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Effects of high temperatures on the fluorescence Fm (maximum fluorescence) and Fo (dark level fluorescence) levels were studied and compared with those of the photochemical reactions of PS II. These comparisons were performed during and after the high temperature treatments. The following results were obtained; (1) increases in the Fo level at high temperatures were partly reversible, (2) the Fm level in the presence of dithionite in spinach chloroplasts decreased at high temperatures and also showed a partial reversibility, (3) photoreductions of pheophytin a and Qa were reversibly inhibited at high temperatures parallel to the decrease in the difference between the Fm and Fo levels, and (4) the decrease in the fluorescence Fm level seemed to be related to denaturation of chlorophyll-proteins. All the data suggested that, as well as the separation of light-harvesting chlorophyll a/t b protein complexes of PS II from the PS II core complexes, partly reversible inactivation of the PS II reaction center at high temperatures is the cause of the increase in the Fo level.

The variance-to-mean ratios of counts accumulated during a time-gate were measured as a function of gate width for several Geiger-Mueller(GM) and neutron proportional counters. The measured ratios asymptotically decreased with an increase in gate width. The ratio for a GM counter was saturated in about 400 μs of gate width, while that for a neutron counter was done in about 40 μs. Applying the first- and second-order formulae derived from the Muller's expression for the variance-to-mean ratio, the dead times of these counters were inferred from these saturated ratios. In the count-rate range above 1,000cps for the GM counter and above 12,000cps for the neutron counter, the dead times obtained by the first-order formula apparently depended on count rate. On the contrary, the application of the second-order formula sufficiently reduced the count-rate dependence. The dead times obtained by the second-order formula were consistent with those by the previous two-source or reactor-power variational methods.

The variance-to-mean measurements were carried out in the ex- and in-core experiments to demonstrate the validity and applicability of the improved expression for data analysis, which was derived by considering the dead-time effect of neutron counter. In the ex-core experiment, the validity of the dead-time term, which was added to the conventional expression for the consideration of the dead-time effect, could be confirmed, and the dead time of the counter employed was also determined. In the in-core (Feynman-α) experiment, it is confirmed that both the inherent decay constant and the dead time could be obtained by the application of the improved expression to data analysis. The above results indicate that the improved expression is available for the data analysis of the Feynman-α experiment performed under high-count-rate conditions.

The Feynman-α (variance-to-mean ratio) formula for a symmetric coupled-core system has been developed to analyse some kinetic parameters of coupled-core systems. Recently, this method has been applied to nuclear criticality safety studies, such as the determination of subcriticality or neutron interference effect between two fissile units. This method is based on neutron pulse counting so that it suffers a counting loss effect originating from a dead time due to the pulse-type neutron detector and counting circuit. To extend the method to more practical uses, the counting loss effect needs to be overcome. We have derived a new formula taking account of dead time effect, making the treatment proposed by Srinivasan our model, and have shown that kinetic parameters of coupled-core systems could be estimated by this new formula.

The method for measuring effective delayed neutron fraction βeff proposed by E.F. Bennett, which is based on measuring a covariance of neutron counts and an absolute fission rate, was applied to thermal neutron systems in Kyoto University Critical Assembly. The successful results were already published in this journal. At that time, an only skeleton of the derivation of theoretical formula shown by E.F. Bennett was introduced, because his derivation was so complicated that the detail description was impossible in the limited space. We found that the formula of the covariance method could be derived easily by using the compound detection probability technique which was the standard technique to derive the formulae of various neutron correlation experiments. As a result, it became clear that the present formula was different by a factor (1-βeff)2 from the original one derived by E.F. Bennett. In this paper, we show the process of derivation based on the compound detection probability technique, and discuss the difference between the original formula and our formula.

The Feynman-α (variance-to-mean ratio) method is a neutron noise analysis based on the statistical characteristics of neutron counts accumulated within counting-gate time (gate width). The kinetic parameters of reactor physics are evaluated from the gate width dependence of these characteristics, so that we need to accumulate many neutron count data for various gate widths. Hence huge measuring time is required to get the kinetic parameters with good accuracy. To save measuring time, we make use of the bunching technique proposed by T. Misawa, in which we accumulate time series data of neutron counts within a fundamental gate width T by using a multi-channel scaler device having dwell time T, and synthesize any data for longer gate widths by bunching these data. When the multi-channel scaler device is used in this bunching technique, count loss time exists between adjacent channels because of channel advance time Δ. Although this channel advance time is generally small, it seems that loss of correlated neutron counts brings about a serious problem. In this report, therefore, the rigorous formula containing the channel advance time was derived for a single core system based on the multi-gate Pal-Bell equation without delayed neutrons, in order to investigate the effect due to the loss of correlated neutron counts. From numerical study for a light water moderated-core, it was concluded that the influence of the loss of correlated counts depended on only the channel advance time-to-fundamental gate width ratio ΔT, and it became prominent as ΔT value increased.

