451 research outputs found
Circular Polarization in two Active Repeating Fast Radio Bursts
Fast radio bursts (FRBs) are bright millisecond radio bursts at cosmological
distances. Only a small fraction of FRBs apparently repeat. Polarization, a
fundamental property of electromagnetic signals, often carries critical
information about the radiation processes, the environment, and the intervening
medium of FRBs. Here we report circular polarization detections of two active
repeating FRBs, namely FRBs 20121102A and 20190520B, with the
Five-hundred-meter Aperture Spherical radio Telescope. We detect circular
polarization in both active repeating FRBs, which increases the number of
repeating FRBs with circular polarization to three. In one of the bursts of FRB
20121102A, we detect 64% degree of circular polarization. The observed circular
polarization is unlikely induced by multipath propagation. Our observations
favor circular polarization induced by Faraday conversion or radiation
mechanism intrinsic to the FRB source. The conditions to generate circular
polarization have to be rare in either case.Comment: 9pages, 3 figures, and 1 table, published in Science Bulleti
FRBs' Brownian Motion on Time-Energy Bivariate Space
The origin of fast radio bursts (FRBs), the brightest cosmic explosion in
radio bands, remains unknown. Magnetar-related mechanisms are currently
favored. The searches for short-term periodicity that is naturally expected for
such fast-spinning compact objects, however, have failed. We introduce here a
novel method for a comprehensive analysis of active FRBs' behaviors in the
time-energy domain. Using ``Pincus Index'' and ``Maximum Lyapunov Exponent'',
we were able to quantify the stochasticity and chaos, respectively, of the
bursting events and put FRBs in the context of common transient physical
phenomena, such as pulsars, earthquakes, and solar flares. In the bivariate
time-energy domain, repeated FRB bursts' behaviors deviate significantly (more
random, less chaotic) from pulsars, earthquakes, and solar flares. FRB bursts
wander in time-energy space stochastically, akin to Brownian motions. The high
degree of stochasticity suggests complex and even multi-origins for FRBs.Comment: 6 pages, 4 figures, submitte
Targeted Inactivation of Kinesin-1 in Pancreatic β-Cells In Vivo Leads to Insulin Secretory Deficiency
Suppression of Kinesin-1 by antisense oligonucleotides, or overexpression of dominant-negative acting kinesin heavy chain, has been reported to affect the sustained phase of glucose-stimulated insulin secretion in β-cells in vitro. In this study, we examined the in vivo physiological role of Kinesin-1 in β-cell development and function
The Large Dispersion and Scattering of FRB 20190520B Are Dominated by the Host Galaxy
The repeating fast radio burst FRB 20190520B is localized to a galaxy at z = 0.241, much closer than expected given its dispersion measure DM = 1205 ± 4 pc cm-3. Here we assess implications of the large DM and scattering observed from FRB 20190520B for the host galaxy's plasma properties. A sample of 75 bursts detected with the Five-hundred-meter Aperture Spherical radio Telescope shows scattering on two scales: a mean temporal delay τ(1.41 GHz) = 10.9 ± 1.5 ms, which is attributed to the host galaxy, and a mean scintillation bandwidth δν d(1.41 GHz) = 0.21 ± 0.01 MHz, which is attributed to the Milky Way. Balmer line measurements for the host imply an Hα emission measure (galaxy frame) EMs = 620 pc cm-6 × (T/104 K)0.9, implying DMHα of order the value inferred from the FRB DM budget, DMh=1121-138+89 pc cm-3 for plasma temperatures greater than the typical value 104 K. Combining τ and DMh yields a nominal constraint on the scattering amplification from the host galaxy FG=1.5-0.3+0.8(pc2km)-1/3, where F describes turbulent density fluctuations and G represents the geometric leverage to scattering that depends on the location of the scattering material. For a two-screen scattering geometry where τ arises from the host galaxy and Δν d from the Milky Way, the implied distance between the FRB source and dominant scattering material is ≤100 pc. The host galaxy scattering and DM contributions support a novel technique for estimating FRB redshifts using the τ-DM relation, and are consistent with previous findings that scattering of localized FRBs is largely dominated by plasma within host galaxies and the Milky Way
Investigation of vancomycin- resistant Enterococci (VRE) colonization in a intensive care of medical center in southern Taiwan
Effects of Acupuncture at Neiguan (PC 6) on Electroencephalogram
Abstract The aim of this study was to investigate if there were any effects on the electroencephalogram (EEG) of human brain by the manual stimulation of Neiguan (PC 6) acupuncture site. In this paper, two groups of six healthy male volunteers of ages 27.6 ± 14.2 (mean ± SD) and 28.5 ± 13.0 (mean ± SD) and no neurological disease participated in this study. A digital storage of 12-channel EEG recorder was used and spectral analyses of the data set of 18 trials were obtained before, during, and after sham/ manual acupuncture. To minimize artefacts, all data were collected with the subjects alert but eyes closed. No significant changes (P > 0.05) were obtained for the sham acupuncture group. As for the manual acupuncture group, the needle was inserted perpendicularly into the PC 6 acupuncture site and manually stimulated about 15 to 30 seconds to achieve De Qi sensation. Needles were left in place for 30 min and then removed. Analysis of the EEG data due to acupuncture was compared to the baseline data and changes were obtained. First, all trials had an increase in the amplitude and power of the alpha band during manual acupuncture (P < 0.05) when compared with the baseline data. Secondly, in the mean time, the frequency peaks in alpha band of 12-channels were all synchronized with much smaller standard deviation (P < 0.01). Thirdly, the manual acupuncture effects of higher power and synchronized frequencies persisted for at least 10 minutes after the experiment (P < 0.05) and did not disappear immediately for all 18 experiments. Finally, we hypothesized that the higher power and synchronized rhythms in brain oscillations may have to do with autonomic nervous system
FAST observations of an extremely active episode of FRB 20201124A: II. Energy Distribution
We report the properties of more than 800 bursts detected from the repeating
fast radio burst (FRB) source FRB 20201124A with the Five-hundred-meter
Aperture Spherical radio Telescope (FAST) during an extremely active episode on
UTC September 25-28, 2021 in a series of four papers. In this second paper of
the series, we mainly focus on the energy distribution of the detected bursts.
