Disorder effects on transport near AFM quantum phase transitions

We discuss three different scenarios recently proposed to account for the non-Fermi liquid behavior near antiferromagnetic (AFM) quantum critical points in heavy-Fermion systems: (i) scattering of Fermi liquid quasiparticles by strong spin fluctuations near the spin-density-wave instability, (ii) the breakdown of the Kondo effect due to the competition with the RKKY interaction, and (iii) the formation of magnetic regions due to rare configurations of the disorder. Here we focus on the first scenario and show that it explains in some detail the anomalous temperature dependence of the resistivity observed, e.g. in CePd₂Si₂, CeNi₂Ge₂ or CeIn₃. The interplay of strongly anisotropic scattering due to critical spin-fluctuations and weak isotropic impurity scattering leads to a regime with a resistivity

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for sufficiently large T and small ρ₀.     

Isothermal Titration Calorimetry of Molecularly Imprinted Polymer Nanospheres

Ultrasensitive isothermal titration calorimetry was used to generate thermodynamic data to assess the binding properties of molecularly imprinted polymer microgels. Microgels were imprinted using L ‐boc‐phenylalanine anilide (L ‐BFA) and then utilized in binding experiments with a variety of probe molecules, structurally closely related to the template molecule. Significant differences were observed between the binding enthalpy of the original template L ‐BFA and those of D ‐BFA, L ‐boc‐phenylalanine, L ‐boc‐tryptophane, and L ‐boc‐tyrosine.     

Ligand‐Dependent Diastereoselectivity in the Palladium‐Catalyzed Copolymerization of Styrene with Carbon Monoxide

[(LL′)Pd(H₂O)](OTf)₂ complexes, in which LL′ is a chelate ligand containing the chiral 4‐benzyl‐4,5‐dihydrooxazole moiety and either pyridin‐2‐yl or 2‐(diphenylphosphino)phenyl substituents, catalyze the copolymerization of styrene with carbon monoxide with an isotactic or prevailingly syndiotactic microstructure, respectively. The chiroptical properties of the copolymers and model studies for carbon monoxide and olefin insertion on related Pd complexes suggest that the reason for the different stereochemistry of the copolymers is a site‐selective coordination of the olefin in the intermediates containing the PN ligand; a lower regioselectivity in the coordination and a different coordination site lead to the different diastereoselectivity for the copolymer formation by the complex containing the NN′‐ligand.     

Umsetzungen von Cp*NbCl4 und Cp*TaCl4 mit Trimethylsilyl‐azid,Me3Si‐N3. Molekülstrukturen der bis(azido)‐oxo‐verbrückten Komplexe [Cp*NbCl(N3)(μ‐N3)]2(μ‐O) und [Cp*TaCl2(μ‐N3)]2(μ‐O) (Cp* = Pentamethylcyclopentadienyl)

Reactions of Cp*NbCl₄ and Cp*TaCl₄ with Trimethylsilyl‐azide, Me₃Si‐N₃. Molecular Structures of the Bis(azido)‐Oxo‐Bridged Complexes [Cp*NbCl(N₃)(μ‐N₃)]₂(μ‐O) and [Cp*TaCl₂(μ‐N₃)]₂(μ‐O) (Cp* = Pentamethylcyclopentadienyl) The chloro ligands in Cp*TaCl₄ (1c) can be stepwise substituted for azido ligands by reactions with trimethylsilyl azide, Me₃Si‐N₃ (A) , to generate the complete series of the bis(azido)‐bridged dimers [Cp*TaCl_3‐n(N₃)_n(μ‐N₃)]₂ ( n = 0 (2c) , n = 1 (3c) , n = 2 (4c) and n = 3 (5c) ). If the solvent CH₂Cl₂ contains traces of water, an additional oxo bridge is incorporated to give [Cp*‐TaCl₂(μ‐N₃)]₂(μ‐O) (6c) or [Cp*TaCl(N₃)(μ‐N₃)]₂(μ‐O) (7c) , respectively. Both 6c and 7c are also formed in stoichiometric reactions from [Cp*TaCl₂(μ‐OH)]₂(μ‐O) (8c) and A . Analogous reactions of Cp*NbCl₄ (1b) with A were used to prepare the azide‐rich dinuclear products [Cp*NbCl_3‐n(N₃)_n(μ‐N₃)]₂ (n = 2 (4b) , and n = 3 (5b) ), and [Cp*NbCl(N₃)(μ‐N₃)]₂(μ‐O) (7b) . The mononuclear complex Cp*Ta(N₃)Me₃ (10c) is obtained from Cp*Ta(Cl)Me₃ and A . All azido complexes were characterised by their IR as well as their ¹H and ¹³C NMR spectra; X‐ray crystal structure analyses are available for 6c and 7b .     

Ladungstransfer durch die DNA: Vom Mechanismus zur Anwendung

DNA charge transfer chemistry has been subject of considerable interest with consequences in the formation of oxidative damage to the DNA which can result in mutagenesis or carcinogenesis. In this article, important examples of spectroscopical and biochemical assays are compared and discussed in terms of the effiencies, rates, and mechanisms. Coupled with the demonstration that such charge transfer can be modulated both negatively and positively by DNA‐binding proteins, these observations therefore suggest the intriguing possibility that DNA‐mediated charge transfer chemistry is biological relevant and may play a role in cellular processes. Additionally, charge transfer chemistry plays a growing role in the recent development of DNA chips detecting mutations or lesions of nucleic acids.     

Adjustable low dynamic pumps based on hydrogels

This paper discusses the suitability of hydrogel actuators as drives of automatic pumps for long-term drug release. We demonstrate that such actuators can execute a defined task if several functional units are connected serially. Investigated functions of this pump are the adjustability of the time-delay from the initial operation up to the beginning of the drug release, opening the sterile drug ampoule, and the drug release at a specified timeframe. The described parameters to influence the pump behaviour are satisfying only for realization of continuous working devices. An outlook of the development of programmable pulsate pumps is given.