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An ohmic-heating laser ion source with a thin ionizer of thickness of 30 μm has been developed for the TIARA-ISOL. It can form an electric field of 4–5 V/cm inside the ionizer. The properties of the laser ion source were tested on- and off-line with aluminum isotopes. The FWHM of the time distribution of the bunched photoions from the ion source was about 4 μs for 27Al. In on-line experiment, a photoionization efficiency of about 0.1% for 25Al was obtained.

The production yield of endohedral 133 Xe-fullerene by ion implantation has been studied by taking advantage of the radioactivity of 133 Xe. Fullerene targets, which were produced by vacuum evaporation of C 60 or C 70 on a Ni backing, were bombarded with 30–38 keV 133 Xe ions by using an isotope separator at doses ranging from 1 × 10 12 to 1 × 10 14 cm −2 . The production yield of endohedral 133 Xe-fullerene was determined by an high performance liquid chromatography analysis following the dissolution of the targets in o -dichlorobenzene. It was found that the production yield decreased with increasing dose and incident energy, and the production yield of 133 Xe@C 70 was higher than that of 133 Xe@C 60 for the same dose and incident energy. Those production yields are discussed in connection with amorphization of fullerene molecules in collisions with 133 Xe ions.

Ion implantation was applied to the production of endohedral 133Xe-fullerene. Using an isotope separator, 133Xe ions were implanted into a fullerene target of C60 and C70 produced by vacuum evaporation on a Ni backing. An HPLC analysis following dissolution of the fullerene targets in o-dichlorobenzene corroborated the formation of 133Xe@C60 and 133Xe@C70, showing a strong correlation between C60/C70 and 133Xe. The observed tailing following 133Xe peaks in the elution curves suggests a possibility of the isolation of endohedral 133Xe-fullerene from empty fullerene.

The effects of anion channel blockers, 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS) and anthracene-9-carboxylic acid (A-9-C), on the uptake and xylem transport of nitrate were investigated in intact barley (Hordeum vulgare L.) seedlings using 13NO3 − and 15NO3 − as tracers. The seedling roots were pretreated with either blocker for 1 h and then 13NO3 − or 15NO3 − was supplied to the medium. Real-time images of 13N accumulation in shoots were monitored during the first 30 min using Positron Emitting Tracer Imaging Systems (PETIS). The radioactivity in the shoots of the plants treated with either blocker was about half of that in the shoots of the control plants. Analysis of the distribution of 13N in whole seedlings using a Bioimaging Analyzer System (BAS) showed a 13N-accumulation in both shoots and roots of the control plants but reduced 13N-levels in the shoots of the plants treated with either blocker. Nitrate concentrations in the xylem sap were significantly reduced by the appli...

The β+/EC decay of 126 La produced by the 94 Mo( 36 Ar, 3pn) reaction has been studied using the on-line isotope separator connected to an AVF cyclotron. Gamma-ray singles, γ–γ angular correlation and internal conversion electron measurements were carried out. From analysis of these data, 33 new levels in 126 Ba were found and the decay scheme containing 137 γ-rays and 50 excited states was constructed. The probable spin and parity of the two β-decaying states in 126 La were found to be 4±, 5± for the high-spin isomer with a half-life of 54(2) s and 0−, 1±, 2− for the low-spin isomer with a half-life shorter than 50 s.

Water (H 2 15 O) translocation from the roots to the top of rice plants (Oryza saliva L. cv. Nipponbare) was visualized over time by a positron-emitting tracer imaging system (PETIS). H 2 15 O flow was activated 8 min after plants were exposed to bright light (1500 μmol m -2 s -1 ). When the light was subsequently removed, the flow gradually slowed and completely stopped after 12 min. In plants exposed to low light (500 μmol m -2 s -1 ), H 2 15 O flow was activated more slowly, and a higher translocation rate of H 2 15 O was observed in the same low light at the end of the next dark period. NaCI (80 mM) and methylmercury (1 mM) directly suppressed absorption of H 2 15 O by the roots, while methionine sulfoximine (1 mM), abscisic acid (10 pM) and carbonyl cyanide m-chlorophenylhydrazone (10 mM) were transported to the leaves and enhanced stomatal closure, reducing H 2 15 O translocation.

