Fundamental (f) Oscillations in a Magnetically Coupled Solar Interior-Atmosphere System:An Analytical Approach

Solar fundamental (f) acoustic mode oscillations are investigated analytically in a magnetohydrodynamic (MHD) model. The model consists of three layers in planar geometry, representing the solar interior, the magnetic atmosphere, and a transitional layer sandwiched between them. Since we focus on the fundamental mode here, we assume the plasma is incompressible. A horizontal, canopy-like, magnetic field is introduced to the atmosphere, in which degenerated slow MHD waves can exist. The global (f-mode) oscillations can couple to local atmospheric Alfvén waves, resulting, e.g., in a frequency shift of the oscillations. The dispersion relation of the global oscillation mode is derived, and is solved analytically for the thin-transitional layer approximation and for the weak-field approximation. Analytical formulae are also provided for the frequency shifts due to the presence of a thin transitional layer and a weak atmospheric magnetic field. The analytical results generally indicate that, compared to the fundamental value (ω=gk), the mode frequency is reduced by the presence of an atmosphere by a few per cent. A thin transitional layer reduces the eigen-frequencies further by about an additional hundred microhertz. Finally, a weak atmospheric magnetic field can slightly, by a few percent, increase the frequency of the eigen-mode. Stronger magnetic fields, however, can increase the f-mode frequency by even up to ten per cent, which cannot be seen in observed data. The presence of a magnetic atmosphere in the three-layer model also introduces non-permitted propagation windows in the frequency spectrum; here, f-mode oscillations cannot exist with certain values of the harmonic degree. The eigen-frequencies can be sensitive to the background physical parameters, such as an atmospheric density scale-height or the rate of the plasma density drop at the photosphere. Such information, if ever observed with high-resolution instrumentation and inverted, could help to gain further insight into solar magnetic structures by means of solar magneto-seismology, and could provide further insight into the role of magnetism in solar oscillations

Global oscillations in a magnetic solar model:II Oblique propagation

The coupling of solar global acoustic oscillations to a magnetised solar atmosphere is studied here. The solar interior – atmosphere interface is modelled by a non-magnetic polytrope interior overlayed by a planar atmosphere embedded in non-uniform horizontal atmospheric magnetic field. Pintér & Goossens (1999, A&A, 347, 321) showed that parallel propagating acoustic waves can couple resonantly to local magnetohydrodynamic (MHD) slow continuum modes only. In general, global acoustic modes can, however, propagate in arbitrary directions with respect to local atmospheric fields giving rise to an additional efficient coupling mechanism that has consequences on mode damping and atmospheric energetics. In this paper we study obliquely propagating global modes that can couple also to local MHD Alfvén continuum modes. The atmospheric magnetic effects on global mode frequencies are still much of a debate. In particular, the resulting frequency shifts and damping rates of global modes caused by the resonant interaction with both local Alfvén and slow waves are investigated. We found the coupling of global f and p modes and the Lamb mode, that penetrate into the magnetic solar atmosphere, will strongly depend on the direction of propagation with respect to the solar atmospheric magnetic field. These frequency shifts, as a function of the propagation direction, give us a further elegant tool and refinement method of local helioseismology techniques. Finally we briefly discuss the importance of studying obliquely propagating waves and discuss the results in the context of possible helioseismic observations

Tudásalapú természetesnyelv-feldolgozás

A 80-as évek óa két fő irányzat van a számítógépes nyelvészetben: a statisztikus megközelítést használó „felszíni technológiák”, valamint azok a próbálkozások, hogy a generatív nyelvelméletet mégiscsak használni lehessen. A z előző volt a sikeresebb, de a mondattan és főleg a jelentéstan területén n e m volt előrehaladás. A z általunk javasolt alternatíva olyan hibrid rendszer, amelyben különböző tudásfajtákat különböző eszközökkel kezelünk. A z „automatikus” folyamatokat, mint amilyen a beszédfelismerés, statisztikus eszközökkel modelláljuk, m í g a „tudatos” működéseket pedig, mint amilyenek a megértés és fogalmazás mélyebb szintjei, logikai eszközökkel, az ún. konstrukciós nyelvtan elméleti alapján, az abdukciónak nevezett okoskodást módszerrel

What have we learned from two-pore potassium channels? Their molecular configuration and function in the human heart

Two-pore domain potassium channels (K2P) control excitability, stabilize the resting membrane potential below firing threshold, and accelerate repolarisation in different cells. Until now, fifteen different genes for the six K2P channel subfamily were cloned. The pore-forming part is translated from two genes and they are built up from a dimer of two two-unit transmembrane domains functioning with a wide spectrum of physiological profiles. K2P ion channels were discovered in the last two decades and gave novel opportunity to recognize the complex molecular mechanism of the potassium ion flux, and may lead to the design of individual drug targeting in the future. In this review, we summarise the structure, function, channelopathies and pharmacological silhouette of the two-pore potassium channels in the human tissues. In addition, we present the computer model of the partially reconstructed wild type K2P1/TWIK1 lacking the intracellular C and N terminal loop

