286 research outputs found
The NGC 4013 tale: a pseudo-bulged, late-type spiral shaped by a major merger
Many spiral galaxy haloes show stellar streams with various morphologies when
observed with deep images. The origin of these tidal features is discussed,
either coming from a satellite infall or caused by residuals of an ancient,
gas-rich major merger. By modelling the formation of the peculiar features
observed in the NGC 4013 halo, we investigate their origin. By using GADGET -2
with implemented gas cooling, star formation, and feedback, we have modelled
the overall NGC 4013 galaxy and its associated halo features. A gas-rich major
merger occurring 2.7-4.6 Gyr ago succeeds in reproducing the NGC 4013 galaxy
properties, including all the faint stellar features, strong gas warp,
boxy-shaped halo and vertical 3.6 mum luminosity distribution. High gas
fractions in the progenitors are sufficient to reproduce the observed thin and
thick discs, with a small bulge fraction, as observed. A major merger is able
to reproduce the overall NGC 4013 system, including the warp strength, the red
colour and the high stellar mass density of the loop, while a minor merger
model cannot. Because the gas-rich model suffices to create a pseudo-bulge with
a small fraction of the light, NGC 4013 is perhaps the archetype of a late-type
galaxy formed by a relatively recent merger. Then late type, pseudo-bulge
spirals are not mandatorily made through secular evolution, and the NGC 4013
properties also illustrate that strong warps in isolated galaxies may well
occur at a late phase of a gas-rich major merger.Comment: 11 pages,9 figures,accepted for publication in MNRA
Could M31 be the result of a major merger?
We investigated a scenario in which M31 could be the remnant of a gas-rich
major merger. Galaxy merger simulations, highly constrained by observations,
were run using GADGET 2 in order to reproduce M31. We succeeded in reproducing
the global shape of M31, the thin disk and the bulge, and in addition some of
the main M31 large-scale features, such as the thick disk, the 10kpc ring and
the Giant Stream. This lead to a new explanation of the Giant Stream which
could be caused by tidal tail stars that have been captured by the galaxy
potential.Comment: Proceedings for the conference "Assembling the puzzle of the Milky
Way", 2 page
Outstanding supercapacitive properties of Mn-doped TiO2 micro/nanostructure porous film prepared by anodization method.
Mn-doped TiO2 micro/nanostructure porous film was prepared by anodizing a Ti-Mn alloy. The film annealed at 300 °C yields the highest areal capacitance of 1451.3 mF/cm(2) at a current density of 3 mA/cm(2) when used as a high-performance supercapacitor electrode. Areal capacitance retention is 63.7% when the current density increases from 3 to 20 mA/cm(2), and the capacitance retention is 88.1% after 5,000 cycles. The superior areal capacitance of the porous film is derived from the brush-like metal substrate, which could greatly increase the contact area, improve the charge transport ability at the oxide layer/metal substrate interface, and thereby significantly enhance the electrochemical activities toward high performance energy storage. Additionally, the effects of manganese content and specific surface area of the porous film on the supercapacitive performance were also investigated in this work
Empirical analysis of current status data for additive hazards model with auxiliary covariates
summary:In practice, it often occurs that some covariates of interest are not measured because of various reasons, but there may exist some auxiliary information available. In this case, an issue of interest is how to make use of the available auxiliary information for statistical analysis. This paper discusses statistical inference problems in the context of current status data arising from an additive hazards model with auxiliary covariates. An empirical log-likelihood ratio statistic for the regression parameter vector is defined and its limiting distribution is shown to be a standard chi-squared distribution. A profile empirical log-likelihood ratio statistic for a sub-vector of the parameters and its asymptotic distribution are also studied. To assess the finite sample performance of the proposed methods, simulation studies are implemented and simulation results show that the methods work well
The vast thin plane of M31 co-rotating dwarfs: an additional fossil signature of the M31 merger and of its considerable impact in the whole Local Group
The recent discovery by Ibata et al. (2013) of a vast thin disk of satellites
(VTDS) around M31 offers a new challenge for the understanding of the Local
Group properties. This comes in addition to the unexpected proximity of the
Magellanic Clouds (MCs) to the Milky Way (MW), and to another vast polar
structure (VPOS), which is almost perpendicular to our Galaxy disk. We find
that the VTDS plane is coinciding with several stellar, tidally-induced streams
in the outskirts of M31, and, that its velocity distribution is consistent with
that of the Giant Stream (GS). This is suggestive of a common physical
mechanism, likely linked to merger tidal interactions, knowing that a similar
argument may apply to the VPOS at the MW location. Furthermore, the VTDS is
pointing towards the MW, being almost perpendicular to the MW disk, as the VPOS
is.
