scholarly journals The rapidly oscillating Ap star γ Equ: linear polarization as an enhanced pulsation diagnostic?

2021 ◽  
Vol 508 (1) ◽  
pp. L17-L21
Author(s):  
S Hubrig ◽  
S P Järvinen ◽  
I Ilyin ◽  
K G Strassmeier ◽  
M Schöller
Keyword(s):  
Magnetic Field ◽  
Polarized Light ◽  
Transverse Magnetic ◽  
Spectral Lines ◽  
Short Time Scale ◽  
Pulsation Period ◽  
Transversal Field ◽  
Short Time ◽  
The Impact ◽  
Landé Factors

ABSTRACT We present the first short time-scale observations of the rapidly oscillating Ap (roAp) star γ Equ in linear polarized light obtained with the Potsdam Echelle Polarimetric and Spectroscopic Instrument installed at the Large Binocular Telescope. These observations are used to search for pulsation variability in Stokes Q and U line profiles belonging to different elements. The atmospheres of roAp stars are significantly stratified with spectral lines of different elements probing different atmospheric depths. roAp stars with strong magnetic fields, such as γ Equ with a magnetic field modulus of 4 kG and a pulsation period of 12.21 min, are of special interest because the effect of the magnetic field on the structure of their atmospheres can be studied with greatest detail and accuracy. Our results show that we may detect changes in the transversal field component in Fe i and rare earth element lines possessing large second-order Landé factors. Such variability can be due to the impact of pulsation on the transverse magnetic field, causing changes in the obliquity angles of the magnetic force lines. Further studies of roAp stars in linear polarized light and subsequent detailed modelling are necessary to improve our understanding of the involved physics.

scholarly journals The Polar Fields and Time Fluctuations of the General Magnetic Field of the Sun

1971 ◽  
Vol 43 ◽  
pp. 675-695 ◽  
Author(s):  
A. B. Severny
Keyword(s):  
Magnetic Field ◽  
Close Agreement ◽  
Present Knowledge ◽  
Short Time Scale ◽  
The Sun ◽  
Statistical Nature ◽  
General Magnetic Field ◽  
Short Period ◽  
The Mean ◽  
Short Time

In an attempt to summarize the present knowledge on the general magnetic field (gmf) of the Sun we pointed out the fine structure and the statistical nature of the gmf as one of its most important properties. The dipole-like behaviour of the mean polar field strengths is combined sometimes (since 1964) with a bias of the S-polarity flux for both poles. Highly uneven distribution of gmf with latitude and longitude, the disappearance of gmf at the South pole for months, and short period, almost synchronous at both poles, variations in the sign of gmf are pointed out. The fluctuations with time of the mean magnetic field of the Sun seen as a star (as well as mf at different latitudes) shows periodicity connected with the rotation of the Sun and very close agreement with the fluctuations of the interplanetary field (sector structure). The effect of faster rotation of N-polarities as compared with S-polarities as well as the bias of mean solar as well as interplanetary S-polarity fields are also pointed out. The possibility of short time-scale (hours) intrinsic changes in the local pattern of gmf is demonstrated.

Experimental evaluation of the impact of low tesla transverse magnetic field on dose distribution in presence of tissue interfaces

2018 ◽  
Vol 53 ◽  
pp. 80-85 ◽  
Author(s):  
Davide Cusumano ◽  
Stefania Teodoli ◽  
Francesca Greco ◽  
Andrea Fidanzio ◽  
Luca Boldrini ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Transverse Magnetic Field ◽  
Dose Distribution ◽  
Experimental Evaluation ◽  
Transverse Magnetic ◽  
The Impact ◽  
Tissue Interfaces

scholarly journals Mechanistic modelling of COVID-19 and the impact of lockdowns on a short-time scale

PLoS ONE ◽  
2021 ◽  
Vol 16 (10) ◽  
pp. e0258084
Author(s):  
Danish A. Ahmed ◽  
Ali R. Ansari ◽  
Mudassar Imran ◽  
Kamal Dingle ◽  
Michael B. Bonsall
Keyword(s):  
Time Scale ◽  
Population Distribution ◽  
Contact Process ◽  
Time Lag ◽  
Service Industries ◽  
Spatial Proximity ◽  
Short Time Scale ◽  
Susceptible Host ◽  
Short Time ◽  
The Impact

