Short communication: On the potential use of materials with heterogeneously distributed parent and daughter isotopes as primary standards for non-U-Pb geochronological applications of laser ablation inductively coupled mass spectrometry (LA-ICP-MS)

Many new geochronological applications of laser ablation inductively coupled mass spectrometry (LA-ICP-MS) have been proposed in recent years. One of the problems associated with this rapid growth is the lack of chemically and isotopically homogeneous matrix-matched primary standards to control elemental fractionation during LA-ICP-MS analysis. In U-Pb geochronological applications of LA-ICP-MS this problem is often addressed by utilising matrix-matched primary standards with variable chemical and isotopic compositions. Here I derive a set of equations to adopt this approach for non-U-Pb geochronological applications of LA-ICP-MS.

The Influence of Mixing Orders on the Microstructure of Artificially Prepared Sand-Clay Mixtures

The mixing order of silica sand, clay (kaolinite), and water controls the microstructure of resulting artificial soil samples. Most homogeneous microstructures can be achieved by applying the mixing order “sand-water-clay.” The following methods were used to validate this statement: (1) optical observation, (2) X-ray tomography, (3) scanning electron microscopy, and (4) Mercury intrusion porosimetry. For all samples, clays are mainly organized in a homogeneous matrix but are also dispersed heterogeneously in micrometer-sized layers surrounding sand particles, particularly where sand grains show a greater roughness. At water contents ≥1.5 w L , the microstructures are visually similar from the mm to μm scale whatever mixing order is used. However, for water contents lower than 1.5 w L , the mixing order controls the distribution of the clay particles. This paper proposes a motivated choice of a preparation protocol of artificial clayey materials to be used in laboratory experiments. It might contribute to better understanding and modeling grain movements and arrangements in artificial muds, used for instance in underground mining, foundation settlement, hydraulic containment, road construction, soil stabilization, and in natural soils in the occurrence of soil liquefaction, industrial brick manufacturing, and in studying shear processes in tectonic fault zones.

Substitution of milk allergen ingredient by blood plasma powder in custard with different sweeteners

Animal blood is a by-product, which can be utilized in a value-adding way instead of being wasted. Allergen substitution is a good possibility especially for a substance that is difficult to substitute, such as milk. Blood plasma is a fluid with high protein content without blood (iron) taste and colour, so it is similar to milk in several ways. While investigating the substitution of milk, it is advisable to investigate the substitution of sugar as well because a lot of consumers who exclude milk from their diet find the glycaemic index and energy content of foods important. The investigated model food is a simple, homogeneous matrix: vanilla custard with milk and with and without sugar and vanilla custard with blood plasma and with and without sugar. Colour, pH and rheological attributes of custard sample groups were measured. According to the results the used protein source as well as sweetener significantly determine the colour, pH and texture of the final product. However, colour and pH are easy to change with other components (food colours, acidity regulators) and the effect of milk and sugar substitution on rheological attributes might not be possible to detect without instrumental analysis.

The study of the projective transformation under the bilinear strict equivalence

The study of linear time invariant descriptor systems has intimately been related to the study of matrix pencils. It is true that a large number of systems can be reduced to the study of differential (or difference) systems, $S\left ( {F,G} \right )$, $$\begin{align*} & S\left({F,G}\right): F\dot{x}(t) = G{x}(t) \left(\text{or the dual, } F{x}(t) = G\dot{x}(t)\right), \end{align*}$$and $$\begin{align*} & S\left({F,G}\right): Fx_{k+1} = Gx_k \left(\text{or the dual, } Fx_k=Gx_{k+1}\right)\!, F,G \in{\mathbb{C}^{m \times n}}, \end{align*}$$and their properties can be characterized by homogeneous matrix pencils, $sF - \hat{s}G$. Based on the fact that the study of the invariants for the projective equivalence class can be reduced to the study of the invariants of the matrices of set ${\mathbb{C}^{k \times 2}}$ (for $k \geqslant 3$ with all $2\times 2$-minors non-zero) under the extended Hermite equivalence, in the context of the bilinear strict equivalence relation, a novel projective transformation is analytically derived.

