1,890 research outputs found

    Prospects for radio detection of ultra-high energy cosmic rays and neutrinos

    Get PDF
    The origin and nature of the highest energy cosmic ray events is currently the subject of intense investigation by giant air shower arrays and fluorescent detectors. These particles reach energies well beyond what can be achieved in ground-based particle accelerators and hence they are fundamental probes for particle physics as well as astrophysics. Because of the scarcity of these high-energy particles, larger and larger ground-based detectors have been built. The new generation of digital radio telescopes may play an important role in this, if properly designed. Radio detection of cosmic ray showers has a long history but was abandoned in the 1970's. Recent experimental developments together with sophisticated air shower simulations incorporating radio emission give a clearer understanding of the relationship between the air shower parameters and the radio signal, and have led to resurgence in its use. Observations of air showers by the SKA could, because of its large collecting area, contribute significantly to measuring the cosmic ray spectrum at the highest energies. Because of the large surface area of the moon, and the expected excellent angular resolution of the SKA, using the SKA to detect radio Cherenkov emission from neutrino-induced cascades in lunar regolith will be potentially the most important technique for investigating cosmic ray origin at energies above the photoproduction cut-off. (abridged)Comment: latex, 26 pages, 17 figures, to appear in: "Science with the Square Kilometer Array," eds. C. Carilli and S. Rawlings, New Astronomy Reviews, (Elsevier: Amsterdam

    Neural responses to facial emotions and subsequent clinical outcomes in difficult-to-treat depression

    Get PDF
    Background: Amygdala and dorsal anterior cingulate cortex responses to facial emotions have shown promise in predicting treatment response in medication-free major depressive disorder (MDD). Here, we examined their role in the pathophysiology of clinical outcomes in more chronic, difficult-to-treat forms of MDD.Methods: Forty-five people with current MDD who had not responded to ≥2 serotonergic antidepressants (n=42, meeting pre-defined fMRI minimum quality thresholds) were enrolled and followed up over four months of standard primary care. Prior to medication review, subliminal facial emotion fMRI was used to extract blood-oxygen level-dependent effects for sad vs. happy faces from two pre-registered a priori defined regions: bilateral amygdala and dorsal/pregenual anterior cingulate cortex. Clinical outcome was the percentage change on the self-reported Quick Inventory of Depressive Symptomatology (16-item).Results: We corroborated our pre-registered hypothesis (NCT04342299) that lower bilateral amygdala activation for sad vs. happy faces predicted favourable clinical outcomes (rs[38]=.40, p=.01). In contrast, there was no effect for dorsal/pregenual anterior cingulate cortex activation (rs[38]=.18, p=.29), nor when using voxel-based whole-brain analyses (voxel-based Family-Wise Error-corrected p<.05). Predictive effects were mainly driven by the right amygdala whose response to happy faces was reduced in patients with higher anxiety levels.Conclusions: We confirmed the prediction that a lower amygdala response to negative vs. positive facial expressions might be an adaptive neural signature, which predicts subsequent symptom improvement also in difficult-to-treat MDD. Anxiety reduced adaptive amygdala responses

    Detecting Radio Emission from Cosmic Ray Air Showers and Neutrinos with a Digital Radio Telescope

    Get PDF
    We discuss the possibilities of measuring ultra-high energy cosmic rays and neutrinos with radio techniques. We review a few of the properties of radio emission from cosmic ray air showers and show how these properties can be explained by coherent ``geosynchrotron'' emission from electron-positron pairs in the shower as they move through the geomagnetic field. This should allow one to use the radio emission as a useful diagnostic tool for cosmic ray research. A new generation of digital telescopes will make it possible to study this radio emission in greater detail. For example, the planned Low-Frequency Array (LOFAR), operating at 10-200 MHz, will be an instrument uniquely suited to study extensive air showers and even detect neutrino-induced showers on the moon. We discuss sensitivities, count rates and possible detection algorithms for LOFAR and a currently funded prototype station LOPES. This should also be applicable to other future digital radio telescopes such as the Square-Kilometer-Array (SKA). LOFAR will be capable of detecting air-shower radio emission from >2*10^14 eV to ~10^20 eV. The technique could be easily extended to include air shower arrays consisting of particle detectors (KASCADE, Auger), thus providing crucial additional information for obtaining energy and chemical composition of cosmic rays. It also has the potential to extend the cosmic ray search well beyond an energy of 10^21 eV if isotropic radio signatures can be found. Other issues that LOFAR can address are to determine the neutral component of the cosmic ray spectrum, possibly look for neutron bursts, and do actual cosmic ray astronomy.Comment: Astropart. Phys., in press, LaTex (elsart.cls included), 29 pages, 4 figures, also available at http://www.mpifr-bonn.mpg.de/staff/hfalcke/publications.html#lofarpape

