Thioalkylated tetraethylene glycol: a new ligand for water soluble monolayer protected gold clusters

Ligand-stabilised, water-soluble gold nanoparticles of two different size ranges (2-4 and 5-8 nm) are readily prepared using monohydroxy (1-mercaptoundec-11-yl) tetraethylene glycol as a novel capping agent. These nanoparticles are as stable as alkylthiol-capped monolayer protected clusters (MPCs) and do not aggregate from aqueous solution under a wide range of stringent conditions. It is expected that this new material will be useful for a number of bio-analytical applications.     

Direct determination of selenium in sub-milligram amounts of human sperm nuclei by electrothermal atomic absorption spectrometry

In the sperm nuclei selenium is present only in form of a single selenoenzyme, the sperm nuclei glutathione peroxidase (snGPx), involved in processes to secure the structural stability of the nuclear chromatin. As changes in its expression may affect sperm function, its analysis is of interest in the diagnosis of male infertility. A method has been developed which by removal of the other selenium compounds present in other sperm components and measurement of the concentration of selenium in the purified human sperm nuclei by electrothermal atomic absorption spectrometry (ETAAS) allows the quantitative analysis of this enzyme. As the purification resulted in yields in the range of only 150 μg nuclei/ml semen and the amount of purified nuclei in the sample could only be determined by weighing, the main analytical difficulty arose from the accurate determination of the sample masses. The procedure includes preparation of purified sperm nuclei, measurement of the sample mass and direct selenium analysis in the suspensions of the compact sperm nuclei without prior digestion of the matter, using a palladium matrix modifier, a spectrometer with Zeeman background correction and a graphite atomizer with L'vov platform. The detection limit for the determination of selenium was 8.4 pg. The quality control of the results by means of instrumental neutron activation analysis (INAA) showed the reliability of the selenium determination by ETAAS. The procedure proved to be suitable to analyze selenium and thus snGPx in very small amounts of purified human sperm nuclei.     

Completely positive semidefinite rank

Mathematical Programming - An $$n\times n$$ matrix X is called completely positive semidefinite (cpsd) if there exist $$d\times d$$ Hermitian positive semidefinite matrices $$\{P_i\}_{i=1}^n$$ (for...     

Path Integral Molecular Dynamics of Liquid Water in a Mean-Field Particle Reservoir

We present a simulation scheme for path integral simulation of molecular liquids where a small open region is embedded in a large reservoir of non interacting point-particles. The scheme is based on the latest development of the adaptive resolution technique AdResS and allows for the space-dependent change of molecular resolution from a path integral representation with 120 degrees of freedom to a point particle that does not interact with other molecules and vice versa. The method is applied to liquid water and implies a sizable gain regarding the request of computational resources compared to full path integral simulations. Given the role of water as universal solvent with a specific hydrogen bonding network, the path integral treatment of water molecules is important to describe the quantum effects of hydrogen atoms’ delocalization in space on the hydrogen bonding network. The method presented here implies feasible computational efforts compared to full path integral simulations of liquid water which, on large scales, are often prohibitive.     

Optical transparency in a polymer blend induced by clay nanofillers

The effect of added nanoclays to the morphological characteristics and the macroscopic properties in a blend of isotactic polypropylene (iPP) and poly(ethylene oxide) (PEO) is examined in this study. It is shown that strong interactions between the surfactant used for clay modification and the binary matrix can effectively control the spatial organization of the suspended polymer droplets. It is also shown that the emulsifying efficiency of nanoclays to the polymer blend has a critical effect on the macroscopic properties of the nanocomposites. In this study, we present a unique case in which the incorporation of a small amount of organically modified nanoclay induces a dramatic transformation from an opaque to a transparent system.     

The Bellman functions of dyadic-like maximal operators and related inequalities

For each p>1 we precisely evaluate the main Bellman functions associated with the dyadic maximal operator on and the dyadic Carleson imbedding theorem. Actually, we do that in the more general setting of tree-like maximal operators. These provide refinements of the sharp L^p inequalities for those operators. For this we introduce an effective linearization for such maximal operators on an adequate set of functions.     

A Sharp Lp Inequality for Dyadic A1 Weights in Rn

The exact best possible range of p is determined such that anydyadic A₁ weight w on Rⁿ satisfies a reverse Hölder inequalityfor p, which depends on the dimension n and the correspondingA₁ constant of w. The proof is based on an effective linearizationof the dyadic maximal operator applied to dyadic step functions.2000 Mathematics Subject Classification 42B25.     

Congruences between the coefficients of the Tate curve via formal groups

Let be the Tate curve with canonical differential, . If the characteristic is , then the Hasse invariant, , of the pair should equal one. If , then calculation of leads to a nontrivial separable relation between the coefficients and . If or , Thakur related and via elementary methods and an identity of Ramanujan. Here, we treat uniformly all characteristics via explicit calculation of the formal group law of . Our analysis was motivated by the study of the invariant which is an infinite Witt vector generalizing the Hasse invariant.