Garnet-Rich Veins in an Ultrabasic Amphibolite from NE Sardinia, Italy: An Example of Vein Mineralogical Re-Equilibration during the Exhumation of a Granulite Terrane

A complex system of mono- and polymineralic centimeter-thick veins occurs within the ultrabasic amphibolites of Montigiu Nieddu hill in northeastern Sardinia, and they are filled with garnet, amphibole, chlorite, and epidote. Some garnet-rich veins are margined by an amphibole layer at the interface with the host rock and/or show replacement of epidote concentrated in the vein core. Together with homogeneous matrix garnet (Grt1), millimetric, euhedral, and strongly zoned garnet porphyroblasts occur within these veins. The estimated pressure–temperature conditions (P = 1.0–1.7 GPa, T = 650–750 °C) for the formation of Grt1 match the metamorphic peak and early exhumation derived previously for the host rocks and confirm that the garnet veins also formed under high-pressure (HP) conditions. The igneous protolith of the host rocks experienced HP metamorphism in a subduction zone and underwent exhumation in an exhumation channel. The vein system in the ultrabasic amphibolites formed by cyclic hydrofracturing as rapid and transient events such as crack-seal veining. The growth of multiple vein-filling mineral assemblages indicates the formation of separate vein-producing cycles.

Enhanced D-H: an improved convention for establishing a robot link coordinate system fixed on the joint

Purpose Robot kinematic modeling needs to be based on clear physical concepts. The widely used Denavit–Hartenberg (D–H) convention requires the coordinate system to be established on an extension of the axis. This leads to non-trivial problems which this study seeks to address by developing an improved convention. Design/methodology/approach First, the problems associated with the traditional D–H convention are systematically analyzed. Then, pursuant of solving these problems, an enhanced Denavit–Hartenberg (ED–H) convention is proposed, and a procedure is delineated for establishing the coordinate frame and obtaining the associated parameters. The transformation equations are derived based on a homogeneous matrix. The characteristics of traditional D–H and ED–H with regard to kinematics and dynamics are comprehensively compared. Finally, an application of dynamics for lead-through programming and collision protection is undertaken to validate the proposed ED–H method. Simulations and experiments are carried out using the Tiansui-One cooperative robot platform with the aim of exploring the merits of the proposed convention. Findings The proposed convention is compatible with traditional methods and can solve the problems inherent in these methods. The main characteristic of ED–H is that the coordinate system is fixed on the joint, which is a general modeling method. Originality/value An enhanced D–H convention is proposed to establish a unified, intuitive and accurate link model that exhibits stronger adaptability than traditional D–H and can be used effectively in kinematic and dynamic modeling of mechanical arms.

Composite Cryogel with Polyelectrolyte Complexes for Growth Factor Delivery

Macroporous scaffolds composed of chitosan (CHI), hydroxyapatite (HA), heparin (Hep), and polyvinyl alcohol (PVA) were prepared with a glutaraldehyde (GA) cross-linker by cryogelation. Addition of PVA to the reaction mixture slowed down the formation of a polyelectrolyte complex (PEC) between CHI and Hep, which allowed more thorough mixing, and resulted in the development of the homogeneous matrix structure. Freezing of the CHI-HA-GA and PVA-Hep-GA mixture led to the formation of a non-stoichiometric PEC between oppositely charged groups of CHI and Hep, which caused further efficient immobilization of bone morphogenic protein 2 (BMP-2) possible due to electrostatic interactions. It was shown that the obtained cryogel matrix released BMP-2 and supported the differentiation of rat bone marrow mesenchymal stem cells (rat BMSCs) into the osteogenic lineage. Rat BMSCs attached to cryogel loaded with BMP-2 and expressed osteocalcin in vitro. Obtained composite cryogel with PEC may have high potential for bone regeneration and tissue engineering applications.

