NP Systems Research Articles

Non-relativistic quark cluster model of the isospin-violating two-nucleon interaction

The violations of isospin symmetry induced in the two-nucleon system at the quark level by the mass difference between up and down quarks are studied in a quark cluster model. Quark dynamics are treated by means of the standard non-relativistic quark model with a quark hamiltonian consisting of a confining harmonic potential, eventually corrected for anharmonicities, and a spin-dependent potential truncated to the contact-gluon-exchange hyperfine interaction. The resonating group method is adopted to treat the six-quark system and we restrict ourselves to configurations of two three-quark clusters with nucléon quantum numbers. π- and σ-meson-mediated quark interactions are tentatively considered in an attempt to achieve a good matching to the empirical strong NN potentials. We supply explicit formulas for the various kernels. Equivalent adiabatic potentials are calculated for the pp, np and nn systems in low partial waves. We also solve the resonating group scattering equations for these systems and give predictions for phase observables and low-energy parameters.

Angular momentum and binding energy effects in two-nucleon transfer

Results of large-basis shell-model calculations of two-nucleon transfer overlaps are presented for non-zero angular momentum and for nn, np and pp systems such as 42Ca, 42Sc, 42Ti which have very different binding energies. It is shown that the usual well-depth method underestimates the two-nucleon transfer overlaps for tightly bound systems but overestimates these overlaps for the weakly bound systems. The differential cross sections can also be distorted by the welldepth method in some particular cases.

The frequency in Japanese of genetic variants of 22 proteins

This paper presents the results of a survey of Japanese for electrophoretic variants of CA I, CA II, LDH, MDH, TPI, NP, HB A and A2, the number of determinations per system ranging from 738 to 4029. Four similar variants of CA I (designed CA IHIR1), one of LDH (designated LDHNGS1), one of MDH (designated MDHS 7HIR1), two of HB A (one a reascertainment of HB Hijiyama, the other not characterized), and one characterized by the absence of HB A2 (delta-thalassaemia) were observed and are described. The CA IHIR1, LDHNAG1 and MDHS 2HIR1 variants have not been previously observed in Japan. No electrophoretic variants were found in the TPI and NP systems.

The time Course of Pacemaker Inhibition in the Hydroid Tubularia

ABSTRACT Stimulating the DOS, a conducting system in Tubularia, inhibits spontaneous firing of the principal pacemaker systems of the polyp, the NP and HP systems. The overall inhibition is greater the greater the stimulus frequency and there is rebound from inhibition at the end of the stimulation period. The latent period for NP inhibition is 0·4–0·6 sec and the duration of inhibition is 4–5 sec. The time course and extent of NP inhibition is independent of stimulus frequency except at high frequency where there is diminishing effectiveness of inhibition with time. HP inhibition has a similarly long latent period and even longer duration, lasting 15–20 sec. HP inhibition from successive stimuli can sum to produce a more intense effect. The behavioural significance of the inhibition seems to be to reduce spontaneous polyp movements during food capture and ingestion.

Multiple Pacemakers and the Behaviour of the HydroidTubularia

ABSTRACTThe spontaneous behaviour of the hydroid Tubularia results from the activity of a number of pacemaker systems in the polyp, there being a major pacemaker system in the distal stalk (the NP system), another in the hydranth body (the HP system) and individual pacemakers in each of the tentacles. The NP system produces single electrical pulses and bursts of three or more pulses, the HP system itself produces single pulses and short bursts of 2-4 pulses, and the tentacle pacemakers fire irregularly. The HP and NP systems are mutually interactive. When the NP system fires in a burst it usually drives the HP system to fire concurrently. Single firing by the NP system sometimes triggers the HP system to fire, and single HP firing can trigger the NP system. Single HP firing is most likely to trigger the NP system if it comes long after the last NP firing, i.e. late in the NP spontaneous cycle. When the HP system independently fires a burst or is driven by the NP system to fire a burst, it drives pacemaker systems in the proximal tentacles to fire concurrently. Firing of the HP system is associated with a behavioural response termed a concert. During a concert the proximal and sometimes the distal tentacles are synchronously elevated. During the longer NP-HP bursts the neck contracts. A peristaltic wave sweeps down the proboscis following the tentacle elevation. Concerts without neck contraction result in mixing of fluid in the enteron chamber of the proboscis ; concerts with neck contraction result in tidal exchange of fluid between the neck chamber and the proboscis chamber. Stimulation of the conducting system in the stalk termed the triggering system (TS) can trigger the NP system to fire. A stalk stimulus is most likely to trigger the NP system if it comes within a few seconds of NP firing, i.e. early in the NP spontaneous cycle. Firing of the NP system of one polyp in a colony can trigger the NP systems of connected polyps. Interpolyp triggering is probably mediated through the TS conducting system. The coupling between NP systems of connected polyps results in synchronization of NP bursts throughout a colony. Because of the coupling between NP and HP systems within single polyps the longer HP bursts, which are those occurring when the HP system is driven by the NP system, are also usually synchronous in connected polyps. This results in concerts with neck contraction being nearly synchronous throughout a colony. Such synchronization facilitates transfer of fluid between the two enteron chambers of polyps during concerts. Prolonged, low-frequency stalk stimulation inhibits spontaneous activity of a polyp, the inhibition increasing with increasing stimulus frequency. The large size of the spontaneous electrical pulses suggests that they are not the result of nervous activity, but possibly due to activity of more primitive co-ordinating mechanisms.

THE COORDINATION OF POTENTIAL PACEMAKERS IN THE HYDROID TUBULARIA.

Sectioning experiments and electrical recording indicate that there are many potential pacemakers in polyps of the hydroid Tubularia. Functionally the pacemakers are organized primarily into pacemaker systems, groups within which there is tight coupling. The different pacemaker systems of a polyp are loosely coupled to one another. There are two principal systems in Tubularia, one in the polyp neck (the NP system) and one in the hydranth (the HP system). In addition, there are pacemakers controlling activities of individual tentacles. Activity in the NP system is usually not associated with observable polyp behavior. HP system activity is correlated with behavioral responses termed concerts. Concerts are probably digestive activities; they result in the mixing of food being digested and the distribution of the products of this digestion. The NP systems of polyps on a colony are loosely coupled to one another through one of the three conducting systems found in Tubularia stalks. The loose coupling between NP systems of polyps on a colony and the loose coupling between NP and HP systems within single polyps results in there being some coordination of concert activity throughout a colony.

Charge dependent effects on scattering lengths of np and pp systems

The effects of the electromagnetic structure of a nucleon on the singlet scattering lengths a np, a pp of np and pp systems are calculated. They are found to be much too small to remove the discrepancy between a np and a pp. It is shown to be plausible that the discrepancy between a np and a pp may be due to π±− π 0 mass difference when its kinematic and dynamical effects, as defined in the text, are taken into account.

On the charge independence of nuclear forces

The possibility that the discrepancy between the zero energy scattering lengths A NP, A PP for 1S states of the NP and PP systems may be due to the mass difference between charged and neutral pions is investigated.