Nanocrystalline particles of MgO were synthesized using microwave radiation in an ethylene glycol solution. The antibacterial activities of the MgO nanoparticles were tested by treating Escherichia ...coli (Gram negative) and Staphylococcus aureus (Gram positive) cultures with 1 mg mL–1 of the nanoparticles. We have examined the importance of the size effect, pH, and the form of the active MgO species as a bactericidal agent. A clear size dependence of the nanoparticles is observed where the amount of eradicated bacteria was strongly dependent on the particle size.
Nanocrystalline particles of MgO show positive antibacterial properties for E. coli (Gram negative) and Staph. aureus (Gram positive) cultures. A clear size dependence of the nanoparticles is observed for the bactericidal studies, where the amount of eradicated bacteria is strongly dependent on the particle size. Small, electron‐dense black dots have been observed in the cytoplasm of the MgO‐nanoparticle‐treated E. coli bacteria (see Figure).
Dispersion of low‐temperature thermochronologic data from nine samples collected on a deformed paleosurface preserved on the Cuevas range (Central Andes) can be exploited to unravel complex thermal ...histories. The nine samples yielded data that have both intersample and intrasample dispersions; the data set includes apatite fission‐track ages (180–110 Ma), mean track lengths (11–13 μm), apatite helium (10–250 Ma), and zircon helium ages (180–348 Ma). We ran inverse thermal history models for each sample that reveal spatial variations of the Miocene reheating along the paleosurface. Next, we ran a multiple‐sample joint model to infer a common form for thermal history for all samples. Our results suggest that initial exhumation during the Famatinian orogeny was followed by a residence between ~2.5 and 7.0 km depth during the Paleozoic and the Triassic. The onset of Mesozoic rifting was responsible for an increase of the geothermal gradient and extensive horst exhumation, which brought the basement of the Cuevas range close to the surface (~1–2 km) in the Late Jurassic. Between the Late Cretaceous and the Paleocene, the combination of low relief, a humid climate, and low erosion rates (0.006–0.030 km/Ma) facilitated the development of the Cuevas paleosurface. During the Miocene, this paleosurface experienced differential reheating with a high geothermal gradient (>25 °C/km) due to the sedimentary cover and local magmatic heat sources. During the Andean orogeny, in the Pliocene, the Cuevas paleosurface was deformed, exhumed, and uplifted.
Key Points
Multiple‐sample thermal history model performed with samples from a continuous paleosurface
Intersample and intrasample thermochronologic dispersions can be exploited to refine the tectonic evolution of the Campo‐Arenal basin
Spatiotemporal variations of geothermal gradient can explain basement thermal histories
We demonstrate a novel array-based diagnostic platform comprising lipid/polydiacetylene (PDA) vesicles embedded within a transparent silica-gel matrix. The diagnostic scheme is based upon the unique ...chromatic properties of PDA, which undergoes blue-red transformations induced by interactions with amphiphilic or membrane-active analytes. We show that constructing a gel matrix array hosting PDA vesicles with different lipid compositions and applying to blood plasma obtained from healthy individuals and from patients suffering from disease, respectively, allow distinguishing among the disease conditions through application of a simple machine-learning algorithm, using the colorimetric response of the lipid/PDA/gel matrix as the input. Importantly, the new colorimetric diagnostic approach does not require a priori knowledge on the exact metabolite compositions of the blood plasma, since the concept relies only on identifying statistically significant changes in overall disease-induced chromatic response. The chromatic lipid/PDA/gel array-based "fingerprinting" concept is generic, easy to apply, and could be implemented for varied diagnostic and screening applications.
The Itajaí Basin is a fault-bounded late- to post-orogenic basin deposited adjacent to the Dom Feliciano Belt in the state of Santa Catarina, Brazil. The basin is composed of alluvial-deltaic and ...platformal successions followed by a turbiditic complex and fan-delta deposits. U-Pb zircon dating of a tuff and five sandstone samples indicates a maximum depositional age of 563
±
3
Ma for the intermediate and upper sections of the Itajaí Basin, and zircon dating of a rhyolite stock indicates a minimum depositional age of 549
±
4
Ma. These dates are compatible with the previous assignment of an Ediacaran age to the sediments based on the discovery of Ediacara-type fossils such as
Parvancorina,
Charniodiscus,
Cyclomedusa, and
Aspidella. The U-Pb detrital zircon ages show a change in the sedimentary input from the base to the top. At the base, zircon grains from the Transamazonian and Brasiliano/Pan-African orogenic cycles occur as major sources with some Archean contribution. The upper section is dominated by Brasiliano/Pan-African zircon grains, most of which range in age from 824 to 770
Ma and 656 to 563
Ma. Pb and Sm-Nd whole rock isotope data suggest that the main source area for the basin infill was a reworked crust such as the Dom Feliciano Belt. We also present the regional correlation of the Itajaí Basin with the basins formed during the late stages of the SW Gondwana.
We present the construction of microscopic vesicular particles comprising phospholipids and polydiacetylene (PDA), a polymer with unique color and fluorescence properties. We show that the ...vesicle‐embedded PDA domains function as chromatic reporters of membrane events, undergoing dramatic colorimetric and fluorescence transformations induced by interactions with membrane‐active species. In particular, the micrometer sizes of the giant vesicles facilitate their utilization for visual inspection of membrane events by conventional microscopy techniques. The morphology, size, and chromatic properties of the vesicular aggregates depend upon the type of phospholipids and the molecular ratio between the phospholipids and diacetylene, indicating that the lipids and polymer form interdependent domains within the vesicles. The giant chromatic aggregates have been employed for detection and microscopic visualization of varied membrane processes, including lipid interactions of lipophilic drugs, binding of antimicrobial peptides, and membrane attachment by virus particles.
Giant lipid/polydiacetylene vesicles exhibiting unique chromatic properties are prepared and characterized. The polymerized vesicles undergo visible color transformations (from blue to red) and fluorescence emission, both induced by binding of biological molecules and larger particles, such as viruses.
Here, we report the development of a homemade experimental setup to perform under vacuum an in situ study of the physical properties of bundles of single-walled carbon nanotubes intercalated with ...rubidium ions using electrical conductivity, X-ray absorption and Raman measurements. This set-up was successfully used at the SAMBA beamline at the Soleil synchrotron. The electrical resistance displays an important drop with the stoichiometry (intercalation time). The Raman radial breathing modes and the G-band of the nanotubes clearly indicate an important electron transfer. The G-band behaviour features a transition from semiconducting to metallic nanotubes, confirmed by the electrical resistance measurements as a function of the temperature after rubidium intercalation. This set-up can be used for the study of any type of extremely air sensitive materials.
Interactions between peptides and lipid membranes play major roles in numerous physiological processes, such as signaling, cytolysis, formation of ion channels, and cellular recognition. We describe ...a new colorimetric technique for studying peptide-membrane interactions. The new assay is based on supramolecular assemblies composed of phospholipids embedded in a matrix of polydiacetylene (PDA) molecules. The phospholipid/PDA vesicle solutions undergo visible color changes upon binding of membrane peptides. Experiments utilizing various analytical techniques confirm that the blue-to-red color transitions of the phospholipid/PDA vesicles are directly related to adoption of helical conformations by the peptides and their association with the lipids. Spectroscopic data indicate that the colorimetric transitions are correlated with important molecular parameters, such as the degree of penetration of the peptides into lipid bilayers, and the mechanisms of peptide-lipid binding. The results suggest that the new colorimetric assay could be utilized for studying interactions and organization of membrane peptides.
PDF
