8,110 research outputs found
GOES observations of solar protons during ground level enhancements
Since 1974, the U.S. National Oceanic and Atmospheric Administration (NOAA) has observed solar proton fluxes from the Geostationary Operational Environmental Satellites (GOES). These observations frequently have served as measurements of the primary component of ground level enhancements (GLEs). Until March 2020, when GOES-14 and -15 were turned off, solar proton measurements were made by the Energetic Particle Sensor (EPS) and the High-Energy Proton and Alpha Detector (HEPAD). EPS had poor energy resolution above 100 MeV, and NOAA derived a >100 MeV integral flux from the EPS channels to support alerts issued by the Space Weather Forecast Office. HEPAD provided some energy resolution in the 330-700 MeV range and a >700 MeV integral channel. Starting with GOES-16, a new instrument called the Solar and Galactic Proton Sensor (SGPS) has replaced EPS and HEPAD. SGPS uses three solid-state telescopes to observe solar proton fluxes between 1 and 500 MeV with a >500 MeV integral channel. The >100 MeV integral flux is now derived from SGPS observations and includes the >500 MeV flux in its derivation. In this paper, we describe the older EPS and HEPAD observations and the new SGPS solar proton observations. We also compare methods for detecting solar proton event onsets currently used with GOES and neutron monitor observations and recommend some innovations
Statistical Estimation of Quantum Tomography Protocols Quality
A novel operational method for estimating the efficiency of quantum state
tomography protocols is suggested. It is based on a-priori estimation of the
quality of an arbitrary protocol by means of universal asymptotic fidelity
distribution and condition number, which takes minimal value for better
protocol. We prove the adequacy of the method both with numerical modeling and
through the experimental realization of several practically important protocols
of quantum state tomography
Controlling Hydrocarbon (De)Hydrogenation Pathways with Bifunctional PtCu Single-Atom Alloys
The conversions of surface-bound alkyl groups to alkanes and alkenes are important steps in many heterogeneously catalyzed reactions. On the one hand, while Pt is ubiquitous in industry because of its high activity toward C-H activation, many Pt-based catalysts tend to overbind reactive intermediates, which leads to deactivation by carbon deposition and coke formation. On the other hand, Cu binds intermediates more weakly than Pt, but activation barriers tend to be higher on Cu. We examine the reactivity of ethyl, the simplest alkyl group that can undergo hydrogenation and dehydrogenation via β-elimination, and show that isolated Pt atoms in Cu enable low-temperature hydrogenation of ethyl, unseen on Cu, while avoiding the decomposition pathways on pure Pt that lead to coking. Furthermore, we confirm the predictions of our theoretical model and experimentally demonstrate that the selectivity of ethyl (de)hydrogenation can be controlled by changing the surface coverage of hydrogen
A priori convergence estimates for a rough Poisson-Dirichlet problem with natural vertical boundary conditions
Stents are medical devices designed to modify blood flow in aneurysm sacs, in
order to prevent their rupture. Some of them can be considered as a locally
periodic rough boundary. In order to approximate blood flow in arteries and
vessels of the cardio-vascular system containing stents, we use multi-scale
techniques to construct boundary layers and wall laws. Simplifying the flow we
turn to consider a 2-dimensional Poisson problem that conserves essential
features related to the rough boundary. Then, we investigate convergence of
boundary layer approximations and the corresponding wall laws in the case of
Neumann type boundary conditions at the inlet and outlet parts of the domain.
The difficulty comes from the fact that correctors, for the boundary layers
near the rough surface, may introduce error terms on the other portions of the
boundary. In order to correct these spurious oscillations, we introduce a
vertical boundary layer. Trough a careful study of its behavior, we prove
rigorously decay estimates. We then construct complete boundary layers that
respect the macroscopic boundary conditions. We also derive error estimates in
terms of the roughness size epsilon either for the full boundary layer
approximation and for the corresponding averaged wall law.Comment: Dedicated to Professor Giovanni Paolo Galdi 60' Birthda
Families of classical subgroup separable superintegrable systems
We describe a method for determining a complete set of integrals for a
classical Hamiltonian that separates in orthogonal subgroup coordinates. As
examples, we use it to determine complete sets of integrals, polynomial in the
momenta, for some families of generalized oscillator and Kepler-Coulomb
systems, hence demonstrating their superintegrability. The latter generalizes
recent results of Verrier and Evans, and Rodriguez, Tempesta and Winternitz.
