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A new approach to X-ray absorption analysis is presented in this paper. The equation log (I2/I1) = KWA + KB is used, from which the weight fraction WA of a given element can be calculated in various solvents when only a calibration curve from one solvent and the absorption of the new solvent at two wavelengths (λ1 and λ2) are known.
This treatment uses the absorption at two wavelengths, one on each side of an absorption edge of the element under study. The desired wavelengths can be conveniently obtained from the Kα and Kβ radiation of an element with an atomic number just higher than the element under study. An easy way to accomplish this is to use the desired target element as the sample in an X-ray spectrometer. The Kα and Kβ radiations are then resolved with an appropriate analyzing crystal, and the absorption measurements are made consecutively.
The advantages of this approach are twofold. First, it is only necessary to do a full calibration curve in one solvent; calibration in other solvents can be calculated with only a knowledge of the absorption of that pure solvent at the wavelengths used, which can. either be determined experimentally or calculated. Secondly, the required experimental data can be collected very conveniently in an X-ray spectrometer.
Disease in a pig herd can have major economic impacts, hampering agricultural processes and creating barriers to trade. Importantly, an outbreak of disease can also pose a risk to human health. It is currently unknown what effects different rearing regimes might have on the incidences of zoonoses in pigs. Outdoor rearing of pigs has gained popularity recently due to interest in animal welfare and an increase in the marketability of organic food. But it is unknown if outdoor rearing can alter the gut microbiology of pigs, and if pigs reared outdoors are more susceptible to zoonotic infections. A method for analysing bacterial populations present in the pig gut has been developed based on amplification of the 16S ribosomal DNA. This technique, known as Terminal Restriction Fragment Length Polymorphism (T-RFLP) analysis has been used for studying bacterial populations in environments such as soil (Osborn et al., 2000) and faeces (Li et al., 2007). It uses fluorescently labelled forward and reverse primers to generate labelled amplicons, followed by a restriction endonuclease digest of the amplified DNA to give rise to labelled terminal fragments that vary between different species. These terminal fragments are then detected using electrophoretic separation and laser detection, and identified based on the fragment size. This study aims to develop a protocol for using this technique on pure cultures of control organisms.
The National Institute for Health and Clinical Excellence (NICE) provides guidance to the National Health Service (NHS) in England and Wales on funding and use of new technologies. This study examined the impact of evidence, process and context factors on NICE decisions in 2004–2009. A data set of NICE decisions pertaining to pharmaceutical technologies was created, including 32 variables extracted from published information. A three-category outcome variable was used, defined as the decision to ‘recommend’, ‘restrict’ or ‘not recommend’ a technology. With multinomial logistic regression, the relative contribution of explanatory variables on NICE decisions was assessed. A total of 65 technology appraisals (118 technologies) were analysed. Of the technologies, 27% were recommended, 58% were restricted and 14% were not recommended by NICE for NHS funding. The multinomial model showed significant associations (p ⩽ 0.10) between NICE outcome and four variables: (i) demonstration of statistical superiority of the primary endpoint in clinical trials by the appraised technology; (ii) the incremental cost-effectiveness ratio (ICER); (iii) the number of pharmaceuticals appraised within the same appraisal; and (iv) the appraisal year. Results confirm the value of a comprehensive and multivariate approach to understanding NICE decision making. New factors affecting NICE decision making were identified, including the effect of clinical superiority, and the effect of process and socio-economic factors.
Embedded wafer-level ball grid array (eWLB) is investigated as a low-cost plastic package for automotive radar applications in the 76–81 GHz range. Low transmission losses from chip to package and board are achieved by appropriate circuit and package design. Special measures are taken to effectively remove the heat from the package and to optimize the package process to achieve automotive quality targets. A 77 GHz radar chip set in eWLB package is developed, which can be applied on the system board using standard solder reflow assembly. These radar MMICs provide excellent radio frequency (RF) performance for the next generation automotive radar sensors. The potential for even higher system integration is shown by a radar transceiver with antennas integrated in the eWLB package. These results demonstrate that eWLB technology is an attractive candidate to realize low-cost radar systems and to enable radar safety affordable for everyone in the near future.
