Thio arsenosugars identified as natural constituents of mussels by liquid chromatography-mass spectrometry

Two novel thio arsenosugars have been identified by liquid chromatography-mass spectrometry as significant arsenic constituents in samples of mussels.     

SU(4) Fermi liquid state and spin filtering in a double quantum dot system

We study a symmetrical double quantum dot (DD) system with strong capacitive interdot coupling using renormalization group methods. The dots are attached to separate leads, and there can be a weak tunneling between them. In the regime where there is a single electron on the DD the low-energy behavior is characterized by an SU(4)-symmetric Fermi liquid theory with entangled spin and charge Kondo correlations and a phase shift pi/4. Application of an external magnetic field gives rise to a large magnetoconductance and a crossover to a purely charge Kondo state in the charge sector with SU(2) symmetry. In a four-lead setup we find perfectly spin-polarized transmission.     

Cellular automata for the spreading of technologies in socio-economic systems

We introduce an agent-based model for the spreading of technological developments in socio-economic systems where the technology is mainly used for the collaboration/interaction of agents. Agents use products of different technologies to collaborate with each other which induce costs proportional to the difference of technological levels. Additional costs arise when technologies of different providers are used. Agents can adopt technologies and providers of their interacting partners in order to reduce their costs leading to microscopic rearrangements of the system. Analytical calculations and computer simulations revealed that starting from a random configuration of different technological levels a complex time evolution emerges where the spreading of advanced technologies and the overall technological progress of the system are determined by the amount of advantages more advanced technologies provide, and by the structure of the social environment of agents. We show that agents tend to form clusters of identical technological level with a power law size distribution. When technological progress arises, the spreading of technologies in the system can be described by extreme order statistics.     

Phases of a polar spin-1 Bose gas in a magnetic field

The two Bose–Einstein condensed phases of a polar spin-1 gas at nonzero magnetizations and temperatures are investigated. The Hugenholtz–Pines theorem is generalized to this system. Crossover to a quantum phase transition is also studied. Results are discussed in a mean field approximation.     

A diagonal measure and a local distance matrix to display relations between objects and variables

Proper permutation of data matrix rows and columns may result in plots showing striking information on the objects and variables under investigation. To control the permutation first, a diagonal matrix measure D was defined expressing the size relations of the matrix elements. D is essentially the absolute norm of a matrix where the matrix elements are weighted by their distance to the matrix diagonal. Changing the order of rows and columns increases or decreases D. Monte Carlo technique was used to achieve maximum D in the case of the object distance matrix or even minimal D in the case of the variable correlation matrix to get similar objects or variables close together. Secondly, a local distance matrix was defined, where an element reflects the distances of neighboring objects in a limited subspace of the variables. Due to the maximization of D in the local distance matrix by row and column changes of the original data matrix, the similar objects were arranged close to each other and simultaneously the variables responsible for their similarity were collected close to the diagonal part defined by these objects. This combination of the diagonal measure and the local distance matrix seems to be an efficient tool in the exploration of hidden similarities of a data matrix. Copyright © 2009 John Wiley & Sons, Ltd.     

Theoretical study of the mechanism of valence tautomerism in cobalt complexes

Valence tautomerism is studied in the [Co(II-HS)(sq)(2)(bpy)]/[Co(III-LS)(sq)(cat)(bpy)] mononuclear cobalt complex by using DFT methods (HS, high spin; LS, low spin; cat, catecholate; sq, semiquinone; bpy, 2,2'-bipyridine). Calculations at the B3LYP* level of theory reproduce well the energy gap between the Co(II-HS) and Co(III-LS) forms giving an energy gap of 4.4 kcal/mol, which is comparable to the experimental value of 8.9 kcal/mol. Potential energy surfaces and crossing seams of the electronic states of the doublet, quartet, and sextet spin states are calculated along minimum energy paths connecting the energy minima corresponding to the different spin states. The calculated minimum energy crossing points (MECPs) are located at 8.8 kcal/mol in the doublet/sextet surfaces, at 10.2 kcal/mol in the doublet/quartet surfaces, and at 8.4 kcal/mol in the quartet/sextet surfaces relative to the doublet ground state. Considering the energy of the three spin states and the crossing points, the one-step relaxation mechanism between the Co(II-HS) and Co(III-LS) forms is the most probable. This research shows that mapping MECPs can be a useful strategy to analyze the potential energy surfaces of systems with complex deformation modes.     

