401 research outputs found
Magnetic nulls and super-radial expansion in the solar corona
Magnetic fields in the sun's outer atmosphere -- the corona -- control both
solar-wind acceleration and the dynamics of solar eruptions. We present the
first clear observational evidence of coronal magnetic nulls in off-limb
linearly polarized observations of pseudostreamers, taken by the Coronal
Multichannel Polarimeter (CoMP) telescope. These nulls represent regions where
magnetic reconnection is likely to act as a catalyst for solar activity. CoMP
linear-polarization observations also provide an independent, coronal proxy for
magnetic expansion into the solar wind, a quantity often used to parameterize
and predict the solar wind speed at Earth. We introduce a new method for
explicitly calculating expansion factors from CoMP coronal linear-polarization
observations, which does not require photospheric extrapolations. We conclude
that linearly-polarized light is a powerful new diagnostic of critical coronal
magnetic topologies and the expanding magnetic flux tubes that channel the
solar wind
From Forbidden Coronal Lines to Meaningful Coronal Magnetic Fields
We review methods to measure magnetic fields within the corona using the
polarized light in magnetic-dipole (M1) lines. We are particularly interested
in both the global magnetic-field evolution over a solar cycle, and the local
storage of magnetic free energy within coronal plasmas. We address commonly
held skepticisms concerning angular ambiguities and line-of-sight confusion. We
argue that ambiguities are in principle no worse than more familiar remotely
sensed photospheric vector-fields, and that the diagnosis of M1 line data would
benefit from simultaneous observations of EUV lines. Based on calculations and
data from eclipses, we discuss the most promising lines and different
approaches that might be used. We point to the S-like [Fe {\sc XI}] line (J=2
to J=1) at 789.2nm as a prime target line (for ATST for example) to augment the
hotter 1074.7 and 1079.8 nm Si-like lines of [Fe {\sc XIII}] currently observed
by the Coronal Multi-channel Polarimeter (CoMP). Significant breakthroughs will
be made possible with the new generation of coronagraphs, in three distinct
ways: (i) through single point inversions (which encompasses also the analysis
of MHD wave modes), (ii) using direct comparisons of synthetic MHD or
force-free models with polarization data, and (iii) using tomographic
techniques.Comment: Accepted by Solar Physics, April 201
Spectroscopic signature of Alfv\'en waves damping in a polar coronal hole up to 0.4 solar radii
Between February 24-25, 2009, the EIS spectrometer onboard the Hinode
spacecraft performed special "sit & stare" observations above the South polar
coronal hole continuously over more than 22 hours. Spectra were acquired with
the 1" slit placed off-limb covering altitudes up to 0.48 R
( Mm) above the Sun surface, in order to study with EIS the
non-thermal spectral line broadenings. Spectral lines such as Fe {\sc xii}
186.88, Fe {\sc xii} 193.51, Fe {\sc xii} 195.12 and
Fe {\sc xiii} 202.04 are observed with good statistics up to high
altitudes and they have been analyzed in this study. Results show that the FWHM
of Fe {\sc xii} 195.12 line increases up to R,
then decreases higher up. EIS stray light has been estimated and removed.
Derived electron density and non-thermal velocity profiles have been used to
estimate the total energy flux transported by Alfv\'en waves off-limb in polar
coronal hole up to R. The computed Alfv\'en wave energy
flux density progressively decays with altitude from erg cm s at 0.03 R down to erg cm s at 0.4 R, with an average energy
decay rate erg cm
s. Hence, this result suggests energy deposition by Alfv\'en waves in a
polar coronal hole, thus providing a significant source for coronal heating.Comment: Physical units of the Alfv\'en wave Energy Decay Rate revised with respect to the published version. Scientific results
and conclusions unchange
Analysis of the solar cycle and core rotation using 15 years of Mark-I observations:1984-1999. I. The solar cycle
High quality observations of the low-degree acoustic modes (p-modes) exist
for almost two complete solar cycles using the solar spectrophotometer Mark-I,
located at the Observatorio del Teide (Tenerife, Spain) and operating now as
part of the Birmingham Solar Oscillations Network (BiSON). We have performed a
Fourier analysis of 30 calibrated time-series of one year duration covering a
total period of 15 years between 1984 and 1999. Applying different techniques
to the resulting power spectra, we study the signature of the solar activity
changes on the low-degree p-modes. We show that the variation of the central
frequencies and the total velocity power (TVP) changes. A new method of
simultaneous fit is developed and a special effort has been made to study the
frequency-dependence of the frequency shift. The results confirm a variation of
the central frequencies of acoustic modes of about 450 nHz, peak-to-peak, on
average for low degree modes between 2.5 and 3.7 mHz. The TVP is
anti-correlated with the common activity indices with a decrease of about 20%
between the minimum and the maximum of solar cycle 22. The results are compared
with those obtained for intermediate degrees, using the LOWL data. The
frequency shift is found to increase with the degree with a weak l-dependence
similar to that of the inverse mode mass. This verifies earlier suggestions
that near surface effects are predominant.Comment: Accepted by A&A October 3 200
Smartphone Distraction: Italian Validation of the Smartphone Distraction Scale (SDS)
