10,434 research outputs found
A SiO J = 5 - 4 Survey Toward Massive Star Formation Regions
We performed a survey in the SiO line toward a sample of
199 Galactic massive star-forming regions at different evolutionary stages with
the SMT 10 m and CSO 10.4 m telescopes. The sample consists of 44 infrared dark
clouds (IRDCs), 86 protostellar candidates, and 69 young \HII\ regions. We
detected SiO line emission in 102 sources, with a detection
rate of 57\%, 37\%, and 65\% for IRDCs, protostellar candidates, and young
\HII\ regions, respectively. We find both broad line with Full Widths at Zero
Power (FWZP) 20 \kms and narrow line emissons of SiO in objects at various
evolutionary stages, likely associated with high-velocity shocks and
low-velocity shocks, respectively. The SiO luminosities do not show apparent
differences among various evolutionary stages in our sample. We find no
correlation between the SiO abundance and the luminosity-to-mass ratio,
indicating that the SiO abundance does not vary significantly in regions at
different evolutionary stages of star formation.Comment: 25 pages, 9 figures, 5 tables, accepted for publication in Ap
Generation of Oligodendrocyte Progenitor Cells From Mouse Bone Marrow Cells.
Oligodendrocyte progenitor cells (OPCs) are a subtype of glial cells responsible for myelin regeneration. Oligodendrocytes (OLGs) originate from OPCs and are the myelinating cells in the central nervous system (CNS). OLGs play an important role in the context of lesions in which myelin loss occurs. Even though many protocols for isolating OPCs have been published, their cellular yield remains a limit for clinical application. The protocol proposed here is novel and has practical value; in fact, OPCs can be generated from a source of autologous cells without gene manipulation. Our method represents a rapid, and high-efficiency differentiation protocol for generating mouse OLGs from bone marrow-derived cells using growth-factor defined media. With this protocol, it is possible to obtain mature OLGs in 7-8 weeks. Within 2-3 weeks from bone marrow (BM) isolation, after neurospheres formed, the cells differentiate into Nestin+ Sox2+ neural stem cells (NSCs), around 30 days. OPCs specific markers start to be expressed around day 38, followed by RIP+O4+ around day 42. CNPase+ mature OLGs are finally obtained around 7-8 weeks. Further, bone marrow-derived OPCs exhibited therapeutic effect in shiverer (Shi) mice, promoting myelin regeneration and reducing the tremor. Here, we propose a method by which OLGs can be generated starting from BM cells and have similar abilities to subventricular zone (SVZ)-derived cells. This protocol significantly decreases the timing and costs of the OLGs differentiation within 2 months of culture
Interacting heavy fermions in a disordered optical lattice
We have theoretically studied the effect of disorder on ultracold
alkaline-earth atoms governed by the Kondo lattice model in an optical lattice
via simplified double-well model and hybridization mean-field theory.
Disorder-induced narrowing and even complete closure of hybridization gap have
been predicted and the compressibility of the system has also been investigated
for metallic and Kondo insulator phases in the presence of the disordered
potential. To make connection to the experimental situation, we have
numerically solved the disordered Kondo lattice model with an external harmonic
trap and shown both the melting of Kondo insulator plateau and an
compressibility anomaly at low-density
Millimeter Spectral Line Mapping Observations Toward Four Massive Star Forming HII Regions
We present spectral line mapping observations toward four massive
star-forming regions (Cepheus A, DR21S, S76E and G34.26+0.15), with the IRAM 30
meter telescope at 2 mm and 3 mm bands. Totally 396 spectral lines from 51
molecules, one helium recombination line, ten hydrogen recombination lines, and
16 unidentified lines were detected in these four sources. An emission line of
nitrosyl cyanide (ONCN, 14-13) was detected in G34.26+0.15,
as first detection in massive star-forming regions. We found that the
-CH and NHD show enhancement in shocked regions as
suggested by evidences of SiO and/or SO emission. Column density and rotational
temperature of CHCN were estimated with the rotational diagram method for
all four sources. Isotope abundance ratios of C/C were derived
using HCN and its C isotopologue, which were around 40 in all four
massive star-forming regions and slightly lower than the local interstellar
value (65). N/N and O/O abundance ratios in
these sources were also derived using double isotopic method, which were
slightly lower than that in local interstellar medium. Except for Cep A,
S/S ratio in the other three targets were derived, which were
similar to that in the local interstellar medium. The column density ratios of
N(DCN)/N(HCN) and N(DCO)/N(HCO) in these sources were more than two
orders of magnitude higher than the elemental [D]/[H] ratio, which is
1.510. Our results show the later stage sources, G34.26+0.15 in
particular, present more molecular species than earlier stage ones. Evidence of
shock activity is seen in all stages studied.Comment: 32 pages, 11 figures, 8 tables, accepted for publication in MNRA
SMA observations of C2H in High-Mass Star Forming Regions
CH is a representative hydrocarbon that is abundant and ubiquitous in the
interstellar medium (ISM). To study its chemical properties, we present
Submillimeter Array (SMA) observations of the CH and HCN
transitions and the 1.1 mm continuum emission toward four OB
cluster-forming regions, AFGL 490, ON 1, W33 Main, and G10.6-0.4, which cover a
bolometric luminosity range of 10--10 . We found that
on large scales, the CH emission traces the dense molecular envelope.
However, for all observed sources, the peaks of CH emission are offset by
several times times 10 AU from the peaks of 1.1 mm continuum emission,
where the most luminous stars are located. By comparing the distribution and
profiles of CH hyperfine lines and the 1.1 mm continuum emission, we find
that the CH column density (and abundance) around the 1.1 mm continuum
peaks is lower than those in the ambient gas envelope. Chemical models suggest
that CH might be transformed to other species owing to increased
temperature and density; thus, its reduced abundance could be the signpost of
the heated molecular gas in the 10 AU vicinity around the embedded
high-mass stars. Our results support such theoretical prediction for centrally
embedded -- OB star-forming cores, while future
higher-resolution observations are required to examine the CH
transformation around the localized sites of high-mass star formation.Comment: 10 pages, 6 figures. ApJ accepted. Comments welcom
Molecular Evolution of the Deuterolysin (M35) Family Genes in Coccidioides
Coccidioides is a primary fungal pathogen of humans, causing life-threatening respiratory disease known as coccidioidomycosis (Valley fever) in immunocompromised individuals. Recently, Sharpton et al (2009) found that the deuterolysin (M35) family genes were significantly expanded in both the Coccidioides genus and in U. reesii, and that Coccidioides has acquired three more M35 family genes than U. reesii. In the present work, phylogenetic analyses based on a total of 28 M35 family genes using different alignments and tree-building methods consistently revealed five clades with high nodal supports. Interestingly, likelihood ratio tests suggested significant differences in selective pressure on the ancestral lineage of three additional duplicated M35 family genes from Coccidioides species compared to the other lineages in the phylogeny, which may be associated with novel functional adaptations of M35 family genes in the Coccidioides species, e.g., recent pathogenesis acquisition. Our study adds to the expanding view of M35 family gene evolution and functions as well as establishes a theoretical foundation for future experimental investigations
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