Determination of Immunosuppressive Pharmaceuticals in Whole Blood Following Kidney Transplantation by High-performance Liquid Chromatography–Tandem Mass Spectrometry

Cyclosporine, tacrolimus, sirolimus, and everolimus are commonly used immunosuppressants following organ transplantation. Their monitoring is used to determine the optimal dose for therapeutic effectiveness and minimize toxicity. High-performance liquid chromatographic–tandem mass spectrometry with positive electrospray ionization and multiple reaction monitoring mode was validated for the determination of cyclosporine A, tacrolimus, sirolimus, and everolimus in whole blood. A C18 analytical column was employed with a gradient elution of pH 4.0 aqueous 10?mmol/L ammonium acetate and acetonitrile. For the pretreatment of whole blood, simple protein precipitation was used with methanol:zinc sulfate. The calibration curves were linear from 20.0 to 1000?ng/mL for cyclosporine A, 1.0 to 50?ng/mL for tacrolimus and sirolimus, and 1.0 to 30?ng/mL for everolimus. The intra-assay precision and inter-assay precision were less than 15%. The method provides reliable and reproducible results according to the linearity, precision, accuracy, recovery, and matrix effects. The method has been introduced to routine clinical practice in Slovakia for the determination of immunosuppressants in patients after kidney transplantation.     

Synthesis and Biological Studies of O3-Aryl Galactosides as Galectin Inhibitors

β-Galactose derivatives have recently been reported to selectively inhibit galectin-3, and a library of O3-arylated galactosides with varying substitution patterns was designed to study such inhibitions further. The O3-arylated galactosides were synthesized using diaryliodonium salts under mild and transition metal free conditions, providing the target products in moderate to good yields. An O3-trifluoroethylated galactoside was also synthesized using iodonium salt chemistry. Azido-substituted products were subsequently transformed into the corresponding triazoles. After deprotection, a selection of galactoside derivatives were evaluated for inhibitory potencies against galectins-1, 3, 4 N (N-terminal domain), 4 C (C-terminal domain), 7, 8 N, 8 C, 9 N, and 9 C and one compound with promising affinity and selectivity for both the N- and C-terminal domain of galectin-9 was discovered.     

Uniform Mixed Hypergraphs: The Possible Numbers of Colors

For a mixed hypergraph , where and are set systems over the vertex set X, a coloring is a partition of X into ‘color classes’ such that every meets some class in more than one vertex, and every has a nonempty intersection with at least two classes. The feasible set of , denoted , is the set of integers k such that admits a coloring with precisely k nonempty color classes. It was proved by Jiang et al. [Graphs and Combinatorics 18 (2002), 309–318] that a set S of natural numbers is the feasible set of some mixed hypergraph if and only if either or S is an ‘interval’ for some integer k ≥ 1. In this note we consider r-uniform mixed hypergraphs, i.e. those with |C| = |D| = r for all and all , r ≥ 3. We prove that S is the feasible set of some r-uniform mixed hypergraph with at least one edge if and only if either for some natural number k ≥ r − 1, or S is of the form where S′′ is any (possibly empty) subset of and S′ is either the empty set or {r − 1} or an ‘interval’ {k, k + 1, ..., r − 1} for some k, 2 ≤ k ≤ r − 2. We also prove that all these feasible sets can be obtained under the restriction , i.e. within the class of ‘bi-hypergraphs’. Research supported in part by the Hungarian Scientific Research Fund, OTKA grant T-049613.