Bayesian Analysis of Econometrics Systems with Discrete Variables and Inequality Constraints

In econometric models, sign or inequality constraints on parameters arise in a wide variety of applications. In this paper, we incorporate linear and nonlinear inequality constraints into systems of equations with both discrete and continuous variables serving as the dependent variables. The posterior sample is generated using Gibbs and Metropolis algorithms with data augmentation. One illustrative example analyzes the choice between fixed and adjustable mortgage rates with inequality restrictions on the financial and borrower characteristics. A second application focuses on certification and performance of auditors.

Dynamical Stability of Witten Rings

The dynamical stability of cosmic rings, or vortons, is investigated for the particular equation of state given by the Witten bosonic model. It is found that there exists a finite range of the state parameter for which the vorton states are actually stable against dynamical perturbations. Inclusion of the electromagnetic self action into the equation of state slightly shrinks the stability region but otherwise yields no qualitative difference. If the Witten bosonic model represents a good approximation for more realistic string models, then the cosmological vorton excess problem can only be solved by assuming either that strings are formed at low energy scales or that some quantum instability may develop at a sufficient rate.Comment: 11 pages, LaTeX-ReVTeX (v.3), 2 figures available upon request, DAMTP R-94/1

Index insurance for managing climate-related agricultural risk: toward a strategic research agenda

In October 2011, the CGIAR program on Climate Change, Agriculture and Food Security (CCAFS) and the Index Insurance Innovation Initiative (I4) organized a joint workshop hosted by the International Food Policy Research Institute (IFPRI). The workshop was designed to identify and address issues surrounding index‐based insurance for smallholder farmers and the rural poor in the developing world. Emphasis was placed on identifying key areas of research and learning for the academic and policy community to pursue. The workshop took as its starting point the idea that there is large potential in using indices to insure smallholder farmers. However, in practice, the costs of providing and scaling up index insurance have not been insubstantial. In view of this potential and these constraints, workshop participants identified key areas of research and learning aimed at increasing the benefits of index‐based insurance to smallholder farmers and the rural poor in the developing world. This report summarizes the findings of the two‐day workshop

Equation of state of cosmic strings with fermionic current-carriers

The relevant characteristic features, including energy per unit length and tension, of a cosmic string carrying massless fermionic currents in the framework of the Witten model in the neutral limit are derived through quantization of the spinor fields along the string. The construction of a Fock space is performed by means of a separation between longitudinal modes and the so-called transverse zero energy solutions of the Dirac equation in the vortex. As a result, quantization leads to a set of naturally defined state parameters which are the number densities of particles and anti-particles trapped in the cosmic string. It is seen that the usual one-parameter formalism for describing the macroscopic dynamics of current-carrying vortices is not sufficient in the case of fermionic carriers.Comment: 30 pages, 15 figures, uses ReVTeX, equation of state corrected, comments and references added. Accepted for publication in Phys. Rev.

Fermionic massive modes along cosmic strings

The influence on cosmic string dynamics of fermionic massive bound states propagating in the vortex, and getting their mass only from coupling to the string forming Higgs field, is studied. Such massive fermionic currents are numerically found to exist for a wide range of model parameters and seen to modify drastically the usual string dynamics coming from the zero mode currents alone. In particular, by means of a quantization procedure, a new equation of state describing cosmic strings with any kind of fermionic current, massive or massless, is derived and found to involve, at least, one state parameter per trapped fermion species. This equation of state exhibits transitions from subsonic to supersonic regimes while the massive modes are filled.Comment: 27 pages, 15 figures, uses ReVTeX. Shortened version, accepted for publication in Phys. Rev.

Sputtering of pure boron using a magnetron without a radio-frequency supply

Boron at room temperature is insulating and therefore conventionally sputtered using radio-frequency power supplies including their power-matching networks. In this contribution, we show that through a suitable ignition assistance, via temporary application of a high voltage (∼600 V) to the substrate holder or auxiliary electrode, the magnetron discharge can be ignited using a conventional mid-frequency power supply without matching network. Once the discharge is ignited, the assisting voltage can be reduced to less than 50 V, and after the boron target surface is at elevated temperature, thereby exhibiting sufficient conductivity, the assisting voltage can be turned off. The deposition of boron and boron nitride films has been demonstrated with a deposition rate of approximately 400 nm/h for a power of 250 W