Attitudes toward Uncertainty among the Poor: Evidence from Rural Ethiopia

We looked at risk and ambiguity attitudes among Ethiopian peasants in one of the poorest regions of the world and compared their attitudes to a standard Western university student sample elicited by the same decision task. Strong risk aversion and ambiguity aversion were found with the Ethiopian peasants. Ambiguity aversion was similar for peasants and students, but peasants were more risk averse. Testing for the effect of socio-economic variables on uncertainty attitudes showed that poor health increased both risk and ambiguity aversion.risk attitudes, ambiguity attitudes, poverty, cultural differences

Relative Contribution of Proprioceptive and Vestibular Sensory Systems to Locomotion: Opportunities for Discovery in the Age of Molecular Science

Locomotion is a fundamental animal behavior required for survival and has been the subject of neuroscience research for centuries. In terrestrial mammals, the rhythmic and coordinated leg movements during locomotion are controlled by a combination of interconnected neurons in the spinal cord, referred as to the central pattern generator, and sensory feedback from the segmental somatosensory system and supraspinal centers such as the vestibular system. How segmental somatosensory and the vestibular systems work in parallel to enable terrestrial mammals to locomote in a natural environment is still relatively obscure. In this review, we first briefly describe what is known about how the two sensory systems control locomotion and use this information to formulate a hypothesis that the weight of the role of segmental feedback is less important at slower speeds but increases at higher speeds, whereas the weight of the role of vestibular system has the opposite relation. The new avenues presented by the latest developments in molecular sciences using the mouse as the model system allow the direct testing of the hypothesis

Dual -1 Hahn polynomials and perfect state transfer

We find all the $XX$ spin chains with perfect state transfer (PST) that are connected with the dual -1 Hahn polynomials $R_n(x; \alpha,\beta,N)$. For $N$ odd we recover a model that had already been identified while for $N$ even, we obtain a new system exhibiting PST.Comment: 11 page

Spinal microcircuits comprising dI3 interneurons are necessary for motor functional recovery following spinal cord transection

The spinal cord has the capacity to coordinate motor activities such as locomotion. Following spinal transection, functional activity can be regained, to a degree, following motor training. To identify microcircuits involved in this recovery, we studied a population of mouse spinal interneurons known to receive direct afferent inputs and project to intermediate and ventral regions of the spinal cord. We demonstrate that while dI3 interneurons are not necessary for normal locomotor activity, locomotor circuits rhythmically inhibit them and dI3 interneurons can activate these circuits. Removing dI3 interneurons from spinal microcircuits by eliminating their synaptic transmission left locomotion more or less unchanged, but abolished functional recovery, indicating that dI3 interneurons are a necessary cellular substrate for motor system plasticity following transection. We suggest that dI3 interneurons compare inputs from locomotor circuits with sensory afferent inputs to compute sensory prediction errors that then modify locomotor circuits to effect motor recovery

Model validation for a noninvasive arterial stenosis detection problem

Copyright @ 2013 American Institute of Mathematical SciencesA current thrust in medical research is the development of a non-invasive method for detection, localization, and characterization of an arterial stenosis (a blockage or partial blockage in an artery). A method has been proposed to detect shear waves in the chest cavity which have been generated by disturbances in the blood flow resulting from a stenosis. In order to develop this methodology further, we use both one-dimensional pressure and shear wave experimental data from novel acoustic phantoms to validate corresponding viscoelastic mathematical models, which were developed in a concept paper [8] and refined herein. We estimate model parameters which give a good fit (in a sense to be precisely defined) to the experimental data, and use asymptotic error theory to provide confidence intervals for parameter estimates. Finally, since a robust error model is necessary for accurate parameter estimates and confidence analysis, we include a comparison of absolute and relative models for measurement error.The National Institute of Allergy and Infectious Diseases, the Air Force Office of Scientific Research, the Deopartment of Education and the Engineering and Physical Sciences Research Council (EPSRC)

Forecasting stylised features of electricity prices in the Australian National Electricity Market