A new method to normalize coincidence counts for γ–γ angular correlations measured with a multiple-Ge detector system is described. This method uses characteristic KX-rays emitted following internal conversion or electron capture, which exhibit a coincidence with γ-rays and an isotropic KX-γ angular correlation. Only the ratios between KX-ray counts and γ-ray counts of interest in the same gated spectra are used to deduce normalized coincidence intensities, and any other quantities such as detector efficiencies, γ-ray singles counts and other kinds of efficiencies are not required. Performance of this method was tested in on-line experiments using mass-separated 126La and 128La sources.

The ammonium ion is an indispensable nitrogen source for crops, especially paddy rice ( Oryza sativa L. cv Nipponbare). Until now, it has been impossible to measure ammonium uptake and nitrogen movement in plants in real time. Using the new technologies of PETIS (positron emitting tracer imaging system) and PMPS (positron multi-probe system), we were able to visualize the real time translocation of nitrogen and water in rice plants. We used positron-emitting 13 N-labeled ammonium ( 13 NH 4 + ) and 15 O-water to monitor the movement. In plants cultured under normal conditions, 13 NH 4 + supplied to roots was taken up, and a 13 N signal was detected at the discrimination center, the basal part of the shoots, within 2 minutes. This rapid translocation of 13 N was almost completely inhibited by a glutamine synthetase inhibitor, methionine sulfoximine. In general, nitrogen deficiency enhanced 13 N translocation to the discrimination center. In the dark, 13 N translocation to the discrimination center was suppressed to 40% of control levels, whereas 15 O-water flow from the root to the discrimination center stopped completely in the dark. In abscisic acid-treated rice, 13 N translocation to the discrimination center was doubled, whereas translocation to leaves decreased to 40% of control levels. Pretreatment with NO 3 − for 36 hours increased 13 N translocation from the roots to the discrimination center to 5 times of control levels. These results suggest that ammonium assimilation (from the roots to the discrimination center) depends passively on water flow, but actively on NH 4 + -transporter(s) or glutamine synthetase(s).

We present real time vanadate (V5+ ) uptake imaging in acowpea plant by positron emitting tracer imaging system (PETIS). Vanadium-48was produced by bombarding a Sc foil target with 50 MeV α -particlesat Takasaki Ion Accelerators for Advanced Radiation Application (TIARA) AVFcyclotron. Then 48 V was added to the culture solution to investigatethe V distribution in a cowpea plant. The real time uptake of the 48V was monitored by PETIS. We measured the distribution of 48Vin a whole plant after 3, 6 and 20 hours of V treatment by Bio-imaging AnalyzerSystem (BAS). After the 20 hour treatment, vanadate was detected at the up-groundpart of the plant. To know the effect of V uptake on plant activity, 18F-labeled water uptake was analyzed by PETIS. When a cowpea plantwas treated with V for 20 hours before 18 F-labeled water uptakeexperiment, the total amount of 18F-labeled water absorption wasdrastically decreased. Results suggest the inhibition of water uptake wasmainly caused by the vanadate already moved to the up-ground part of the plant.

15P-water flow from the roots to the top in tomato (Lycopersicon esculentum Mill.) and rice (Oryza sativa L.) plants was visualized with time using a positron-emitting tracer imaging system (PETIS). The 15O-water flow was switched on by light and completely stopped in the dark. The flow rate in the stem of tomato and the shoot of rice at a light intensity of 500 μmol·m−2·s−1 was 1.9 and 0.4 cm min−1, respectively.

