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AbstractThe inclusive top quark pair ($$t\bar{t}$$ t t ¯ ) production cross-section $$\sigma _{t\bar{t}}$$ σ t t ¯ has been measured in proton–proton collisions at $$\sqrt{s}=13\,\text {TeV}$$ s = 13 TeV , using 36.1 fb$$^{-1}$$ - 1 of data collected in 2015–2016 by the ATLAS experiment at the LHC. Using events with an opposite-charge $$e\mu $$ e μ pair and b-tagged jets, the cross-section is measured to be: $$\begin{aligned} \sigma _{t\bar{t}} = 826.4 \pm 3.6\,\mathrm {(stat)}\ \pm 11.5\,\mathrm {(syst)}\ \pm 15.7\,\mathrm {(lumi)}\ \pm 1.9\,\mathrm {(beam)}\,\mathrm {pb}, \end{aligned}$$ σ t t ¯ = 826.4 ± 3.6 ( stat ) ± 11.5 ( syst ) ± 15.7 ( lumi ) ± 1.9 ( beam ) pb , where the uncertainties reflect the limited size of the data sample, experimental and theoretical systematic effects, the integrated luminosity, and the LHC beam energy, giving a total uncertainty of 2.4%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. It is used to determine the top quark pole mass via the dependence of the predicted cross-section on $$m_t^{\mathrm{pole}}$$ m t pole , giving $$m_t^{\mathrm{pole}}=173.1^{+2.0}_{-2.1}\,\text {GeV}$$ m t pole = 173 . 1 - 2.1 + 2.0 GeV . It is also combined with measurements at $$\sqrt{s}=7\,\text {TeV}$$ s = 7 TeV and $$\sqrt{s}=8\,\text {TeV}$$ s = 8 TeV to derive ratios and double ratios of $$t\bar{t}$$ t t ¯ and Z cross-sections at different energies. The same event sample is used to measure absolute and normalised differential cross-sections as functions of single-lepton and dilepton kinematic variables, and the results are compared with predictions from various Monte Carlo event generators.

Domestic (household) biogas plants constitute a growing sub-sector of the anaerobic digestion industry worldwide but have received low interest for improvements. The Chinese dome digester (CDD 1), a major type of domestic biogas plants, is a naturally mixed, unheated and low technology reactor mainly used in rural and pre-urban areas for cooking using animal manure. In this study, a multiphase Computational Fluid Dynamics (CFD) model was applied to evaluate an optimized CDD design and outcomes were compared with results of pilot scale experiments. The optimized digester (CDD2) under goes self-agitating cycles created by the pressure variation from the produced biogas with the aid of a baffle at the top of the reactor, whereas the blank (CDD 1) does not self-agitate. The optimized digester has two pressure zones to improve mixing viz. the self-agitation cycles. The optimized digester is characterized by more, stable and improved hydraulic characteristics and mixing.