7,353 research outputs found
The dynamics of immigration policy with wealth-heterogeneous immigrants
In this paper we consider a simple intertemporal economy in which immigrants, if admitted, bring heterogeneous amounts of capital. We show that under certain conditions there is a level of immigration which maximizes the economy's capital-labor ratio, and that this level of immigration is the preferred choice of a majority of the economy's citizens. We then characterize, in an overlapping generations setting, the dynamics of capital accumulation and immigration policy, which can include multiple steady state equilibria and a sensitivity of immigration levels to changes in the economy's technology growth rate.Emigration and immigration
Attribution of intentional causation influences the perception of observed movements: behavioral evidence and neural correlates
Recent research on human agency suggests that intentional causation is associated with a subjective compression in the temporal interval between actions and their effects. That is, intentional movements and their causal effects are perceived as closer together in time than equivalent unintentional movements and their causal effects. This so-called intentional binding effect is consistently found for one's own self-generated actions. It has also been suggested that intentional binding occurs when observing intentional movements of others. However, this evidence is undermined by limitations of the paradigm used. In the current study we aimed to overcome these limitations using a more rigorous design in combination with functional Magnetic Resonance Imaging (fMRI) to explore the neural underpinnings of intentional binding of observed movements. In particular, we aimed to identify brain areas sensitive to the interaction between intentionality and causality attributed to the observed action. Our behavioral results confirmed the occurrence of intentional binding for observed movements using this more rigorous paradigm. Our fMRI results highlighted a collection of brain regions whose activity was sensitive to the interaction between intentionality and causation. Intriguingly, these brain regions have previously been implicated in the sense of agency over one's own movements. We discuss the implications of these results for intentional binding specifically, and the sense of agency more generally
Position dependent rate dampening in any active hand controller
A control system for an active hand controller, for example, uses a control stick connected to and controlled by a motor. Electronics are provided to control the motor to eliminate oscillations due to motor torque and high gain due to breakout at the control stick when the control stick is at about its null position. Both hardware as well as software implementations can provide position dependent dampening to the control sticks such that when the control stick is located about a null position, a higher rate of dampening is provided than when the control stick is located outside the null position, when a lower rate of dampening is provided. The system provides a stable active hand controller control stick without degraded force and feel characteristics of the system
The Roughness Properties of Small Ice-Bearing Craters at the South Pole of the Moon: Implications for Accessing Fresh Water Ice in Future Surface Operations
The lunar poles provide a fascinating thermal environment capable of cold-trapping water ice on geologic timescales [1]. While there have been many observations indicating the presence of water ice at the lunar surface [e.g., 24], it is still not clear when this ice was delivered to the Moon. The timing of volatile dep-osition provides important constraints on the origin of lunar ice because different delivery mechanisms have been active at different times throughout lunar history. We previously found that some small (<10 km) cra-ters at the south pole of the Moon have morphologies suggestive of relatively young ages, on the basis of crisp crater rims [5]. These craters are too small to date with robust cratering statistics [5], but the possibility of ice in young craters is intriguing because it suggests that there is some recent and perhaps ongoing mechanism that is delivering or redistributing water to polar cold traps. Therefore, understanding if these small, ice-bear-ing craters are indeed young is essential in understand-ing the age and source of volatiles on the Moon. Here we take a new approach to understand the ages of these small polar cold traps: analyzing the roughness properties of small ice-bearing craters. It is well under-stood that impact crater properties (e.g., morphology, rock abundance, and roughness) evolve with time due to a variety of geologic and space-weathering processes [611]. Topographic roughness is a measurement of the local deviation from the mean topography, providing a measurement of surface texture, and is a powerful tool for evaluating surface evolution over geologic time [e.g., 1114]. In this study we analyze the roughness of southern lunar craters (40S90S) from all geologic eras, and determine how the roughness of small (<10 km) ice-bearing craters compare. We discuss the implications of the ages of ice-bearing south polar craters, and potential strategies for accessing fresh ice on the Moon
MARKETING CHARACTERISTICS ASSOCIATED WITH SEAFOOD COUNTERS IN GROCERY STORES
