Background and objectives: The plants belonging to the genus Heliotropium L. (Boraginaceae) are the main sources of toxic pyrrolizidine alkaloids (PAs). In the present study, we have investigated the PAs of the aerial parts of Heliotropium transoxanum Bunge, a perennial species native to Iran. Methods: Silica gel column chromatography and silica gel PTLC were applied ...

We have synthesized inorganic micron-sized filaments, whose microstucture consists of silica-coated nanometer-sized carbonate crystals, arranged with strong orientational order. They exhibit noncrystallographic, curved, helical morphologies, reminiscent of biological forms. The filaments are similar to supposed cyanobacterial microfossils from the Precambrian Warrawoona chert formation in Weste...

A simple process for forming sub-micron gaps between horizontal and vertical electrodes in a three-dimensional micro-electrode system without the need for high-resolution lithography is described. The process is based on the enhancement of ion milling rates in metals at oblique ion incidence, which allows the preferential erosion of metal at a mesa edge. Self-aligned electrode structures are fo...

G roundwaters in areas such as Texas, New Mexico, Arizona, California, parts of southern Europe, the Pacific Rim, and Latin America contain high silica concentrations (50 to 100 ppm, as colloidal silica [SiO 2 ]). These levels arise from dissolution of various silicate-containing minerals into the groundwater. Silica precipitation and deposition occur mostly in evaporative cooling systems, wher...

The expression of 10 genes implicated in regulation of the inflammatory processes in the lung was studied after exposure of alveolar macrophages (AMs) to silica in vitro or in vivo. Exposure of AMs to silica in vitro up-regulated the messenger RNA (mRNA) levels of three genes [interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), and macrophage inflammatory protein-2 (MIP-2)] withou...

Polyamide 6/silica nanocomposites were synthesized by in situ ring-opening anionic polymerization of ε-caprolactam in the presence of sodium caprolactamate as a catalyst and caprolactam-functionalized silica as an initiator. The initiator precursor, isocyanate-functionalized silica, was prepared by directly reacting commercial silica with excess toluene 2,4-diisocyanate. This polymerization was...

metal nanoshells consists of a dielectric core surrounded by a thin noble metal shell, possess unique optical properties that render nanoshells attractive for use in different technologies. this paper reports a facile method for growth of small gold nanoparticles on the functionalized surface of larger silica nanoparticles. mono-dispersed silica particles and gold nanoparticles were prepared by...

This study examined the effect that silica content in diatom cells has on the behavior of protists. The diatoms Thalassiosira weissflogii and T. pseudonanawere cultured in high or low light conditions to achieve low and high silica contents, respectively. These cells were then fed to a heterotrophic dinoflagellate Noctiluca scintillans and a ciliate Euplotes sp. in single and mixed diet experim...

Occupational exposure to mineral dusts, such as silica, has been associated with progressive pulmonary inflammation, lung cancer, and fibrosis. However, the mechanisms involved in this process are poorly understood. Because p53 is a key transcription factor regulating many important apoptosis-related genes, we hypothesized that p53 may play a key role in silica-induced apoptosis and that abnorm...