Nuclear reactions of C on a liquid hydrogen target measured with the superconducting TOF spectrometer

Reaction cross sections with various kinds of breakup channels for neutron-rich carbon isotopes ^18-20C and for ⁹Be impinging on a liquid hydrogen target were investigated at 40 MeV/nucleon. The nuclides of interest were produced via projectile fragmentation from a 63 MeV/nucleon ⁴⁰Ar beam and were separated in flight at the RIKEN projectile fragment separator (RIPS). The combination of the large-acceptance superconducting TOF spectrometer, TOMBEE (TOF Mass analyzer for exotic BEam Experiment), with a liquid hydrogen target, CRYPTA (CRYogenic ProTon and Alpha target system), enables simultaneous measurements of several reaction channels: the reaction cross sections (σR), individual elemental fragmentation cross sections (σΔZ), charge-changing cross sections (σcc), neutron-removal cross sections (σ−xn), and charge-pickup cross sections (σΔZ+1) for ^19,20C; σΔZ, σ−xn, and σΔZ+1 for ¹⁸C; and σR for ⁹Be. The present σR of ⁹Be on proton, σR=397±23 mb, measured in the inverse kinematics, was consistent with the previous measurements using proton beams at different laboratories. The σR of ¹⁹C and ²⁰C on proton were determined to be σR=754±22 mb and σR=791±34 mb, respectively. Taking into account the beam energy and target dependence of σR, the present σR are found to be considerably enhanced compared with those measured at around 1 GeV/nucleon. The σΔZ+1 appears to increase with the mass number of the projectiles, and it significantly contributes to σR in the present energy range. The finite-range optical-limit and few-body Glauber model analyses were performed for σR to study the nuclear matter density distributions and to derive the relative strength of the s-wave components of the valence neutrons in ¹⁹C and ²⁰C. A neutron halo structure of ¹⁹C is confirmed with an s-wave dominance of the valence neutron when the effect of the charge-pickup reaction is taken into account. The large σ−n of ¹⁹C and σ−2n of ²⁰C also support the decoupled structures of ¹⁸C +n and ¹⁸C+2n, respectively. The σcc of ¹⁹C and ²⁰C agree with each other within their experimental uncertainties, which might indicate a similar proton density distribution in ¹⁹C and ²⁰C. The σΔZ decreases monotonically without the even-odd effect as the number of removed protons increases.     

Regulation of phosphorylase kinase by low concentrations of Ca ions upon muscle contraction: the connection between metabolism and muscle contraction and the connection between muscle physiology and Ca-dependent signal transduction

It had long been one of the crucial questions in muscle physiology how glycogenolysis is regulated in connection with muscle contraction, when we found the answer to this question in the last half of the 1960s. By that time, the two principal currents of muscle physiology, namely, the metabolic flow starting from glycogen and the mechanisms of muscle contraction, had already been clarified at the molecular level thanks to our senior researchers. Thus, the final question we had to answer was how to connect these two currents. We found that low concentrations of Ca ions (10(-7)-10(-4) M) released from the sarcoplasmic reticulum for the regulation of muscle contraction simultaneously reversibly activate phosphorylase kinase, the enzyme regulating glycogenolysis. Moreover, we found that adenosine 3',5'-monophosphate (cyclic AMP), which is already known to activate muscle phosphorylase kinase, is not effective in the absence of such concentrations of Ca ions. Thus, cyclic AMP is not effective by itself alone and only modifies the activation process in the presence of Ca ions (at that time, cyclic AMP-dependent protein kinase had not yet been identified). After a while, it turned out that our works have not only provided the solution to the above problem on muscle physiology, but have also been considered as the first report of Ca-dependent protein phosphorylation, which is one of the central problems in current cell biology. Phosphorylase kinase is the first protein kinase to phosphorylate a protein resulting in the change in the function of the phosphorylated protein, as shown by Krebs and Fischer. Our works further showed that this protein kinase is regulated in a Ca-dependent manner. Accordingly, our works introduced the concept of low concentrations of Ca ions, which were first identified as the regulatory substance of muscle contraction, to the vast field of Ca biology including signal transduction.     

Discovery of the First 2- State in 16C via Neutron Knockout Reaction

The ¹⁶C nucleus has been investigated by the neutron knockout reaction of ¹⁷C on a liquid hydrogen target. Applying the invariant mass method in inverse kinematics and γ-ray spectroscopy, the energy spectrum was reconstructed by triple-coincidence measurement, in which neutrons, charged fragments, and γ rays from the decay of the reaction residue (¹⁶C*) were detected. A peak at 0.47 MeV was observed in the invariant mass spectrum in coincidence with a peak at 0.74 MeV in the γ-ray spectrum, which indicates the presence of an unbound state with an excitation energy of 5.46 MeV. Comparison of the experimental cross section with the value derived by a theoretical calculation provided evidence that the spin-parity of this state is 2^?.     