Ion implantation was used to form high densities (~1019
/cm3) of small oxide precipitates in Ni in order to
investigate the strength mechanism produced by such highly refined
structures. Nanometer-size precipitates of Al2O3 and
NiO are found to block dislocation motion in the Ni matrix, producing yield
strengths up to 4.6 GPa, more than twice that of hardened bearing steel.
Dispersion strengthening theory, developed for micrometer-size precipitates
and spacings, was found to account quantitatively for the yield strengths
produced by nanometer-size oxides as well. Nanoindentation plus
finite-element modeling was used to quantify the mechanical properties of
implanted metal layers, and was extended to examination of amorphous Si
layers formed by self-ion implantation. The amorphous phase was found to
have a yield strength of 4.45 ± 0.20 GPa, Young's modulus of 144 ± 7 GPa,
and hardness of 10.3 ± 0.4 GPa. The modulus and hardness are reduced by 10%
and 15%, respectively, from those of crystalline Si.
The microstructure of Fe implanted with up to 50 at.% C was found to consist of hexagonal iron carbide precipitates oriented with respect to the Fe matrix. For higher C concentrations, an amorphous phase forms. This concentration dependence is explained in terms of the lattice structure of the iron carbide. In Ti-implanted Fe, substitutional Ti was found in the bcc Fe lattice for concentrations ≤ 15 at.% Ti. The work of others suggests that amorphous phases form for ≥ 33 at.% Ti. These results are discussed in terms of concentration boundaries of the ternary Fe(Ti,C) amorphous phase.
Ion beam alloying methods are currently being used to form metastable alloys , both for fundamental investigations of such alloys as well as for potential use to improve physical properties of components . An important consideration in metal alloys is what phase will form upon implantation; one aspect of this question is to determine when amorphous phases will form. Rules are currently being advanced to predict alloy systems which will yield amorphous phases. By using ion irradiation and ion beam mixing as well as ion implantation, such rules can be evaluated over entire composition ranges.
To gain insight into amorphous phase formation, we have studied Fe alloys implanted with C, Ti and Ti + C. The Fe(C) alloys exhibit compound precipitation and amorphous phase formation; the precipitation and the concentrations at which the amorphous phase appears can be accounted for by considerations of the structure of the hexagonal carbide which forms. Based on conventional uses of the Fe(C) system, such alloys may be useful for improving mechanical properties by implanting C into ferrous components. Iron implanted with Ti is examined to a limited extent here, but by including ion irradiation studies by others , a more complete characterization of Fe(Ti) alloys is obtained. The microstructures of Fe(C) and Fe(Ti) are examined along with the known composition limits of amorphous Fe(Ti,C) alloys, which are important for their improved mechanical properties . Taken together, a more complete determination of amorphous phase formation in this ternary system is obtained.
In situ transmission electron microscopy was used to show that nanocrystalline nickel produced by pulsed-laser deposition undergoes abnormal grain growth at moderate temperatures (225-400°C). The growth rate was found to increase with thickness for the three film thicknesses examined, 50, 80 and 150 nm. The abnormal growth proceeded in an irregular manner: initiation sites and growth direction were unpredictable, and the grains exhibited no preferred orientation. Some abnormal grains show internal boundaries such as twins, while others exhibited lattice misalignments across the grain body. The grains contain many defects, including dislocations, stacking faults and surprisingly, stacking fault tetrahedra. The stacking fault tetrahedra are not a result of quenching nor of electron irradiation-induced lattice displacements; they instead are thought to form from vacancies trapped in the growing grain as it incorporates lower-density material at the high-angle grain boundaries in the nanocrystalline matrix.
