A Leslie matrix approach to an age-structured epidemic

We consider a Leslie-type matrix approach to an SIR epidemic in discrete time. We give examples of the population of susceptibles, infectives, and removals for different birth rates and two different infection rates. Finally, when the infection rate depe

Exchange Rates and Local Labor Markets

We document the consequences of real exchange rate movements for the employment, hours, and hourly earnings of workers in manufacturing industries across individual states. Exchange rates have statistically significant wage and employment implications in these local labor markets. The importance and size of these dollar-induced effects vary considerably across industries and are more pronounced in some U.S. regions. In addition to the importance of exchange rate shocks, we confirm prior research results showing that relatively strong local conditions drive up wage in local industries, while anticipated future (positive) local shocks reduce current wages.

The Economic Costs of the Iraq War: An Appraisal Three Years After the Beginning of the Conflict

This paper attempts to provide a more complete reckoning of the costs of the Iraq War, using standard economic and accounting/ budgetary frameworks. As of December 30, 2005, total spending for combat and support operations in Iraq is $251bn, and the CBO's estimates put the projected total direct costs at around$500bn. These figures, however, greatly underestimate the War's true costs. We estimate a range of present and future costs, by including expenditures not in the $500bn CBO projection, such as lifetime healthcare and disability payments to returning veterans, replenishment of military hardware, and increased recruitment costs. We then make adjustments to reflect the social costs of the resources deployed, (e.g. reserve pay is less than the opportunity wage and disability pay is less than forgone earnings). Finally, we estimate the effects of the war on the overall performance of the economy. Even taking a conservative approach and assuming all US troops return by 2010, we believe the true costs exceed a trillion dollars. Using the CBO's projection of maintaining troops in Iraq through 2015, the true costs may exceed$2 trillion. In either case, the cost is much larger than the administration's original estimate of $50-$60bn. The costs estimated do not include those borne by other countries, either directly (military expenditures) or indirectly (the increased price of oil). Most importantly, we have not included the costs to Iraq, either in terms of destruction of infrastructure or the loss of lives. These would all clearly raise the costs significantly.

Electronic Transport on the Shastry-Sutherland Lattice in Ising-type Rare Earth Tetraborides

In the presence of a magnetic field frustrated spin systems may exhibit plateaus at fractional values of saturation magnetization. Such plateau states are stabilized by classical and quantum mechanisms including order-by-disorder, triplon crystallization, and various competing order effects. In the case of electrically conducting systems, free electrons represent an incisive probe for the plateau states. Here we study the electrical transport of Ising-type rare earth tetraborides $R$B$_4$ ($R=$Er, Tm), a metallic Shastry-Sutherland lattice showing magnetization plateaus. We find that the longitudinal and transverse resistivities reflect scattering with both the static and dynamic plateau structure. We model these results consistently with the expected strong uniaxial anisotropy in a quantitative level, providing a framework for the study of plateau states in metallic frustrated systems.Comment: 18 pages, 5 figure

Communication training for aircrews: A review of theoretical and pragmatic aspects of training program design

This study is the final report of a project studying methods of communications training applicable to both civilian and military aviation personnel, including multiperson teams or single pilot fixed wing or rotary wing aircraft. A review is provided of a number of theories proposed as relevant for producing training materials for improved communications. Criteria are given for evaluating the applicability of training programs to the aviation environment, and these criteria are applied to United Airlines' Resources Management Training, as well as to a number of commercially available general purpose training programs. The report considers in detail assertiveness training and grid management training, examining their theoretical background and attempts made to validate their effectiveness. It was found that there are substantive difficulties in assessing the effectiveness of both training programs, as well as problems with the theories underlying them. However, because the aviation environment offers unique advantages for studying the effectiveness of communications training, recommendations are made on the design of appropriate training programs and on procedures that might be used to validate them

Transport Signatures of Fermi Surface Topology Change in BiTeI

We report a quantum magnetotransport signature of a change in Fermi surface topology in the Rashba semiconductor BiTeI with systematic tuning of the Fermi level $E_F$. Beyond the quantum limit, we observe a marked increase/decrease in electrical resistivity when $E_F$ is above/below the Dirac node that we show originates from the Fermi surface topology. This effect represents a measurement of the electron distribution on the low-index ($n=0,-1$) Landau levels and is uniquely enabled by the finite bulk $k_z$ dispersion along the $c$-axis and strong Rashba spin-orbit coupling strength of the system. The Dirac node is independently identified by Shubnikov-de Haas oscillations as a vanishing Fermi surface cross section at $k_z=0$. Additionally we find that the violation of Kohler's rule allows a distinct insight into the temperature evolution of the observed quantum magnetoresistance effects.Comment: 12 pages, 4 figure

Extreme Magnetoresistance in Magnetic Rare Earth Monopnictides

The acute sensitivity of the electrical resistance of certain systems to magnetic fields known as extreme magnetoresistance (XMR) has recently been explored in a new materials context with topological semimetals. Exemplified by WTe$_{2}$ and rare earth monopnictide La(Sb,Bi), these systems tend to be non-magnetic, nearly compensated semimetals and represent a platform for large magnetoresistance driven by intrinsic electronic structure. Here we explore electronic transport in magnetic members of the latter family of semimetals and find that XMR is strongly modulated by magnetic order. In particular, CeSb exhibits XMR in excess of $1.6 \times 10^{6}$ % at fields of 9 T while the magnetoresistance itself is non-monotonic across the various magnetic phases and shows a transition from negative magnetoresistance to XMR with field above magnetic ordering temperature $T_{N}$. The magnitude of the XMR is larger than in other rare earth monopnictides including the non-magnetic members and follows an non-saturating power law to fields above 30 T. We show that the overall response can be understood as the modulation of conductivity by the Ce orbital state and for intermediate temperatures can be characterized by an effective medium model. Comparison to the orbitally quenched compound GdBi supports the correlation of XMR with the onset of magnetic ordering and compensation and highlights the unique combination of orbital inversion and type-I magnetic ordering in CeSb in determining its large response. These findings suggest a paradigm for magneto-orbital control of XMR and are relevant to the understanding of rare earth-based correlated topological materials.Comment: 21 pages, 6 figure