54,880 research outputs found
Blunting the Spike: the CV Minimum Period
The standard picture of CV secular evolution predicts a spike in the CV
distribution near the observed short-period cutoff P_0 ~ 78 min, which is not
observed. We show that an intrinsic spread in minimum (`bounce') periods P_b
resulting from a genuine difference in some parameter controlling the evolution
can remove the spike without smearing the sharpness of the cutoff. The most
probable second parameter is different admixtures of magnetic stellar wind
braking (at up to 5 times the GR rate) in a small tail of systems, perhaps
implying that the donor magnetic field strength at formation is a second
parameter specifying CV evolution. We suggest that magnetic braking resumes
below the gap with a wide range, being well below the GR rate in most CVs, but
significantly above it in a small tail.Comment: 5 pages, 4 figures; accepted for publication in MNRA
Talon cusp affecting primary dentition in two siblings: a case report
The term talon cusp refers to a rare developmental dental anomaly characterized by a cusp-like structure projecting from the cingulum area or cement-enamel junction. This condition can occur in the maxillary and mandibular arches of the primary and permanent dentitions. The purpose of this paper is to report on the presence of talon cusps in the primary dentition of two southern Chinese siblings. The 4 years and 2 months old girl had a talon cusp on her maxillary right primary central incisor, while her 2 years and 9 months old brother had bilateral talon cusps on the maxillary primary central incisors. The presence of this rare dental anomaly in two siblings has scarcely been reported in the literature and this may provide further evidence of a hereditary etiology.Article Link:
http://www.rjme.ro/RJME/resources/files/540113211213.pd
Discovery Prospects for NMSSM Higgs Bosons at the High-Energy Large Hadron Collider
We investigate the discovery prospects for NMSSM Higgs bosons during the
13~TeV run of the LHC. While one of the neutral Higgs bosons is demanded to
have a mass around 125~GeV and Standard Model (SM)-like properties, there can
be substantially lighter, nearby or heavier Higgs bosons, that have not been
excluded yet by LEP, Tevatron or the 8~TeV run of the LHC. The challenge
consists in discovering the whole NMSSM Higgs mass spectrum. We present the
rates for production and subsequent decay of the neutral NMSSM Higgs bosons in
the most promising final states and discuss their possible discovery. The
prospects for pinning down the Higgs sector of the Natural NMSSM will be
analysed taking into account alternative search channels. We give a series of
benchmark scenarios compatible with the experimental constraints, that feature
Higgs-to-Higgs decays and entail (exotic) signatures with multi-fermion and/or
multi-photon final states. These decay chains furthermore give access to the
trilinear Higgs self-couplings. We briefly discuss the possibility of
exploiting coupling sum rules in case not all the NMSSM Higgs bosons are
discovered
High Redshift Standard Candles: Predicted Cosmological Constraints
We investigate whether future measurements of high redshift standard candles
(HzSCs) will be a powerful probe of dark energy, when compared to other types
of planned dark energy measurements. Active galactic nuclei and gamma ray
bursts have both been proposed as potential HzSC candidates. Due to their high
luminosity, they can be used to probe unexplored regions in the expansion
history of the universe. Information from these regions can help constrain the
properties of dark energy, and in particular, whether it varies over time.
We consider both linear and piecewise parameterizations of the dark energy
equation of state, , and assess the optimal redshift distribution a
high-redshift standard-candle survey could take to constrain these models.
The more general the form of the dark energy equation of state being
tested, the more useful high-redshift standard candles become. For a linear
parameterization of , HzSCs give only small improvements over planned
supernova and baryon acoustic oscillation measurements; a wide redshift range
with many low redshift points is optimal to constrain this linear model.
