351 research outputs found
Molecular environments of 51 Planck cold clumps in Orion complex
A mapping survey towards 51 Planck cold clumps projected on Orion complex was
performed with J=1-0 lines of CO and CO at the 13.7 m telescope
of Purple Mountain Observatory. The mean column densities of the Planck gas
clumps range from 0.5 to 9.5 cm, with an average value of
(2.91.9) cm. While the mean excitation temperatures
of these clumps range from 7.4 to 21.1 K, with an average value of 12.13.0
K. The averaged three-dimensional velocity dispersion in these
molecular clumps is 0.660.24 km s. Most of the clumps have
larger than or comparable with . The H
column density of the molecular clumps calculated from molecular lines
correlates with the aperture flux at 857 GHz of the dust emission. Through
analyzing the distributions of the physical parameters, we suggest turbulent
flows can shape the clump structure and dominate their density distribution in
large scale, but not affect in small scale due to the local fluctuations.
Eighty two dense cores are identified in the molecular clumps. The dense cores
have an averaged radius and LTE mass of 0.340.14 pc and 38
M_{\sun}, respectively. And structures of low column density cores are more
affected by turbulence, while those of high column density cores are more
concerned by other factors, especially by gravity. The correlation of the
velocity dispersion versus core size is very weak for the dense cores. The
dense cores are found most likely gravitationally bounded rather than pressure
confined. The relationship between and can be well fitted
with a power law. The core mass function here is much more flatten than the
stellar initial mass function. The lognormal behavior of the core mass
distribution is most likely determined by the internal turbulence.Comment: Accepted to The Astrophysical Journal Supplement Series (ApJS
Uniform Infall toward the Cometary H II Region in the G34.26+0.15 Complex?
Gas accretion is a key process in star formation. However, the gas infall
detections in high-mass star forming regions with high-spatial resolution
observations are rare. Here we report the detection of gas infall towards a
cometary ultracompact H{\sc ii} region "C" in G34.26+0.15 complex. The hot core
associated with "C" has a mass of 76 M_{\sun} and a volume density of
1.1 cm. The HCN (3--2), HCO (1--0) lines observed by
single-dishes and the CN (2--1) lines observed by the SMA show redshifted
absorption features, indicating gas infall. We found a linear relationship
between the line width and optical depth of the CN (2--1) lines. Those
transitions with larger optical depth and line width have larger absorption
area. However, the infall velocities measured from different lines seem to be
constant, indicating the gas infall is uniform. We also investigated the
evolution of gas infall in high-mass star forming regions. At stages prior to
hot core phase, the typical infall velocity and mass infall rate are 1
km s and M_{\sun}\cdotyr, respectively. While in
more evolved regions, the infall velocity and mass infall rates can reach as
high as serval km s and M_{\sun}\cdotyr,
respectively. Accelerated infall has been detected towards some hypercompact
H{\sc ii} and ultracompact H{\sc ii} regions. However, the acceleration
phenomenon becomes inapparent in more evolved ultracompact H{\sc ii} regions
(e.g. G34.26+0.15)
Molecular gas and triggered star formation surrounding Wolf-Rayet stars
The environments surrounding nine Wolf-Rayet stars were studied in molecular
emission. Expanding shells were detected surrounding these WR stars (see left
panels of Figure 1). The average masses and radii of the molecular cores
surrounding these WR stars anti-correlate with the WR stellar wind velocities
(middle panels of Figure 1), indicating the WR stars has great impact on their
environments. The number density of Young Stellar Objects (YSOs) is enhanced in
the molecular shells at 5 arcmin from the central WR star (lower-right
panel of Figure 1). Through detailed studies of the molecular shells and YSOs,
we find strong evidences of triggered star formation in the fragmented
molecular shells (\cite[Liu et al. 2010]{liu_etal12}Comment: 1 page, IAUS29
Competitive accretion in the protocluster G10.6-0.4?
We present the results of high spatial resolution observations at 1.1 mm
waveband, with the Submillimetre Array (SMA), towards the protocluster
G10.6-0.4. The 1.1 mm continuum emission reveals seven dense cores, towards
which infall motions are all detected with the red-shifted absorption dips in
HCN (3--2) line. This is the first time that infall is seen towards multiple
sources in a protocluster. We also identified four infrared point sources in
this region, which are most likely Class 0/I protostars. Two jet-like
structures are also identified from Spitzer/IRAC image. The dense core located
in the centre has much larger mass than the off-centre cores. The clump is in
overall collapse and the infall motion is supersonic. The standard deviation of
core velocities and the velocity differences between the cores and the
cloud/clump are all larger than the thermal velocity dispersion. The picture of
G10.6-0.4 seems to favor the "competitive accretion" model but needs to be
tested by further observations.Comment: 9 pages, 9 figures, 2 tables, Submitted to MNRA
Circular External Difference Families: Construction and Non-Existence
The circular external difference family and its strong version, which
themselves are of independent combinatorial interest, were proposed as variants
of the difference family to construct new unconditionally secure non-malleable
threshold schemes. In this paper, we present new results regarding the
construction and non-existence of (strong) circular external difference
families, thereby solving several open problems on this topic
An Approach to the Production of Soluble Protein from a Fungal Gene Encoding an Aggregation-Prone Xylanase in Escherichia coli
The development of new procedures and protocols that allow researchers to obtain
recombinant proteins is of fundamental importance in the biotechnology field. A
strategy was explored to overcome inclusion-body formation observed when
expressing an aggregation-prone fungal xylanase in Escherichia
coli. pHsh is an expression plasmid that uses a synthetic
heat-shock (Hsh) promoter, in which gene expression is regulated by an
alternative sigma factor (σ32). A derivative of pHsh was
constructed by fusing a signal peptide to xynA2 gene to
facilitate export of the recombinant protein to the periplasm. The xylanase was
produced in a soluble form. Three factors were essential to achieving such
soluble expression of the xylanase: 1) the target gene was under the control of
the Hsh promoter, 2) the gene product was exported into the periplasm, and 3)
gene expression was induced by a temperature upshift. For the first time we
report the expression of periplasmic proteins under the control of an Hsh
promoter regulated by σ32. One unique feature of this approach
was that over 200 copies of the Hsh promoter in an E. coli cell
significantly increased the concentration of σ32. The growth
inhibition of the recombinant cells corresponded to an increase in the levels of
soluble periplasmic protein. Therefore, an alternative protocol was designed to
induce gene expression from pHsh-ex to obtain high levels of active soluble
enzymes
LLMDet: A Large Language Models Detection Tool
With the advancement of generative language models, the generated text has
come remarkably close to high-quality human-authored text in terms of fluency
and diversity. This calls for a highly practical detection tool that can
identify the source of text, preferably pinpointing the language model it
originates from. However, existing detection tools typically require access to
language models and can only differentiate between machine-generated and
human-authored text, failing to meet the requirements of rapid detection and
text tracing. Therefore, in this paper, we propose an efficient, secure, and
scalable detection tool called LLMDet, which calculates the proxy perplexity of
text by utilizing the prior information of the model's next-token
probabilities, obtained through pre-training. Subsequently, we use the
self-watermarking information of the model, as measured by proxy perplexity, to
detect the source of the text. We found that our method demonstrates impressive
detection performance while ensuring speed and security, particularly achieving
a recognition accuracy of 97.97\% for human-authored text. Furthermore, our
detection tool also shows promising results in identifying the large language
model (e.g., GPT-2, OPT, LLaMA, Vicuna...) responsible for the text. We release
the code and processed data at \url{https://github.com/TrustedLLM/LLMDet}.Comment: 7 pages, 1 figur
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