The positron emitting tracer-imaging system (PETIS) was used to determine whether it was possible to obtain on image of 13N-distribution in common bean in which a single root was fed with a liquid medium containing nitrate at different concentrations with different 13N specific activities. The distribution of the images of the 13N atoms in the root could be obtained over a wide range of nitrate concentrations and 13N specific activities in the medium. As for nitrate stress on leguminous root nodulation, the positional relationship between the nitrate uptake sites and root hair just elongating area, where rhizobia capably initiate their infection, was studied in common bean and soybean. PETIS gave direct evidence that single roots of both common bean and soybean showed one or two dense 13N-distribution areas after 2 min pulse-feeding of 13N03 -. These areas remained stable over 30 min, and the first dense site, which was common in all the examined roots, extended over ca. 1 cm above the root apex....

The ALICE code was used to calculate the excitation functions for proton induced reactions on 100Mo that lead to the production of Nb, Mo and Tc isotopes. The ALICE code predicts a maximum cross section of the order of 100 mb for the 100Mo(p,pn)99Mo nuclear reaction. ALICE predicts that the production of a few Curies of 99Mo is feasible if high intensity (mA) protons are degraded from 50→30 MeV in a target of highly isotopically enriched 100Mo. The ALICE code cannot be used to predict the cross sections for the isomeric states for the 100Mo(p, 2p)99m+gNb→99Mo reactions. However, the predicted cross section for protons on 100Mo to yield 99Nb suggests that the (p,2p) reaction channel does not contribute significantly to the thick target yield of 99Mo. Several considerations suggest that accelerator production of 99Mo→99mTc generators is not a practical economic alternative to fission produced 99Mo. Considerations for the cyclotron production of 99mTc are discussed.

A coronary stent was made radioactive by implantation of 133Xe ions for the purpose of suppressing the re-narrowing of the part of blood vessel in which the stent is implanted. Electrons of relatively low energies emitted in the decay of 133Xe may give an antiproliferative effect of ionizing radiation to the intimal cells within a limited range of 1 mm. A 133Xe+ beam accelerated at 40 or 60 keV was directed to several stainless steel stents mounted on a target-holder table that could revolve and move up and down to distribute the 133Xe+ ions within a stent as well as among the stents. The radioactive stents produced contained up to 100 kBq of 133Xe and were implanted into the abdominal aortas of rabbits. Neointimal thickening was analyzed by histomorphometry for samples taken 4 weeks after stent implantation. The results indicate that the radioactive stents have a potential to suppress neointimal hyperplasia in rabbits.

The recently discovered family of RGS (regulators of G protein signaling) proteins acts as GTPase activating proteins which bind to alpha subunits of heterotrimeric G proteins. We previously showed that a brain-specific RGS, RGS8 speeds up the activation and deactivation kinetics of the G protein-coupled inward rectifier K+ channel (GIRK) upon receptor stimulation (Saitoh, O., Kubo, Y., Miyatani, Y., Asano, T., and Nakata, H. (1997) Nature 390, 525-529). Here we report the isolation of a full-length rat cDNA of another brain-specific RGS, RGS7. In situ hybridization study revealed that RGS7 mRNA is predominantly expressed in Golgi cells within granule cell layer of cerebellar cortex. We observed that RGS7 recombinant protein binds preferentially to Galphao, Galphai3, and Galphaz. When co-expressed with GIRK1/2 in Xenopus oocytes, RGS7 and RGS8 differentially accelerate G protein-mediated modulation of GIRK. RGS7 clearly accelerated activation of GIRK current similarly with RGS8 but the acceleration effect of deactivation was significantly weaker than that of RGS8. These acceleration properties of RGS proteins may play important roles in the rapid regulation of neuronal excitability and the cellular responses to short-lived stimulations.

Mossbauer effect measurements for the 81 keV transition in133Cs have been performed with133Xe-implanted sources prepared by means of an electromagnetic isotope separator. The behavior of the isomer shift of133Cs impurities was studied in various metals. Some correlations were found between measured isomer shifts and electronic properties of the host materials, and they show that the host conduction electrons have an important role in the determination of the isomer shift in metals.

The positron emitters11C,13N and18F and their labeled compounds have been produced for studies on plants using a newly developed positron emitting tracer imaging system. Although this system covers, at present, a limited area in a plant, the distribution of the positron emitter fed into the plant can be visualized dynamically. Further development of positron-emitter-labeled compounds is expected to elucidate the physiological function of plants in vivo.

