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LGR's Methane Carbon Isotope Analyzer (MCIA) reports measurements of δ 13 CH 4 and methane concentration (mole fraction) directly, continuously and without sample preparation. LGR offers three models to span the entire range of methane levels in landfills, mudlogging studies, biogas reactors, and ambient air. For measurements of methane concentrations expected in ambient air near landfills and natural gas leaks, LGR's MCIA Range

This work is distributed under the Creative Commons Attribution 4.0 International (CC BY 4.0) license. Contents 1 Introduction and operations 8 Lithology 25 Structural geology 37 Biostratigraphy and paleomagnetism 42 Geochemistry 48 Physical properties 55 Logging 75 References

Various models have been proposed to link partial gas saturation to seismic attenuation and dispersion, suggesting that the reflection coefficient should be frequency-dependent in many cases of practical importance. Previous approaches to studying this phenomenon have typically been limited to single interface models. Here we propose a modelling technique which allows us to incorporate frequency-dependent reflectivity into convolutional modelling. With this modelling framework, seismic data can be synthesized from well logs of velocity, density, porosity and water saturation. This forward modelling could act as a basis for inversion schemes aimed at recovering gas saturation variations with depth. We present a Bayesian inversion scheme for a simple thin layer case and a particular rock physics model, and show that although the method is very sensitive to prior information and constrains, gas saturation and layer thickness can both theoretically be estimated in the case of interfering reflections.

This paper presents the application of weight function method for the calculation of stress intensity factors (K) and T‐stress for surface semi‐elliptical crack in finite thickness plates subjected to arbitrary two‐dimensional stress fields. New general mathematical forms of point load weight functions for K and T have been formulated by taking advantage of the knowledge of a few specific weight functions for two‐dimensional planar cracks available in the literature and certain properties of weight function in general. The existence of the generalised forms of the weight functions simplifies the determination of specific weight functions for specific crack configurations. The determination of a specific weight function is reduced to the determination of the parameters of the generalised weight function expression. These unknown parameters can be determined from reference stress intensity factor and T‐stress solutions. This method is used to derive the weight functions for both K and T for semi‐elliptical surface cracks in finite thickness plates, covering a wide range of crack aspect ratio (a/c) and relative depth (a/t) at any point along the crack front. The derived weight functions are then validated against stress intensity factor and T‐stress solutions for several linear and nonlinear two‐dimensional stress distributions. These derived weight functions are particularly useful for the development of two‐parameter fracture and fatigue models for surface cracks subjected to fluctuating nonlinear stress fields, such as these resulting from surface treatment (shot peening), stress concentration or welding (residual stress).

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