Photonic crystal fiber based evanescent-wave sensor for detection of biomolecules in aqueous solutions

We demonstrate highly efficient evanescent-wave detection of fluorophore-labeled biomolecules in aqueous solutions positioned in the air holes of the microstructured part of a photonic crystal fiber. The air-suspended silica structures located between three neighboring air holes in the cladding crystal guide light with a large fraction of the optical field penetrating into the sample even at wavelengths in the visible range. An effective interaction length of several centimeters is obtained when a sample volume of less than 1 microL is used.     

Silylated derivatives of arabinonucleosides

Procedure have been developed which allow for the selective derivatization of arabinonucleosides at the 5′? or 2′? and 5′? or 3′? and 5′? positions.     

Ionization of aqueous dimethylbenzoic acids: Conductance and thermodynamics

Precise conductance measurements are reported for four xylic acids, 2,3-2,5-2,6 and 3,5-dimethylbenzoics. Limiting molar conductances Λ_O and pK _a obtained from a Fuoss type analysis, are reported for each of these acids at five degree intervals covering the range from 0° to 100°C. The Λ_O values for each acid are described by a polynomial in the Celsius temperature. The pK _a were smoothed as a function of the Kelvin temperature T with an equation of the form: $$pK_{\text{a}} = A{\text{ }} + {\text{ }}B/T{\text{ }} + {\text{ }}C{\text{ }}logT{\text{ }} + {\text{ }}DT$$ where the term linear in T was required only for the 2,3-acid. Standard enthalpy, entropy, and heat capacity changes were calculated by suitable differentiation of this equation. Walden products were calculated for the four anions at each of the temperatures and are compared with earlier data for the toluate and the benzoate ions. Those acids with ortho groups undergo a large decrease in enthalpy on ionization and are substantially more acidic than benzoic acid. These effects are especially large for 2,6-dimethylbenzoic acid. A methyl group in the meta position lowers acidity slightly both in m-toluic and in 2,5-dimethylbenzoic acid. However, 2,3-dimethylbenzoic acid is more acidic than o-toluic.     

Conformal field theory interpretation of black hole quasinormal modes

We obtain exact expressions for the quasinormal modes of various spin for the Ba?ados-Teitelboim-Zanelli black hole. These modes determine the relaxation time of black hole perturbations. Exact agreement is found between the quasinormal frequencies and the location of the poles of the retarded correlation function of the corresponding perturbations in the dual conformal field theory. This then provides a new quantitative test of the anti-de Sitter/conformal field theory correspondence.     

An efficient direct approach for computing shortest rectilinear paths among obstacles in a two-layer interconnection model

In this paper, we present a direct approach for routing a shortest rectilinear path between two points among a set of rectilinear obstacles in a two-layer interconnection model that is used for VLSI routing applications. The previously best known direct approach for this problem takes O(nlog²n) time and O(nlogn) space, where n is the total number of obstacle edges. By using integer data structures and an implicit graph representation scheme (i.e., a generalization of the distance table method), we improve the time bound to O(nlog^3/2n) while still maintaining the O(nlogn) space bound. Comparing with the indirect approach for this problem, our algorithm is simpler to implement and is probably faster for a quite large range of input sizes.     

C[triple‐bond]C—H⋯N hydrogen bonding in 3‐methylthio‐4‐propargylthioquinoline

The title compound, C₁₃H₁₁NS₂, contains a C[triple‐bond]C—H?N hydrogen bond to a pyridine‐type N atom, with a C?N distance of 3.305 (4) Å and an H?N distance of 2.28 Å. This is one of the shortest C—H?N hydrogen bonds known.