The Stability of Macroeconomic Systems with Bayesian Learners

We study abstract macroeconomic systems in which expectations play an important role. Consistent with the recent literature on recursive learning and expectations, we replace the agents in the economy with econometricians. Unlike the recursive learning literature, however, the econometricians in the analysis here are Bayesian learners. We are interested in the extent to which expectational stability remains the key concept in the Bayesian environment. We isolate conditions under which versions of expectational stability conditions govern the stability of these systems just as in the standard case of recursive learning. We conclude that Bayesian learning schemes, while they are more sophisticated, do not alter the essential expectational stability findings in the literature.Expectational stability, recursive learning, learnability of rational expectations equilibrium.

Adaptive Multicast of Multi-Layered Video: Rate-Based and Credit-Based Approaches

Network architectures that can efficiently transport high quality, multicast video are rapidly becoming a basic requirement of emerging multimedia applications. The main problem complicating multicast video transport is variation in network bandwidth constraints. An attractive solution to this problem is to use an adaptive, multi-layered video encoding mechanism. In this paper, we consider two such mechanisms for the support of video multicast; one is a rate-based mechanism that relies on explicit rate congestion feedback from the network, and the other is a credit-based mechanism that relies on hop-by-hop congestion feedback. The responsiveness, bandwidth utilization, scalability and fairness of the two mechanisms are evaluated through simulations. Results suggest that while the two mechanisms exhibit performance trade-offs, both are capable of providing a high quality video service in the presence of varying bandwidth constraints.Comment: 11 page

The Puzzling Frequencies of CEMP and NEMP Stars

We present the results of binary population simulations of carbon- and nitrogen-enhanced metal-poor (CEMP and NEMP) stars. We show that the observed paucity of very nitrogen-rich stars puts strong constraints on possible modifications of the initial mass function at low metallicity.Comment: 3 pages, contribution to "The Origin of the Elements Heavier than Iron" in honor of the 70th birthday of Roberto Gallino, Torino, Italy, September 200

Uniformity in association schemes and coherent configurations: cometric Q-antipodal schemes and linked systems

Inspired by some intriguing examples, we study uniform association schemes and uniform coherent configurations, including cometric Q-antipodal association schemes. After a review of imprimitivity, we show that an imprimitive association scheme is uniform if and only if it is dismantlable, and we cast these schemes in the broader context of certain --- uniform --- coherent configurations. We also give a third characterization of uniform schemes in terms of the Krein parameters, and derive information on the primitive idempotents of such a scheme. In the second half of the paper, we apply these results to cometric association schemes. We show that each such scheme is uniform if and only if it is Q-antipodal, and derive results on the parameters of the subschemes and dismantled schemes of cometric Q-antipodal schemes. We revisit the correspondence between uniform indecomposable three-class schemes and linked systems of symmetric designs, and show that these are cometric Q-antipodal. We obtain a characterization of cometric Q-antipodal four-class schemes in terms of only a few parameters, and show that any strongly regular graph with a ("non-exceptional") strongly regular decomposition gives rise to such a scheme. Hemisystems in generalized quadrangles provide interesting examples of such decompositions. We finish with a short discussion of five-class schemes as well as a list of all feasible parameter sets for cometric Q-antipodal four-class schemes with at most six fibres and fibre size at most 2000, and describe the known examples. Most of these examples are related to groups, codes, and geometries.Comment: 42 pages, 1 figure, 1 table. Published version, minor revisions, April 201

Evolution and CNO yields of Z=10^-5 stars and possible effects on CEMP production

Our main goals are to get a deeper insight into the evolution and final fates of intermediate-mass, extremely metal-poor (EMP) stars. We also aim to investigate their C, N, and O yields. Using the Monash University Stellar Evolution code we computed and analysed the evolution of stars of metallicity Z = 10^-5 and masses between 4 and 9 M_sun, from their main sequence until the late thermally pulsing (super) asymptotic giant branch, TP-(S)AGB phase. Our model stars experience a strong C, N, and O envelope enrichment either due to the second dredge-up, the dredge-out phenomenon, or the third dredge-up early during the TP-(S)AGB phase. Their late evolution is therefore similar to that of higher metallicity objects. When using a standard prescription for the mass loss rates during the TP-(S)AGB phase, the computed stars lose most of their envelopes before their cores reach the Chandrasekhar mass, so our standard models do not predict the occurrence of SNI1/2 for Z = 10^-5 stars. However, we find that the reduction of only one order of magnitude in the mass-loss rates, which are particularly uncertain at this metallicity, would prevent the complete ejection of the envelope, allowing the stars to either explode as an SNI1/2 or become an electron-capture SN. Our calculations stop due to an instability near the base of the convective envelope that hampers further convergence and leaves remnant envelope masses between 0.25 M_sun for our 4 M_sun model and 1.5 M_sun for our 9 M_sun model. We present two sets of C, N, and O yields derived from our full calculations and computed under two different assumptions, namely, that the instability causes a practically instant loss of the remnant envelope or that the stars recover and proceed with further thermal pulses. Our results have implications for the early chemical evolution of the Universe.Comment: 12 pages, 13 figures, accepted for publication in A&

