481 research outputs found
Low-lying magnetic loops in the solar internetwork
The aim of this work is to study the structure of the magnetic field vector
in the internetwork and search for the presence of small-scale loops. We invert
1.56 micron spectropolarimetric observations of internetwork regions at disc
centre by applying the SIR code. This allows us to recover the atmospheric
parameters that play a role in the formation of these spectral lines. We are
mainly interested in the structure of the magnetic field vector. We find that
many opposite polarity elements of the internetwork are connected by short
(2-6''), low-lying (photospheric) loops. These loops connect at least the 10-20
% of the internetwork flux visible in our data. Also we have some evidence that
points towards a dynamic scenario which can be produced by the emergence of
internetwork magnetic flux.Comment: Accepted for publication in A&A letter
Mandibular advancement devices in the treatment of obstructive sleep apnea syndrome
La apnea del sueño es un trastorno respiratorio, con consecuencias no deseables para la salud, que ocurre durante el sueño cuando se obstruyen o colapsan las vĂas aĂ©reas superiores. El fenĂłmeno es bien conocido clĂnicamente, con diagnosis y tratamientos mĂ©dicos contrastados, pero no existe una metodologĂa sencilla ni los instrumentos y tĂ©cnicas de anĂĄlisis necesarias para conocer y valorar cualitativa y cuantitativamente la respuesta fĂsica y clĂnica de una actuaciĂłn mandibular concreta. En este trabajo se muestra como las tĂ©cnicas digitales de tratamiento de imĂĄgenes, la dinĂĄmica de fluidos y la implementaciĂłn de criterios ingenieriles de diseño importados de otros campos de actividad permiten, a partir de unas imĂĄgenes mĂ©dicas convencionales, establecer una metodologĂa de anĂĄlisis sencilla Ăștil clĂnicamente para decidir las actuaciones, de presiĂłn o mecĂĄnicas, mandibulares mĂĄs convenientes. La metodologĂa se aplica a un paciente que sufre el sĂndrome y se estudia el efecto de un dispositivo mandibular (DAMÂź ), especialmente innovador, premiado cientĂfica y empresarialmente en varias ocasiones, que por medio de un avance de la mandĂbula, variable y distinto para cada paciente segĂșn las necesidades clĂnicas, provoca una apertura significativa de las vĂas aĂ©reas superiores.Obstructive sleep apnea syndrome (OSAS) consists in the occurrence of recurrent episodes of airflow limitation during sleep, with undesirable consequences for the health. The phenomenon is well known from a medical point of view (prognosis, diagnosis and treatment), but there is not a methodology or analysis tools for the quantification of the clinical response using Mandibular Advancement Devices (MAD). This paper shows how combining image processing, fluid dynamics and engineering design criteria, imported from other fields, allow to establish a simple analysis method clinically useful to decide the more convenient positioning of the MAD based on the pressure or mechanical movement of the jaw. This methodology is applied to a patient suffering OSAS which the objective to evaluate the changes provoked in the upper-airways due to an innovative mandibular device.Peer Reviewe
Chromospheric polarimetry through multi-line observations of the 850 nm spectral region II: A magnetic flux tube scenario
In this publication we continue the work started in Quintero Noda et al.