We have measured the polarization of unstable nuclei produced by the technique of ion beam surface interaction at grazing incidence (IBSIGI). A 60 keV 124Cs beam from the on-line mass separator was used. The NMR technique was employed for the observation of the nuclear polarization. A small polarization of 0.22(13)% was observed. The small value was interpreted in terms of the velocity dependence of nuclear polarization, comparing with the results observed with stable nuclei.

Studies on the decay of unstable nuclei using the two on-line isotope separators of JAERI are reviewed for the past five years. With the previously established ion-source technique using mono-oxide ion formation in a thermal ion source, the new nuclides125Pr and127Pr have been identified in heavy-ion fusion residues. Further, with a newly developed gas-jet coupled thermal ion source, the new nuclides166Tb,165Gd,161Sm and236Am have been identified by bombarding238U and235U targets with a proton or6Li beam. Other studies, including off-line experiments, by decay spectroscopy, laser spectroscopy and Mossbauer spectroscopy are described.

For neutron-deficient 124,125,127-130 La, Q EC measurement has been performed by determining β + -ray maximum energies. The radioactive sources were prepared by on-line mass-separation following the fusion-evaporation reactions 92, nat Mo( 36 Ar, 3 p x n ). The β + -rays were measured with an HPGe detector in β-γ coincidence mode in which γ-rays were detected with another HPGe detector for specifying an excited state in daughter nucleus. By unfolding the β + -ray spectra using experimental response functions, the Q EC -values of 124, 125, 127, 130 La were newly obtained, and those of 128, 129 La were improved in their accuracy. The Q EC -values obtained and the resulting atomic masses are compared with theoretical predictions. The results of half-life calculation and two-neutron separation energies using the experimental Q EC -values are also discussed.

Beta-ray endpoint energies of the neutron-deficient nuclide of 126La have been measured with an HPGe detector. The 126La activities were produced by the 94Mo(36Ar, 3pn) reaction and mass-separated on-line. From the β-γ coincidence measurements, QEC values of the high- and low-spin isomers of 126La were determined for the first time to be 7700 ± 100 keV and 7910 ± 400 keV, respectively. The experimental atomic masses were compared with predicted values of mass formulas.

A simple retardation system has been constructed in order to realize low-energy ion-implantations using an electro-magnetic isotope separator (EMIS). Mass-separated ions are decelerated through a smoothly increasing potential which is produced in a box which is coated inside with a highly resistive film. To test the performance of the system, 133Xe ions retarded from 20 keV by a maximum of 15 keV were implanted into a nickel foil covered by a thin copper layer, and their mean range in copper was determined with a radiochemical technique. The observed ranges are in good agreement with theoretical prediction, which manifests that the system works well as expected.

Low-spin states in ${}^{124,126,128,130}\mathrm{Ba}$ fed by the $\mathrm{EC}/{\ensuremath{\beta}}^{+}$ decay of their La parents have been investigated by means of the \ensuremath{\gamma}-\ensuremath{\gamma} angular correlation measurement coupled with an isotope separator on-line. The spin of the first excited ${0}^{+}$ states ${(0}_{2}^{+})$ were unambiguously established, and higher-excited ${0}^{+}$ states were newly identified. The energy of the ${0}_{2}^{+}$ state in ${}^{124}\mathrm{Ba}$ previously assigned was revised upward. Resultingly, the level energy of the ${0}_{2}^{+}$ state in neutron-deficient Ba nuclei takes a minimum at $N=72$ and then gradually increases toward neutron midshell $(N=66),$ while the level energy of the ${0}_{3}^{+}$ state rapidly decreases with decreasing neutron number. From an extrapolation of these ${0}^{+}$ energies, it is highly expected that the energy relation between the ${0}_{2}^{+}$ and ${0}_{3}^{+}$ state would invert at ${}^{122}\mathrm{Ba}$ or at more deformed Ba nuclei. This energy inversion is interpreted as the evolution of the ${0}_{2}^{+}$ state in \ensuremath{\gamma}-soft nuclei toward the two-phonon \ensuremath{\gamma}-vibrational ${0}^{+}$ state in axially-symmetric deformed nuclei, while the ${0}_{3}^{+}$ state toward the \ensuremath{\beta}-vibrational ${0}^{+}$ state.

