The Effect of synchronized inputs at the single neuron level

It is commonly assumed that temporal synchronization of excitatory synaptic inputs onto a single neuron increases its firing rate. We investigate here the role of synaptic synchronization for the leaky integrate-and-fire neuron as well as for a biophysically and anatomically detailed compartmental model of a cortical pyramidal cell. We find that if the number of excitatory inputs, N, is on the same order as the number of fully synchronized inputs necessary to trigger a single action potential, N_t, synchronization always increases the firing rate (for both constant and Poisson-distributed input). However, for large values of N compared to N_t, ''overcrowding'' occurs and temporal synchronization is detrimental to firing frequency. This behavior is caused by the conflicting influence of the low-pass nature of the passive dendritic membrane on the one hand and the refractory period on the other. If both temporal synchronization as well as the fraction of synchronized inputs (Murthy and Fetz 1993) is varied, synchronization is only advantageous if either N or the average input frequency, ƒ(in), are small enough

Rapid Fabrication of Carbide Matrix/Carbon Fiber Composites

Composites of zirconium carbide matrix material reinforced with carbon fibers can be fabricated relatively rapidly in a process that includes a melt infiltration step. Heretofore, these and other ceramic matrix composites have been made in a chemical vapor infiltration (CVI) process that takes months. The finished products of the CVI process are highly porous and cannot withstand temperatures above 3,000 F (approx.1,600 C). In contrast, the melt-infiltration-based process takes only a few days, and the composite products are more nearly fully dense and have withstood temperatures as high as 4,350 F (approx.2,400 C) in a highly oxidizing thrust chamber environment. Moreover, because the melt- infiltration-based process takes much less time, the finished products are expected to cost much less. Fabrication begins with the preparation of a carbon fiber preform that, typically, is of the size and shape of a part to be fabricated. By use of low-temperature ultraviolet-enhanced chemical vapor deposition, the carbon fibers in the preform are coated with one or more interfacial material(s), which could include oxides. The interfacial material helps to protect the fibers against chemical attack during the remainder of the fabrication process and against oxidation during subsequent use; it also enables slippage between the fibers and the matrix material, thereby helping to deflect cracks and distribute loads. Once the fibers have been coated with the interfacial material, the fiber preform is further infiltrated with a controlled amount of additional carbon, which serves as a reactant for the formation of the carbide matrix material. The next step is melt infiltration. The preform is exposed to molten zirconium, which wicks into the preform, drawn by capillary action. The molten metal fills most of the interstices of the preform and reacts with the added carbon to form the zirconium carbide matrix material. The zirconium does not react with the underlying fibers because they are protected by the interfacial material(s). The success of the melt-infiltration step depends on interface material selection and uniform coating of the fibers, infiltration with the correct amount of carbon, and careful control of temperature and rate of heating

On the “atypical” imperative conjugation in Manda (Bantu N.11).

Peer reviewe

Social Capital and Global Health Indicators: What Trusting Relationships Tell Us About the Global Burden of Disease

This study analyzed the relationship between social capital and global health indicators. Countries from all regions, economic standings, and political models were included (N=58). Epidemiologically a dramatic shift is occurring in the burden of disease. This research attempts to illuminate the complexity of community health and the implications of ignoring social influences on physical health. Previous research has clearly shown the benefits of social capital on health at the individual and communal level and between developed nations, but little study has been given to large-sample, cross-national indicators. Social capital was measured using selected items from the World Values Survey Wave 6 (2010-2014). Global health indicators were obtained from the World Bank Databank and include but are not limited to life expectancy, mortality rates, suicide rates, and prevalence of smoking, overweight, and diabetes. Regression models were applied to test the hypotheses that global health indicators are affected by social capital. At the time of printing, the results were pending. The findings will be applicable to understanding the dynamic pathways of health, in designing public health interventions, and in recognizing the potential for social capital to improve global health. Future research should explore to what extent this relationship exists longitudinally, examine the mechanism of this relationship, and investigate how to increase social capital to improve public health outcomes

Statistical Gaussian Model of Image Regions in Stochastic Watershed Segmentation

International audienceStochastic watershed is an image segmentation technique based on mathematical morphology which produces a probability density function of image contours. Estimated probabilities depend mainly on local distances between pixels. This paper introduces a variant of stochastic watershed where the probabilities of contours are computed from a Gaussian model of image regions. In this framework, the basic ingredient is the distance between pairs of regions, hence a distance between normal distributions. Hence several alternatives of statistical distances for normal distributions are compared, namely Bhattacharyya distance, Hellinger metric distance and Wasserstein metric distance

