Effect of particle size on in vitro cytotoxicity of titania and alumina nanoparticles

Aluminium oxide (Al₂O₃) and titanium dioxide (TiO₂) nanoparticles (NPs) have been widely used in nanotechnology-based products. Recently, researchers and the public have raised concerns about the adverse effects of these NPs in biological systems, particularly in humans. The aim of this study was to investigate the possible adverse effects of these two common metal oxide NPs on human lung epithelium cells (A549) and to investigate NP size-dependent effects on these cells, considering both the primary and hydrodynamic particle size. NPs were found to inhibit cell viability and proliferation at the highest concentration level (10?mg/mL) included in this study, as measured by a clonogenic assay. Moreover, cell viability, proliferation and metabolism were impaired to a greater extent by the smaller NPs (5?nm TiO₂ and 10?nm Al₂O₃) relative to the larger particles (200?nm TiO₂ and 50?nm Al₂O₃) included in this study, as measured by cell proliferation and metabolism. Notably, the observed cytotoxic effects correlated to the primary size, rather than the hydrodynamic size. Similarly, NP cytotoxicity was found to be correlated with the NP surface area. These findings highlight the importance of including primary size and surface area information in NP characterisation in cytotoxicity studies.     

Which tool to distinguish transient alumina from alpha alumina in thermally grown alumina scales?

Abstract

Alumina scales constitute excellent protective barriers when they form on alumina-forming steels. If they keep tightly adherent to the underlying substrate, they isolate it from the surrounding aggressive atmosphere at high temperature. The protectiveness of the alumina scale is highly dependant upon its growth mechanism. The nucleation and transformation of transient alumina (mainly γ-Al₂O₃ and θ-Al₂O₃) is known to play an important role on alumina scale formation. It is therefore fundamental to characterise these transient alumina especially during the early stages of the oxidation process. The morphology of the transient alumina was observed by scanning electron microscopy (SEM), their crystallographic phases determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). X-ray photoelectron spectrometry (XPS) analyses were performed on reference samples and then compared to the alloys oxidised 5 and 30 minutes at 850, 900 and 950°C.     

How expensive is Big Science? Consequences of using simple publication counts in performance assessment of large scientific facilities

Although the nuclear era and the Cold War superpower competition have long since passed, governments are still investing in Big Science, although these large facilities are nowadays mostly geared towards areas of use closer to utility. Investments in Big Science are also motivated not only by promises of scientific breakthroughs but also by expectations (and demands) of measurable impact, and with an emerging global market of competing user-oriented Big Science facilities, quantitative measures of productivity and quality have become mainstream. Among these are rather simple and one-sided publication counts. This article uses publication counts and figures of expenditure for three cases that are disparate but all represent the state-of-the-art of Big Science of their times, discussing at depth the problems of using simple publication counts as a measure of performance in science. Showing, quite trivially, that Big Science is very expensive, the article also shows the absurd consequences of consistently using simple publication counts to display productivity and quality of Big Science, and concludes that such measures should be deemed irrelevant for analyses on the level of organizations in science and replaced by qualitative assessment of the content of the science produced.     

A new carbon structure in annealed film coatings of the carbon–lead system

Carbon–lead solid solutions coexisting with amorphous carbon have been obtained for the first time in a film coating deposited by ion-plasma sputtering. During subsequent vacuum annealing of carbon–lead films containing more than 68.5 at % Pb, this element almost completely evaporates to leave an amorphous carbon coating on a substrate. During annealing at 1100°C, this amorphous carbon crystallizes into a new hexagonal lattice with unit cell parameters a = 0.7603 nm and c = 0.8168 nm. Characteristic X-ray diffraction data for the identification of this phase are determined.

     

Violation of Schmid's law and tension–compression asymmetry in L12 alloys: role of ordered structure

Abstract

Hypostoichiometric Ni₃Al(B) undergoes a structural transformation from its initial L1₂ structure to DO₂₂ structure during cold rolling. It has been found that this DO₂₂ structure reverts back to L1₂ structureduring annealing. The transformation to DO₂₂ structure as well as back to L1₂ at higher temperature is very much dependent on the degree of cold reduction. Based on thesefindings, the possible reason for abnormal behaviour of these L1₂ordered alloys, i.e. violation of Schmid's law and orientation dependence of flow stress is hypothesised.     

