ABSTRACT
A transient in the Local Group dwarf irregular galaxy NGC 6822 (Barnard’s Galaxy) was discovered on 2017 August 2 and is only the second classical nova discovered in that galaxy. We ...conducted optical, near-ultraviolet, and X-ray follow-up observations of the eruption, the results of which we present here. This ‘very fast’ nova had a peak V-band magnitude in the range −7.41 > MV > −8.33 mag, with decline times of t2,V = 8.1 ± 0.2 d and t3,V = 15.2 ± 0.3 d. The early- and late-time spectra are consistent with an Fe ii spectral class. The H α emission line initially has a full width at half-maximum intensity of ∼2400 km s−1 – a moderately fast ejecta velocity for the class. The H α line then narrows monotonically to ∼1800 km s−1 by 70 d post-eruption. The lack of a pre-eruption coincident source in archival Hubble Space Telescope imaging implies that the donor is a main-sequence, or possibly subgiant, star. The relatively low-peak luminosity and rapid decline hint that AT 2017fvz may be a ‘faint and fast’ nova.
The ability to control electroencephalographic rhythms and to map those changes to the actuation of mechanical devices provides the basis for an assistive brain-computer interface (BCI). In this ...study, we investigate the ability of subjects to manipulate the sensorimotor mu rhythm (8-12-Hz oscillations recorded over the motor cortex) in the context of a rich visual representation of the feedback signal. Four subjects were trained for approximately 10 h over the course of five weeks to produce similar or differential mu activity over the two hemispheres in order to control left or right movement in a three-dimensional video game. Analysis of the data showed a steep learning curve for producing differential mu activity during the first six training sessions and leveling off during the final four sessions. In contrast, similar mu activity was easily obtained and maintained throughout all the training sessions. The results suggest that an intentional BCI based on a binary signal is possible. During a realistic, interactive, and motivationally engaging task, subjects learned to control levels of mu activity faster when it involves similar activity in both hemispheres. This suggests that while individual control of each hemisphere is possible, it requires more learning time.
In this work, BVRI light curves of 55 Type II supernovae (SNe II) from the Lick Observatory Supernova Search programme obtained with the Katzman Automatic Imaging Telescope and the 1 m Nickel ...telescope from 2006 to 2018 are presented. Additionally, more than 150 spectra gathered with the 3 m Shane telescope are published. We conduct an analyse of the peak absolute magnitudes, decline rates, and time durations of different phases of the light and colour curves. Typically, our light curves are sampled with a median cadence of 5.5 d for a total of 5093 photometric points. In average, V-band plateau declines with a rate of 1.29 mag (100 d)(exp −1), which is consistent with previously published samples. For each band, the plateau slope correlates with the plateau length and the absolute peak magnitude: SNe II with steeper decline have shorter plateau duration and are brighter. A time-evolution analysis of spectral lines in term of velocities and pseudo-equivalent widths is also presented in this paper. Our spectroscopic sample ranges between 1 and 200 d post-explosion and has a median ejecta expansion velocity at 50 d post-explosion of 6500 km s(exp −1) (H α line) and a standard dispersion of 2000 km s(exp −1). Nebular spectra are in good agreement with theoretical models using a progenitor star having a mass <16M⨀. All the data are available to the community and will help to understand SN II diversity better, and therefore to improve their utility as cosmological distance indicators.
A transient in the Local Group dwarf irregular galaxy NGC 6822 (Barnard's Galaxy) was discovered on 2017 August 2 and is only the second classical nova discovered in that galaxy. We conducted ...optical, near-ultraviolet, and X-ray follow-up observations of the eruption, the results of which we present here. This 'very fast' nova had a peak \(V\)-band magnitude in the range \(-7.41>M_V>-8.33\) mag, with decline times of \(t_{2,V} = 8.1 \pm 0.2\) d and \(t_{3,V} = 15.2 \pm 0.3\) d. The early- and late-time spectra are consistent with an Fe II spectral class. The H\(\alpha\) emission line initially has a full width at half-maximum intensity of \(\sim 2400\) km s\(^{-1}\) - a moderately fast ejecta velocity for the class. The H\(\alpha\) line then narrows monotonically to \(\sim1800\) km s\(^{-1}\) by 70 d post-eruption. The lack of a pre-eruption coincident source in archival Hubble Space Telescope imaging implies that the donor is a main sequence, or possibly subgiant, star. The relatively low peak luminosity and rapid decline hint that AT 2017fvz may be a 'faint and fast' nova.
