We show that the traveling salesman problem with a symmetric relaxed Monge matrix as distance matrix is pyramidally solvable and can thus be solved by dynamic programming. Furthermore, we present a polynomial time algorithm that decides whether there exists a renumbering of the cities such that the resulting distance matrix becomes a relaxed Monge matrix.

BACKGROUND The prevalence of allergic rhinitis (AR) has increased worldwide in recent decades. This study was conducted to investigate the prevalence of self-reported AR and profiles of AR-related comorbidities in the adult population of China over time. METHODS This study surveyed residents of 18 major cities in mainland China. Telephone interviews were conducted with study participants afte...

Supermarkets and hypermarkets already dominate the markets of some larger cities, and their continued expansion from major cities into smaller cities is expected to further drive competition in the grocery retail sector. Of the various retail channels, hypermarkets are expected to have the most growth potential in the Chinese market and are benefitting from consumer trends toward convenience an...

Avian influenza virus (AIV) surveillance studies in wild birds are usually conducted in rural areas and nature reserves. Less is known of avian influenza virus prevalence in wild birds located in densely populated urban areas, while these birds are more likely to be in close contact with humans. Influenza virus prevalence was investigated in 6059 wild birds sampled in cities in the Netherlands ...

Istanbul and Bucharest are major European cities that face a continuing threat of large earthquakes. The geological contexts for these two case studies enable us to understand the nature of the threat and to predict more precisely the consequences of future earthquakes, though we remain unable to predict the time of those events with any precision better than multi-decadal. These two cities fac...

Previous studies have shown that Twitter users have biases to tweet from certain locations (locational bias) and during certain hours (temporal bias). We used three years of geo-located Twitter Data to quantify these biases and test our central hypothesis that Twitter users’ biases are consistent across US cities. Our results suggest that temporal and locational bias of Twitter users are incons...

A megacity is usually defined as a metropolitan area with a total population in excess of 10 million people. The number of megacities is increasing worldwide: in 1950 they were 4; in 1980 they were 28, in 2002 they were 39 and by 2015 they will be 59. In most agglomerations and megacities, urban planning and public infrastructure can guide the urban development in order to achieve a proper sust...

This paper examines reports on how care is administered by Family Health Teams (FHT) doctors and nurses in four state capitals. It identifies issues relating to priority actions, routine activities and the association between the professional profile and how selected activities are performed, in an attempt to ascertain how far these approximate to the comprehensive approach to primary health ca...

BACKGROUND The existence of socio-economic inequalities in child mortality is well documented. African cities grow faster than cities in most other regions of the world; and inequalities in African cities are thought to be particularly large. Revealing health-related inequalities is essential in order for governments to be able to act against them. This study aimed to systematically compare ine...