Introduction Quality control (QC) techniques are used in monitoring and maintenance of the components of an x-ray system. QC of radiology devices plays a significant role in reduction of medication dose and optimization of image quality. This study aimed to conduct QC tests on randomly selected radiology devices, installed in diagnostic imaging departments of Iran. Materials and Methods In tota...

Previous research suggests that social anxiety disorder (SAD) has a specific relationship with impairment in friendship quality; however, potential moderators of this relationship have not been tested. The current study examines whether the specific effect of SAD on friendship quality is stable or varies across gender and ethnicity in a large epidemiological dataset. Results indicate that the u...

2 The reciprocity problem 3 2.1 Quadratic reciprocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2 Cubic reciprocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3 Biquadratic reciprocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.4 Generalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.5 Hilber...

This paper provides evidence about the determinants of trust and reciprocal inclinations, that is, a tendency for people to respond in kind to hostile or kind actions, in a representative setting. We investigate the prevalence of reciprocity in the population, the correlation between trust and positive and negative reciprocal inclinations within person, the individual determinants of reciprocit...

Reciprocity is often invoked to explain cooperation. Reciprocity is cognitively demanding, and both direct and indirect reciprocity require that individuals store information about the propensity of their partners to cooperate. By contrast, generalized reciprocity, wherein individuals help on the condition that they received help previously, only relies on whether an individual received help in...

A distance magic labeling of a graph G = (V, E) of order n is a bijection l : V → {1, 2, . . . , n} with the property that there is a positive integer k (called magic constant) such that w(x) = k for every x ∈ V . If a graph G admits a distance magic labeling, then we say that G is a distance magic graph. In the case of non-regular graph G, the problem of determining whether there is a distance...

Online Social Networking (OSN) services have become among the most popular services on Internet and their growth has led to creation of lots of different applications and protocols. Most of these applications and protocols rely on findings of previous studies which were concentrated on analyzing and modeling of the structure of inferred friendship graph of social networks. However, serious ques...

Why do your friends have more friends than you do? The question may sound offensive. We don’t even know you. How can we assume than you have fewer friends than your friends have on average? Because most people do. This so-called friendship paradox has first been described and studied in [1]. It does seem counterintuitive: If we are talking about the average number of friends of average friends ...