A multiple-detector system for γ−γ angular correlation measurements has been constructed to study low-spin states populated via the β-decay of mass-separated short-lived nuclei using an isotope separator on-line. The system consists of five-HPGe detectors which are configured at fixed angles to provide ten correlation angles of 90°, 100°, 110°, 120°, 130°, 130°, 140°, 150°, 160° and 170° simultaneously, and with short source-to-detector distance to enlarge the detection efficiencies. The performance of the system was studied with an 152 Eu source in off-line experiments. The contribution of finite solid angle of detectors, random coincidences and Compton-scattered γ-rays were appropriately corrected. Difference in the coincidence efficiency among various detector pairs was experimentally evaluated, and it was concluded that this difference was almost negligible in this system. In an on-line experiment, low-spin states in 126 Ba populated via the β + -decay of 126 La were investigated with this system.

The transport of a positron-emitting isotope introduced into a plant was dynamically followed by a special observation apparatus called ‘Positron-Emitting Tracer Imaging System’ to observe the damage and recovery functions of plants in vivo. In the system, annihilation γ-rays from the positron emitter are detected with two planar detectors (5 × 6 cm2). The water containing ca. 5 MBq/ml of 18F was fed to the cut stem of soybean for 2 min and then the images of tracer activity were recorded for 30–50 min. When the midrib of a leaf near the petiole was cut just before measurement, the activity in the injured leaf was decreased but detected even at the apex. This result suggests that the damaged leaf recovered the uptake of water through the lamina. Maximum tracer activities in leaves of unirradiated plant were observed within 10 min, whereas those of irradiated plant at 100 Gy were observed after over 25 min. The final activity of irradiated plant after 30 min was lower than that of unirradiated plant. In case of beans, there was a difference in the absorption behavior of the 18F-labeled water between unirradiated and irradiated samples. These results show that the system is effective to observe the uptake and transportation of water containing positron emitting tracer for the study of damage and recovery functions of plants.

We are developing a hot-cavity type laser ion source (LIS) for the on-line isotope separation of heavy-ion-reaction products. To optimize the efficiency of the LIS, a lens, which enlarges the laser irradiation volume, was introduced; the lens focuses the laser beams at an orifice of the cavity, which is opposite to the ion extraction orifice, and expand them inside. With a stable 139 La isotope, we performed off-line experiments and observed the LIS providing pulsed ion beams, the full width of which was less than 1 μs.

Strain THI201, a member of the alphaproteobacteria, is a novel thiocyanate (SCN(-))-degrading bacterium isolated from lake water enriched with potassium thiocyanate (KSCN). This bacterium carries the enzyme thiocyanate hydrolase (SCNase) that hydrolyses thiocyanate to carbonyl sulfide and ammonia. Characterization of both native and recombinant SCNase revealed properties different from known SCNases regarding subunit structure and thermostability: SCNase of strain THI201 was composed of a single protein and thermostable. We cloned and sequenced the corresponding gene and determined a protein of 457 amino acids of molecular mass 50 267 Da. Presence of a twin-arginine (Tat) signal sequence of 32 amino acids was found upstream of SCNase. The deduced amino acid sequence of SCNase showed 83% identity to that of a putative uncharacterized protein of Thiobacillus denitrificans ATCC 25259, but no significant identity to those of three subunits of SCNase from Thiobacillus thioparus strain THI115. The specific activities of native and recombinant enzyme were 0.32 and 4-15 µmol min(-1) (mg protein)(-1), respectively. The maximum activity of SCNase was found in the temperature range 30-70 °C. The thiocyanate-hydrolysing activity in both enzymes was decreased by freeze-thawing, although 25-100% of the activity of recombinant protein could be retrieved by treating the enzyme at 60 °C for 15 min. Furthermore, both native and recombinant enzymes retained the activity after pre-treatment of the protein solution at temperatures up to 70 °C.

