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81.
We discuss three different ways to arrive at kaon condensation at nc?3n0 where n0 is nuclear matter density: (1) Fluctuating around the n=0 vacuum in chiral perturbation theory, (2) fluctuating around nVM near the chiral restoration density nχ where the vector manifestation of hidden local symmetry is reached and (3) fluctuating around the Fermi liquid fixed point at ∼n0. They all share one common theoretical basis, “hidden local symmetry”. We argue that when the critical density nc<nχ is reached in a neutron star, the electrons turn into K− mesons, which go into an s-wave Bose condensate. This reduces the pressure substantially and the neutron star goes into a black hole. Next we develop the argument that the collapse of a neutron star into a black hole takes place for a star of M?1.5M⊙. This means that Supernova 1987A had a black hole as result. We also show that two neutron stars in a binary have to be within 4% of each other in mass, for neutron stars sufficiently massive that they escape helium shell burning. For those that are so light that they do have helium shell burning, after a small correction for this, they must be within 4% of each other in mass. Observations support the proximity in mass inside of a neutron star binary. The result of strangeness condensation is that there are ∼5 times more low-mass black-hole, neutron-star binaries than double neutron-star binaries although the former are difficult to observe. 相似文献
82.
Qualitative aspects of quantum corrections to the Lee-Wick abnormal nuclear matter are studied in terms of many-body forces in the normal nuclear matter implied by the σ-model Lagrangian field theory. Using a simplified model for the scalar meson self-energy in the nuclear medium and restricting to a set of graphs which in non-relativistic normal nuclear matter reduces to the well-known random phase approximation (RPA), we have found that an abnormal nuclear state can be bound or unbound depending upon whether strongly attractive multi-body forces are present or absent in the normal matter. This is in support of our previous result obtained heuristically from some general considerations of quantum corrections. A strongly bound abnormal matter with an equilibrium density of a few times the normal nuclear matter density ρ0 can be formed if large attractive manybody forces can be accommodated in the normal nuclear matter. However if one accepts the present status of theories of nuclear matter binding energy in which no attractive many-body forces are called for, then the abnormal state can occur only at large densities (perhaps 8 to 10 times ρ0) and is expected to be unbound by several hundred MeV per particle. 相似文献
83.
A model is employed to describe the velocity dependence of the effective nucleon-nucleon interaction in nuclear matter. The interactions in this model consist of π? and ρ-meson exchange, together with short-range correlations induced by the strongly repulsive potential resulting from ω-meson exchange. With known coupling strengths, these interactions produce an effective mass in nuclear matter.Through the formalism of Fermi liquid theory, the exchange-current correction to the orbital g-factor, δgl, can be described in terms of the velocity dependence in the neutron-proton interaction, and, within the model, this can be related to the effective mass . With , the δgl for the proton turns out to be 0.22, 45% of it coming from π-meson exchange.Additional contributions to in nuclei come from the coupling of vibrations to quasiparticles; these are especially important in the nuclear surface, and tend to increase the effective mass, when averaged over both nuclear volume and surface, so that . In so far as these contributions arise from isovector vibrations, we can use the same model as for π- and ρ-meson exchange, and show that the same relation between and δgl holds, so that for , δgl = 0. The contributions from coupling to vibrations will depend upon the single-particle state, however; states of high-angular momentum will tend to have and δgl > 0.Finally, the enchancement δgl in gl can be connected with the enhancement k in the dipole sum rule originating from the giant-resonance region. This connection is not very precise, but gives a small positive κ ~ 0.2. 相似文献
84.
We demonstrate the amplification of a femtosecond signal pulse in an underdense plasma by a novel mechanism called superradiant amplification. The pulse is amplified by a counterpropagating few picosecond long pump pulse. In the superradiant regime, the ponderomotive forces exceed the electrostatic forces and arrange the plasma electrons to reflect the pump light into the signal pulse. We found a significant amplification in energy and intensity. The time structure of the amplified signal pulse carries intrinsic features of the superradiant regime. Sub-10-fs pulses of petawatt power appear feasible. 相似文献
85.
