Simulations of particle acceleration beyond the classical synchrotron burnoff limit in magnetic reconnection: An explanation of the Crab flares

It is generally accepted that astrophysical sources cannot emit synchrotron radiation above 160 MeV in their rest frame. This limit is given by the balance between the accelerating electric force and the radiation reaction force acting on the electrons. The discovery of synchrotron gamma-ray flares in the Crab Nebula, well above this limit, challenges this classical picture of particle acceleration. To overcome this limit, particles must accelerate in a region of high electric field and low magnetic field. This is possible only with a non-ideal magnetohydrodynamic process, like magnetic reconnection. We present the first numerical evidence of particle acceleration beyond the synchrotron burnoff limit, using a set of 2D particle-in-cell simulations of ultra-relativistic pair plasma reconnection. We use a new code, Zeltron, that includes self-consistently the radiation reaction force in the equation of motion of the particles. We demonstrate that the most energetic particles move back and forth across the reconnection layer, following relativistic Speiser orbits. These particles then radiate >160 MeV synchrotron radiation rapidly, within a fraction of a full gyration, after they exit the layer. Our analysis shows that the high-energy synchrotron flux is highly variable in time because of the strong anisotropy and inhomogeneity of the energetic particles. We discover a robust positive correlation between the flux and the cut-off energy of the emitted radiation, mimicking the effect of relativistic Doppler amplification. A strong guide field quenches the emission of >160 MeV synchrotron radiation. Our results are consistent with the observed properties of the Crab flares, supporting the reconnection scenario.Comment: 15 pages, 16 figures, Accepted for publication in The Astrophysical Journa

Metacognition and headache: which Is the role in childhood and adolescence?

Headache, in particular migraine, is one of the most frequent neurological symptoms in children and adolescents and it affects about 60% of children and adolescents all over the world. Headache can affect several areas of child’s functioning, such as school, physical activities, peer, and family relationship. The global and severe burden of this disease requires a multidisciplinary strategy and an effective treatment addressed all of the patient’s needs and based on cutting-edge scientific research. In recent years, research has focused on cognitive factors specifically in functions called metacognitive processes. Metacognition can be defined as the knowledge, beliefs, and cognitive processes involved in monitoring, control, and assessment of cognition. Metacognition seems to be closely related to the ability of theory of mind, the ability to infer, and reason about the mental states of other people in order to predict and explain own behavior. Recent studies found a relationship between metacognitive skills and anxiety, depression, motivation, academic performance, human social interactions, and stress symptoms. This relationship is very interesting for headache treatment, because these factors are the most commonly reported triggers in this disorder and there is a high comorbidity with anxiety and depression in children and adolescents with headache. So, headache and these comorbidities, in particular anxiety and depression, may have in common persistent and maladaptive patterns of thinking which are related to maladaptive metacognitive beliefs. Further research should assess metacognitive processes of children and adolescents with headache in order to increase their ability to control their own cognitive processes and consequently monitor factors which may trigger the attacks

An exploratory study on internet addiction, somatic symptoms and emotional and behavioral functioning in school-aged adolescents

Objective: In the last two decades there has been a significant transformation regarding the use of new technologies. Despite growing acknowledgement concerning the different activities and functions of digital technologies, there remains a lack of understanding on how technology overuse may negatively impact both physical and psychosocial well-being. Although researchers have begun to explore the meaning and implications of excessive Internet use in non-clinical populations of children and adolescents, there is still little consistent knowledge on the topic. This study aimed to extend existing knowledge on the excessive use of the Internet among school-aged adolescents, focusing on its association with recurrent somatic symptoms, depressive risk and behavioral and emotional problems. Method: Two hundred and forty adolescents (51.9% females) aged between 10 and 15, participated in this study. Data was collected using the Children’s Somatization Inventory, the Internet Addiction Test, the Children’s Depression Inventory, the Youth Self Report and the Emotion Regulation Questionnaire. Structural Equation Model analysis was used to analyse the data. Results: Approximately 21.8% of participants reported excessive Internet use based on Young’s criteria. Higher levels of Internet use were associated with somatic and depressive symptoms as well as emotional and behavioral problems. Depressive Symptoms predicted both Internet Addiction (b = 0.304, p < 0.001) and Internalizing (b = 0.542, p <0.001) and Externalizing problems (b = 0.484, p < 0.001). Internet Addiction also significantly predicted both Internalizing (b = 0.162, p = 0.02) and Externalizing problems (b = 0.183, p = 0.02). Finally, Structural Equation Modeling showed that the indirect effect of Depressive Symptoms (via Internet Addiction) on Internalizing or Externalizing problems were significant. Conclusions: Longitudinal studies are needed to confirm these findings and to identify the mechanisms linking Internet use, somatic symptoms and adaptive functioning

Headache and alexithymia in children and adolescents: what Is the connection?

Background: Headache is one of the most common complaints in children and adolescents and comorbidity rates are very high and the major associated diseases are depression, anxiety, atopic disorders, sleep, and behavioral disorders. In recent years, it has been highlighted that difficulties regulating emotions such as alexithymia have also been associated with diagnosis of somatization. Methods: We carried out a mini review analyzing the relation between alexithymia and primary headache (e.g., migraine and tension type headache) in children and adolescents by synthesizing the relevant studies in the literature on PubMed, PsycINFO, and Google Scholar. Search terms were "alexithymia" combined with the "primary headache," "migraine," "tension type headache," "children," and "adolescents." Results: All analyzed studies found higher levels of alexithymia in children and adolescents with headache than control groups but there are different opinions about the relationship between headache and alexithymia. For example, some studies suggest that the association between headache and alexithymia in children may be due to an incomplete development of emotive competency or a general immature cognitive development, instead other studies found a correlation between headache symptoms, insecure attachment, and alexithymia. There seems to be also differences between children with migraine compared to those with tension type headache (TTH). Conclusion: There are some studies on adults suffering from headache or migraine and alexithymia, but there is only a moderate amount of research on pediatric age with different opinions and theories about this relationship. Further studies on children and adolescents are necessary to effectively understand this relationship and to help children to reduce headache and improve emotional consciousness

Don't judge a book by its cover. factitious disorder imposed on children-report on 2 cases

Factitious Disorder Imposed on Another (FDIA), also known as Munchausen Syndrome by Proxy (MSbP) is a very serious form of child abuse. The perpetrator, usually the mother, invents symptoms or causes real ones in order to make her child appear sick. Usually this is due to a maladaptive disorder or to an excessive of attention-seeking on her part. We report here two new cases of FDIA. The first one is a 9-year-old boy with a history of convulsive episodes, reduced verbal production, mild psychomotor disorder and urological problems who underwent several invasive procedures and hospitalizations before a diagnosis of FDIA was made. The second is a 12 year-old girl with headache, abdominal pain, lipothymic episodes, seizures and a gait impairment, who was hospitalized in several hospitals before an FDIA was diagnosed

Hadronic interactions of primary cosmic rays with the FLUKA code

The measured fluxes of secondary particles produced by the interactions of cosmic rays with the astronomical environment represent a powerful tool to infer some properties of primary cosmic rays. In this work we investigate the production of secondary particles in inelastic hadronic interactions between several cosmic rays species of projectiles and different target nuclei of the interstellar medium. The yields of secondary particles have been calculated with the FLUKA simulation package, that provides with very good accuracy the energy distributions of secondary products in a large energy range. An application to the propagation and production of secondaries in the Galaxy is presented.Comment: 8 pages, 4 figures; Contribution to the 34th International Cosmic Ray Conference, July 30 to August 6, The Hague, Netherlands; fixing a typo in the y-axis label of Fig.