This paper provides an analytic performance evaluation of the bit error rate (BER) of underlay decode-and-forward cognitive networks with best relay selection over Rayleigh multipath fading channels. ...A generalized BER expression valid for arbitrary operational parameters is firstly presented in the form of a single integral, which is then employed for determining the diversity order and coding gain for different best relay selection scenarios. Furthermore, a novel and highly accurate closed-form approximate BER expression is derived for the specific case where relays are located relatively close to each other. The presented results are rather convenient to handle both analytically and numerically, while they are shown to be in good agreement with results from respective computer simulations. In addition, it is shown that as in the case of conventional relaying networks, the behaviour of underlay relaying cognitive networks with best relay selection depends significantly on the number of involved relays.
The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission to Mercury has provided a wealth of new data about energetic particle phenomena. With observations from ...MESSENGER's Energetic Particle Spectrometer, as well as data arising from energetic electrons recorded by the X‐Ray Spectrometer and Gamma‐Ray and Neutron Spectrometer (GRNS) instruments, recent work greatly extends our record of the acceleration, transport, and loss of energetic electrons at Mercury. The combined data sets include measurements from a few keV up to several hundred keV in electron kinetic energy and have permitted relatively good spatial and temporal resolution for many events. We focus here on the detailed nature of energetic electron bursts measured by the GRNS system, and we place these events in the context of solar wind and magnetospheric forcing at Mercury. Our examination of data at high temporal resolution (10 ms) during the period March 2013 through October 2014 supports strongly the view that energetic electrons are accelerated in the near‐tail region of Mercury's magnetosphere and are subsequently “injected” onto closed magnetic field lines on the planetary nightside. The electrons populate the plasma sheet and drift rapidly eastward toward the dawn and prenoon sectors, at times executing multiple complete drifts around the planet to form “quasi‐trapped” populations.
Key Points
Shows where energetic particles are accelerated at Mercury
Demonstrates quasi‐trapping of energetic electrons
Answers decades‐old questions about Mercury substorms
Mesoscale dynamics are a fundamental process in space physics, but fall within an observational gap of current and planned missions. Particularly in the solar wind, measurements at the mesoscales ...(100s RE to a few degrees heliographic longitude at 1 au) are crucial for understanding the connection between the corona and an observer anywhere within the heliosphere. Mesoscale dynamics may also be key to revealing the currently unresolved physics regulating particle acceleration and transport, magnetic field topology, and the causes of variability in the composition and acceleration of solar wind plasma. Studies using single-point observations do not allow for investigations into mesoscale solar wind dynamics and plasma variability, nor do they allow for the exploration of the sub-structuring of large-scale solar wind structures like coronal mass ejections (CMEs), co-rotating/stream interaction regions (CIR/SIRs), and the heliospheric plasma sheet. To address this fundamental gap in our knowledge of the heliosphere at these scales, the Interplanetary Mesoscale Observatory (InterMeso) concept employs a multi-point approach using four identical spacecraft in Earth-trailing orbits near 1 au. Varying drift speeds of the InterMeso spacecraft enable the mission to span a range of mesoscale separations in the solar wind, achieving significant and innovative science return. Simultaneous, longitudinally-separated measurements of structures co-rotating over the spacecraft also allow for disambiguation of spatiotemporal variability, tracking of the evolution of solar wind structures, and determination of how the transport of energetic particles is impacted by these variabilities.
The Energetic Particle Spectrometer (EPS) on the MESSENGER spacecraft, in orbit about Mercury since March 2011, has detected bursts of low‐ and moderate‐energy (tens to hundreds of keV) electrons ...during portions of most orbits. There have been periods when such bursts were observed regularly on every orbit over a span of several weeks, and other periods when electrons were not observed for several days at a time. We have systematically characterized these energetic events on the basis of particle intensity over the 12‐month period since MESSENGER began orbital operations. Now that MESSENGER has sampled most Mercury longitudes and local times, it is evident that the largest burst events were either at high northern latitudes or near local midnight. Lower‐energy events were also seen near the equator but were mostly absent in both the dawn and dusk local time sectors. The high‐latitude and nightside events are similar in particle intensity, spectra, and pitch angle and are interpreted to be the result of acceleration by the same mechanism. Another group of events occurred upstream of Mercury's bow shock. For two examples of this group of upstream events with good pitch angle coverage, the particles were field‐aligned and traveling away from the bow shock. This group of events is interpreted to be similar to upstream events found at Earth during which particles are accelerated at the bow shock and subsequently travel upstream into the solar wind.
Key Points
MESSENGER made definitive measurements of low‐energy electron bursts at Mercury
The largest electron bursts were at high latitudes or local midnight
We found events occurred upstream of Mercury's bow shock
The MESSENGER spacecraft flyby of Mercury on 14 January 2008 provided a new opportunity to study the intrinsic magnetic field of the innermost planet and its interaction with the solar wind. The ...model presented in this paper is based on the solution of the three-dimensional, bi-fluid equations for solar wind protons and electrons in the absence of mass loading. In this study we provide new estimates of Mercury’s intrinsic magnetic field and the solar wind conditions that prevailed at the time of the flyby. We show that the location of the boundary layers and the strength of the magnetic field along the spacecraft trajectory can be reproduced with a solar wind ram pressure
P
sw
=
6.8
nPa and a planetary magnetic dipole having a magnitude of 210
R
M
3
−
nT and an offset of 0.18
R
M to the north of the equator, where
R
M is Mercury’s radius. Analysis of the plasma flow reveals the existence of a stable drift belt around the planet; such a belt can account for the locations of diamagnetic decreases observed by the MESSENGER Magnetometer. Moreover, we determine that the ion impact rate at the northern cusp was four times higher than at the southern cusp, a result that provides a possible explanation for the observed north–south asymmetry in exospheric sodium in the neutral tail.
