CO2 Mitigation: On Methods and Parameters for Comparison of Fossil-Fuel and Biofuel Systems

The replacement of fossil fuels by biofuels could be an important means of reducing net carbon dioxide (CO₂) emission. An estimation of the CO₂ mitigation efficiency of biofuel systems depends on the method and assumptions used. Here, different parameters and methods are discussed for comparing fossil-fuel- and biofuel-based systems. Three parameters are suggested: the monetary cost, the primary energy cost and the biofuel cost of CO₂ mitigation. They are defined as the difference in monetary expenditure, primary energy use and biofuel use between the compared systems, divided by the difference in net CO₂ emission between the systems. Cogeneration and separate production of electricity and heat is then compared using these parameters and the methods of multi-functional products or subtraction. In both methods, either electricity or heat is regarded as the main product and the other is regarded as a by-product. The multi-functional method is preferable due to its transparency as both the main product and the by-product are part of the functional unit. Using heat as the main product illustrates the typical situation that the heat demand limits the use of cogeneration. When comparing systems the output from them should not differ. If the by-product is not fully, cogenerated part of the by-product has to be produced separately. A logical choice for producing this part of the by-product is to use a similar fuel and technology as used for cogeneration.     

Swedish survey on extra structurally abnormal chromosomes in 39 105 consecutive prenatal diagnoses: Prevalence and characterization by fluorescence in situ hybridization

During 7 years (1985–1992), 39 105 consecutive prenatal diagnoses (34 908 amniocenteses and 4197 chorionic villus samples) were made at the five largest clinical genetic laboratories in Sweden. Thirty-one cases of extra structurally abnormal chromosomes (ESACs) were found, giving a total prevalence of 0·8 per 1000. Twelve ESACs were inherited, 14 were de novo and in five the parental origin was unknown. This gives an estimated prevalence of 0·3–0·4 per 1000 for familial and 0·4–0·5 per 1000 for de novo ESACs. Retrospectively, the ESACs were characterized by fluorescence in situ hybridization (FISH). In nine cases, no material was available for this analysis. In 21 of the remaining 22 cases, the chromosomal origin could be identified by FISH. Seventeen of these (81 per cent) were derived from the acrocentric chromosomes, of which 13 originated from chromosome 15 (62 per cent). The most common ESAC was the inv dup(15) (57 per cent). Two cases were derived from chromosome 22, one from chromosome 14, and one from either chromosome 13 or chromosome 21. The four remaining cases consisted to two i(18p)s and two small ring chromosomes derived from chromosomes 4 and 19, respectively.     

Competition,defense and games between plants

Summary Coexistence of defended and undefended plants may be maintained by herbivory. In the present paper this phenomenon is analyzed by means of evolutionary game theory. The plants in the model play either a defensive or a non-defensive strategy and they interact indirectly: when a plant is grazed its competitive ability decreases, because of this a neighboring plant makes a profit. The solution to the game leads to three qualitatively different cases depending on whether the profit is equal for the two strategies, defended and undefended, or if the profit is higher for one type than for the other. When the results are applied to intea-specific interactions, the model predicts that polymorphic populations should be expected only under certain specific conditions. When the results are applied to inter-specific interactions, the model predicts either stable coexistence, i.e., increased diversity, or a paradoxical situation without increased diversity.Offprint requests to: M. Augner     

Determination of isocyanic acid in air

A method is presented for the determination of isocyanic acid (ICA), HNCO, in air samples as a di-n-butylamine (DBA) derivative. The method is based on sampling in midget impinger flasks containing 10 ml of 0.01 mol l-1 DBA in toluene. Quantification was made using liquid chromatography (LC) and electrospray mass spectrometry (MS) monitoring positive ions. The instrumental detection limit for the LC-MS was 10 fmol of ICA-DBA. ICA was generated by thermal decomposition of urea. A standard solution containing the DBA derivatives of ICA was prepared by collecting the emitted ICA in an impinger flask containing DBA. ICA in the reference solution was characterised by LC and time-of-flight (TOF) MS and quantified by LC chemiluminescent nitrogen detection (LC-CLND). The instrumental detection limit for the LC-CLND was 1 ng of nitrogen. ICA was emitted during thermal degradation of PFU resins and polyurethane (PUR) lacquers, from car metal sheets. ICA was the most dominant isocyanate and in PUR coating up to 8% of the total weight was emitted as ICA and for PFU resins up to 14% was emitted as ICA. When air samples were collected in an iron foundry during casting in sand moulds with furan resins, concentrations of ICA in the range 50-700 micrograms m-3 were found in the working atmosphere.