    The Effect of Fossil Energy and Other Environmental Taxes on Profit Incentives for Change in an Open Economy: Evidence from the UK

    Get PDF
    This paper is in the tradition of those which use input-output techniques to analyse fossil energy and environmental taxes. We put forward the view that, for a country which is open to trade at given world prices and adopts national taxes, the key mechanism for bringing about change in the short term is not through prices and, ultimately, consumer decisions but through profits and producer decisions. This mechanism provides incentives for producers to substitute more environmentally conserving production techniques and to switch productive resources from, say, energy intensive goods to less energy intensive ones. In this respect the paper seeks to deal with a specific set of circumstances which are far from applicable to every economic sector. As such it seeks to complement the existing, more widely applicable literature – to focus on the role of profits as a key short run transmission mechanism by which energy taxes effect changes in producer behaviour. We produce evidence to show that the UK is almost certainly open to trade and unlikely to be able to influence world prices for a range of economic activities. Using this as a working assumption we examine the impact of current environmental taxes in the UK on profitability for a wide range of economic sectors. We then de-compose the overall effect of these environmental taxes on profits into that part attributable to fossil energy taxes and that to other environmental taxes. In general we find fossil energy taxes to be much more significant in their effect on profits and that they introduce significant variations between sectors in the profit incentives to switch productive resources away from energy intensive activities. This paper seeks to address the way in which fossil energy and other environmental taxes provide short run profit incentives to reallocate resources within the domestic economy. It does not address carbon leakage (the transfer of production to other countries which have weaker policies on emissions)

    Early development of non-hodgkin lymphoma following initiation of newer class antiretroviral therapy among HIV-infected patients - implications for immune reconstitution

    Get PDF
    <p>Abstract</p> <p>Background</p> <p>In the HAART era, the incidence of HIV-associated non-Hodgkin lymphoma (NHL) is decreasing. We describe cases of NHL among patients with multi-class antiretroviral resistance diagnosed rapidly after initiating newer-class antiretrovirals, and examine the immunologic and virologic factors associated with potential IRIS-mediated NHL.</p> <p>Methods</p> <p>During December 2006 to January 2008, eligible HIV-infected patients from two affiliated clinics accessed Expanded Access Program antiretrovirals of raltegravir, etravirine, and/or maraviroc with optimized background. A NHL case was defined as a pathologically-confirmed tissue diagnosis in a patient without prior NHL developing symptoms after starting newer-class antiretrovirals. Mean change in CD4 and log<sub>10 </sub>VL in NHL cases compared to controls was analyzed at week 12, a time point at which values were collected among all cases.</p> <p>Results</p> <p>Five cases occurred among 78 patients (mean incidence = 64.1/1000 patient-years). All cases received raltegravir and one received etravirine. Median symptom onset from newer-class antiretroviral initiation was 5 weeks. At baseline, the median CD4 and VL for NHL cases (n = 5) versus controls (n = 73) were 44 vs.117 cells/mm3 (p = 0.09) and 5.2 vs. 4.2 log<sub>10 </sub>(p = 0.06), respectively. The mean increase in CD4 at week 12 in NHL cases compared to controls was 13 (n = 5) vs. 74 (n = 50)(p = 0.284). Mean VL log<sub>10 </sub>reduction in NHL cases versus controls at week 12 was 2.79 (n = 5) vs. 1.94 (n = 50)(p = 0.045).</p> <p>Conclusions</p> <p>An unexpectedly high rate of NHL was detected among treatment-experienced patients achieving a high level of virologic response with newer-class antiretrovirals. We observed trends toward lower baseline CD4 and higher baseline VL in NHL cases, with a significantly greater decline in VL among cases by 12 weeks. HIV-related NHL can occur in the setting of immune reconstitution. Potential immunologic, virologic, and newer-class antiretroviral-specific factors associated with rapid development of NHL warrants further investigation.</p

