AN INTERMEDIATE LUMINOSITY TRANSIENT IN NGC 300: THE ERUPTION OF A DUST-ENSHROUDED MASSIVE STAR

Soccer players often have a dominant (D) leg, which could influence the relative strength between the quadriceps and hamstrings. The hamstring-to-quadriceps (H:Q) ratio can be assessed on a dynamometer at various velocities to provide information on injury risk. To assess the concentric hamstrings and concentric quadriceps strength ratio (conventional H:Q ratio) assessed in D and nondominant (ND) legs at various speeds in male soccer players. A systematic literature search was completed from inception to 2020 in PubMed, Academic Search Ultimate, CINAHL, and SPORTDiscus. Keywords associated with the H:Q ratio were connected with terms for soccer players. Titles and abstracts were screened by 2 reviewers based on inclusion and exclusion criteria related to sex, playing level, language, and measurement. A total of 81 studies were reviewed and 17 studies (21%) were used. A meta-analysis with random effects modeling generated standardized mean differences with 95% CIs between legs and speeds. Level 3. A total of 38 cohorts were identified, with 14, 13, and 11 cohorts assessed at low, intermediate, and high velocities, respectively. The Quality Assessment Tool for Observational Cohort and Cross-sectional Studies from the National Institutes of Health was used. The mean H:Q ratio at low velocities was 59.8 ± 9.5% in D leg and 58.6 ± 9.9% in ND leg, 64.2 ± 10.7% (D) and 63.6 ± 11.3% (ND) at the intermediate velocity, and 71.9 ± 12.7% (D) and 72.8 ± 12.7% (ND) at the high velocity. Low, intermediate, and high velocities had small effects of 0.13, 0.10, and -0.06, respectively. Conventional H:Q ratios vary across velocities but did not differ between D and ND limbs in male soccer players. This study may provide the foundation to establish norms and clinically meaningful differences.

In front of the LMC molecular hydrogen is found in absorption near 0 km s -1 , being local disk gas, near +60 km s -1 in an intermediate velocity cloud, and near +120 km s -1 , being a high velocity halo cloud. The nature of the gas is discussed based on four Orfeus far UV spectra of LMC stars and including data from the ground and from the IUE satellite. The local gas is cool and, given a span of sight lines of only $2.5^\circ$, rather fluffy. The fractional abundance of H 2 varies from $\log f=\log [N({\rm H}_2)/(2\cdot N({\rm H}_2)+N(\rm{\ion{H}{i}}))]=-5.4$ to -3.3. Metal depletions (up to -1.7 dex for Fe) are typical for galactic disk gas. In the intermediate and high velocity gas an apparent underabundance of neutral oxygen points to an ionization level of the gas of about 90% . H 2 is detected in intermediate and high velocity gas towards HD 269546. In the intermediate velocity gas we find an H 2 column density of $\log(N)\simeq15.6$. The H 2 excitation indicates that the line of sight samples a cloud at a temperature below 150 K. Column densities are too small to detect the higher UV pumped excitation levels. The high velocity H 2 ($\log(N)\simeq15.6$) is highly excited and probably exposed to a strong radiation field. Its excitation temperature exceeds 1000 K. Due to the radial velocity difference between the halo gas and the Milky Way disk, the unattenuated disk radiation is available for H 2 excitation in the halo. We do not find evidence for an intergalactic origin of this gas; a galactic as well as a Magellanic Cloud origin is possible.

Bipolar and schizophrenic patients differ in patterns of visual motion discrimination

To investigate the dependence of velocity characteristics on spatiotemporal interactions the velocity selectivity of 15 geniculate and 72 cortical cells (areas 17 and 18) was examined with light and dark bars before and after masking all but the most sensitive part of the receptive field. The use of a 0.3 degree window proved effective in eliminating enough spatiotemporal interactions to abolish cortical direction selectivity. The same window improved the responsiveness at high velocities in only 26% of the cortical cells preferring low velocities and having a receptive field with nonoverlapping ON and OFF subregions. The remaining 74% showed various degrees of velocity-independent decrease in response amplitude. The only two geniculate cells that had a velocity upper cutoff lost this cutoff when tested with the mask. Cortical units preferring high velocities lost their responsiveness at high velocities in the mask condition, provided that their receptive fields contained nonoverlapping ON and OFF subregions. Cortical units, which responded best at intermediate velocities and which had receptive fields with nonoverlapping subregions, lost their sharp velocity tuning when tested with a mask. We conclude that inhibitory spatiotemporal interactions can account for the preference for low velocities in at most a quarter of the cells with nonoverlapping subregions. In contrast, facilitatory interactions seem to be important for cortical cells preferring high or intermediate velocities and having receptive fields with nonoverlapping subregions.

