Self-assembly of nanometer-scale magnetic dots with narrow size distributions on an insulating substrate

The self-assembly of iron dots on the insulating surface of NaCl(001) is investigated experimentally and theoretically. Under proper growth conditions, nanometer-scale magnetic iron dots with remarkably narrow size distributions can be achieved in the absence of a wetting layer. Furthermore, both the vertical and lateral sizes of the dots can be tuned with the iron dosage without introducing apparent size broadening, even though the clustering is clearly in the strong coarsening regime. These observations are interpreted using a phenomenological mean-field theory, in which a coverage-dependent optimal dot size is selected by strain-mediated dot-dot interactions.     

Anisotropic field dependence of the magnetic transition in Cu2Te2O5Br2

In this paper, we present the results of measurements of the thermal conductivity of Cu2Te2O5Br2, a compound where tetrahedra of Cu2+ ions carrying S=1/2 spins form chains along the c-axis of the tetragonal crystal structure. The thermal conductivity was measured along both the c- and the a-direction as a function of temperature between 3 and 300 K and in external magnetic fields H up to 69 kOe, oriented both parallel and perpendicular to the c-axis. Distinct features of (T) were observed in the vicinity of TN=11.4 K in zero magnetic field. These features are unaltered in external fields which are parallel to the c-axis, but are more pronounced when a field is applied perpendicularly to the c-axis. The transition temperature increases upon enhancing the external field, but only if the field is oriented along the a-axis.     

Low field wall mobility in thin conducting ferromagnetic films

The factors which may determine the low field domain wall mobility in thin ferromagnetic films of nickel iron are reconsidered in the light of recent experimental and theoretical work which has been published.     

Einfluß von Lösungsmittel und Halogenessigsäure auf die Fluorescenz von N-Aryl-anthranilsäuren und verwandten Verbindungen

The influence of a pretreatment of flufenamic acid and other N-aryl-anthranilic acids by alkaline saponification and oxidation, as well as the influence of the solvent and the added halogenoacetic acid on fluorescence intensity has been investigated. Derivatives of the flufenamic acid (e.g. esters or amides) must first be hydrolyzed. To render the solution fluorescent solvents with a DK = 0 are required. The halogeno-acetic acids (e.g. mono-, di-, trichloro-, -bromo- and -fluoroacetic acids) with a pK_a-value <1 are suitable. Acids with a pK_a-value >1 are completely unsuitable. Arylsubstituation influences the position of the fluorescence maxima but not the intensity. Anthranilic acid itself shows fluorescence in chloroform-trichloroacetic acid while their m- and p-analogues as well as diphenylamine do not.     

Quantitative determination of acemetacin and its metabolite indometacin in blood and plasma by column liquid chromatography

A column liquid chromatographic (LC) method using UV detection for the determination of acemetacin and its metabolite indometacin in blood is described. The lower detection limit for both compounds is ca. 25 micrograms/l, the precision (coefficient of variation) is 6% for acemetacin and 10% for indometacin. The method is also suited for determination of both compounds in plasma, precisions in this case are even better than for blood, i.e. around 3% for both acemetacin and indometacin. Blood samples of three volunteers who had received 90 mg of acemetacin orally were analysed using the new method and very good agreement with results from a thin-layer chromatographic/fluorescence method was found.     

New embedded boundary-type quadrature formulas for the simplex

In this paper we consider the problem of the approximation of the integral of a smooth enough function f(x,y) on the standard simplex $\Delta _{2} \subset \mathbb{R}^{2}$ by cubature formulas of the following kind: $${\int\limits_{\Delta _{2} } {f{\left( {x,y} \right)}dxdy} } = {\sum\limits_{\alpha = 1}^3 {{\sum\limits_{i,j} {A_{{\alpha ij}} \frac{{\alpha ^{{i + j}} }}{{\alpha x^{i} \alpha y^{j} }}f{\left( {x_{\alpha } ,y_{\alpha } } \right)} + E{\left( f \right)}} }} }$$ where the nodes $\left( x_{\alpha},y_{\alpha}\right) ,\alpha=1,2,3$ are the vertices of the simplex. Such kind of quadratures belong to a more general class of formulas for numerical integration, which are called boundary-type quadrature formulas. We discuss three classes of such formulas that are exact for algebraic polynomials and generate embedded pairs. We give bounds for the truncation errors and conditions for convergence. Finally, we show how to organize an algorithm for the automatic computation of the quadratures with estimate of the errors and provide some numerical examples.     

