Impact of agriculture on soil consumption of atmospheric CH4 and a comparison of CH4 and N2O flux in subarctic, temperate and tropical grasslands

Increasing concentrations of methane (CH₄) in the atmosphere are projected to account for about 25% of the net radiative forcing. Biospheric emissions of CH₄ to the atmosphere total approximately 400 Tg C y^-1. An estimated 300 Tg of CH₄-C y^-1 is oxidized in the atmosphere by hydroxyl radicals while about 40 Tg y^-1 remains in the atmosphere. Approximately 40 Tg y^-1 of the atmospheric burden is oxidized in aerobic soils. Research efforts during the past several years have focused on quantifying CH₄ sources while relatively less effort has been directed toward quantifying and understanding the soil sink for atmospheric CH₄. Recent research has demonstrated that land use change, including agricultural use of native forest and grassland systems has decreased the soil sink for atmospheric methane. Some agricultural systems consume atmospheric CH₄ at rates less than 10% of those found in comparable undisturbed soils. While it has been necessary to change land use practices over the past centuries to meet the required production of food and fiber, we need to recognize and account for impacts of land use change on the biogeochemical nutrient cycles in the biosphere. Changes that have ensued in these cycles have and will impact the atmospheric concentrations of CH₄ and N₂O. Since CH₄ and N₂O production and consumption are accomplished by a variety of soil microorganisms, the influence of changing agricultural, forest, and, demographic patterns has been large. Existing management and technological practices may already exist to limit the effect of land use change and agriculture on trace gas fluxes. It is therefore important to understand how management and land use affect trace gas fluxes and to observe the effect of new technology on them. This paper describes the role of aerobic soils in the global CH₄ budget and the impact of agriculture on this soil CH₄ sink. Examples from field studies made across subarctic, temperate and tropical climate gradients in grasslands are used to demonstrate the influence of nutrient cycle perturbations on the soil consumption of atmospheric CH₄ and in increased N₂O emissions. This revised version was published online in August 2006 with corrections to the Cover Date.     

Impedance measurements on some doped MnO2 electrodes in H2SO4 electrolyte

A.c. impedance behaviour of MnO₂ and doped -MnO₂ electrodes in H₂SO₄ medium was assessed with a view to explaining the mechanism of the discharge behaviour of MnO₂ electrodes in 4m H₂SO₄ electrolyte. The electrodes used in this work appear to be intermediate cases of planar and porous electrodes as the angles, , made by the low frequency part with the real axis are found to be in the range (30–60°). The Nyquist plots and the Randle plots tend to reinforce the observation made by Tye that the capacity yield is essentially diffusion controlled. The depression and flattening of semi-circles observed reveals a link with the heterogeneity of the planar electrode and with the porosity of the pitted electrode. The deviation from a 45° angle made by the low frequency part with the real axis may either be explained by the roughness of the electrode surface or the shallow pores on the surface of the electrodes; in other words due to the difference between the apparent and true surface areas. The double layer capacitance values of the electrodes seem to subsume adsorption capacitances and diffusion factors. Hence, the relative increase in magnitude. The electrodes appear to behave like planar electrodes when 10 µF is introduced into the circuit as a parallel capacitance since angles 0 vary between 40–58°. The undoped -MnO₂ electrode, as well as those prepared from Li-MnO₂, Ag-MnO₂, and I.C.8, appear to be planar electrodes.     

Estimating shear properties of walnut wood: a combined experimental and theoretical approach

In this study, several theoretical models to numerically estimate shear properties of orthotropic materials are introduced. These approaches are based on the combination of Hankinson’s empirically derived formula with other empirical and analytical calculations. Next to shear moduli, which are estimated from the elastic moduli and Poisson’s ratios, shear strengths are also estimated from the in-axis strengths. The models are validated by mechanical tests on walnut wood (Juglans regia L.), for which a sufficient data set can be found in literature. The Arcan test is used to estimate the shear moduli, while the shear block test is used to estimate the shear strengths. The results show that the model, which is based on a combined use of Hankinson’s formula and tensor rotation, gives the best estimation of shear moduli as evaluated by the minimum differences to the experimentally obtained results. For the shear strengths, a combination of Hankinson’s formula and Norris’ failure criterion shows the best agreement in comparison to the experimental data. The theoretical calculations may be used for a time efficient estimation of shear modulus and strength in comparison to the very time-consuming experimental estimation.     

Autonomous Magnetic Microrobots by Navigating Gates for Multiple Biomolecules Delivery

The precise delivery of biofunctionalized matters is of great interest from the fundamental and applied viewpoints. In spite of significant progress achieved during the last decade, a parallel and automated isolation and manipulation of rare analyte, and their simultaneous on‐chip separation and trapping, still remain challenging. Here, a universal micromagnet junction for self‐navigating gates of microrobotic particles to deliver the biomolecules to specific sites using a remote magnetic field is described. In the proposed concept, the nonmagnetic gap between the lithographically defined donor and acceptor micromagnets creates a crucial energy barrier to restrict particle gating. It is shown that by carefully designing the geometry of the junctions, it becomes possible to deliver multiple protein‐functionalized carriers in high resolution, as well as MCF‐7 and THP‐1 cells from the mixture, with high fidelity and trap them in individual apartments. Integration of such junctions with magnetophoretic circuitry elements could lead to novel platforms without retrieving for the synchronous digital manipulation of particles/biomolecules in microfluidic multiplex arrays for next‐generation biochips.     

