1,510 research outputs found
N-Morpholino-Δ8-dihydroabietamide
The title compound, C24H39NO2 (systematic name: 4-{[1,4a-dimethyl-7-(propan-2-yl)-1,2,3,4,4a,5,6,7,8,9,10,10a-dodecahydrophenanthren-1-yl]carbonyl}morpholine), has been synthesized from Δ8-dihydroabietic acid. Two cyclohexene rings adopt half-chair conformations, whereas the cyclohexane and morpholine rings are each in the chair conformation. Two methyl groups are in an axial position with respect to the tricyclic hydrophenanthrene nuclei
Spatiotemporal Sparse Bayesian Learning with Applications to Compressed Sensing of Multichannel Physiological Signals
Energy consumption is an important issue in continuous wireless
telemonitoring of physiological signals. Compressed sensing (CS) is a promising
framework to address it, due to its energy-efficient data compression
procedure. However, most CS algorithms have difficulty in data recovery due to
non-sparsity characteristic of many physiological signals. Block sparse
Bayesian learning (BSBL) is an effective approach to recover such signals with
satisfactory recovery quality. However, it is time-consuming in recovering
multichannel signals, since its computational load almost linearly increases
with the number of channels.
This work proposes a spatiotemporal sparse Bayesian learning algorithm to
recover multichannel signals simultaneously. It not only exploits temporal
correlation within each channel signal, but also exploits inter-channel
correlation among different channel signals. Furthermore, its computational
load is not significantly affected by the number of channels. The proposed
algorithm was applied to brain computer interface (BCI) and EEG-based driver's
drowsiness estimation. Results showed that the algorithm had both better
recovery performance and much higher speed than BSBL. Particularly, the
proposed algorithm ensured that the BCI classification and the drowsiness
estimation had little degradation even when data were compressed by 80%, making
it very suitable for continuous wireless telemonitoring of multichannel
signals.Comment: Codes are available at:
https://sites.google.com/site/researchbyzhang/stsb
The magnetic field in the NGC 2024 FIR 5 dense core
We used the Submillimeter Array (SMA) to observe the thermal polarized dust
emission from the protostellar source NGC 2024 FIR 5. The polarized emission
outlines a partial hourglass morphology for the plane-of-sky component of the
core magnetic field. Our data are consistent with previous BIMA maps, and the
overall magnetic field geometries obtained with both instruments are similar.
We resolve the main core into two components, FIR 5A and FIR 5B. A possible
explanation for the asymmetrical field lies in depolarization effects due to
the lack of internal heating from FIR 5B source, which may be in a prestellar
evolutionary state. The field strength was estimated to be 2.2 mG, in agreement
with previous BIMA data. We discuss the influence of a nearby H{\sc ii} region
over the field lines at scales of pc. Although the hot component is
probably compressing the molecular gas where the dust core is embedded, it is
unlikely that the radiation pressure exceeds the magnetic tension. Finally, a
complex outflow morphology is observed in CO (3 2) maps. Unlike
previous maps, several features associated with dust condensations other than
FIR 5 are detected.Comment: 48 pages, 12 figures, accepted for publication in The Astrophysical
Journa
Detection of 40-48 GHz dust continuum linear polarization towards the Class 0 young stellar object IRAS 16293-2422
We performed the new JVLA full polarization observations at 40-48 GHz
(6.3-7.5 mm) towards the nearby ( 1473.4 pc) Class 0 YSO IRAS
16293-2422, and compare with the previous SMA observations reported by Rao et
al. (2009; 2014). We observed the quasar J1407+2827 which is weakly polarized
and can be used as a leakage term calibrator for 9 GHz observations, to
gauge the potential residual polarization leakage after calibration. We did not
detect Stokes Q, U, and V intensities from the observations of J1407+2827, and
constrain (3-) the residual polarization leakage after calibration to
be 0.3\%. We detect linear polarization from one of the two binary
components of our target source, IRAS\,16293-2422\,B. The derived polarization
position angles from our observations are in excellent agreement with those
detected from the previous observations of the SMA, implying that on the
spatial scale we are probing (50-1000 au), the physical mechanisms for
polarizing the continuum emission do not vary significantly over the wavelength
range of 0.88-7.5 mm. We hypothesize that the observed polarization
position angles trace the magnetic field which converges from large scale to an
approximately face-on rotating accretion flow. In this scenario, magnetic field
is predominantly poloidal on 100 au scales, and becomes toroidal on smaller
scales. However, this interpretation remains uncertain due to the high dust
optical depths at the central region of IRAS\,16293-2422\,B and the uncertain
temperature profile. We suggest that dust polarization at wavelengths
comparable or longer than 7\,mm may still trace interstellar magnetic field.
Future sensitive observations of dust polarization in the fully optically thin
regime will have paramount importance for unambiguously resolving the magnetic
field configuration.Comment: 14 pages, 7 figures, accepted to A&A. Comments are welcom
N-Benzylidenenordehydroabietylamine
The title compound [systematic name: (1R,4aS,10aR,E)-N-benzylidene-7-isopropyl-1,4a-dimethyl-1,2,3,4,4a,9,10,10a-octahydrophenanthren-1-amine], C26H33N, has been synthesized from nor-dehydroabietylamine and benzaldehyde. The two cyclohexane rings form a trans ring junction with classic chair and half-chair conformations, respectively, the two methyl groups are on the same side of tricyclic hydrophenanthrene structure. The dihedral angle between two benzene rings is 44.2 (4)°. The C=N bond is in an E configuration
N-(2-Pyridylmethyleneamino)dehydroabietylamine
The title compound {systematic name: 1-[(1R,4aS,10aR)-7-isopropyl-1,2,3,4,4a,9,10,10a-octahydrophenanthren-1-yl]-N-[(E)-2-pyridylmethyleneamino]methanamine}, C26H33N2, has been synthesized from dehydroabietylamine. The two cyclohexane rings form a trans ring junction with classic chair and half-chair conformations, respectively, whereas the benzene and pyridine rings are almost planar, and the dihedral angle between them is 80.4°. The two methyl groups directly attached to the tricyclic nucleus are on the same side of the tricyclic hydrophenanthrene structure
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