326 research outputs found
Experimental research on evolving rules of segregation ice in artificial frozen soil
AbstractThe foundation of frost heave controlling is the research on evolving rules of segregation ice. The evolving rules of segregation ice have been researched systematically by one-dimension freezing experiments. The technique of dynamic photograph has been applied in research for the first time. The research on segregation ice indicated that three phases can be divided according to the change of temperature field: few segregation ices appeared in the first phases, several thin and discontinuous segregation ices appeared in the second phases, segregation ice evolvement was mainly the growth of final ice lens in the third phase when the freezing front tended to be stable
Regulation of transplanted mesenchymal stem cells by the lung progenitor niche in rats with chronic obstructive pulmonary disease
Investigating a Global Collapsing Hub-Filament Cloud G326.611+0.811
We present the dynamics study toward the G326.611+0.811 (G326)
hub-filament-system (HFS) cloud using the new APEX observations of both
CO and CO (J = 2-1). The G326 HFS cloud constitutes a central hub
and at least four hub-composing filaments that are divided into a major branch
of filaments (F1, and F2) and a side branch (F3-F5). The cloud holds ongoing
high-mass star formation as characterised by three massive dense clumps (i.e.,
370-1100 and 0.14-0.16 g cm for C1-C3) with the high
clump-averaged mass infalling rates ( yr) within
in the major filament branch, and the associated point sources bright at 70
m typical of young protostars. Along the five filaments, the velocity
gradients are found in both CO and CO (J = 2-1) emission,
suggesting that the filament-aligned gravitational collapse toward the central
hub (i.e., C2) is being at work for high-mass star formation therein. Moreover,
a periodic velocity oscillation along the major filament branch is revealed in
both CO and CO (J = 2-1) emission with a characteristic
wavelength of 3.5 pc and an amplitude of 0.31-0.38 km s. We
suggest that this pattern of velocity oscillation in G326 could arise from the
clump-forming gas motions induced by gravitational instability. Taking into
account the prevalent velocity gradients, the fragmentation of the major branch
of filaments, and the ongoing collapse of the three massive dense clumps, it is
indicative that G326 is a HFS undergoing global collapse.Comment: 21 pages, 13 figures, 2 tables, Accepted for publication in Ap
Differential Brain MicroRNA Expression Profiles After Acute and Chronic Infection of Mice With Toxoplasma gondii Oocysts
Brain microRNAs (miRNAs) change in abundance in response to Toxoplasma gondii infection. However, their precise role in the pathogenesis of cerebral infection with T. gondii oocyst remains unclear. We studied the abundance of miRNAs in the brain of mice on days 11 and 33 post-infection (dpi) in order to identify miRNA pattern specific to early (11 dpi) and late (33 dpi) T. gondii infection. Mice were challenged with T. gondii oocysts (Type II strain) and on 11 and 33 dpi, the expression of miRNAs in mouse brain was investigated using small RNA (sRNA) sequencing. miRNA expression was confirmed by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed to identify the biological processes, molecular functions, and cellular components, as well as pathways involved in infection. More than 1,500 miRNAs (1,352 known and 150 novel miRNAs) were detected in the infected and control mice. The expression of miRNAs varied across time after infection; 3, 38, and 108 differentially expressed miRNAs (P < 0.05) were detected during acute infection, chronic infection and chronic vs. acute infection, respectively. GO analysis showed that chronically infected mice had more predicted targets of dysregulated miRNAs than acutely infected mice. KEGG analysis indicated that most predicted targets were involved in immune- or disease-related pathways. Our data indicate that T. gondii infection alters the abundance of miRNAs in mouse brain particularly at the chronic stage, probably to fine-tune conditions required for the establishment of a latent brain infection
Insights into the release of triclosan from microplastics in aquatic environment assessed with diffusive gradient in thin-films
Organic chemicals associated with microplastics (MPs) can be released and thus pose potential risks during weathering processes. However, the thermodynamics and kinetics of their release processes still need to be better understood. Herein, the adsorption and desorption kinetics of triclosan on polystyrene (PS) and polyvinyl chloride (PVC) were investigated by using both batch experiments and diffusive gradients in thin-films (DGT) technique. The pseudo-second-order model fitted the data best, implying that both intraparticle diffusion and external liquid film diffusion influence the adsorption and desorption processes. DGT continuously accumulated triclosan from MP suspensions but slower than theoretical values, indicating some restrictions to desorption. The DGT-induced fluxes in Soils/Sediment (DIFS) model, employed to interpret DGT data, gave distribution coefficients for labile species (K ) of 5000 mL g (PS) and 1000 mL g (PVC) and the corresponding response times (T ) were 10 s and 1000 s, respectively. Higher K but smaller T for PS than PVC showed that more triclosan adsorbed on PS could be rapidly released, while there were some kinetic limitations for triclosan on PVC. A novel finding was that pH and ionic strength individually and interactively affected the supply of triclosan to DGT. This is the first study to quantify interactions of organics with MPs by using DGT, aiding our understanding of MPs' adsorption/desorption behavior in the aquatic environment
Universality class of non-Fermi liquid behavior in mixed valence systems
A generalized Anderson single-impurity model with off-site Coulomb
interactions is derived from the extended three-band Hubbard model, originally
