Novel Insights in the faecal egg count reduction test for monitoring drug efficacy against gastrointestinal nematodes of veterinary importance

The faecal egg count reduction test (FECRT) is the method of choice to monitor anthelmintic efficacy against gastro-intestinal nematodes in livestock. Guidelines on how to conduct a FECRT are made available by the World Association for the Advancement of Veterinary Parasitology (WAAVP). Since the publication of these guidelines in the early 1990s, some limitations have been noted, including (i) the ignorance of host-parasite interactions that depend on animal and parasite species, (ii) their feasibility under field conditions, (iii) appropriateness of study design, and (iv) the low analytic sensitivity of the recommended faecal egg count (FEC) method. Therefore, the objective of the present study was to empirically assess the impact of the level of excretion and aggregation of FEC, sample size and detection limit of the FEC method on the sensitivity and specificity of the FECRT to detect reduced efficacy (<90% or <95%) and to develop recommendations for surveys on anthelmintic resistance. A simulation study was performed in which the FECRT (based on the arithmetic mean of grouped FEC of the same animals before and after drug administration) was conducted under varying conditions of mean FEC, aggregation of FEC (inversely correlated with k), sample size, detection limit and ‘true’ drug efficacies. Classification trees were built to explore the impact of the above factors on the sensitivity and specificity of detecting a truly reduced efficacy. For a reduced-efficacy threshold of 90%, most combinations resulted in a reliable detection of reduced and normal efficacy. For the reduced-efficacy threshold of 95% however, unreliable FECRT results were found when sample sizes <15 were combined with highly aggregated FEC (k = 0.25) and detection limits ≥5 EPG or when combined with detection limits ≥15 EPG. Overall, an increase in sample size and mean preDA FEC, and a decrease in detection limit improved the diagnostic accuracy. FECRT remained inconclusive under any evaluated condition for drug efficacies ranging from 87.5% to 92.5% for a reduced-efficacy-threshold of 90% and from 92.5% to 97.5% for a threshold of 95%. The results highlight that (i) the interpretation of this FECRT is affected by a complex interplay of factors, including the level of excretion and aggregation of FEC and (ii) the diagnostic value of FECRT to detect small reductions in efficacy is limited. This study, therefore, provides a framework allowing researchers to adapt their study design according to a wide range of field conditions, while ensuring a good diagnostic performance of the FECRT

First-Principle Description of Correlation Effects in Layered Materials

We present a first-principles description of anisotropic materials characterized by having both weak (dispersion-like) and strong covalent bonds, based on the Adiabatic--Connection Fluctuation--Dissipation Theorem within Density Functional Theory. For hexagonal boron nitride the in-plane and out of plane bonding as well as vibrational dynamics are well described both at equilibrium and when the layers are pulled apart. Also bonding in covalent and ionic solids is described. The formalism allows to ping-down the deficiencies of common exchange-correlation functionals and provides insight towards the inclusion of dispersion interactions into the correlation functional.Comment: Accepted for publication in Physical Review Letter

Insights into the architecture and stoichiometry of Escherichia coli PepA•DNA complexes involved in transcriptional control and site-specific DNA recombination by atomic force microscopy

Multifunctional Aminopeptidase A (PepA) from Escherichia coli is involved in the control of two distinct DNA transaction processes: transcriptional repression of the carAB operon, encoding carbamoyl phosphate synthase and site-specific resolution of ColE1-type plasmid multimers. Both processes require communication at a distance along a DNA molecule and PepA is the major structural component of the nucleoprotein complexes that underlie this communication. Atomic Force Microscopy was used to analyze the architecture of PepA·carAB and PepA·cer site complexes. Contour length measurements, bending angle analyses and volume determinations demonstrate that the carP1 operator is foreshortened by ∼235 bp through wrapping around one PepA hexamer. The highly deformed part of the operator extends from slightly upstream of the –35 hexamer of the carP1 promoter to just downstream of the IHF-binding site, and comprises the binding sites for the PurR and RutR transcriptional regulators. This extreme remodeling of the carP1 control region provides a straightforward explanation for the strict requirement of PepA in the establishment of pyrimidine and purine-specific repression of carAB transcription. We further provide a direct physical proof that PepA is able to synapse two cer sites in direct repeat in a large interwrapped nucleoprotein complex, likely comprising two PepA hexamers

