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Search Results: 1 - 10 of 220282 matches for " De-Hua Wen "
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Properties of hyperon stars rotating at Keplerian frequency

Wen De-Hua,Chen Wei,

中国物理 B , 2011,
Abstract:
Imprints of the nuclear symmetry energy on gravitational waves from the axial w-modes of neutron stars
De-Hua Wen,Bao-An Li,Plamen G. Krastev
Physics , 2009, DOI: 10.1103/PhysRevC.80.025801
Abstract: The eigen-frequencies of the axial w-modes of oscillating neutron stars are studied using the continued fraction method with an Equation of State (EOS) partially constrained by the recent terrestrial nuclear laboratory data. It is shown that the density dependence of the nuclear symmetry energy $E_{sym}(\rho)$ affects significantly both the frequencies and the damping times of these modes. Besides confirming the previously found universal behavior of the mass-scaled eigen-frequencies as functions of the compactness of neutron stars, we explored several alternative universal scaling functions. Moreover, the $w_{II}$-mode is found to exist only for neutron stars having a compactness of $M/R\geq 0.1078$ independent of the EOS used.
One possible mechanism for massive neutron star supported by soft EOS
De-Hua Wen,Jing Yan,Xue-Mei Liu
Physics , 2012, DOI: 10.1142/S0218271812500368
Abstract: The recently discovery of a massive neutron star (PSR J1614-2230 of $1.97\pm0.04M_{\odot}$) rules out the soft equation of states (EOSs) such as those included hyperons or kaon condensates at high densities, while the nuclear theory or the terrestrial laboratory data prefer a soft EOS. Here we propose one possible mechanism to allow that the observed massive neutron star can be supported by a soft EOS, that is, if the the gravitational constant $G$ varies at super strong field, a soft EOS can support the massive neutron stars.
Sensitivity of the neutron star r-mode instability window to the density dependence of the nuclear symmetry energy
De-Hua Wen,W. G. Newton,Bao-An Li
Physics , 2011, DOI: 10.1103/PhysRevC.85.025801
Abstract: Using a simple model of a neutron star with a perfectly rigid crust constructed and a set of crust and core equations of state that span the range of nuclear experimental uncertainty in the density dependence of the symmetry energy from 25 MeV (soft EOS) to 115 MeV (stiff EOS), we calculate the instability window for the onset of the Chandrasekhar-Friedmann-Schutz (CFS) instability in r-mode oscillations for canonical neutron stars (1.4 M_{\odot}) and massive neutron stars (2.0 M_{\odot}). In these models the crust-core transition density, and thus crustal thickness, is calculated consistently with the core equation of state (EOS). For the canonical neutron star, the lower bound of the r-mode instability window is reduced in frequency by \approx150 Hz from the softest to the stiffest symmetry energy used, independent of mass and temperature. The instability window also drops by \approx 100 Hz independent of EOS when the mass is raised from 1.4 M_{\odot} to 2.0 M_{\odot}. Where temperature estimates are available, the observed neutron stars in low mass X-ray binaries (LMXBs) have frequencies below the instability window for the 1.4 M_{\odot} models, while some LMXBs fall within the instability window for 2.0 M_{\odot} stars if the symmetry energy is relatively stiff, indicating that a softer symmetry energy is more consistent with observations within this model. Thus we conclude that smaller values of L help stabilize neutron stars against runaway r-mode oscillations. The critical temperature, below which no star can reach the instability window without exceeding its Kepler frequency, varies by nearly an order of magnitude from soft to stiff symmetry energies. When the crust thickness and core EOS are treated consistently, a thicker crust corresponds to a lower critical temperature, the opposite result to previous studies in which the transition density was independent of the core EOS.
Super-soft symmetry energy encountering non-Newtonian gravity in neutron stars
De-Hua Wen,Bao-An Li,Lie-Wen Chen
Physics , 2009, DOI: 10.1103/PhysRevLett.103.211102
Abstract: Considering the non-Newtonian gravity proposed in the grand unification theories, we show that the stability and observed global properties of neutron stars can not rule out the super-soft nuclear symmetry energies at supra-saturation densities. The degree of possible violation of the Inverse-Square-Law of gravity in neutron stars is estimated using an Equation of State (EOS) of neutron-rich nuclear matter consistent with the available terrestrial laboratory data.
Breaking the EOS-Gravity Degeneracy with Masses and Pulsating Frequencies of Neutron Stars
Weikang Lin,Bao-An Li,Lie-Wen Chen,De-Hua Wen,Jun Xu
Physics , 2013, DOI: 10.1088/0954-3899/41/7/075203
Abstract: A thorough understanding of many astrophysical phenomena associated with compact objects requires reliable knowledge about both the equation of state (EOS)of super-dense nuclear matter and the theory of strong-field gravity simultaneously because of the EOS-gravity degeneracy. Currently, variations of the neutron star (NS) mass-radius correlation from using alternative gravity theories are much larger than those from changing the NS matter EOS within known constraints. At least two independent observables are required to break the EOS-gravity degeneracy. Using model EOSs for hybrid stars and a Yukawa-type non-Newtonian gravity, we investigate both the mass-radius correlation and pulsating frequencies of NSs. While the maximum mass of NSs increases, the frequencies of the $f$, $p_1$, $p_2$, and $w_I$ pulsating modes are found to decrease with the increasing strength of the Yukawa-type non-Newtonian gravity, providing a useful reference for future determination simultaneously of both the strong-field gravity and the supranuclear EOS by combining data of x-ray and gravitational wave emissions of neutron stars.