The effective delayed neutron fraction βeff is an important reactor physics parameter, because it plays a role of a conversion factor between the calculated reactivity in Δk/k unit and the measured one in dollar unit. In 1970's, central-sample-worth measurements were done to accumulate the basic data for fast reactor design. Calculated values to these measurements were 30% overestimate. It was pointed out that the 10% of this discrepancy was due to the βeff. Recently, as an origin of systematic discrepancy between the calculated and measured reactivity is due to the βeff, needs for experimental method obtaining the βeff with 1-2% accuracy have been stressed in order to re-examine delayed neutron data and calculational method. In this report, we describe the βeff measurements by using the method proposed by E.F. Bennett at the Kyoto University Critical Assembly (KUCA) of the Kyoto University Research Reactor Institute. This method is based on the measurements of covariance between neutron counts and the absolute fission rate. Measurements were performed with the 3/8″ P36EU thermal neutron system which was composed of 93.3% enriched uranium plates of 1/16″ thickness and 3/8″ polyethylene moderator plates, and the 1/8″ P80EU system which was composed of 1/8″ polyethylene plates and had slightly hard neutron spectrum. As the results of several measurements, the βeff of the 3/8″ P36EU system ranged from 7.60 ±0.18 to 7.96±0.19, and from 8.07±0.18 to 8.14±0.18 for the 1/8″ P80EU system. The latter is slightly large because of hard neutron spectrum. The experimental accuracy is ±2.2%- ±2.9% which did not clear the target accuracy of 1-2%. But this may be improved by means of an improvement of fission rate measurement. Comparing with these measurements and the calculated values based on the JENDL-2 nuclear data file, they agreed within the range form -4% to 1.5%. Then we concluded that the covariance method was usable to evaluate the βeff value of thermal neutron system.

One-pot sequences of hydrogenation/hydroamination to form indoles from (2-nitroaryl)alkynes and hydrogenation/reductive amination to form aniline derivatives from nitroarenes and aldehydes were catalyzed by Au nanoparticles supported on Fe2O3. Nitro group selective hydrogenations and successive reactions were efficiently catalyzed under the conditions.

Applicability and efficiency of Tone’s method used for resonance calculations is improved by incorporating the Method of Characteristics (MOC). Verification calculations are carried out in three configurations, i.e., infinite slab, infinite cylinder, and pin-cell. The validity of the modified Tone’s method has been confirmed through the results of verification calculations. Since MOC has excellent geometric flexibility and efficiency for large and complicated configurations, the proposed method can be applied to a large, complicated, and general geometry such as a whole fuel assembly or a full core configuration.Copyright © 2010 by ASME

One-pot sequences of hydrogenation/hydroamination to form indoles from (2-nitroaryl)alkynes and hydrogenation/reductive amination to form aniline derivatives from nitroarenes and aldehydes were catalyzed by Au nanoparticles supported on Fe(2)O(3). Nitro group selective hydrogenations and successive reactions were efficiently catalyzed under the conditions.

We found two polymorphisms, A or C, at position 63 from the L-myc transcription start site, and 8- or 9-base Gs stretch between positions 82 and 89 or 90, in L-myc 5' UTR, which exhibited a strong linkage disequilibrium as two haplotypes, A-9G and C-8G. We analyzed whether both haplotypes of 5' UTR of the L-myc gene, each of which is approximately 200 nt long, are involved in translational regulation of the L-myc gene. Each haplotype of 5' UTR was inserted between Renilla luciferase and firefly luciferase genes to construct a bicistronic vector which was transcribed as a single mRNA. A translation of the downstream cistron was increased 70-100-fold in cos 7 cells, and 7-10-fold in HeLa S3 cells compared with a control vector without insertion. However, in this bicistronic assay system, both haplotypes of the L-myc 5' UTR showed similar internal ribosome entry site (IRES) activity. When a stable hairpin loop with a palindromic sequence was inserted into a 5'-end of bicistronic mRNA, the hairpin loop decreased only the activity of an upstream luciferase in both cos 7 and HeLa S3 cells, supporting the presence of an IRES. We also inserted 5' UTR of the L-myc gene into the 5'-end of reporter mRNA. C-8G showed approximately 2-fold higher IRES activity than A-9G in both cos 7 and HeLa S3 cells, suggesting that two polymorphisms in the L-myc exon 1 might be involved in regulation of L-myc protein expression.

