1,007 research outputs found
The emission line near 1319 A in solar and stellar spectra
An emission line near 1319 A is one of the strongest unidentified lines in
the ultraviolet spectra of cool dwarf stars. In most line lists it is
identified as a transition in N I, although its intensity would then be
anomalous and the observed wavelength does not fit precisely that expected for
N I. The line is also observed in cool giant stars. The measured wavelength of
the line in stellar spectra is 1318.94 (+,- 0.01) A. Observations of giant
stars provide further evidence that this line is not due to N I. It is proposed
that this line is a decay from a previously unknown level in S I, which lies
above the first ionization limit. This is identified with the 3d singlet D (odd
parity) term. The previous tentative assignment of this term to the S I line at
1309.3 A then needs to be revised. The 1309.3 A line has been identified here
for the first time in an astrophysical source. The singlet D (odd parity) level
could, in principle, be populated by collisions from nearby autoionizing levels
that have large number-densities, through population by di-electronic capture.
Spin-orbit interaction with the autoionizing triplet D (odd parity) term might
also lead to di-electronic capture into the singlet D (odd parity) level. A
line at 1309.87 A observed in cool giant stars is identified as a transition in
P II, pumped by the O I resonance lines.Comment: 9 pages, 3 figures, to be published in Monthly Notices of the Royal
Astronomical Societ
Building an Argument for the Use of Science Fiction in HCI Education
Science fiction literature, comics, cartoons and, in particular, audio-visual
materials, such as science fiction movies and shows, can be a valuable addition
in Human-computer interaction (HCI) Education. In this paper, we present an
overview of research relative to future directions in HCI Education, distinct
crossings of science fiction in HCI and Computer Science teaching and the
Framework for 21st Century Learning. Next, we provide examples where science
fiction can add to the future of HCI Education. In particular, we argue herein
first that science fiction, as tangible and intangible cultural artifact, can
serve as a trigger for creativity and innovation and thus, support us in
exploring the design space. Second, science fiction, as a means to analyze
yet-to-come HCI technologies, can assist us in developing an open-minded and
reflective dialogue about technological futures, thus creating a singular base
for critical thinking and problem solving. Provided that one is cognizant of
its potential and limitations, we reason that science fiction can be a
meaningful extension of selected aspects of HCI curricula and research.Comment: 6 pages, 1 table, IHSI 2019 accepted submissio
Modelling the chromosphere and transition region of Epsilon Eri (K2 V)
Measurements of ultraviolet line fluxes from Space Telescope Imaging
Spectrograph and Far-Ultraviolet Spectroscopic Explorer spectra of the K2-dwarf
Epsilon Eri are reported. These are used to develop new emission measure
distributions and semi-empirical atmospheric models for the chromosphere and
lower transition region of the star. These models are the most detailed
constructed to date for a main-sequence star other than the Sun. New ionisation
balance calculations, which account for the effect of finite density on
dielectronic recombination rates, are presented for carbon, nitrogen, oxygen
and silicon. The results of these calculations are significantly different from
the standard Arnaud & Rothenflug ion balance, particularly for alkali-like
ions. The new atmospheric models are used to place constraints on possible
First Ionisation Potential (FIP) related abundance variations in the lower
atmosphere and to discuss limitations of single-component models for the
interpretation of certain optically thick line fluxes.Comment: 22 pages, 9 figure
Inheritance of Evolved Glyphosate Resistance in a North Carolina Palmer Amaranth ( Amaranthus palmeri
Inheritance of glyphosate resistance in a Palmer amaranth biotype from North Carolina was studied. Glyphosate rates for 50% survival of glyphosate-resistant (GR) and glyphosate-susceptible (GS) biotypes were 1288 and 58 g ha−1, respectively. These values for F1 progenies obtained from reciprocal crosses (GR×GS and GS×GR were 794 and 501 g ha−1, respectively. Dose response of F1 progenies indicated that resistance was not fully dominant over susceptibility. Lack of significant differences between dose responses for reciprocal F1 families suggested that genetic control of glyphosate resistance was governed by nuclear genome. Analysis of F1 backcross (BC1F1) families showed that 10 and 8 BC1F1 families out of 15 fitted monogenic inheritance at 2000 and 3000 g ha−1 glyphosate, respectively. These results indicate that inheritance of glyphosate resistance in this biotype is incompletely dominant, nuclear inherited, and might not be consistent with a single gene mechanism of inheritance. Relative 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) copy number varied from 22 to 63 across 10 individuals from resistant biotype. This suggested that variable EPSPS copy number in the parents might be influential in determining if inheritance of glyphosate resistance is monogenic or polygenic in this biotype
Physiology of Glyphosate-Resistant and Glyphosate-Susceptible Palmer Amaranth ( Amaranthus palmeri
Glyphosate-resistant (GR) biotypes of Palmer amaranth are now commonly found across the southern United States. Experiments were conducted to characterize physiological differences between a GR biotype and a glyphosate-susceptible (GS) biotype from North Carolina. The GR biotype had an 18-fold level of resistance based upon rates necessary to reduce shoot fresh weight 50%. Shikimate accumulated in both biotypes following glyphosate application, but greater concentrations were found in GS plants. Absorption and translocation of 14C-glyphosate were studied in both biotypes with and without an overspray with commercial glyphosate potassium salt (840 g ae ha−1) immediately prior to 14C-glyphosate application. Greater absorption was noted 6 h after treatment (HAT) in GS compared with GR plants, but no differences were observed at 12 to 72 HAT. Oversprayed plants absorbed 33 and 61% more 14C by 48 and 72 HAT, respectively, than plants not oversprayed. 14C distribution (above treated leaf, below treated leaf, roots) was similar in both biotypes. Together, these results suggest that resistance in this biotype is not due to an altered target enzyme or translocation but may be in part due to the rate of glyphosate absorption. These results also are consistent with resistance being due to increased gene copy number for the target enzyme
Detection of magnetic dipole lines of Fe XII in the ultraviolet spectrum of the dwarf star Epsilon Eri
We report observations of the dwarf star Epsilon Eri (K2 V) made with the
Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope
(HST). The high sensitivity of the STIS instrument has allowed us to detect the
magnetic dipole transitions of Fe XII at 1242.00A and 1349.38A for the first
time in a star other than the Sun. The width of the stronger line at 1242.00A
has also been measured; such measurements are not possible for the permitted
lines of Fe XII in the extreme ultraviolet. To within the accurcy of the
measurements, the N V and the Fe XII lines occur at their rest wavelengths.