No-Carrier-Added186Re was produced using the186W(p,n)186Re nuclear reaction with 13.6 MeV protons on thick targets of 99.79% isotopically enriched186WO3. The theoretical excitation functions for producing186Re, and possible radionuclidic impurities of182Re,183Re, and184Re were calculated using the ALICE code. Cross-sections of the186W(p,n)186Re reaction were measured up to 20 MeV using the stacked target method with thin foils of natural composition tungsten metal. The experimental and theoretical excitation functions were in good agreement. Targetry used at the TIARA cyclotron, and a radiochemical separation scheme for186Re are described.

No-carrier-added tantalum-183 was produced free of radiotantalum impurities by the 186 W(p,α) 183 Ta nuclear reaction using 13.6 MeV protons on thick targets of isotopically enriched 186 WO 3 . The proton energy was optimum for the simultaneous production of 186 Re and 183 Ta. The ALICE code was used to theoretically determine the optimum irradiation conditions for the production of 183 Ta with proton and deuteron nuclear reactions. A Bio-imaging analyser was used to illustrate the migration of 183 Ta species into a grass plant ( Cyperus microiria steud). 183 Ta has potential applications as a tracer for ecotoxicity studies, and for developmental studies for radiotantalum pharmaceuticals.

The β + decay of 127,126,125 Pr was studied for on-line mass-separated sources. The decay scheme of 127 Pr reported previously was revised from the results of a more-detailed analysis of the experimental data. The 125 Pr isotope was newly identified with a half-life of 3.3(7) s and its decay scheme is presented. The γ band in 126 Ce was identified in the decay of 126 Pr and its properties are compared with the prediction of the interacting boson model 2.

A new isotope,127Pr, has been identified and its decay has been studied using on-line isotope separation of94Mo (36Ar,p2n) reaction products. The half-life of the isotope was determined to be 7.7(6) s, and a γ/X-ray spectrum has been obtained. A partial level scheme is proposed for127Ce on the basis ofγ-singles,β-gatedγ andγγ-coincidence data.

To obtain fundamental data for the research of the transmutation of nuclear waste, the thermal neutron cross section and the resonance integral of the reaction 137Cs(n, γ)138Cs have been measured by means of a modified Cd-ratio technique. Targets of about 0.4 MBq 137Cs were irradiated with neutrons in the JRR-4 swimming pool reactor by using a pneumatic tube equipped with a movable Cd shield, and neutron fluxes and their epithermal neutron fractions were monitored with activation detectors (Co/Al and Au/Al) whose sensitivity to epithermal neutrons differed from each other. After irradiation, the 137Cs samples were purified chemically and their γ-ray spectra were measured with a high purity Ge detector. The resulting yields of 138Cs for different neutron spectra and the neutron flux data have yielded that the thermal neutron cross section (for 2,200 m/s neutrons) is 0.25±0.02b and the resonance integral 0.36±0.07b. The results are consistent with the effective cross section (σ=0.250±0.013b) of our...

For the purpose of achieving a good efficiency and pulsed output of short-lived reaction products, we propose a laser-enhanced ion-guide ion source for an on-line isotope separator. Two-step resonant, three-color resonance ionization of Ba atoms was established in an off-line experiment and the ionization efficiency per pulse was measured to be 1.9%. In an on-line ion-guide experiment, it was found that the use of heavy gas was effective to stop the recoil atoms and that most of them remain in the gas until evacuation. While enhancement of the ionization efficiency by introduction of a laser beam to the ion-guide chamber has not been achieved so far, possible improvements are discussed.

Hold-up times of ions in a thermal ion source were measured for lanthanum and cerium together with neighboring elements in the periodic table. The hold-up times of metallic and monoxide ions of both lanthanum and cerium were found to be almost the same and much longer than those of cesium, barium, praseodymium and neodymium ions. The observed long hold-up times of lanthanum and cerium ions were ascribed to long sticking times of atoms on a cavity wall.

