Zero-inflated hierarchical models for faecal egg counts to assess anthelmintic efficacy

The prevalence of anthelmintic resistance has increased in recent years, as a result of the extensive use of anthelmintic drugs to reduce the infection of parasitic worms in livestock. In order to detect the resistance, the number of parasite eggs in animal faeces is counted. Typically a subsample of the diluted faeces is examined, and the mean egg counts from both untreated and treated animals are compared. However, the conventional method ignores the variabilities introduced by the counting process and by different infection levels across animals. In addition, there can be extra zero counts, which arise as a result of the unexposed animals in an infected population or animals. In this paper, we propose the zero-inflated Bayesian hierarchical models to estimate the reduction in faecal egg counts. The simulation study compares the Bayesian models with the conventional faecal egg count reduction test and other methods such as bootstrap and quasi-Poisson regression. The results show the Bayesian models are more robust and they perform well in terms of both the bias and the coverage. We further illustrate the advantages of our proposed model using a case study about the anthelmintic resistance in Swedish sheep flocks

Multi-State Analysis of the OCS Ultraviolet Absorption Including Vibrational Structure

The first absorption band of OCS (carbonyl sulfide) is analyzed using potential energy surfaces and transition dipole moment functions of the lowest four singlet and the lowest four triplet states. Excitation of the 21A\u27 state is predominant except at very low photon energies. It is shown that the vibrational structures in the center of the band are due to excitation of the 23A triplet state, whereas the structures at the very low energies are caused by bending excitation in the potential wells of states 21A\u27 and 11A

2.0 å structure of indole-3-glycerol phosphate synthase from the hyperthermophile Sulfolobus solfataricus: possible determinants of protein stability

AbstractBackground: Recent efforts to understand the basis of protein stability have focussed attention on comparative studies of proteins from hyperthermophilic and mesophilic organisms. Most work to date has been on either oligomeric enzymes or monomers comprising more than one domain. Such studies are hampered by the need to distinguish between stabilizing interactions acting between subunits or domains from those acting within domains. In order to simplify the search for determinants of protein stability we have chosen to study the monomeric enzyme indole-3-glycerol phosphate synthase from the hyperthermophilic archaeon Sulfolobus solfataricus (sIGPS), which grows optimally at 90°C.Results The 2.0 å crystal structure of sIGPS was determined and compared with the known 2.0 å structure of the IGPS domain of the bifunctional enzyme from the mesophilic bacterium Escherichia coli (eIGPS). sIGPS and eIGPS have only 30% sequence identity, but share high structural similarity. Both are single-domain (β/α)8 barrel proteins, with one (eIGPS) or two (sIGPS) additional helices inserted before the first β strand. The thermostable sIGPS has many more salt bridges than eIGPS. Several salt bridges crosslink adjacent α helices or participate in triple or quadruple salt-bridge clusters. The number of helix capping, dipole stabilizing and hydrophobic interactions is also increased in sIGPS.Conclusion The higher stability of sIGPS compared with eIGPS seems to be the result of several improved interactions. These include a larger number of salt bridges, stabilization of α helices and strengthening of both polypeptide chain termini and solvent-exposed loops

The Ultraviolet Spectrum of OCS from First Principles: Electronic Transitions, Vibrational Structure and Temperature Dependence

Global three dimensional potential energy surfaces and transition dipole moment functions are calculated for the lowest singlet and triplet states of carbonyl sulfide at the multireference configuration interaction level of theory. The first ultraviolet absorption band is then studied by means of quantum mechanical wave packet propagation. excitation of the repulsive 21A\u27 state gives the main contribution to the cross section. Excitation of the repulsive 11A state is about a factor of 20 weaker at the absorption peak (Eph ≈ 45 000 cm-1) but becomes comparable to the 21A\u27 state absorption with decreasing energy (35 000 cm-1) and eventually exceeds it. Direct excitation of the repulsive triplet states is negligible except at photon energies Eph \u3c 38 000 cm-1. The main structure observed in the cross section is caused by excitation of the bound 23A state, which is nearly degerate with the 2 1A\u27 state in the Franck-Condon region. The structure observed in the low energy tail of the spectrum is caused by excitation of quasi-bound bending vibrational states of the 21A\u27 and 11A electronic states. The absorption cross sections agree well with experimental data and the temperature dependence of the cross section is well reproduced

Photodissociation of N\u3csub\u3e2\u3c/sub\u3eO: Energy Partitioning

The energy partitioning in the UV photodissociation of N2O is investigated by means of quantum mechanical wave packet and classical trajectory calculations using recently calculated potential energy surfaces. Vibrational excitation of N2 is weak at the onset of the absorption spectrum, but becomes stronger with increasing photon energy. Since the NNO equilibrium angles in the ground and the excited state differe by about 70°, the molecule experiences an extraordinarily large torque during fragmentation producing N2in very high rotational states. The vibrational and rotational distributions obtained from the quantum mechanical and the classical calculations agree remarkably well. The shape of the rotational distributions is semi-quantitatively explained by a two-dimensional verision of the reflection principle. The calculated rotational distribution for excitation with λ = 204 nm and the translational energy distribution for 193 nm agree well with experimental results, except for the tails of the experimental distributions corresponding to excitation of the highest rotational states. Inclusion of nonadiabatic transitions from the excited to the ground electronic state at relatively large N2-O separations, studied by trajectory surface hopping, improves the agreement at high j