    Tick-, mosquito-, and rodent-borne parasite sampling designs for the National Ecological Observatory Network

    Get PDF
    Parasites and pathogens are increasingly recognized as significant drivers of ecological and evolutionary change in natural ecosystems. Concurrently, transmission of infectious agents among human, livestock, and wildlife populations represents a growing threat to veterinary and human health. In light of these trends and the scarcity of long-term time series data on infection rates among vectors and reservoirs, the National Ecological Observatory Network (NEON) will collect measurements and samples of a suite of tick-, mosquito-, and rodent-borne parasites through a continental-scale surveillance program. Here, we describe the sampling designs for these efforts, highlighting sampling priorities, field and analytical methods, and the data as well as archived samples to be made available to the research community. Insights generated by this sampling will advance current understanding of and ability to predict changes in infection and disease dynamics in novel, interdisciplinary, and collaborative ways

    A cascade of magmatic events during the assembly and eruption of a super-sized magma body

    Get PDF
    We use comprehensive geochemical and petrological records from whole-rock samples, crystals, matrix glasses and melt inclusions to derive an integrated picture of the generation, accumulation and evacuation of 530 km3 of crystal-poor rhyolite in the 25.4 ka Oruanui supereruption (New Zealand). New data from plagioclase, orthopyroxene, amphibole, quartz, Fe-Ti oxides, matrix glasses, and plagioclase- and quartz-hosted melt inclusions, in samples spanning different phases of the eruption, are integrated with existing data to build a history of the magma system prior to and during eruption. A thermally and compositionally zoned, parental crystal-rich (mush) body was developed during two periods of intensive crystallisation, 70 and 10-15 kyr before the eruption. The mush top was quartz-bearing and as shallow as ~3.5 km deep, and the roots quartz-free and extending to >10 km depth. Less than 600 yr prior to the eruption, extraction of large volumes of ~840 °C low-silica rhyolite melt with some crystal cargo (between 1 and 10%), began from this mush to form a melt-dominant (eruptible) body that eventually extended from 3.5-6 km depth. Crystals from all levels of the mush were entrained into the eruptible magma, as seen in mineral zonation and amphibole model pressures. Rapid translation of crystals from the mush to the eruptible magma is reflected in textural and compositional diversity in crystal cores and melt inclusion compositions, versus uniformity in the outermost rims. Prior to eruption the assembled eruptible magma body was not thermally or compositionally zoned and at temperatures of ~790°C, reflecting rapid cooling from the ~840 °C low-silica rhyolite feedstock magma. A subordinate but significant volume (3-5 km3) of contrasting tholeiitic and calc-alkaline mafic material was co-erupted with the dominant rhyolite. These mafic clasts host crystals with compositions which demonstrate that there was some limited pre-eruptive physical interaction of mafic magmas with the mush and melt-dominant body. However, the mafic magmas do not appear to have triggered the eruption or controlled magmatic temperatures in the erupted rhyolite. Integration of textural and compositional data from all available crystal types, across all dominant and subordinate magmatic components, allows the history of the Oruanui magma body to be reconstructed over a wide range of temporal scales using multiple techniques. This history spans the tens of millennia required to grow the parental magma system (U-Th disequilibrium dating in zircon), through the centuries and decades required to assemble the eruptible magma body (textural and diffusion modelling in orthopyroxene), to the months, days, hours and minutes over which individual phases of the eruption occurred, identified through field observations tied to diffusion modelling in magnetite, olivine, quartz and feldspar. Tectonic processes, rather than 57 any inherent characteristics of the magmatic system, were a principal factor acting to drive the rapid accumulation of magma and control its release episodically during the eruption. This work highlights the richness of information that can be gained by integrating multiple lines of petrologic evidence into a holistic timeline of field-verifiable processes
    corecore