Direct Determination of Trace Elements in Meat Samples via High-Resolution Graphite Furnace Atomic Absorption Spectrometry

This work presents a direct and straightforward approach for the determination of trace elements in fish muscle, oyster, and bovine liver via direct solid sample analysis (SS) using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS). The preliminary studies revealed the presence of spectral interferences at the analytical line of Ni at 231.096 nm, which could be corrected subtracting the spectrum of SiO and PO from the sample spectra using least-squares background correction. Moreover, all meat samples were proven homogeneous according to the homogeneity factor (H _e) (all values were <10 mg^½). Pyrolysis (Tp) and atomization (Ta) temperatures were studied and optimized as 800 °C (Tp) and 2500 °C (Ta) for Mn, 700 °C (Tp) and 2600 °C (Ta) for Ni, and 600 °C (Tp) and 2500 °C (Ta) for Rb. Calibration against aqueous standards was proven feasible for Mn determination, whereas Ni and Rb required calibration against solid standards for their quantification. The detection limits achieved were demonstrated adequate for application to food analysis (0.005 μg g^?1 for Mn, 0.002 μg g^?1 for Ni, and 0.1 μg g^?1 for Rb). The developed method was successfully applied for the elemental analysis of fish muscle, oyster, and bovine liver and three certified reference materials, demonstrating good agreement with the certified values and with the reference technique at a 95 % statistical confidence level.     

Thermal properties of fats and oils

Summary 1. Melting points and x-ray diffraction patterns have been determined for cottonseed oil hydrogenated to an iodine value of less than 1, and for a very pure sample of tristearin. 2. Contrary to the observations of previous investigators, the x-ray patterns indicate a well-defined crystal structure with a sharp long spacing and a single sharp short spacing in the lowest-melting form of tristearin. A new pattern, with two short spacings and a long spacing, was observed in tristearin of intermediate melting point. 3. Four polymorphic forms of the hydrogenated cottonseed oil were detected. The x-ray pattern of the lowest-melting form of the hydrogenated oil was similar to that of the correspopnding form of tristearin. The pattern of the highest-melting form of the hydrogenated oil differed from that of either tristearin or β-palmitodistearin, the major components of the oil. Distinctive patterns for the intermediate forms of the hydrogenated oil could not be obtained, presumably because of the instability of the lower melting forms at room temperature. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

An analysis of the machinability of ASTM grades 2 and 3 austempered ductile iron

The main goal of this work is to perform an analysis of the machinability of two ASTM grades of ADI, namely 2 and 3. The samples used in this work were cast and austempered according to ASTM standards for the production of grade 2 (G2) and grade 3 (G3) ADI. Characterization was accomplished through tensile and hardness tests, metallography and X-ray diffraction. Machinability was evaluated by analyzing tool life, cutting forces, surface finish and chip characteristics in turning operations. A quick-stop test was also performed in order to verify some mechanical processes during the chip formation and to analyze the shear plane angle. Tool life when machining G2 was 33% lower than G3 (18 min against 26 min), although the latter is a harder material. Abrasion and adhesion were the wear mechanisms observed through SEM images, whereas in other cast irons mainly abrasion is observed. Cutting forces measurements showed that the value of K_c1,1 decreased 19%, from 1448 to 1175 N/mm², for G2 as the depth of cut increased from 2 to 5 mm at a cutting speed of 80 m/min and 18%, from 1501 to 1236 N/mm², for G3. Surface roughness measurements proved that a smoother surface is obtained for both alloys at f = 0.10 mm/rev when using an insert with nose radius 1.6 mm instead of smaller radii. Both alloys presented similar surface quality. All chips observed were segmented.     

Water-in-water tracer studies of supercritical-water reversing jets using neutron radiography

The flow behavior within vessels containing supercritical water has traditionally been very difficult to measure and to model, due to the highly variable fluid properties and the thick walls needed to contain the high pressures involved with supercritical water. Using neutron radiography, we are able to perform a water-in-water (¹H₂O-in-D₂O) tracer measurement of a supercritical-water reverse-flow vessel that has been designed for salt precipitation in a hydrothermal biomass gasification process. With this method, we have discovered that flow patterns within the vessel are quite disperse and are strongly accelerated by buoyant forces. This method has the beneficial feature that measurements can be taken that are completely non-invasive (for suitable vessel materials, such as zirconium alloys) and do not require the presence of windows or thermowells. We expect that this method will be applicable to a range of research, from reactive processes to nuclear power heat transfer applications, especially when multiple phases, density gradients, or reactions that cause precipitation are present.     