(2017) examining this time a numerical simulation of a magnetic flux tube
concentration. Our goal is to study if the physical phenomena that take place
in it, in particular, the magnetic pumping, leaves a specific imprint on the
examined spectral lines. We find that the profiles from the interior of the
flux tube are periodically dopplershifted following an oscillation pattern that
is also reflected in the amplitude of the circular polarization signals. In
addition, we analyse the properties of the Stokes profiles at the edges of the
flux tube discovering the presence of linear polarization signals for the Ca II
lines, although they are weak with an amplitude around 0.5% of the continuum
intensity. Finally, we compute the response functions to perturbations in the
longitudinal field and we estimate the field strength using the weak field
approximation. Our results indicate that the height of formation of the
spectral lines changes during the magnetic pumping process which makes the
interpretation of the inferred magnetic field strength and its evolution more
difficult. These results complement those from previous works demonstrating the
capabilities and limitations of the 850 nm spectrum for chromospheric Zeeman
polarimetry in a very dynamic and complex atmosphere.Comment: 12 pages, 12 figures, 0 tables, MNRAS main journal publicatio
Chromospheric polarimetry through multi-line observations of the 850 nm spectral region III: Chromospheric jets driven by twisted magnetic fields
We investigate the diagnostic potential of the spectral lines at 850 nm for
understanding the magnetism of the lower atmosphere. For that purpose, we use a
newly developed 3D simulation of a chromospheric jet to check the sensitivity
of the spectral lines to this phenomenon as well as our ability to infer the
atmospheric information through spectropolarimetric inversions of noisy
synthetic data. We start comparing the benefits of inverting the entire
spectrum at 850 nm versus only the Ca II 8542 A spectral line. We found a
better match of the input atmosphere for the former case, mainly at lower
heights. However, the results at higher layers were not accurate. After several
tests, we determined that we need to weight more the chromospheric lines than
the photospheric ones in the computation of the goodness of the fit. The new
inversion configuration allows us to obtain better fits and consequently more
accurate physical parameters. Therefore, to extract the most from multi-line
inversions, a proper set of weights needs to be estimated. Besides that, we
conclude again that the lines at 850 nm, or a similar arrangement with Ca II
8542 A plus Zeeman sensitive photospheric lines, poses the best observing
configuration for examining the thermal and magnetic properties of the lower
solar atmosphere.Comment: 14 pages, 11 figure
Successful fiber sensing technologies and hot topics for the near future
Inside the Photonics field Optical Fiber Sensors (OFS) are currently being used and will still be used in the future in a wide number of applications because its properties present technical advantages over traditional techniques or, sometimes, is practically the only feasible solution. In this paper, the more successful techniques will be reviewed. Then a prospective for the near future of the market and hot topics in which invest research resources will be suggested
Naming a phantom â the quest to find the identity of Ulluchu, an unidentified ceremonial plant of the Moche culture in Northern Peru
The botanical identification of Ulluchu, an iconic fruit frequently depicted in the art of the pre-Columbian Moche culture that flourished from A.D. 100â800 on the Peruvian north coast, has eluded scientists since its documentation in ceramics in the 1930s. Moche fine-line drawings of Ulluchu normally depict seed-pods or seeds floating in the air in sacrificial scenes, associated with runners and messengers or intoxicated priests. It is a grooved, comma-shaped fruit with an enlarged calyx found mainly in fine-line scenes painted on Moche ceramics. The term first appeared without linguistic explanation in the work of pioneer Moche scholar Rafael Larco Hoyle, and the identification of the plant was seen as the largest remaining challenge in current archaebotany at the Peruvian North coast. The name Ulluchu seems to have been coined by Larco. According to his description, the name originated in the VirĂș River valley, and is supposedly of Mochica origin. However, there is no linguistic evidence that such a term indeed existed in the Mochica or Yunga language
Interpretation of HINODE SOT/SP asymmetric Stokes profiles observed in quiet Sun network and internetwork
We present the first interpretation of the Stokes profile asymmetries
measured in the FeI 630 nm lines by SOT/SP, in both quiet Sun internetwork (IN)
and network regions. The inversion is carried out under the hypothesis of
MISMA, where the unresolved structure is assumed to be optically thin. We
analyze a 29.52"x31.70" subfield carefully selected to be representative of the
properties of a 302"x162" quiet Sun field-of-view at disk center. The inversion
code is able to reproduce the observed asymmetries in a very satisfactory way.
