The rapid urbanization in many developing countries over the past half century seems to have been accompanied by excessively high levels of concentration of the urban population in very large cities. Some degree of urban concentration may be desirable initially to reduce interand intraregional infrastructure expenditures. But in a mature system of cities, economic activity is more spread out. S...

The economic crisis cannot conceal the need for transformation of the National Health System. The financial difficulties of healthcare systems whose spending is growing at a faster rate than the economy have been well known for years. The development and diffusion of new technologies, increased use of health services, rising drug costs, inflation of prices, and the inefficiency of the system ex...

it was thought previously that cardiac muscle gap junctions provide low-resistance connections between cells and permit the local-circuit current to flow. some evidences show that myocardial cells may not require low-resistance connections for successful propagation of the action potential (ap). it seems that some other types of mechanisms must be involved in ap propagation. in this article, we...

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this study examines the assumption that plant resistance to herbivory has fitness costs. to assess costs, i used the standard method of determining whether there is a significant negative genetic correlation between the resistance character and damage in the presence of herbivory and with fitness in the absence of herbivory. seeds of five plants from four genotypes of arabidopsis thaliana were ...

BACKGROUND In this study, the dilute maleic acid pretreatment of wheat straw is optimized, using pretreatment time, temperature and maleic acid concentration as design variables. A central composite design was applied to the experimental set up. The response factors used in this study are: (1) glucose benefits from improved enzymatic digestibility of wheat straw solids; (2) xylose benefits from...

the goal of the current study is to determine the optimal level of advertising beyond which advertising expenditure will not be justified by revenues. to achieve the goal first different types of media were rated by experts as to the degree of their importance. then data ware collected by interviewing the managers and reviewing different media resources. the collected data were then analyzed us...

the economic burden of human immunodeficiency virus/acquired immunodeficiency syndrome (hiv/aids) is far greater than its direct medical costs. this study estimated annual indirect costs of the hiv/aids epidemic in islamic republic of iran in 2006-2007 from societal perspective. a patient cost diary in sets of six booklets covering a total of 6 months (from october 2006 and fallowed until march...