102 research outputs found
History of the Tromsø ionosphere heating facility
We present the historical background of the construction of a major ionospheric heating facility,
âHeatingâ, near Tromsø, Norway, in the 1970s by the Max Planck Institute for Aeronomy; we also detail the facilityâs subsequent operational history to the present. Heating was built next to the European Incoherent Scatter
Scientific Association (EISCAT) incoherent scatter (IS) radar facility and in a region with a multitude of diagnostic instruments used to study the auroral region. The facility was transferred to EISCAT in January 1993 and
continues to provide new discoveries in plasma physics and ionospheric and atmospheric science to this day. It
is expected that Heating will continue operating along with the new generation of IS radar, called EISCAT_3D,
when it is commissioned in the near future
The Extending of Observing Altitudes of Plasma and Ion Lines During Ionospheric Heating
Source at https://doi.org/10.1002/2017JA024809. The ultrahigh-frequency observation during an ionospheric heating experiment on 11 March 2014 at the European Incoherent Scatter Scientific Association Tromsø site illustrated a remarkable extension of observing altitudes of the enhanced plasma line and the ion line, implying that the enhanced ion acoustic wave and Langmuir wave should satisfy the Bragg condition within the extending altitude range. An analysis shows that the dependence of the wave number of the traveling ion acoustic wave on the profiles of enhanced electron temperature and ion mass, as are expected from the dispersion relation of the ion acoustic wave, leads to the extension of observing altitudes of the enhanced ion line. In addition, the altitude extension of the enhanced plasma line is dependent mainly on the profile of the electron density, although it is not independent of the profile of the electron temperature. Considering a small gradient profile of electron density, however, the enhanced electron temperature, as well as the thermal conduction along the magnetic field, may lead to the altitude extension of the enhanced plasma line
Modulation of polar mesospheric summer echoes (PMSEs) with high-frequency heating during low solar illumination
Polar mesospheric summer echo (PMSE) formation is linked to charged dust/ice particles in the mesosphere. We investigate the modulation of PMSEs with radio waves based on measurements with EISCAT VHF radar
and EISCAT heating facility during low solar illumination.
The measurements were made in August 2018 and 2020
around 20:02 UT. Heating was operated in cycles with intervals of 48 s on and 168 s off. More than half of the observed
heating cycles show a PMSE modulation with a decrease
in PMSE when the heater is on and an increase when it is
switched off again. The PMSE often increases beyond its initial strength. Less than half of the observed modulations have
such an overshoot. The overshoots are small or nonexistent
at strong PMSE, and they are not observed when the ionosphere is influenced by particle precipitation. We observe
instances of very large overshoots at weak PMSE. PMSE
modulation varies strongly from one cycle to the next, being
highly variable on spatial scales smaller than a kilometer and
timescales shorter than the timescales assumed for the variation in dust parameters. Average curves over several heating
cycles are similar to the overshoot curves predicted by theory and observed previously. Some of the individual curves
show stronger overshoots than reported in previous studies,
and they exceed the values predicted by theory. A possible
explanation is that the dust-charging conditions are different
either because of the reduced solar illumination around midnight or because of long-term changes in ice particles in the
mesosphere. We conclude that it is not possible to reliably derive the dust-charging parameters from the observed PMSE
modulations
A case study of a sporadic sodium layer observed by the ALOMAR Weber Na lidar
Several possible mechanisms for the production of
sporadic sodium layers have been discussed in the literature,
but none of them seem to explain all the accumulated observations.
The hypotheses range from direct meteoric input,
to energetic electron bombardment on meteoric smoke particles,
to ion neutralization, to temperature dependent chemistry.
The varied instrumentation located on Andøya and near
Tromsø in Norway gives us an opportunity to test the different
theories applied to high latitude sporadic sodium layers.
We use the ALOMARWeber sodium lidar to monitor the appearance
and characteristics of a sporadic sodium layer that
was observed on 5 November 2005. We also monitor the
temperature to test the hypotheses regarding a temperature
dependent mechanism. The EISCAT Tromsø Dynasonde,
the ALOMAR/UiO All-sky camera and the SKiYMET meteor
radar on Andøya are used to test the suggested relationships
of sporadic sodium layers and sporadic E-layers, electron
precipitation, and meteor deposition during this event.