When the B type stars are classified, they are arranged into groups of differing luminosity at each spectral type by considering the strengths and shapes of lines which are sensitive to changes in pressure and to the extent of atmosphere. In the atmospheres of the stars of high luminosity, the pressure is lower than in the atmospheres of the stars of lower luminosity and the atmosphere is more extended. The most striking spectral features demonstrating this in B type spectra are the Balmer lines of hydrogen and the Hei lines. In main-sequence stars the Balmer lines have wide wings of a typical shape due to Stark effect. For a given spectral type, as the luminosity increases and the electron pressure in the atmosphere decreases, the Stark effect becomes less and the Balmer lines of hydrogen become narrower. In the most luminous stars, the supergiants, large-scale motions in the atmosphere dominate over Stark effect as a broadening agent, and the absorption lines have a bell shape rather than a sharp, narrow core with extended wings. These changes in line profile produce readily measurable changes in the equivalent width of each Balmer line.

Probabilities for K-shell ionization and capture by light ions: Scaling properties

Finite element investigation of the loading rate effect on the spinal load-sharing changes under impact conditions

We report the discovery of the progenitor of the recent type IIn SN 2008S in the nearby galaxy NGC 6946. Surprisingly, it was not found in deep, pre-explosion optical images of its host galaxy taken with the Large Binocular Telescope, but only through examination of archival Spitzer mid-IR data. A source coincident with the SN 2008S position is clearly detected in the 4.5, 5.8, and 8.0 micron IRAC bands, showing no evident variability in the three years prior to the explosion, yet is undetected at 3.6 and 24 micron. The distinct presence of ~440 K dust, along with stringent LBT limits on the optical fluxes, suggests that the progenitor of SN 2008S was engulfed in a shroud of its own dust. The inferred luminosity of 3.5x10^4 Lsun implies a modest mass of ~10 Msun. We conclude that objects like SN 2008S are not exclusively associated with the deaths or outbursts of very massive eta Carinae-like objects. This conclusion holds based solely on the optical flux limits even if our identification of the progenitor with the mid-IR source is incorrect.

SN 2008S erupted in early 2008 in the grand design spiral galaxy NGC 6946. The progenitor was detected by Prieto et al. in Spitzer Space Telescope images taken over the four years prior to the explosion, but was not detected in deep optical images, from which they inferred a self-obscured object with a mass of about 10 Msun. We obtained Spitzer observations of SN 2008S five days after its discovery, as well as coordinated Gemini and Spitzer optical and infrared observations six months after its outburst. We have constructed radiative transfer dust models for the object before and after the outburst, using the same r^-2 density distribution of pre-existing amorphous carbon grains for all epochs and taking light-travel time effects into account for the early post-outburst epoch. We rule out silicate grains as a significant component of the dust around SN 2008S. The inner radius of the dust shell moved outwards from its pre-outburst value of 85 AU to a post-outburst value of 1250 AU, attributable to grain vaporisation by the light flash from SN 2008S. Although this caused the circumstellar extinction to decrease from Av = 15 before the outburst to 0.8 after the outburst, we estimate that less than 2% of the overall circumstellar dust mass was destroyed. The total mass-loss rate from the progenitor star is estimated to have been (0.5-1.0)x10^-4 Msun yr^-1. The derived dust mass-loss rate of 5x10^-7 Msun yr^-1 implies a total dust injection into the ISM of up to 0.01 Msun over the suggested duration of the self-obscured phase. We consider the potential contribution of objects like SN 2008S to the dust enrichment of galaxies.

We present the analysis of emission lines in high-resolution optical spectra of the planet-host star Proxima Centauri (Proxima) classified as a M5.5V\@. We carry out the detailed analysis of observed spectra to get a better understanding of the physical conditions of the atmosphere of this star. We identify the emission lines in a serie series of 147 high-resolution optical spectra of the star at different levels of activity and compare them with the synthetic spectra computed over a wide spectral range. Our synthetic spectra computed with the PHOENIX 2900/5.0/0.0 model atmosphere fits pretty well the observed optical-to-near-infrared spectral energy distribution. However, modelling strong atomic lines in the blue spectrum (3900--4200\AA{}) requires implementing additional opacity. We show that high temperature layers in Proxima Centauri consist in at least three emitting parts: a) a stellar chromosphere where numerous emission lines form. We suggest that some emission cores of strong absorption lines of metals form there; b) flare regions above the chromosphere, where hydrogen Balmer lines up to high transition levels (10--2) form; c) a stellar wind component with V${r}$\,=\,$-$30 \kmps{} seen in some Balmer lines as blue shifted emission lines. We believe that the observed He line at 4026\AA{} in emission can be formed in that very hot region. We show, that real structure of the atmosphere of Proxima is rather complicated. The photosphere of the star is best fit by a normal M5 dwarf spectrum. On the other hand emission lines form in the chromosphere, flare regions and extended hot envelope.

