In vivo temporal EPR imaging for estimating the kinetics of a nitroxide radical in the renal parenchyma and pelvis in rats

The kinetics of a nitroxide radical in the renal parenchyma and pelvis in rats were investigated by employing an in vivo EPR imaging system equipped with a surface-coil-type resonator (SCR). The exposed kidney of a living rat was inserted into the single-turn coil of the SCR, with the renal major axis aligned with the direction of alternative magnetic field (B(1)). After the injection of nitroxide radical via the tail vein, EPR measurements were repeated. From the temporal EPR images of the kidney on the 2-D projection to the plane which is perpendicular to the direction of B(1,) the decay rate of nitroxide radical in the renal parenchyma and pelvis was estimated. The parenchymal decay rate was found to be significantly shorter than that for the pelvis.     

Chaotic transition in a three-coupled phase-locked loop system

The chaotic transition is observed in a three-coupled phase-locked loop (PLL) system in both experiments and numerical simulations. In this system, three PLL oscillators are connected with the periodic boundary condition. Intermittency is found in partially synchronized phase, in which two of three oscillators synchronize with each other and form a pair, and the chaotic transition occurs due to the recombination of synchronized pairs so that different pair is re-formed. In this phase, on-off intermittency is also observed and statistical analyses are carried out for on-off intermittent time series. This intermittency is considered as a hybrid type of intermittency with both on-off intermittency and intermittency due to the recombination of synchronized pairs present in the same time series. We also show the chaotic transition phenomena in a three-coupled logistic map system. (c) 2001 American Institute of Physics.     

Non-destructive observation of electrically detected magnetic resonance in bulk material using AC bias

DC bias is normally found in conventional measurements of electrically detected magnetic resonance (EDMR). Usually, electrodes are formed on the sample surface to make ohmic contacts for detecting changes in the electrical characteristics of the sample material. Thus, destructive procedures are required to detect the EDMR signal of bulk material with such methods. An AC bias detection technique was developed to allow the non-destructive EDMR measurement of bulk materials. An AC bridge circuit was constructed to detect the change in impedance of the sample, which when changed by ESR, an unbalanced AC voltage can be detected. By detecting this AC bias, it is possible to cancel the effects, such as Shottky barriers, that disturb the ohmic contact between the electrodes and a sample material. Further, the AC bias current penetrates the thin surface layer of a sample such as silicon oxide, which normally obstructs a DC current. This method was utilized using conductive rubber contacts for non-destructive EDMR measurements of part of a silicon wafer. EDMR spectra observed were the same as those obtained by the conventional method of using DC bias detection.     

Routine charged particle activation analysis of light elements

In order to develop a highly reliable method of routine charged particle activation analysis on a commercial basis by request of an outside company, (1) a new target holder was developed for brittle or low melting-point samples, (2) some modifications and improvements were introduced in the chemical separation, and (3) the reliability of the results was further examined. Oxygen, nitrogen, carbon, and boron in a greater variety of matrices have thus become analyzable with a higher reliability and efficiency.     

A series of search designs for 2m factorial designs of resolution V which permit search of one or two unknown extra three-factor interactions

In the absence of four-factor and higher order interactions, we present a series of search designs for 2^m factorials (m6) which allow the search of at most k (=1,2) nonnegligible three-factor interactions, and the estimation of them along with the general mean, main effects and two-factor interactions. These designs are derived from balanced arrays of strength 6. In particular, the nonisomorphic weighted graphs with 4 vertices in which two distinct vertices are assigned with integer weight (13), are useful in obtaining search designs for k=2. Furthermore, it is shown that a search design obtained for each m6 is of the minimum number of treatments among balanced arrays of strenth 6. By modifying the results for m6, we also present a search design for m=5 and k=2.     

Adaptation of the sheet resistance of an YBaCuO layer to the substrate impedance, applications

We have studied the Far Infrared transmission spectra of an MgO plate covered with an YBaCuO film of thickness t=200 Å, at different temperatures. By cooling from room temperature to temperatures < 140 K, the Far Infrared interference fringes are displaced by half a period. Explanation in terms of different adaptations of the YBaCuO sheet resistance to the MgO substrate impedance during cooling.     

Identification of (6R)‐5,6,7,8‐Tetrahydro‐D‐monapterin (=(6R)‐2‐Amino‐5,6,7,8‐tetrahydro‐6‐[(1R,2R)‐1,2,3 ‐trihydroxypropyl]pteridin‐4(3H)‐one) as the Native Pteridine in Tetrahymena pyriformis

The structure of the native pteridine in Tetrahymena pyriformis was determined as (6R)‐5,6,7,8‐tetrahydro‐D ‐monapterin (=(6R)‐2‐amino‐5,6,7,8‐tetrahydro‐6‐[(1R,2R)‐1,2,3‐trihydroxypropyl]pteridin‐4(3H)‐one; 4 ). First, the configuration of the 1,2,3‐trihydroxypropyl side chain was confirmed as D ‐threo by the fluorescence‐detected circular dichroism (FDCD) spectrum of its aromatic pterin derivative 2 obtained by I₂ oxidation (Fig. 1). The configuration at the 6‐position of 4 was determined as (R) by comparison of its hexaacetyl derivative 6 with authentic (6R)‐ and (6S)‐hexaacetyl‐5,6,7,8‐tetrahydro‐D ‐monapterins 6 and 7 , respectively, in the HPLC, LC/MS, and LC‐MS/MS (Figs. 3 – 6). (6R)‐5,6,7,8‐Tetrahydro‐D ‐monapterin ( 4 ) is a newly discovered natural tetrahydropterin.     

Twin LC Resonator System for EPR Measurements Operating at Radio-Frequency

Two LC resonant circuits resonating at the same frequency (245 MHz) faced each other with reverse polarity (twin electron paramagnetic resonance (EPR) resonator). For the inductor of the LC circuit, a square single-turn one-loop coil (width, 38 mm) was fabricated. Each LC circuit was independently tuned using mechanical variable capacitors. A cylindrical phantom (diameter, 25 mm) including a 1 mM nitroxide radical physiological saline solution was located at the center of two coils (distance between these coils, 50 mm). Two resonant frequencies (the lower and the higher ones) were observed at each LC circuit of the twin EPR resonator with termination of the other LC circuit. The lower resonant frequency alone was observed when the powers from two LC circuits of the twin EPR resonator were combined by a 180° combiner. On the other hand, the higher frequency alone was observed when they were combined by a 0° combiner. EPR signals could be obtained using the 180° combiner (lower frequency) but not the 0° combiner (higher frequency).     

ΛN and ΣN Interactions from Lattice QCD

We present our recent study on ΛN and ΣN (isospin I = 3/2) interactions by measuring Nambu–Bethe–Salpeter wave functions on the Lattice QCD. The lattice QCD calculation is performed by using the N _f  = 2 + 1 gauge configurations generated by PACS-CS collaboration together with employing an improved method to obtain potentials in lattice QCD simulations. For the ¹ S ₀ channel, the central ΣN (I = 3/2) potential and the central ΛN (¹ S ₀) potential are found to be very similar. For the spin triplet (³ S ₁?³ D ₁) channels, the central ΛN(³ S ₁?³ D ₁) potential is attractive while the central ΣN(I = 3/2, ³ S ₁?³ D ₁) potentials is repulsive. Tensor potentials, on the other hand, are rather weak in both ΛN and ΣN(I = 3/2) systems.