Ageing of wet-synthesized oxide powders

Wet chemical synthesis of precursor oxide ceramics is a method to obtain small particulate powders. Such powders are far more prone to ageing in air than more traditional precursors. Thermogravimetric analysis is used to highlight the species responsible for the ageing of ceramic precursors. Indeed water and carbon dioxide are observed to evolve from aged powders. Ceramics obtained from aged precursors can reach a very low final density with respect to the theoretical value. A large degree of the original sintering properties can be recovered after washing the aged powders with ethanol in a basic medium.     

Influence of extra-framework cations on the adsorption properties of X-faujasite systems: microcalorimetry and molecular simulations

Isotherms and differential enthalpies of adsorption are obtained for nitrogen at ambient temperature on monovalent (Li(+), Na(+), K(+)) and divalent (Ca(2+), Ba(2+), Sr(2+), Mn(2+)) substituted X-faujasite systems by microcalorimetry measurements. These experimental data are compared with those obtained by combining grand canonical Monte Carlo simulations and newly derived force fields for describing the interactions between the extra-framework cations and the adsorbates obtained from a simple model based only on the intrinsic properties of the cations. It is the first time that such good qualitative agreement is reported between experiment and simulation for a series of both monovalent and divalent cations.     

Spectral and scattering theory for a Schrödinger operator with a class of momentum-dependent long-range potentials

Let be the selfadjoint operator for the static electromagnetic field where W _j for 0, 1, 2, ..., n is a sum of (i) a short-range potential and (ii) a smooth long-range potential decreasing at as |x|^- with in (0, 1]. Then for >1/2, asymptotic completeness holds for the scattering system (H, H ₀).     

A new high: Cannabis as a budding source of carbon-based materials for electrochemical power sources

Cannabis sativa L., a low-cost, fast-growing herbaceous plant, is seeing a resurgence in widespread cultivation as a result of new policies and product drive. Its biodegradable and environmentally benign nature coupled with its high specific surface area and three-dimensional hierarchal structure makes it an excellent candidate for use as a biomass-derived carbon material for electrochemical power sources. It is proposed that this ‘wonder crop’ could have an important role in the energy transition by providing high-functioning carbon-based materials for electrochemistry. In this article, all instances of C. sativa usage in batteries, fuel cells and supercapacitors are discussed with a focus on highlighting the high capacity, rate capability, capacitance, current density and half-wave potential that can be achieved with its utilisation in the field.     

The ν4 fundamental of three isotopic species of CF4

The vibration-rotation spectra of the ν₄ fundamental of ¹²CF₄, ¹³CF₄, and ¹⁴CF₄ have been observed with 0.06 cm^?1 resolution. A least squares fit of the data has been used to evaluate the pertinent molecular constants. The band centers are 631.199, 629.285, and 627.348 cm^?1 for ¹²CF₄, ¹³CF₄, and ¹⁴CF₄, respectively. The Coriolis constant ζ₄ has been estimated for the three isotopes.     

Attenuation of vehicle noise over short grass

Field experiments to investigate the attenuation of noise from single vehicles over short grass indicate that for a microphone height of 1·2 m and a source/receiver distance <30 m, the rate of attenuation is 4·8 dB(A) per doubling of distance. Some evidence is presented to suggest that for source/receiver distances >30 m the rate of attenuation increases with distance.     

Infrared microspectroscopic study of the thermo-oxidative degradation of hydroxy-terminated polybutadiene/isophorone diisocyanate polyurethane rubber

Hydroxy-terminated polybutadiene/isophorone diisocyanate (HTPB/IPDI) polyurethane rubber which was aged in air at elevated temperatures has been studied by infrared microspectroscopy. Spectra were collected in transmission mode on microtomed samples. Analysis of sets of spectra taken across the sectioned material showed that most of the degradation occurred in the polybutadiene part of the polymer and that the urethane linkage was essentially unchanged. The trans isomer of the polybutadiene appears to be preferentially degraded compared with the vinyl isomer. The IR technique does not provide significant information about the cis isomer. The IR spectra indicated that likely degradation products included acids, esters, alcohols, and small amounts of other products containing a carbonyl functional group. Band area ratios, supported by a principal components analysis, were used to derive degradation profiles for the material. These profiles were steep-sided indicating an oxygen diffusion limited process.     

Raman spectroscopic investigation on the microenvironment of the liver tissues of Zebrafish (Danio rerio) due to titanium dioxide exposure

Nano titanium dioxide (nTiO₂), generally considered to be toxicologically inert, is manufactured in large quantities and extensively applied in consumer products. The small size and large surface area endow them with an active group or intrinsic toxicity. Advances in instrumentation are making Raman spectroscopy the tool of choice for an increasing number of (bio) chemical applications. One of the great advantages of this technique is its ability to provide information on the concentration, structure and interaction of biochemical molecules in their microenvironments within intact cells and tissues, non-destructively. Zebrafish (Danio rerio), one of the most important vertebrate model organisms used in developmental biology, are increasingly used in biomedical research, particularly as a model of human disease. In the present work, an attempt is made to study the effect of titanium dioxide, both nano and bulk, on the microenvironment of the liver tissues of Zebrafish using FT-Raman spectroscopy. The results of the present study suggest that TiO₂ exposure demonstrate a marked influence on the microenvironments of the liver tissues of Zebrafish. A shift to a higher wavenumber and an increase in the intensity of the band at ∼1087 cm⁻¹ in the TiO₂ exposed tissues suggest that some of the conformational changes resulting from the alkali recovery process takes place due to TiO₂ exposure. The decreased intensity ratio (I₃₂₂₀/I₃₄₀₀) observed in the titanium-exposed tissues suggests a decreased water domain size, which could be interpreted in terms of weaker hydrogen-bonded molecular species of water in the TiO₂ exposed tissues. The observed shift of COO⁻ bands to higher frequencies shows the disruption of salt bridges as a result of a change in the oppositely charged partners and due to the enhanced random coil conformation. The variation in the intensity ratio of the tyrosyl doublet (I₈₅₈/I₈₂₅) indicates variation in the hydrogen bonding of the phenolic hydroxyl group due to TiO₂ exposure. The results further suggest that the microenvironments are greatly altered due to titanium nano exposure when compared to titanium bulk. In conclusion, the results indicate that FT-Raman spectroscopy might be a useful tool for rapid assessment of nano particle biological interactions.     

The path to fusion power

Fusion, which powers the sun and stars, is potentially an environmentally responsible and intrinsically safe source of essentially limitless energy. The Joint European Torus (JET) has produced 16 MW of fusion power, and construction of a power station sized device called ITER (International Tokamak Experimental Reactor), which should produce at least 500 MW, is about to begin. Further work on fusion technologies is also needed, including construction of the proposed International Fusion Materials Irradiation Facility (IFMIF) which will test materials that will have to stand up to years of intense neutron bombardment in a fusion power station. Given i) its potential attractions (which include essentially limitless fuel, and the absence of green-house gas and of long-lived radio-active by-products), and that ii) it looks as if the economics of fusion power will be acceptable, the time has come to develop fusion as rapidly as reasonably possible. The status and potential advantages of fusion are being described, together with the outstanding challenges, the remaining steps and a timetable for developing fusion power.