The inversion code interprets 25% of inverted profiles as emerging from pixels
in which both positive and negative polarities coexist. kG field strengths are
found at the base of the photosphere in both network and IN; in the case of the
latter, both kG fields and hG fields are admixed. When considering the magnetic
properties at the mid photosphere most kG fields are gone, and the statistics
is dominated by hG fields. We constrain the magnetic field of only 4.5% of the
analyzed photosphere (and this percentage reduces to 1.3% when referred to all
pixels, including those with low polarization not analyzed). The rest of the
plasma is consistent with the presence of weak fields not contributing to the
detected polarization signals. The average flux densities derived in the full
subfield and in IN regions are higher than the ones derived from the same
dataset by Milne-Eddington inversion. The existence of large asymmetries in
SOT/SP polarization profiles is uncovered. These are not negligible in quiet
Sun data. The MISMA inversion code reproduces them in a satisfactory way, and
provides a statistical description of the magnetized IN and network which
partly differs and complements the results obtained so far. From this it
follows the importance of having a complete interpretation of the line profile
shapes.Comment: 11 pages, 9 figures, 1 table - Accepted for publication on A&
Solar Spectroscopy and (Pseudo-)Diagnostics of the Solar Chromosphere
I first review trends in current solar spectrometry and then concentrate on
comparing various spectroscopic diagnostics of the solar chromosphere. Some are
actually not at all chromospheric but just photospheric or clapotispheric and
do not convey information on chromospheric heating, even though this is often
assumed. Balmer Halpha is the principal displayer of the closed-field
chromosphere, but it is unclear how chromospheric fibrils gain their large
Halpha opacity. The open-field chromosphere seems to harbor most if not all
coronal heating and solar wind driving, but is hardly seen in optical
diagnostics.Comment: To appear in "Recent Advances in Spectroscopy: Astrophysical,
Theoretical and Experimental Perspectives", eds. R.K. Chaudhuri, M.V.
Mekkaden, A.V. Raveendran and A. Satya Narayanan, Astrophysics and Space
Science Proceedings, Springer, Heidelberg, 2009. Revision: references
corrected, new references added, minor text correction
Limited effect of patient and disease characteristics on compliance with hospital antimicrobial guidelines
Objective: Physicians frequently deviate from guidelines that promote prudent use of antimicrobials. We explored to what extent patient and disease characteristics were associated with compliance with guideline recommendations for three common infections. Methods: In a 1-year prospective observational study, 1,125 antimicrobial prescriptions were analysed for compliance with university hospital guidelines. Results: Compliance varied significantly between and within the groups of infections studied. Compliance was much higher for lower respiratory tract infections (LRTIs; 79%) than for sepsis (53%) and urinary tract infections (UTIs; 40%). Only predisposing illnesses and active malignancies were associated with more compliant prescribing, whereas alcohol/ intravenous drug abuse and serum creatinine levels > 130 mu mol/l were associated with less compliant prescribing. Availability of culture results had no impact on compliance with guidelines for sepsis but was associated with more compliance in UTIs and less in LRTIs. Narrowing initial broad-spectrum antimicrobial therapy to cultured pathogens was seldom practised. Most noncompliant prescribing concerned a too broad spectrum of activity when compared with guideline-recommended therapy. Conclusion: Patient characteristics had only a limited impact on compliant prescribing for a variety of reasons. Physicians seemed to practise defensive prescribing behaviour, favouring treatment success in current patients over loss of effectiveness due to resistance in future patients
Time series of high resolution photospheric spectra in a quiet region of the Sun. II. Analysis of the variation of physical quantities of granular structures
From the inversion of a time series of high resolution slit spectrograms
obtained from the quiet sun, the spatial and temporal distribution of the
thermodynamical quantities and the vertical flow velocity is derived as a
function of logarithmic optical depth and geometrical height. Spatial coherence
and phase shift analyzes between temperature and vertical velocity depict the
height variation of these physical quantities for structures of different size.
An average granular cell model is presented, showing the granule-intergranular
lane stratification of temperature, vertical velocity, gas pressure and density
as a function of logarithmic optical depth and geometrical height. Studies of a
specific small and a specific large granular cell complement these results. A
strong decay of the temperature fluctuations with increasing height together
with a less efficient penetration of smaller cells is revealed. The T -T
coherence at all granular scales is broken already at log tau =-1 or z~170 km.
At the layers beyond, an inversion of the temperature contrast is revealed.
Vertical velocities are in phase throughout the photosphere and penetrate into
the highest layers under study.Comment: 13 pages, 12 figures, 1 table; Astronomy & Astrophysics, Volume 441,
Issue 3, pp.1157-1169, 200
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