Effect of oxalate test dose size on absolute and percent oxalate absorption

The purpose of this pilot study was to establish the dependence or independence of oxalate absorption on the quantity of the test dose of sodium oxalate over a range of test doses corresponding to physiological dietary oxalate intake values. Gastrointestinal oxalate absorption was measured with the [¹³C₂]oxalate absorption test. Six healthy volunteers were always tested under standardized dietary conditions with 63 mg dietary oxalate and 800 mg dietary calcium per day. The volunteers were tested thrice each with sodium oxalate test doses of 25, 50, 200, and 600 mg. Additionally, 1000 mg sodium oxalate was applied once to three of these volunteers. The oxalate absorption of the six volunteers tested under the standardized conditions with 50 mg sodium [¹³C₂]oxalate was 7.2 ± 2.62 % (mean ± SD), similar to the 120 volunteers tested previously: 8.0 ± 4.4 % (mean ± SD). The tests with sodium [¹³C₂]oxalate doses in the range 25–1000 mg revealed similar percent oxalate absorption values. In conclusion, in healthy volunteers, the amount of oxalate absorbed in the gastrointestinal tract increased proportionally with the higher test doses of oxalate. However, percent oxalate absorption remained unchanged with test doses in the dose range of physiological dietary oxalate intakes.     

A Fixed Point Theorem for Decreasing Functions

Let E be a Banach spaces ordered by a cone K. We prove a fixed point theorem for Lipschitz continuous monotone decreasing functions f: K → K, which proves the existence of a unique fixed point in cases where the Lipschitz constant of f is bigger than 1. This fixed point theorem can be applied to Hammerstein integral equations in a quite natural way.     

QCD on an Infinite Lattice

We construct a mathematically well–defined framework for the kinematics of Hamiltonian QCD on an infinite lattice in ${\mathbb{R}^3}$ , and it is done in a C*-algebraic context. This is based on the finite lattice model for Hamiltonian QCD developed by Kijowski, Rudolph e.a.. To extend this model to an infinite lattice, we need to take an infinite tensor product of nonunital C*-algebras, which is a nonstandard situation. We use a recent construction for such situations, developed by Grundling and Neeb. Once the field C*-algebra is constructed for the fermions and gauge bosons, we define local and global gauge transformations, and identify the Gauss law constraint. The full field algebra is the crossed product of the previous one with the local gauge transformations. The rest of the paper is concerned with enforcing the Gauss law constraint to obtain the C*-algebra of quantum observables. For this, we use the method of enforcing quantum constraints developed by Grundling and Hurst. In particular, the natural inductive limit structure of the field algebra is a central component of the analysis, and the constraint system defined by the Gauss law constraint is a system of local constraints in the sense of Grundling and Lledo. Using the techniques developed in that area, we solve the full constraint system by first solving the finite (local) systems and then combining the results appropriately. We do not consider dynamics.     

The nature of physics

The Doppler shift in frequency of an ionospherically reflected radio wave can be used to study various ionospheric disturbances. In this article the experimental arrangement for measuring such a shift is described, and examples of frequency shifts associated with solar flares, geomagnetic variations and travelling disturbances are discussed.     

Heisenberg’s Uncertainty Relation and Bell Inequalities in High Energy Physics

An effective formalism is developed to handle decaying two-state systems. Herewith, observables of such systems can be described by a single operator in the Heisenberg picture. This allows for using the usual framework in quantum information theory and, hence, to enlighten the quantum features of such systems compared to non-decaying systems. We apply it to systems in high energy physics, i.e. to oscillating meson–antimeson systems. In particular, we discuss the entropic Heisenberg uncertainty relation for observables measured at different times at accelerator facilities including the effect of CP\mathcal{CP} violation, i.e. the imbalance of matter and antimatter. An operator-form of Bell inequalities for systems in high energy physics is presented, i.e. a Bell-witness operator, which allows for simple analysis of unstable systems.     

