2,465 research outputs found
Propagating Waves Transverse to the Magnetic Field in a Solar Prominence
We report an unusual set of observations of waves in a large prominence
pillar which consist of pulses propagating perpendicular to the prominence
magnetic field. We observe a huge quiescent prominence with the Solar Dynamics
Observatory (SDO) Atmospheric Imaging Assembly (AIA) in EUV on 2012 October 10
and only a part of it, the pillar, which is a foot or barb of the prominence,
with the Hinode Solar Optical Telescope (SOT) (in Ca II and H\alpha lines), Sac
Peak (in H\alpha, H\beta\ and Na-D lines), THEMIS ("T\'elescope
H\'eliographique pour l' Etude du Magn\'etisme et des Instabilit\'es Solaires")
with the MTR (MulTi-Raies) spectropolarimeter (in He D_3 line). The THEMIS/MTR
data indicates that the magnetic field in the pillar is essentially horizontal
and the observations in the optical domain show a large number of horizontally
aligned features on a much smaller scale than the pillar as a whole. The data
is consistent with a model of cool prominence plasma trapped in the dips of
horizontal field lines. The SOT and Sac Peak data over the 4 hour observing
period show vertical oscillations appearing as wave pulses. These pulses, which
include a Doppler signature, move vertically, perpendicular to the field
direction, along thin quasi-vertical columns in the much broader pillar. The
pulses have a velocity of propagation of about 10 km/s, a period about 300 sec,
and a wavelength around 2000 km. We interpret these waves in terms of fast
magneto-sonic waves and discuss possible wave drivers.Comment: Accepted for publication in The Astrophysical Journa
Distinct ultraviolet-signaling pathways in bean leaves. DNA damage is associated with ß-1,3-glucanase gene induction, but not with flavonoid formation
The enzyme beta-1,3-glucanase (betaGlu) was found to be strongly induced by ultraviolet (UV-B; 280-320 nm) radiation in primary leaves of French bean (Phaseolus vulgaris). This was demonstrated on the level of gene transcription, protein synthesis, and enzyme activity and was due to the expression of bean class I betaGlu (pGlu I). In contrast to other proteins of the family of pathogenesis-related proteins, the induction of betaGlu I by UV correlated with the formation of photoreversible DNA damage, i.e. Pyrimidine dimer formation. In conditions that allowed photorepair of this damage, betaGlu I induction was blocked. Therefore, UV-induced DNA damage seems to constitute a primary signal in the pathway leading to the induction of the betaGlu I gene(s). The induction was a local response because in partly irradiated leaves betaGlu I was selectively found in leaf parts exposed to UV. Although short wavelength UV (lambda 295 nm) as present in natural radiation was still effective. In contrast to UV induction of betaGlu I, the induction of flavonoids in bean leaves was optimally triggered by much more moderate fluences from the UV wavelength range no longer effective in betaGlu I induction. UV induction of the flavonoid pathway shows no correlation with DNA damage and thus should be mediated via a different signal transduction pathway
Open questions on prominences from coordinated observations by IRIS, Hinode, SDO/AIA, THEMIS, and the Meudon/MSDP
Context. A large prominence was observed on September 24, 2013, for three
hours (12:12 UT -15:12 UT) with the newly launched (June 2013) Interface Region
Imaging Spectrograph (IRIS), THEMIS (Tenerife), the Hinode Solar Optical
Telescope (SOT), the Solar Dynamic Observatory Atmospheric Imaging Assembly
(SDO/AIA), and the Multichannel Subtractive Double Pass spectrograph (MSDP) in
the Meudon Solar Tower. Aims. The aim of this work is to study the dynamics of
the prominence fine structures in multiple wavelengths to understand their
formation. Methods. The spectrographs IRIS and MSDP provided line profiles with
a high cadence in Mg II and in Halpha lines. Results. The magnetic field is
found to be globally horizontal with a relatively weak field strength (8-15
Gauss). The Ca II movie reveals turbulent-like motion that is not organized in
specific parts of the prominence. On the other hand, the Mg II line profiles
show multiple peaks well separated in wavelength. Each peak corresponds to a
Gaussian profile, and not to a reversed profile as was expected by the present
non-LTE radiative transfer modeling. Conclusions. Turbulent fields on top of
the macroscopic horizontal component of the magnetic field supporting the
prominence give rise to the complex dynamics of the plasma. The plasma with the
high velocities (70 km/s to 100 km/s if we take into account the transverse
