333 research outputs found
Electrokinetic measurements of membrane capacitance and conductance for pancreatic -cells
No full textAuthor Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of IEE for personal use, not for redistribution. The definitive version was published in IEE Proceedings - Nanobiotechnology 152 (2005): 189-193, doi:10.1049/ip-nbt:20050040.Membrane capacitance and membrane conductance values are reported for insulin secreting cells (primary β-cells and INS-1 insulinoma cells) determined using the methods of dielectrophoresis and electrorotation. The membrane capacitance value of 12.57 (± 1.46) mF/m2 obtained for β-cells, and the values 9.96 (± 1.89) mF/m2 to 10.65 (± 2.1) mF/m2 obtained for INS-1 cells, fall within the range expected for mammalian cells. The electrorotation results for the INS-1 cells lead to a value of 36 (± 22) S/m2 for the membrane conductance associated with ion channels, if values in the range 2nS to 3 nS are assumed for the membrane surface conductance. This membrane conductance value falls within the range reported for INS cells obtained using the whole-cell patch-clamp technique. However, the total ‘effective’ membrane conductance value of 601 (± 182) S/m2 obtained for the INS-1 cells by dielectrophoresis is significantly larger (by a factor of around three-fold) than the values obtained by electrorotation. This could result from an increased membrane surface conductance, or increased passive conduction of ions through membrane pores, induced by the larger electric field stresses experienced by cells in the dielectrophoresis experiments.This study was financed by a gift from the Denis Robinson Memorial Fund to RP and NIH grants NCRR RR001395 and DK06984 to PJSS
Nonlinear Production, Abatement, Pollution and Materials Balance Reconsidered
No full textIn the environmental economics literature the standard approach of modeling nonlinear production and abatement processes is to treat waste emissions "simply as another factor of production" (Cropper and Oates 1992). That approach doesn't map the materials flow involved completely and hides, moreover, the exact links between production, residuals generation and abatement. This paper shows that production functions with emissions treated as inputs can be reconstructed as a subsystem of a comprehensive production-cum-abatement technology that is in line with the materials-balance principle. In a simple economy with full regard of the materials flow it also explores the consequences for allocative efficiency and efficiency-restoring taxation of multiple and interdependent residuals generated in the transformation processes of production, abatement and consumption. Finally, the paper demonstrates that efficiency may require setting the emissions tax rate above or below conventionally defined marginal abatement cost if the residual subject to abatement is not the only residual causing pollution.residuals, abatement, pollution, materials balance
Dielectrophoresis: A Review of Applications for Stem Cell Research
No full textDielectrophoresis can discriminate distinct cellular identities in heterogeneous populations, and monitor cell state changes associated with activation and clonal expansion, apoptosis, and necrosis, without the need for biochemical labels. Demonstrated capabilities include the enrichment of haematopoetic stem cells from bone marrow and peripheral blood, and adult stem cells from adipose tissue. Recent research suggests that this technique can predict the ultimate fate of neural stem cells after differentiation before the appearance of specific cell-surface proteins. This review summarises the properties of cells that contribute to their dielectrophoretic behaviour, and their relevance to stem cell research and translational applications.</p
Pricing the Ecosystem and Taxing Ecosystem Services: A General Equilibrium Approach
No full textIn an integrated dynamic general equilibrium model of the economy and the ecosystem humans and wildlife species compete for land and prey biomass. We introduce a competitive allocation mechanism in both submodels such that economic prices and ecosystem prices guide the allocation in the economy and in the ecosystem, respectively. We distinguish the scenarios of an open accessible habitat and a privately owned habitat. In both scenarios efficiency requires different corrective taxes/subsidies to internalize consumption services externalities. In the case of an open access habitat additional sources of inefficiency are the divergence of prices for biomass and land in both subsystems. Finally, we determine values of all components of the ecosystem in an efficient steady state with special emphasis on the role and the interplay of ecosystem and economic prices.land, biomass, ecosystem services
International Carbon Emissions Trading and Strategic Incentives to Subsidize Green Energy
No full textThis paper examines strategic incentives to subsidize green energy in a group of countries that operates an international carbon emissions trading scheme. Welfare-maximizing national governments have the option to discriminate against energy from fossil fuels by subsidizing green energy, although in our model green energy promotion is not efficiency enhancing. The cases of small and large countries turn out to exhibit significantly differences. While small countries refrain from subsidizing green energy and thus implement the efficient allocation, large permit-importing countries subsidize green energy in order to influence the permit price in their favor.emissions trading, black energy, green energy, energy subsidies
On-chip high-speed sorting of micron-sized particles for high-throughput analysis
No full textA new design of particle sorting chip is presented. The device employs a dielectrophoretic gate that deflects particles into one of two microfluidic channels at high speed. The device operates by focussing particles into the central streamline of the main flow channel using dielectrophoretic focussing. At the sorting junction (T- or Y-junction) two sets of electrodes produce a small dielectrophoretic force that pushes the particle into one or other of the outlet channels, where they are carried under the pressure-driven fluid flow to the outlet. For a 40mm wide and high channel, it is shown that 6micron diameter particles can be deflected at a rate of 300particles/s. The principle of a fully automated sorting device is demonstrated by separating fluorescent from non-fluorescent latex beads
Optical particle detection integrated in a dielectrophoretic lab-on-a-chip
No full textThe design and fabrication of a dielectrophoretic "lab-on-a-chip" device for bioparticle processing and counting is presented. The device consists of a multi-layer travelling wave dielectrophoretic electrode array for manipulating particles and/or fluids, micro channels for delivering samples, and optical fibres for counting particles and/or measuring their velocities. Single particles were detected optically using either light scattering or fluorescence emission. The technology described in this work is potentially applicable to a range of particulate diagnostic systems
Flattening the Carbon Extraction Path in Unilateral Cost-Effective Action
No full textInternalizing the global negative externality of carbon emissions requires flattening the extraction path of world fossil energy resources (= world carbon emissions). We consider governments having sign-unconstrained emission taxes at their disposal and seeking to prevent world emissions from exceeding some binding aggregate emission ceiling in the medium term. Such a ceiling policy can be carried out either in full cooperation of all (major) carbon emitting countries or by a sub-global climate coalition. Unilateral action has to cope with carbon leakage and high costs which makes a strong case for choosing a policy that implements the ceiling in a cost-effective way. In a two-country two-period general equilibrium model with a non-renewable fossil-energy resource we characterize the unilateral cost-effective ceiling policy and compare it with its fully cooperative counterpart. We show that with full cooperation there exists a cost-effective ceiling policy in which only first-period emissions are taxed at a rate that is uniform across countries. In contrast, the cost-effective ceiling policy of a sub-global climate coalition is characterized by emission regulation in both periods. That policy may consist either of positive tax rates in both periods or of negative tax rates (= subsidies) in both periods or of a positive rate in the first and a negative rate in the second period. The share of the total stock of energy resources owned by the sub-global climate coalition turns out to be a decisive determinant of the sign and magnitude of unilateral cost-effective taxes.unilateral climate policy, intertemporal climate policy, non-renewable energy resources, emission taxes
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