Some finiteness conditions on indecomposable operands

Let S be a monoid such that every left S-operand satisfies the ascending chain condition on orbits. Let X be an indecomposable [0-indecomposable] left S-operand. There is a descending chain of suboperands of X defined in terms of maximal orbits. If this chain terminates after a finite number of terms, the last non-empty [non-zero] term defines a distinguished collection (X) [ ₀(X)] of disjoint [0-disjoint] orbits in X. The assumption that (X) [ ₀(X)] is finite for all appropriate X, together with the additional assumption that every left S-operand satisfies the d.c.c. on orbits, implies that S has a unique minimal left ideal [that the principal left ideals outside of the minimal ideal are linearly ordered]. This research supported in part by the National Science Foundation.     

A new approach to firm evaluation

In this paper, a method is developed to evaluate firms on the basis of the risks they face. In accordance with the multi-factor method, risk is represented as a vector of sensitivities to unexpected changes of risk factors. Subsequently, the sensitivities themselves are related to firm characteristics.In addition, an application of the method to interfirm comparison is presented. This application is illustrated by a numerical example based on estimates concerning real data. Apart from this application, some other possible future applications are mentioned. Finally, some decision support tools are presented which may enhance the usefulness of the method in practice.     

Hydrogen scrambling in the long-lived protonated benzene ion generated from benzyl amine in the i.c.r. spectrometer

It is shown by reactions with various bases in an i.c.r. cell that an almost complete H-D randomization takes place in the gaseous and long-lived [C₆H₂D₅]⁺ ion, generated from C₆D₅CD₂NH₂ by electron impact, but not in its precursor ions. This follows from the ratio of [H]⁺ vs [D]⁺ transfer to bases, obtained from double resonance signals. The ratio appears to be reliable only if the protonated (deuterated) base is stable and does not undergo unimolecular decompositions.     

Unprecedented rearrangements via allenes as π-participants in α-acyliminium ion cyglisations

Upon HCOOH reaction of ethoxylactams $\text{1a}$-$\text{1d}$ the terminally unsubstituted allenes $\text{1a}$ and $\text{1d}$ underwent a [3,3] sigmatropic rearrangement. The dimethyl allenes 1b and 1c afforded only products from an α-acyliminium ion cyclisation.     

Residue-specific 13C' CSA tensor principal components for ubiquitin: correlation between tensor components and hydrogen bonding

The residue-specific 13C' CSA tensor principal components, sigma(11), sigma(22), sigma(33), and the tensor orientation defined by the rotation angles beta and gamma have been determined by solution NMR for uniformly labeled ubiquitin partially aligned in four different media. Spurious chemical shift deviations due to solvent effects were corrected with an offset calculated by linear regression of the residual dipolar couplings and chemical shifts at increasing alignment strengths. Analysis of this effect revealed no obvious correlation to solvent exposure. Data obtained in solution from a protein offer a better sampling of 13C' CSA for different amino acid types in a complex heterogeneous environment, thereby allowing for the evaluation of structural variables that would be challenging to achieve by other methods. The 13C' CSA principal components cluster about the average values previously determined, and experimental correlations observed between sigma(11), sigma(22) tensorial components and C'O...H(N) hydrogen bonding are discussed. The inverse association of sigma(11) and sigma(22) exemplify the calculated and solid-state NMR observed effect on the tensor components by hydrogen bonding. We also show that 13C' CSA tensors are sensitive to hydrogen-bond length but not hydrogen-bond angle. This differentiation was previously unavailable. Similarly, hydrogen bonding to the conjugated NH of the same peptide plane has no detectable effect. Importantly, the observed weak correlations signify the presence of confounding influences such as nearest-neighbor effects, side-chain conformation, electrostatics, and other long-range factors to the 13C' CSA tensor. These analyses hold future potential for exploration provided that more accurate data from a larger number of proteins and alignments become available.     

Selective bond breaking in beta-D-ribose by gas-phase electron attachment around 8 eV

Electron attachment experiments are carried out on the beta-d-ribose molecule in the gas phase for the energy region around 8 eV, and clear fragmentation products are observed for different mass values. A computational analysis of the relevant dynamics is also carried out for the beta-d-ribose in both the furanosic and pyranosic form as gaseous targets around that energy range. The quantum scattering attributes obtained from the calculations reveal in both systems the presence of transient negative ions (TNIs). An analysis of the spatial features of the excess resonant electron, together with the computation and characterization of the target molecular normal modes, suggests possible break-up pathways of the initial, metastable molecular species.     

Tunable hot-electron transfer within a single core-shell nanowire

We report the hot photoexcited electron transfer across the coaxial interface of a cylindrical core-shell nanowire. Modulation of the transfer rates, manifested as a large tunability of the voltage onset of negative differential resistance and of voltage-current phase, is achieved using three different modes. The coupling of electrostatic gating, incident photon energy, and the incident photon intensity to transfer rates is facilitated by the combined influences of geometric confinement and heterojunction shape on hot-electron transfer, and by electron-electron scattering rates that can be altered by varying the incident photon flux, with evidence of weak electron-phonon scattering. Dynamic manipulation of this transfer rate permits the introduction and control of a continuously adjustable phase delay of up to ～130° within a single nanometer-scale device element.