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

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

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

Peer reviewe

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

Peer reviewe

The negative existential in Bantu

Peer reviewe

Post-verbal negative particles in Southern Tanzania : form, distribution and historical development

Peer reviewe

Modal auxiliary verb constructions in East African Bantu languages

In this article we offer an overview of the use of modal auxiliary verb constructions in East African Bantu (encompassing languages spoken from eastern Congo in the north-west to northern Mozambique in the south-east; viz. Guthrie zones JD, JE, F, G, M, N and P). Modality, here conceptualized as a semantic space comprising different subcategories (or flavors) of possibility and necessity, has traditionally been a neglected category within Bantu linguistics, which has tended to focus instead on the more grammatical(ized) categories of tense, aspect and to a lesser extent mood. Nonetheless, our survey shows that there exists a rich number of different verbs with specialized modal functions in East African Bantu. Moreover, when comparing the variety of modal verbs in East African Bantu and the wider constructions in which they operate, many similar patterns arise. In some cases, different languages make use of cognate verbs for expressing similar modal concepts, in other cases divergent verbs, but with essentially the same source meaning(s), are employed. In addition, both Bantu-internal and Bantu-external contact have played a key role in the formation of several of the languages’ inventories of modal verbs. A typologically significant feature recurrently discovered among the languages surveyed is the tendency of structural manipulations of the same verb base to indicate semantic shift from participant-internal to participant-imposed modal flavors.In this article we offer an overview of the use of modal auxiliary verb constructions in East African Bantu (encompassing languages spoken from eastern Congo in the north-west to northern Mozambique in the south-east; viz. Guthrie zones JD, JE, E, F, G, M, N and P). Modality, here conceptualized as a semantic space comprising different subcategories (or flavors) of possibility and necessity, has traditionally been a neglected category within Bantu linguistics, which has tended to focus instead on the more grammatical(ized) categories of tense, aspect and to a lesser extent mood. Nonetheless, our survey shows that there exists a rich number of different verbs with specialized modal functions in East African Bantu. Moreover, when comparing the variety of modal verbs in East African Bantu and the wider constructions in which they operate, many similar patterns arise. In some cases, different languages make use of cognate verbs for expressing similar modal concepts, in other cases divergent verbs, but with essentially the same source meaning(s), are employed. In addition, both Bantu-internal and Bantu-external contact have played a key role in the formation of several of the languages’ inventories of modal verbs. A typologically significant feature recurrently discovered among the languages surveyed is the tendency of structural manipulations of the same verb base to indicate semantic shift from participant-internal to participant-imposed modal flavors.Peer reviewe

Post-verbal negative particles in Southern Tanzania : form, distribution and historical development

Peer reviewe

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

Reliability of Lead-Free Solder Joints Under Combined Shear and Compressive Loads

In electronic assemblies, solder joints are used to create electrical connections, remove heat, and mechanically support the components. When an electronic device is powered on, the solder joints and the board they are attached to heat up, expanding at different rates. Due to the difference in expansion, shear stress is imposed on the solder joints. As the device is powered on and off, this shear stress can eventually fracture the solder joint, causing the device to fail. Therefore, to increase the lifespan of electronics, it is important to investigate the mechanical properties of solder alloys. The present study investigates how the SAC 305 solder alloy (96.5% Tin, 3% Silver, 0.5% Copper) degrades under simultaneous compressive loading and shear cycling. The effect of compressive load on solder joint life has not been systematically studied in prior work but is critical to understand as large heat sinks are bolted onto increasingly large electronic assemblies, adding compressive stress on solder joints. To gather data, we constructed a custom shear tester. Shear loads were applied using a programmable motor. A pulley system applied compressive loads. Tests were conducted on a large number of samples under varying shear and compressive loads. The data showed that, for compressive loads below 30N, increasing the compressive load decreased the rate of damage to the sample. However, at the highest compressive load of 45N, the sample fractured immediately. This suggests that applying small compressive loads to critical components of electronic devices could improve their long-term reliability