86 research outputs found
Three Open Questions for the Design of AI for Music Composition
This paper suggests three open questions for designing AI for music composition by reflecting on interviews with expert and novice composers. Our questions consider the role of AI as a mediator, the importance of a composer’s originality, and AI for building intuition
Cryptolepis sanguinolenta Root Tablets: Effect of Binder Type and Concentration on the Tablet Properties
ABSTRACT The objectives of the study were to formulate Cryptolepis sanguinolenta root powder into tablets and to evaluate the effect of different binders and binder concentrations on the properties of tablets. The tablets were formulated by the wet granulation method using gelatin and sodium carboxymethyl cellulose (SCMC) as binders at concentrations of 2%, 4%, 6% and 8%w/w. The tablets were evaluated using the relevant official and unofficial tests. Also the phytochemistry of the powdered root extract of C. sanguinolenta was evaluated. Phytochemical analysis showed that C. sanguinolenta root contains alkaloids, terpenoids, steroids, proteins, carbohydrate, resins, reducing sugars and glycosides. Tablets formulated with SCMC significantly exhibited higher disintegration times than those formulated with gelatin (p<0.05).Tablets hardness ranged from 3.51 ± 0.12 to 5.02 ± 0.10 kgf for A1 and A4 tablets formulated with 2 and 8% gelatin and 2.00 ± 0.11 to 5.00 ± 0.17 kgf for B1 and B4 tablets formulated with 2 and 8% SCMC. All the tablet batches exhibited friability of < 1% (p<0.05). Therefore the powdered root of C. sanguinolenta could be formulated as normal release tablets using gelatin and SCMC in order to standardize the preparation and also enhance patient's compliance
Electrical modelling and design of ultra-fast micro-OLED with coplanar wave-guided electrodes in ON-OFF regime
A Detection of Cosmological 21 cm Emission from CHIME in Cross-correlation with eBOSS Measurements of the Lyman- Forest
We report the detection of 21 cm emission at an average redshift in the cross-correlation of data from the Canadian Hydrogen Intensity
Mapping Experiment (CHIME) with measurements of the Lyman- forest from
eBOSS. Data collected by CHIME over 88 days in the ~MHz frequency band
() are formed into maps of the sky and high-pass delay filtered
to suppress the foreground power, corresponding to removing cosmological scales
with at the average redshift.
Line-of-sight spectra to the eBOSS background quasar locations are extracted
from the CHIME maps and combined with the Lyman- forest flux
transmission spectra to estimate the 21 cm-Lyman- cross-correlation
function. Fitting a simulation-derived template function to this measurement
results in a detection significance. The coherent accumulation of the
signal through cross-correlation is sufficient to enable a detection despite
excess variance from foreground residuals times brighter than the
expected thermal noise level in the correlation function. These results are the
highest-redshift measurement of \tcm emission to date, and set the stage for
future 21 cm intensity mapping analyses at
CHIME/FRB Detection of Eight New Repeating Fast Radio Burst Sources
We report on the discovery of eight repeating fast radio burst (FRB) sources
found using the Canadian Hydrogen Intensity Mapping Experiment (CHIME)
telescope. These sources span a dispersion measure (DM) range of 103.5 to 1281
pc cm. They display varying degrees of activity: six sources were
detected twice, another three times, and one ten times. These eight repeating
FRBs likely represent the bright and/or high-rate end of a distribution of
infrequently repeating sources. For all sources, we determine sky coordinates
with uncertainties of 10. FRB 180916.J0158+65 has a
burst-averaged DM = pc cm and a low DM excess over the
modelled Galactic maximum (as low as 20 pc cm); this source also
has a Faraday rotation measure (RM) of rad m, much
lower than the RM measured for FRB 121102. FRB 181030.J1054+73 has the lowest
DM for a repeater, pc cm, with a DM excess of 70
pc cm. Both sources are interesting targets for multi-wavelength
follow-up due to their apparent proximity. The DM distribution of our repeater
sample is statistically indistinguishable from that of the first 12 CHIME/FRB
sources that have not repeated. We find, with 4 significance, that
repeater bursts are generally wider than those of CHIME/FRB bursts that have
not repeated, suggesting different emission mechanisms. Our repeater events
show complex morphologies that are reminiscent of the first two discovered
repeating FRBs. The repetitive behavior of these sources will enable
interferometric localizations and subsequent host galaxy identifications.Comment: 40 pages, 11 figures; accepted by ApJL on 28 September 2019; added
analysis of correlation between width and max. flux densit
Periodic activity from a fast radio burst source
Fast radio bursts (FRBs) are bright, millisecond-duration radio transients
originating from extragalactic distances. Their origin is unknown. Some FRB
sources emit repeat bursts, ruling out cataclysmic origins for those events.
Despite searches for periodicity in repeat burst arrival times on time scales
from milliseconds to many days, these bursts have hitherto been observed to
appear sporadically, and though clustered, without a regular pattern. Here we
report the detection of a day periodicity (or possibly a
higher-frequency alias of that periodicity) from a repeating FRB
180916.J0158+65 detected by the Canadian Hydrogen Intensity Mapping Experiment
Fast Radio Burst Project (CHIME/FRB). In 38 bursts recorded from September
16th, 2018 through February 4th, 2020, we find that all bursts arrive in a
5-day phase window, and 50% of the bursts arrive in a 0.6-day phase window. Our
results suggest a mechanism for periodic modulation either of the burst
emission itself, or through external amplification or absorption, and disfavour
models invoking purely sporadic processes
CHIME/FRB Discovery of 25 Repeating Fast Radio Burst Sources
We present the discovery of 25 new repeating fast radio burst (FRB) sources
found among CHIME/FRB events detected between 2019 September 30 and 2021 May 1.
The sources were found using a new clustering algorithm that looks for multiple
events co-located on the sky having similar dispersion measures (DMs). The new
repeaters have DMs ranging from 220 pc cm to 1700 pc
cm, and include sources having exhibited as few as two bursts to as many
as twelve. We report a statistically significant difference in both the DM and
extragalactic DM (eDM) distributions between repeating and apparently
nonrepeating sources, with repeaters having lower mean DM and eDM, and we
discuss the implications. We find no clear bimodality between the repetition
rates of repeaters and upper limits on repetition from apparently nonrepeating
sources after correcting for sensitivity and exposure effects, although some
active repeating sources stand out as anomalous. We measure the repeater
fraction and find that it tends to an equilibrium of % over
our exposure thus far. We also report on 14 more sources which are promising
repeating FRB candidates and which merit follow-up observations for
confirmation.Comment: Submitted to ApJ. Comments are welcome and follow-up observations are
encouraged
Sub-second periodicity in a fast radio burst
Fast radio bursts (FRBs) are millisecond-duration flashes of radio waves that
are visible at distances of billions of light-years. The nature of their
progenitors and their emission mechanism remain open astrophysical questions.
Here we report the detection of the multi-component FRB 20191221A and the
identification of a periodic separation of 216.8(1) ms between its components
with a significance of 6.5 sigmas. The long (~3 s) duration and nine or more
components forming the pulse profile make this source an outlier in the FRB
population. Such short periodicity provides strong evidence for a neutron-star
origin of the event. Moreover, our detection favours emission arising from the
neutron-star magnetosphere, as opposed to emission regions located further away
from the star, as predicted by some models.Comment: Updated to conform to the accepted versio
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