Solving Steiner Tree Problems in Graphs with Lagrangian Relaxation

This paper presents an algorithm to obtain near optimal solutions for the Steiner tree problem in graphs. It is based on a Lagrangian relaxation of a multi-commodity flow formulation of the problem. An extension of the subgradient algorithm, the volume algorithm, has been used to obtain lower bounds and to estimate primal solutions. It was possible to solve several difficult instances from the literature to proven optimality without branching. Computational results are reported for problems drawn from the SteinLib library.     

Salmonella Prevalence Alone Is Not a Good Indicator of Poultry Food Safety

Salmonella is a leading cause of foodborne illness (i.e., salmonellosis) outbreaks, which on occasion are attributed to ground turkey. The poultry industry uses Salmonella prevalence as an indicator of food safety. However, Salmonella prevalence is only one of several factors that determine risk of salmonellosis. Consequently, a model for predicting risk of salmonellosis from individual lots of ground turkey as a function of Salmonella prevalence and other risk factors was developed. Data for Salmonella contamination (prevalence, number, and serotype) of ground turkey were collected at meal preparation. Scenario analysis was used to evaluate effects of model variables on risk of salmonellosis. Epidemiological data were used to simulate Salmonella serotype virulence in a dose‐response model that was based on human outbreak and feeding trial data. Salmonella prevalence was 26% (n = 100) per 25 g of ground turkey, whereas Salmonella number ranged from 0 to 1.603 with a median of 0.185 log per 25 g. Risk of salmonellosis (total arbitrary units (AU) per lot) was affected (p ≤ 0.05) by Salmonella prevalence, number, and virulence, by incidence and extent of undercooking, and by food consumption behavior and host resistance but was not (p > 0.05) affected by serving size, serving size distribution, or total bacterial load of ground turkey when all other risk factors were held constant. When other risk factors were not held constant, Salmonella prevalence was not correlated (r = ?0.39; p = 0.21) with risk of salmonellosis. Thus, Salmonella prevalence alone was not a good indicator of poultry food safety because other factors were found to alter risk of salmonellosis. In conclusion, a more holistic approach to poultry food safety, such as the process risk model developed in the present study, is needed to better protect public health from foodborne pathogens like Salmonella.     

Foraging for patchily-distributed leaf miners by the parasitic wasp,Dacnusa sibirica

Summary We studied the rules used by the female parasitoid,Dacnusa sibirica Telenga (Hymenoptera: Braconidae), for deciding when to leave a tomato leaflet on which she is searching for larvae of the leafminer,Liriomyza bryoniae Kalt. (Diptera: Agromyzidae). Females would deposit a marking pheromone on the leaflet and would leave the leaflet when the amount of the pheromone accumulated to the thresholdL, which is proportional to the amount of search effort on the leaflet.L appears to increase with host density since it rises after every encounter with a host (or mine).D. sibirica would employ an area-concentrated search, which is advantageous in foraging for hosts showing a clumped distribution.     

Ideology and social indicators of the quality of life

This paper explores the possibility that social-psychological, evaluative measures of social well-being/quality of life (QOL) perceptions may embody unintended ideological elements. We argue that individual QOL satisfactions are likely caused, in part, by ‘satisfactions’, or conservative orientations, vis-à-vis societal institutions. Four dependent measures of QOL attitudes-overall life satisfaction, service satisfaction, community satisfaction, and powerlessness-are derived from factor analyses and established measurement procedures. Each of these QOL indicators is found to exhibit significant bivariate associations with measures of political-economic ideology. These relationships are somewhat reduced, but persist at statistically significant levels, when socio-demographic background variables are held constant. We then discuss the implications of our results for theory and method in the social indicators field.     

Cancer in older men: A gender-based review

Cancer is a common condition of the older male. Risk factors for developing a malignancy include genetic, environmental and life style features. Cancer epidemiology and prognosis differ depending on the age and gender of the population being studied. In the group of men older than 65 years, the most common malignant tumors are prostate, lung, colon and pancreatic cancer. Treatment options vary depending on the stage of the tumor when it is diagnosed, and the decision for therapeutic versus palliative interventions will depend upon the functional status, comorbidity and personal wishes of the patients.     

Social accountability as social movement outcome: Protests in a Chinese city

ABSTRACT

Social accountability is a concept that has been used much in development studies and democratic theory to study informal ways for civil society to achieve social change and hold governments accountable. Surprisingly, it has been far less used in social movement scholarship and we argue that social accountability, understood as a combination of answerability, legal claim attainment, and sanction, is a useful way to examine social movement outcomes in China. Social accountability directs the focus of research towards the target of protest and not only whether the protest resulted in policy changes or not. Based on field work in 2013–2015, this article examines four cases of social protests in the Chinese city of Hangzhou. In line with previous research we find that when citizen claims accord with government policies and protesters are well-organized, local authorities tend to accommodate the protesters’ claims. However, answerability and sanction do not always follow the same pattern. Answerability can be relatively high also when legal claims are unsuccessful. This means that cases that are commonly seen as unsuccessful protests because the legal demands were not accommodated may still result in partial social accountability. In addition to the presentation of original empirical findings, the study makes a theoretical contribution by linking the two research fields of social movement and social accountability, which will be of interest to a wider scholarly audience.     

The Union Effect on Wages in Chile: A Two‐Stage Approach Using Panel Data

We estimate the union effect on wages in Chile to be between 18 and 24 per cent. We follow a two‐stage procedure that allows us to correct the endogeneity of union status and to separate true from spurious dependence, by exploiting the union history of individuals using panel data. We find evidence of comparative‐advantage sorting in union status, strong true state dependence and a re‐distributional effect of union membership (i.e. wage gains from unionization are larger for lower‐wage earners).