Cellular DNA topoisomerase I is an important target in cancer chemotherapy. A chloroform extract of the root barks of Cudrania tricuspidata showed an inhibitory effect on mammalian DNA topoisomerase I. The topoisomerase I inhibitory compound was purified and identified as 2',5,7-trihydroxy-4',5'-(2,2-dimethylchromeno)-8-(3-hydroxy-3-methylbutyl) flavanone. The compound, temporarily designated as PKH-3, was shown to inhibit the activity of topoisomerase I with IC50 about 1.0 mM. Concentration of 10 microM PKH-3 caused 50% growth inhibition of human cancer cell U937. PKH-3-induced cell death was characterized with the cleavage of poly(ADP-ribose) polymerase (PARP) and pro-caspase 3. Furthermore, PKH-3 induced the fragmentation of DNA into multiples of 180 b.p. (an apoptotic DNA ladder), indicating that the inhibitor triggered apoptosis. This induction of apoptosis by PKH-3 was also confirmed using flow cytometry analysis. Taken together, these results suggest that PKH-3 may function by inhibiting oncogenic disease, at least in part, through the inhibition of topoisomerase I activity. 相似文献
86.
Balawant S. Joshi Taikyun Rho Peter L. Rinaldi Weixia Liu Todd A. Wagler M. Gary Newton Doowon Lee S. William Pelletier 《Journal of chemical crystallography》1997,27(9):553-559
The structure of the π-molecular complex (10) was assigned on the basis of the solid state13C-nmr spectrum. The solid state13C-nmr spectrum of quinhydrone (12) has also been determined. Accurate1H and13C chemical shift assignments have been made for the compounds3,5,6,7,8, and10 on the basis of HMQC and HMBC spectral data. The π-molecular complex10 crystallizes in the space groupP21 In with cell parameters:a=4.052 (1) Å,b=6.477 (1) Å,c=19.093 (2) Å, β=90.17 (1)o,z=1,D c =1.400 g mc?32. Crystal and molecular structure of the title compound, C28H22O4, has been determined by an X-ray analysis of10 by direct methods from diffractometer data and refined by full-matrix least-squares 相似文献
87.
88.
Hyung Jin Lim Eun-Jae Park Yeong-Seon Won Seon Gyeong Bak Sun Hee Cheong Seung Woong Lee Soyoung Lee Seung-Jae Lee Mun-Chual Rho 《Molecules (Basel, Switzerland)》2021,26(22)
Osteoporosis is characterized by the deterioration of bone structures and decreased bone mass, leading to an increased risk of fracture. Estrogen deficiency in postmenopausal women and aging are major factors of osteoporosis and are some of the reasons for reduced quality of life. In this study, we investigated the effects of n-trans-hibiscusamide (NHA) and its derivative 4-O-(E)-feruloyl-N-(E)-hibiscusamide (HAD) on receptor activator of nuclear factor kappa-Β (NF-κB) ligand (RANKL)-induced osteoclast differentiation and an ovariectomized osteoporosis mouse model. NHA and HAD significantly inhibited the differentiation of osteoclasts from bone marrow-derived macrophages (BMMs) and the expression of osteoclast differentiation-related genes. At the molecular level, NHA and HAD significantly downregulated the phosphorylation of mitogen-activated protein kinase (MAPK) signaling molecules. However, Akt and NF-κB phosphorylation was inhibited only after NHA or HAD treatment. In the ovariectomy (OVX)-induced osteoporosis model, both NHA and HAD effectively improved trabecular bone structure. C-terminal telopeptide (CTX), a bone resorption marker, and RANKL, an osteoclast stimulation factor, were significantly reduced by NHA and HAD. The tartrate-resistant acid phosphatase (TRAP)-stained area, which indicates the osteoclast area, was also decreased by these compounds. These results show the potential of NHA and HAD as therapeutic agents for osteoporosis. 相似文献
89.
90.
We report Raman scattering results of wurtzite ZnS nanowires, nanocombs, and nanobelts. The Raman spectrum obtained from ZnS nanowires exhibits first‐order phonon modes at 272, 284, and 350 cm−1, corresponding to A1/E1 transverse optical, E2 transverse optical, and A1/E1 longitudinal optical phonons, respectively. Several multiphonon modes are also observed. The longitudinal optical phonon mode varies in wavenumber for nanocombs and nanobelts, indicating that the residual strain varies during the morphological change from ZnS nanowires to nanocombs and ultimately to nanobelts. Interestingly, a surface optical (SO) phonon mode varies in wavenumber depending on the shape and surface roughness of the ZnS nanostructures. The surface modulation wavelengths of the ZnS nanowires, nanocombs, and nanobelts are estimated using the SO phonon dispersion relations and the observed SO phonon wavenumbers. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献