On the von Neumann and Frank-Wolfe Algorithms with Away Steps

The von Neumann algorithm is a simple coordinate-descent algorithm to determine whether the origin belongs to a polytope generated by a finite set of points. When the origin is in the of the polytope, the algorithm generates a sequence of points in the polytope that converges linearly to zero. The algorithm's rate of convergence depends on the radius of the largest ball around the origin contained in the polytope. We show that under the weaker condition that the origin is in the polytope, possibly on its boundary, a variant of the von Neumann algorithm that includes generates a sequence of points in the polytope that converges linearly to zero. The new algorithm's rate of convergence depends on a certain geometric parameter of the polytope that extends the above radius but is always positive. Our linear convergence result and geometric insights also extend to a variant of the Frank-Wolfe algorithm with away steps for minimizing a strongly convex function over a polytope

ON THE ECONOMIC LINK BETWEEN ASSET PRICES AND REAL ACTIVITY

This paper presents a model linking two financial markets (stocks and bonds) with the real business cycle, in the framework of the Consumption Capital Asset Pricing Model with Generalized Isoelastic Preferences. Besides interest rate term spread, the model includes a new variable to forecast economic activity: stock market term spread, which constitutes the slope of expected stock market returns. The empirical evidence documented in this paper suggests systematic relationships between the state of the business cycle and the shapes of two yield curves (interest rates and expected stock returns). Results are robust to changes in measures of economic growth, stock prices, interest rates and expectation-generating mechanisms.

State expansion, development imaginaries and mobility in a peripheral frontier: the case of Caracaraí, Brazil

This article examines social transformation and mobility dynamics in Caracaraí, a rural frontier town in the State of Roraima, Brazil, from the 1950s to the 1990s. During this short period, we observe a rapid diversification of migration in Caracaraí: from non-migratory mobility tied to the micro-scale extraction of local products to more-permanent settlement in town, rapid shifts in the direction of internal migration patterns and back to non-migratory mobility patterns again. Drawing from frontier migration studies and mobility transition theories, this paper adopts a social transformation perspective to explore the relation between social change and these mobility transitions. The changing role of the state, from a promoter of infrastructure to a provider of services and public employment, the restructuring of the local economic fabric and its reorientation towards more secondary and tertiary activities, and inhabitants’ imaginaries of the development potential of Caracaraí all explain the shift in migration processes. Investigating these processes, we observe that (i) the state promoted new opportunities, leading to a decline in traditional circular mobility, alongside the growth of temporal workers and spontaneous migrants; (ii) infrastructure advancements encouraged non-migratory mobility patterns between Caracaraí and Boa Vista, the capital city of the State of Roraima; (iii) the provision of public employment intensified internal rural-urban and urban-rural migration patterns, from communities in the interior of the State of Roraima to Caracaraí and vice versa, and (iv) development imaginaries – the perception of how Caracaraí should and could be in the near future – prevented voluminous emigration, during periods of socio-economic slowdown. This research highlights the meaningful role of the state in altering livelihoods and migration decision-making processes. In particular, it shows how state expansion framed cultural imaginaries of the ‘good life’, favouring the desire to stay put in periods of high economic uncertainty, even when life aspirations were not being met by local opportunitie

Effect of SKN-1 on Stress Responses on Caenorhabditis elegans

SKN-1 (protein Skinhead-1) plays a central role in promoting C. elegans longevity. The human ortholog is Nrf/CNC protein. It is a regulator of stress response as well as a defense to foreign substances. In this experiment, we investigate whether SKN-1 functions similarly to Nrf/CNC proteins in resisting oxidative stress in C. elegans. Silencing the gene skn-1 using RNAi is expected to modify the response to oxidative stress. PCR primers were designed to amplify a portion of the skn-1 gene in C. elegans. The amplicon from the PCR experiment was used to create an RNAi feeding vector. To assay sensitivity to oxidative stress, two groups of young adults were subjected to oxidative stress. The control group was fed the usual bacterial feeding strain (OP50), whereas the experimental group was fed my RNAi feeding strain. Worms were scored using standard lifetime assay procedure

Variación de la morfología floral en cinco especies de Penstemon (Plantaginaceae) que muestran el síndrome de polinización de himenópteros