The event rate initially increased exponentially but the source activity
stopped within 24 hours after the 4th day. The detection of 542 bursts in one
hour during the fourth day marked the highest event rate detected from one
single FRB source so far. The bursts have complex structures in the
time-frequency space. We find a double-peak distribution of the waiting time,
which can be modeled with two log-normal functions peaking at 51.22 ms and
10.05 s, respectively. Compared with the emission from a previous active
episode of the source detected with FAST, the second distribution peak time is
smaller, suggesting that this peak is defined by the activity level of the
source. We calculate the isotropic energy of the bursts using both a partial
bandwidth and a full bandwidth and find that the energy distribution is not
significantly changed. We find that an exponentially connected broken-power-law
function can fit the cumulative burst energy distribution well, with the lower
and higher-energy indices being and ,
respectively. Assuming a radio radiative efficiency of , the
total isotropic energy of the bursts released during the four days when the
source was active is already erg, exceeding of
the available magnetar dipolar magnetic energy. This challenges the magnetar
models invoking an inefficient radio emission (e.g. synchrotron maser models).Comment: 26 pages, 7 figures, accepted for publication in Research in
Astronomy and Astrophysic
Risk groups defined by Recursive Partitioning Analysis of patients with colorectal adenocarcinoma treated with colorectal resection
<p>Abstract</p> <p>Background</p> <p>To define different prognostic groups of surgical colorectal adenocarcinoma patients derived from recursive partitioning analysis (RPA).</p> <p>Methods</p> <p>Ten thousand four hundred ninety four patients with colorectal adenocarcinoma underwent colorectal resection from Taiwan Cancer Database during 2003 to 2005 were included in this study. Exclusion criteria included those patients with stage IV disease or without number information of lymph nodes. For the definition of risk groups, the method of classification and regression tree was performed. Main primary outcome was 5-year cancer-specific survival.</p> <p>Results</p> <p>We identified six prognostic factors for cancer-specific survival, resulting in seven terminal nodes. Four risk groups were defined as following: Group 1 (mild risk, 1,698 patients), Group 2 (moderate risk, 3,129 patients), Group 3 (high risk, 4,605 patients) and Group 4 (very high risk, 1,062 patients). The 5-year cancer-specific survival for Group 1, 2, 3, and 4 was 86.6%, 62.7%, 55.9%, and 36.6%, respectively (p < 0.001). Hazard ratio of death was 2.13, 5.52 and 10.56 (95% confidence interval 1.74-2.60, 4.58-6.66 and 8.66-12.9, respectively) times for Group 2, 3, and 4 as compared to Group 1. The predictive capability of these grouping was also similar in terms of overall and progression-free survival.</p> <p>Conclusion</p> <p>The use of RPA offered an alternative grouping method that could predict the survival of patients who underwent surgery for colorectal adenocarcinoma.</p
Molecular Basis of NDM-1, a New Antibiotic Resistance Determinant
The New Delhi Metallo-β-lactamase (NDM-1) was first reported in 2009 in a Swedish patient. A recent study reported that Klebsiella pneumonia NDM-1 positive strain or Escherichia coli NDM-1 positive strain was highly resistant to all antibiotics tested except tigecycline and colistin. These can no longer be relied on to treat infections and therefore, NDM-1 now becomes potentially a major global health threat
FAST observations of an extremely active episode of FRB 20201124A: III. Polarimetry
As the third paper in the multiple-part series, we report the statistical
properties of radio bursts detected from the repeating fast radio burst (FRB)
source FRB 20201124A with the Five-hundred-meter Aperture Spherical radio
telescope (FAST) during an extremely active episode between the 25th and the
28th of September 2021 (UT). We focus on the polarisation properties of 536
bright bursts with . We found that the Faraday rotation
measures (RMs) monotonically dropped from to in the 4-day window. The RM values were compatible with
the values ( to ) reported 4 month ago (Xu et
al. 2022). However, the RM evolution rate in the current observation window was
at least an order of magnitude smaller than the one ($\sim 500\ {\rm rad \
m^{-2}\, day^{-1}}\le 1\ {\rm rad \ m^{-2} day^{-1}}L/IV/I\sigma$) were observed in 33% of
all bursts. The polarisation of single pulses seems to follow certain complex
trajectories on the Poincar\'e sphere, which may shed light on the radiation
mechanism at the source or the plasma properties along the path of FRB
propagation.Comment: 25 pages, 16 figures. Accepted by Research in Astronomy and
Astrophysics (RAA
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