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Background: Scotland has the shortest life expectancy in Western Europe, driven by high rates of cancer, suicides, alcohol-related causes and drug-related poisonings. These disparities cannot be explained solely by socioeconomic deprivation. Our aim was to investigate whether a syndemic in a socioeconomically deprived area of Glasgow might account for premature mortality among men. Methods: We analysed data from two cross-sectional population surveys: a national sample of 1916 British men and another of 765 men in Glasgow East. The survey included men aged 18–34, and was undertaken in 2011 to study correlates of violence. Questionnaires covered current physical health, psychiatric symptoms, substance misuse, and crime and violence. Syndemic components were identified using confirmatory factor analysis. Associations and synergistic interactions between these variables and health status were estimated using logistic regression. Results: An aggregation of multiple health conditions and health-related behaviours was found in Glasgow East. A syndemic model of joint effects, adducing a four-component latent variable (violence, substance dependence, psychiatric morbidity and a diathesis of biological/behavioural risk) showed synergy between components and explained persistent disparities in poor physical health/chronic health conditions. Effect modification was found between the general syndemic factor and contextual variables at individual and social environmental level according to location. Conclusions: Syndemic effects from synergistic interactions were confirmed between psychiatric morbidity, substance misuse, violence, and biological/behavioural risk for physical health. A hypothetical model was developed to explain how the syndemic leads to potentially life-threatening risks to young men, both currently and as precursors of physical health conditions which may shorten their lives in the future.

This study investigates Al-Mg2Si-Si alloy joints produced via resistance spot welding (RSW) with and without the use of Al-Si interlayers. The joint microstructures produced both with and without Al-Si interlayers consist of three zones: the base material (BM), the heat affected zone (HAZ) and the weld nugget (WN). The WN is oval, and increases in the welding current increase the WN size in both welding methods. The joints produced via RSW with an Al-Si interlayer have larger WNs than those produced without an interlayer under the same welding current conditions. Relationships between the welding current and the WN size are established by Gaussian fitting and Lorentz fitting. A comparison of the two welding approaches shows that a successful weld can be obtained at a low welding current when an Al-Si interlayer is used, whereas a larger welding current is required to obtain the same result without the use of an Al-Si interlayer. The transition layer (interface between the HAZ and the WN) in the joints welded without an interlayer is a single eutectic phase structure; however, in the joints welded with an interlayer, the transition layer generates an equiaxed-columnar crystal zone. The formation of the equiaxed-columnar crystal zone and the change in composition of the WN (according to the results of differential scanning calorimetry tests) improve the tensile-shear loads (TSLs). The equations of the peak TSLs as a function of the welding current and WN size are established by Gaussian fitting. Keywords: Al-Mg2Si-Si alloy, Resistance spot welding, Interlayer, Microstructure, Mechanical properties