166 research outputs found
On the cross correlation between the arrival direction of ultra-high energy cosmic rays, BL Lacertae, and EGRET detections: A new way to identify EGRET sources?
With the aim of testing recent claims for a particularly strong correlation
between ultra-high energy cosmic rays (UHECRs), observed with the AGASA and the
Yakutsk experiments, and a sample of BL Lacertae (BL Lacs), we here conduct a
blind statistical assessment. We search for associations between the same set
of BL Lac objects and the arrival directions of 33 relevant UHECRs observed
with the Haverah Park and the Volcano Ranch experiments. Within the accuracy of
angle determination, there are no positional coincidences. The probability that
this null result arises as a statistical fluctuation from the strongly
correlated case is less than 5%. This implies that the possible correlation
between the arrival directions of UHECRs and BL Lacs is not statistically
sustained. We discuss the impact of our findings on the propose additional
connection among UHECRs, BL Lacs, and EGRET gamma-ray blazars. Recently, such
an association was used as classification technique for EGRET sources. Here we
show that its main underlying hypothesis, i.e., the EGRET angular uncertainty
is twice that quoted in the Third EGRET Catalog, underestimates the goodness of
existing gamma-ray data.Comment: References added. Accepted for publication in Astrophys. J. Let
Infectious disease and health systems modelling for local decision making to control neglected tropical diseases
Most neglected tropical diseases (NTDs) have complex life cycles and are challenging to control. The “2020 goals” of control and elimination as a public health programme for a number of NTDs are the subject of significant international efforts and investments. Beyond 2020 there will be a drive to maintain these gains and to push for true local elimination of transmission. However, these diseases are affected by variations in vectors, human demography, access to water and sanitation, access to interventions and local health systems. We therefore argue that there will be a need to develop local quantitative expertise to support elimination efforts. If available now, quantitative analyses would provide updated estimates of the burden of disease, assist in the design of locally appropriate control programmes, estimate the effectiveness of current interventions and support ‘real-time’ updates to local operations. Such quantitative tools are increasingly available at an international scale for NTDs, but are rarely tailored to local scenarios. Localised expertise not only provides an opportunity for more relevant analyses, but also has a greater chance of developing positive feedback between data collection and analysis by demonstrating the value of data. This is essential as rational program design relies on good quality data collection. It is also likely that if such infrastructure is provided for NTDs there will be an additional impact on the health system more broadly. Locally tailored quantitative analyses can help achieve sustainable and effective control of NTDs, but also underpin the development of local health care systems
Mass drug administration and beyond : how can we strengthen health systems to deliver complex interventions to eliminate neglected tropical diseases?
Achieving the 2020 goals for Neglected Tropical Diseases (NTDs) requires scale-up of Mass Drug Administration (MDA) which will require long-term commitment of national and global financing partners, strengthening national capacity and, at the community level, systems to monitor and evaluate activities and impact.
For some settings and diseases, MDA is not appropriate and alternative interventions are required. Operational research is necessary to identify how existing MDA networks can deliver this more complex range of interventions equitably.
The final stages of the different global programmes to eliminate NTDs require eliminating foci of transmission which are likely to persist in complex and remote rural settings. Operational research is required to identify how current tools and practices might be adapted to locate and eliminate these hard-to-reach foci.
Chronic disabilities caused by NTDs will persist after transmission of pathogens ceases. Development and delivery of sustainable services to reduce the NTD-related disability is an urgent public health priority.
LSTM and its partners are world leaders in developing and delivering interventions to control vector-borne NTDs and malaria, particularly in hard-to-reach settings in Africa. Our experience, partnerships and research capacity allows us to serve as a hub for developing, supporting, monitoring and evaluating global programmes to eliminate NTDs
Stable electroluminescence in ambipolar dopant-free lateral p-n junctions
Dopant-free lateral p-n junctions in the GaAs/AlGaAs material system have
attracted interest due to their potential use in quantum optoelectronics (e.g.,
optical quantum computers or quantum repeaters) and ease of integration with
other components, such as single electron pumps and spin qubits. A major
obstacle to integration has been unwanted charge accumulation at the p-n
junction gap that suppresses light emission, either due to enhanced
non-radiative recombination or inhibition of p-n current. Typically, samples
must frequently be warmed to room temperature to dissipate this built-up charge
and restore light emission in a subsequent cooldown. Here, we introduce a
practical gate voltage protocol that clears this parasitic charge accumulation,
in-situ at low temperature, enabling the indefinite cryogenic operation of
devices. This reset protocol enabled the optical characterization of stable,
bright, dopant-free lateral p-n junctions with electroluminescence linewidths
among the narrowest (< 1 meV; < 0.5 nm) reported in this type of device. It
also enabled the unambiguous identification of the ground state of neutral free
excitons (heavy and light holes), as well as charged excitons (trions). The
free exciton emission energies for both photoluminescence and
electroluminescence are found to be nearly identical (within 0.2 meV or 0.1
nm). The binding and dissociation energies for free and charged excitons are
reported. A free exciton lifetime of 237 ps was measured by time-resolved
electroluminescence, compared to 419 ps with time-resolved photoluminescence.Comment: Main text: 5 pages and 5 figures. Supplementary: 18 pages and 11
figure
Fit for purpose : do we have the right tools to sustain NTD elimination?
