronic properties can be created by attaching other atoms or molecules.
RESUMO
Clostridium perfringens has been implicated as a causative agent of foodborne poisoning, infectious diarrhea (not associated with foods), gas gangrene, and several veterinary diseases. Fecal carriage of enterotoxigenic strains of this bacterium appears to be important in the development of infectious diarrhea and as a source of C. perfringens contamination of foods. In this work, carriage of this bacterium in feces of a Mexican population was analyzed. C. perfringens was found in 126 of the 200 fecal samples obtained from healthy individuals from northern Mexico. The samples had an average of 7.4 x 10(3) spores per gram, with the elderly population showing the highest levels. Dot blot analyses using a dig-labeled probe specific for the enterotoxin gene showed that 7% of the samples had isolates with toxigenic potential.