On exact mappings between fermionic Ising spin glass and classical spin glass models

We present in this paper exact analytical expressions for the thermodynamical properties and Green functions of a certain family of fermionic Ising spin-glass models with Hubbard interaction, by noticing that their Hamiltonian is a function of the number operator only. The thermodynamical properties are mapped to the classical Ghatak-Sherrington spin-glass model while the the Density of States (DoS) is related to its joint spin-field distribution. We discuss the presence of the pseudogap in the DoS with the help of this mapping.Comment: 6 page

Applications of microprocessors in digital high frequency radio communications

This thesis describes the application of VLSI devices to channel evaluation and communication techniques over ionospheric radio paths. Digital signal processing techniques using microprocessors and charge coupled devices are described in detail. A novel method for observing interference and fading patterns on HF channels is described. Error control coding schemes and digital modulation techniques are combined in a design for an adaptive modem for use over HF radio links. Results of narrow-band interference measurements, error patterns and coding performance are presented

Alcohol and Student Performance: Estimating the Effect of Legal Access

We consider the effect of legal access to alcohol on student achievement. We first estimate the effect using an RD design but argue that this approach is not well suited to the research question in our setting. Our preferred approach instead exploits the longitudinal nature of the data, identifying the effect by measuring the extent to which a student’s performance changes after he gains legal access to alcohol, controlling flexibly for the expected evolution of grades as students make progress towards their degrees. We find that students’ grades fall below their expected levels upon being able to drink legally, but by less than previously documented. We also show that there are effects on women and that the effects are persistent.

Alcohol and Student Performance: Estimating the Effect of Legal Access

We consider the effect of legal access to alcohol, which is known to increase drinking behavior, on academic performance. We first estimate the effect using an RD design but argue that this approach is not well-suited to the research question in our setting. Our preferred approach instead exploits the longitudinal nature of the data, essentially identifying the effect by comparing a student's academic performance before and after turning 21. We find that students' grades fall below their expected levels upon being able to drink legally, but by less than previously documented. We also show that there are effects on women and that the effects are persistent. The main results are robust to the inclusion of individual fixed effects, individual trends, and individual quadratics, in addition to other controls, that account for the expected evolution of performance as students make progress towards their degrees.alcohol, post-secondary education, minimum legal drinking age

The AGN Obscuring Torus -- End of the "Doughnut" Paradigm?

Unified schemes of active galactic nuclei (AGN) require an obscuring dusty torus around the central engine. The compact sizes (only a few pc) determined in recent high-resolution observations require that the obscuring matter be clumpy and located inside the region where the black-hole gravity dominates over the galactic bulge. This location is in line with the scenario depicting the torus as the region of the clumpy wind coming off the accretion disk in which the clouds are dusty and optically thick. We study here the outflow scenario within the framework of hydromagnetic disk winds, incorporating the cloud properties determined from detailed modeling of the IR emission from clumpy tori. We find that torus clouds were likely detected in recent water maser observations of NGC 3079. In the wind scenario, the AGN main dynamic channel for release of accreted mass seems to be switching at low luminosities from torus outflow to radio jets. The torus disappears when the bolometric luminosity decreases below about \E{42} erg/sec because the accretion onto the central black hole can no longer sustain the required cloud outflow rate. This disappearance seems to have been observed in both LINERs and radio galaxies. With further luminosity decrease, suppression of cloud outflow spreads radially inward from the disk's dusty, molecular region into its atomic, ionized zone, resulting in disappearance of the broad emission line region at lower luminosities, yet to be determined.Comment: ApJ Letters, to be publishe

Cavity sideband cooling of a single trapped ion

We report a demonstration and quantitative characterization of one-dimensional cavity cooling of a single trapped 88Sr+ ion in the resolved sideband regime. We measure the spectrum of cavity transitions, the rates of cavity heating and cooling, and the steady-state cooling limit. The cavity cooling dynamics and cooling limit of 22.5(3) motional quanta, limited by the moderate coupling between the ion and the cavity, are consistent with a simple model [Phys. Rev. A 64, 033405] without any free parameters, validating the rate equation model for cavity cooling.Comment: 5 pages, 4 figure

An Analysis of Product Life Cycle Orientation in PLM Software Tool Vendors

A challenge in implementation of Product Lifecycle Management (PLM) tools is the selection of the right vendor and the solution. Implementing PLM entails huge financial investment on the part of the user and hence precise knowledge as to where each tool can be applied is a must. In this paper, seven PLM tool vendors are compared on their definitions of PLM and also their product offerings in different Product Life Cycle (PLC) phases, including the extreme ends of PLC viz. R&D and end-of-life phase, which are usually ignored. An integrated PLC model is developed and the tools are then mapped onto different phases of PLC. Vendors are compared based on number of tools offered in different PLC phases. The results reveal an uneven distribution in the applicability of various tools, with majority of them focusing on the product development phase and an astonishingly low number on the R&D and end-of-life phases