proposed to describe the physics of the copper-oxides. Using the abelian
bosonization technique and canonical transformations, an effective Hamiltonian
is derived in the strong coupling limit, which is essentially analogous to the
Toulouse limit of the ordinary Kondo problem. In this limit, the effective
Hamiltonian can be exactly solved, with a mixed valence quantum critical point
separating two different Fermi liquid phases, {\it i.e.} the Kondo phase and
the empty orbital phase. In the mixed valence quantum critical regime, the
local moment is only partially quenched and X-ray edge singularities are
generated. Around the quantum critical point, a new type of non-Fermi liquid
behavior is predicted with an extra specific heat and a
singular spin-susceptibility . At the same time, the
effective Hamiltonian under single occupancy is transformed into a
resonant-level model, from which the correct Kondo physical properties
(specific heat, spin susceptibility, and an enhanced Wilson ratio) are easily
rederived. Finally, a brief discussion is given to relate these theoretical
results to observations in () alloys, which show
single-impurity critical behavior consistent with our predictions.Comment: 26 pages, revtex, no figure. Some corrections have been made, but the
basic results are kept. To be published in Physical Review
Superconductivity and Charge-density-wave-like Transition in Th2Cu4As5
We report the synthesis, crystal structure, and physical properties of a
novel ternary compound, ThCuAs. The material crystallizes in a
tetragonal structure with lattice parameters {\AA} and
{\AA}. Its structure can be described as an alternating stacking
of fluorite-type ThAs layers with antifluorite-type double-layered
CuAs slabs. The measurement of electrical resistivity, magnetic
susceptibility and specific heat reveals that ThCuAs undergoes bulk
superconducting transition at 4.2 K. Moreover, all these physical quantities
exhibit anomalies at 48 K, where the Hall coefficient change the sign. These
findings suggest a charge-density-wave-like (CDW) transition, making
ThCuAs a rare example for studying the interplay between CDW and
superconductivity.Comment: 11 pages, 6 figures, and 1 tabl
The LAMOST Survey of Background Quasars in the Vicinity of the Andromeda and Triangulum Galaxies -- II. Results from the Commissioning Observations and the Pilot Surveys
We present new quasars discovered in the vicinity of the Andromeda and
Triangulum galaxies with the LAMOST during the 2010 and 2011 observational
seasons. Quasar candidates are selected based on the available SDSS, KPNO 4 m
telescope, XSTPS optical, and WISE near infrared photometric data. We present
509 new quasars discovered in a stripe of ~135 sq. deg from M31 to M33 along
the Giant Stellar Stream in the 2011 pilot survey datasets, and also 17 new
quasars discovered in an area of ~100 sq. deg that covers the central region
and the southeastern halo of M31 in the 2010 commissioning datasets. These 526
new quasars have i magnitudes ranging from 15.5 to 20.0, redshifts from 0.1 to
3.2. They represent a significant increase of the number of identified quasars
in the vicinity of M31 and M33. There are now 26, 62 and 139 known quasars in
this region of the sky with i magnitudes brighter than 17.0, 17.5 and 18.0
respectively, of which 5, 20 and 75 are newly-discovered. These bright quasars
provide an invaluable collection with which to probe the kinematics and
chemistry of the ISM/IGM in the Local Group of galaxies. A total of 93 quasars
are now known with locations within 2.5 deg of M31, of which 73 are newly
discovered. Tens of quasars are now known to be located behind the Giant
Stellar Stream, and hundreds behind the extended halo and its associated
substructures of M31. The much enlarged sample of known quasars in the vicinity
of M31 and M33 can potentially be utilized to construct a perfect astrometric
reference frame to measure the minute PMs of M31 and M33, along with the PMs of
substructures associated with the Local Group of galaxies. Those PMs are some
of the most fundamental properties of the Local Group.Comment: 26 pages, 6 figures, AJ accepte
De novo Transcriptome Characterization of Rhodomyrtus tomentosa Leaves and Identification of Genes Involved in α/β-Pinene and β-Caryophyllene Biosynthesis
Plant-derived terpenes are effective in treating chronic dysentery, rheumatism, hepatitis, and hyperlipemia. Thus, understanding the molecular basis of terpene biosynthesis in some terpene-abundant Chinese medicinal plants is of great importance. Abundant in mono- and sesqui-terpenes, Rhodomyrtus tomentosa (Ait.) Hassk, an evergreen shrub belonging to the family Myrtaceae, is widely used as a traditional Chinese medicine. In this study, (+)-α-pinene and β-caryophyllene were detected to be the two major components in the leaves of R. tomentosa, in which (+)-α-pinene is higher in the young leaves than in the mature leaves, whereas the distribution of β-caryophyllene is opposite. Genome-wide transcriptome analysis of leaves identified 138 unigenes potentially involved in terpenoid biosynthesis. By integrating known biosynthetic pathways for terpenoids, 7 candidate genes encoding terpene synthase (RtTPS1-7) that potentially catalyze the last step in pinene and caryophyllene biosynthesis were further characterized. Sequence alignment analysis showed that RtTPS1, RtTPS3 and RtTPS4 do not contain typical N-terminal transit peptides (62–64aa), thus probably producing multiple isomers and enantiomers by terpenoid isomerization. Further enzyme activity in vitro confirmed that RtTPS1-4 mainly produce (+)-α-pinene and (+)-β-pinene, as well as small amounts of (−)-α-pinene and (−)-β-pinene with GPP, while RtTPS1 and RtTPS3 are also active with FPP, producing β-caryophyllene, along with a smaller amount of α-humulene. Our results deepen the understanding of molecular mechanisms of terpenes biosynthesis in Myrtaceae
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