Phenolic constituents of licorice. VIII. Structures of glicophenone and glicoisoflavanone, and effects of licorice phenolics on methicillin-resistant Staphylococcus aureus

Two new phenolic compounds, glicophenone (1) and glicoisoflavanone (2), were isolated from commercial licorice, and their structures were elucidated on the basis of spectroscopic data. Antibacterial assays of licorice phenolics for Staphylococcus aureus, including four strains of methicillin-resistant S. aureus (MRSA), and also for Escherichia coli K12 and Pseudomonas aeruginosa PAO1, were then examined. Two compounds among them, 8-(gamma,gamma-dimethylallyl)-wighteone (21) and 3'-(gamma,gamma-dimethylallyl)-kievitone (28), showed remarkable antibacterial effects [minimum inhibitory concentrations (MICs), 8 microg/ml on the MRSA strains and methicillin-sensitive S. aureus. Licochalcone A (14), gancaonin G (20), isoangustone A (24), glyasperins C (30) and D (31), glabridin, (32), licoricidin (33), glycycoumarin (34) and licocoumarone (40) showed antibacterial effects on the MRSA strains with MIC values of 16 microg/ml. Effects on the beta-lactam resistance of the MRSA strains were also examined, and licoricidin (33) noticeably decreased the resistance of the MRSA strains against oxacillin, as shown by the reduction in the MICs of oxacillin (lower than 1/128-1/1000 in the presence of 8 microg/ml of 33, and 1/8-1/32 in the presence of 4 microg/ml of 33). Mechanistic study suggested that 33 does not inhibit the formation of penicillin-binding protein 2' (PBP2'), but affects the enzymatic function of PBP2'.     

Three-dimensional GaN-Ga2O3 core shell structure revealed by x-ray diffraction microscopy

In combination of direct phase retrieval of coherent x-ray diffraction patterns with a novel tomographic reconstruction algorithm, we, for the first time, carried out quantitative 3D imaging of a heat-treated GaN particle with each voxel corresponding to 17 x 17 x 17 nm3. We observed the platelet structure of GaN and the formation of small islands on the surface of the platelets, and successfully captured the internal GaN-Ga2O3 core shell structure in three dimensions. This work opens the door for nondestructive and quantitative imaging of 3D morphology and 3D internal structure of a wide range of materials at the nanometer scale resolution that are amorphous or possess only short-range atomic organization.     

Determination of optical isomers for left-handed or right-handed chiral double-wall carbon nanotubes

The handedness relationship between adjacent layers in nested double-wall carbon nanotubes (DWNTs) has been investigated for the first time. Our high-resolution electron microscopy analysis on a series of specimen tilts can successfully tell the handedness of each constituent nanotube in a DWNT, and therefore the chiral indices (n, m) including their optical isomers [(n, m) or (m, n)] of inner and outer nanotubes can be uniquely determined. It is shown that right-handed and left-handed nanotubes are equally distributed for both the inner and outer nanotubes in the examined specimens and a preferable handedness relationship between the adjacent layers in DWNT may exist.     

Neutron spin echo measurements of monolayer and capillary condensed water in MCM-41 at low temperatures

Neutron spin echo measurements of monolayer and capillary condensed heavy water (D(2)O) confined in MCM-41 C10 (pore diameter 2.10 nm) were performed in a temperature range of 190-298 K. The intermediate scattering functions were analyzed by the Kohlrausch-Williams-Watts stretched exponential function. The relaxation times of confined D(2)O in the capillary condensed state follow remarkably well the Vogel-Fulcher-Tammann equation between 298 and 220 K, whereas below 220 K they show an Arrhenius type behavior. That is, the fragile-to-strong (FTS) dynamic crossover occurs, which has never been seen in experiments on bulk water. On the other hand, for monolayer D(2)O, the FTS dynamic crossover was not observed in the temperature range measured. The FTS dynamic crossover observed in capillary condensed water would take place in the central region of the pore, not near the pore surface. Because the tetrahedral-like water structure in the central region of the pore is more preserved than that near the pore surface, the FTS dynamic crossover would be concerned with the tetrahedral-like water structure.     

