Golmaenone, a new diketopiperazine alkaloid from the marine-derived fungus Aspergillus sp

A new diketopiperazine alkaloid, golmaenone (1). and related alkaloids, neoechinulin A (2). and L-alanyl-L-tryptophan anhydride (3). have been isolated from the culture broth of the marine-derived fungus Aspergillus sp. The structure and absolute stereochemistry of the new compound (1). was assigned by spectroscopic methods and the advanced Marfey's method. Compounds 1 and 2 exhibited a significant radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) with IC(50) values of 20 and 24 microM, respectively, which are similar to the positive control, ascorbic acid (IC(50), 20 microM). Compounds 1 and 2 also showed an ultraviolet-A (UV-A) (320--390 nm) protecting activity with ED(50) values of 90 and 170 microM, respectively, which are more active than oxybenzone (ED(50), 350 microM) currently being used as sunscreen.     

New farnesylhydroquinone glycosides from the gorgonian Euplexaura anastomosans

Euplexides F (3) and G (4), novel farnesylhydroquinone glycosides, have been isolated as minor constituents of the gorgonian Euplexaura anastomosans. The structures of these compounds have been determined by combined spectroscopic methods. These compounds exhibited moderate cytotoxicity and inhibitory activity against PLA2.     

The energy levels of the heavy flavour baryons in the topological soliton model

The energy levels of the charm and bottom as well as the mixed flavour hyperons are calculated with the model in which the hyperons are described as bound states of a topologicalSU (2) soliton andK-, D- andB-mesons. The spectra are obtained in a modified version of the Skyrme model where the chiral symmetry breaking term in the Lagrangian density is modified so as to incorporate the different values of the decay constants of the mesons of different flavour. The predicted strange and charmed hyperon spectra are in very good agreement with the empirical values, while the bottom hyperon energies that are more sensitive to the short range dynamics are somewhat below the empirical values. The predicted hyperfine spectra are remarkably close to those obtained with the constituent quark model, more or less independently of the short-distance properties of the effective Lagrangian. We suggest that this feature reflects the presence of an induced nonabelian gauge potential generated by the interplay between “fast” and “slow” degrees of freedom in the meson-soliton system.     

Minimum orders of eulerian oriented digraphs with given diameter

A digraph D is oriented if it does not contain 2-cycles.If an oriented digraph D has a directed eulerian path,it is an oriented eulerian digraph.In this paper,when an oriented eulerian digraph D has minimum out-degree 2 and a diameter d,we find the minimum order of D.In addition,when D is 2-regular with diameter 4m(m ≥ 2),we classify the extremal cases.     

Evidence of the primary-color photoluminescence in ion (H,H,C) irradiated and thermal annealed SrTiO3

We have measured photoluminescence (PL) spectrum of (1) thermal-annealed SrTiO₃/Si thin film and undoped SrTiO₃ single crystal; (2) SrTiO₃ single crystal irradiated by high energy (3 MeV) proton, deuterium, and He ion beams and (3) SrTiO₃ single crystal irradiated by low energy (60 keV) H⁺ and C⁻ ions. Two PL emissions are induced in (1) and (2) at visible frequencies 3 and 2.45 eV, while another PL peak is induced at 2 eV in (3). When compared with our previous PL experiments on high-temperature annealed SrTiO₃/SiO₂/Si thin film and 3 MeV proton (H⁺) irradiated STO single crystal, these results confirm that the three PL emissions with blue (3 eV), green (2.45 eV), and red-orange (2 eV) frequencies originate indeed from SrTiO₃. These primary-color PL effect induced at room-temperature makes STO a strong candidate material for future oxide-based optoelectronic application.     

Ru-Catalyzed Hydrogenolysis of Chiral Allylic and Propargylic Cyclic Carbonates: Synthesis of Optically Active (E)-Allylic and Allenic Alcohols

RuH₂(PPh₃)₄-catalyzed reductive cleavage reactions of chiral allylic cyclic carbonates with ammonium formate afforded optically active (E)-allylic alcohols with excellent regioselectivity. Alternatively, hydrogenolysis of propargylic cyclic carbonates in the presence of RuH₂(PPh₃)₄ catalyst afforded allenic alcohols as a sole products.     

Determination of226Ra in environmental samples using high-resolution inductively coupled plasma mass spectrometry

A time-saving and accurate technique for determining²²⁶Ra in groundwater and soil was examined, using high-resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS). The technique was applied to the determination of²²⁶Ra in groundwater and soil samples and compared with the conventional liquid scintillation counting method. This technique was capable of completing²²⁶Ra counting within 3 minutes, without the in-growth period to allow radon and its progeny to achieve secular equilibrium with the parent²²⁶Ra. The detection limits of HR-ICP-MS for²²⁶Ra in groundwater and soil were 0.19 mBq·1⁻¹ and 0.75 Bq·kg⁻¹, respectively, which were about 10 times lower than that of the liquid scintillation counter. The results obtained from HR-ICP-MS in groundwater and soil were in accordance with those of LSC within a relative error of about 13%.