This work aimed to validate the use of the Smartphone Distraction Scale (SDS) in Italy. The SDS was devised to assess distraction related to smartphone use in adult populations. A cross-sectional study was conducted among n = 609 adults (females = 76.4%; mean age = 30.26; SD age = 9.90). An assessment of the factorial structure of the Italian version was carried out using exploratory factor analysis (EFA) and confirmatory factor analysis (CFA). The four factors identified by Throuvala and colleagues were confirmed (i.e., attention impulsiveness, online vigilance, multitasking and emotion regulation). Reliability was assessed using Cronbach's alpha coefficient (0.703-0.889). The scale's scores showed significant linear correlations with validated instruments, including the Mobile Phone Problematic Use Scale (MPPUS)and the Cognitive Failures Questionnaire (CFQ). A multivariate analysis of variance showed significant differences in the means among participants belonging to different age groups (born before 1995 vs. born after 1996). In summary, the good psychometric properties observed led us to assume that this instrument can be applied and used in Italian studies to assess the cognitive dimension of distraction related to the use of smartphones
Price-personalization: Customer typology based on hospitality business
Personalization drives value co-creation and willingness to pay for customers. Consumers are keen to receive personalized services but have various willingness to pay for the personalization process. The willingness to pay is influenced by motives for customer purchase behavior and personalization expectations in a specific context. It also depends on disposable income and the availability of resources, as well as the severity of requirements. The results indicate that customers comprise a heterogeneous market concerning their personalization expectations and willingness to pay. The paper proposes a customer typology based on a conceptual framework that includes personalization, willingness to pay, customer philosophy, and novelty-familiarity continuum. By analyzing data from thirty-eight semi-structured interviews, six customer types are proposed, namely: Budget Adventurer, Family Explorer, Relation Seeker, Relaxation Seeker, Delight Seeker, and Must-Have Customer. The findings suggest that revenue managers should understand customer personalization preferences for each type in order to develop effective pricing strategies
Brewing of filter coffee
We report progress on mathematical modelling of coffee grounds in a drip filter coffee machine. The report focuses on the evolution of the shape of the bed of coffee grounds during extraction with some work also carried out on the chemistry of extraction. This work was sponsored by Philips who are interested in understanding an observed correlation between the final shape of the coffee grounds and the quality of the coffee. We used experimental data gathered by Philips and ourselves to identify regimes in the coffee brewing process and relevant regions of parameter space. Our work makes it clear that a number of separate processes define the shape of the coffee bed depending on the values of the parameters involved e.g. the size of the grains and the speed of fluid flow during extraction. We began work on constructing mathematical models of the redistribution of the coffee grounds specialised to each region and on a model of extraction. A variety of analytic and numerical tools were used. Furthermore our research has progressed far enough to allow us to begin to exploit connections between this problem and other areas of science, in particular the areas of sedimentology and geomorphology, where the processes we have observed in coffee brewing have been studied
Epigenome-wide association study reveals decreased average methylation levels years before breast cancer diagnosis
Interest in the potential of DNA methylation in peripheral blood as a biomarker of cancer risk is increasing. We aimed to assess whether epigenome-wide DNA methylation measured in peripheral blood samples obtained before onset of the disease is associated with increased risk of breast cancer. We report on three independent prospective nested case-control studies from the European Prospective Investigation into Cancer and Nutrition (EPIC-Italy; n = 162 matched case-control pairs), the Norwegian Women and Cancer study (NOWAC; n = 168 matched pairs), and the Breakthrough Generations Study (BGS; n = 548 matched pairs). We used the Illumina 450k array to measure methylation in the EPIC and NOWAC cohorts. Whole-genome bisulphite sequencing (WGBS) was performed on the BGS cohort using pooled DNA samples, combined to reach 50× coverage across ~16 million CpG sites in the genome including 450k array CpG sites. Mean β values over all probes were calculated as a measurement for epigenome-wide methylation
Suicide inhibition of alpha-oxamine synthases:structures of the covalent adducts of 8-amino-7-oxononanoate synthase with trifluoroalanine
The suicide inhibition of the α-oxamine synthases by the substrate analog, L-trifluoroalanine was investigated. The inhibition resulted in the formation of a complex with loss of all three fluorine atoms. Decarboxylation and loss of fluoride occurred immediately after aldimine formation. The inherent flexibility could allow the difluorinated intermediate complex to adopt a suitable conformation. Decarboxylation in the normal mechanism occurs after formation of the ketoacid intermediate.link_to_subscribed_fulltex
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