The End of the Rainbow: What Can We Say About the Extragalactic Sub-Megahertz Radio Sky?

The Galactic disc is opaque to radio waves from extragalactic sources with frequencies nu less than ~3 MHz. However, radio waves with kHz, Hz, and even lower frequencies may propagate through the intergalactic medium (IGM). I argue that the presence of these waves can be inferred by using the Universe as our detector. I discuss possible sub-MHz sources and set new non-trivial upper limits on the energy density of sub-MHz radio waves in galaxy clusters and the average cosmic background. Limits based on five effects are considered: (1) changes in the expansion of the Universe from the radiation energy density (2) heating of the IGM by free-free absorption; (3) radiation pressure squeezing of IGM clouds by external radio waves; (4) synchrotron heating of electrons in clusters; and (5) Inverse Compton upscattering of sub-MHz radio photons. Any sub-MHz background must have an energy density much smaller than the CMB at frequencies below 1 MHz. The free-free absorption bounds from the Lyman-alpha forest are potentially the strongest, but are highly dependent on the properties of sub-MHz radio scattering in the IGM. I estimate an upper limit of 6 * 10^4 L_sun Mpc^-3 for the emissivity within Lyman-alpha forest clouds in the frequency range 5 - 200 Hz. The sub-MHz energy density in the Coma cluster is constrained to be less than ~10^-15 erg cm^-3. At present, none of the limits is strong enough to rule out a maximal T_b = 10^12 K sub-MHz synchrotron background, but other sources may be constrained with a better knowledge of sub-MHz radio propagation in the IGM.Comment: Accepted by MNRAS, 4 figures, 20 pages

Radiation transport in diffractive media

We consider radiation transport theory applied to non-dispersive but refractive media. This setting is used to discuss Minkowski's and Abraham's electromagnetic momentum, and to derive conservation equations independent of the choice of momentum definition. Using general relativistic kinetic theory, we derive and discuss a radiation gas energy-momentum conservation equation valid in arbitrary curved spacetime with diffractive media.Comment: 10 pages, typos and equation numbers corrected, version to appear in J. Phys. A: Math. Ge

Assessment of α-Synuclein Secretion in Mouse and Human Brain Parenchyma

Genetic, biochemical, and animal model studies strongly suggest a central role for α-synuclein in the pathogenesis of Parkinson's disease. α-synuclein lacks a signal peptide sequence and has thus been considered a cytosolic protein. Recent data has suggested that the protein may be released from cells via a non-classical secretory pathway and may therefore exert paracrine effects in the extracellular environment. However, proof that α-synuclein is actually secreted into the brain extracellular space in vivo has not been obtained. We developed a novel highly sensitive ELISA in conjugation with an in vivo microdialysis technique to measure α-synuclein in brain interstitial fluid. We show for the first time that α-synuclein is readily detected in the interstitial fluid of both α-synuclein transgenic mice and human patients with traumatic brain injury. Our data suggest that α-synuclein is physiologically secreted by neurons in vivo. This interstitial fluid pool of the protein may have a role in the propagation of synuclein pathology and progression of Parkinson's disease

A Frameshift Mutation in Golden Retriever Dogs with Progressive Retinal Atrophy Endorses SLC4A3 as a Candidate Gene for Human Retinal Degenerations

Progressive retinal atrophy (PRA) in dogs, the canine equivalent of retinitis pigmentosa (RP) in humans, is characterised by vision loss due to degeneration of the photoreceptor cells in the retina, eventually leading to complete blindness. It affects more than 100 dog breeds, and is caused by numerous mutations. RP affects 1 in 4000 people in the Western world and 70% of causal mutations remain unknown. Canine diseases are natural models for the study of human diseases and are becoming increasingly useful for the development of therapies in humans. One variant, prcd-PRA, only accounts for a small proportion of PRA cases in the Golden Retriever (GR) breed. Using genome-wide association with 27 cases and 19 controls we identified a novel PRA locus on CFA37 (praw = 1.94×10−10, pgenome = 1.0×10−5), where a 644 kb region was homozygous within cases. A frameshift mutation was identified in a solute carrier anion exchanger gene (SLC4A3) located within this region. This variant was present in 56% of PRA cases and 87% of obligate carriers, and displayed a recessive mode of inheritance with full penetrance within those lineages in which it segregated. Allele frequencies are approximately 4% in the UK, 6% in Sweden and 2% in France, but the variant has not been found in GRs from the US. A large proportion of cases (approximately 44%) remain unexplained, indicating that PRA in this breed is genetically heterogeneous and caused by at least three mutations. SLC4A3 is important for retinal function and has not previously been associated with spontaneously occurring retinal degenerations in any other species, including humans

Effectiveness of Mechanisms and Models of Coordination between Organizations, Agencies and Bodies Providing or Financing Health Services in Humanitarian Crises: A Systematic Review.

BACKGROUND: Effective coordination between organizations, agencies and bodies providing or financing health services in humanitarian crises is required to ensure efficiency of services, avoid duplication, and improve equity. The objective of this review was to assess how, during and after humanitarian crises, different mechanisms and models of coordination between organizations, agencies and bodies providing or financing health services compare in terms of access to health services and health outcomes. METHODS: We registered a protocol for this review in PROSPERO International prospective register of systematic reviews under number PROSPERO2014:CRD42014009267. Eligible studies included randomized and nonrandomized designs, process evaluations and qualitative methods. We electronically searched Medline, PubMed, EMBASE, Cochrane Central Register of Controlled Trials, CINAHL, PsycINFO, and the WHO Global Health Library and websites of relevant organizations. We followed standard systematic review methodology for the selection, data abstraction, and risk of bias assessment. We assessed the quality of evidence using the GRADE approach. RESULTS: Of 14,309 identified citations from databases and organizations' websites, we identified four eligible studies. Two studies used mixed-methods, one used quantitative methods, and one used qualitative methods. The available evidence suggests that information coordination between bodies providing health services in humanitarian crises settings may be effective in improving health systems inputs. There is additional evidence suggesting that management/directive coordination such as the cluster model may improve health system inputs in addition to access to health services. None of the included studies assessed coordination through common representation and framework coordination. The evidence was judged to be of very low quality. CONCLUSION: This systematic review provides evidence of possible effectiveness of information coordination and management/directive coordination between organizations, agencies and bodies providing or financing health services in humanitarian crises. Our findings can inform the research agenda and highlight the need for improving conduct and reporting of research in this field

Organophosphate flame retardants in the environment: source, occurrence, and human exposure

Due to the restrictions on the application of some traditional brominated flame retardants in consumer products, non-halogenated flame retardant, in particular organophosphate triesters (OPEs), have been extensively used and ubiquitously detected in environmental compartments worldwide. The suspected reproductive toxicity, carcinogenicity, and neurotoxicity of OPEs have raised growing concerns. In this chapter, we first reviewed sources of OPEs in different environments (i.e. indoor, outdoor and aquatic environment), including industrial emission and release from household products. The occurrences and levels of OPEs in various environmental matrices were further assessed showing that concentrations outdoor are one to four orders of magnitude lower than in respective indoor matrices. In addition to persistence, there is an evidence of bioaccumulation for several OPEs. Human exposure to OPEs had been estimated via inhalation, dust ingestion, dermal contact with dust, and dietary ingestion. The median exposure to OPEs were two to three orders of magnitude under the health-based reference doses for all the available studies. Finally, some suggestions for future work are provided based on the current research gaps and changes in commercial markets of alternative flame retardants such as OPEs