Large four-wave mixing of spatially extended excitonic states in thin GaAs layers

We study the size dependence of the nonlinear response of weakly confined excitons for the size region beyond the long wavelength approximation regime. The observed degenerate-four-wave mixing signal of GaAs thin layers exhibits an anomalous size dependence, where the signal is resonantly enhanced at a particular thickness region. The theoretical analysis elucidates that this enhancement is due to the size-resonant enhancement of the internal field with a spatial structure relevant to the nondipole-type excitonic state. These results establish the formerly proposed new type of size dependence of nonlinear response due to the nonlocality induced double resonance.     

Measurement of fusion excitation functions of 27, 29, 31Al + 197Au

A systematic study of the sub-barrier fusion reactions with neutron-rich projectiles has been carried out for three isotopes ^27,29,31Al bombarding a ¹⁹⁷Au target. A target chamber equipped with a target stack and sets of MWPC was employed in order to enhance the efficiency of the radioactive beam experiment. Coupled-channel calculations including the quadrupole excitations do not well fit the measured fusion excitation functions, whereas flat barrier distributions to represent the coupling to the neutron transfer largely account for the observed enhancement of the sub-barrier fusion cross-sections. Received: 13 March 2001 / Accepted: 27 April 2001     

Development of copolymer of CR-39 with high sensitivity to low let particles

Several types of copolymers of CR-39 were prepared to find its usefulness as a nuclear track detector of high sensitivity. Track responses of these copolymers were investigated by irradiating energetic ions from proton through Ar. The copolymer of CR-39 monomer with N-isopropylacrylamide (NIPAAm) shows higher sensitivity than that of pure CR-39 for low LET particles such as protons. Preliminary results are reported for the track responses of copolymers (CR-39/NIPAAm) with various contents of NIPAAm as well as the etching properties.     

Feasibility of self-correcting quantum memory and thermal stability of topological order

Recently, it has become apparent that the thermal stability of topologically ordered systems at finite temperature, as discussed in condensed matter physics, can be studied by addressing the feasibility of self-correcting quantum memory, as discussed in quantum information science. Here, with this correspondence in mind, we propose a model of quantum codes that may cover a large class of physically realizable quantum memory. The model is supported by a certain class of gapped spin Hamiltonians, called stabilizer Hamiltonians, with translation symmetries and a small number of ground states that does not grow with the system size. We show that the model does not work as self-correcting quantum memory due to a certain topological constraint on geometric shapes of its logical operators. This quantum coding theoretical result implies that systems covered or approximated by the model cannot have thermally stable topological order, meaning that systems cannot be stable against both thermal fluctuations and local perturbations simultaneously in two and three spatial dimensions.     

Comparison of accuracy of intravoxel incoherent motion and apparent diffusion coefficient techniques for predicting malignancy of head and neck tumors using half-Fourier single-shot turbo spin-echo diffusion-weighted imaging

Purpose

To evaluate the use of the intravoxel incoherent motion (IVIM) technique in half-Fourier single-shot turbo spin-echo (HASTE) diffusion-weighted imaging (DWI), and to compare its accuracy to that of apparent diffusion coefficient (ADC) to predict malignancy in head and neck tumors.

Patients and methods

HASTE DW images of 33 patients with head and neck tumors (10 benign and 23 malignant) were evaluated. Using the IVIM technique, parameters (D, true diffusion coefficient; f, perfusion fraction; D*, pseudodiffusion coefficient) were calculated for each tumor. ADC values were measured over a range of b values from 0 to 1000 s/mm². IVIM parameters and ADC values in benign and malignant tumors were compared using Student's t test, receiver operating characteristics (ROC) analysis, and multivariate logistic regression modeling.

Results

Mean ADC and D values of malignant tumors were significantly lower than those of benign tumors (P < 0.05). Mean D* values of malignant tumors were significantly higher than those of benign tumors (P < 0.05). There was no significant difference in mean f values between malignant and benign tumors (P > 0.05). The technique of combining D and D* was the best for predicting malignancy; accuracy for this model was higher than that for ADC.

Conclusions

The IVIM technique may be applied in HASTE DWI as a diagnostic tool to predict malignancy in head and neck masses. The use of D and D* in combination increases the diagnostic accuracy in comparison with ADC.