SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Scanning electron microscope

262

Evidence of prehistoric dentistry has been limited to a few cases, the most ancient dating back to the Neolithic. Here we report a 6500-year-old human mandible from Slovenia whose left canine crown bears the traces of a filling with beeswax. The use of different analytical techniques, including synchrotron radiation computed micro-tomography (micro-CT), Accelerator Mass Spectrometry (AMS) radiocarbon dating, Infrared (IR) Spectroscopy and Scanning Electron Microscopy (SEM), has shown that the exposed area of dentine resulting from occlusal wear and the upper part of a vertical crack affecting enamel and dentin tissues were filled with beeswax shortly before or after the individual’s death. If the filling was done when the person was still alive, the intervention was likely aimed to relieve tooth sensitivity derived from either exposed dentine and/or the pain resulting from chewing on a cracked tooth: this would provide the earliest known direct evidence of therapeutic-palliative dental filling.

Concepts: Electron, Spectroscopy, Mass spectrometry, Teeth, Dental caries, Scanning electron microscope, Tooth enamel, Dentin

183

The folded intersegmental membrane is a structure that interconnects two adjacent abdominal segments; this structure is distributed in the segments of the honey bee abdomen. The morphology of the folded intersegmental membrane has already been documented. However, the ultrastructure of the intersegmental membrane and its assistive role in the telescopic movements of the honey bee abdomen are poorly understood. To explore the morphology and ultrastructure of the folded intersegmental membrane in the honey bee abdomen, frozen sections were analyzed under a scanning electron microscope. The intersegmental membrane between two adjacent terga has a Z-S configuration that greatly influences the daily physical activities of the honey bee abdomen. The dorsal intersegmental membrane is 2 times thicker than the ventral one, leading to asymmetric abdominal motion. Honey bee abdominal movements were recorded using a high-speed camera and through phase-contrast computed tomography. These movements conformed to the structural features of the folded intersegmental membrane.

Concepts: Electron, Insect, Arthropod, Honey bee, Abdomen, Scanning electron microscope, Bee, Apidae

171

Highly dispersive strontium carbonate (SrCO3) nanostructures with uniform dumbbell, ellipsoid, and rod-like morphologies were synthesized in methanol solution without any additives. These SrCO3 were characterized by X-ray diffraction, field emission scanning electron microscopy, and N2 adsorption-desorption. The results showed that the reaction temperature and the methanol/water ratio had important effects on the morphologies of SrCO3 particles. The dumbbell-like SrCO3 exhibited a Broader-Emmett-Teller surface area of 14.9 m2 g-1 and an average pore size of about 32 nm with narrow pore size distribution. The formation mechanism of the SrCO3 crystal was preliminary presented.

Concepts: Electron, Electron microscope, Strontium, X-ray, Chemical reaction, Calcium carbonate, Scanning electron microscope, Strontianite

171

Porous silicon microcavity (PSiMc) structures were used to immobilize the photosynthetic reaction center (RC) purified from the purple bacterium Rhodobacter sphaeroides R-26. Two different binding methods were compared by specular reflectance measurements. Structural characterization of PSiMc was performed by scanning electron microscopy and atomic force microscopy. The activity of the immobilized RC was checked by measuring the visible absorption spectra of the externally added electron donor, mammalian cytochrome c. PSi/RC complex was found to oxidize the cytochrome c after every saturating Xe flash, indicating the accessibility of specific surface binding sites on the immobilized RC, for the external electron donor. This new type of bio-nanomaterial is considered as an excellent model for new generation applications of silicon-based electronics and biological redox systems.

Concepts: Photosynthesis, Electron, Bacteria, Cellular respiration, Scanning tunneling microscope, Scanning electron microscope, Electron acceptor, Photosynthetic reaction centre

170

Aluminum-doped zinc oxide ceramics with yttria doping (AZO:Y) ranging from 0 to 0.2 wt.% were fabricated by pressureless sintering yttria-modified nanoparticles in air at 1,300°C. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis, a physical property measurement system, and a densimeter were employed to characterize the precursor nanoparticles and the sintered AZO ceramics. It was shown that a small amount of yttria doping can remarkably retard the growth of the as-received precursor nanoparticles, further improve the microstructure, refine the grain size, and enhance the density for the sintered ceramic. Increasing the yttria doping to 0.2 wt.%, the AZO:Y nanoparticles synthetized by a coprecipitation process have a nearly sphere-shaped morphology and a mean particle diameter of 15.1 nm. Using the same amount of yttria, a fully dense AZO ceramic (99.98% of theoretical density) with a grain size of 2.2 μm and a bulk resistivity of 4.6 × 10-3 Ω·cm can be achieved. This kind of AZO:Y ceramic has a potential to be used as a high-quality sputtering target to deposit ZnO-based transparent conductive films with better optical and electrical properties.

Concepts: Electron, X-ray, Scanning electron microscope, Ceramic engineering, Pottery, Ceramic, Sintering, Clay

168

BACKGROUND: Nanotechnology is receiving enormous funding. Very little however is known about the health dangers of this technology so far. Chronic tonsillitis is one of a number of diseases called idiopathic. Among other factors, the tonsils are exposed to suspended particles in inhaled air including nano particles. The objective of this study was to detect and evaluate metallic particles in human tonsil tissue diagnosed with chronic tonsillitis and in amniotic fluid as a comparison. METHODS: Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) was used for identification of solid particles in a total of 64 samples of routinely analyzed biopsy and cytologic material. RESULTS: Almost all samples were found to contain solid particles of various metals. The most frequent, regardless of diagnosis, were iron, chromium, nickel and aluminium. The size, determined using SEM, varied from around 500 nm to 25 µm. The majority formed aggregates of several micrometers in size but there were a significant number of smaller (sub-micrometer or nano-sized) particles present. The incidence of metallic particles was similar in child and adult tissues. The difference was in composition: the presence of several metals in adults was due to occupational exposure. CONCLUSIONS: The presence of metallic particles in pathologically altered tissues may signal an alternative causation of some diseases. The ethiopathogenic explanation of these diseases associated with the presence of nano-sized particles in the organism has emerged into a new field of pathology, nanopathology.