Priorities for NTD control programmes will shift over the next 10-20 years as the elimination phase reaches the ‘end game’ for some NTDs, and the recognition that the control of other NTDs is much more problematic. The current goal of scaling up programmes based on preventive chemotherapy (PCT) will alter to sustaining NTD prevention, through sensitive surveillance and rapid response to resurgence. A new suite of tools and approaches will be required for both PCT and Intensive Disease Management (IDM) diseases in this timeframe to enable disease endemic countries to:
1. Sensitively and sustainably survey NTD transmission and prevalence in order to identify and respond quickly to resurgence.
2. Set relevant control targets based not only on epidemiological indicators but also entomological and ecological metrics and use decision support technology to help meet those targets.
3. Implement verified and cost-effective tools to prevent transmission throughout the elimination phase.
Liverpool School of Tropical Medicine (LSTM) and partners propose to evaluate and implement existing tools from other disease systems as well as new tools in the pipeline in order to support endemic country ownership in NTD decision-making during the elimination phase and beyond
Multi-Jet Event Rates in Deep Inelastic Scattering and Determination of the Strong Coupling Constant
Jet event rates in deep inelastic ep scattering at HERA are investigated
applying the modified JADE jet algorithm. The analysis uses data taken with the
H1 detector in 1994 and 1995. The data are corrected for detector and
hadronization effects and then compared with perturbative QCD predictions using
next-to-leading order calculations. The strong coupling constant alpha_S(M_Z^2)
is determined evaluating the jet event rates. Values of alpha_S(Q^2) are
extracted in four different bins of the negative squared momentum
transfer~\qq in the range from 40 GeV2 to 4000 GeV2. A combined fit of the
renormalization group equation to these several alpha_S(Q^2) values results in
alpha_S(M_Z^2) = 0.117+-0.003(stat)+0.009-0.013(syst)+0.006(jet algorithm).Comment: 17 pages, 4 figures, 3 tables, this version to appear in Eur. Phys.
J.; it replaces first posted hep-ex/9807019 which had incorrect figure 4
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
Measurement of Leading Proton and Neutron Production in Deep Inelastic Scattering at HERA
Deep--inelastic scattering events with a leading baryon have been detected by
the H1 experiment at HERA using a forward proton spectrometer and a forward
neutron calorimeter. Semi--inclusive cross sections have been measured in the
kinematic region 2 <= Q^2 <= 50 GeV^2, 6.10^-5 <= x <= 6.10^-3 and baryon p_T
<= MeV, for events with a final state proton with energy 580 <= E' <= 740 GeV,
or a neutron with energy E' >= 160 GeV. The measurements are used to test
production models and factorization hypotheses. A Regge model of leading baryon
production which consists of pion, pomeron and secondary reggeon exchanges
gives an acceptable description of both semi-inclusive cross sections in the
region 0.7 <= E'/E_p <= 0.9, where E_p is the proton beam energy. The leading
neutron data are used to estimate for the first time the structure function of
the pion at small Bjorken--x.Comment: 30 pages, 9 figures, 2 tables, submitted to Eur. Phys.
Fermi Large Area Telescope Constraints on the Gamma-ray Opacity of the Universe
The Extragalactic Background Light (EBL) includes photons with wavelengths
from ultraviolet to infrared, which are effective at attenuating gamma rays
with energy above ~10 GeV during propagation from sources at cosmological
distances. This results in a redshift- and energy-dependent attenuation of the
gamma-ray flux of extragalactic sources such as blazars and Gamma-Ray Bursts
(GRBs). The Large Area Telescope onboard Fermi detects a sample of gamma-ray
blazars with redshift up to z~3, and GRBs with redshift up to z~4.3. Using
photons above 10 GeV collected by Fermi over more than one year of observations
for these sources, we investigate the effect of gamma-ray flux attenuation by
the EBL. We place upper limits on the gamma-ray opacity of the Universe at
various energies and redshifts, and compare this with predictions from
well-known EBL models. We find that an EBL intensity in the optical-ultraviolet
wavelengths as great as predicted by the "baseline" model of Stecker et al.
(2006) can be ruled out with high confidence.Comment: 42 pages, 12 figures, accepted version (24 Aug.2010) for publication
in ApJ; Contact authors: A. Bouvier, A. Chen, S. Raino, S. Razzaque, A.
Reimer, L.C. Reye
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