Economic activity in different industries is linked to each other through aggregate income (horizontal linkages) and input-output relationships (vertical linkages). Could such linkages give rise to vicious circles of underdevelopment or virtuous circles of development when there are increasing returns to scale at the firm level? We show that vicious or virtuous circles based on demand linkages ...

in a thousands beds general hospital affiliated to the tehran university, long-standing infestations of insects such as cockroaches, flies, mosquitoes and rat were found as a result of vicious circles and substandard clearing which are due to not well trained and drilled personnel of contracting agency, out of work condition of two incinerators, quasti-administrative aspects of their program on...

The article presents a complex clinical case of drug‑induced erosive esophagitis grade C with the formation Schatzki ring in patient S., 85 years old. A feature under consideration is long‑term persistence both esophageal (dysphagia, odynophagia) and extraesophageal (thoracalgia) complaints, which required an extensive differential diagnosis to rule out cardiac genesis pain syndrome. diagnostic...

Evolutionary biologists and ecologists often focus on equilibrium states that are subject to forms of negative feedback, such as optima for phenotypic traits or regulation of population sizes. However, recent theoretical and empirical studies show how positive feedback can be instrumental in driving many of the most important and spectacular processes in evolutionary ecology, including the evol...

Despite the increasing investment in multi-year federally funded science and technology centers in universities, there are few studies of how these centers engage in learning and change based on information submitted from various agents in the oversight and evaluation process. One challenge is how to manage and respond to this evaluative information, especially when it is conflicting. Although ...