Identification of the Li ground state

The proton-stripping reaction from a ¹¹Be radioactive beam incident on a beryllium target demonstrates that only (7±3)% of the ⁹Li residues in the reaction are in coincidence with the 2.7 MeV γ-ray corresponding to the ⁹Li first excited state. This implies that the previously observed low-energy neutrons from the decay of the unbound nucleus ¹⁰Li represent a direct l=0 transition to the ⁹Li ground state. Consequently, neutron-unbound ¹⁰Li is proven to have the same parity inversion as occurs in the case of ¹¹Be with a  intruder state below the natural parity state.     

A comparative study of the immunogold labeling on H(2)O(2)-treated and heated epoxy sections.

The purpose of this study was to compare the intensity of the immunogold labeling of H(2)O(2)-treated and heated epoxy sections. Renal swine tissue with glomerular immune complex deposits with reactivity against IgG was embedded in epoxy resin. Immunogold labeling with anti-IgG was performed on sections from these blocks. Some of these sections were treated by H(2)O(2), others were heated in a citrate solution, while some were not treated at all. Some epoxy sections, which had been exposed to both H(2)O(2) and heat, were also exposed to the same immunolabeling. The heated epoxy sections obtained an yield of specific immunogold labeling, which was twice as large as the labeling of the H(2)O(2)-treated sections. The yield of immunolabeling of the sections that had been exposed to both H(2)O(2) and heat was not significantly different from the sections that were only exposed to heat. The non-treated sections were very weakly labeled with anti-IgG. We believe that both H(2)O(2) and heat have the ability to break some chemical bonds between the epoxy resin and the antigens, but heating in citrate buffer has a larger potential in this respect than H(2)O(2). We interpret the results from the combined treatment with H(2)O(2) and heat in the following way; the bonds that are broken by H(2)O(2) will also be broken by heating in citrate solution. The practical significance of these results is that heating in citrate buffer is a more convenient method for enhancing the immunolabeling of epoxy sections than treatment with H(2)O(2).     

Decay pathways of small gold clusters

The decay pathway competition between monomer and dimer evaporation of photoexcited cluster ions Au ⁺ _n, n = 2-27, has been investigated by photodissociation of size-selected gold clusters stored in a Penning trap. For n > 6 the two decay pathways are distinguished by their experimental signature in time-resolved measurements of the dissociation. For the smaller clusters, simple fragment spectra were used. As in the case of the other copper-group elements, even-numbered gold cluster ions decay exclusively by monomer evaporation, irrespective of their size. For small odd-size gold clusters, dimer evaporation is a competitive alternative, and the smaller the odd-sized clusters, the more likely they decay by dimer evaporation. In this respect, Au ⁺ ₉ shows an anomalous behavior, as it is less likely to evaporate dimers than its two odd-numbered neighbors, Au ⁺ ₇ and Au ⁺ ₁₁. This nonamer anomaly is typical for copper-group cluster ions M ⁺ ₉ (M = Cu, Ag, Au) and a similar behavior is found in the anionic heptamers M ^- ₇. It is discussed in terms of the well-known electronic shell closing at n _e = 8 atomic valence electrons. Received 2 November 2000     

Strong intramolecular hydrogen bonds and steric effects involving C═S groups: An NMR and computational study

A number of 5-acyl rhodanines and thiorhodanines with bulky acyl groups (pivaloyl and adamantoyl), not previously available, have been synthesized. The compounds are shown to exist in the enol form. Structures have been calculated using both the MP2 approach and the B3LYP-GD3BJ functional and the 6-311++G(d,p) basis set. Hydrogen bond energies are estimated by subtracting energies of a structure with the OH group turned 180° from those of the intramolecularly hydrogen-bonded one. Properties such as OH chemical shifts, two-bond isotope effects on ¹³C chemical shifts, electron densities at the bond critical point from atoms in molecules analysis, and the hydrogen bond energies show that the sterically hindered compounds have stronger hydrogen bonds than methyl or isopropyl derivatives. The combination of oxygen and sulfur derivatives enables a detailed analysis of hydrogen bond energies.     

WYD-like Skew Information Measures

Following recent advances in the theory of operator monotone functions we introduce new classes of WYD-like skew information measures.     

Shock elasticities and impulse responses

We construct shock elasticities that are pricing counterparts to impulse response functions. Recall that impulse response functions measure the importance of next-period shocks for future values of a time series. Shock elasticities measure the contributions to the price and to the expected future cash flow from changes in the exposure to a shock in the next period. They are elasticities because their measurements compute proportionate changes. We show a particularly close link between these objects in environments with Brownian information structures.     

Simplified components of the spin-other-orbit interaction near the middle of the atomic f shell

To honour the memory of Brian Garner Wybourne, an analysis is presented of three components of the spin-other-orbit interaction for f electrons using the kind of Lie groups he would have been familiar with. The components have been named z ₆, z ₈ and z ₁₀. They all belong to the irreducible representation (IR) (30) of Racah’s group G₂. Near the middle of the f shell it is often found that fewer independent blocks of numbers are needed to express their matrix elements than the Wigner–Eckart theorem, generalized to the IRs U of G₂, would indicate. Each block corresponds to a given U and U?′, and possesses rows and columns labelled by the angular momenta L and L′. The number of independent blocks would be expected to be given by Racah’s multiplicity function c(UU?′ (30)); but near the middle of the shell the number c(UU?′ (20)) (or less) often suffices. For this to occur, z ₈ and z ₁₀ have to be replaced by linear combinations corresponding to IRs of the types (20)×(10) and (21)×(10) of the direct product group G_2A×G_2B, where A and B refer to electrons with their spins up (A) and spins down (B). A detailed example is provided by the IR (31) of G₂, which occurs in the configurations f ⁵ through f ⁹. In addition, two antiHermitian operators (z _a6 and z _a7) that also belong to the IR (30) of G₂ are discussed.