Electron densities and line widths have been measured from other transition
region lines. Together, these can be used to investigate the non-thermal energy
flux in the lower and upper transition region, which is useful in constraining
possible heating processes. The Fe XII lines are also present in archival STIS
spectra of other G/K-type dwarfs.Comment: 12 pages, 4 figures, submitted to MNRAS letters (11 Jan 2001
Response of Herbicide-Resistant Palmer Amaranth ( Amaranthus palmeri
Palmer amaranth is a very problematic weed in several crops in the southern USA due to its competitive ability and resistance to herbicides representing different mechanisms of action. Variation in growth and subsequent interference of North Carolina Palmer amaranth accessions has not been examined. A greenhouse experiment determined response of 15 North Carolina Palmer amaranth accessions to drought stress beginning 15 days after seedling emergence (DAE) for a duration of 3, 5, 7, and 9 days. Following exposure to drought, plants were grown under optimal moisture conditions until harvest at 30 DAE. Five accessions each of glyphosate-resistant (GR), acetolactate synthase inhibitor-resistant (ALSR), and acetolactate synthase inhibitor-susceptible and glyphosate-susceptible (ALSS/GS) were compared. Variation in response to drought stress, based on height and dry weight reduction relative to nonstressed controls, was noted among accessions. Stress for 3 or more days affected height and dry weight. Height and dry weight of GR and ALSR accession groups were reduced less by drought than the ALSS/GS accession group. Results suggest a possible relationship between herbicide resistance and ability of Palmer amaranth to withstand drought stress and thus a possible competitive advantage for resistant accessions under limited moisture availability
Interference of Selected Palmer Amaranth ( Amaranthus palmeri
Palmer amaranth (Amaranthus palmeri S. Wats.) has become difficult to control in row crops due to selection for biotypes that are no longer controlled by acetolactate synthase inhibiting herbicides and/or glyphosate. Early season interference in soybean [Glycine max (L.) Merr.] for 40 days after emergence by three glyphosate-resistant (GR) and three glyphosate-susceptible (GS) Palmer amaranth biotypes from Georgia and North Carolina was compared in the greenhouse. A field experiment over 2 years compared season-long interference of these biotypes in soybean. The six Palmer amaranth biotypes reduced soybean height similarly in the greenhouse but did not affect soybean height in the field. Reduction in soybean fresh weight and dry weight in the greenhouse; and soybean yield in the field varied by Palmer amaranth biotypes. Soybean yield was reduced 21% by Palmer amaranth at the established field density of 0.37 plant m−2. When Palmer amaranth biotypes were grouped by response to glyphosate, the GS group reduced fresh weight, dry weight, and yield of soybean more than the GR group. The results indicate a possible small competitive disadvantage associated with glyphosate resistance, but observed differences among biotypes might also be associated with characteristics within and among biotypes other than glyphosate resistance
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A booster dose enhances immunogenicity of the COVID-19 vaccine candidate ChAdOx1 nCoV-19 in aged mice.
BACKGROUND: The spread of SARS-CoV-2 has caused a worldwide pandemic that has affected almost every aspect of human life. The development of an effective COVID-19 vaccine could limit the morbidity and mortality caused by infection and may enable the relaxation of social-distancing measures. Age is one of the most significant risk factors for poor health outcomes after SARS-CoV-2 infection; therefore, it is desirable that any new vaccine candidates elicit a robust immune response in older adults. METHODS: Here, we use in-depth immunophenotyping to characterize the innate and adaptive immune response induced upon intramuscular administration of the adenoviral vectored ChAdOx1 nCoV-19 (AZD-1222) COVID-19 vaccine candidate in mice. FINDINGS: A single vaccination generates spike-specific Th1 cells, Th1-like Foxp3+ regulatory TÂ cells, polyfunctional spike-specific CD8+ TÂ cells. and granzyme-B-producing CD8 effectors. Spike-specific IgG and IgM are generated from both the early extrafollicular antibody response and the T follicular helper cell-supported germinal center reaction, which is associated with the production of virus-neutralizing antibodies. A single dose of this vaccine generated a similar type of immune response in aged mice but of a reduced magnitude than in younger mice. We report that a second dose enhances the immune response to this vaccine in aged mice. CONCLUSIONS: This study shows that ChAdOx1 nCoV-19 induces both cellular and humoral immunity in adult and aged mice and suggests a prime-boost strategy is a rational approach to enhance immunogenicity in older persons. FUNDING: This study was supported by BBSRC, Lister institute of Preventative Medicine, EPSRC VaxHub, and Innovate UK
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