Winter wheat (Triticum aestivum L. cv Norin No. 61) was grown at 25 degrees C until the third leaves reached about 10 cm in length and then at 15 degrees C, 25 degrees C, or 35 degrees C until full development of the third leaves (about 1 week at 25 degrees C, but 2-3 weeks at 15 degrees C or 35 degrees C). In the leaves developed at 15 degrees C, 25 degrees C, and 35 degrees C, the optimum temperature for CO(2)-saturated photosynthesis was 15 degrees C to 20 degrees C, 25 degrees C to 30 degrees C, and 35 degrees C, respectively. The photosystem II (PS II) electron transport, determined either polarographically with isolated thylakoids or by measuring the modulated chlorophyll a fluorescence in leaves, also showed the maximum rate near the temperature at which the leaves had developed. Maximum rates of CO(2)-saturated photosynthesis and PS II electron transport determined at respective optimum temperatures were the highest in the leaves developed at 25 degrees C and lowest in the leaves developed at 35 degrees C. So were the levels of chlorophyll, photosystem I and PS II, whereas the level of Rubisco decreased with increasing temperature at which the leaves had developed. Kinetic analyses of chlorophyll a fluorescence changes and P700 reduction showed that the temperature dependence of electron transport at the plastoquinone and water-oxidation sites was modulated by the temperature at which the leaves had developed. These results indicate that the major factor that contributes to thermal acclimation of photosynthesis in winter wheat is the plastic response of PS II electron transport to environmental temperature.

Oxygen evolution is one of the most heat-sensitive sites in photosynthetic organisms. To investigate effects of heat stress on photosynthesis, high-temperature (HT) -induced fluorescence Fo (minimum fluorescence) increases and Fm (maximum fluorescence) decreases had been studied by many workers (1). In higher plants, the Fo increase was attributed to irreversible detachment of light-harvesting chlorophyll a/b protein complexes from the reaction center (RC) complexes of Photosystem (PS) II, to partly reversible inactivation of PS 11 (2, 3), and to dark reduction of QA (4). The Fm decrease is related to inhibition of oxygen evolution (5, 6). However, Fm levels in the presence of 3- (3,4-dichlorophenyl) -1,1-dimethylurea and NH2OH, which cancelled the inhibitory effect of heat stress on oxygen evolution, were also decreased by HT treatments, showing that RCs of PS II were inactivated by high temperature-stress and that the inactivated PS II RC complexes become less fluorescent (6). In cyanobacteria, however, little is known about the effects of HTs on photosynthetic systems and on these fluorescence parameters. In this report, we show that the Fo increase in cyanobacteria is due to partly reversible release of phycobilisomes from the RC complexes of PS II and to partly reversible inactivation of PS II RC.

The intermolecular hydroaminomethylation and the intramolecular cyclocarbonylation efficiently proceeded on cobalt oxide supported gold nanoparticles. The intermolecular reaction employing terminal olefins and N-isopropylaniline afforded hydroaminomethylated products as a mixture of regioisomers via a common reaction path consisting of hydroformylation, imine formation, and hydrogenation. In contrast, indolinone derivatives were exclusively obtained in the case of 2-alkenylanilines based on the intramolecular cyclocarbonylation mechanism. Both of these reactions were catalyzed by cobalt species derived from cobalt oxide. The active cobalt species were formed via reduction of the oxide support promoted by deposited gold nanoparticles. Characterization of the catalysts before and after the reaction was also performed.

To investigate the applicability of the Feynman- (or variance-to-mean) and Rossi-α techniques to subcriticality monitoring of the future accelerator-driven subcritical reactor (ADSR), a series of experiments was performed at the Kyoto University Critical Assembly (KUCA). To simulate the pulse mode operation of the ADSR, a D-T pulsed neutron generator was employed. As a result, it was observed that the α-values measured by these techniques clearly depended on the subcriticality, ranging from $0.65 to $2.72. Furthermore, through measurements in transient states that were realised by operating control rods, it was found that one can detect subcriticality changes in quasi-real-time.

