Ex Situ Conservation of Phyllanthus fraternus Webster and Evaluation of Genetic Fidelity in Regenerates Using DNA-Based Molecular Marker

Germplasm storage of Phyllanthus fraternus by using synseed technology has been optimized. Synseeds were prepared from nodal segments taken from in vitro-grown plantlets. An encapsulation matrix of 3 % sodium alginate and 100 mM calcium chloride with polymerization duration up to 15 min was found most suitable for synseed formation. Maximum plantlet conversion (92.5?±?2.5 %) was obtained on a growth regulator-free ½-strength solid Murashige and Skoog (MS) medium. Multiple shoot proliferation was optimum on a ½ MS medium containing 0.5 mg/l 6-benzylaminopurine (BAP). Shoots were subjected to rooting on MS media containing 1 mg/l α-naphthaleneacetic acid (NAA) and acclimatized successfully. Encapsulated nodal segments can be stored for up to 90 days with a survival frequency of 47.33 %. The clonal fidelity of synseed-derived plantlets was also assessed and compared with that of the mother plant using rapid amplified polymorphic DNA and inter-simple sequence repeat analysis. No changes in molecular profiles were observed among the synseed-derived plantlets and mother plant, which confirms the genetic stability of regenerates. This synseed production protocol could be useful for in vitro multiplication, short-term storage, and exchange of germplasm of this important antiviral and hepatoprotective plant.     

A search for spectator isobars in deuteron collisions

A search has been made for spectator delta resonances from the breakup of deuterons by a 4 GeV/c incident π⁺ beam. It is shown that the narrow pπ enhancement produced backwards in the laboratory system is mostly not Δ, and an upper limit of 0.8% is estimated for the Δ Δ component of the deuteron.     

Pressure induced collapse of the 4f‐electron induced μ+‐Knight shift in Sm0.9La0.1S

The pressure dependence of the μ⁺-Knight shift in the pseudo‐binary compound Sm_0.9La_0.1S has been studied with the aim to verify microscopically the quenching of paramagnetism by the formation and condensation of excitons in the insulating regime. A collapse of the μ⁺-Knight shift is indeed observed but it is not restricted to the insulating phase and may not reflect the bulk‐magnetic response. This revised version was published online in July 2006 with corrections to the Cover Date.     

On the number of lattice points between two enlarged and randomly shifted,copies of an oval

Summary Let A be an oval with a nice boundary in ²,R a large positive number,c>0 some fixed number and a uniformly distributed random vector in the unit square [0,1]². We are interested in the number of lattice points in the shifted annular region consisting of the difference of the sets {(R+c/R)A–} and {(R–c/R)A–}. We prove that whenR tends to infinity, the expectation and the variance of this random variable tend to 4c times the area of the set A, i.e. to the area of the domain where we are counting the number of lattice points. This is consistent with computer studies in the case of a circle or an ellipse which indicate that the distribution of this random variable tends to the Poisson law. We also make some comments about possible generalizations.     

Chemical reactions of positronium studied by age-momentum correlation (AMOC) using a relativistic positron beam

Correlated measurements of the individual positron lifetimes (so-called positron ages) and of the Doppler shift of the 2-annihilation photon energy (Age-Momentum Correlation, AMOC) allow the evolution of the positron states to be observed in the time domain. The AMOC technique is thus especially useful when chemical reactions of positronium induce transitions between positron states. The full information contained in the AMOC data may be extracted from the two-dimensional AMOC histogramme, the so-called AMOC relief, by fitting a suitable two-dimensional model function. In this way quantitative information on the spin conversion of positronium by a paramagnetic radical in the systems HTEMPO/methanol and HTEMPO/benzene and on the formation of positron bound states in aqueous solutions of various sodium halides has been deduced.     

Determination of long-lived radionuclides in environmental media around a nuclear fuel reprocessing plant

Methods for the analysis of¹²⁹I and²⁴¹Pu are described briefly. Neutron activation is necessary to achieve an adequate degree of sensitivity for the measurement of¹²⁹I, but otherwise all laboratory manipulations are straightforward and use commonly-found, well-tried techniques. With these methods, both radionuclides can be measured easily in the terrestrial environment around a nuclear fuel reprocessing plant;²⁴¹Pu is measureable elsewhere in integrating media such as undisturbed soil.     

Solvent polarization and kinetic isotope effects in nitroethane deprotonation and implications to the nitroalkane oxidase reaction

We have carried out a mixed molecular dynamics and centroid path integral simulation using a combined quantum mechanical and molecular mechanical (QM/MM) potential to study the anomalous Br?nsted relationship between rates and equilibria for deprotonation of nitroalkanes in water, which is known as the nitroalkane anomaly. The deprotonation process is catalyzed by nitroalkane oxidase. Our results show that the difference in solvent polarization effects for the TS and products is a major factor for the differential solvent effects on rate and equilibrium of nitroalkane deprotonation. This is due to poor charge delocalization as a result of slow rehybridization compared to bond breaking. Although solvent effects do not affect significantly the computed kinetic isotope effects in comparison with the gas-phase value, there is slight solvent-induced increase in tunneling. The present results suggest that an effective means by which the transition state can be stabilized in the enzyme nitroalkane oxidase is to facilitate the Calpha rehybridization.