Plant delta(15)N associated with arbuscular mycorrhization, drought and nitrogen deficiency

It has long been evident that plant (15)N chiefly reflects the processes which fractionate (15)N/(14)N rather than the (15)N of plant N source(s). It has emerged recently that one of the most important fractionating processes contributing to the whole plant (15)N is the presence/absence, type or species of mycorrhiza, especially when interacting with nutrient deficiency. Ecto- and ericoid mycorrhizas are frequently associated with (15)N-depleted foliar (15)N, commonly as low as -12 per thousand. As shown by the present study, plants having no mycorrhiza, or those infected with various species of arbuscular mycorrhiza (AM)-forming fungi, interact with varying concentrations of soil nitrogen [N] and moisture to enrich plant (15)N by as much as 3.5 per thousand. Hence the lack of a mycorrhiza, or variation in the species of AM-forming fungal associations, can account for about 25% of the usually reported variations of foliar (15)N found in field situations and do so by (15)N enrichment rather than depletion. Copyright 1999 John Wiley & Sons, Ltd.     

Structure of rotational bands in 253No

In-beam gamma-ray and conversion electron spectroscopic studies have been performed on the ²⁵³ No nucleus. A strongly coupled rotational band has been identified and the improved statistics allows an assignment of the band structure as built on the $\ensuremath 9/2^-[734]_{\nu}$ ground state. The results agree with previously known transition energies but disagree with the tentative structural assignments made in earlier work.     

Conversion electron cascades in 254(102)No

The spectrum of prompt conversion electrons emitted by excited 254No nuclei has been measured, revealing discrete lines arising from transitions within the ground state band. A striking feature is a broad distribution that peaks near 100 keV and comprises high multiplicity electron cascades, probably originating from M1 transitions within rotational bands built on high K states.     

Prolate deformation in the 187,189Bi isotopes

Prompt and delayed gamma-ray spectroscopy of very neutron-deficient bismuth isotopes ^{187, 189}Bi has been performed using the recoil decay tagging method. A rotational band has been observed in ¹⁸⁹Bi and is interpreted as a complete decoupling of a single proton from the deformed lead core. The results for ¹⁸⁷Bi suggest a similar structure and coupling scheme. This study gives the first evidence for a prolate band in a light bismuth nucleus and confirms the prolate character of the low-lying rotational band observed in the core nuclei ¹⁸⁸Pb and ¹⁸⁶Pb.Received: 21 July 2004, Published online: 21 September 2004PACS: 23.20.Lv transitions and level energies - 27.70. + q K. Hauschild: Present address: CSNSM, Orsay, France.P. Nieminen: Present address: ANU, Canberra, Australia.M. Rejmund: Present address: GANIL, Caen, France.J. Wilson: Present address: LPSC, Grenoble, France.A.N. Andreyev: Present address: TRIUMF, Vancouver, Canada.F. Becker: Present address: GSI, Darmstadt, Germany.M. Muikku: Present address: RNSA, Helsinki, Finland.     

Error growth in the numerical integration of periodic orbits by multistep methods, with application to reversible systems

We study the growth with time of (the coefficients of the asymptoticexpansion of) the error in the numerical integration with linearmultistep methods of periodic solutions of systems of ordinarydifferential equations. Particular attention is devoted to reversiblesystems. It turns out that symmetric linear multistep methodscannot be recommended in spite of the fact that they mimic thereversibility of the true flow. For reversible second-ordersystems, linear multistep methods without parasitic double rootsare useful.