109 research outputs found
Newly formed downflow lanes in exploding granules in the solar photosphere
Exploding granules have drawn renewed interest because of their interaction
with the magnetic field. Especially the newly forming downflow lanes developing
in their centre seem to be eligible candidates for the intensification of
magnetic fields. We analyse spectroscopic data from two different instruments
in order to study the intricate velocity pattern within the newly forming
downflow lanes in detail. We aim to examine general properties of a number of
exploding granules. To gain a better understanding of the formation process of
the developing intergranular lane in exploding granules, we study the temporal
evolution and height dependence of the line-of-sight velocities at their
formation location. Additionally, we search for evidence that exploding
granules act as acoustic sources. We investigated the evolution of several
exploding granules using data taken with the Interferometric Bidimensional
Spectrometer and the Imaging Magnetograph eXperiment. Velocities for different
heights of the solar atmosphere were determined by computing bisectors of the
Fe I 6173.0{\AA} and the Fe I 5250.2{\AA} lines. We performed a wavelet
analysis to study the intensity and velocity oscillations within and around
exploding granules. We also compared our findings with predictions of numerical
simulations. We found that exploding granules have significantly longer
lifetimes than regular granules. Exploding granules larger than 3.8 arcsec form
an independent intergranular lane during their decay phase, while smaller
granules usually fade away or disappear into the intergranular area. For all
exploding granules that form a new intergranular downflow lane, we find a
temporal height-dependent shift with respect to the maximum of the downflow
velocity. Our suggestion that this results from a complex atmospheric structure
within the newly forming downflow lane is supported by the simulations.Comment: 13 pages; accepted for publication in A&
Tracking magnetic bright point motions through the solar atmosphere
High-cadence, multiwavelength observations and simulations are employed for the analysis of solar photospheric magnetic bright points (MBPs) in the quiet Sun. The observations were obtained with the Rapid Oscillations in the Solar Atmosphere (ROSA) imager and the Interferometric Bidimensional Spectrometer at the Dunn Solar Telescope. Our analysis reveals that photospheric MBPs have an average transverse velocity of approximately 1 km s−1, whereas their chromospheric counterparts have a slightly higher average velocity of 1.4 km s−1. Additionally, chromospheric MBPs were found to be around 63 per cent larger than the equivalent photospheric MBPs. These velocity values were compared with the output of numerical simulations generated using the MURAM code. The simulated results were similar, but slightly elevated, when compared to the observed data. An average velocity of 1.3 km s−1 was found in the simulated G-band images and an average of 1.8 km s−1 seen in the velocity domain at a height of 500 km above the continuum formation layer. Delays in the change of velocities were also analysed. Average delays of ∼4 s between layers of the simulated data set were established and values of ∼29 s observed between G-band and Ca II K ROSA observations. The delays in the simulations are likely to be the result of oblique granular shock waves, whereas those found in the observations are possibly the result of a semi-rigid flux tube
Chemical and biological factors in the control Brucella and Brucellosis
Brucellosis is a highly contagious bacterial zoonosis that affects millions of people worldwide. Brucella is highly infectious, especially when aerosolized. The infection induces severe protracted diseases, which are both debilitating and incapacitating, hence, Brucella melitensis has been considered a potential biological warfare agent. In the battle against Brucella, it is crucial to know its chemical-structure and biochemistry-metabolic characteristics. It is well known that Brucella, as well as many other intracellular bacterial pathogens, has evolved to survive and even proliferate within monocytes and macrophages cells. Depending on the route of entry (complement, Fc, lectin or fibronectin receptors), the fate of the bacteria will vary; it may even segregate from the endocytic route towards the endoplasmic reticulum. This intracellular “non regular” behaviour of Brucella makes treatment difficult. Most antibiotics, although effective in vitro, do not actively pass through cellular membranes, or, once inside, may not reach the discrete intracellular niche where the bacteria is hidden. Therefore, complete eradication of the microorganisms is difficult to achieve, and the incidence of relapses is rather high. Taking these data into consideration, this review will evaluate the past, current and new trends in the control of brucellosis, paying special attention to the drug delivery systems as potential vectors for targeting these intracellular sites where the organisms are located
Three-dimensional non-LTE radiative transfer effects in Fe I lines I. Flux sheet and flux tube geometries
In network and active region plages, the magnetic field is concentrated into
structures often described as flux tubes (FTs) and sheets (FSs). 3-D radiative
transfer (RT) is important for energy transport in these concentrations. It is
also expected to be important for diagnostic purposes but has rarely been
applied for that purpose. Using true 3-D, non-LTE (NLTE) RT in FT/FS models, we
compute Fe line profiles commonly used to diagnose the Sun's magnetic field by
comparing the results with those obtained from LTE/1-D (1.5-D) NLTE
calculations. Employing a multilevel iron atom, we study the influence of basic
parameters such as Wilson depression, wall thickness, radius/width, thermal
stratification or magnetic field strength on all Stokes parameters in the
thin-tube approximation. The use of different levels of approximations of RT
may lead to considerable differences in profile shapes, intensity contrasts,
equivalent widths, and the determination of magnetic field strengths. In
particular, LTE, which often provides a good approach in planar 1-D
atmospheres, is a poor approximation in our flux sheet model for some of the
most important diagnostic Fe I lines (524.7nm, 525.0nm, 630.1nm, and 630.2nm).
