26,556 research outputs found
Comparison of solar radio and EUV synoptic limb charts during the present solar maximum
The present solar cycle is particular in many aspects: it had a delayed
rising phase, it is the weakest of the last 100 years, and it presents two
peaks separated by more than one year. To understand the impact of these
characteristics on the solar chromosphere and coronal dynamics, images from a
wide wavelength range are needed. In this work we use the 17~GHz radio
continuum, formed in the upper chromosphere and the EUV lines 304 and
171~{\AA}, that come from the transition region (He II) and the corona (Fe IX,
X), respectively. We analyze daily images at 304 and 171~{\AA} obtained by the
Atmospheric Imaging Assembly (AIA). The 17~GHz maps were obtained by the
Nobeyama Radioheliograph (NoRH). To construct synoptic limb charts, we
calculated the mean emission of delimited limb areas with 100" wide and angular
separation of . At the equatorial region, the results show an
hemispheric asymmetry of the solar activity. The northern hemisphere dominance
is coincident with the first sunspot number peak, whereas the second peak
occurs concurrently with the increase in the activity at the south. The polar
emission reflects the presence of coronal holes at both EUV wavelengths,
moreover, the 17~GHz polar brightenings can be associated with the coronal
holes. Until 2013, both EUV coronal holes and radio polar brightenings were
more predominant at the south pole. Since then they have not been apparent in
the north, but thus appear in the beginning of 2015 in the south as observed in
the synoptic charts. This work strengthens the association between coronal
holes and the 17~GHz polar brightenings as it is evident in the synoptic limb
charts, in agreement with previous case study papers. The enhancement of the
radio brightness in coronal holes is explained by the presence of bright
patches closely associated with the presence of intense unipolar magnetic
fields.Comment: 6 pages, 5 figures. Acccepted for publication in Astronomy &
Astrophysic
Some properties of two Nambu--Jona-Lasinio -type models with inputs from lattice QCD
We investigate the phase diagram of the so-called
Polyakov--Nambu--Jona-Lasinio (PNJL) model at finite temperature and nonzero
chemical potential. The calculations are performed in the light and strange
quark sectors (, , ), which includes the 't Hooft instanton induced
interaction term that breaks the axial symmetry, and the quarks are coupled to
the (spatially constant) temporal background gauge field. On one hand, a
special attention is payed to the critical end point (CEP). The strength of the
flavor-mixing interaction alters the CEP location, since when it becomes weaker
the CEP moves to low temperatures and can even disappear. On the other hand, we
also explore the connection between QCD, a nonlocal Nambu--Jona-Lasinio type
model and the Landau gauge gluon propagator. Possible links between the
quenched gluon propagator and low energy hadronic phenomenology are
investigated.Comment: Contribution to the International Meeting "Excited QCD", Peniche,
Portugal, 06 - 12 May 201
Predicted defect induced vortex core switching in thin magnetic nanodisks
We investigate the influence of artificial defects (small holes) inserted
into magnetic nanodisks on the vortex core dynamics. One and two holes
(antidots) are considered. In general, the core falls into the hole but, in
particular, we would like to remark an interesting phenomenon not yet observed,
which is the vortex core switching induced by the vortex-hole interactions. It
occurs for the case with only one hole and for very special conditions
involving the hole size and position as well as the disk size. Any small
deformation in the disk geometry such as the presence of a second antidot
changes completely the vortex dynamics and the vortex core eventually falls
into one of the defects. After trapped, the vortex center still oscillates with
a very high frequency and small amplitude around the defect center.Comment: 11pages, Revtex format, 17 figure
Appetite-Related Eating Behaviours: An Overview of Assessment Methods, Determinants and Effects on Children's Weight
Identifying the underlying child-eating behaviours that contribute to weight differences across growth has been a constant challenge. This report reviews the various literature approaches for assessing appetite regulation. In doing so, it attempts to understand how appetite control develops and determines the eating habits in early childhood, and its effects on children's weight status. The interaction between homeostatic and hedonic mechanisms largely explains the appetite regulation process. Homeostatic mechanisms are mediated by the biological need to maintain the body's energy reserves, increasing the motivation to eat. On the contrary, the hedonic mechanisms are mediated by food reward, increasing the craving for high-palatable foods and triggering the release of dopamine and serotonin. There are many biological methods (plasma measurements of hormones, like leptin, ghrelin and insulin) and behavioural evaluation methods of appetite. The Children's Eating Behaviour Questionnaire is most commonly used, due to its adequate psychometric properties tested in several population settings. The development of eating behaviours begins in utero, and several determinants may contribute to a decrease in the ability to self-regulate dietary intake. Examples include genetic predisposition, the first taste experiences and the family environment, a key determinant in this process. Several eating behaviours contribute most to childhood obesity. Among them, are the external eating (eating by external stimuli, such as the mere presence of the food or its smell), food restriction (which may potentiate the uninhibited increased intake of the restricted foods) and emotional eating (intake due to emotional variations, especially negative feelings). These eating behaviours have been linked to childhood obesity. (c) 2018 S. Karger AG, BaselA.O. received funds from the FCT Investigator Programme (IF/01350/2015), with FEDER funds through the Operational Programme Competitiveness and Internationalisation, in addition to national funding from the Foundation for Science and Technology (FCT; Portuguese Ministry of Science, Technology and Higher Education), co-funded by the FCT and the POPH/FSE Program
Canonical transformation for stiff matter models in quantum cosmology
In the present work we consider Friedmann-Robertson-Walker models in the
presence of a stiff matter perfect fluid and a cosmological constant. We write
the superhamiltonian of these models using the Schutz's variational formalism.
We notice that the resulting superhamiltonians have terms that will lead to
factor ordering ambiguities when they are written as operators. In order to
remove these ambiguities, we introduce appropriate coordinate transformations
and prove that these transformations are canonical using the symplectic method.Comment: Revtex4 Class, 3 pages, No Figure
- âŠ