Space-resolved dynamics of a tracer in a disordered solid

The dynamics of a tracer particle in a glassy matrix of obstacles displays slow complex transport as the free volume approaches a critical value and the void space falls apart. We investigate the emerging subdiffusive motion of the test particle by extensive molecular dynamics simulations and characterize the spatio-temporal transport in terms of two-time correlation functions, including the time-dependent diffusion coefficient, the frequency-dependent conductivity, as well as the wavenumber-dependent intermediate scattering function. We rationalize our findings within the framework of critical phenomena and compare our data to a dynamic scaling theory.     

2H NMR calculations on polynuclear transition metal complexes: on the influence of local symmetry and other factors

It is now well-known that (2)H solid-state NMR techniques can bring a better understanding of the interaction of deuterium with metal atoms in organometallic mononuclear complexes, clusters or nanoparticles. In that context, we have recently obtained experimental quadrupolar coupling constants and asymmetry parameters characteristic of deuterium atoms involved in various bonding situations in ruthenium clusters, namely D(4)Ru(4)(CO)(12), D(2)Ru(6)(CO)(18) and other related compounds [Gutmann et al., J. Am. Chem. Soc., 2010, 132, 11759], which are model compounds for edge-bridging (μ-H) and face-capping (μ(3)-H) coordination types on ruthenium surfaces. The present work is in line with density functional theory (DFT) calculations of the electric field gradient (EFG) tensors in deuterated organometallic ruthenium complexes. The comparison of quadrupolar coupling constants shows an excellent agreement between calculated and observed values. This confirms that DFT is a method of choice for the analysis of deuterium NMR spectra. Such calculations are achieved on a large number of ruthenium clusters in order to obtain quadrupolar coupling constants characteristic of a given coordination type: terminal-D, η(2)-D(2), μ-D, μ(3)-D as well as μ(4)-D and μ(6)-D (i.e. interstitial deuterides). Given the dependence of such NMR parameters mainly on local symmetry, these results are expected to remain valid for large assemblies of ruthenium atoms, such as organometallic ruthenium nanoparticles.     

A reactive Si4 cage: K(SitBu3)3Si4

KR∗₃Si₄, 2, (R∗ = SitBu₃), formed by the reaction of R∗₄Si₄ with 2 KC₈, is an orange red solid stable at r.t. but decomposes in solution into R∗₄Si₄ and a compound that reacts with excess Me₃SiCl to form (Me₃Si)₄R∗₃ClSi₈. Compound 2 is very sensitive to air and moisture. Its alcoholysis does not stabilize the protonated species HR∗₃Si₄ and ends up in R∗₃Si₃H₃. Compound 2 reacts with 1/2 equivalent ICl to form a violet solid R∗₆Si₈. A 1:1 reaction of 2 with SiBr₄ runs differently to form ditetrahedranyl, R∗₃Si₄-Si₄R∗₃ which is stable at r.t. but transforms into its violet isomer R∗₆Si₈ at higher temperatures. Compound 2 crystallizes as R∗₃Si₄K(18-crown-6) and its crystal structure shows a Si₄-cage with a short Si-K linkage. It opens up at higher temperatures to acquire a unique structure in which a -CH₂-CH₂- group detaches itself from an ether to insert into Si-Si linkage of Si₄-unit to form a bicyclic ring. The residual chain (CH₂)₁₀O₆ closes itself on to a Si atom to form R∗₃Si₃(CH₂-CH₂)Si(C₁₀H₂₀O₆)K(18-C-6).     

Redox-active silica nanoparticles. Part 4. Synthesis, size distribution, and electrochemical adsorption behavior of ferrocene- and (diamine)(diphosphine)-ruthenium(II)-modified Stöber silica colloidal particles

Stöber silica nanoparticles with a diameter of approximately 800 nm are covalently modified by redox-active ferrocene or (diamine)(diphosphine) ruthenium(II) units attached to a spacer. The particles are characterized by NMR spectroscopic and chemical techniques. Two variants of modification by condensation are compared. Besides an estimation of the size and the particle porosity, the agglomeration behavior in solvents of different polarity is investigated. The adsorption of the particles to an electrode surface is followed.