However to constrain a general, and thus potentially more informative, form of
, having many HzSCs can significantly improve limits on the nature of
dark energy.Comment: Accepted MNRAS, 27 Pages, 15 figures, matches published versio
Axion-like-particle decay in strong electromagnetic backgrounds
The decay of a massive pseudoscalar, scalar and U(1) boson into an
electron-positron pair in the presence of strong electromagnetic backgrounds is
calculated. Of particular interest is the constant-crossed-field limit,
relevant for experiments that aim to measure high-energy axion-like-particle
conversion into electron-positron pairs in a magnetic field. The total
probability depends on the quantum nonlinearity parameter - a product of field
and lightfront momentum invariants. Depending on the seed particle mass,
different decay regimes are identified. In the below-threshold case, we find
the probability depends on a non-perturbative tunnelling exponent depending on
the quantum parameter and the particle mass. In the above-threshold case, we
find that when the quantum parameter is varied linearly, the probability
oscillates nonlinearly around the spontaneous decay probability. A strong-field
limit is identified in which the threshold is found to disappear. In modelling
the fall-off of a quasi-constant-crossed magnetic field, we calculate
probabilities beyond the constant limit and investigate when the decay
probability can be regarded as locally constant.Comment: 22 pages, 7 figure
Proof of Luck: an Efficient Blockchain Consensus Protocol
In the paper, we present designs for multiple blockchain consensus primitives
and a novel blockchain system, all based on the use of trusted execution
environments (TEEs), such as Intel SGX-enabled CPUs. First, we show how using
TEEs for existing proof of work schemes can make mining equitably distributed
by preventing the use of ASICs. Next, we extend the design with proof of time
and proof of ownership consensus primitives to make mining energy- and
time-efficient. Further improving on these designs, we present a blockchain
using a proof of luck consensus protocol. Our proof of luck blockchain uses a
TEE platform's random number generation to choose a consensus leader, which
offers low-latency transaction validation, deterministic confirmation time,
negligible energy consumption, and equitably distributed mining. Lastly, we
discuss a potential protection against up to a constant number of compromised
TEEs.Comment: SysTEX '16, December 12-16, 2016, Trento, Ital
Pathogen Population Biology Research can Reduce International Threats to Tree Health Posed by Invasive Fungi
Humankind owes much to trees, given their major role in sequestering carbon and providing oxygen, sugars and much of the energy on which ourselves and terrestrial ecosystems depend. Trees and forests are important culturally, economically, environmentally and socially. And yet, despite this, trees throughout the world are currently facing an increasing number of serious challenges. On a global scale, Curtis et al. (2018) report most forest loss is due to commodity driven deforestation through permanent conversion to nonforest land uses including agriculture (e.g. palm oil production), energy production and mining. The other main drivers of global forest loss, that might instead be considered less permanent and associated with subsequent regrowth, include forestry, shifting agriculture and wildfire. Additional threats to forests include those posed by climate change, and invasive biotic agents such as insect pests and pathogens. Most new tree disease outbreaks are due to introduction events, with a potential pathogen introduced from their endemic centres of origin (where they generally cause little or no disease on their plant host due to long-term coevolution) into a new geographic location, in which a naive host has not previously been exposed and can thus be highly susceptible. The incidence of such 'new encounter' diseases is increasing at an unprecedented rate due to globalisation with increased international trade in plants and travel, a scenario potentially exacerbated by a changing climate better suited to establishment of a pathogen once introduced. Identification of the centres of origin of fungal pathogens can be important for several reasons. First, given that the original host-fungus interaction will have typically stabilised over long periods of time, such geographic regions could be useful sources of host genetic resistance. Moreover, the longer time periods involved will have likely resulted in greater genetic diversity accruing in such endemic populations. More diverse pathogen populations have greater evolutionary potential, with increased genetic variation available for response to environmental change. This could enable host tolerance to be overcome, unexpected 'jumps' onto new hosts, increased risk of fungicide resistance, and better adaptability to changing environmental conditions (e.g. temperature). Thus, strategies to reduce introduction of additional genetic variation from source to sink regions can reduce tree health threats. In this article, such introduction events are considered in the context of three devastating tree diseases, namely ash dieback, Dutch Elm Disease (DED) and Dothistroma Needle Blight (DNB, mainly on pine). On all these tree hosts, multiple closely-related fungal species have now been associated with each of these different diseases. Such related species are often morphologically very similar or even indistinguishable by eye, and consequently this can result in taxonomic confusion and species misidentification, leading to delayed diagnosis of the true causal agent of a given disease outbreak. Research into such related species is important as they might pose very different plant health threats that require distinct disease management strategies. These differences might relate to pathogenicity, geographic distribution, host range, effectiveness of host resistance, sensitivity to fungicides, temperature optima, reproductive strategy and so on. Furthermore, when related fungal species come into physical contact with each other after a long period of separation, for instance via an introduction event, various outcomes are possible including: (1) replacement (and possible extinction) of one species by the other; (2) coexistence of the species; or (3) cross-species hybridisation. The remainder of this article focuses, using three major tree disease case histories, on how fundamental research on pathogen biology can provide new insights into the genetic structure of related pathogen populations that can be usefully applied to reduce the threat to tree health posed by invasive fungal species
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