Facile fabrication of organobentonite–carboxymethyl chitosan hybrid film that absorbs organophosphate insecticides

Organophosphate (OP)-insecticide-absorbing hybrid film containing 10% (w/w) organobentonite and carboxymethyl chitosan (CMCh) was fabricated and tested. Bentonite clay was modified to organobentonite by two steps modification with (1) NaCl and (2) plant alkaloid monovalent cation berberine. CMCh was synthesized from commercial shrimp chitosan. Afterwards, organobentonite was immobilized into CMCh matrix via in situ polymerization of CMCh to cast a hybrid film with 0.5 mm thickness. Scanning electron microscopy images of organobentonite powder and the film revealed the porous material and layer-upon-layer structure, respectively, which is supposed to enhance the water permeability of the film. Fourier transform infrared spectrometry analysis revealed similarly chemical characteristics of the CMCh component in the film and synthesized CMCh polymer powder. The film was then investigated to remove four OP insecticides including profenofos, chlorpyrifos, methyl parathion and dimethoate of 5 ppm concentration in spiked water samples via batch filtration. High-pressure liquid chromatography analysis showed that the removal rates for profenofos, chlorpyrifos, methyl parathion and dimethoate after seven batches were 42, 39, 24 and 20%, respectively. Hence, absorptivity of this film for tested OP insecticides was demonstrated. Furthermore, the combination of organobentonite and natural chitosan is promising for novel absorptive film material generation with regard to environmental clean-up study.     

Role of particle size of alumina on the formation of aluminium titanate as well as on sintering and microstructure development in sol–gel alumina–aluminium titanate composites

With a view to develop low temperature fine grained alumina–aluminium titanate composite, influence of alumina particle size on the temperature of formation of the aluminium titanate, sintering behaviour and microstructure development of alumina–aluminium titanate composite prepared through a sol–gel core shell approach is reported. The alumina matrix composite containing 20 wt% aluminium titanate has been prepared from alumina powders having different average particle size in the range 300–600 nm. The alumina particle size appears to have no significant influence on the formation temperature of in situ formed aluminium titanate. However, the microstructural analysis of the dense ceramic showed that the average grain size of the alumina–aluminium titanate composite increases with increase in the alumina particle size. XRD analysis indicated the absence of rutile titania in the sintered composite ensuring complete formation of aluminium titanate. Smaller starting alumina particle size led to finer grain size composites. The present study therefore shows that although the starting particle size of alumina has no significant role on the lowering of formation temperature of aluminium titanate, it does influence the microstructure of the composite.     

Properties of anodic oxides grown on a hafnium–tantalum–titanium thin film library

A ternary thin film combinatorial materials library of the valve metal system Hf–Ta–Ti obtained by co-sputtering was studied. The microstructural and crystallographic analysis of the obtained compositions revealed a crystalline and textured surface, with the exception of compositions with Ta concentration above 48 at.% which are amorphous and show a flat surface. Electrochemical anodization of the composition spread thin films was used for analysing the growth of the mixed surface oxides. Oxide formation factors, obtained from the potentiodynamic anodization curves, as well as the dielectric constants and electrical resistances, obtained from electrochemical impedance spectroscopy, were mapped along two dimensions of the library using a scanning droplet cell microscope. The semiconducting properties of the anodic oxides were mapped using Mott–Schottky analysis. The degree of oxide mixing was analysed qualitatively using x-ray photoelectron spectroscopy depth profiling. A quantitative analysis of the surface oxides was performed and correlated to the as-deposited metal thin film compositions. In the concurrent transport of the three metal cations during oxide growth a clear speed order of Ti > Hf > Ta was proven.     

How rare are large,multiple-fatality work-related incidents?

Despite their salience, the prevalence of incidents that result in many work-related deaths is not well-documented. This study estimated probabilities of observing large scale work-related fatal incidents using 1995–2010 records from the Census of Fatal Occupational Injuries. A range of model estimates suggest approximately a one-in-four annual chance of observing an incident resulting in 20 or more work-related fatalities. The most likely contributors are aircraft incidents, and fires and explosions. The probability that a large scale incident occurs has declined in recent years due to a general decline in the number of fatal incidents, and due to a compositional shift away from those types of incidents more likely to result in large scale outcomes.     

What do analyses of city size distributions have in common?

Scientometrics - In this article, I conduct a textual and contextual meta-analysis of the empirical literature on Zipf's law for cities. Combining citation network analysis and...     

Mobilities and dislocation energies of planar faults in an ordered A3B (D019) structure

Present work describes the stability of possible planar faults of the A ₃B (D0 ₁₉) phase with an axial ratio less than the ideal. Mobilities and dislocation energies of various planar faults viz. antiphase boundaries (APBs), superlattice intrinsic stacking faults (SISFs) and complex stacking faults (CSFs) have been computed using complex fourth-order tensor transformations and hard sphere model. Displacements normal to the slip planes for various slip systems (vertical shift) have been used to calculate mobility of dislocations. The energy of the planar faults in Ti ₃Al intermetallic is calculated using some simplifying assumptions. Based on the mobility and energy, stability of planar faults has been explained. These results are compared with single crystal ordered Ti ₃Al alloy having D0 ₁₉ structure.     