We find that more than one candidate is eligible to explain
our observation of the sporadic sodium layer
Rietveld refinement of Sr5(AsO4)3Cl from high-resolution synchrotron data
The apatite-type compound, pentaÂstrontium trisÂ[arsenate(V)] chloride, Sr5(AsO4)3Cl, has been synthesized by ion exchange at high temperature from a synthetic sample of mimetite [Pb5(AsO4)3Cl] with SrCO3 as a by-product. The results of the Rietveld refinement, based on high resolution synchrotron X-ray powder diffraction data, show that the title compound crystallizes in the same structure as other halogenoapatites with general formula A
5(YO4)3
X (A = divalent cation, Y = pentaÂvalent cation, and X = F, Cl or Br) in the space group P63/m. The structure consists of isolated tetraÂhedral AsO4
3â anions (the As atom and two O atoms have m symmetry), separated by two crystallographically independent Sr2+ cations that are located on mirror planes and threefold rotation axes, respectively. One Sr atom is coordinated by nine O atoms and the other by six. The chloride anions (site symmetry ) are at the 2a sites and are located in the channels of the structure
Genetic factors and insulin secretion: gene variants in the IGF genes
IGFs are important regulators of pancreatic beta-cell development, growth, and maintenance. Mutations in the IGF genes have been found to be associated with type 2 diabetes, myocardial infarction, birth weight, and obesity. These associations could result from changes in insulin secretion. We have analyzed glucose-stimulated insulin secretion using hyperglycemic clamps in carriers of a CA repeat in the IGF-I promoter and an ApaI polymorphism in the IGF-II gene. Normal and impaired glucose-tolerant subjects (n = 237) were independently recruited from three different populations in the Netherlands and Germany to allow independent replication of associations. Both first- and second-phase insulin secretion were not significantly different between the various IGF-I or IGF-II genotypes. Remarkably, noncarriers of the IGF-I CA repeat allele had both a reduced insulin sensitivity index (ISI) and disposition index (DI), suggesting an altered balance between insulin secretion and insulin action. Other diabetes-related parameters were not significantly different for both the IGF-I and IGF-II gene variant. We conclude that gene variants in the IGF-I and IGF-II genes are not associated with detectable variations in glucose-stimulated insulin secretion in these three independent populations. Further studies are needed to examine the exact contributions of the IGF-I CA repeat alleles to variations in ISI and DI
Genome-wide analyses for personality traits identify six genomic loci and show correlations with psychiatric disorders
Personality is influenced by genetic and environmental factors1
and associated with mental health. However, the underlying
genetic determinants are largely unknown. We identified six
genetic loci, including five novel loci2,3, significantly associated
with personality traits in a meta-analysis of genome-wide
association studies (N = 123,132â260,861). Of these genomewide
significant loci, extraversion was associated with variants
in WSCD2 and near PCDH15, and neuroticism with variants
on chromosome 8p23.1 and in L3MBTL2. We performed a
principal component analysis to extract major dimensions
underlying genetic variations among five personality traits
and six psychiatric disorders (N = 5,422â18,759). The first
genetic dimension separated personality traits and psychiatric
disorders, except that neuroticism and openness to experience
were clustered with the disorders. High genetic correlations
were found between extraversion and attention-deficitâ
hyperactivity disorder (ADHD) and between openness and
schizophrenia and bipolar disorder. The second genetic
dimension was closely aligned with extraversionâintroversion
and grouped neuroticism with internalizing psychopathology
(e.g., depression or anxiety)
Supplemental Information 2: Example dataset description
Access to consistent, high-quality metadata is critical to finding, understanding, and reusing scientific data. However, while there are many relevant vocabularies for the annotation of a dataset, none sufficiently captures all the necessary metadata. This prevents uniform indexing and querying of dataset repositories. Towards providing a practical guide for producing a high quality description of biomedical datasets, the W3C Semantic Web for Health Care and the Life Sciences Interest Group (HCLSIG) identified Resource Description Framework (RDF) vocabularies that could be used to specify common metadata elements and their value sets. The resulting guideline covers elements of description, identification, attribution, versioning, provenance, and content summarization. This guideline reuses existing vocabularies, and is intended to meet key functional requirements including indexing, discovery, exchange, query, and retrieval of datasets, thereby enabling the publication of FAIR data. The resulting metadata profile is generic and could be used by other domains with an interest in providing machine readable descriptions of versioned datasets
Acoustic Correlates of Information Structure.
This paper reports three studies aimed at addressing three questions about the acoustic correlates of information structure in English: (1) do speakers mark information structure prosodically, and, to the extent they do; (2) what are the acoustic features associated with different aspects of information structure; and (3) how well can listeners retrieve this information from the signal? The information structure of subject-verb-object sentences was manipulated via the questions preceding those sentences: elements in the target sentences were either focused (i.e., the answer to a wh-question) or given (i.e., mentioned in prior discourse); furthermore, focused elements had either an implicit or an explicit contrast set in the discourse; finally, either only the object was focused (narrow object focus) or the entire event was focused (wide focus). The results across all three experiments demonstrated that people reliably mark (1) focus location (subject, verb, or object) using greater intensity, longer duration, and higher mean and maximum F0, and (2) focus breadth, such that narrow object focus is marked with greater intensity, longer duration, and higher mean and maximum F0 on the object than wide focus. Furthermore, when participants are made aware of prosodic ambiguity present across different information structures, they reliably mark focus type, so that contrastively focused elements are produced with greater intensity, longer duration, and lower mean and maximum F0 than noncontrastively focused elements. In addition to having important theoretical consequences for accounts of semantics and prosody, these experiments demonstrate that linear residualisation successfully removes individual differences in people's productions thereby revealing cross-speaker generalisations. Furthermore, discriminant modelling allows us to objectively determine the acoustic features that underlie meaning differences
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