3,745 research outputs found
On the contribution of thermal excitation to the total 630.0 nm emissions in the northern cusp ionosphere
Direct impact excitation by precipitating electrons is believed to be the
main source of 630.0 nm emissions in the cusp ionosphere. However, this paper
investigates a different source, 630.0 emissions caused by thermally excited
atomic oxygen OD) when high electron temperature prevail in the cusp. On
22 January 2012 and 14 January 2013, the European Incoherent Scatter Scientific
Association (EISCAT) radar on Svalbard measured electron temperature
enhancements exceeding 3000 K near magnetic noon in the cusp ionosphere over
Svalbard. The electron temperature enhancements corresponded to electron
density enhancements exceeding m accompanied by intense 630.0
nm emissions in a field of view common to both the EISCAT Svalbard radar and a
meridian scanning photometer. This offered an excellent opportunity to
investigate the role of thermally excited OD) 630.0 nm emissions in the
cusp ionosphere. The thermal component was derived from the EISCAT Radar
measurements and compared with optical data. For both events the calculated
thermal component had a correlation coefficient greater than 0.8 to the total
observed 630.0 nm intensity which contains both thermal and particle impact
components. Despite fairly constant solar wind, the calculated thermal
component intensity fluctuated possibly due to dayside transients in the
aurora
Isolation, characterization and heterologous expression of a novel chitosanase from Janthinobacterium sp. strain 4239
A class of well-posed parabolic final value problems
This paper focuses on parabolic final value problems, and well-posedness is
proved for a large class of these. The clarification is obtained from Hilbert
spaces that characterise data that give existence, uniqueness and stability of
the solutions. The data space is the graph normed domain of an unbounded
operator that maps final states to the corresponding initial states. It induces
a new compatibility condition, depending crucially on the fact that analytic
semigroups always are invertible in the class of closed operators. Lax--Milgram
operators in vector distribution spaces constitute the main framework. The
final value heat conduction problem on a smooth open set is also proved to be
well posed, and non-zero Dirichlet data are shown to require an extended
compatibility condition obtained by adding an improper Bochner integral.Comment: 16 pages. To appear in "Applied and numerical harmonic analysis"; a
reference update. Conference contribution, based on arXiv:1707.02136, with
some further development
Might salicylate exert benefits against childhood cancer?
Childhood cancers are a broad range of diseases. Research on the chemopreventive potential of non-steroidal anti-inflammatory drugs, such as aspirin (acetylsalicylate) has yet to be fully directed towards childhood cancers. A prima facie hypothesis on salicylate and childhood cancer would therefore be based on several factors. Firstly, salicylate inhibits the production of inflammatory prostaglandins, which have been shown to stimulate the growth of cancer cells. Secondly, salicylate inhibits the growth of cancer cells in pre-clinical models. Thirdly, salicylate is a natural component of fruits and vegetables so it is consumed within the diet. Further research, of which some possibilities are identified, is recommended
Granular Rayleigh-Taylor Instability: Experiments and Simulations
A granular instability driven by gravity is studied experimentally and
numerically. The instability arises as grains fall in a closed Hele-Shaw cell
where a layer of dense granular material is positioned above a layer of air.
The initially flat front defined by the grains subsequently develops into a
pattern of falling granular fingers separated by rising bubbles of air. A
transient coarsening of the front is observed right from the start by a finger
merging process. The coarsening is later stabilized by new fingers growing from
the center of the rising bubbles. The structures are quantified by means of
Fourier analysis and quantitative agreement between experiment and computation
is shown. This analysis also reveals scale invariance of the flow structures
under overall change of spatial scale.Comment: 4 pages, 11 figure
Controlling the Superconducting Transition by Rotation of an Inversion Symmetry-Breaking Axis
We consider a hybrid structure where a material with Rashba-like spin-orbit
coupling is proximity coupled to a conventional superconductor. We find that
the superconducting critical temperature can be tuned by rotating the
vector characterizing the axis of broken inversion symmetry.
This is explained by a leakage of -wave singlet Cooper pairs out of the
superconducting region, and by conversion of -wave singlets into other types
of correlations, among these -wave odd-frequency pairs robust to impurity
scattering. These results demonstrate a conceptually different way of tuning
compared to the previously studied variation of in magnetic
hybrids.Comment: 4 pages, (11 pages including Supplemental Material), 3 figure
Parental Age and Birth Defects : A Sibling Study
Funding Open access funding provided by University of Bergen (incl Haukeland University Hospital).Peer reviewedPublisher PD
Magnetization reorientation due to the superconducting transition in heavy-metal heterostructures
Recent theoretical and experimental work has demonstrated how the
superconducting critical temperature () can be modified by rotating the
magnetization of a single homogeneous ferromagnet proximity-coupled to the
superconducting layer. This occurs when the superconductor and ferromagnet are
separated by a thin heavy normal metal that provides an enhanced interfacial
Rashba spin-orbit interaction. We consider the reciprocal effect: magnetization
reorientation driven by the superconducting phase transition. We solve the
tight-binding Bogoliubov-de Gennes equations on a lattice self-consistently and
find that the relative angle between the spin-orbit field and the magnetization
gives rise to a contribution in the free energy even in the normal state due to
band-structure effects. For temperatures below , superconductivity gives
rise to a competing contribution. By lowering the temperature, in addition to
reorientation of the favored magnetization direction from in-plane to
out-of-plane, a in-plane rotation for thicker ferromagnetic layers is
possible. Furthermore, computation of of the structure in the ballistic
limit shows a dependence on the in-plane orientation of the magnetization, in
contrast to our previous result on the diffusive limit. This finding is
relevant with respect to thin-film heterostructures since these are likely to
be in the ballistic regime of transport. Finally, we discuss the experimental
feasibility of observing the magnetic anisotropy induced by the superconducting
transition when other magnetic anisotropies, such as the shape anisotropy for a
ferromagnetic film, are taken into account. Our work suggests that the
superconducting condensation energy in principle can trigger a reorientation of
the magnetization of a thin-film ferromagnet upon lowering the temperature
below , in particular for ferromagnets with weak magnetic anisotropies.Comment: 11 pages, 10 figure
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