Recoil proton tagged knockout reaction for He

We report for the first time the discrimination of the core fragment knockout and valence nucleon knockout reaction mechanisms at medium energy range, by the use of the recoil proton tagging technique. Intense ⁸He beams at 82.3 MeV/u were supplied by the RIPS beam line at RIKEN, and impinged on both hydrogen and carbon targets. Recoil protons were detected in coincidence with the forward moving core fragments and neutrons. The core fragment knockout mechanism is identified through the polar angle correlation and checked by various kinematics relations. This mechanism may be used to extract the cluster structure information of unstable nuclei. On the other hand, with the selection of the tagged valence nucleon knockout mechanism, a narrower peak of ⁷He ground state is obtained. The extracted neutron spectroscopic factor Sn=0.512(18) is relatively smaller than the no-tagged one, and is in good agreement with the prediction of ab initio Green?s function Monte Carlo calculations.     

Effects of 230 MeV Au irradiation on Bi2Sr2CaCu2Ox

Bi₂Sr₂CaCu₂O_x tapes were irradiated using 230 MeV Au¹⁴⁺ ions. Columnar defects were presumably produced due to irradiation. Zero-field-cooling (ZFC) magnetization increased up to a fluence of 1.6 × 10¹¹ Au⁺/cm², but field-cooling (FC) magnetization decreased, indicating the strong pinning effects resulting from the columnar defects. The critical current density as well as the irreversibility field, obtained from the hysteresis loops, were enhanced. Irreversibility fields are fitted by H_irr = A exp(−T/T_A). An effective activation energy for flux motion was obtained from the measurements of magnetization relaxation. The features of flux pinning as a result of the columnar defects were compared with those of point defects brought about by 120 MeV O⁷⁺ irradiation.     

An energy-decomposition technique for the analysis of band structure and its application to polyphosphazene and its halogenated derivatives

An energy-decomposition technique is presented for the analysis of band structures of polymers and is applied to the π orbitals of polyphosphazene and its halogenated derivatives. In this treatment the orbital energy is decomposed into the contributions from individual atoms and bonds in the structure. Thereby, the shape of the energy band is elucidated as a function of atomic orbital interactions as well as structures of polymers. The trends of the k dependences for the individual contributions thus analyzed are consistent with those to be expected from the characters of the crystal orbitais. This method seems to be suitable for determining the effects of various substituents on the shape of the energy bands of polymers.     

2-[2-(5-Bromopyridyl)azo]-5-dimethylaminophenol; a new sensitive reagent for cadmium

Cadmium(II) reacts with 2-[2-(5-bromopyridyl)azo]-5-dimethyl-aminophenol (5-Br-DMPAP) in aqueous solution; the complex can be extracted with organic solvents such as chloroform, 3-methyl-l-butanol and methyl isobutyl ketone at pH 8–10.5 to give a red solution which absorbs at 525–555 nm. The absorbance in organic solvents is stable and the system conforms to Beer's law; the optimal range in 3-methyl-1-butanol for measurement in 1.00-cm cells is 0.01–l p.p.m. cadmium. Moderate amounts of many cations and anions do not interfere, and interfering cations such as zinc, copper, manganese and nickel can be separated by extraction with dithizone. The 5-Br-DMPAP method is one of the most sensitive procedures available for the determination of cadmium; the molar absorptivity in a 3-methyl-1-butanol extract is 1.41·10⁵ 1 mol^?1 cm^?1 at 555 nm.     

1-[(5-Chloro-2-Pyridyl)Azo]-2-Naphthol as a new extraction- photometric reagent for metals

The heterocyclic azo compound, 1-[(5-chloro-2-pyridyl)azo]-2-naphthol (5-Cl-β-PAN), forms various coloured metal chelates, which can be extracted with different organic solvents. Chelate stability is greatly affected by pH. The molar absorptivities are usually considerably greater than those of the β-PAN chelate. Although the bathochromic shifts produced on chelation are no greater than those with 5-Br-β-PAN, the selectivity is increased. The reactivity of tri- and tetravalent metal ions is decreased appreciably by introduction of the chlorine. A correct choice of pH, solvent and masking reagent allows 5-C1-β-PAN to be made reasonably selective.