Can the maximum mass of neutron stars rule out any equation of state of dense stellar matter before gravity is well understood?
De-Hua Wen,Bao-An Li,Lie-Wen Chen
Physics , 2011,
Abstract: Probably No! As an example, using soft EOSs consistent with existing terrestrial nuclear laboratory experiments for hybrid neutron stars containing a quark core described with MIT bag model using reasonable parameters, we show that the recently discovered new holder of neutron star maximum mass PSR J1614-2230 of $1.97\pm0.04M_{\odot}$ can be well described by incorporating a Yukawa gravitational correction that is consistent with existing constraints from neutron-proton and neutron-lead scatterings as well as the spectroscopy of antiproton atoms.
Effect of regulatory dendritic cells on IL-10-producing regulatory B cells of skin allograft in mice
Yu-xiang WEI,Wen-qiang ZHOU,Li XIAO,De-hua ZHENG
Medical Journal of Chinese People's Liberation Army , 2013,
Abstract: Objective  To investigate the effect of recipient immature dendritic cells (imDCs) loaded with PUVA-treated donor apoptotic splenic lymphocytes (PUVA-SP DC) on IL-10+CD19+regulatory B cells (Breg) and the survival duration of skin allograft in mice. Methods  Bone marrow-derived DCs of C57BL/6 mice were obtained from bone marrow cells by co-culturing with recombinant mouse IL-4 and GM-CSF. Spleen lymphocytes (SP) of BALB/c mice were isolated and prepared as PUVA-SP by treating the cells with 8-methoxypsoralen plus ultraviolet A irradiation. The bone marrow-derived imDCs of C57BL/6 mice were co-cultured with PUVA-SP of BALB/c mice to obtain PUVA-SP DCs. The skin allograft model was then established. Animals were randomly grouped according to different pretreatments as follows: the control group was iv. introduction of PBS (0.2ml) alone 7 days before skin transplantation, the PUVA-SP DC group received an iv. injection of PUVA-SP DCs, the maDC (mature DC) group received recipient maDCs, and the imDC group was given recipient imDCs. Mice were monitored daily from day 6 after transplantation for signs of rejection of skin graft. The recipients' peripheral blood serum samples were then collected and the level of cytokines were measured by using ELISA kits. The survival time of skin allograft was evaluated every day. The expression of IL10+CD19+regulatory B cells was analyzed by flow cytometry. Results  After transplantation, the proportion of IL-10+CD19+Breg in the peripheral blood of PUVA-SP DC group was 7.48%, which was obviously higher than that of imDC group (4.12%), maDC group (3.01%) and control group (2.37%). The serum level of cytokine IL-10 in PUVA-SP DC group was 58.2±0.9ng/ml, and it was significantly higher than that in maDC group (20.1±1.6ng/ml), imDC group (26.2±1.3ng/ml) and control group (19.0±0.6ng/ ml, P<0.01). The survival time of allograft in PUVA-SP DC group was 62.3±2.6d, and it was markedly longer than that in maDC group (20.7±1.9d), imDC group (12.1±1.0d) and control group (11.0±1.3d, P<0.01). Conclusions  Administration of PUVASP DCs, in the absence of an immunosuppressant, may significantly delay allograft rejection. This effect is associated with up-regulation of circulating regulatory B cells with preferential IL-10 secretion.
Frame Dragging Effect on Moment of Inertia and Radius of Gyration of Neutron Star
De-hua Wen,Wei Chen,Jian-xun Hu,Liang-gang Liu
Physics , 2005, DOI: 10.1142/S0217732307023225
Abstract: Accurate to the first order in the uniform angular velocity, the general relativity frame dragging effect of the moments of inertia and radii of gyration of two kinds of neutron stars are calculated in a relativistic $\sigma-\omega$ model. The calculation shows that the dragging effect will diminish the moments of inertia and radii of gyration.
Constraints on the symmetry energy from neutron star observations
W. G. Newton,M. Gearheart,De-Hua Wen,Bao-An Li
Physics , 2012, DOI: 10.1088/1742-6596/420/1/012145
Abstract: The modeling of many neutron star observables incorporates the microphysics of both the stellar crust and core, which is tied intimately to the properties of the nuclear matter equation of state (EoS). We explore the predictions of such models over the range of experimentally constrained nuclear matter parameters, focusing on the slope of the symmetry energy at nuclear saturation density $L$. We use a consistent model of the composition and EoS of neutron star crust and core matter to model the binding energy of pulsar B of the double pulsar system J0737-3039, the frequencies of torsional oscillations of the neutron star crust and the instability region for r-modes in the neutron star core damped by electron-electron viscosity at the crust-core interface. By confronting these models with observations, we illustrate the potential of astrophysical observables to offer constraints on poorly known nuclear matter parameters complementary to terrestrial experiments, and demonstrate that our models consistently predict $L<70$ MeV.
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