Szoláris és asztrofizikai magnetohidrodinamika = Solar and astrophysical magnetohydrodynamics

A pályázat az ELTE Csillagászati Tanszékén működő szoláris magneto-hidrodinamikai kutatócsoport működésének fő finanszírozási forrása. Itt két fontos eredményünket emeljük ki a 2003-2006 évekből. A világon elsőként kifejlesztett gyors tachoklínamodellünket (ld. a T032462 OTKA pályázat zárójelentését) továbbfejlesztettük és realisztikusabbá tettük. A tachoklína a napbelső egy fontos rétege, mely mai elképzelésünk szerint a dinamó székhelye. Modellünkben a tachoklína eléggé turbulens ahhoz, hogy a Nap oszcilláló mágneses tere azt egészében áthassa, s így meghatározza annak dinamikáját. Új mechanizmust javasoltunk a Nap kromoszférájában látható szpikulák eredetére. A mechanizmus lényege. hogy a mágneses hálózat vékony erővonalcsövei felfelé terelik az ötperces oszcillációkat. | The project has been the principal source of funding for the solar and astrophysical research group at the Department of Astronomy of Eötvös University. In this summary we just mention two key results of our research. We have further developed our model for the so-called fast solar tachocline. The tachocline is an important layer in the solar interior, thought to be the seat of the dynamo. In our model, this layer is assumed to be turbulent enough to allow penetration of the overlying oscillatory magnetic field into much of the tachocline, controlling its dynamics. A new mechanism was proposed for the origin of spicules in the solar chromomosphere. The mechanism is based on upward channeling of photospheric 5-minute oscillations by the tilted magnetic network tubes

Expression of Tight Junction Components in Hepatocyte-Like Cells Differentiated from Human Embryonic Stem Cells

Human embryonic stem cells can be differentiated in vitro into a wide variety of progeny cells by addition of different morphogens and growth factors. Our aim was to monitor the expression pattern of tight junction (TJ) components and various cellular markers during differentiation of stem cell lines toward the hepatic lineage. Human embryonic stem cell lines (HUES1, HUES9) were differentiated into endoderm-like cells, and further differentiated to hepatocyte-like cells. Gene expressions of Oct3/4, Nanog, alpha-fetoprotein, albumin, cytokeratins (CK-7, CK-8, CK-18, CK-19), ATP-binding cassette (ABC) transporters (ABCC2, ABCC7, ABCG2), and various TJ components, including claudin-1, claudin-4, claudin-5, claudin-7, and tricellulin, as well as an extracellular matrix component, agrin were monitored during hepatic differentiation by real-time quantitative PCR. The differentiated cells exhibit epithelial morphology and functional assessments similar to that of hepatocytes. The expression level of stem cell marker genes (Oct3/4 and Nanog) significantly and gradually decreased, while liver-associated genes (alpha-fetoprotein, albumin) reached their highest expression at the end of the differentiation. The endoderm-like cells expressed claudin-1, which declined eventually. The expression levels of cholangiocyte markers including claudin-4, CK-7, CK-19, and agrin gradually increased and reached their highest level at the final stage of differentiation. In contrast, these cells did not express notable level of claudin-7, CK-8 and tricellulin. The marker set used for monitoring differentiation revealed both hepatocyte and cholangiocyte characteristics of the differentiated cells at the final stage. This is the first report describing the expression level changes of various TJ components, and underlining their importance in hepatic differentiation. © 2015 Arányi Lajos Foundatio

Mapping Fluorescence Enhancement of Plasmonic Nanorod Coupled Dye Molecules

Plasmonically enhanced fluorescence is a widely studied and applied phenomenon, however only a comparative theoretical and experimental analyses of coupled fluorophores and plasmonic nanoresonators makes it possible to uncover, how this phenomenon can be controlled. A numerical optimization method was applied to design configurations that are capable of resulting in an enhancement of excitation and emission, moreover of both phenomena simultaneously in coupled Cy5 dye molecule and gold nanorod systems. Parametric sensitivity studies revealed, how the fluorescence enhancement depends on the molecule's location, distance and orientation. Coupled systems designed for simultaneous improvement exhibited the highest (intermediate directional) total fluorescence enhancement, which is accompanied by intermediate sensitivity to the molecule's parameters, except the location and orientation sensitivity at the excitation wavelength. Gold nanorods with a geometry corresponding to the predicted optimal configurations were synthesized, and DNA strands were used to control the Cy5 dye molecule distance from the nanorod surface via hybridization of the Cy5-labelled oligonucleotide. State-of-the-art dSTORM microscopy was used to accomplish a proof-of-concept experimental demonstration of the theoretically predicted (directional) total fluorescence enhancement. The measured fluorescence enhancement was in good agreement with theoretical predictions, thus providing a complete kit to design and prepare coupled nanosystems exhibiting plasmonically enhanced fluorescence.Comment: 15 pages, 7 figure

Evaluation of entomopathogenic bacteria and fungi for the control of the western corn rootworm

Untersuchungen entomopathogener Bakterien und Pilze für die Bekämpfung des Westlichen Maiswurzelbohrer