Trapping of a Polyketide Synthase Module after C−C Bond Formation Reveals Transient Acyl Carrier Domain Interactions

Modular polyketide synthases (PKSs) are giant assembly lines that produce an impressive range of biologically active compounds. However, our understanding of the structural dynamics of these megasynthases, specifically the delivery of acyl carrier protein (ACP)-bound building blocks to the catalytic site of the ketosynthase (KS) domain, remains severely limited. Using a multipronged structural approach, we report details of the inter-domain interactions after C−C bond formation in a chain-branching module of the rhizoxin PKS. Mechanism-based crosslinking of an engineered module was achieved using a synthetic substrate surrogate that serves as a Michael acceptor. The crosslinked protein allowed us to identify an asymmetric state of the dimeric protein complex upon C−C bond formation by cryo-electron microscopy (cryo-EM). The possible existence of two ACP binding sites, one of them a potential “parking position” for substrate loading, was also indicated by AlphaFold2 predictions. NMR spectroscopy showed that a transient complex is formed in solution, independent of the linker domains, and photochemical crosslinking/mass spectrometry of the standalone domains allowed us to pinpoint the interdomain interaction sites. The structural insights into a branching PKS module arrested after C−C bond formation allows a better understanding of domain dynamics and provides valuable information for the rational design of modular assembly lines.     

Long-term evolution of mid-altitude quasi-satellite orbits

Quasi-satellite orbits are of great interest for the exploration of planetary moons because of their dynamical features and close proximity with respect to the surface of scientifically relevant objects like Phobos and Deimos. This paper explores the equations of the elliptical Hill problem, offering a new analytical insight into the long-term evolution of mid-altitude quasi-satellite orbits. Our developments are based on the Yamanaka–Ankersen solution of the Tschauner–Hempel equations and capture the effects of the secondary’s gravity and orbital eccentricity on the shape and orientation of near-equatorial retrograde relative trajectories. The analytical solution of the in-plane and out-of-plane components of the secular motion is achieved by averaging over the relative longitude of a spacecraft as seen from the co-rotating frame of the two primaries. Developments are validated against the numerical integration of quasi-periodic trajectories that densely cover the surface of three-dimensional invariant tori. This analysis confirms the stable nature of quasi-satellite orbits and provides new tools for future spacecraft missions such as the Martian Moons eXploration envisaged by JAXA.

     

ΔThe effect of co-doping on the yttrium local environment and ionic conductivity of yttria-stabilised zirconia

The effect of co-doping yttria-stabilised zirconia with calcia and scandia has been investigated. Changes in the yttrium ion local environment have been monitored using solid-state magic angle sample spinning ⁸⁹Y nuclear magnetic resonance. The effect on the low-temperature (below 320 °C) bulk ionic conductivity has been observed using AC impedance spectroscopy. It was found that the number of oxygen vacancies in the nearest-neighbour sites to yttrium ions decreased on co-doping with scandia, correlating with an increase in conductivity, but increased on co-doping with calcia, correlating with a decrease in conductivity. This behaviour can be explained by proposing the trapping of oxygen vacancies in the nearest-neighbour yttrium ion sites so that they no longer contribute to the conduction mechanism.

Doping of a high calcium oxide metaphosphate glass with titanium dioxide

This study investigates the effect of doping a high calcium oxide containing metaphosphate glass series (CaO)₄₀(Na₂O)₁₀(P₂O₅)₅₀ with TiO₂ (1, 3, and 5 mol%). TiO₂ incorporation increased the density and glass transition temperature while reduced the degradation rate (5 mol% in particular) by twofold compared with (CaO)₃₀ system reported previously. This has been confirmed by ion release and the minimal pH changes. TiP₂O₇, NaCa(PO₃)₃ and CaP₂O₆ phases were detected for all TiO₂-containing ceramics. XPS showed that the surface is composed of Ca, P, and Ti. Ti was recognized mainly as TiO₂, but its total amount was lower than theoretical values. ³¹P magic angle spinning (MAS) NMR showed a downfield shift of the ³¹P lineshape with increasing TiO₂, interpreted as an effect of the titanium cation rather than an increase in the phosphate network connectivity. FTIR showed that incorporation of TiO₂ increased the strength of the phosphate chains, and the O/P ratio while introducing more Q¹ units into the structure at the expense of the Q² units. There were no differences, however, in surface topography roughness and free energies between these glasses. These results suggested that TiO₂ and CaO were acting synergistically in producing glasses with controllable bulk and structural properties.