For the analysis of noise problems in zero-power coupled-core reactors, one-energy group multipoint Pal-Bell equations are derived and their applications are illustrated. The illustration is made for the neutron correlation experiments of loosely-coupled two-core systems. We first derive a two-point version of the Pal-Bell equations for the neutron detection probability generating functions, and then derive the formulae of Feynman-alpha and Rossi-alpha (Orndoff type) experiments for a coupled-core system, using the factorial moment and cumulant expansions. With these formulae the following coupled-core kinetic parameters can be evaluated from neutron correlation experiments: coupling delay time, coupling coefficient and neutron generation time. The simplicity in the present derivation of Pal-Bell equations is pointed out.

A two-group, one-dimensional formulation of a coupled-core system is proposed as a revision of the one-group response function method by Shinkawa et al. The coupling coefficient of the Kyoto University Critical Assembly symmetric coupled-core loading is revised.

For single-core reflected neutronic systems, generalized neutron generation time is derived and given physical interpretations in terms of importance. A system kinetic equation containing the moderator region response function previously introduced is reduced by a slow-variation approximation to the form of a conventional one-point kinetic equation, in which a parameter can be identified as generalized neutron generation time by analogy with a bare system. In such a mathematical expression for the parameter, one can further identify the amount of increase due to reflection over the bare system generation time. This amount is found to be the reflection time multiplied by the number of migrations that neutrons undergo between reflector and core in one generation. The theoretical generation time of the SHE assembly, a thermal-energy, graphite-moderated critical assembly, calculated by such a formation with cylindrical geometry, agreed well with that from pulsed neutron experiments.

A method is proposed to derive three kinetic parameters of a zero-power coupled-core system, namely coupling reactivity Δ, mean neutron transit time , and neutron generation time Λ of respective co...

One-dimensional, one-energy-group diffusion theory is applied to a coupled-core slab reactor to derive kinetic equations for the system, with different modes of formulation taken for moderator regions and for core regions. For the former, the diffusion equation is exactly solved to obtain the time-dependent neutron currents from moderator to core (the moderator response function) in response to the neutron incident current in the form of a unit impulse on the boundary. For the core regions, the neutron flux psi(x,t) is written as a product of a shape function, phi(x,t), and a time function, P(t), as suggested by Henry, with P(t) chosen to represent the time variation of total importance over the respective core. The boundary terms that arise in the equations for P(t) are combined with incoming neutron currents at the boundaries, which in turn are expressed in terms of the moderator region reponse functions above. The equations for P(t) derived by such procedures include the coupling effect between the two cores, without a need for the conventional, a priori assumption of coupling coefficient. For the Argonaut two-slab core, the transfer functions are obtained and compared with existing values. The value of the conventional coupling coefficient is also inferred bymore » reducing the present form of coupling terms by approximation. From the approximation needed in the procedure, the limitation of the coupling coefficient approach is discussed.« less

In a previous work, we have derived a formula for the variance-to-mean ration, used in the Feynman-alpha method, of the neutron counts in a subcritical system driven by a correlated (multiple or non-Poisson) source (such as a spallation or a 252 Cf one). The formal derivation as made by assuming prompt neutrons only in the fission chain, and the results were extended to include delayed neutrons by intuitive arguments. To confirm this procedure and the validity of the former result, in this paper the variance-to-mean formula has been derived by using a master equation technique including one group of delayed neutrons. The result shows, in agreement with the previous work, that both the prompt and the delayed neutron terms include the effect of the correlated source in form of additive factors, multiplying the corresponding time dependent terms. It is thus also confirmed that the presence of a correlated source with large multiplicity, such as in the case of a spallation source in an accelerator driven system, is very beneficial for the application of the Feynman alpha technique because it enhances the prompt alpha component from which the prompt neutron time constant is determined. Hence, in such systems the reactivity may be monitored with larger subcriticalities than in conventional systems.

Formulae of neutron correlation measurements, such as Feynman-and Rossi-alpha, have been derived in the past by the master equation method or the joint detection probability method. Generally speaking, the master equation method is rigorous in the sense, that all elementary processes can be taken into account, but its manipulations are complicated and elaborate. On the other hand, the method of joint detection probability is heuristic, but several kinds of formulae can be easily derived from it. It seems that these methods are complementary. Recently in order to develop a method for evaluating subcriticality in the accelerator driven subcritical reactors, we derived the Feynman-alpha formula with a correlated neutron source and delayed neutrons based on the master equation method. In this paper, based on a heuristic method, we have derived the joint detection probability including one group of delayed neutrons and a correlated neutron source, which is valid in deep subcritical systems. Then, as an application of this joint probability, the Rossi-alpha formula with delayed neutrons and a correlated neutron source has been derived.