Surface layers of the icosahedral phase of Al(Mn) have been formed from thin, alternating Al/Mn layers deposited on Al or Fe surfaces by rapid electron-beam or laser melting, by ion beam mixing, and by solid-state diffusion. The electron beam and laser treatments are similar to other liquid quenching techniques used previously to form the phase, but have well defined temperature histories which allow us to place limits on the melting point of the icosahedral phase, the time needed for its nucleation from the melt, and its growth velocity. Ion beam mixing is a way of forming the icosahedral phase which is quite different from melt quenching; the phase is formed during ion beam mixing at temperatures of 100–200°C. For mixing at ≤60C an amorphous phase with icosahedral short-range order is formed; this phase can be converted to the icosahedral phase by subsequent annealing. Formation of the icosahedral phase by reacting the as-deposited layers in the solid state is a new technique not previously reported. The results presented here place new restrictions on proposed structural and thermodynamic models for the icosahedral phase.
Radiation damage in V2Os induced by electrons in the energy range 0-3 keV has been studied by high resolution electron microscopy, X-ray photoelectron spectroscopy and mass spectrometry. Different phase transformations were observed when V205 was irradiated by electrons of different energies. The damage kinetics and the role of electron radiation enhanced diffusion were investigated. It was found that nucleation and growth of lower oxides was driven by electron radiation enhanced diffusion.
SiO2 films were prepared at a substrate temperature of 100°C by the simultaneous use of a microwave ion source and an ICB system. Transparent and good insulating SiO2 films could be obtained by using 02 gas ions, and they were thermally and chemically stable. Furthermore, both the ionization energy and the incident energy of the 02 gas ions were found to enhance the chemical reaction between SiO and 02 molecules, resulting in the Si02 film formation at a low substrate temperature.
Femtosecond time-resolved reflectivity measurements performed on highly oriented pyrolytic graphite (HOPG) and diamond elucidate the nature of the phase transition from solid to liquid carbon. In HOPG, we find that a high-reflectivity phase lasting as long as 10 ps appears when the surface is irradiated with pulse fluences in excess of 0.13 J/cm2, the critical fluence for melting. This transforms within 30 ps into an equilibrium low-reflectivity phase lasting hundreds of ps, similar to behavior observed in picosecond reflectivity experiments. The results suggest the occurrence of a two-step phase transition (graphite -> liquid metal -> liquid insulator) when HOPG is excited above the critical fluence. Similar results are obtained with diamond.
We have discovered that the β and γ brasses of Cu-Zn exhibit clearly resolved increases in reflectance upon melting with a 30 ns ruby laser, which allow their melt durations to be readily measured. This system thus offers potential for obtaining quantitative information about the solidification kinetics of metals. We have also found that a heteroepitaxial layer of β' brass is formed on the surface of (ordered) γ brass with 63 wt.% Zn following pulsed laser-induced melting. The β' layer is interpreted to mean that the metastable β phase (bcc) formed on the liquid-solid interface as the γ substrate attempted to regrow, and that β ordered to β' (B2) during cooling. The β formation implies that undercoolings > 16 K were attained during the attempted regrowth of the γ phase.
Previously we reported a substantial (∼ 50 %) decrease in shear modulus prior to amorphization in Kr irradiated Zr3Al, and proposed that amorphization is triggered when the crystalline lattice becomes unstable against shear stress. In the present work, the relation between amorphization and shear elastic instability has been investigated in two additional compounds (FeTi and NiAl) during room temperature irradiation with 1.7-MeV Kr+. A shear modulus was measured using Brillouin scattering; structural information was obtained in situ in a high voltage electron microscope interfaced to a tandem accelerator.
During irradiation of FeTi, chemical disordering and a large (∼40 %) decrease of shear modulus were observed, and an amorphous phase developed subsequently. In contrast, NiAl remained crystalline and chemically ordered during irradiation, and exhibited only a ∼ 10 % decrease in shear modulus. Hence, these two results provide further support that a shear instability triggers irradiation-induced amorphization. The shear instability mechanism may also apply to other solid-state amorphization techniques, e.g. hydrogen charging and mechanical deformation.