REBUILDING THE EASTERN BALTIC COD STOCK UNDER ENVIRONMENTAL CHANGE (PART II): TAKING INTO ACCOUNT THE COSTS OF A MARINE PROTECTED AREA

Abstract This study adds a cost analysis of the Eastern Baltic cod fishery to the existing model presented in Röckmann et al. [2007a] . As cost data on this international fishery do not exist, data from Denmark are extrapolated to the whole international fishery. Additionally, unit and total variable costs are simulated, and the sensitivity to a set of different cost–stock and cost–output elasticities is tested. The study supports preliminary conclusions that a temporary marine reserve policy, which focuses on protecting the Eastern Baltic cod spawning stock in the International Council for the Exploration of the Sea (ICES) subdivision 25, is a valuable fisheries management tool to (i) rebuild the overexploited Eastern Baltic cod stock and (ii) increase operating profits. The negative effects of climate change can be postponed for at least 20 years—depending on the assumed rate of future climate change. Including costs in the economic analysis does not change the ranking of management policies as proposed in the previous study where costs were neglected.     

REBUILDING THE EASTERN BALTIC COD STOCK UNDER ENVIRONMENTAL CHANGE–A PRELIMINARY APPROACH USING STOCK,ENVIRONMENTAL, AND MANAGEMENT CONSTRAINTS

ABSTRACT. . The population dynamics of the Eastern Baltic cod (Gadus morhua callarias L.), unlike many other stocks, shows a strong dependency on environmental conditions. To test the implications of different management policies on the stock and the fishery in a system of global environmental change, we apply a spatially disaggregated, discrete time, age‐structured model of the Eastern Baltic cod stock in 50 year simulation analyses. The simulation provides an analysis of stock, yield, and revenue development under various management policies and environmental scenarios. The policy analysis, focusing on different regulations of fishing mortality, is embedded into three environmental scenarios, assuming low, medium, or high climate and environmental change. The environmental assumptions are based on simulation results from a coupled atmosphere‐ocean regional climate model, which project salinity in the Baltic Sea to decrease by 7–47% in the period 2071–2100 relative to the reference period 1961 1990. Our simulation results show that a significant reduction in fishing mortality is necessary for achieving high long‐term economic yields. Moreover, under the environmental scenarios presented, a stock collapse cannot be prevented. It can, however, be postponed by the establishment of a marine reserve in ICES subdivision 25.     

Long electron spin memory times in gallium arsenide

Extremely long electron spin memory times in GaAs are reported. It was established by the optical orientation method that the spin relaxation time of electrons localized at shallow donors in n-type gallium arsenide (N _d ?N _A ≈10¹⁴ cm^?3) is 290±30 ns at a temperature of 4.2 K. The exchange interaction of quasi-free electrons and electrons at donors suppresses the main spin-loss channel for electrons localized at donors—spin relaxation due to the hyperfine interaction with lattice nuclei.     

Dependence of optically oriented and detected electron spin resonance on donor concentration in n-GaAs

Electron spin resonance of donors in GaAs has been observed through optical orientation and detection of spins. GaAs samples doped below the metal-insulator transition were studied. The resonance linewidth increases as the concentration of donors is reduced, due to the dependence of the T₂^* spin lifetime on correlation effects between donor electrons. The linewidth of the lowest doped sample (3×10¹⁴ cm⁻³) corresponds to a T₂^* of 5 ns, which is the value predicted for electrons in the non-interacting, localized limit. The nuclei need to be simultaneously depolarized in order to make the electron resonance observable.     

Some topological dynamics properties of discrete-time control systems

This paper is concerned with the study of certain stabilityproperties of discrete-time systems by means of topologicalmethods. It turns out that suitably defined sets guarantee thestability of the reachable sets in the vicinity of compact sets.Furthermore, special properties about affine control systemsare given.     

Nanoporous metal organic framework materials for hydrogen storage

Hydrogen is expected to play an important role in future transportation as a promising alternative clean energy source to carbon-based fuels.One of the key challenges to commercialize hydrogen energy is to develop appropriate onboard hydrogen storage systems,capable of charging and discharging large quantities of hydrogen with fast enough kinetics to meet commercial requirements.Metal organic framework (MOF) is a new type of inorganic and organic hybrid nanoporous particulate materials.Its diverse networks can enhance hydrogen storage through tuning the structure and property of MOFs.The MOF materials so far developed adsorb hydrogen through weak disperston interactions,which allow significant quantity of hydrogen to be stored at cryogenic temperatures with fast kinetics.Novel MOFs are being developed to strengthen the interactions between hydrogen and MOFs in order to store hydrogen under ambient conditions.This review surveys the development of such candidate materials,their performance and future research needs.     

Electronic spectroscopy of NO-(Rg)x complexes (Rg = Ne,Ar) via the 4s and 3d Rydberg states

We have employed (2 + 1) resonance enhanced multiphoton ionization spectroscopy to investigate the 3d and 4s Rydberg states of the NO molecule when bound to the surface of Rg(x) clusters (Rg = rare gas). We observe that the spectra of the NO-Ar(x) species converge in appearance as x increases, and this is discussed in terms of two Rg atoms interacting with the NO+ core, with other Rg atoms being "outside" the Rydberg orbital. We show that the interaction of each of the Rg atoms with the NO is essentially independent for the NO-Rg2 complexes: both by comparing our spectra for Rydberg states of NO-Rg and NO-Rg2, and from the results of ab initio calculations on NO+ - Rg and NO+ - Rg2. In addition, we discuss the disappearance of some electronic bands upon complexation in terms of Franck-Condon factors that are very sensitive to the angular coordinate. We relate our results to those of the bulk by comparing to the previously reported electronic spectroscopy of NO in both Rg matrices and He nanodroplets.