The paper deals with the presence of iron-based granules in body parts of bumblebees. Two groups of bumblebees were collected from their natural habitat, industrial landscape, and from a breeding ...station. Detection of the magnetic particles was performed by a vibratory magnetometer and their morphology and elemental composition was analysed by scanning electron microscopy with EDX microanalysis. By means of the EDX spectra, wild bumblebees were found to have many magnetic and non-magnetic particles on their body, containing Fe, O, Al, Si, Bi, Mg, K, and Ni, likely having origin in the industrial pollution of the environment. In the case of bred bumblebees the presence of iron-rich granules, which occurred more abundantly in subsurface tissues on the head and wings, was observed. Phase analysis based on X-ray diffraction shows that iron-based granules contain magnetite and wuestite and Mössbauer spectroscopy admits a superparamagnetic form of these minerals. Magnetoreception, i.e. the sensory function of these granules, is discussed within the paper.
The paper addresses laboratory preparation, characterization and in vitro evaluation of antibacterial activity of graphite/TiO sub(2) nanocomposites. Composites graphite/TiO sub(2) with various ratio ...of TiO sub(2) nanoparticles (30 wt.%, and 50 wt.%) to graphite were prepared using a thermal hydrolysis of titanylsulfate in the presence of graphite particles, and subsequently dried at 80 degreesC. X-ray powder diffraction, transmission electron microscopy and Raman microspectroscopy served as phase-analytical methods distinguishing anatase and rutile phases in the prepared composites. Scanning and transmission electron microscopy techniques were used for characterization of morphology of the prepared samples. A developed modification of the standard microdilution test was used for in vitro evaluation of daylight induced antibacterial activity, using four common human pathogenic bacterial strains (Staphylococcus aureus, Escherichia coli, Enterococcus faecalis and Pseudomonas aeruginosa). Antibacterial activity of the graphite/TiO sub(2) nanocomposites could be based mainly on photocatalytic reaction with subsequent potential interaction of reactive oxygen species with bacterial cells. During the antibacterial activity experiments, the graphite/TiO sub(2) nanocomposites exhibited antibacterial activity, where differences in the onset of activity and activity against bacterial strains were observed. The highest antibacterial activity evaluated as minimum inhibitory concentration was observed against P. aeruginosa after 180 min of irradiation.
The paper addresses laboratory preparation and antibacterial activity testing of kaolinite/nanoTiO sub(2) composite in respect of the daylight irradiation time. Kaolinite/nanoTiO sub(2) composites ...with 20 and 40 wt% of TiO sub(2) were laboratory prepared, dried at 105 degreesC and calcined at 600 degreesC. The calcination caused transformation of kaolinite to metakaolinite and origination of the metakaolinite/nanoTiO sub(2) composite. X-ray powder diffraction, Raman and FTIR spectroscopic methods revealed titanium dioxide only in the form of anatase in all evaluated samples (non-calcined and calcined) and also transformation of kaolinite to metakaolinite after the calcination treatment. Scanning electron microscopy was used as a method for characterization of morphology and elemental composition of the studied samples. A standard microdilution test was used to determine the antibacterial activity using four human pathogenic bacterial strains (Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa). A lamp with a wide spectrum bulb simulating daylight was used for induction of photocatalysis. The antibacterial assays found all the KATI samples to have antibacterial potency with different onset of the activity when calcined samples exhibited antibacterial activity earlier than the non-calcined. Significant difference in antibacterial activity of KATI samples for different bacterial strains was not observed.
PDF