ABSTRACT
We have conducted temperature and frequency dependent transport measurements in amorphous NbxSi1-x samples in the insulating regime. We find a temperature dependent dc conductivity consistent with variable range hopping in a Coulomb glass. The frequency dependent response in the millimeter-wave frequency range can be described by the expression sigma(omega) varies with (-iota omega)(alpha) with the exponent somewhat smaller than 1. Our ac results are not consistent with extant theories for the hopping transport.
ABSTRACT
The concept of nanotechnology is discussed, and its connection with biomedical engineering is elucidated. For the specific field of nanoscale flow and transport problems of physiological relevance, some typical examples are presented, and their interaction is discussed for some classic biomechanical problems like the flow in arteries with blood-wall coupling. Then, existing computational models are presented and classified according to the length scale of interest, with emphasis on particle-fluid problems. Final remarks address the essential unity of biomedical and engineering behaviour and the possible relevance to small-scale industrial research.
Subject(s)
Models, Biological , Rheology , Biological Transport, Active , Biomechanical Phenomena , Biomedical Engineering , Biophysical Phenomena , Biophysics , Cartilage/physiology , Cell Membrane/physiology , Endothelium, Vascular/physiology , Erythrocytes/physiology , Humans , Macromolecular Substances , Quantum Theory , ThermodynamicsABSTRACT
Nine naturally-occurring 2,2':5',2"-terthiophenes were quantitatively evaluated for their in vitro photoinduced growth inhibitory activity against three bacterial strains. All the compounds proved active towards Staphylococcus aureus. As regards Escherichia coli, the unsubstituted 2,2':5'2"-terthiophene (MIC = 0.62 microgram/ml at 4j/cm2 fluence), was found to be the only compound active. None of the compounds tested displayed activity on Pseudomonas aeruginosa at the highest concentration tested.
Subject(s)
Anti-Bacterial Agents/pharmacology , Thiophenes/pharmacology , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/radiation effects , Escherichia coli/drug effects , Light , Microbial Sensitivity Tests , Molecular Structure , Plants, Medicinal , Pseudomonas aeruginosa/drug effects , Staphylococcus aureus/drug effects , Structure-Activity Relationship , Thiophenes/chemistry , Thiophenes/radiation effectsABSTRACT
The dermatophyte Microsporum cookei Ajello was treated with nine new natural and synthetic 2,2':5',2"-terthiophenes to determine their possible antifungal activity. In the dark the thiophenes were inactive, while when photoactivated with UV-A they induced a remarkable reduction in the growth rate of the fungus. The only exception was (E)-N-(2-methylpropyl)-3-(2,2':5',2"-terthien-5-yl)-propenamide , which was not fungistatic even at the highest dose tested (24 microM). The more active compounds were 3'-methoxy-2,2':5',2"-terthiophene and 3'-methylthio-2,2':5',2"-terthiophene, whose activity seems to be related to the presence of a substituent in the 3' position of the central ring of thiophenes. Transmission electron microscopic observations demonstrated the photoactive nature of the synthetic molecules to be similar to that of alpha-terthienyl, a natural thiophene present in some Asteraceae. The dark treatment caused only the accumulation of the compound in vacuoles, without other evident alterations. After UV-A irradiation the activated thiophene causes severe modifications to the endomembrane system, probably via oxygen-dependent mechanism.
