Facility location models are well established in various application areas with more than a century of history in academia. Since the 1970s the trend has been shifting from manufacturing to service industries. Due to their nature, service industries are frequently located in or near urban areas which results in additional assumptions, objectives and constraints other than those in more traditional manufacturing location models. This survey focuses on the location of service facilities in urban areas. We studied 110 research papers across different journals and disciplines. We have analyzed these papers on two levels. On the first, we take an Operations Research perspective to investigate the papers in terms of types of decisions, location space, main assumptions, input parameters, objective functions and constraints. On the second level, we compare and contrast the papers in each of these applications categories: a) Waste management systems (WMS), b) Large-scale disaster (LSD), c) Small-scale emergency (SSE), d) General service and infrastructure (GSI), e) Non-emergency healthcare systems (NEH) and f) Transportation systems and their infrastructure (TSI). Each of these categories is critically analyzed in terms of application, assumptions, decision variables, input parameters, constraints, objective functions and solution techniques. Gaps, research opportunities and trends are identified within each category. Finally, some general lessons learned based on the practicality of the models is synthesized to suggest avenues of future research.

Hawthorn extract has been used for ameliorating cardiac disorders and pulmonary hypertension. Flavonoids and oligomeric proanthocyanidins are considered to be responsible for the positive health effects of hawthorn extract. The effect of Hawthorn extract in the water supply on feed intake, growth, carcass traits, internal organ weight, cardiac indices, the concentration of serum proteins and the incidence of pulmonary hypertension syndrome was evaluated in broiler chickens. At one day-of-age, 225 chickens were assigned to one of three experimental groups where 0, 0.1 and 0.2 ML of hawthorn extract was added per one liter of drinking water. Feed intake, live weight gain and carcass weight increased when hawthorn extract was included in the drinking water at a level of 0.1 and 0.2 ML/L (p<0.05). Compared to no extract, the addition of Hawthorn extract in the drinking water (p<0.05) reduced the proportion of the body attributed to abdominal fat, liver and heart (p<0.05), and decreased the percentage of birds that died or showed clinical symptoms of pulmonary hypertension syndrome (p<0.05). Serum protein concentration was (p<0.05) higher in chickens that received the hawthorn extract in the drinking water compared to no addition of extract in the drinking water. Hawthorn extract has shown potential for use as a herbal medicine to aid in the prevention of physiological cardiac disorders and pulmonary hypertension in chickens.

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