The effect of size of the SiC inclusions in the AlN–SiC composite structure on its electrophysical properties

AlN–SiC–Y₃Al₅O₁₂ composite materials with a high absorption of microwave frequency (27–65 dB/cm) produced by pressureless sintering of mixtures consisting of AlN(2H), Y₂O₃, and SiC (6H) in 46, 4, 50 wt %, respectively, have been studied. The SiC components of the mixtures were used in sizes of 1, 5, and 50 μm. It has been shown that the resistivity of the developed materials depends essentially on the materials structures: sizes of SiC inclusions, distances between them, and state of the interfaces. It has been found that the increase of the SiC inclusions sizes in the material structure from 3 to 7 μm results in the decrease of the resistivity from 10⁴ to 90 Ω·m, and at the decrease of the SiC inclusions sizes from 3 to 0.5 μm there forms a SiC uninterrupted skeleton, which also decreases the resistivity to 210 Ω·m. Thus, composite materials that contain 50 wt % SiC (inclusions sizes of 3 μm) are the most efficient in producing absorbers of microwave radiation. Interlayers of yttrium aluminum garnet, which are located at the SiC grains boundaries, prevent the forming of AlN(2H)–SiC(6H) solid solutions and thus, make it possible to keep high dielectric characteristics of a composite material based on aluminum nitride and afford a high absorption of a microwave radiation.     

Strength improvement in beta″ alumina by incorporation of zirconia

Beta alumina ceramic electrolytes for use in Na/S batteries are inherently weaker than most engineering ceramics due to the presence of weakly-bonded conduction planes in the crystal structure and to difficulties in controlling grain growth during firing. Substantial improvement in microstructural control is obtained by incorporation of monoclinic zirconia (m-ZrO₂) or partially stabilized zirconia (PSZ) resulting in increases in strength and fracture toughness to around 350 MPa and 4 MPam^1/2, respectively. PSZ may adversely influence the electrical resistivity of the ceramic owing to the presence of impurities. With most zirconia powders a high level of retention of tetragonal zirconia (t-ZrO₂) is obtained at levels of addition up to 15% by weight ZrO₂. At these levels ZrO₂/-Al₂O₃ ceramics show low resistivity and stable resistance in Na/S cells.     

Determination of diffusivity of sodium in liquid tin using Na-ß″ alumina

Diffusivity of sodium in molten tin was determined using an electrochemical cell of the type Na/Na-β″-Al₂O₃/(Na)Sn where Na-β″-Al₂O₃, which is a sodium-ion conductor, was the solid electrolyte. Using the above cell in which a small amount of sodium dissolved in tin was transported through β″-Al₂O₃ upon application of an external voltage, and using a known solution to Fick's second law for appropriate boundary conditions, the diffusivity was determined to be $$D{\text{ = 4}}{\text{.4 }}\left( {\begin{array}{*{20}c} {{\text{ + 1}}{\text{.0}}} \\ {{\text{ - 0}}{\text{.5}}} \\ \end{array} } \right){\text{ x 10}}^{{\text{ - 4}}} {\text{ exp }}\left( {{\text{ - }}\frac{Q}{{RT}}} \right){\text{ cm}}^{\text{2}} {\text{ sec}}^{{\text{ - 1}}} $$ withQ = 16320 J mol^?1 over a range of temperatures from 240 to 440° C. From the solution to Fick's second law, it was shown that first term approximations, which have often been used in the past, lead to an estimate of diffusivity which is about a factor of 2 too high indicating that more terms should be considered. The diffusivity was also determined using a transient technique in which the decay in voltage upon removal of externally applied voltage was recorded as a function of time. The diffusivity so determined, in which it was assumed that the only polarization was the concentration polarization, was higher than the previous method. The difference between the two diffusivities became smaller with increasing temperature. These experiments thus suggested that interfacial or activation polarization must also be present.     