In the present work, we have conducted a study to investigate the validity of three different charge-state models of ion beams penetrating plasma targets through a comparison with a total of five experiments from the literature. We have applied two alternative theoretical approaches. On the one hand, we have used a further extension of our cross-sectional model (CSM) code based on projectile electron loss and capture cross sections (rate equations) that was developed previously [Morales et al., Phys. Plasmas 24, 042703 (2017); R. Morales, Ph.D. thesis (Universidad de Castilla-La Mancha, 2019)]. On the other hand, we also used two charge-state models based on a semi-empirical formalism adapted to the plasma case: the Kreussler model [Kreussler et al., Phys. Rev. B 23, 82 (1981)] and the Gus'kov model [Guskov et al., Plasma Phys. Rep. 35, 709 (2009)]. Specifically, we present the predictions and the interpretation of the charge state of light to heavier ions at high, intermediate, and low velocities in Z-pinch and laser-produced partially and fully ionized plasmas. We are showing that experimental data support our new CSM code based on the cross-sectional formalism. In contrast, the framework based on semi-empirical formulas is less accurate for a precise charge-state prediction, but it can be applied for a reasonable stopping power calculation. Overall, results denote that the Gus'kov model is better suited to stopping power calculations at low projectile velocities and the Kreussler model fits better the energy loss data at intermediate velocities. Additionally, we propose a simple non-equilibrium charge model, derived from the semi-empirical framework, as a function of the ion path and equilibrium charge state.

There are about a dozen symbiotic stars known to produce high-velocity jets during outbursts. MWC 560 (V694 Mon) is a symbiotic star that seems to show a permanent jet. After showing an unexpected brightening in 2018 November, it has continued to brighten until 2021 and is currently in the brightest state ever. We have been conducting long-term high-dispersion spectroscopic monitoring of this object since 2016 March. An emission wing with vFWHM ≈ 700 km s−1 in the hydrogen Balmer line at an unexpected brightening event in 2018 was reported by Ando et al. (2021, PASJ, 73, L1). In subsequent continuous observations, this emission wing was no longer seen on 2019 February 6. The absorption lines seen in the hydrogen Balmer lines are gradually deepening and spreading to the slower side of the velocity, and the outflow velocity is becoming slower. The expanding component generated by the outburst was initially observed in the emission wing just after the 2018 outburst, got gradually cooler, and was observed in the absorption line after 2019.

We have observed SN 1998S which exploded in NGC 3877, with the Utrecht Echelle Spectrograph (6-7 km s-1 FWHM) at the William Herschel Telescope and with the E230M echelle of the Space Telescope Imaging Spectrograph (8 km s-1 FWHM) aboard the Hubble Space Telescope. Both data sets were obtained at two epochs, separated by 19 (optical) and 7 days (UV data). From our own Galaxy we detect interstellar absorption lines of Ca II K, Fe II λλ2600, 2586, 2374, 2344, Mg I λ2852, and probably Mn II λ2576, at vLSR = -95 km s-1 arising from the outer edge of the High Velocity Cloud Complex M. We derive gas-phase abundances of [Fe/H] = -1.4 and [Mn/H] = -1.0, values which are very similar to warm disk clouds found in the local ISM. This is the first detection of manganese from a Galactic HVC, and we believe that the derived gas-phase abundances argue against the HVC material having an extragalactic origin. At the velocity of NGC 3877 we detect interstellar Mg I λ2852, Mn II λλ2576, 2594, 2606, Ca II K and Na I D2, D1 absorption lines, spanning a velocity range of -102 to +9 km s-1 from the systemic velocity of the galaxy (910 km s-1). Surprisingly, the component at -102 km s-1 is seen to increase by a factor of 1 dex in N(Na I) between 1998 March 20 and April 8, and in N(Mg I) between 1998 April 4 and April 11. Unusually, our data also show narrow Balmer, He I, and metastable UV Fe II P Cygni profiles, with a narrow absorption component superimposed on the bottom of the profile's absorption trough. Both the broad and narrow components of the optical lines are seen to increase substantially in strength between March 20 and April 8. The broad absorption covers ~350 km s-1 and is seen in Mg II λλ2796, 2803 absorption as well, although there is no evidence of narrow Mg II emission forming a P Cygni profile. There is some suggestion that this shelf has decreased in strength over 7 days between April 4 and April 11. Most of the low-ionization absorption can be understood in terms of gas corotating with the disk of NGC 3877, provided the supernova is at the back of the disk as we observe it, and the H I disk is of a similar thickness to our own Galaxy. However, the variable component seen in all the other lines, and the accompanying emission which forms the classic P Cygni profiles, most likely arise in slow-moving circumstellar outflows originating from the red supergiant progenitor of SN 1998S.