Sculpting Metal-binding Environments in De Novo Designed Three-helix Bundles

De novo protein design is a biologically relevant approach used to study the active centers of native metalloproteins. In this review, we will first discuss the design process in achieving α₃D, a de novo designed three-helix bundle peptide with a well-defined fold. We will then cover our recent work in functionalizing the α₃D framework by incorporating a tris(cysteine) and tris(histidine) motif. Our first design contains the thiol-rich sites found in metalloregulatory proteins that control the levels of toxic metal ions (Hg, Cd, and Pb). The latter design recapitulates the catalytic site and activity of a natural metalloenzyme carbonic anhydrase. The review will conclude with future design goals aimed at introducing an asymmetric metal-binding site in the α₃D framework.     

Experiences of algae in UK waters: a treatment perspective

Algae blooms are a seasonal problem in UK waters and during these periods interferences with treatment plants are reported. This paper presents an analysis of data from 2000 to 2005 demonstrating UK experiences of algae at water treatment works. Cell populations are lower than those reported in the 1970s and 1980s, but reach levels that adversely affect treatment processes. Diatoms and cyanobacteria dominate in spring and autumn respectively. A treatment works including pre-oxidation, coagulation, flotation and filtration removes on average 96% of influent cells, while rapid gravity filters alone remove 63–75%. Cells present in the filtrate are typically either unicellular, micro-algae, or flagellated algae. filter blockages in the spring and autumn are caused by large cells of complex morphology, including the diatoms Melosira and Asterionella . Overall, since the 1980s the key issue with respect to algae treatment has changed from one of treatability to that of process optimisation and economics.     

A new system for crack closure of cementitious materials using shrinkable polymers

This paper presents details of an original crack-closure system for cementitious materials using shrinkable polymer tendons. The system involves the incorporation of unbonded pre-oriented polymer tendons in cementitious beams. Crack closure is achieved by thermally activating the shrinkage mechanism of the restrained polymer tendons after the cement-based material has undergone initial curing.The feasibility of the system is demonstrated in a series of small scale experiments on pre-cracked prismatic mortar specimens. The results from these tests show that, upon activation, the polymer tendon completely closes the preformed macro-cracks and imparts a significant stress across the crack faces.The potential of the system to enhance the natural autogenous crack healing process and generally improve the durability of concrete structures is addressed.     

Investigation of capillary flow in discrete cracks in cementitious materials

A series of experimental studies are presented that simulate capillary flow of water in discrete cracks in cementitious materials. A number of amendments to existing capillary flow theory are adopted which take the form of correction parameters for stick–slip behaviour of the meniscus, frictional dissipation at the meniscus wall boundary and slip between the fluid and solid wall. A benchmark study to examine capillary flow in small diameter glass capillaries is reported and this provides data to validate the amended theoretical model. Predictions made using the amended model closely match the experimental results of capillary rise in discrete cracks in cementitious materials allowing the correction parameters for capillary flow in planar cracks to be determined. Finally, capillary rise in a discrete natural crack of known aperture is considered and a relationship is proposed which predicts the capillary rise response in a natural crack in terms of an equivalent planar crack.     

Tailoring the Structure and Luminescence of Nanostructured Er3+ and Er3+/Yb3+‐Activated Hafnia‐Based Systems

Nanostructured Er³⁺‐ and Er³⁺/Yb³⁺‐activated hafnium oxide films and nanoparticles were prepared from a stable colloidal suspension and investigated by several techniques such as transmission electron microscopy, X‐ray diffraction, dynamic light scattering, atomic force microscopy, Fourier‐transform infrared spectroscopy, and photoluminescence. Low roughness and crack‐free films were deposited by dip‐coating and spin‐coating techniques on vitreous SiO₂ and Si substrates. Nanostructured particles were also synthesized. Remarkable structural and spectroscopic differences were observed for hafnium oxide‐based materials as a function of the Er³⁺ and Er³⁺/Yb³⁺ concentration. The ⁴I_13/2 → ⁴I_15/2 emission bandwidth and the lifetime of the ⁴I_13/2 metastable state of Er³⁺ was tailored through the rare‐earth concentration. The Er³⁺ emission in HfO₂ can be explored for photonic applications.