Discrete breathers in nonlinear magnetic metamaterials

Magnetic metamaterials composed of split-ring resonators or U-type elements may exhibit discreteness effects in THz and optical frequencies due to weak coupling. We consider a model one-dimensional metamaterial formed by a discrete array of nonlinear split-ring resonators where each ring interacts with its nearest neighbors. On-site nonlinearity and weak coupling among the individual array elements result in the appearance of discrete breather excitations or intrinsic localized modes, both in the energy-conserved and the dissipative system. We analyze discrete single and multibreather excitations, as well as a special breather configuration forming a magnetization domain wall and investigate their mobility and the magnetic properties their presence induces in the system.     

Thermal denaturing of mutant lysozyme with both the OPLSAA and the CHARMM force fields

Biomolecular simulations enabled by massively parallel supercomputers such as BlueGene/L promise to bridge the gap between the currently accessible simulation time scale and the experimental time scale for many important protein folding processes. In this study, molecular dynamics simulations were carried out for both the wild-type and the mutant hen lysozyme (TRP62GLY) to study the single mutation effect on lysozyme stability and misfolding. Our thermal denaturing simulations at 400-500 K with both the OPLSAA and the CHARMM force fields show that the mutant structure is indeed much less stable than the wild-type, which is consistent with the recent urea denaturing experiment (Dobson et al. Science 2002, 295, 1719-1722; Nature 2003, 424, 783-788). Detailed results also reveal that the single mutation TRP62GLY first induces the loss of native contacts in the beta-domain region of the lysozyme protein at high temperatures, and then the unfolding process spreads into the alpha-domain region through Helix C. Even though the OPLSAA force field in general shows a more stable protein structure than does the CHARMM force field at high temperatures, the two force fields examined here display qualitatively similar results for the misfolding process, indicating that the thermal denaturing of the single mutation is robust and reproducible with various modern force fields.     

Compact domination for groups definable in linear o-minimal structures

We prove the Compact Domination Conjecture for groups definable in linear o-minimal structures. Namely, we show that every definably compact group G definable in a saturated linear o-minimal expansion of an ordered group is compactly dominated by (G/G ⁰⁰, m, π), where m is the Haar measure on G/G ⁰⁰ and π : G → G/G ⁰⁰ is the canonical group homomorphism.     

Hydration and dewetting near fluorinated superhydrophobic plates

The water dynamics near nanoscale fluorinated (CF(3)(CF(2))(7)(CH(2))(2)SiH(3)) monolayers (plates) as well as possible dewetting transitions in-between two such plates have been studied with molecular dynamics simulations in this paper. A "weak water depletion" is found near the single fluorinated surface, with an average water density in the first solvation shells 6-8% lower than its hydrogenated counterpart. The fluorinated molecules are also found to be water impermeable, consistent with experimental findings. More surprisingly, a dewetting transition is found in the interplate region with a critical distance D(c) of 10 A (3-4 water diameters) for double plates with 8 x 8 molecules each (plate size approximately 4 nm x 4 nm). This transition, although occurring on a microscopic length scale, is reminiscent of a first-order phase transition from liquid to vapor. The unusual superhydrophobicity of fluorocarbons is found to be related to their larger size (or surface area) as compared to hydrocarbons, which "dilutes" their physical interactions with water. The water-plate interaction profile shows that the fluorinated carbons have a 10-12% weaker water-plate interaction than their hydrogenated counterparts in the nearest solvation shell, even though the fluorocarbons do have a stronger electrostatic interaction with water due to their larger partial charges. However, the van der Waals interactions dominate the water-plate interaction within the nearest shell, with up to 90% contributions to the total interaction energy, and fluorocarbons have a noticeably weaker (by 10-15%) van der Waals interaction with water in the nearest shell than do hydrocarbons. Both the slightly weaker water-plate interaction and larger surface area contribute to the stronger dewetting transition in the current fluorinated carbon plates.     

An experimental investigation of the performance boundaries of a solar water heating system

This paper presents the performance characteristics of a solar water heating system consisting of a 3 m² flat plate collector and a 68 L tank, from readings taken over a period of 2 years under real weather conditions. It focuses on the characteristics and the behavior of the system, its response to solar radiation and hot water flow rate through the collector under no load conditions and in the evaluation of the errors associated with the system performance measurements. The system behavior proved to be linear with small relative standard deviations (less than 15%) within the values of the calculated errors and also relatively insensitive to solar radiation fluctuations ranging from 800 to 1100 W/m². Flow rate variations from 0.07 and up to 0.25 L/s did not produce any noticeable effects on the energy collected in the storage tank of the system under investigation. The calculated absolute errors in the system instantaneous efficiency ranged from 34% for low flow and up to 20% for the high flows.     

The choice property in tame expansions of o-minimal structures

We establish the choice property, a weak analogue of definable choice, for certain tame expansions of o-minimal structures. Most noteworthily, this property holds for dense pairs of real closed fields, as well as for expansions of o-minimal structures by a dense independent set.     

Measuring performance in analytical measurements

This paper presents the experience from a research which was conducted, within the framework of an EU project, on the various aspects of nutritional micronutrient measurements in foods. The project examined various methods of measuring basic micronutrients in food and water, their effectiveness, their difficulties, their costs as well as other elements. Data from a number of inter-laboratory comparison providers and prepared questionnaires were collated and analyzed, and the data gathered revealed that there are major differences in the methods employed and the instrumentation used. Methods using state of the art equipment such as ICP/MS and GC/MS were used for micronutrient measurements, and the results (successes and failures (z > 2) in the measurements) are presented. The laboratories from which data were gathered were mainly from across Europe (results for more than 700 laboratory determinations are presented), and the failures range from 0 to 67% of the measurement laboratories.     

Radiometric dating of sediment cores from aquatic environments of north-east Mediterranean

Journal of Radioanalytical and Nuclear Chemistry - Chronological records and sedimentation rates of coastal sediment cores from different aquatic environments of NE Mediterranean are reported....     

Coverings by open cells

We prove that in a semi-bounded o-minimal expansion of an ordered group every non-empty open definable set is a finite union of open cells.