Correction of congenital diaphragmatic hernia in utero IX: fetuses with poor prognosis (liver herniation and low lung-to-head ratio) can be saved by fetoscopic temporary tracheal occlusion

BACKGROUND/PURPOSE: Fetuses with congenital diaphragmatic hernia (CDH) who have a "poor prognosis" with postnatal treatment now can be identified on the basis of liver herniation, early diagnosis (before 25 weeks' gestation) and a low lung-to-head ratio (LHR). Because complete in utero repair proved unsuccessful for this group, the strategy of temporary tracheal occlusion was developed to gradually enlarge the hypoplastic fetal lung. The purpose of this study is to compare the outcome of patients in the poor-prognosis group treated by one of three methods: (1) standard postnatal care, (2) fetal tracheal occlusion via open hysterotomy, and (3) the recently developed video-fetoscopic (Fetendo) technique of tracheal occlusion without hysterotomy. METHODS: In the past 3 years, 34 of 86 fetuses with an isolated left CDH met criteria for the poor-prognosis group. Thirteen families chose postnatal treatment at an extracorporeal membrane oxygenation (ECMO) center, 13 underwent open fetal tracheal occlusion, and eight underwent fetoscopic tracheal occlusion. RESULTS: The survival rate was 38% in the group treated by standard postnatal therapy, 15% in the open tracheal occlusion group, and 75% in the Fetendo group. There were less postoperative pulmonary complications noted in mothers who underwent the Fetendo procedure versus the open tracheal occlusion. All but one Fetendo clip patient had a striking physiological response demonstrated by sonographic enlargement of the small left lung that was documented postnatally by plain radiographs and its subjective appearance during repair of the CDH. In contrast, only 5 of the 13 open tracheal occlusion patients demonstrated lung growth. CONCLUSION: Fetuses with a left CDH who have liver herniation and a low LHR are at high risk of neonatal demise and appear to benefit from temporary tracheal occlusion when performed fetoscopically, but not when performed by open fetal surgery.     

EXAM: a comprehensive environment for the analysis of access control policies

Policy integration and inter-operation is often a crucial requirement when parties with different access control policies need to participate in collaborative applications and coalitions. Such requirement is even more difficult to address for dynamic large-scale collaborations, in which the number of access control policies to analyze and compare can be quite large. An important step in policy integration and inter-operation is to analyze the similarity of policies. Policy similarity can sometimes also be a pre-condition for establishing a collaboration, in that a party may enter a collaboration with another party only if the policies enforced by the other party match or are very close to its own policies. Existing approaches to the problem of analyzing and comparing access control policies are very limited, in that they only deal with some special cases. By recognizing that a suitable approach to the policy analysis and comparison requires combining different approaches, we propose in this paper a comprehensive environment—EXAM. The environment supports various types of analysis query, which we categorize in the paper. A key component of such environment, on which we focus in the paper, is the policy analyzer able to perform several types of analysis. Specifically, our policy analyzer combines the advantages of existing MTBDD-based and SAT-solver-based techniques. Our experimental results, also reported in the paper, demonstrate the efficiency of our analyzer.     

Wherein is Human Cognition Systematic?

The ??systematicity argument?? has been used to argue for a classical cognitive architecture (Fodor in The Language of Thought. Harvester Press, London, 1975, Why there still has to be a language of thought? In Psychosemantics, appendix. MIT Press, Cambridge, pp 135?C154, 1987; Fodor and Pylyshyn in Cognition 28:3?C71, 1988; Aizawa in The systematicity arguments. Kluwer Academic Press, Dordrecht, 2003). From the premises that cognition is systematic and that the best/only explanation of systematicity is compositional structure, it concludes that cognition is to be explained in terms of symbols (in a language of thought) and formal rules. The debate, with connectionism, has mostly centered on the second premise-whether an explanation of systematicity requires compositional structure, which neural networks do not to exhibit (for example, Hadley and Hayward, in Minds and Machines, 7:1?C37). In this paper, I will take issue with the first premise. Several arguments will be deployed that show that cognition is not systematic in general; that, in fact, systematicity seems to be related to language. I will argue that it is just verbal minds that are systematic, and they are so because of the structuring role of language in cognition. A dual-process theory of cognition will be defended as the best explanation of the facts.     

Influence of diameter in the Raman spectra of aligned multi-walled carbon nanotubes

Aligned multi-walled carbon nanotubes (MWCNTs) were produced with different diameters, according to the thickness of Ni catalyst layer, by microwave plasmas enhanced chemical vapor deposition, in N₂/H₂/CH₄ environment. Raman spectroscopy, performed both on top and lateral surfaces, revealed that the relative intensity of the G′ band and the G and G′ bandwidths have high sensitivity to tube diameter distribution and also to structural variations along the tube axis. The D band present a distinct behavior: I_D/I_G is sensitive to structural organization, particularly along tube axis, while D bandwidth is sensitive to tube diameter distribution. This result may indicate D bandwidth as a parameter to correlate to the diameter of the aligned MWCNTs.