This study provides a benchmark analysis of seafood counter characteristics corresponding to the peaking of per capita seafood demand in the U.S. Logistic regression results show separate seafood counters are less likely in small stores, in rural stores, and in stores in low or medium income areas. Chain stores and stores with a significant number of non-white customers were more likely to have a seafood counter. Stores in the East South Central region were less likely, and stores in New England more likely, to have a seafood counter. The likelihood that stores will develop seafood counters was related to differences in sales volume, floor space, urban/rural location, income level of clients and regional location. Continuing innovations in marketing technology of seafood counters are likely to provide expanded marketing opportunities in the future.Marketing,
GABAergic compensation in connexin36 knock-out mice evident during low-magnesium seizure-like event activity
Gap junctions within the cerebral cortex may facilitate cortical seizure formation by their ability to synchronize electrical activity. To investigate this, one option is to compare wild-type (WT) animals with those lacking the gene for connexin36 (Cx36 KO); the protein that forms neuronal gap junctions between cortical inhibitory cells. However, genetically modified knock-out animals may exhibit compensatory effects; with the risk that observed differences between WT and Cx36 KO animals could be erroneously attributed to Cx36 gap junction effects. In this study we investigated the effect of GABAA-receptor modulation (augmentation with 16 μM etomidate and blockade with 100 μM picrotoxin) on low-magnesium seizure-like events (SLEs) in mouse cortical slices. In WT slices, picrotoxin enhanced both the amplitude (49% increase, p = 0.0006) and frequency (37% increase, p = 0.005) of SLEs; etomidate also enhanced SLE amplitude (18% increase, p = 0.003) but reduced event frequency (25% decrease, p < 0.0001). In Cx36 KO slices, the frequency effects of etomidate and picrotoxin were preserved, but the amplitude responses were abolished. Pre-treatment with the gap junction blocker mefloquin in WT slices did not significantly alter the drug responses, indicating that the reduction in amplitude seen in the Cx36 KO mice was not primarily mediated by their lack of interneuronal gap junctions, but was rather due to pre-existing compensatory changes in these animals. Conclusions from studies comparing seizure characteristics between WT and Cx36 KO mice must be viewed with a degree of caution because of the possible confounding effect of compensatory neurophysiological changes in the genetically modified animals
Internal Flow Physics of a Fluidic Oscillator in the Transition Regime
An experimental investigation of the underlying flow physics of a dual jet interaction fluidic oscillator has been conducted in the transition regime for a Reynolds number of 1680. The transition regime is defined as a narrow range of flow rates between two other operating modes of the fluidic oscillator. Particle image velocimetry (PIV) was used with refractive index matching sodium iodide solution to minimize reflections from the actuator geometry and obtain detailed internal velocity fields. PIV results showed that the inter-action of the two internal jets and the resultant vortices are responsible for the oscillation mechanism in the transition regime. Two side vortices sustain their existence throughout the oscillation period by altering their size, shape and strength, and a dome vortex is created twice each oscillation period (once from each jet). The dome vortex plays a key role in the kinetic energy transfer mechanism inside the oscillator by means of jet bifurcations. The primary oscillation mechanism in the transition regime is that each internal jet’s connection with the exiting jet is cut completely by the dome vortex in every period. This is in contrast to the low flow rate oscillation mechanism in which the oscillations are created by continuous collisions of the jets. Furthermore, the internal jets were observed to energize the side vortex on the opposite side of the chamber – a phenomenon which was not observed in the low flow rate regimeDFG, 200291049, SFB 1029: TurbIn - Signifikante Wirkungsgradsteigerung durch gezielte, interagierende Verbrennungs- und Strömungsinstationaritäten in Gasturbine
INCORPORATING GOVERNMENT PROGRAM PROVISIONS INTO A MEAN-VARIANCE FRAMEWORK
E-V studies traditionally have relied on historical data to calculate returns and variance. Historical data may not fully reflect current conditions, particularly when decisions involve government-supported crops. This paper presents a method for calculating mean and variance using subjectively-estimated data. The method is developed for both government-supported and non-program crops. Comparisons to alternative methods suggest the approach provides reasonable accuracy.Agricultural and Food Policy,
Multi-Coset Sparse Imaging Arrays
We develop an efficient structured sparse antenna array architecture for coherent imaging of sparse but otherwise unknown scenes. In this architecture, the array elements are configured in a periodic nonuniform pattern that can be viewed as the superposition of multiple sparse uniform subarrays. For such structure, we develop an efficient pattern design procedure using co-array analysis, and we describe robust and efficient algorithms implementing the required associated array processing, which comprise scene support recovery, followed by image reconstruction. In addition, we develop a practical method for detecting reconstruction failures when the scene density exceeds the level for which the array was designed, so that false images are not produced. As a demonstration of its viability, the architecture is used to reconstruct a simulated natural scene.National Science Foundation (U.S.) (Grant CCF-1017772)Semiconductor Research Corporation. Center for Circuits and Systems SolutionsUnited States. Air Force (Contract FA8721-05-C-0002
- …