Concepts: Iron, Metal, Scanning electron microscope, Energy-dispersive X-ray spectroscopy, Tonsil, Tonsillectomy, Tonsillitis, Tonsillolith

168

The aim of this study was to develop an immediate-release pellet formulation with improved drug dissolution and adsorption. Carbamazepine, a poorly water-soluble drug, was adsorbed into mesoporous silica (SBA-15-CBZ) via a wetness impregnation method and then processed by extrusion/spheronization into pellets. Physicochemical characterization of the preparation was carried out by scanning electron microscopy, transmission electron microscopy, nitrogen adsorption, small-angle and wide-angle x-ray diffraction, and differential scanning calorimetry. Flowability and wettability of the drug-loaded silica powder were evaluated by bulk and tapped density and by the angle of repose and contact angle, respectively. The drug-loaded silica powder was formulated into pellets to improve flowability.

Concepts: Electron, X-ray, Adsorption, Wetting, Materials science, Scientific techniques, Transmission electron microscopy, Scanning electron microscope

168

We have investigated the influences of aluminum and gallium dopants (0 to 2.0 mol%) on zinc oxide (ZnO) thin films regarding crystallization and electrical and optical properties for application in transparent conducting oxide devices. Al- and Ga-doped ZnO thin films were deposited on glass substrates (corning 1737) by sol–gel spin-coating process. As a starting material, AlCl3.6H2O, Ga(NO3)2, and Zn(CH3COO)2.2H2O were used. A lowest sheet resistance of 3.3 x 103 [greek capital letter omega]/[white square] was obtained for the GZO thin film doped with 1.5 mol% of Ga after post-annealing at 650 [degree sign]C for 60 min in air. All the films showed more than 85 % transparency in the visible region. We have studied the structural and microstructural properties as a function of Al and Ga concentrations through X-ray diffraction and scanning electron microscopy analysis. In addition, the optical bandgap and photoluminescence were estimated.

Concepts: Electron, X-ray, Optical fiber, Aluminium, Zinc, X-ray crystallography, Scanning electron microscope, Zinc oxide

167

Biological materials with hierarchically laminated structures usually exhibit a good synergy between strength and fracture toughness. Here, we show that a bio-inspired (polyelectrolyte (PE)/TiO2)4 nanolayered composite with a thickness ratio of TiO2 and amorphous PE layers of about 1.1 has been prepared successfully on Si substrates by layer-by-layer self-assembly and chemical bath deposition methods. Microstructures of the nanolayered composite were investigated by scanning electron microscopy, secondary ion mass spectroscopy, and high-resolution transmission microscopy. Mechanical performance of the composite was characterized by instrumented indentation. The composite consisting of 17.9-nm-thick nanocrystalline TiO2 and 16.4-nm-thick amorphous PE layers has a strength of about 245 MPa, which is close to that of shells, while the fracture toughness of the composite, KIC = 1.62 +/- 0.30 MPa . m1/2, is evidently higher than that of the bulk TiO2. A possible strategy to build the composite at nanoscale for high mechanical performance was addressed.

Concepts: Electron, Electron microscope, Fracture mechanics, Materials science, Transmission electron microscopy, Scanning electron microscope, Secondary ion mass spectrometry, Fracture toughness

167

Although amorphous silica is used in food products, cosmetics and paints and as vector for drug delivery, data on its potential health hazard are limited. The aim of this study was to investigate the cytotoxic and genotoxic potential of silica particles of different sizes (250 and 500nm) and structures (dense and mesoporous). Dense silica (DS) spheres were prepared by sol-gel synthesis, mesoporous silica particles (MCM-41) were prepared using hexadecyltrimethyl ammonium bromide as a structure-directing agent and tetraethylorthosilicate as silica source. Particles were accurately characterised by dynamic light scattering, nitrogen adsorption, X-ray diffraction and field emission scanning electron microscopy. Murine macrophages (RAW264.7) and human epithelial lung (A549) cell lines were selected for investigation. Genotoxicity was evaluated by Comet assay and micronucleus test. Cytotoxicity was tested by the trypan blue method. Cells were treated with 0, 5, 10, 20, 40 and 80 µg/cm(2) of different silica powders for 4 and 24 h. The intracellular localisation of silica was investigated by transmission electron microscopy. Amorphous particles penetrated into the cells, being compartmentalised within endocytic vacuoles. DS and MCM-41 particles induced cytotoxic and genotoxic effects in A549 and RAW264.7 although to different extent in the two cell lines. A549 were resistant in terms of cell viability, but showed a generalised induction of DNA strand breaks. RAW264.7 were susceptible to amorphous silica exposure, exhibiting both cytotoxic and genotoxic responses as DNA strand breaks and chromosomal alterations. The cytotoxic response of RAW264.7 was particularly relevant after MCM-41 exposure. The genotoxicity of amorphous silica highlights the need for a proper assessment of its potential hazard for human health.

Concepts: DNA, Electron, Cell, Human, Chromosome, Sol-gel, Scanning electron microscope, Silicon dioxide