Exotic garnet–clinopyroxene–K-feldspar granulites from the Chepelare shear zone, Central Rhodope massif, Bulgaria: implications for high-pressure granulite facies metamorphism

Garnet–clinopyroxene–K-feldspar granulite occurs as a thick layer or boudin within the variegated rocks of the Chepelare shear zone in the Central Rhodope massif, Bulgaria. It consists of several domains: mesocratic homogeneous matrix (clinopyroxene–plagioclase–K-feldspar–quartz ± amphibole), porphyroblastic garnet, K-feldspar and clinopyroxene, and strongly foliated fine-grain bands (chloritized biotite–chlorite–prehnite–albite ± epidote). The origin and nature of the matrix mineral association is still unclear. The peak porphyroblast association forms at the expense of plagioclase from the matrix at higher pressure. The fine-grain deformation zones channel the lattermost fluid infiltration. The clinopyroxene-garnet and Zr-in-titanite thermometry give temperatures higher than 790–860 ºC at 2 GPa and, with thermodynamic modeling, suggests crystallization at ~1.8–2.1 GPa and temperature of ~850 ºC in HP granulite field for the porphyroblast granulite association.

On Multiple Inhomogeneities in Plane Elasticity

In this paper we present some new analytical techniques which have been recently developed to solve for problems of circular elastic inhomogeneities in anti-plane and plane elasticity. The inhomogeneities may be composed of different materials and have different radii. The matrix may be subjected to arbitrary loadings or singularities. The solution to this heterogeneous problem is sought as a transformation performed on the solution of the corresponding homogeneous problem, i.e., the problem when all the inhomogeneities are removed and the homogeneous matrix is subjected to the same loading/singularities, a procedure which has been dubbed ‘heterogenization’. In previous works, a single inhomogeneity or hole has been considered and the transformation has been shown to be purely algebraic in the antiplane case and involves differentiation of the Kolosov-Mushkelishvili complex potentials in the plane case. Universal formulas, i.e., formulas which are independent of the loading/singularities, that express the stresses at the inter-face of the inhomogeneity in terms of the stresses that would have existed at the same interface had the inhomogeneity been absent, have been be derived. The solution for a single inhomogeneity bonded to a matrix which is subjected to arbitrary loading/singularities can then in principle be used systematically in a Schwarz alternating method to obtain the solution for multiple inhomogeneities to any degree of accuracy. However alternative and innovative methods have been sought which lead to a much faster convergence and in some cases to exact expressions in terms of infinite series. The aim of this paper is to present some of the progress that has been made in this direction.

Effect of Activator Concentration on the Properties of Metakaolin-Based Geopolymer

In the present study, an alkaline solution, prepared by sodium silicate (Na2SiO3) and sodium hydroxide (NaOH), was used as an activator for the preparation of a metakaolin-based geopolymer with high compressive strength. The effects of the factors, including the modulus (SiO2/Na2O ratio) of the alkaline activator, activator concentration, curing temperature, and curing time on the mechanical properties of the geopolymer were examined using orthogonal tests. Test results showed that the concentration of the alkaline activator is the primary factor affecting the mechanical properties of the geopolymer, followed by the modulus of the alkaline activator. The compressive strength of the geopolymer increases with an increase in activator concentration and decrease in the modulus of the alkaline activator. Subsequently, the reaction degree of the geopolymer and the reaction products corresponding to various concentrations of the activator were investigated using microcalorimetric analysis, Fourier Transform Infrared (FT-IR) analysis, and Scanning electron microscopy-Energy Dispersive Spectrometer (SEM-EDS) analysis, and the mechanism of the activator concentration affecting the geopolymer properties was also studied. It was found that the hydrolysis reaction and the polymerization degree were improved with an increase in the activator concentration. When the activator concentration increased from 50% to 80%, the compressive strength of the geopolymer increased from 21.54 MPa to 99.89 MPa. In addition, the SEM images also showed that the reaction products with a higher activator concentration, had a denser and more homogeneous matrix than that of products with a lower activator concentration.