In this work, we have combined constant-pH molecular dynamics simulations and experiments to provide a quantitative analysis of pH dependent interactions between doxorubicin hydrochloride (DOX) ...cancer therapeutic and faceted nanodiamond (ND) nanoparticle carriers. Our study suggests that when a mixture of faceted ND and DOX is dissolved in a solvent, the pH of this solvent plays a controlling role in the adsorption of DOX molecules on the ND. We find that the binding of DOX molecules on ND occurs only at high pH and requires at least ∼10% of ND surface area to be fully titrated for binding to occur. As such, this study reveals important mechanistic insight underlying an ND-based pH-controlled therapeutic platform.
Background
Although the provision of pediatric emergency and trauma radiology has become increasingly prevalent in North America over the last few years, many hospitals differ in their models of ...providing after-hours coverage.
Objective
To describe the scope of after-hours radiology services provided in children’s hospitals in North America, and the means by which different radiology departments deliver this coverage.
Materials and methods
The Society for Pediatric Radiology Emergency and Trauma Imaging Committee developed a survey that we electronically distributed to a single representative from each of the 79 hospitals represented in the Society of Chiefs of Radiology at Children’s Hospitals (SCORCH).
Results
Completed questionnaires were submitted between Aug. 2, 2017, and Sept. 29, 2017, by 44/79 (56%) SCORCH representatives. Contemporaneous after-hours interpretation of radiographs (81%), ultrasounds (81%), body CT (79%) and neurologic CT (75%) with preliminary or final reports was common. Coverage was accomplished most commonly by a combination of evening and overnight shifts 17/44 (39%). Eleven of 44 (25%) hospitals used a model in which radiologists rotate working blocks of overnight service followed by blocks off service. Only 2/44 (5%) hospitals exclusively provided pager coverage after hours. Attending pediatric radiologists were assigned to the majority of after-hours shifts 110/175 (63%), but radiology trainees provided interpretations independently for varying periods of time at 19/44 (43%) surveyed hospitals. Incentives to work after hours included the option to work remotely, as well as additional income, time off, and academic time.
Conclusion
The model for delivering after-hours pediatric radiology coverage varies. Most hospitals, however, provide contemporaneous interpretations of radiographs, US, body CT and neurologic CT. Most institutions use evening shifts to extend coverage later, with many providing subsequent overnight coverage. Although most shifts are staffed by attending pediatric radiologists, radiology trainees commonly interpret studies independently for varying durations of time after hours.
Background:
Direct oral anticoagulants (DOACs) have strict dosing guidelines, but recent studies indicate that inappropriate dosing is common, particularly in chronic kidney disease (CKD), for which ...it has been reported to be as high as 43%. Since 2011, the Veterans Health Administration (VA) has implemented anticoagulation management programs for DOACs, generally led by pharmacists, which has previously been shown to improve medication adherence.
Objective:
We investigated the prevalence of overdosing and underdosing of DOACs in the VA.
Methods:
Using data from the TREAT-AF cohort study (The Retrospective Evaluation and Assessment of Therapies in AF), we identified VA patients with newly diagnosed atrial fibrillation (AF) and receipt of a DOAC between 2003 and 2015. We classified dosing as correct, overdosed, or underdosed based on the Food and Drug Administration–approved dosing criteria.
Results:
Of 230 762 patients, 5060 received dabigatran (77.3%) or rivaroxaban (22.7%) within 90 days of AF diagnosis (age 69 10 years; CHA2DS2-VASc 1.6 1.4), of which 1312 (25.9%) had CKD based on estimated glomerular filtration rate <60. Overall, 93.6% of patients, 83.2% with CKD, received appropriate DOAC dosing. Incorrect dosing increased with worsening renal function.
Conclusion:
Compared to recent studies of commercial payers and health-care systems, incorrect dosing of DOACs is less common across the VA. Pharmacist-led DOAC management or similar anticoagulation management interventions may reduce the risk of incorrect dosing across health-care systems.
Mariner 10 and MESSENGER spacecraft observations have established that Mercury has an intrinsic magnetic field and magnetosphere. Following the March 2011 insertion of MESSENGER into orbit around ...Mercury, measurements show that ions and electrons with typical energies of about 1–10 keV form an equatorially centered distribution of plasma at 1.4 RM radial distance (where RMis Mercury's radius) around a substantial portion of the planet in local time from morning through night and into the afternoon sector. Coincident with the detection of plasma around Mercury, an observed drop in the total magnetic pressure is attributable to the ion and electron thermal pressure. Additionally, intense waves near the ion cyclotron frequency were observed at the same location as the quasi‐trapped particle population, which are likely a result of anisotropic distributions created by the large loss cone (>30o) at these radial distances.
Key Points
Mercury has a quasi‐trapped particle population
Mercury's quasi‐trapped particle energies are lower than other planets
Particle precipitation plays an important role in exopshere formation at Mercury
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