We compare these properties to the modelling of M31 as an ancient, gas-rich
major merger, which has been successfully used to predict the M31 substructures
and the GS origin. We find that without fine tuning, the induced tidal tails
are lying in the VTDS plane, providing a single and common origin for many
stellar streams and for the vast stellar structures surrounding both the MW and
M31. The model also reproduces quite accurately positions and velocities of the
VTDS dSphs. Our conjecture leads to a novel interpretation of the Local Group
past history, as a gigantic tidal tail due to the M31 ancient merger is
expected to send material towards the MW, including the MCs. Such a link
between M31 and the MW is expected to be quite exceptional, though it may be in
qualitative agreement with the reported rareness of MW-MCs systems in nearby
galaxies.Comment: Accepted for publication in MNRAS, 8 pages, 3 figure
Triptolide ameliorates lipopolysaccharide-induced acute lung injury in rats
BACKGROUND: Acute lung injury (ALI) is a serious clinical syndrome with a high rate of mortality. In this study, the effects of triptolide on lipopolysaccharide (LPS)-induced ALI in rats were investigated. METHODS: Sixty-five male Sprague Dawley rats(approved by ethics committee of the First Affiliated Hospital of Soochow University) were randomly divided into five groups. The control group was injected with 2.5 mL saline/kg body weight via the tail vein and intraperitoneally with 1% dimethyl sulfoxide (DMSO) (n = 5). The L group was administered with 0.2% LPS dissolved in saline (5 mg/kg) to induce ALI via the tail vein (n = 15). The TP1, TP2, and TP3 groups were treated as rats in the L group and then intraperitoneally injected with 25, 50, and 100 μg triptolide/kg body weight, respectively (15 rats per group). Blood samples from the left heart artery were taken for blood gas analysis at 1 hour before injection and at 1, 3, 6, and 12 hours after saline and DMSO administration in the control group, LPS injection in the L group, and triptolide injection in the TP1, TP2, and TP3 groups. Lung wet-to-dry weight (W/D) ratio, diffuse alveolar damage (DAD) score, TNF-α levels, and mRNA and protein expression of toll-like receptor 4 (TLR4) were analyzed. RESULTS: Compared with the control group, the arterial partial pressure of oxygen (PaO(2)) declined (P <0.05), the W/D ratio and DAD score increased (P <0.05), and TNF-α levels in serum and bronchoalveolar lavage fluid (BALF) and mRNA and protein expression of TLR4 were significantly increased in the L group (P <0.05). Compared with the L group, PaO(2) significantly increased in the TP2 and TP3 groups (P <0.05), while the W/D ratio and DAD score were significantly decreased in the TP2 and TP3 groups (P <0.05). TNF-α levels and mRNA and protein expression of TLR4 were significantly decreased in the TP2 and TP3 groups compared with the L group (P <0.05). CONCLUSIONS: Triptolide can ameliorate LPS-induced ALI by reducing the release of the inflammatory mediator TNF-α and inhibiting TLR4 expression
Revisiting mass estimates of the Milky Way
We use the rotation curve from Gaia data release (DR) 3 to estimate the mass
of the Milky Way. We consider an Einasto density profile to model the dark
matter component. We extrapolate and obtain a dynamical mass
at kpc. This lower-mass
Milky Way is consistent with the significant declining rotation curve, and can
provide new insights into our Galaxy and halo inhabitants.Comment: 4 pages, 2 figures, Accepted for publication in proceedings of IAU
Symposium 379: Dynamical Masses of Local Group Galaxies, Potsdam, March
20-24, 202
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A Hybrid Machine Learning-Based Method for Classifying the Cushing's Syndrome With Comorbid Adrenocortical Lesions
Background: The prognosis for many cancers could be improved dramatically if they could be detected while still at the microscopic disease stage. It follows from a comprehensive statistical analysis that a number of antigens such as hTERT, PCNA and Ki-67 can be considered as cancer markers, while another set of antigens such as P27KIP1 and FHIT are possible markers for normal tissue. Because more than one marker must be considered to obtain a classification of cancer or no cancer, and if cancer, to classify it as malignant, borderline, or benign, we must develop an intelligent decision system that can fullfill such an unmet medical need. Results: We have developed an intelligent decision system using machine learning techniques and markers to characterize tissue as cancerous, non-cancerous or borderline. The system incorporates learning techniques such as variants of support vector machines, neural networks, decision trees, self-organizing feature maps (SOFM) and recursive maximum contrast trees (RMCT). These variants and algorithms we have developed, tend to detect microscopic pathological changes based on features derived from gene expression levels and metabolic profiles. We have also used immunohistochemistry techniques to measure the gene expression profiles from a number of antigens such as cyclin E, P27KIP1, FHIT, Ki-67, PCNA, Bax, Bcl-2, P53, Fas, FasL and hTERT in several particular types of neuroendocrine tumors such as pheochromocytomas, paragangliomas, and the adrenocortical carcinomas (ACC), adenomas (ACA), and hyperplasia (ACH) involved with Cushing's syndrome. We provided statistical evidence that higher expression levels of hTERT, PCNA and Ki-67 etc. are associated with a higher risk that the tumors are malignant or borderline as opposed to benign. We also investigated whether higher expression levels of P27KIP1 and FHIT, etc., are associated with a decreased risk of adrenomedullary tumors. While no significant difference was found between cell-arrest antigens such as P27KIP1 for malignant, borderline, and benign tumors, there was a significant difference between expression levels of such antigens in normal adrenal medulla samples and in adrenomedullary tumors. Conclusions: Our frame work focused on not only different classification schemes and feature selection algorithms, but also ensemble methods such as boosting and bagging in an effort to improve upon the accuracy of the individual classifiers. It is evident that when all sorts of machine learning and statistically learning techniques are combined appropriately into one integrated intelligent medical decision system, the prediction power can be enhanced significantly. This research has many potential applications; it might provide an alternative diagnostic tool and a better understanding of the mechanisms involved in malignant transformation as well as information that is useful for treatment planning and cancer prevention
Dynamic Resource Management in CDRT Systems through Adaptive NOMA
This paper introduces a novel adaptive transmission scheme to amplify the
prowess of coordinated direct and relay transmission (CDRT) systems rooted in
non-orthogonal multiple access principles. Leveraging the maximum ratio
transmission scheme, we seamlessly meet the prerequisites of CDRT while
harnessing the potential of dynamic power allocation and directional antennas
to elevate the system's operational efficiency. Through meticulous derivations,
we unveil closed-form expressions depicting the exact effective sum throughput.
Our simulation results adeptly validate the theoretical analysis and vividly
showcase the effectiveness of the proposed scheme.Comment: 11 pages, 7 figures, submitted to IEEE journal for revie
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