Auditory ERPs were recorded from eight tinnitus patients and 12 controls. Tone pips of 1000 and 2000 Hz, as well as the patient's tinnitus pitch (around 4000 Hz) were used. Controls received tone ...pips at 1000, 2000, and 4000 Hz. Tones were presented at 30, 36, 42, 48 and 54 dB/SL. The intensity dependence of the auditory N100 was calculated for each frequency in each group. Patients showed a steeper response to the tinnitus frequency than responses to the 4000 Hz tone in controls. In contrast, intensity-dependence to the 2000 Hz tones was significantly decreased in patients (two-tailed Wilcoxon-Mann-Whitney U-test, p < 0.05). Responses to the 1000 Hz tones were similar for both groups. This reduced intensity dependence is hypothesized to result from lateral inhibition arising from tinnitus related activity in the 4000 Hz isofrequency region.
Cross-sectional echocardiography was used to quantify left ventricular mass noninvasively in 21 dogs. Short- and long-axis cross-sectional images of the left ventricle were reproducibly traced at ...endocardial and epicardial borders during stop-motion video-tape replay. We used area, length and diameter measurements to calculate left ventricular mass by seven mathematic models, including the standard formulas used with M-mode echocardiography and cineangiography. Calculated mass was compared with excised weight of the left ventricle by regression and percent error analyses. Formulas using short-axis areas and long-axis length resulted in higher correlation coefficients (0.94--0.95) and lower mean errors (6--7%) than for standard formulas. Since short-axis areas account for regional left ventricular irregularities, noninvasive quantification of left ventricular mass by cross-sectional echocardiography in dogs is most accurate with formulas using short-axis areas.
A reflection mode proof-of-concept medical ultrasound imager based on time delay spectrometry has been developed and tested. The system uses a broad band swept-frequency signal operating up to 10 ...MHz. Signal processing using a fast Fourier transform (FFT) permits extraction of range information. The imager has a higher signal-to-noise ratio than pulse-echo systems which allows high resolution at greater depths. The time delay spectrometry (TDS) spread spectrum operates at lower peak intensities than pulse-echo and permits more control of the spectral content and amplitude of the signal. At present, the system is non-real time which degrades in vivo imaging because of averaging over several cardiac cycles and tissue movement.
Three-dimensional sonograms of the common carotid artery were obtained using a device which takes images in parallel planes. Tests in phantoms simulating atherosclerotic vessels the same size as the ...common carotid artery indicated that the coefficient of variation of a single luminal measurement was 2-5%.
The velocity and attenuation of sound has been determined for freshly excised human and canine arterial tissues using a time delay spectrometer (TDS) technique. Frequency was swept from 0 to 10 MHz ...with data being taken in the range from 2 to 10 MHz. The velocity was determined using a comparison of the time delay for the received signal between a water path and a sample tissue of measured thickness. The velocity of sound was measured for various pathologies and related to biochemical assays of tissue. It was found to increase with increasing ultrasound attenuation of the tissue. The velocity was shown to increase with increased collagen, C, expressed as a percentage of wet weight of the tissue, V = 17.8* C + 1561 m/s at 37 degrees C, r = 0.77 but was strongly dependent on tissue cholesterol or low levels of calcium. For highly calcified lesions, the velocity of sound was found to be approximately 2000 m/s at 37 degrees C.
In this work, BV RI light curves of 55 Type II supernovae (SNe II) from the Lick Observatory Supernova Search program obtained with the Katzman Automatic Imaging Telescope and the 1 m Nickel ...telescope from 2006 to 2018 are presented. Additionally, more than 150 spectra gathered with the 3 m Shane telescope are published. We conduct an analyse of the peak absolute magnitudes, decline rates, and time durations of different phases of the light and colour curves. Typically, our light curves are sampled with a median cadence of 5.5 days for a total of 5093 photometric points. In average V-band plateau declines with a rate of 1.29 mag (100 days)-1, which is consistent with previously published samples. For each band, the plateau slope correlates with the plateau length and the absolute peak magnitude: SNe II with steeper decline have shorter plateau duration and are brighter. A time-evolution analysis of spectral lines in term of velocities and pseudoequivalent widths is also presented in this paper. Our spectroscopic sample ranges between 1 and 200 days post-explosion and has a median ejecta expansion velocity at 50 days post-explosion of 6500 km/s (Halpha line) and a standard dispersion of 2000 km/s. Nebular spectra are in good agreement with theoretical models using a progenitor star having a mass <16 Msol. All the data are available to the community and will help to understand SN II diversity better, and therefore to improve their utility as cosmological distance indicators.
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