The observed effects depend on parameters such as the height of line formation,
field strength, and internal temperature stratification. Differences between
the profile shapes may lead to errors in the determination of magnetic fields
on the order of 10 to 20%, while errors in the determined temperature can reach
300-400K. The empirical FT models NET and PLA turn out to minimize the effects
of 3D RT, so that results obtained with these models by applying LTE may also
remain valid for 3-D NLTE calculations. Finally, horizontal RT is found to only
insignificantly smear out structures such as the optically thick walls of FTs
and FSs, allowing features as narrow as 10km to remain visible.Comment: 20 pages, 21 figures, accepted for publication to "Astronomy and
Astrophysics
Abundances of the elements in the solar system
A review of the abundances and condensation temperatures of the elements and
their nuclides in the solar nebula and in chondritic meteorites. Abundances of
the elements in some neighboring stars are also discussed.Comment: 42 pages, 11 tables, 8 figures, chapter, In Landolt- B\"ornstein, New
Series, Vol. VI/4B, Chap. 4.4, J.E. Tr\"umper (ed.), Berlin, Heidelberg, New
York: Springer-Verlag, p. 560-63
Liberación controlada de principios activos mediante el empleo de formulaciones galénicas
Drugs inside a conventional galenic form are distributed between specific biological targets and other anatomical tissues. With the aim to obtain a more rational and a better therapeutic, one of the most promising possibilities by using the concept of vector- ization: association of an active principle to an appropriate vector with the object to increase its action efficiency and efficacy. By this means, they do not just increase the affinity of the drug to the target but also active principle gets protected from a potentially hos- tile environment (hydrolytic enzymes, acid pH, etc.). The success in the extension of the applications of the vectorización depends more and more of an appropriate design, for what the fundamental objective of this revision will be the one of presenting the general char- acteristics and some of the current applications in these new galenic forms.Los principios activos incluidos en una
forma galénica convencional se distribuyen indistintamente
entre dianas biológicas específicas y otros tejidos
anatómicos. Con el fin de obtener una terapéutica
más racional y mejor adaptada, una de las posibilidades
más prometedoras es la que utiliza el concepto
de vectorización: asociación del principio activo a un
vector apropiado, con objeto de aumentar la eficacia y
la especificidad de acción del mismo. De esta manera,
no solo aumenta la afinidad del fármaco por la diana,
sino que además queda protegido de un ambiente
potencialmente hostil (enzimas hidrolíticas, pH ácido,
etc.). El éxito en la extensión de las aplicaciones de la
vectorización depende cada vez más de un diseño
adecuado, por lo que el objetivo fundamental de esta
revisión será la de presentar las características generales
y algunas de las actuales aplicaciones de estas
nuevas formas farmacéuticas
Tree rings of Scots pine (Pinus sylvestris L.) as a source of information about past climate in northern Poland
Scots pine (Pinus sylvestris) is a very common tree in Polish forests, and therefore was widely used as timber. A relatively large amount of available wood allowed a long-term chronology to be built up and used as a source of information about past climate. The analysis of reconstructed indexed values of mean temperature in 51-year moving intervals allowed the recognition of the coldest periods in the years 1207–1346, 1383–1425, 1455–1482, 1533–1574, 1627–1646, and 1694–1785. The analysis of extreme wide and narrow rings forms a complementary method of examining climatic data within tree rings. The tree ring widths, early wood and late wood widths of 16 samples were assessed during the period 1581–1676. The most apparent effect is noted in the dry summer of 1616. According to previous research and our findings, temperature from February to March seems to be one of the most stable climatic factors which influenced pine growth in Poland. Correlation coefficients in the calibration and validation procedure gave promising results for temperature reconstruction from the pine chronology
Stable carbon isotope ratios of tree-ring cellulose from the site network of the EU-Project ‘ISONET’
Spatio‐temporal patterns of tree growth as related to carbon isotope fractionation in European forests under changing climate
Aim
To decipher Europe-wide spatiotemporal patterns of forest growth dynamics and their associations with carbon isotope fractionation processes inferred from tree rings as modulated by climate warming.
Location
Europe and North Africa (30‒70°N, 10°W‒35°E).
Time period
1901‒2003.
Major taxa studied
Temperate and Euro-Siberian trees.
Methods
We characterize changes in the relationship between tree growth and carbon isotope fractionation over the 20th century using a European network consisting of 20 site chronologies. Using indexed tree-ring widths (TRWi), we assess shifts in the temporal coherence of radial growth across sites (synchrony) for five forest ecosystems (Atlantic, Boreal, cold continental, Mediterranean and temperate). We also examine whether TRWi shows variable coupling with leaf-level gas exchange, inferred from indexed carbon isotope discrimination of tree-ring cellulose (Δ13Ci).
Results
We find spatial autocorrelation for TRWi and Δ13Ci extending over up to 1,000 km among forest stands. However, growth synchrony is not uniform across Europe, but increases along a latitudinal gradient concurrent with decreasing temperature and evapotranspiration. Latitudinal relationships between TRWi and Δ13Ci (changing from negative to positive southwards) point to drought impairing carbon uptake via stomatal regulation for water saving occurring at forests below 60°N in continental Europe. A rise in forest growth synchrony over the 20th century together with increasingly positive relationships between TRWi and Δ13Ci indicate intensifying drought impacts on tree performance. These effects are noticeable in drought-prone biomes (Mediterranean, temperate and cold continental).
Main conclusions
At the turn of this century, convergence in growth synchrony across European forest ecosystems is coupled with coordinated warming-induced drought effects on leaf physiology and tree growth spreading northwards. Such a tendency towards exacerbated moisture-sensitive growth and physiology could override positive effects of enhanced leaf intercellular CO2 concentrations, possibly resulting in Europe-wide declines of forest carbon gain in the coming decades
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