velocities) may correspond to condensation of plasma along more or less
horizontal threads of the arch-shape structure visible in 304 A. The steady
flows (5 km/s) would correspond to a more quiescent plasma (cool and
prominence-corona transition region) of the prominence packed into dips in
horizontal magnetic field lines. The very weak secondary peaks in the Mg II
profiles may reflect the turbulent nature of parts of the prominence.Comment: 15 pages, 14 figure
Boronic Acid Derivatives Targeting HIV-1
A series of novel boronic acid derivatives containing either a pyrimidine or purine base was synthesized. The preparation involved the condensation of 4-bromobutyl boronic acid with the appropriate base. These acyclic nucleosides were designed as potential antiviral agents especially targeting the human immunodeficiency virus. Two analogues, 6-chloro-9-(4-dihydroxyborylbutyl)purine and 2,6-dichloro-9-(4-dihydroxyborylbutyl)purine, exhibited EC50 values of 7.7 µM and 0.99 µM, respectively, in an HIV-1 syncytial plaque reduction assay
Voltage control of magnetocrystalline anisotropy in ferromagnetic - semiconductor/piezoelectric hybrid structures
We demonstrate dynamic voltage control of the magnetic anisotropy of a
(Ga,Mn)As device bonded to a piezoelectric transducer. The application of a
uniaxial strain leads to a large reorientation of the magnetic easy axis which
is detected by measuring longitudinal and transverse anisotropic
magnetoresistance coefficients. Calculations based on the mean-field
kinetic-exchange model of (Ga,Mn)As provide microscopic understanding of the
measured effect. Electrically induced magnetization switching and detection of
unconventional crystalline components of the anisotropic magnetoresistance are
presented, illustrating the generic utility of the piezo voltage control to
provide new device functionalities and in the research of micromagnetic and
magnetotransport phenomena in diluted magnetic semiconductors.Comment: Submitted to Physical Review Letters. Updates version 1 to include a
more detailed discussion of the effect of strain on the anisotropic
magnetoresistanc
Comparison of Upper Extremity Physical Characteristics Between Adolescent Competitive Swimmers and Nonoverhead Athletes
Alterations to upper extremity physical characteristics of competitive swimmers (posture, range of motion [ROM], and subacromial-space distance) are commonly attributed to cumulative training load during a swimmer's competitive career. However, this accepted clinical belief has not been established in the literature. It is important to understand whether alterations in posture and associated physical characteristics occur as a result of sport training or factors other than swimming participation to better understand injury risk and possible interventions
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Retrospective Evaluations of Sequences: Testing the Predictions of a Memory-based Analysis
Retrospective evaluation (RE) of event sequences are known to be biased in various ways. The present paper presents a series of studies that examined the suggestion that the moments that are the most accessible in memory at the point of RE contribute to these biases. As predicted by this memory-based analysis, Experiment 1 showed that pleasantness ratings of word lists were biased by the presentation position of a negative item and by how easy the negative information was to retrieve. Experiment 2 ruled out the hypothesis that these findings were due to the dual nature of the task called upon. Experiment 3 further manipulated the memorability of the negative items—and corresponding changes in RE were as predicted. Finally, Experiment 4 extended the findings to more complex stimuli involving event narratives. Overall, the results suggest that assessments were adjusted based on the retrieval of the most readily available information
Deviations from plastic barriers in BiSrCaCuO thin films
Resistive transitions of an epitaxial BiSrCaCuO thin
film were measured in various magnetic fields (), ranging from 0
to 22.0 T. Rounded curvatures of low resistivity tails are observed in
Arrhenius plot and considered to relate to deviations from plastic barriers. In
order to characterize these deviations, an empirical barrier form is developed,
which is found to be in good agreement with experimental data and coincide with
the plastic barrier form in a limited magnetic field range. Using the plastic
barrier predictions and the empirical barrier form, we successfully explain the
observed deviations.Comment: 5 pages, 6 figures; PRB 71, 052502 (2005
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