A new solution to the Anderson-Newns Hamiltonian of chemisorption

A new solution to the Anderson-Newns Hamiltonian of chemisorption is proposed by using the Green-function formalism and an adequate approximation to the adatom self-energy. The method has been checked in simple models. Our results give both the quasi-particle spectrum and the chemisorption energy with a high accuracy better than 99.9%.     

Simultaneous determination of all-trans-retinoic acid, beta-carotene, and vitamin A in galenic preparations by liquid chromatography

The concentrations of vitamin A, beta-carotene, and all-trans-retinoic acid in oral preparations were determined in a single analysis by a method based on isocratic, reversed-phase liquid chromatography (LC). The LC system consisted of a C18 column, a mobile phase of acetonitrile, dichloromethane, methanol, and water and a UV detector set at 330 nm. The linearity ranges were 25-250 ng/mL for trans-retinoic acid and vitamin A, and 100-1,000 ng/mL for beta-carotene. This LC method for the determination of retinoids is simple, precise, and accurate. No extraction procedure is required before the chromatographic analysis; only a suitable dilution is necessary. The method proved to be reliable, fast, and economical. Furthermore, this method is indicative of stability, because it allows for the determination of degradation products such as 13-cis-retinoic acid.     

Effect of uniaxial strain on the Drude weight of graphene

We study the dependence on the strength and orientation of applied uniaxial strain of the Drude weight in the conductivity of graphene. We find a non-monotonic dependence on strain, which may be related to the proximity to several strain-induced electronic topological transitions. Given the relation between the Drude weight and the long-wavelength plasmon frequency, such a strain dependence can be evidenced by infrared spectroscopy measurements.     

A symmetry result for the p-laplacian equation via the moving planes method

Thsi paper is concerned with a positive solution u of the non–homogeneous p–Laplacian equation in an open, bounded, connected subset Ω of Rⁿ with C² boundary. We assume that u verifies overdetermined boundary conditions and we prove that of us has only one critial point Ω thenΩ is a ball and u is radially symmetric; to prove this result we use the moving planes method introduced by J.Serrien. Using the same technique we also prove that the result is stable in the following sense: the boundary of Ω tends to the boundary of a sphere as the diameter of the critical set u tends to 0.     

Resonant plasmonic and vibrational coupling in a tailored nanoantenna for infrared detection

A novel resonant mechanism involving the interference of a broadband plasmon with the narrowband vibration from molecules is presented. With the use of this concept, we demonstrate experimentally the enormous enhancement of the vibrational signals from less than one attomol of molecules on individual gold nanowires, tailored to act as plasmonic nanoantennas in the infrared. By detuning the resonance via a change in the antenna length, a Fano-type behavior of the spectral signal is observed, which is clearly supported by full electrodynamical calculations. This resonant mechanism can be a new paradigm for sensitive infrared identification of molecular groups.     

Continuous glucose monitoring by means of mid-infrared transmission laser spectroscopy in vitro

The continuous surveillance of glucose concentration reduces short-term risks and long-term complications for people with diabetes mellitus, a disorder of glucose metabolism. As a first step towards the continuous monitoring of glucose, reagent-free transmission spectroscopy in the mid-infrared region has been carried out in vitro using a quantum cascade laser and an optical silver halide fiber. A 30 μm gap in the fiber allowed for transmission spectroscopy of aqueous glucose solutions at a wavelength of 9.69 μm, which is specific to a molecular vibration of glucose. A noise-equivalent concentration as low as 4 mg/dL was achieved at an average power of 1.8 mW and an integration time of 50 s. This is among the most precise of glucose measurements using mid-infrared spectroscopy. Even with the very low average laser power of 0.07 mW the sensitivity of previous results (using a fiber optical evanescent field analysis) has been improved upon by almost one order of magnitude. Finally, the impact of potentially interfering substances such as other carbohydrates was analyzed.