Computational Economics: Help for the Underestimated Undergraduate

Our concern in this paper is that the capability of economics undergraduates is substantially underestimated in the design of the present college curriculum and that our students are insufficiently challenged and motivated. Students enter our classrooms with substantial previous knowledge about computers and computation and we are not taking full advantage of this opportunity. We suggest a set of examples from computational economics which are challenging enough to motivate students and simple enough that they can master them within a few hours. By encouraging the students to modify the models in directions of their own interest avenues for creative endeavor are opened which deeply involve the students in their own education.teaching computational economics

A Taylor Rule for Fiscal Policy

In times of rapid macroeconomic change it would seem useful for both fiscal and monetary policy to be modified frequently. This is true for monetary policy with monthly meetings of the Open Market Committee. It is not true for fiscal policy which mostly varies with the annual Congressional budget cycle. This paper proposes a feedback framework for analyzing the question of whether or not movement from annual to quarterly fiscal policy changes would improve the performance of stabilization policy. More broadly the paper considers a complementary rather than competitive framework in which monetary policy in the form of the Taylor rule is joined by a similar fiscal policy rule. This framework is then used to consider methodological improvements in the Taylor and the fiscal policy rule to include lags, uncertainty in parameters and measurement errors.design of fiscal policy, optimal experimentation, stochastic optimization, time-varying parameters, numerical experiments

Expected optimal feedback with Time-Varying Parameters

In this paper we derive, by using dynamic programming, the closed loop form of the Expected Optimal Feedback rule with time varying parameter. As such this paper extends the work of Kendrick (1981, 2002, Chapter 6) for the time varying parameter case. Furthermore, we show that the Beck and Wieland (2002) model can be cast into this framework and can be treated as a special case of this solution.

Expected optimal feedback with Time-Varying Parameters

In this paper we derive the closed loop form of the Expected Optimal Feedback rule, sometimes called passive learning stochastic control, with time varying parameters. As such this paper extends the work of Kendrick (1981,2002, Chapter 6) where parameters are assumed to vary randomly around a known constant mean. Furthermore, we show that the cautionary myopic rule in Beck and Wieland (2002) model, a test bed for comparing various stochastic optimizations approaches, can be cast into this framework and can be treated as a special case of this solution.Optimal experimentation, stochastic optimization, time-varying parameters, expected optimal feedback

Potential atmospheric impact of the Toba Mega‐Eruption ∼71,000 years ago

An ∼6‐year long period of volcanic sulfate recorded in the GISP2 ice core about 71,100 ± 5000 years ago may provide detailed information on the atmospheric and climatic impact of the Toba mega‐eruption. Deposition of these aerosols occur at the beginning of an ∼1000‐year long stadial event, but not immediately before the longer glacial period beginning ∼67,500 years ago. Total stratospheric loading estimates over this ∼6‐year period range from 2200 to 4400 Mt of H2SO4 aerosols. The range in values is given to compensate for uncertainties in aerosol transport. Magnitude and longevity of the atmospheric loading may have led directly to enhanced cooling during the initial two centuries of this ∼1000‐year cooling event

Volcanic aerosol records and tephrochronology of the Summit, Greenland, ice cores