Climate variability of Southern Chile since the Last Glacial Maximum: a continuous sedimentological record from Lago Puyehue (40°S)

A key region to study high resolution climate changes of the Southern Hemisphere is undoubtedly the southern part of Chile because it has the advantage to be far removed from the Northern Hemisphere ice sheets and thermohaline circulation influences. In order to reconstruct the regional climate evolution since the Last Glacial Maximum, we investigated the sedimentary infilling of Lago Puyehue (40°S, 164 km2, elevation 185 m) by a multi-proxy analyse of a 11 m long core. Sediments from this core are transported by interflow currents and are made of finely laminated silts, with only small disturbances due to volcanic and seismic activities. Several proxies were measured: grain-size, mineralogy, magnetic susceptibility, major elements geochemistry and biogenic silica concentration. These are used to reconstruct paleo-precipitation and paleo-productivity changes around 40°S. Results evidence that sediment grainsize is highly correlated with the biogenic sediment content and can be used as a proxy for lake paleoproductivity. On the other hand, the magnetic susceptibility signal is highly correlated with the aluminium and titanium concentrations and can be used as a proxy for the terrigenous supply. Temporal variations of sediment composition demonstrate that, since the Last Glacial Maximum, the Chilean Lake District was characterized by 3 abrupt climate changes superimposed on a long term climate evolution. These rapid climate changes are: (1) the end of the Last Glacial Maximum at 17,300 cal. yr. BP; (2) a 13,100-12,300 cal. yr. BP cold event, ending rapidly and interpreted as the local counter part of the European Younger Dryas event, and (3) a 3400-2900 cal. yr. BP climatic instability related to low solar activity. The timing of the 13,100-12,300 cold event is compared with similar records in both hemispheres and demonstrates that this Southern Hemisphere climate change lags behind the Northern Hemisphere Younger Dryas cold period by 500 to 1000 years

Strontium Stable Isotope Composition of Allende Fine-Grained Inclusions

Isotopic anomalies are departures from the laws of mass-dependent fractionation that cannot be explained by radioactive decay, cosmogenic effects, or exotic isotopic fractionation processes such as nuclear field shift or magnetic effects [1 and references therein]. These anomalies often have a nucleosynthetic origin and provide clues on the stellar origin and solar system processing of presolar dust. Anomalies are most often found in refractory elements of relatively low mass, so Sr is a prime target for study. The four stable isotopes of strontium are useful for discerning the various nucleosynthetic origins of early solar system building blocks and the timing of accretion processes. Strontium-84 is the least abundant (0.56%) of these isotopes, but is particularly significant in being a p-process only nuclide that is produced in core-collapse or type Ia supernovae [2,3]. The more abundant isotopes ^(86)Sr (9.86%), ^(87)Sr (7.00%) and ^(88)Sr (82.58%) are produced in s- and r-processes in asymptotic giant branch stars and other stellar types [4]. Additionally, ^(87)Sr is produced by ^(87)Rb decay in proportions that dominate over possible nucleosynthetic variations but provide timings of early solar system processes, most notably volatile element depletion [5-7]. Furthermore, variations in strontium isotopic ratios caused by high-temperature massdependent fractionation [8] are also important [9-12], as they provide insights into nebular and accretionary processes

Novel insights in the interpretation of the faecal egg count reduction test to monitor anthelmintic efficacy

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Theoretical polarization dependence of the two-phonon double-resonant Raman spectra of graphene

The experimental Raman spectra of graphene exhibit a few intense two-phonon bands, which are enhanced through double-resonant scattering processes. Though there are many theoretical papers on this topic, none of them predicts the spectra within a single model. Here, we present results for the two-phonon Raman spectra of graphene calculated by means of the quantum perturbation theory. The electron and phonon dispersions, electronic lifetime, electron-photon and electron-phonon matrix elements, are all obtained within a density-functional-theory-based non-orthogonal tight-binding model. We study systematically the overtone and combination two-phonon Raman bands, and, in particular, the energy and polarization dependence of their Raman shift and intensity. We find that the ratio of the integrated intensities for parallel and cross polarized light for all two-phonon bands is between 0.33 and 0.42. Our results are in good agreement with the available experimental data