Another example is given of a superintegrable system on a non-conformally flat
space.Comment: 9 page
LOLS@stigma: comedy as activism in the changing times of the HIV epidemic
This paper examines how, in the midst of changing political times, some characteristics of HIV activism are changing, and suggests the relevance of these shifts for other fields of health activism. Despite the UK achieving UNAIDS’s ‘90–90-90ʹ testing and treatment goals, many in the UK lack up-to-date HIV knowledge and retain stigmatising attitudes, and some areas of testing failure remain. In response, people with HIV and HIV organisations are generating imaginative, collaborative projects that indicate effective contemporary forms of health activism may, as other critical health research suggests, be decentred, participatory, multimodal, affective, and implicit. The paper describes a 2016 HIV NGO-run comedy event directed at HIV awareness which was researched via qualitative pre- and post-measures, and two-month follow-up interviews. Findings pointed to strong effects of comedy, as enjoyment and ‘break’ in HIV thinking, feeling, and action; of a one-off event’s emotionality and particularity; and of performance in generating collectivity and HIV citizenship. The paper discusses the potential transferability of these findings to other health activisms, particularly around stigmatised conditions. It argues that such strategies of emotionality, multi-modality, and solidarity in a performance event can work as implicit activism for changing times, generating social change via a doubled politics of resistance and alterity
Advancing the Provision of Pain Education and Learning (APPEAL) study
Objectives Unrelieved pain is a substantial public health concern
necessitating improvements in medical education. The Advancing the Provision
of Pain Education and Learning (APPEAL) study aimed to determine current
levels and methods of undergraduate pain medicine education in Europe. Design
and methods Using a cross-sectional design, publicly available curriculum
information was sought from all medical schools in 15 representative European
countries in 2012–2013. Descriptive analyses were performed on: the provision
of pain teaching in dedicated pain modules, other modules or within the
broader curriculum; whether pain teaching was compulsory or elective; the
number of hours/credits spent teaching pain; pain topics; and teaching and
assessment methods. Results Curriculum elements were publicly available from
242 of 249 identified schools (97%). In 55% (133/242) of schools, pain was
taught only within compulsory non-pain-specific modules. The next most common
approaches were for pain teaching to be provided wholly or in part via a
dedicated pain module (74/242; 31%) or via a vertical or integrated approach
to teaching through the broader curriculum, rather than within any specific
module (17/242; 7%). The curricula of 17/242 schools (7%) showed no evidence
of any pain teaching. Dedicated pain modules were most common in France (27/31
schools; 87%). Excluding France, only 22% (47/211 schools) provided a
dedicated pain module and in only 9% (18/211) was this compulsory. Overall,
the median number of hours spent teaching pain was 12.0 (range 4–56.0 h; IQR:
12.0) for compulsory dedicated pain modules and 9.0 (range 1.0–60.0 h; IQR:
10.5) for other compulsory (non-pain specific) modules. Pain medicine was
principally taught in classrooms and assessed by conventional examinations.
There was substantial international variation throughout. Conclusions
Documented pain teaching in many European medical schools falls far short of
what might be expected given the prevalence and public health burden of pain
Harmonic lattice behavior of two-dimensional colloidal crystals
Using positional data from video-microscopy and applying the equipartition
theorem for harmonic Hamiltonians, we determine the wave-vector-dependent
normal mode spring constants of a two-dimensional colloidal model crystal and
compare the measured band-structure to predictions of the harmonic lattice
theory. We find good agreement for both the transversal and the longitudinal
mode. For , the measured spring constants are consistent with the
elastic moduli of the crystal.Comment: 4 pages, 3 figures, submitte
Investigation of conduction band structure, electron scattering mechanisms and phase transitions in indium selenide by means of transport measurements under pressure
In this work we report on Hall effect, resistivity and thermopower
measurements in n-type indium selenide at room temperature under either
hydrostatic and quasi-hydrostatic pressure. Up to 40 kbar (= 4 GPa), the
decrease of carrier concentration as the pressure increases is explained
through the existence of a subsidiary minimum in the conduction band. This
minimum shifts towards lower energies under pressure, with a pressure
coefficient of about -105 meV/GPa, and its related impurity level traps
electrons as it reaches the band gap and approaches the Fermi level. The
pressure value at which the electron trapping starts is shown to depend on the
electron concentration at ambient pressure and the dimensionality of the
electron gas. At low pressures the electron mobility increases under pressure
for both 3D and 2D electrons, the increase rate being higher for 2D electrons,
which is shown to be coherent with previous scattering mechanisms models. The
phase transition from the semiconductor layered phase to the metallic sodium
cloride phase is observed as a drop in resistivity around 105 kbar, but above
40 kbar a sharp nonreversible increase of the carrier concentration is
observed, which is attributed to the formation of donor defects as precursors
of the phase transition.Comment: 18 pages, Latex, 10 postscript figure
Inverse medium problem for a singular contrast
We consider an inverse medium problem in two- and three-dimensional cases. Namely, we investigate the problem of reconstruction of unknown compactly supported refractive index (contrast) from L-2 with a fixed positive wave number. The proof is based on the new estimates for the Green-Faddeev function in L-infinity space. The main goal of this work is to prove a uniqueness result in the two- and three-dimensional cases and to discuss some possible constructive methods for solving the problem. Finally, we present some numerical examples to demonstrate the results in two dimensions. Published under license by AIP Publishing.Peer reviewe
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