A mass separator has been connected on line to the 20 MV tandem accelerator at JAERI/Tokai. Using a thermal ion source, decay spectroscopic studies have been carried out for neutron-deficient isotopes in the mass 120–130 region. A study with collinear laser spectroscopy has begun recently. The present paper describes the status of the mass separator facility together with some experimental results.

Level energies and γ-transition properties in the low-lying states of 123 Ba have been investigated through the decay of 123 La. From γ-ray singles and γ-γ coincidence measurements of the 123 La produced in the 35 Cl+ 92 Mo reaction and an on-line mass-separation technique, 12 new levels haye been assigned in the level scheme of 123 Ba. The [411]1/2 + band, consisting of 6 members, has been proposed.

Mass yield curves in low-energy proton-induced fission of $^{233}\mathrm{U}$, $^{235}\mathrm{U}$, $^{236}\mathrm{U}$, $^{237}\mathrm{Np}$, $^{239}\mathrm{Pu}$, $^{242}\mathrm{Pu}$, $^{244}\mathrm{Pu}$, $^{241}\mathrm{Am}$, and $^{243}\mathrm{Am}$ were investigated in the energy range of 8--32 MeV. The gross features of mass yield curves were compared either at the same excitation energy or for the same charge of the compound nucleus with different neutron number. The results are briefly discussed in terms of (1) the weighted mean mass number of the light and heavy asymmetric peak, (2) the FWHM of the heavier asymmetric peak, and (3) the peak-to-valley ratio.

Formation cross sections of 95m Tc and 95g Tc via the 95 Mo (p, n) reaction have been measured to evaluate the production yield of 95m Tc which is expected to be a useful radiotracer of technetium isotopes. It was found from the cross section data that for incident proton energies above 15 MeV, the thick-target yield of 95m Tc was more than 20 μCi/μAh at the end of bombardment and the 95g Tc contamination was less than 1% after 12 d cooling. To examine the separation and purification of 95m Tc from target, we have carried out a test production of 95m Tc using a thick 95 Mo-enriched target. Other reactions of producing 95m Tc are compared and discussed in terms of the production yield and amounts of contaminants.

To investigate a feature of the symmetric mass division at high angular momentum, distributions of mass, angular and total kinetic energy have been measured with a time-of-flight telescope for the products of symmetric mass division in the 37 Cl+ 68 Zn and 16 O+ 89 Y reactions. The widths of the mass and totalkinetic energy distributions are broader than those expected from the liquid drop model.

Kinetic energy, angular and charge distributions have been measured for complex fragments (5 ⩽ Z ⩽ 29) produced in the 37 Cl induced reactions on 68 Zn at laboratory bombarding energies of 156, 166 and 177MeV. The characteristics of the fragments observed at backward angles are consistent with those of the decay products from an equilibrium compound nucleus. The charge distributions of these products are reproduced by the statistical model calculation which takes account of the potential energy associated with mass asymmetry and angular momentum. The influence of angular momentum on the width of the charge (mass) distributions for symmetric mass division is discussed.

The Positron-Emitting Tracer Imaging System (PETIS) is introduced for monitoring the distribution of (11)C-labelled photoassimilates in Sorghum. The obtained two-dimensional image data were quantitatively analysed using a transfer function analysis approach. While one half of a Sorghum root in a split root system was treated with either 0, 100, or 500 mM NaCl dissolved in the nutrient solution, tracer images of the root halves and the lower stem section were recorded using PETIS. From the observed tracer levels, parameters were estimated, from which the mean speed of tracer transport and the proportion of tracer moved between specified image positions were deduced. Transport speed varied between 0.7 and 1.8 cm min(-1) with the difference depending on which part of the stem was involved. When data were collected in the lowest 0.5-1 cm of the stem, which included the point where the roots emerge, transport speed was less. Rapid changes in NaCl concentration, from 0 to 100 mM, resulted in short-term increases of assimilate import into the treated root. This response represented a transient osmotic effect, that was compensated for in the medium-term by osmotic adaptation. Higher concentrations of NaCl (500 mM) resulted in distinctly less photoassimilate transport into the treated root half. The present results agree with earlier observations, showing that transport of (11)C-labelled photoassimilates measured with the PETIS detector system can be quantified using the method of input-output analysis. It is worth noting that with the PETIS detector system, areas of interest do not need to be defined until after data collection. This means that unexpected behaviour of a plant organ will be seen, which is not necessarily the case with conventional detector systems looking at predefined areas of interest.

