Multi-microelectrode devices for intrafascicular use in peripheral nerve

This minisymposium paper gives an overview of experimental, modeling, design and microfabrication steps which lead towards the University of Twente three-dimensional 128-fold silicon microelectrode device. The device is meant for implantation in peripheral nerve for neuromuscular control purposes and is estimated to be able to selectively control 10-20 motor fibres. Also, the potentialities of an alternative LIGA microfabrication technology are considered. A brief comparison is made with the two-dimensional sieve and flexible foil types of neuro electronic interfaces, under development elsewhere. Microfabrication technologies appear to be an important tool, but evidence is accumulating that for selective neuroelectronic interfacing the micro devices are not yet small/selective enough. More precision and selectivity is needed to contact individual axons intimately and selectively. Therefore, new lines of research develop towards in-vitro-neuron-cultured MEPs (Multi Electrode Plates) to be implanted in neural tissu

The influence of cochlear hearing loss and probe tone level on compound action potential tuning curves in humans

The effect of cochlear hearing loss and of probe tone level on slopes and sharpness of compound action potential tuning curves was investigated. Thirty-one simultaneously masked isoreduction (50%) tuning curves were determined in 26 adults with cochlear hearing losses up to 60 dB. Probe tone frequency was 2 or 3 kHz. Probe tone level was chosen as close as possible to the action potential threshold, usually within 30 dB. In 5 cases a second tuning curve was determined at a 20–30 dB higher probe tone level in order to differentiate between effects of hearing loss and of probe tone level itself on decrease of selectivity. Tuning was analysed in terms of high- and low-frequency slopes of the tuning curves, both in the steepest parts near the tip and overall, and in terms of Q10dB. Slopes and tuning quality diminished with increasing hearing loss up to 60 dB. Part of the decrease in Q10 could be attributed to increased probe tone level, implying that frequency selectivity is also a level-dependent property. In the same group of subjects so called ‘narrow-band’ (or ‘derived response’) compound action potential latencies were determined at 90 dB per SPL and a derived frequency similar to the probe tone in the tuning curve experiments. Narrow band latencies did not change significantly out of the normal range (2 periods) with increasing hearing loss. This implies that narow band latencies are not related to hearing loss, but reflect only the probe-level dependent impulse response delay. Analysis shows that it is possible to derived Q10dB from narrow band latencies with probe level as a parameter

H-alpha features with hot onsets. I. Ellerman bombs

Ellerman bombs are transient brightenings of the wings of the Balmer lines that uniquely mark reconnection in the solar photosphere. They are also bright in strong Ca II and ultraviolet lines and in ultraviolet continua, but they are not visible in the optical continuum and the Na I D and Mg I b lines. These discordant visibilities invalidate all published Ellerman bomb modeling. I argue that the assumption of Saha-Boltzmann lower-level populations is informative to estimate bomb-onset opacities for these diverse diagnostics, even and especially for H-alpha, and employ such estimates to gauge the visibilities of Ellerman bomb onsets in all of them. They constrain Ellerman bomb formation to temperatures 10,000 - 20,000 K and hydrogen densities around 10^15 cm^-3. Similar arguments likely hold for H-alpha visibility in other transient phenomena with hot and dense onsets.Comment: Accepted by Astronomy & Astrophysic

H-alpha features with hot onsets III. Fibrils in Lyman-alpha and with ALMA

In H-alpha most of the solar surface is covered by dense canopies of long opaque fibrils, but predictions for quiet-Sun observations with ALMA have ignored this fact. Comparison with Ly-alpha suggests that the large opacity of H-alpha fibrils is caused by hot precursor events. Application of a recipe that assumes momentary Saha-Boltzmann extinction during their hot onset to millimeter wavelengths suggests that ALMA will observe H-alpha-like fibril canopies, not acoustic shocks underneath, and will yield data more interesting than if these canopies were transparent.Comment: Accepted for Astronomy & Astrophysics; Figure 1 correcte