The grammaticalization of -kotok- into a negative marker in Manda (Bantu N.11)

Peer reviewe

Lazima in Swahili and Beyond: Accounting for the Double Transfer of a Strong Necessity Marker in East Africa

In this study I explore the transfer and further adaptation of Arabic lazima, first into Swahili and its many varieties and then from Swahili into several local language varieties spoken in East Africa. Establishing the function of lazima as a modal marker, used for conveying strong necessity, I examine the various structural and semantic types of integration that lazima has been exposed to. In this pursuit, the investigation contributes both to the growing interest in studies on modality and the influence of Swahili in this area. Drawing on a wide range of Swahili varieties and Swahilized varieties, the analysis challenges the traditional understanding of lazima as a nominal form confined to a superordinate copula clause and as only operating on predicate verbs inflected in dependent and/or non-indicative forms. I argue that there are structural, interactional and ultimately socio-cognitive and socio-historical reasons behind the introduction of this linguistic element in the East African region, where lazima in some local languages even seems to serve as the sole marker of strong necessity, or even of necessity more generally, in a particular semantic domain

Traceability in Legal Pharmaceutical Supply Chains - ensuring safety and quality of prescribed medicinal products

The legal pharmaceutical supply chains are today facing an increasing problem with counterfeit medicines worldwide. There are many documented cases where consumers have taken counterfeit medicines resulting in permanent injuries and even deaths. Supply chain traceability is fundamental to enable verification of authenticity for pharmaceutical products and to prevent counterfeit products to reach end consumers. The traceability is highly dependent on the supply chain actors' ability to share information. It is therefore of interest to study the information sharing in legal pharmaceutical supply chains to ensure safety and quality of medicinal products. The purpose of this master thesis is partly to present a framework to ensure safety of prescribed medicinal products in legal pharmaceutical supply chains. The aim is also to identify mandatory and voluntary information attributes that comply with legal and industrial safety requirements on information sharing. To fulfill the aim a case study was conducted. Multiple sources of data was collected; a survey, semi-structured interviews and internal documents. Eight companies and the Medical Products Agency, MPA participated in the case study. It was found that there is today no standard for identifying products in the studied supply chain and a variety of technologies and standards are used for exchanging data. Another finding was that the companies in the Swedish pharmaceutical supply chain are in harmony with the legislation provided by the MPA. The empirical findings were analyzed together with theory to identify important areas of improvement for enhancing the traceability, and thereby also the safety of medical products, in the pharmaceutical supply chain. The identified components for enhanced traceability are unique identification, standardized data carrier, standardized communication and guidelines for what information to share. These are visualized in the framework TracePharma. The theoretical contributions from this thesis are a comparison of published traceability frameworks within the food industry, and that the components identified in TracePharma can act as a starting point for further research. The practical implications are that the members of the pharmaceutical industry are provided with insight and understanding about how to improve the supply chain traceability and product safety. TracePharma can also be practically used for other supply chains, for example in other industries

Consequences of converting graded to action potentials upon neural information coding and energy efficiency

Information is encoded in neural circuits using both graded and action potentials, converting between them within single neurons and successive processing layers. This conversion is accompanied by information loss and a drop in energy efficiency. We investigate the biophysical causes of this loss of information and efficiency by comparing spiking neuron models, containing stochastic voltage-gated Na+ and K+ channels, with generator potential and graded potential models lacking voltage-gated Na+ channels. We identify three causes of information loss in the generator potential that are the by-product of action potential generation: (1) the voltage-gated Na+ channels necessary for action potential generation increase intrinsic noise and (2) introduce non-linearities, and (3) the finite duration of the action potential creates a ‘footprint’ in the generator potential that obscures incoming signals. These three processes reduce information rates by ~50% in generator potentials, to ~3 times that of spike trains. Both generator potentials and graded potentials consume almost an order of magnitude less energy per second than spike trains. Because of the lower information rates of generator potentials they are substantially less energy efficient than graded potentials. However, both are an order of magnitude more efficient than spike trains due to the higher energy costs and low information content of spikes, emphasizing that there is a two-fold cost of converting analogue to digital; information loss and cost inflation

The negative existential in Bantu

Peer reviewe