Electronic Transport in Hybrid Mesoscopic Structures: A Nonequilibrium Green Function Approach

We present a unified transport theory of hybrid structures, in which a confined normal state ($N$) sample is sandwiched between two leads each of which can be either a ferromagnet ($F$) or a superconductor ($S$) via tunnel barriers. By introducing a four-dimensional Nambu-spinor space, a general current formula is derived within the Keldysh nonequilibrium Green function formalism, which can be applied to various kinds of hybrid mesoscopic systems with strong correlations even in the nonequilibrium situation. Such a formula is gauge invariant. We also demonstrate analytically for some quantities, such as the difference between chemical potentials, superconductor order parameter phases and ferromagnetic magnetization orientations, that only their relative value appears explicitly in the current expression. When applied to specific structures, the formula becomes of the Meir-Wingreen-type favoring strong correlation effects, and reduces to the Landauer-B\"uttiker-type in noninteracting systems such as the double-barrier resonant structures, which we study in detail beyond the wide-band approximation.Comment: 24 pages, 12 eps figures, Revtex

Friends' and Adolescents' delinquency. The Moderating Role of Social Status and Reciprocity of Friendships

Contains fulltext : 90384.pdf (publisher's version ) (Closed access)The current study examined the role of friends' delinquency, in terms of violent and property offenses and vandalism. Data were collected from 1,025 adolescents and their best friends in 19 Dutch secondary schools. Concerning violent offenses, cross-sectional analyses showed that adolescents with a high-status friend were more likely to commit violent offenses themselves, whereas adolescents with a low-status friend engaging in vandalism had a greater likelihood of perpetrating vandalism than the adolescents with a high-status friend. The adolescent's violent delinquency and vandalism were positively related to the friend's delinquency only when the friendship was reciprocal. Longitudinally, adolescents with a high-status friend perpetrating vandalism were more likely to engage in vandalism, whereas those with a low-status vandalistic friend showed a decrease. Finally, having a reciprocal friend who committed property offenses increased the adolescent's risk of committing similar offenses, whereas adolescents with a unilateral friend showed a decreased risk over time

Food tourism, niche markets and products in rural tourism: combining the intimacy model and the experience economy as a rural development strategy

The countryside hosts an increasing number of alternative food networks: rural tourists can play an important role in acting as both consumer and \u201ccultural broker\u201d between these networks. This paper provides a theoretical framework for niche marketing food specialties in rural tourism by combining two different consumer behavioural theories, the \u201cexperience economy\u201d and the \u201cintimacy\u201d model, representing a reorientation from classical marketing thinking. It explores the meaning of local food, including the pursuit of reconnection with nature, resilience to globalisation, the role of local food in reinforcing personal identity, the search for freshness, taste and authenticity, support for local producers, and environmental concerns. It considers the challenges for rural entrepreneurs and policy makers in marketing food specialties and rural regions to the post-modern consumer. Using examples derived mostly from secondary literature it identifies seven dimensions that elevate food products to an appealing culinary niche, namely, coherence, anti-capitalistic attitude, struggle against extinction, personal signature, mutual-disclosure, rituals of spatial and physical proximity, and sustainability-related practices. Food providers may use these features to signal food distinctiveness to rural tourists; policy makers can include them in their regional development models to enhance rural tourism without altering historically, socially, and environmentally layered culinary traditions

Looking to happy tomorrows with friends: Best and close friendships as they predict happiness

best friendship, buffering effect, close friendship, companionship, happiness,