Intracortical Neural Probes with Post-Implant Self-Deployed Electrodes for Improved Chronic Stability.

This thesis presents a new class of implantable intracortical neural probe with small recording electrodes that deploy away from a larger main shank after insertion. This concept is hypothesized to enhance the performance of the electrodes in chronic applications. Today, electrodes that can be implanted into the brain for months or years, are an irreplaceable tool for brain machine interfaces and neuroscience studies. However, these chronically implanted neural probes suffer from continuous loss of signal quality, limiting their utility. Histological studies found a sheath of scar tissue with decreased neural density forming around probe shanks as part of an ongoing chronic inflammation. This was hypothesized to contribute to the deterioration of recorded signals. The neural probes developed in this thesis are designed to deploy electrodes outside this sheath such that they interface with healthier neurons. To achieve this, an actuation mechanism based on starch-hydrogel coated microsprings was integrated into the shank of neural probes. Recording electrodes were positioned at the tip of micrometer fine and flexible needles that were attached to the springs. Before insertion, the hydrogel dehydrates, retracting the springs. After insertion, the gel rehydrates, releasing the springs, which then deploy the electrodes. The actuation mechanism functions in a one-time release fashion, triggered by contact with biological fluids at body temperature. The deployment of the electrodes occurred over the course of two hours and can be divided into three stages: For the first 20 s, the electrodes did not deploy. Within the first three minutes they deployed by roughly 100 µm (0.5 µm/s). Tor the following two hours they deployed an additional 20 µm (0.17 µm/min). The employed design supported six deploying electrodes, each at the end of a 5 µm wide and thick, and 100 µm long needle. These were attached to a shank with 290 µm width, 12 µm thickness and 3 mm length. The shanks could be inserted into the cortex of rats through an opening in the pia without breaking. The acquired waveforms indicate that some of the deployed electrodes were able to record neural action potentials.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/113317/1/egertd_1.pd

Hardy's inequality for functions vanishing on a part of the boundary

We develop a geometric framework for Hardy's inequality on a bounded domain when the functions do vanish only on a closed portion of the boundary.Comment: 26 pages, 2 figures, includes several improvements in Sections 6-8 allowing to relax the assumptions in the main results. Final version published at http://link.springer.com/article/10.1007%2Fs11118-015-9463-

Bitter gourd, Momordica charantia L., breeding lines differ in secondary metabolite content according to market type

Bitter gourd, Momordica charantia L., is an important commercial cucurbitaceous vegetable of enormous medicinal value in Asia because of its secondary metabolite content. We report here the characterization and evaluation of open-pollinated (OP) edible South Asian and Southeast Asian types of bitter gourd breeding lines, developed at the World Vegetable Center, for horticultural traits (11 OP) and secondary metabolites (10 OP) and their comparisons with commercial OP and F1 hybrid cultivars. Marketable yields of South Asian and Southeast Asian type breeding lines were comparable to the OP ‘BARI Karella 1’ and the hybrid ‘Benteng’, respectively.The bitter gourd cultivars and breeding lines included in this study exhibited specific patterns for five secondary metabolites (saponins, carotenoids, chlorophyll a and b, and vitamin C): in general the two cultivars and South Asian type breeding lines contained higher levels of secondary metabolites, e.g. carotenoids, than the Southeast Asian bitter gourd breeding lines.Some of these bitter gourd lines will be released to Asian home and school gardeners after conducting multi-location trials across Asia to improve vegetable consumption as a main task of bitter gourd breeding

Worker remittances and the global preconditions of ‘smart development’

With the growing environmental crisis affecting our globe, ideas to weigh economic or social progress by the ‘energy input’ necessary to achieve it are increasingly gaining acceptance. This question is intriguing and is being dealt with by a growing number of studies, focusing on the environmental price of human progress. Even more intriguing, however, is the question of which factors of social organization contribute to a responsible use of the resources of our planet to achieve a given social result (‘smart development’). In this essay, we present the first systematic study on how migration – or rather, more concretely, received worker remittances per GDP – helps the nations of our globe to enjoy social and economic progress at a relatively small environmental price. We look at the effects of migration on the balance sheets of societal accounting, based on the ‘ecological price’ of the combined performance of democracy, economic growth, gender equality, human development, research and development, and social cohesion. Feminism in power, economic freedom, population density, the UNDP education index as well as the receipt of worker remittances all significantly contribute towards a ‘smart overall development’, while high military expenditures and a high world economic openness are a bottleneck for ‘smart overall development’

Self-Organized Criticality in Developing Neuronal Networks

Recently evidence has accumulated that many neural networks exhibit self-organized criticality. In this state, activity is similar across temporal scales and this is beneficial with respect to information flow. If subcritical, activity can die out, if supercritical epileptiform patterns may occur. Little is known about how developing networks will reach and stabilize criticality. Here we monitor the development between 13 and 95 days in vitro (DIV) of cortical cell cultures (n = 20) and find four different phases, related to their morphological maturation: An initial low-activity state (≈19 DIV) is followed by a supercritical (≈20 DIV) and then a subcritical one (≈36 DIV) until the network finally reaches stable criticality (≈58 DIV). Using network modeling and mathematical analysis we describe the dynamics of the emergent connectivity in such developing systems. Based on physiological observations, the synaptic development in the model is determined by the drive of the neurons to adjust their connectivity for reaching on average firing rate homeostasis. We predict a specific time course for the maturation of inhibition, with strong onset and delayed pruning, and that total synaptic connectivity should be strongly linked to the relative levels of excitation and inhibition. These results demonstrate that the interplay between activity and connectivity guides developing networks into criticality suggesting that this may be a generic and stable state of many networks in vivo and in vitro