Molecular simulation analysis of structural variations in lipoplexes

We use a coarse-grained molecular model to study the self-assembly process of complexes of cationic and neutral lipids with DNA molecules ("lipoplexes") - a promising nonviral carrier of DNA for gene therapy. We identify the resulting structures through direct visualization of the molecular arrangements and through calculations of the corresponding scattering plots. The latter approach provides a means for comparison with published data from X-ray scattering experiments. Consistent with experimental results, we find that upon increasing the stiffness of the lipid material, the system tends to form lamellar structures. Two characteristic distances can be extracted from the scattering plots of lamellar complexes - the lamellar (interlayer) spacing and the DNA-spacing within each layer. We find a remarkable agreement between the computed values of these two quantities and the experimental data [J. O. R\"{a}dler, I. Koltover, T. Salditt and C. R. Safinya, Science Vol. 275, 810 (1997)] over the entire range of mole fractions of charged lipids (CLs) studied experimentally. A visual inspection of the simulated systems reveals that, for very high fractions of CLs, disordered structures consisting of DNA molecules bound to small membrane fragments are spontaneously formed. The diffraction plots of these non-lamellar disordered complexes appear very similar to that of the lamellar structure, which makes the interpretation of the X-ray data ambiguous. The loss of lamellar order may be the origin of the observed increase in the efficiency of lipoplexes as gene delivery vectors at high charge densities.Comment: Accepted for publication in "Soft Matter

Fisheries Management with Multiple Market Failures

Within fisheries it is well-known that several market failures exist. However, fisheries economists analyse these market failures separately despite the fact that the market failures arise simultaneously. In this paper several market fail-ures that arise simultaneously are analysed. A resource stock tax and a tax on self-reported harvest are considered as a solution to problems associated with the stock externality, measuring individual catches and stock uncertainty. Within a fisheries economic model it is shown that it will be in the interest of risk-averse fishermen to report a part of their catch even without a control pol-icy. In addition, it is shown that this tax structure can secure optimal expected individual catches and simulations show that the tax payment is very low. Thus, the tax system may be useful in practical fisheries management.Prices regulation, Quantity regulation, Asymmetric Information, Self-Reporting, Stock Tax and Harvest Tax

Regulation of Renewable Resources in Federal Systems: The Case of Fishery in th EU

The EU regulation of fisheries is decided in two levels. The level of the total allowable catch (TAC) for the most important species is decided every year by the Council of Minsters. The TACs are allocated to the Member States as quotas. The Member States determine who is going to harvest the quota. There is, however, an information problem associated with this structure. It does not take into account how efficient fishermen in different countries are. In this paper we model the information problem as an adverse selection problem and analyse an EU tax coupled to effort as an alternative to the TAC system. We work with the hypothesis that EU suffers from a fiscal illusion and includes tax revenue in the objective function in order to finance other, also inefficient, operations. Even in the light of these imperfections there are at least two reasons for recommending an EU tax. First, it can be used to correct part of the market failure associated with fishery. Second, it can be used to secure correct revealation of types in the light of asymmetric information.

Moral Hazard Problems in Fisheries Regulation: The Case og Illegal Landings

This paper treats illegal landings as a moral hazard problem that arises, since individual catches are unobservable to society and hence private information. A tax/subsidy mechanism taking into account the asymmetric information problem is formulated as a solution to problems with illegal landings. The incentive scheme uses fish stock size as the tax variable, and can be seen as an alternative to a control policy. Rough estimates from a simulation study suggest that the incentive scheme is potentially useful. The incentive scheme also has potential application as an instrument to the solution of by-catch and discard problems.

MANAGEMENT OF FISHERIES IN THE EU: A PRINCIPAL-AGENT ANALYSIS

In this paper, an EU tax on fishing effort is studied as an alternative to the system of Total Allowable Catches (TACs). The analysis is conducted under imperfect information, and the hypothesis adopted is that the EU lacks information about the costs of individual fishermen. In light of this imperfection, there are at least two reasons for considering an EU tax. First, it can be used to correct part of the market failure associated with fisheries. Second, it can be used to secure correct revelation of fishermen types in light of asymmetric information.Resource /Energy Economics and Policy,

Hyperradiance from Soliton Oscillators Synchronized by Capacitive or Inducitve Coupling

The output power from coupled Josephson oscillators is investigated when the junctions are operated in their single fluxon mode. We demonstrate that both inductive and capacitive coupling mechanisms can give rise to hyperradiance when the power is coupled out through a boundary resistor. Analytical expressions are derived from adiabatic perturbation theory and excellent agreement is found between the analytical expression and numerical simulations