Background To mitigate the spread of the COVID-19 coronavirus, some countries have adopted more stringent non-pharmaceutical interventions in contrast to those widely used. In addition to standard practices such as enforcing curfews, social distancing, and closure of non-essential service industries, other non-conventional policies also have been implemented, such as the total lockdown of fragmented regions, which are composed of sparsely and highly populated areas. Methods In this paper, we model the movement of a host population using a mechanistic approach based on random walks, which are either diffusive or super-diffusive. Infections are realised through a contact process, whereby a susceptible host is infected if in close spatial proximity of the infectious host with an assigned transmission probability. Our focus is on a short-time scale (∼ 3 days), which is the average time lag time before an infected individual becomes infectious. Results We find that the level of infection remains approximately constant with an increase in population diffusion, and also in the case of faster population dispersal (super-diffusion). Moreover, we demonstrate how the efficacy of imposing a lockdown depends heavily on how susceptible and infectious individuals are distributed over space. Conclusion Our results indicate that on a short-time scale, the type of movement behaviour does not play an important role in rising infection levels. Also, lock-down restrictions are ineffective if the population distribution is homogeneous. However, in the case of a heterogeneous population, lockdowns are effective if a large proportion of infectious carriers are distributed in sparsely populated sub-regions.

scholarly journals Experimental tests of the quantum property of protein folding

2016 ◽  
Author(s):  
Liaofu Luo
Keyword(s):  
Protein Folding ◽  
Conformational Changes ◽  
Experimental Tests ◽  
Spectral Lines ◽  
Short Time Scale ◽  
Quantum Property ◽  
Folding Rate ◽  
Arrhenius Temperature Dependence ◽  
Short Time ◽  
Arrhenius Temperature

Experimental tests on the quantum property of protein folding are discussed. It includes: the test of the instantaneousness of torsion transition through observation of protein structural change in a short time scale of microsecond; the test of non-Arrhenius temperature dependence of protein folding rate and other biomolecular conformational changes; and the search for the narrow spectral lines of the protein photo-folding.

scholarly journals Phages associated with horses provide new insights into the dominance of lateral gene transfer in virulent bacteriophages evolution in natural systems

2019 ◽  
Author(s):  
V.V. Babenko ◽  
A.K. Golomidova ◽  
P.A. Ivanov ◽  
M.A. Letarova ◽  
E.E. Kulikov ◽  
...  
Keyword(s):  
Time Scale ◽  
Natural Habitat ◽  
Local Population ◽  
Point Mutations ◽  
Major Effect ◽  
Model Systems ◽  
Laboratory Model ◽  
Short Time Scale ◽  
Short Time ◽  
The Impact

AbstractTailed bacteriophages (Caudovirales order) are omnipresent on our planet. Their impressive ecological and evolutionary success largely relies on the bacteriophage potential to adapt to great variety of the environmental conditions found in the Biosphere. It is believed that the adaptation of bacteriophages, including short time scale adaptation, is achieved almost exclusively via the (micro)evolution processes. In order to analyze the major mechanisms driving adaptation of phage genomes in a natural habitat we used comparative genomics of G7C-like coliphage isolates obtained during 7 years period from the feces of the horses belonging to a local population. The data suggest that even at this relatively short time scale the impact of various recombination events overwhelms the impact of the accumulation of point mutations. The access to the large pool of the genes of a complex microbial and viral community of the animal gut had major effect on the evolutionary trajectories of these phages. Thus the “real world” bacteriophage evolution mechanisms may differ significantly from those observed in the simplified laboratory model systems.

scholarly journals Investigations of space magnetism at the Crimean Astrophysical Observatory. II. Direct spectropolarimetric measurements of stellar magnetic fields

2020 ◽  
Vol 1 (2) ◽  
pp. 26-36
Author(s):  
Sergei Plachinda ◽  
Varvara Butkovskaya
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Spectral Lines ◽  
Crimean Astrophysical Observatory ◽  
Scientific School ◽  
Pulsation Period ◽  
Echelle Spectrograph ◽  
Direct Measurements ◽  
Stellar Magnetic Fields ◽  
The Magnetic Field