The recently collected Greenland Ice Sheet Project 2 (GISP2) and Greenland Ice Core Project ice cores from Summit, Greenland, provide lengthy and highly resolved records of the deposition of both the aerosol (H2SO4) and silicate (tephra) components of past volcanism. Both types of data are very beneficial in developing the hemispheric to global chronology of explosive volcanism and evaluating the entire volcanism‐climate system. The continuous time series of volcanic SO42− for the last 110,000 years show a strong relationship between periods of increased volcanism and periods of climatic change. The greatest number of volcanic SO42− signals, many of very high magnitude, occur during and after the final stages of deglaciation (6000–17,000 years ago), possibly reflecting the increased crustal stresses that occur with changing volumes of continental ice sheets and with the subsequent changes in the volume of water in ocean basins (sea level change). The increase in the number of volcanic SO42− signals at 27,000–36,000 and 79,000–85,000 years ago may be related to initial ice sheet growth prior to the glacial maximum and prior to the beginning of the last period of glaciation, respectively. A comparison of the electrical conductivity of the GISP2 core with that of the volcanic SO42− record for the Holocene indicates that only about half of the larger volcanic signals are coincident in the two records. Other volcanic acids besides H2SO4 and other SO42− sources can complicate the comparisons, although the threshold level picked to make such comparisons is especially critical. Tephra has been found in both cores with a composition similar to that originating from the Vatnaöldur eruption that produced the Settlement Layer in Iceland (mid‐A.D. 870s), from the Icelandic eruption that produced the Saksunarvatn ash (∼10,300 years ago), and from the Icelandic eruption(s) that produced the Z2 ash zone in North Atlantic marine cores (∼52,700 years ago). The presence of these layers provides absolute time lines for correlation between the two cores and for correlation with proxy records from marine sediment cores and terrestrial deposits containing these same tephras. The presence of both rhyolitic and basaltic shards in the Z2 ash in theGISP2 core and the composition of the basaltic grains lend support to multiple Icelandic sources (Torfajökull area and Katla) for the Z2 layer. Deposition of the Z2 layer occurs at the beginning of a stadial event, further reflecting the possibility of a volcanic triggering by the effects of changing climatic conditions

Investigating UAS Operator Characteristics Influencing Mission Success

The two objectives of this study were to 1) evaluate how specific operator characteristics (prior experience in manned and unmanned flight, teamwork, and gaming) influence mission success in unmanned aircraft systems (UAS) operations; and 2) evaluate the potential utility of a performance assessment tool. Mission success was assessed using a modified version of the Situation Awareness Linked Indicators Adapted to Novel Tasks (SALIANT) methodology. Eighteen participants completed a UAS scenario (port security) as part of 9 two-person crews (pilot and sensor operator). Results showed that the SALIANT measure was able to discriminate differences in performance among the UAS crews. Results also revealed significant correlations between the targeted operator characteristics and several of the SALIANT indicators. Findings from this study will be used to refine the SALIANT measure to support future research on how to optimize human performance in this domain

The Autophagy Receptor TAX1BP1 and the Molecular Motor Myosin VI Are Required for Clearance of Salmonella Typhimurium by Autophagy.

Autophagy plays a key role during Salmonella infection, by eliminating these pathogens following escape into the cytosol. In this process, selective autophagy receptors, including the myosin VI adaptor proteins optineurin and NDP52, have been shown to recognize cytosolic pathogens. Here, we demonstrate that myosin VI and TAX1BP1 are recruited to ubiquitylated Salmonella and play a key role in xenophagy. The absence of TAX1BP1 causes an accumulation of ubiquitin-positive Salmonella, whereas loss of myosin VI leads to an increase in ubiquitylated and LC3-positive bacteria. Our structural studies demonstrate that the ubiquitin-binding site of TAX1BP1 overlaps with the myosin VI binding site and point mutations in the TAX1BP1 zinc finger domains that affect ubiquitin binding also ablate binding to myosin VI. This mutually exclusive binding and the association of TAX1BP1 with LC3 on the outer limiting membrane of autophagosomes may suggest a molecular mechanism for recruitment of this motor to autophagosomes. The predominant role of TAX1BP1, a paralogue of NDP52, in xenophagy is supported by our evolutionary analysis, which demonstrates that functionally intact NDP52 is missing in Xenopus and mice, whereas TAX1BP1 is expressed in all vertebrates analysed. In summary, this work highlights the importance of TAX1BP1 as a novel autophagy receptor in myosin VI-mediated xenophagy. Our study identifies essential new machinery for the autophagy-dependent clearance of Salmonella typhimurium and suggests modulation of myosin VI motor activity as a potential therapeutic target in cellular immunity.FB and DAT thank the Wellcome Trust (www.wellcome.ac.uk) for funding of a University Award to FB (086743), the CIMR Strategic Award (100140) and an equipment grant [093026]. FB also thanks the Medical Research Council UK (www.mrc.ac.uk) for funding of a project grant (MR/K000888/1). JKJ, MA and MB were supported by the Medical Research Council UK (www.mrc.ac.uk) (U105184325).This is the final published version. It first appeared at http://dx.doi.org/10.1371/journal.ppat.100517