Barn and Pole paradox: revisited

We present two different paradoxes related to the length contraction in special relativity and explain their resolution.Comment: 7 pages, 6 figures. To appear in Physics Education, IOP Scienc

Gravitational slingshot

The slingshot effect is an intriguing phenomenon that has been used effectively by NASA to send spacecraft to outer edges of the solar system. This phenomenon can be satisfactorily explained by Newtonian physics. However, if it is presented as a problem involving four-momentum conservation, the methods of relativistic kinematics easily lead to the conditions necessary for an accelerating as well as a retarding scenario. This problem provides an example that showcases the frequent utility of relativistic methods to analyze problems of Newtonian mechanics

Spreading in Social Systems: Reflections

In this final chapter, we consider the state-of-the-art for spreading in social systems and discuss the future of the field. As part of this reflection, we identify a set of key challenges ahead. The challenges include the following questions: how can we improve the quality, quantity, extent, and accessibility of datasets? How can we extract more information from limited datasets? How can we take individual cognition and decision making processes into account? How can we incorporate other complexity of the real contagion processes? Finally, how can we translate research into positive real-world impact? In the following, we provide more context for each of these open questions.Comment: 7 pages, chapter to appear in "Spreading Dynamics in Social Systems"; Eds. Sune Lehmann and Yong-Yeol Ahn, Springer Natur

Loneliness, social support and cardiovascular reactivity to laboratory stress

Self-reported or explicit loneliness and social support have been inconsistently associated with cardiovascular reactivity (CVR) to stress. The present study aimed to adapt an implicit measure of loneliness, and use it alongside the measures of explicit loneliness and social support, to investigate their correlations with CVR to laboratory stress. Twenty-five female volunteers aged between 18 and 39 years completed self-reported measures of loneliness and social support, and an Implicit Association Test (IAT) of loneliness. The systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) reactivity indices were measured in response to psychosocial stress induced in the laboratory. Functional support indices of social support were significantly correlated with CVR reactivity to stress. Interestingly, implicit, but not explicit, loneliness was significantly correlated with DBP reactivity after one of the stressors. No associations were found between structural support and CVR indices. Results are discussed in terms of validity of implicit versus explicit measures and possible factors that affect physiological outcomes

Social regulation of gene expression in human leukocytes

Analysis of differentially expressed in circulating leukocytes from people who chronically experienced high versus low levels of subjective social isolation (loneliness) revealed over-expression of some anti-inflammatory genes and under-expression of some pro-inflammatory genes

Mechanical exfoliation and layer number identification of single crystal monoclinic CrCl3

After the recent finding that CrI3, displays ferromagnetic order down to its monolayer, extensive studies have followed to pursue new two-dimensional (2D) magnetic materials. In this article, we report on the growth of single crystal CrCl3 in the layered monoclinic phase. The system after mechanical exfoliation exhibits stability in ambient air (the degradation occurs on a time scale at least four orders of magnitude longer than is observed for CrI3). By means of mechanical cleavage and atomic force microscopy (AFM) combined with optical identification, we demonstrate the systematic isolation of single and few layer flakes onto 270 nm and 285 nm SiO2/Si~(100) substrates with lateral size larger than graphene flakes isolated with the same method. The layer number identification has been carried with statistically significant data, quantifying the optical contrast as a function of the number of layers for up to six layers. Layer dependent optical contrast data have been fitted within the Fresnel equation formalism determining the real and imaginary part of the wavelength dependent refractive index of the material. A layer dependent (532 nm) micro-Raman study has been carried out down to two layers with no detectable spectral shifts as a function of the layer number and with respect to the bulk

Will a Good Citizen Actively Support Organizational Change? Investigation of Psychological Processes Underlying Active Change Support

The present study investigated motivational factors of employees active change support (ACS). It also investigated good citizens response to the change by highlighting convergence and divergence of motivational factors between ACS and traditional extra-role behavior. The findings based on 166 staff responses and 346 supervisor assessments in a hospital that recently implemented a sharedgovernance structure suggest that active change support is a result of an active thinking process that involves perception of potential benefit from change but not necessarily the consequence of conventional predictors of extra-role behaviors (i.e., positive attitudes). The findings also suggest that good citizens are not necessarily the supporters of organizational change and that in actuality they confront motivational dilemma especially when they hold high quality relationship with their employer because they are reluctant to challenge the status quo

Screaming 'Black' Murder: Crime Fiction and the Construction of Ethnic Identities

A significant segment of crime fiction is concerned with the representation of ethnic identities and may to some extent be considered paradigmatic of the participation of literary texts in discourses on race and minorities. This article explores constructions of ethnic identities in American, British, and South African crime fiction from the 1920s to the early twenty-first century. In particular, the focus will be on such texts in which the ethno-cultural identity of the detective gives special prominence not only to the ethnic particularity of the fictional character itself and of its environs but frequently also to that of its author. Main texts discussed are Rudolph Fisher’s The Conjure Man Dies (1932), Earl Derr Biggers’ The House Without a Key (1925) and The Black Camel (1929), Walter Mosley’s Devil in a Blue Dress (1990) and Little Scarlet (2004) as well as James McClure’s The Gooseberry Fool (1974) and Patrick Neate’s City of Tiny Lights (2005). It is argued that all of these texts have a distinct subversive potential of which the construction of ethnic identities becomes the main vehicle because these identities are the products and the catalysts of the conflicts negotiated in ethnic crime fiction and correlating to ‘reality’