Search for exotic baryons at HERMES

An experimental search for the Θ(1540)- and Λ(1520)-resonance was performed in quasi-real photoproduction on deuterium at the HERMES experiment. While evidence for Θ(1540) was found in the decay channel pK ⁰ _S→pπ ⁺ π ^-, no evidence for the corresponding anti-particle was found. In some models it is expected that the Θ(1540) and the Λ(1520) have similar production mechanisms. The photoproduction cross-sections for the Λ(1520) in the decay channel Λ(1520)→pK ^- and the corresponding anti-particle are determined. The partial photoproduction cross-sections for Λ(1520) and ˉ(1520) are obtained as σ _Λ(1520) = 65.3±8.8(stat)±6.9(syst)nb and σ _ˉ(1520) = 9.8±2.6(stat)±0.9(syst)nb, corresponding to a ratio R _Λ(1520) = σ _ˉ(1520)/σ _Λ(1520) = 0.15±0.05(stat)±0.02(syst).     

Third order residual distribution schemes for the Navier–Stokes equations

We construct a third order multidimensional upwind residual distribution scheme for the system of the Navier–Stokes equations. The underlying approximation is obtained using standard P² Lagrange finite elements. To discretise the inviscid component of the equations, each element is divided in sub-elements over which we compute a high order residual defined as the integral of the inviscid fluxes on the boundary of the sub-element. The residuals are distributed to the nodes of each sub-element in a multi-dimensional upwind way. To obtain a discretisation of the viscous terms consistent with this multi-dimensional upwind approach, we make use of a Petrov–Galerkin analogy. The analogy allows to find a family of test functions which can be used to obtain a weak approximation of the viscous terms. The performance of this high-order method is tested on flows with high and low Reynolds number.     

Single spin asymmetries in charged pion production from semi-inclusive deep inelastic scattering on a transversely polarized 3He Target at Q2 = 1.4-2.7 GeV2

We report the first measurement of target single spin asymmetries in the semi-inclusive (3)He(e,e'π(±))X reaction on a transversely polarized target. The experiment, conducted at Jefferson Lab using a 5.9 GeV electron beam, covers a range of 0.16 < x < 0.35 with 1.4 < Q(2) < 2.7 GeV(2). The Collins and Sivers moments were extracted from the azimuthal angular dependence of the measured asymmetries. The π(±) Collins moments for (3)He are consistent with zero, except for the π(+) moment at x = 0.35, which deviates from zero by 2.3σ. While the π(-) Sivers moments are consistent with zero, the π(+) Sivers moments favor negative values. The neutron results were extracted using the nucleon effective polarization and measured cross section ratios of proton to (3)He, and are largely consistent with the predictions of phenomenological fits and quark model calculations.     

Development and validation of a ultra-high-performance liquid chromatography-UV method for the detection and quantification of erectile dysfunction drugs and some of their analogues found in counterfeit medicines

Pharmaceutical counterfeiting is a permanently growing problem. Control laboratories are constantly analysing counterfeit medicines. In industrialised countries, one of the main counterfeited class of medicines are erectile dysfunction drugs. This paper describes the development and validation of a fast method to detect and quantify the three authorised phosphodiesterase type 5 inhibitors and five analogues. The method is based on the use of a sub-2 microns polar-embedded column with a gradient using acetonitrile as organic modifier and 10 mM ammonium formate buffer (pH 3.5) as aqueous component of the mobile phase. The separation was achieved in less than 4.5 min. The method has also been compared to the registered HPLC method for the assay of Viagra^® which was considered as the reference method. The method is also compatible with on-line coupling mass spectrometry and will significantly reduce analysis times and solvent consumption.