57 research outputs found
Two different charge-separation pathways in photosystem II
Charge separation is an essential step in the conversion of solar energy into chemical energy in photosynthesis. To investigate this process, we performed transient absorption experiments at 77 K with various excitation conditions on the isolated Photosystem II reaction center preparations from spinach. The results have been analyzed by global and target analysis and demonstrate that at least two different excited states, (Ch
Revival of the magnetar PSR J1622-4950: observations with MeerKAT, Parkes, XMM-Newton, Swift, Chandra, and NuSTAR
New radio (MeerKAT and Parkes) and X-ray (XMM-Newton, Swift, Chandra, and
NuSTAR) observations of PSR J1622-4950 indicate that the magnetar, in a
quiescent state since at least early 2015, reactivated between 2017 March 19
and April 5. The radio flux density, while variable, is approximately 100x
larger than during its dormant state. The X-ray flux one month after
reactivation was at least 800x larger than during quiescence, and has been
decaying exponentially on a 111+/-19 day timescale. This high-flux state,
together with a radio-derived rotational ephemeris, enabled for the first time
the detection of X-ray pulsations for this magnetar. At 5%, the 0.3-6 keV
pulsed fraction is comparable to the smallest observed for magnetars. The
overall pulsar geometry inferred from polarized radio emission appears to be
broadly consistent with that determined 6-8 years earlier. However, rotating
vector model fits suggest that we are now seeing radio emission from a
different location in the magnetosphere than previously. This indicates a novel
way in which radio emission from magnetars can differ from that of ordinary
pulsars. The torque on the neutron star is varying rapidly and unsteadily, as
is common for magnetars following outburst, having changed by a factor of 7
within six months of reactivation.Comment: Published in ApJ (2018 April 5); 13 pages, 4 figure
The 1.28 GHz MeerKAT DEEP2 Image
We present the confusion-limited 1.28 GHz MeerKAT DEEP2 image covering one qb » ¢ 68 FWHM primarybeam area with θ = 7 6 FWHM resolution and s = m - n 0.55 0.01 Jy beam 1 rms noise. Its J2000 center position
α = 04h 13m 26 4, δ = −80° 00′ 00″ was selected to minimize artifacts caused by bright sources. We introduce
the new 64-element MeerKAT array and describe commissioning observations to measure the primary-beam
attenuation pattern, estimate telescope pointing errors, and pinpoint (u, v) coordinate errors caused by offsets in
frequency or time. We constructed a 1.4 GHz differential source count by combining a power-law count fit to the
DEEP2 confusion P(D) distribution from 0.25 to 10 μJy with counts of individual DEEP2 sources between 10 μJy
and 2.5 mJy. Most sources fainter than S ∼ 100 μJy are distant star-forming galaxies (SFGs) obeying the far-IR/
radio correlation, and sources stronger than 0.25 μJy account for ∼93% of the radio background produced by
SFGs. For the first time, the DEEP2 source count has reached the depth needed to reveal the majority of the star
formation history of the universe. A pure luminosity evolution of the 1.4 GHz local luminosity function consistent
with the Madau & Dickinson model for the evolution of SFGs based on UV and infrared data underpredicts our
1.4 GHz source count in the range -5 log Jy 4 [ ( )] S
The MeerKAT Galaxy Cluster Legacy Survey: I. Survey overview and highlights
Please abstract in the article.The South African Radio Astronomy Observatory (SARAO), the National Research Foundation (NRF), the National Radio Astronomy Observatory, US National Science Foundation, the South African Research Chairs Initiative of the DSI/NRF, the SARAO HCD programme, the South African Research Chairs Initiative of the Department of Science and Innovation.http://www.aanda.orghj2022Physic
The SARAO MeerKAT 1.3 GHz Galactic Plane Survey
We present the SARAO MeerKAT Galactic Plane Survey (SMGPS), a 1.3 GHz continuum survey of almost half of the Galactic Plane (251○ ≤l ≤ 358○ and 2○ ≤l ≤ 61○ at |b| ≤ 1
5). SMGPS is the largest, most sensitive and highest angular resolution 1 GHz survey of the Plane yet carried out, with an angular resolution of 8″ and a broadband RMS sensitivity of ∼10–20 μJy beam−1. Here we describe the first publicly available data release from SMGPS which comprises data cubes of frequency-resolved images over 908–1656 MHz, power law fits to the images, and broadband zeroth moment integrated intensity images. A thorough assessment of the data quality and guidance for future usage of the data products are given. Finally, we discuss the tremendous potential of SMGPS by showcasing highlights of the Galactic and extragalactic science that it permits. These highlights include the discovery of a new population of non-thermal radio filaments; identification of new candidate supernova remnants, pulsar wind nebulae and planetary nebulae; improved radio/mid-IR classification of rare Luminous Blue Variables and discovery of associated extended radio nebulae; new radio stars identified by Bayesian cross-matching techniques; the realisation that many of the largest radio-quiet WISE H II region candidates are not true H II regions; and a large sample of previously undiscovered background H I galaxies in the Zone of Avoidance
Biotechnological approaches for plant viruses resistance: from general to the modern RNA silencing pathway
The influence of long-term treatment with megestrol acetate or tamoxifen on the nutritional status of advanced breast cancer patients
UV-microscopic studies on the vacuolar changes caused by the flavone “aglycone” isovitexin inSilene pratensis plants
Seventeen Projects Carried Out by Students Designing for and with Disabled Children: Identifying Designers' Difficulties During the Whole Design Process
International audienceThis article aims to identify the difficulties that may arise when designing assistive devices for disabled children. Seventeen design projects involving disabled children, engineering students, and special schools were analysed. A content analysis of the design reports was performed. For this purpose, a coding scheme was built based on a review of the literature. This was then improved through direct observation of the design reports. The coding scheme includes 17 categories, 7 of which stemmed from the direct observation of the reports: these 7 categories cover newly identified difficulties. Three important aspects emerged from the content analysis: (1) Difficulties identified in the literature arose in the context of this study. (2) Among the difficulties related to the practical barriers of involving disabled children, one new difficulty in particular was identified through the study, that is, that of partnering with special schools. (3) While existing literature focuses on the practical barriers, the results of this study show that not all difficulties are related to these barriers. In fact, understanding user needs proves to be especially difficult when the product to be designed targets several different disabled users
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