The quiet chromosphere. Old wisdom, new insights, future needs

The introduction to this review summarizes chromosphere observation in two figures. The first part showcases the historical emphasis on the eclipse chromosphere in the development of NLTE line formation theory and criticizes 1D modeling. The second part advertises recent breakthroughs after many decades of standstill. The third part discusses what may or should come next.Comment: To appear in Proceedings 25th NSO Workshop, editors A. Tritschler, K. Reardon, H. Uitenbroek, Mem. Soc. Astr. Ita

The Economic Impact of Medical Migration: an Overview of the Literature

Despite rapid economic and social development of the Maldives, the vulnerability of the island population in terms of poverty remains high. Using household panel data for the period 1997/98 Ð 2004 we show that, although the majority of the poor manages to escape from poverty, a substantial part of the non-poor falls back into poverty at the same time. Using Logit regression analysis, the most influential determinants of escaping household poverty are shown to be: the level of education, participation in community activities, and the proportion of adults employed. Factors that have the largest impact on impeding a poverty escape are: the proportion of household members not working due to bad health, living in the North, and the proportion of female household members. The former two factors, in addition to household size, are also most influential on the odds of falling into poverty. Working in tourism, or the public sector, and taking out a loan to invest are important factors that prevent households from falling into poverty. Policy implications of these results are not only relevant at government level but also at household level. The government may consider paying more attention to the development of the two Northern regions, improve access to good quality education and health care, and further develop (private sector) tourism across the country. Household coping strategies involve investing in education, entering the labour market (especially in tourism and the public sector) and family planning.medical migration, brain drain, doctor migration, nurse migration

Medical migration : what can we learn from the UK's perspective ?

This paper seeks to determine the macro-economic impacts of migration of skilled medical personnel from a receiving country's perspective. The resource allocation issues are explored in theory, by developing an extension of the Rybczynski theorem in a low-dimension Heckscher-Ohlin framework, and empirically, by developing a static computable general equilibrium model for the United Kingdom with an extended health sector component. Using simple diagrams, an expansion of the health sector by recruiting immigrant skilled workers in certain cases is shown to compare favorably to the (short-term) long-term alternative of using domestic (unskilled) workers. From a formal analysis, changes in non-health outputs are shown to depend on factor-bias and scale effects. The net effects generally are indeterminate. The main finding from the applied model is that importing foreign doctors and nurses into the United Kingdom yields higher overall welfare gains than a generic increase in the National Health Service budget. Welfare gains rise in case of wage protection.Health Monitoring&Evaluation,Health Systems Development&Reform,Labor Markets,Population Policies,Health Economics&Finance

The effectiveness and usefulness for commodity-dependent countries of new tools in commodity markets: risk management and collateralized finance

This paper describes the experiences of developing country enterprises, farmers and governments with commodity price risk management and various forms of structured finance. It explores the constraints that these entities face in using modern financial markets, including counterparty and sovereign risk obstacles, and problems in their legal and regulatory framework. Various schemes to overcome such obstacles are examined.commodity futures market, futures, options, risk management, structured finance, warehouse receipts, securitization

Potential applications of structured commodity financing techniques for banks in developing countries

This paper discusses of a number of innovative financial techniques that can be used by developing country banks to open up new financing possibilities in the commodities sector, for industries servicing the commodity sector, and for financing on the basis of "commoditized" income streams. This includes techniques such as factoring and forfaiting, countertrade, warehouse receipt finance, prepayments, export receivables finance, Islamic finance, structured import finance, and securitization. A number of practical models for developing country banks are described.agricultural finance structured finance repos banks securitization

New types of non-trade related participation in commodity futures markets

This paper explores the growing involvement of new types of non- commodity-sector-related players in commodity futures markets. This includes a discussion on the role of managed funds, the impact of the use of commodity warrants, and the direct involvement of banks. The impact of this new form of "speculation" on the price formation process on commodity futures markets is then examined, and conclusions are drawn as to the use of these markets by commodity sector actors.commodity futures market, futures, options, speculation, market efficiency