The upper part of a nodulated soybean root hydroponically cultured in a glass bottle was monitored using a computer microscope under controlled environmental conditions, and the diameter of individual nodules was measured from 10-24 d after planting. The diameter of a root nodule attached to the primary root increased from 1 mm to 6 mm for 2 weeks under nitrogen-free conditions. The increase in diameter of the nodules was almost completely stopped after 1 d of supplying 5 mM nitrate, and was due to the cessation of nodule cell expansion. However, nodule growth quickly returned to the normal growth rate following withdrawal of nitrate from the solution. The reversible depression of nodule growth by nitrate was similar to the restriction of photoassimilate supply by continuous dark treatment for 2 d followed by normal light/dark conditions. In addition, the inhibitory effect of nitrate was partially alleviated by the addition of 3% (w/v) sucrose to the medium. Plant leaves were exposed to (11)C or (14)C-labelled carbon dioxide to investigate the effects of 5 mM nitrate on the translocation and distribution of photosynthates to nodules and roots. Supplying 5 mM nitrate stimulated the translocation rate and the distribution of labelled C in nitrate-fed parts of the roots. However, the (14)C partitioning to nodules decreased from 9% to 4% of total (14)C under conditions of 5 mM nitrate supply. These results indicate that the decrease in photoassimilate supply to nodules may be involved in the quick and reversible nitrate inhibition of soybean nodule growth.

Quantitative analysis of the two-dimensional image data obtained with the positron-emitting tracer imaging system (PETIS) for plant physiology has been carried out using a transfer function analysis method. While a cut leaf base of Chinese chive (Allium tuberosum Rottler) or a cut stem of soybean (Glycine max L.) was immersed in an aqueous solution containing the [18F] F− ion or [13N]NO3− ion, tracer images of the leaf of Chinese chive and the trifoliate of soybean were recorded with PETIS. From the time sequence of images, the tracer transfer function was estimated from which the speed of tracer transport and the fraction moved between specified image positions were deduced.

Decay spectroscopy using on-line mass separators has the advantage of allowing the study of level properties in the low energy region, including band head information, since g transitions between low-spin states can be measured more intensively under lower background conditions than can those with in-beam spectroscopy measurements. Neutron-deficient nuclides of 125,127 Ba have been studied by means of in-beam spectroscopy, and the level structures for high-spin states were successfully interpreted within the framework of the IBFM model @1‐5#. Decay studies of these nuclides have rarely been reported. Therefore, the last evaluations in Refs. @6, 7# were mainly based on in-beam studies. In 1991, the possibility of static octupole deformation, similar to that of the A5145 and 225 regions proposed, was proposed for the A5130 region by Cottle @8#. The presence of static octupole deformation is represented by parity doublets, which have equal spins and opposite parity levels of rotational bands with alternating bands. The E1 transitions between parity doublets are characterized by a two to four orders of magnitude enhancement compared to those of more normal cases. The 127‐130 Ba isotopes were successively studied by in-beam conversion electron measurements to investigate for parity doublets, and no evidence of them was observed @9,10#. These studies, however, focused only on the conversion electron measurements; the transition probabilities were not measured. It is necessary to measure not only the conversion electrons, but also the half-lives of the excited states in order to explain this feature. The aim of this investigation was to study the level properties of 125,127 Ba in the low energy region, focusing on a search for E1 transitions, and to study their properties by measuring the half-lives of low-lying excited states. The half-lives and conversion electrons were measured for the first time through the decays of 125,127 La, by means of a delayed coincidence technique and a cooled Si~Li! detector, respectively. The expected enhanced E1 transitions were not observed. Level properties based on the Nilsson model are proposed.