"Migration of Talent: Foreign Students and Graduate Economics Education in the United States"

In this paper, Rao tackles the reasons behind the increasing number and share of foreign students enrolled in Ph.D. economics programs in the U.S. The conventional argument of comparative advantage in U.S. graduate economics education fails to stand up under closer scrutiny. In addition to not explaining the actual and relative decline of American students pursuing graduate economics education, the traditional view fails to explain the relatively narrow scope of foreign students in these programs: The majority of foreign students come from a few Asian countries (e.g., India, South Korea, China, and Taiwan). Among the questions posed in this paper are the reasons for the change in the proportion of foreign students over time, and the effect of this change on American graduate (and undergraduate) economics education. It is surmised that most foreign students enroll in American Ph.D. programs to facilitate their migration to this country. Given the relative ease of securing work permission as a university faculty member-for which a U.S. Ph.D. is essential-most foreign students view an American Ph.D. and a subsequent academic job as an ideal entree to the U.S. In contrast, the most popular postgraduate path for American college economics majors is business or law school, and the appropriate strategy for these institutions is to offer a curriculum that fosters successful completion of an M.B.A. or J.D. via a general rather than a specialized economics training. Meanwhile, Rao ponders the possibility of "reverse foreign aid" occurring: After all, the home governments of these students are not compensated for their education subsidies through the undergraduate level. In sum, he suggests that the influx of foreign Ph.D. students-who typically receive financial aid from U.S. institutions-must be considered as a positive phenomenon. Since most of these students remain in the U.S. and become part of the vital stock of human capital, the financial aid awarded them should be regarded as an investment in a productive asset.

"Money, Growth, Distribution, and Prices in a Simple Sraffian Economy"

Rejecting neoclassical notions of supply and demand, Sraffa demonstrated that relative prices are determined by the profit rate. However, a Sraffa model fails to explicitly describe the determination of output, growth, and accumulation. Rao closes this model with a monetary sector, and examines the effects in both a Sraffian and a Classical world. Rao integrates a two class, simple Sraffian production economy with an assets market. The production side yields capital and consumption goods using Sraffian technology, while assets consist of money (printed and distributed by the Central Bank) and the stock of capital. Different approaches to the labor market yield two distinct models: Sraffian and Classical. The principal conclusion is that, in a Sraffian world, Central Bank policy, via its influence on the profit rate, controls the long-run distribution of income and relative prices. In a Classical regime-in which the real wage (and so the profit rate) is exogenously driven the Central Bank controls long-run economic growth.

MGF Approach to the Analysis of Generalized Two-Ray Fading Models

We analyze a class of Generalized Two-Ray (GTR) fading channels that consist of two line of sight (LOS) components with random phase plus a diffuse component. We derive a closed form expression for the moment generating function (MGF) of the signal-to-noise ratio (SNR) for this model, which greatly simplifies its analysis. This expression arises from the observation that the GTR fading model can be expressed in terms of a conditional underlying Rician distribution. We illustrate the approach to derive simple expressions for statistics and performance metrics of interest such as the amount of fading, the level crossing rate, the symbol error rate, and the ergodic capacity in GTR fading channels. We also show that the effect of considering a more general distribution for the phase difference between the LOS components has an impact on the average SNR.Comment: 14 pages, 8 Figures and 2 Tables. This work has been accepted for publication at IEEE Transactions on Wireless Communications. Copyright (c) 2014 IEEE. Personal use of this material is permitted. However, permission to use this material for any other purposes must be obtained from the IEEE by sending a request to [email protected]