Electron-induced proton knockout from neutron rich nuclei

We study the evolution of the \eep cross section on nuclei with increasing asymmetry between the number of neutrons and protons. The calculations are done within the framework of the nonrelativistic and relativistic distorted-wave impulse approximation. In the nonrelativistic model phenomenological Woods-Saxon and Hartree-Fock wave functions are used for the proton bound-state wave functions, in the relativistic model the wave functions are solutions of Dirac-Hartree equations. The models are first tested against experimental data on $^{40}$Ca and $^{48}$Ca nuclei, and then they are applied to a set of spherical calcium isotopes.Comment: 5 pages, 2 figures. contribution to the XIX International School on Nuclear Physics, Neutron Physics and Applications, Varna (Bulgaria) September 19-25, 201

Comparison of opioid prescribing by dentists in the United States and England

Importance: The United States consumes most of the opioids worldwide despite representing a small portion of the world\u27s population. Dentists are one of the most frequent US prescribers of opioids despite data suggesting that nonopioid analgesics are similarly effective for oral pain. While oral health and dentist use are generally similar between the United States and England, it is unclear how opioid prescribing by dentists varies between the 2 countries. Objective: To compare opioid prescribing by dentists in the United States and England. Design, Setting, and Participants: Cross-sectional study of prescriptions for opioids dispensed from outpatient pharmacies and health care settings between January 1 and December 31, 2016, by dentists in the United States and England. Data were analyzed from October 2018 to January 2019. Exposures: Opioids prescribed by dentists. Main Outcomes and Measures: Proportion and prescribing rates of opioid prescriptions. Results: In 2016, the proportion of prescriptions written by US dentists that were for opioids was 37 times greater than the proportion written by English dentists. In all, 22.3% of US dental prescriptions were opioids (11.4 million prescriptions) compared with 0.6% of English dental prescriptions (28 082 prescriptions) (difference, 21.7%; 95% CI, 13.8%-32.1%; P \u3c .001). Dentists in the United States also had a higher number of opioid prescriptions per 1000 population (35.4 per 1000 US population [95% CI, 25.2-48.7 per 1000 population] vs 0.5 per 1000 England population [95% CI, 0.03-3.7 per 1000 population]) and number of opioid prescriptions per dentist (58.2 prescriptions per dentist [95% CI, 44.9-75.0 prescriptions per dentist] vs 1.2 prescriptions per dentist [95% CI, 0.2-5.6 prescriptions per dentist]). While the codeine derivative dihydrocodeine was the sole opioid prescribed by English dentists, US dentists prescribed a range of opioids containing hydrocodone (62.3%), codeine (23.2%), oxycodone (9.1%), and tramadol (4.8%). Dentists in the United States also prescribed long-acting opioids (0.06% of opioids prescribed by US dentists [6425 prescriptions]). Long-acting opioids were not prescribed by English dentists. Conclusions and Relevance: This study found that in 2016, dentists in the United States prescribed opioids with significantly greater frequency than their English counterparts. Opioids with a high potential for abuse, such as oxycodone, were frequently prescribed by US dentists but not prescribed in England. These results illustrate how 1 source of opioids differs substantially in the United States vs England. To reduce dental opioid prescribing in the United States, dentists could adopt measures similar to those used in England, including national guidelines for treating dental pain that emphasize prescribing opioids conservatively

Impacts of reduction of deep levels and surface passivation on carrier lifetimes in p-type 4H-SiC epilayers

Impacts of reduction of deep levels and surface passivation on carrier lifetimes in p-type 4H-SiC epilayers are investigated. The authors reported that the carrier lifetime in n-type epilayers increased by reduction of deep levels through thermal oxidation and thermal annealing. However, the carrier lifetimes in p-type epilayers were not significantly enhanced. In this study, in order to investigate the influence of surface passivation on the carrier lifetimes, the epilayer surface was passivated by different oxidation techniques. While the improvement of the carrier lifetime in n-type epilayers was small, the carrier lifetime in p-type epilayers were remarkably improved by appropriate surface passivation. For instance, the carrier lifetime was improved from 1.4 μs to 2.6 μs by passivation with deposited SiO2 annealed in NO. From these results, it was revealed that surface recombination is a limiting factor of carrier lifetimes in p-type 4H-SiC epilayers