ZnO@CdS core–shell thin film: fabrication and enhancement of exciton life time by CdS nanoparticle

In the present study photoluminescence behavior of ZnO and ZnO@CdS core–shell nanorods film has been reported. ZnO nanorods were grown on the glass coated indium tin oxide (ITO) surface by seeding ZnO particle followed with nanorods growth. These nanorods were coated with CdS by chemical bath deposition techniques to have ZnO@CdS thin film and further annealed at 200 °C for their adherence to the ITO surface. The coating was characterized for surface morphology using SEM and optical behavior using UV–visible spectrophotometer. Energy dispersive X-ray (EDX) was used for compositional analysis and time resolve photoluminescence decay for excitons life time measurement. The absorption spectrum reveals that the absorption edge of ZnO@CdS core–shell heterostructure shifted to 480 nm in the visible region whereas ZnO nanorods have absorption maxima at 360 nm. The excitons lifetime of ZnO@CdS was found to be increased with the thickness of the CdS layer on ZnO nanorod. These ZnO@CdS core–shell nanostructures will be of great use in the field of photovoltaic cell and photocatalysis in a UV–visible region.     

How does firm size affect technology licensing? Empirical evidence from China

Technology licensing is viewed as the key factor for activating the sleeping patents. This study re-examines the relationship between the firm size and its technology licensing activity. The empirical results show that there is a U-shaped relationship between the firm size and technology licensing. However, this U-shaped relationship appears only in the markets with high competition, which confirms a moderate role of the technology competition in the relationship between the firm size and technology licensing. Chinese firms lag behind developed countries in terms of the licensing strategies. e.g., Chinese firms have fewer patents that are cross licensed. China’s export-oriented firms show relatively more positive licensing propensity, where large, small and medium sized firms do not show essentially different willingness to license out their patents compared with non export-oriented firms. China’s state owned firms are less likely to license out their patents compared with that of private firms. Policy implications are presented at the end of this study.     

Preparation of gold clusters in gelatin layer film using photographic film — 4: Effect of photographic materials

Abstract

The effect of the properties of photographic materials on the preparation of gold clusters in a gelatin layer using a photographic film was examined. The cluster are formed by reducing a gold(I)–thiocyanate complex solution on latent image specks in emulsion grains. Gold clusters are marked as a non-linear optical material, and it was necessary for this purpose to condense the gold clusters in the layer. This was attempted by two methods. The first was to increase the emulsion grains in the layer, and the second was to increase the number of latent image specks on a grain. An ultrafine grain emulsion was applied for the former, while a high-intensity exposure and chemically sensitized emulsions were used to induce the dispersion of latent image specks for the latter. The characteristics of the clusters prepared from those emulsions were compared by absorption spectrum and size distribution. Both methods increased the plasmon absorption due to the gold clusters. The size of the clusters was similar, while absorbance increased with the sulphur-sensitization level. These results suggested that both were effective in condensing the gold clusters in the layer.     

Are all photon radiations similar in large absorbers?--a comparison of electron spectra

Conventional X rays, i.e. X rays generating voltage between roughly 150 and 300 kV, are used in many radio-diagnostic procedures and also in radiobiological experiments. They release less energetic and, therefore, more densely ionising electrons than the high-energy gamma rays from 60Co or from the A bombs. Accordingly, they are considered to be somewhat more effective, especially at low doses. Various radiobiological studies, especially studies on chromosome aberrations have confirmed this assumption, but epidemiological investigations, e.g. the comparison of the excess relative risk for mammary cancer in the X-ray exposed patients and in the gamma-ray exposed A bomb survivors, have not demonstrated a similar difference. In view of the missing epidemiological evidence and largely for the reasons of practicality in radiation protection, the ICRP has recommended the radiation weighting factor unity equally for all photon radiations. However, in the discussion preceding the 2005 Recommendations of the ICRP, the issue remains controversial. In a recent paper, Harder et al. argue--with reference to an assessment by the German Radiation Protection Commission (SSK)--that the use of the same weighting factor for different photon energies can be justified more directly. For high-energy incident photons, they present the degraded photon spectra at different depths in a phantom, and they conclude that much of the difference between high-energy gamma rays and conventional X rays disappears in a large phantom. The present assessment, which is more direct, compares the spectra of electrons released (through pair production, Compton effect and photo effect) in a small and in a very large receptor for the incident photons of 150 keV, 1 MeV and 6 MeV. For the 1 Mev and 6 MeV photons, there is a substantial shift towards smaller electron energies in the large receptor, but the electron spectra remain much harder than those from the 150 keV incident photons. Furthermore, it is seen--in agreement with earlier conclusions by Straume--that for the broad gamma-ray spectrum from the A bombs there is no shift at all to lower energies within the body, but rather some degree of hardening of the radiation. The assumption that distinct differences between high-energy gamma rays and conventional X rays are restricted to small samples must, thus, be rejected. The attribution of the same effective quality factor or radiation weighting factor to all photon energies remains, therefore, an issue that is based on the considerations beyond dosimetry.