Phorbasones A and B, sesterterpenoids isolated from the marine sponge Phorbas sp. and induction of osteoblast differentiation

Two new sesterterpenoids, phorbasones A (1) and B (2), were isolated from the Korean marine sponge Phorbas sp. Their complete structures were elucidated by spectral data and chemical reactions. Phorbasone A exhibited a positive effect on the calcium deposition activity in C3H10T1/2 cells. The biogenic origin of the core structure is believed to be through a novel rearrangement from the ansellone carbon structure.     

Regioselective Deoxygenation of the Cyclic Thionocarbonates of 2,3-Dihydroxy Esters with Magnesium in Methanol

Deoxygenation of the cyclic thionocarbonates of 2,3-dihydroxy esters was mediated with magnesium in methanol, which provided a facile method for the synthesis of α-hydroxy esters     

Effect of Si doping on epitaxial lateral overgrowth of GaN: A spatially resolved micro-Raman scattering study

We report spatially resolved Raman scattering from Si-doped epitaxial laterally overgrown GaN structures to investigate spatial variations in stress and free electron concentration. The doping-induced increase in the free electron concentration is relatively higher in the laterally overgrown regions than in the coherently grown regions due to the increased contribution of the high-energy A₁ longitudinal optical phonon–plasmon coupled mode. In addition, the E₂(high) [E₂(low)] phonon energy shifts downward (upward) more significantly in the laterally overgrown regions than in the coherently grown regions. The doping-induced Raman shifts of the E₂(high) and E₂(low) phonons in the laterally overgrown regions are approximately ?0.6 and 0.11 cm^?1, respectively, corresponding to the in-plane stress of ～0.22 GPa.     

Dynamical response of multi-patch, flux-based models to the input of infected people: Epidemic response to initiated events

The time course of an epidemic can be modeled using the differential equations that describe the spread of disease and by dividing people into “patches” of different sizes with the migration of people between these patches. We used these multi-patch, flux-based models to determine how the time course of infected and susceptible populations depends on the disease parameters, the geometry of the migrations between the patches, and the addition of infected people into a patch. We found that there are significantly longer lived transients and additional “ancillary” epidemics when the reproductive rate R is closer to 1, as would be typical of SARS (Severe Acute Respiratory Syndrome) and bird flu, than when R is closer to 10, as would be typical of measles. In addition we show, both analytical and numerical, how the time delay between the injection of infected people into a patch and the corresponding initial epidemic that it produces depends on R.     

Recent developments on kaon condensation and its astrophysical implications

We discuss three different ways to arrive at kaon condensation at _nc?3_n0$n_c?3n_0$ where _n0$n_0$ is nuclear matter density: (1) Fluctuating around the n=0$n=0$ vacuum in chiral perturbation theory, (2) fluctuating around _nVM$n_{VM}$ near the chiral restoration density _nχ$n_{\chi }$ where the vector manifestation of hidden local symmetry is reached and (3) fluctuating around the Fermi liquid fixed point at ∼_n0$\sim n_0$. They all share one common theoretical basis, “hidden local symmetry”. We argue that when the critical density _nc<_nχ$n_c<n_{\chi }$ is reached in a neutron star, the electrons turn into K⁻$K^{-}$ 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?1.5_M⊙$M?1.5M_{\odot }$. 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$\sim 5$ times more low-mass black-hole, neutron-star binaries than double neutron-star binaries although the former are difficult to observe.     

Abnormal nuclear matter and many-body forces

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.     

Velocity dependence of the nucleon-nucleon interaction,exchange currents and enhancement of the dipole sum rule in nuclei

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 $\text{m}{}^1\text{/m = 0.75}$ in nuclear matter.Through the formalism of Fermi liquid theory, the exchange-current correction to the orbital g-factor, δg_l, 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 $\text{m}{}^1$. With $\text{m}{}^1\text{/m = 0.75}$, the δg_l for the proton turns out to be 0.22, 45% of it coming from π-meson exchange.Additional contributions to $\text{m}{}^1\text{/m}$ 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 $\text{〈m}{}^1\text{/m〉}{}_{\mathrm{<mtext>av.</mtext>}}\text{? 1}$. 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 $\text{m}{}^1\text{/m}$ and δg_l holds, so that for $\text{〈m}{}^1\text{/m〉}{}_{\mathrm{<mtext>av.</mtext>}}\text{= 1}$, δg_l = 0. The contributions from coupling to vibrations will depend upon the single-particle state, however; states of high-angular momentum will tend to have $\text{〈m}{}^1\text{/m〉}{}_{\mathrm{<mtext>av.</mtext>}}\text{< 1}$ and δg_l > 0.Finally, the enchancement δg_l 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.     

2',5,7-Trihydroxy-4',5'-(2,2-dimethylchromeno)-8-(3-hydroxy-3-methylbutyl) flavanone purified from Cudrania tricuspidata induces apoptotic cell death of human leukemia U937 cells

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.