Pair Creation in the Pulsar Magnetosphere

We present numerical simulations of the electron-positron plasma creation process in a simple neutron star magnetosphere. We have developed a set of cascade `kernels', which represent the endpoint of the pair cascades resulting from monoenergetic photon seeds. We explore two popular models by convolving these kernels with the seed photon distributions produced by curvature radiation and by inverse Compton scattering. We find that the pair plasma in either case is well-described in its rest frame by a relativistic Maxwellian distribution with temperature near mc^2/k_B. We present cascade multiplicities and efficiencies for a range of seed particle energies and stellar magnetic fields. We find that the efficiencies and multiplicities of pair creation are often lower than has been assumed in previous work.Comment: 38 pages, including 11 figures and 5 tables. To appear in the Astrophysical Journal. Uses the aastex macro

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

Cognitive Neuropsychology of HIV-Associated Neurocognitive Disorders

Advances in the treatment of the human immunodeficiency virus (HIV) have dramatically improved survival rates over the past 10 years, but HIV-associated neurocognitive disorders (HAND) remain highly prevalent and continue to represent a significant public health problem. This review provides an update on the nature, extent, and diagnosis of HAND. Particular emphasis is placed on critically evaluating research within the realm of cognitive neuropsychology that aims to elucidate the component processes of HAND across the domains of executive functions, motor skills, speeded information processing, episodic memory, attention/working memory, language, and visuoperception. In addition to clarifying the cognitive mechanisms of HAND (e.g., impaired cognitive control), the cognitive neuropsychology approach may enhance the ecological validity of neuroAIDS research and inform the development of much needed novel, targeted cognitive and behavioral therapies

Effects of circadian disruption on physiology and pathology: from bench to clinic (and back)

Nested within the hypothalamus, the suprachiasmatic nuclei (SCN) represent a central biological clock that regulates daily and circadian (i.e., close to 24 h) rhythms in mammals. Besides the SCN, a number of peripheral oscillators throughout the body control local rhythms and are usually kept in pace by the central clock. In order to represent an adaptive value, circadian rhythms must be entrained by environmental signals or zeitgebers, the main one being the daily light?dark (LD) cycle. The SCN adopt a stable phase relationship with the LD cycle that, when challenged, results in abrupt or chronic changes in overt rhythms and, in turn, in physiological, behavioral, and metabolic variables. Changes in entrainment, both acute and chronic, may have severe consequences in human performance and pathological outcome. Indeed, animal models of desynchronization have become a useful tool to understand such changes and to evaluate potential treatments in human subjects. Here we review a number of alterations in circadian entrainment, including jet lag, social jet lag (i.e., desynchronization between body rhythms and normal time schedules), shift work, and exposure to nocturnal light, both in human subjects and in laboratory animals. Finally, we focus on the health consequences related to circadian/entrainment disorders and propose a number of approaches for the management of circadian desynchronization.Fil: Chiesa, Juan José. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Duhart, José Manuel. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Casiraghi, Leandro Pablo. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Paladino, Natalia. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bussi, Ivana Leda. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Golombek, Diego Andrés. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

A community-based transcriptomics classification and nomenclature of neocortical cell types

To understand the function of cortical circuits it is necessary to classify their underlying cellular diversity. Traditional attempts based on comparing anatomical or physiological features of neurons and glia, while productive, have not resulted in a unified taxonomy of neural cell types. The recent development of single-cell transcriptomics has enabled, for the first time, systematic high-throughput profiling of large numbers of cortical cells and the generation of datasets that hold the promise of being complete, accurate and permanent. Statistical analyses of these data have revealed the existence of clear clusters, many of which correspond to cell types defined by traditional criteria, and which are conserved across cortical areas and species. To capitalize on these innovations and advance the field, we, the Copenhagen Convention Group, propose the community adopts a transcriptome-based taxonomy of the cell types in the adult mammalian neocortex. This core classification should be ontological, hierarchical and use a standardized nomenclature. It should be configured to flexibly incorporate new data from multiple approaches, developmental stages and a growing number of species, enabling improvement and revision of the classification. This community-based strategy could serve as a common foundation for future detailed analysis and reverse engineering of cortical circuits and serve as an example for cell type classification in other parts of the nervous system and other organs

The role of sleep in pain and fibromyalgia

Fibromyalgia is a common cause of chronic widespread pain, characterized by reduced pressure pain thresholds with hyperalgesia and allodynia. In addition to pain, common symptoms include nonrestorative sleep, fatigue, cognitive dysfunction, stiffness and mood disturbances. The latest research indicates that the dominant pathophysiology in fibromyalgia is abnormal pain processing and central sensitization. Neuroimaging studies have shown that patients with fibromyalgia have similar neural activation to healthy age-matched and gender-matched individuals; however, they have a lower pressure-pain threshold. Polysomnography data has demonstrated that these patients have reduced short-wave sleep and abnormal α-rhythms, suggestive of wakefulness during non-REM (rapid eye movement) sleep. Sleep deprivation in healthy individuals can cause symptoms of fibromyalgia, including myalgia, tenderness and fatigue, suggesting that sleep dysfunction might be not only a consequence of pain, but also pathogenic. Epidemiological studies indicate that poor sleep quality is a risk factor for the development of chronic widespread pain among an otherwise healthy population. Mechanistically, sleep deprivation impairs descending pain-inhibition pathways that are important in controlling and coping with pain. Clinical trials of pharmacological and nonpharmacological therapies have shown that improving sleep quality can reduce pain and fatigue, further supporting the hypothesis that sleep dysfunction is a pathogenic stimulus of fibromyalgi