Background: Geographic distance promotes phenotypic variation by facilitating environmental distance, limiting gene flow, and exposing plants to different pollen vectors. Therefore, understanding how plant morphology changes across a geographic range improves our understanding of the drivers of morphological diversification both on a macro- and micro-evolutionary scale. Questions: 1) How do geographic location and abiotic factors affect flower morphology between populations? 2) Is there a geographic pattern of flower morphology variation? and 3) How does yearly variation in temperature and precipitation affect flower morphology within populations? Studied species: Penstemon albidus, P. fruticosus, P. glandulosus, P. speciosus, and P. whippleanus Study site and dates: The continental USA, summers of 2017 and 2018 Methods: Fifty-seven populations and 496 individuals were selected at random to measure ten floral traits. Bioclimatic variables were extracted from the WorldClim database and NOAA. Linear models, partial least squares regression, Mantel tests and canonical correlation analysis were used to analyze the data. Results: Geographic variables alone explained a significant portion of the variation in flower morphology in two species, while in others, flower morphology did not vary despite large geographic distances. Penstemon albidus and P. whippleanus flowers increase in size from south-north, while P. glandulosus and P. speciosus exhibited an east-west increasing trend. Additionally, mean annual precipitation was the most important variable influencing P. glandulosusflower morphology. Conclusions: Geographic distance facilitates isolation-by-distance and isolation-by-phenology as well as abiotic differences between populations; however, other factors such as pollinators might be keeping populations morphologically homogeneous despite large geographic distance.publishedVersio

A Multiple Radar Approach for Automatic Target Recognition of Aircraft using Inverse Synthetic Aperture Radar

Along with the improvement of radar technologies, Automatic Target Recognition (ATR) using Synthetic Aperture Radar (SAR) and Inverse SAR (ISAR) has come to be an active research area. SAR/ISAR are radar techniques to generate a two-dimensional high-resolution image of a target. Unlike other similar experiments using Convolutional Neural Networks (CNN) to solve this problem, we utilize an unusual approach that leads to better performance and faster training times. Our CNN uses complex values generated by a simulation to train the network; additionally, we utilize a multi-radar approach to increase the accuracy of the training and testing processes, thus resulting in higher accuracies than the other papers working on SAR/ISAR ATR. We generated our dataset with 7 different aircraft models with a radar simulator we developed called RadarPixel; it is a Windows GUI program implemented using Matlab and Java programming, the simulator is capable of accurately replicating a real SAR/ISAR configurations. Our objective is to utilize our multi-radar technique and determine the optimal number of radars needed to detect and classify targets.Comment: 8 pages, 9 figures, International Conference for Data Intelligence and Security (ICDIS

Recharge Uncertainty Analysis of Major Aquifers in Texas

While the reduction of the groundwater available volume in the state of Texas of urban, agricultural, and industrial use has been dealt with in different ways, the first step is to assess the current and future behavior of the aquifers that supply it. For this the Texas Water Development Board created the Groundwater Availability models. This paper studies the recharge data used to build them and how the sensitivity to changes in recharge of each aquifer can affect the available groundwater statewide to point to interest aquifers that need a more in-depth recharge analysis. The reported recharge in the models was variated from 50% to 150% to determine changes in head, stored volume, and overall baseflow. The normalized variations where then compared to select the most and least recharge sensitive aquifers to perform a recharge surge reflecting that of hurricane Harvey (1000% normal recharge) in the Gulf Coast Center (Houston, Texas) to determine the behavior when subjected to atypical recharge events. Given the great geohydrological variability, not only inside the aquifers, but between the analyzed aquifers, the changes in head, volume, and baseflow do not only follow the greatest increase in recharge. The Hueco Mesilla Bolson aquifer experienced the least absolute change in mean head (0.0003% of normal head), paired with the lowest absolute change in recharge (0.004m1 y -1). However, the Edwards Balcones Fault Zone Springs (near San Antonio, Texas) experiences the largest absolute change in recharge (0.370m-1 y -1), but the Gulf Coast North experienced the largest absolute change in mean head (42% of normal head). While the differences in composition and size of the aquifers make a complete comparison difficult, the most sensitive aquifers, determined by the linear model to which head and stored volume were subjected to, were determined to be the Trinity North and the Edwards Trinity Plateau for respectively. These two can be the focus of subsequent and more localized studies to determine the feasibility of the recharge driven strategies to increase the groundwater availability of Texas

Moving across (Im)mobility categories: the importance of values, family and adaptation for migration

The aspiration-capability framework introduces four (im)mobility categories–mobility, voluntary immobility, involuntary immobility and acquiescent immobility–which have received considerable attention. However, few studies have examined how people move across such categories. Drawing on the migration experiences of 17 self-identified Latin American gay individuals, this paper shows how prospective migrants can be pushed into a state of involuntary immobility by their families, and how they can adapt to overcome immobility and fulfil their migration aspirations. The article finds, firstly, that heteronormative values and familial expectations regarding sexuality shape the possibility of mobilizing the family’s economic, informative and emotional resources. Secondly, I discuss the adaptation strategies that individuals use to surpass involuntary immobility. To understand movement across (im)mobility categories, as well as the role of social boundaries for migration, this paper differentiates between individual and collective migration aspirations and capabilities. In doing so, the article introduces an approach to explore how interactions between social groups and their individual group members shape the (im)mobility projects of the latter