A research on stellar magnetism in Crimea was initiated by pioneer works of A.B. Severny, V.E. Stepanov, and D.N. Rachkovsky. Today, the study of stellar magnetic fields is a key field of research at the Crimean Astrophysical Observatory (CrAO). The 2.6 m Shajn telescope equipped with the echelle spectrograph ESPL, CCD, and Stokesmeter (a circular polarization analyzer) allows us to study the magnetic field of bright stars up to 5m–6m. The Single Line (SL) technique is developed for measuring magnetic fields at CrAO. This technique is based on the calculation of the Zeeman effect in individual spectral lines. A key advantage of the SL technique is its ability to detect local magnetic fields on the surface of stars. Many results in the field of direct measurements of stellar magnetic fields were obtained at CrAO for the first time. In particular, the magnetic field on supergiants (ǫ Gem), as well as on a number of subgiants, giants, and bright giants was first detected. This, and investigations of other authors, confirmed the hypothesis that a magnetic field is generated at all the stages of evolution of late-type stars, including the stage of star formation. The emergence of large magnetic flux tubes at the surface of stars of V-IV-III luminosity classes (61 Cyg A, β Gem, β Aql) was first registered. In subgiants, the magnetic field behavior with the activity cycle was first established for β Aql. Using the long-term Crimean spectroscopic and spectropolarimetric observations of α Lyr, the 22-year variability cycle of the star, supposedly associated with meridional flows, is confirmed. Magnetic field variability with the pulsation period was first detected for different types of pulsating variables: the classical Cepheid β Aql, the low-amplitude β Cep-type variable γ Peg, and others. In this review we cover more than a half-century history of the formation of the Crimean scientific school for high-precision direct measurements of stellar magnetic fields.

scholarly journals Observations of the Two-Level Structure of Sunspot Magnetic Fields

1971 ◽  
Vol 43 ◽  
pp. 231-234
Author(s):  
H. I. Abdussamatov
Keyword(s):  
Magnetic Field ◽  
Fine Structure ◽  
Level Structure ◽  
Field Structure ◽  
Short Time Scale ◽  
Sunspot Umbra ◽  
Magnetic Field Structure ◽  
Spectroscopic Information ◽  
Short Time ◽  
The Magnetic Field

Inhomogeneity of magnetic field structure, ‘granulation’ in sunspot umbrae and fine structure of the Evershed motions lead to the conclusion that the sunspot umbra is composed of magnetic ropes (or plaits) with dimensions near the limit of resolution. Progress in the study of these ropes is closely connected with the possibility of obtaining extensive spectroscopic information about some selected regions on the solar disc. It is extremely interesting to obtain a picture of short-time-scale variations of the magnetic field strength and the radial velocity field in connection with the transfer of energy from the photosphere to the upper layers of the solar atmosphere (chromosphere, corona).

Short-Time-Scale Thermal Mapping of Microdevices Using a Scanning Thermoreflectance Technique

1998 ◽  
Vol 120 (2) ◽  
pp. 306-313 ◽  
Author(s):  
Y. S. Ju ◽  
K. E. Goodson
Keyword(s):  
Temperature Distribution ◽  
Time Scale ◽  
Silicon On Insulator ◽  
Temperature Fields ◽  
Scanning Laser ◽  
Transient Temperature ◽  
Drift Region ◽  
Short Time Scale ◽  
Short Time ◽  
The Impact

The performance and reliability of microdevices can be strongly influenced by the peak temperature rise and spatial temperature distribution during brief electrical overstress (EOS) phenomena, which can occur at sub-microsecond time scales. The present study investigates short-time-scale laser reflectance thermometry of micro devices by examining the impact of passivation overlayers on the thermoreflectance signal and by demonstrating a calibration method suitable for metallization. This manuscript also describes a scanning laser thermometry facility that captures temperature fields in microdevices with 10 ns temporal resolution and 1 μm spatial resolution. The facility combines scanning laser optics with electrical stressing capability to allow simultaneous interrogation of the thermal and electrical behavior of devices. Data show the transient temperature distribution along the drift region of silicon-on-insulator (SOI) power transistors and along metal interconnects subjected to brief electrical stresses. The theory and experimental capability developed in this study are useful for studying short-time-scale thermal phenomena in microdevices and verifying models employed for their simulation.

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