A CAMEL rating's shelf life

How quickly do the CAMEL ratings regulators assign to banks during on-site examinations become "stale"? One measure of the information content of CAMEL ratings is their ability to discriminate between banks that will fail and those that will survive. To assess the accuracy of CAMEL ratings in predicting failure, Rebel Cole and Jeffery Gunther use as a benchmark an offsite monitoring system based on publicly available accounting data. Their findings suggest that, if a bank has not been examined for more than two quarters, off-site monitoring systems usually provide a more accurate indication of survivability than its CAMEL rating. The lower predictive accuracy for CAMEL ratings “older” than two quarters causes the overall accuracy of CAMEL ratings to fall substantially below that of off-site monitoring systems. The higher predictive accuracy of off-site systems derives from both their timeliness—an updated off-site rating is available for every bank in every quarter—and the accuracy of the financial data on which they are based. Cole and Gunther conclude that off-site monitoring systems should continue to play a prominent role in the supervisory process, as a complement to on-site examinations.bank; bank failure; CAMEL; CAMEL rating; commercial bank; offsite supervision

Dissipative dynamics of an extended magnetic nanostructure: Spin necklace in a metallic environment

We study theoretically the dynamics of an ``xxz'' spin necklace coupled to a conduction electron sea, a model system for a nanostructure in a dissipative environment. We extract the long-time behavior via a mapping to a multichannel Coulomb gas problem followed by a scaling analysis. The strong quantum fluctuations of the necklace cause a nontrivial dependence of couplings on system size which we extract via an analysis involving the ``boundary condition changing operator'', and confirm via a detailed numerical evaluation of one case.Comment: 4 pages, 4 figure

Spin relaxation in Mn12-acetate

We present a comprehensive derivation of the magnetization relaxation in a Mn12-acetate crystal based on thermally assisted spin tunneling induced by quartic anisotropy and weak transverse magnetic fields. The overall relaxation rate as function of the magnetic field is calculated and shown to agree well with data including all resonance peaks. The Lorentzian shape of the resonances is also in good agreement with recent data. A generalized master equation including resonances is derived and solved exactly. It is shown that many transition paths with comparable weight exist that contribute to the relaxation process. Previously unknown spin-phonon coupling constants are calculated explicitly.Comment: 4 pages,4 EPS figures,LaTeX(europhys.sty);final version accepted for EP

Nonadiabatic Landau Zener tunneling in Fe_8 molecular nanomagnets

The Landau Zener method allows to measure very small tunnel splittings \Delta in molecular clusters Fe_8. The observed oscillations of \Delta as a function of the magnetic field applied along the hard anisotropy axis are explained in terms of topological quantum interference of two tunnel paths of opposite windings. Studies of the temperature dependence of the Landau Zener transition rate P gives access to the topological quantum interference between exited spin levels. The influence of nuclear spins is demonstrated by comparing P of the standard Fe_8 sample with two isotopically substituted samples. The need of a generalized Landau Zener transition rate theory is shown.Comment: 5 pages, 6 figure

A CAMEL rating's shelf life

How quickly do the CAMEL ratings regulators assign to banks during on-site examinations become "stale"? One measure of the information content of CAMEL ratings is their ability to discriminate between banks that will fail and those that will survive. To assess the accuracy of CAMEL ratings in predicting failure, Rebel Cole and Jeffery Gunther use as a benchmark an offsite monitoring system based on publicly available accounting data. Their findings suggest that, if a bank has not been examined for more than two quarters, off-site monitoring systems usually provide a more accurate indication of survivability than its CAMEL rating. The lower predictive accuracy for CAMEL ratings “older” than two quarters causes the overall accuracy of CAMEL ratings to fall substantially below that of off-site monitoring systems. The higher predictive accuracy of off-site systems derives from both their timeliness—an updated off-site rating is available for every bank in every quarter—and the accuracy of the financial data on which they are based. Cole and Gunther conclude that off-site monitoring systems should continue to play a prominent role in the supervisory process, as a complement to on-site examinations

Anisotropic Inflation and the Origin of Four Large Dimensions

In the context of (4+d)-dimensional general relativity, we propose an inflationary scenario wherein 3 spatial dimensions grow large, while d extra dimensions remain small. Our model requires that a self-interacting d-form acquire a vacuum expectation value along the extra dimensions. This causes 3 spatial dimensions to inflate, whilst keeping the size of the extra dimensions nearly constant. We do not require an additional stabilization mechanism for the radion, as stable solutions exist for flat, and for negatively curved compact extra dimensions. From a four-dimensional perspective, the radion does not couple to the inflaton; and, the small amplitude of the CMB temperature anisotropies arises from an exponential suppression of fluctuations, due to the higher-dimensional origin of the inflaton. The mechanism triggering the end of inflation is responsible, both, for heating the universe, and for avoiding violations of the equivalence principle due to coupling between the radion and matter.Comment: 24 pages, 2 figures; uses RevTeX4. v2: Minor changes and added references. v3: Improved discussion of slow-rol

Macroscopic Quantum Phase Interference in Antiferromagnetic Particles

The tunnel splitting in biaxial antiferromagnetic particles is studied with a magnetic field applied along the hard anisotropy axis. We observe the oscillation of tunnel splitting as a function of the magnetic field due to the quantum phase interference of two tunneling paths of opposite windings. The oscillation is similar to the recent experimental result with Fe}$_8$\textrm{\ molecular clusters.}Comment: 8 pages, 2 postscript figures, to appear in J. Phys.: Condes. Matte

Magnetic quantum coherence effect in Ni4 molecular transistors

We consider the electron transport in single molecule magnet transistors in the presence of Zeeman spin splitting and magnetic quantum coherence (MQC). The Zeeman interaction is extended along the leads, thereby producing gaps in the energy spectrum which allow electron transport with spin polarized along a certain direction. The MQC induces an effective coupling between localized spin states and continuum spin states in the single molecule magnet and leads, respectively. We investigate the conductance at zero temperature as a function of the applied bias and magnetic field, and show that the MQC is responsible for the appearence of resonances. Accordingly, we name them MQC resonances.Comment: 5 pages, Revtex

Low-Temperature Quantum Relaxation in a System of Magnetic Nanomolecules

We argue that to explain recent resonant tunneling experiments on crystals of Mn$_{12}$ and Fe$_8$, particularly in the low-T limit, one must invoke dynamic nuclear spin and dipolar interactions. We show the low-$T$, short-time relaxation will then have a $\sqrt{t/\tau}$ form, where $\tau$ depends on the nuclear $T_2$, on the tunneling matrix element $\Delta_{10}$ between the two lowest levels, and on the initial distribution of internal fields in the sample, which depends very strongly on sample shape. The results are directly applicable to the $Fe_8$ system. We also give some results for the long-time relaxation.Comment: 4 pages, 3 PostScript figures, LaTe

Synthesis and investigation of the spectral-luminescence characteristics of powder based on zinc oxide

ZnO and ZnAlO composites were synthesized by thermal decomposition of a precursor salt, dried at 200 °C and annealed at 400 and 600 °C, respectively. It was shown that pH and temperature of synthesis has great influence on the spectral-luminescence properties of samples