Explicit Finite Element Modeling of the Human Lumbar Spine

Validated finite element (FE) models of the functional spinal unit (FSU) and lumbar spine are essential in design-phase device development and in assessing the mechanics associated with normal spine function and degenerative disc disease (DDD), as well as the impact of fusion and total disc replacement (TDR). Although experimental data from fully intact specimens can be used for model calibration and validation, the contributions from the individual structures (disc, facets, and ligaments) may be inappropriately distributed. Hence, creation of decompression conditions or device implantations that require structure removal may not have the proper resulting mechanics. An explicit FE formulation may be advantageous compared to standard analysis due to efficiency in handling complex, changing contact conditions and the ability to evaluate either rigid or deformable body contact. Also, probabilistic studies based on these deterministic FE formulations are of great interest currently as model input parameters (such as properties of nucleus, annulus, ligament stiffness and facet material and geometric orientation) have been characterized experimentally, but contain substantial variability. The use of these FE formulations is not only valuable from an intact spine point of view, but also relevant in understanding and improving the design outcome of procedures like the total disc replacement (TDR). It has been shown that clinical outcome and the incidence of adjacent level disease is linked to the range of motion achieved by the introduction of these disc replacement devices like the ProDisc-L (Synthes Spine, West Chester, PA). Placement of the spherical center of the device as close as possible to the anatomical axis of rotation of the segment is essential in achieving optimal performance. Accordingly, an explicit FE model of the lumbosacral spine and FSU\u27s L2-L3 and L4-L5 using subject-specific in vitro data was developed using sequential transection of each structure. In addition, the objective of this dissertation was to develop a computationally efficient, probabilistic explicit FE model of the lumbar spine, to evaluate spine mechanics for the FSU\u27s L2-L3 and L4-L5. This probabilistic modeling approach was used to assess the capability of efficient probabilistic analyses to predict performance incorporating disc and ligament material variability as well as geometric variability of the facet joint. A well calibrated deterministic and probabilistic model can be used as an excellent computational tool to predict the behavior of the spine with implants like the ProDisc-L. This dissertation also investigates the effect of altering the position of the Prodisc-L implanted in a FE model on ROM during flexion-extension, lateral bending, and axial rotation. Specifically, ROM, bone impingement, implant impingement, and facet forces were evaluated with varying anterior-posterior and medial-lateral placement of the TDR implant. The uniqueness of this work is the method developed to tune the individual structures in calibrating the FE model using sequential sectioning. This strong calibration against subject-specific in vitro data developed confidence in the predictive power of this FE model. For an applied torque, the rotational root mean squared error between the model predictions and the experimental results were within 0.15deg averaged during flexion and extension. The probabilistic analysis compared some of the advanced reliability and probabilistic techniques with the Monte Carlo simulation which is considered the gold standard. The efficient methods accurately estimated the results from Monte Carlo simulation in approximately 5% of computational time. This study on the implanted spine performed on four different spine models showed the importance of using FE techniques as a pre-op templating tool in decision making process for spinal procedures

Outcomes following abdominoperineal resection 6 years retrospective study at a rural district general hospital

Background: A range of surgical techniques are used for perineal wound closure following Abdominoperineal Excision of the Rectum (APER). The aim of this study was to assess the safety and effectiveness of using a biological mesh for perineal wound closure and to compare the outcomes following conventional suture and mesh closure of the perineal wound.Methods: A single-centre retrospective study of a cohort of patients undergoing surgery for low rectal cancer between January 2013 and December 2018. Patient records were analysed for outcomes including perineal complication rates, length of hospital stay and impact of patient factors on complication rates in mesh vs no mesh group.Results: Of the total 43 patients included in the study, 13 (30%) had a conventional perineal closure whereas 30 patients (70%) had a biological mesh reconstruction.  Early perineal wound complications were seen in 21/43 (49%) patients. Of those, 6 (29%) patients were in the no mesh group compared to 15 (71%) patients in the mesh group (p = 0.81). 84% of the patients who received neo adjuvant radiotherapy (NART) developed perineal wound infection. There was no statistically significant difference in the mesh and no mesh groups. None of the patient factors, other than preoperative anaemia, had a statistically significant association with the rate of complications in either of the groups.Conclusions: There was no statistically significant difference in the complication rate between primary and biological mesh closure. Biological mesh is safe for perineal reconstruction following APER

Decentralized optimization over noisy, rate-constrained networks: Achieving consensus by communicating differences

In decentralized optimization, multiple nodes in a network collaborate to minimize the sum of their local loss functions. The information exchange between nodes required for this task, is often limited by network connectivity. We consider a setting in which communication between nodes is hindered by both (i) a finite rate-constraint on the signal transmitted by any node, and (ii) additive noise corrupting the signal received by any node. We propose a novel algorithm for this scenario: Decentralized Lazy Mirror Descent with Differential Exchanges (DLMD-DiffEx), which guarantees convergence of the local estimates to the optimal solution under the given communication constraints. A salient feature of DLMD-DiffEx is the introduction of additional proxy variables that are maintained by the nodes to account for the disagreement in their estimates due to channel noise and rate-constraints. Convergence to the optimal solution is attained by having nodes iteratively exchange these disagreement terms until consensus is achieved. In order to prevent noise accumulation during this exchange, DLMD-DiffEx relies on two sequences; one controlling the power of the transmitted signal, and the other determining the consensus rate. We provide clear insights on the design of these two sequences which highlights the interplay between consensus rate and noise amplification. We investigate the performance of DLMD-DiffEx both from a theoretical perspective as well as through numerical evaluations.Comment: 15 pages, 6 figure