This thesis tests whether forecast accuracy improves when models that explicitly capture the stylised features of the Australian National Electricity Market (NEM) are employed to generate predictions. It is believed that by explicitly modelling these features of electricity wholesale spot prices, the accuracy of the price forecast models can be improved when compared to standard alternative. The stylised features identified in data are mean-reversion, sudden short-lived and consecutive jumps and heavy tails. When employing models to capture the stylised features of electricity prices, the models necessarily become more complex and often contain a greater number of parameters which combine to mimic the characteristics observed in the price series. Throughout this thesis an adherence to the principle of parsimony (Makridakis, et al page 609) will be maintained; that is if two models effectively generate the same forecast performance the simpler model will be preferred whether it contains the stylised features or not. This is also known as Occum’s Razor. This investigation is important in terms of a better understanding of what models are more useful has the potential to lead to more accurate price forecasts which may result in less volatility in market prices leading to more efficient markets. Further, by assessing models that capture various stylised features it may be possible to infer the importance of particular features. Given that wholesale prices are a major determinant of how much end users pay for powering their homes and businesses, it is believed that a better understanding of what forecasting models work (and do not) will allow market participants to develop more successful (business) strategies for adjusting supply to meet demand and to assist with the valuation of financial assets as part of risk management. Additionally, a better understanding of the dynamics of electricity prices and its implications for successful forecasting is important for government policy makers, as Government sets the rules that govern the production and distribution of electricity. It is believed that by explicitly modelling the stylised features of electricity wholesale prices, forecast accuracy can be improved upon baseline models commonly used in quantitative finance. This thesis investigates the forecasting ability of two distinct modelling approaches which by construction capture the stylised characteristics of electricity prices. Namely, these are linear continuous time and non-linear modelling methods. The AR-GARCH model is chosen to be the standard approach in forecasting price series (Engle, 2001) and is taken as the benchmark model in this thesis. More specifically, this thesis aims to answer the following research questions: Does the application of continuous-time models in capturing the stylised features of Australian electricity wholesale spot prices improve forecasting ability upon the traditional AR-GARCH model? Does the application of non-linear forecast models in capturing the stylised features of Australian electricity wholesale spot prices improve forecast ability upon traditional AR-GARCH model? The continuous-time models examined in this thesis are; Geometric Brownian Motion (GBM), Mean-Reverting, and Mean-Reverting Jump-Diffusion processes. The inclusion of GBM in this thesis is due to it being the foundation for the Mean-Reverting and Jump-Diffusion models, which are considered in this thesis. Continuous-time models capture some of the main stylised features of electricity prices; Mean-Reverting process captures the mean-reversion (tendency of electricity prices to revert back to its long-term average over time) characteristics of electricity prices whilst Mean-Reverting and Jump-Diffusion process models the sudden jumps prevalent in Australian electricity prices. The models are in order such that each successive model extends the one preceding it. Note that each extension addresses a stylised feature of the data therefore the a priori expectation is that the forecasting performance will improve. The inclusion of the non-linear approach to forecasting Australian electricity prices is performed with the application of a Markov Regime-Switching model and the application of Extreme Value Theory (EVT) into electricity price modelling. The Markov Regime-Switching model is a non-linear modelling tool that is able to capture consecutive spikes prevalent in electricity prices that Mean-Reverting and Jump-Diffusion processes fail to capture. The application of EVT is included in this thesis so that heavy tails present in electricity prices can be adequately captured. Copulas are considered as a unique method that models the dependence structure of data. The forecasts based on the EVT model is built upon the application of Copula functions as these functions model the interdependence of prices within the separate regions of the Australian electricity markets. The models examined in this thesis are: 1. AR(1)-GARCH(1) 2. Geometric Brownian Motion 3. Mean-Reverting Model 4. Mean-Reverting and Jump-Diffusion Model 5. Markov Regime-Switching Model with spike distributions modelled with 6. -Gaussian distribution 7. -Log-Gaussian distribution and, 8. Extreme value Theory and Copula functions Each model under investigation mimics a known characteristic of electricity prices. Comparative performance evaluations of each model investigated in this thesis showed that the benchmark model is providing superior short-term forecasting ability

Role of muscle spindle feedback in regulating muscle activity strength during walking at different speed in mice

Terrestrial animals increase their walking speed by increasing the activity of the extensor muscles. However, the mechanism underlying this speed dependent amplitude modulation is achieved remain obscure. Previous studies have shown that group Ib afferent feedback from Golgi tendon organs that signal force is one of the major regulators of the strength of muscle activity during walking in cats and humans. In contrast, the contribution of group Ia/II afferent feedback from muscle spindle stretch receptors which signal angular displacement of leg joints is unclear. Some studies indicate that group II afferent feedback may be important for amplitude regulation in humans, but the role of muscle spindle feedback in regulation of muscle activity strength in quadrupedal animals is very poorly understood. To examine the role of feedback from muscle spindles, we combined in vivo electrophysiology and motion analysis with mouse genetics and gene delivery with adeno associated virus. We provide evidence that proprioceptive sensory feedback from muscle spindles is important for the regulation of the muscle activity strength and speed dependent amplitude modulation. Furthermore, our data suggest that feedback from the muscle spindles of the ankle extensor muscles, the triceps surae, are the main source for this mechanism. In contrast, muscle spindle feedback from the knee extensor muscles, the quadriceps femoris, has no influence on speed dependent amplitude modulation. We provide evidence that proprioceptive feedback from ankle extensor muscles is critical for regulating muscle activity strength as gait speed increases

application of surface transformation films and nanosphere lithography

Photoelectrochemical (PEC) cells offer the possibility of carbon-neutral solar fuel production through artificial photosynthesis. The pursued design involves technologically advanced III–V semiconductor absorbers coupled via an interfacial film to an electrocatalyst layer. These systems have been prepared by in situ surface transformations in electrochemical environments. High activity nanostructured electrocatalysts are required for an efficiently operating cell, optimized in their optical and electrical properties. We demonstrate that shadow nanosphere lithography (SNL) is an auspicious tool to systematically create three-dimensional electrocatalyst nanostructures on the semiconductor photoelectrode through controlling their morphology and optical properties. First results are demonstrated by means of the photoelectrochemical production of hydrogen on p-type InP photocathodes where hitherto applied photoelectrodeposition and SNL-deposited Rh electrocatalysts are compared based on their J–V and spectroscopic behavior. We show that smaller polystyrene particle masks achieve higher defect nanostructures of rhodium on the photoelectrode which leads to a higher catalytic activity and larger short circuit currents. Structural analyses including HRSEM and the analysis of the photoelectrode surface composition by using photoelectron spectroscopy support and complement the photoelectrochemical observations. The optical performance is further compared to theoretical models of the nanostructured photoelectrodes on light scattering and propagation

Experimental and numerical validation of active flaps for wind turbine blades

An industrial active flap concept for wind turbine rotor blades is validated numerically by means of CFD, as well as experimentally in a wind tunnel environment. This paper presents the numerical and experimental results, as well as a discussion regarding the testing of airfoils equipped with active flaps with a highly loaded aft portion. A conceptual implementation for an offshore wind turbine and the potential for load reduction is shown by means of aeroelastic calculations. The work presented herein is conducted within the frame of the Induflap2 project and is partially funded by the Danish funding board EUDP