We have obtained high-resolution Far Ultraviolet Spectroscopic Explorer (FUSE) and Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) echelle observations of the quasar PG 1116 + 215 (zem = 0.1765, l = 22336, b = +6821). The semicontinuous coverage of the ultraviolet spectrum over the wavelength range 916-2800 Å provides detections of Galactic and high-velocity cloud (HVC) absorption over a wide range of ionization species: H I, C II-IV, N I-II, O I, O VI, Mg II, Si II-IV, P II, S II, and Fe II over the velocity range -100 km s-1 < vLSR < +200 km s-1. The high dispersion of these spectra (6.5-20 km s-1) reveals that low-ionization species consist of five discrete components: three at low and intermediate velocities (vLSR ≈ -44, -7, +56 km s-1) and two at high velocities (vLSR ≈ +100, +184 km s-1). Over the same velocity range, the higher ionization species (C III-IV, O VI, Si IV)—those with ionization potentials larger than 40 eV—show continuous absorption with column density peaks at vLSR ≈ 10 km s-1, the expected velocity of halo gas corotating with the Galactic disk, and vLSR ≈ +184 km s-1, the velocity of the higher velocity HVC. The velocity coincidence of both low- and high-ionization species in the vLSR ≈ +184 km s-1 HVC gas suggests that they arise in a common structure, though not necessarily in the same gaseous phase. The absorption structure in the high-ionization gas, which extends to very low velocities, suggests a scenario in which a moderately dense cloud of gas is streaming away from the Galaxy through a hot external medium (either the Galactic halo or corona) that is stripping gas from this cloud. The cloud core produces the observed neutral atoms and low-ionization species. The stripped material is the likely source of the high-ionization species. Among the host of collisionally ionized nonequilibrium models, we find that shock ionization and conductive interfaces can account for the column density ratios of high-ionization species. The nominal metallicity of the neutral gas using the O I and H I column densities is [O/H] ∼ -0.66, with a substantial uncertainty caused by the saturation of the H I Lyman series in the FUSE band. The ionization of the cloud core is likely dominated by photons, and assuming the source of ionizing photons is the extragalactic UV background, we estimate the cloud has a density of 10-2.7 cm-3 with a thermal pressure p/k ≈ 24 cm-3 K. If photons escaping the Galactic disk are also included (i.e., if the cloud lies closer than the outer halo), the density and thermal pressure could be higher by as much as 2 dex. In either case, the relative abundances of O, Si, and Fe in the cloud core are readily explained without departures from the solar pattern. We compare the column density ratios of the HVCs toward the PG 1116+215 to other isolated HVCs as well as Complex C. Magellanic Stream gas (either a diffuse extension of the leading arm or gas stripped from a prior passage) is a possible origin for this gas and is consistent with the location of the high-velocity gas on the sky, as well as its high positive velocity, the ionization, and metallicity.

In 149 units from area 17 and 48 units from area 18 the responses to stationary stimulation of different durations were compared with the responses to the same stimulus (a 0.3 degrees-wide light or dark bar) moving at different velocities. The aim was to test the hypothesis that the range of effective velocities depends on the time needed for the bar to cross the receptive field. Forty-two percent of the area 17 cells and 8% of the area 18 cells responded poorly or not at all to briefly presented stationary stimulation. These cells were unable to respond at high velocities, and for these "duration-sensitive" cells the velocity characteristics are well predicted on the basis of responses to stationary stimulation of different durations. Cells that responded equally well to periods of stationary stimulation ranging from 12.5 to 3,200 ms ("duration-insensitive cells") were found to be able to respond at all equivalent velocities, but their preference for either high, low, or intermediate velocities was not reflected in differences in responsiveness to the different durations tested. Duration-sensitive cells in area 17 tended to have a receptive field near the area centralis, and 73% of them were classified as S-family cells, one third being end-stopped S-cells. In contrast only 18% of the duration-insensitive cells were of the S family, and these S-family cells were rarely end-stopped (1/12) or rarely had receptive fields within 5 degrees of the fovea (3/12). Duration-sensitive cells had very long latencies (median 285 ms) in response to a stationary flashed light bar of 1 s duration but much shorter latencies (median 91 ms) when tested with a slowly moving light bar. This difference was not seen in duration-insensitive cells (median latencies = 61 and 59 ms). The ability to respond at high velocity was contrast dependent. At a low contrast level all cells failed to respond to brief stimulation, whether moving or stationary. At high contrast levels only the duration-insensitive cells showed an increased responsivity to brief stimuli. The absence of responses in duration-sensitive cells to brief stimuli of high contrast may depend upon suppressive influences reaching these cells before the excitatory influences. We conclude that the velocity upper cutoff of most S-family cells with a central receptive field can be predicted from a knowledge of the minimum duration of stationary presentation required for their activation (median ON duration threshold, 200 ms).(ABSTRACT TRUNCATED AT 400 WORDS)