Action of chlorine on cyanide of mercury

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Action of chlorine on cyanide of mercury

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The Kondo-Hubbard model at half-filling

We have analyzed the antiferromagnetic (J>0) Kondo-Hubbard lattice with the band at half-filling by means of a perturbative approach in the strong coupling limit, the small parameter is an arbitrary tight-binding band. The results are valid for any band shape and any dimension. We have obtained the energies of elementary charge and spin excitations as well as the magnetic correlations in order to elucidate the magnetic and charge behavior of the Kondo lattice at half-filling. Finally, we have briefly analyzed the ferromagnetic case (J<0), which is shown to be equivalent to an effective antiferromagnetic Heisenberg model.Comment: 4 pages, Proceedings of SCES98/Pari

Endothelial Cx40 limits myocardial ischaemia/reperfusion injury in mice

Aims Gap junctions are indispensable for the function of heart and blood vessels by providing electrical coupling and direct cell-to-cell transfer of small signalling molecules. Gap junction channels between neighbouring cells are composed of 12 connexins (Cx). Changes in Cx43 expression, localization, and channel properties in cardiomyocytes contribute to infarction and reperfusion injury of the heart. It is increasingly recognized that deleterious consequences of ischaemia/reperfusion (IR) are modulated by the inflammatory response and endothelial function. The role of the endothelial connexins, i.e. Cx40 and Cx37, in cardiac IR injury is, however, not known. Methods and results Following 30 min ischaemia and 24 h reperfusion, we found a significant increase in myocardial infarct size in mice with endothelial-specific deletion of Cx40 (Cx40del), but not in Cx37-deficient mice. The cardioprotective effect of endothelial Cx40 was associated with a decrease in neutrophil infiltration. Moreover, beneficial effects of endothelial Cx40 were not observed in isolated Langendorff-perfused hearts, suggesting direct involvement of endothelial-leucocyte interactions in the cardiac injury. Single-dose administration of methotrexate, a CD73 activator, reduced infarct size and neutrophil infiltration into the infarcted myocardium in Cx40del but not in control mice. Similar to Cx40del mice, CD73-deficient mice showed increased sensitivity to cardiac IR injury, which could not be conversed by methotrexate. Conclusion Endothelial Cx40, but not Cx37, is implicated in resistance of the heart to IR injury by activation of the CD73 pathway. Thus, the Cx40-CD73 axis may represent an interesting target for controlling reperfusion damage associated with revascularization in coronary diseas

Intermediate coupling fixed point study in the overscreened regime of generalized multichannel SU(N) Kondo models

We study a generalized multichannel single-impurity Kondo model, in which the impurity spin is described by a representation of the SU(N) group which combines bosonic and fermionic degrees of freedom. The impurity spin states are described by Abrikosov pseudofermions, and we make use of a method initiated by Popov and Fedotov which allows a proper handling of the fermionic constraint. The partition function is derived within a path integral approach. We use renormalization group techniques to calculate the $\beta$ scaling function perturbatively in powers of the Kondo coupling constant, which is justified in the weak coupling limit. The truncated expansion is valid in the overscreened (Nozieres-Blandin) regime, for an arbitrary SU(N) group and any value of the parameters characterizing the impurity spin representation. The intermediate coupling fixed point is identified. We derive the temperature dependence of various physical quantities at low T, controlled by a unique critical exponent, and show that the physics of the system in the overscreened regime governed by the intermediate coupling fixed point is characterized by a non-Fermi liquid behavior. Our results are in accordance with those obtained by other methods, as Bethe ansatz and boundary conformal field theory, in the case of various impurity spin symmetries. We establish in a unified way that the Kondo models in which the impurity spin is described successively by a fundamental, symmetric, antisymmetric and mixed symmetry representation yield all the same low-energy physics in the overscreened regime. Possible generalizations of the analysis we present to the case of arbitrary impurity spin representations of SU(N) are also discussed.Comment: 21 pages, 7 figures, REVTeX; final version accepted for publicatio

Iron bioavailability in two commercial cultivars of wheat: a comparison between wholegrain and white flour and the effects of nicotianamine and 2'-deoxymugineic acid on iron uptake into Caco-2 cells

Iron bioavailability in unleavened white and wholegrain bread made from two commercial wheat varieties was assessed by measuring ferritin production in Caco-2 cells. The breads were subjected to simulated gastrointestinal digestion and the digests applied to the Caco-2 cells. Although Riband grain contained a lower iron concentration than Rialto, iron bioavailability was higher. No iron was taken up by the cells from white bread made from Rialto flour or from wholegrain bread from either variety, but Riband white bread produced a small ferritin response. The results probably relate to differences in phytate content of the breads, although iron in soluble monoferric phytate was demonstrated to be bioavailable in the cell model. Nicotianamine, an iron chelator in plants involved in iron transport, was a more potent enhancer of iron uptake into Caco-2 cells than ascorbic acid or 2'-deoxymugineic acid, another metal chelator present in plants

Is international agricultural research a global public good? : The case of rice biofortification

The status of international agricultural research as a global public good (GPG) has been widely accepted since the Green Revolution of the 1960s and 1970s. While the term was not used at the time of its creation, the Consultative Group on International Agricultural Research (CGIAR) system that evolved at that time has been described as a 'prime example of the promise, performance and perils of an international approach to providing GPGs'. Contemporary literature on international agricultural research as a GPG tends to support this view and focuses on how to operationalize the concept. This paper adopts a different starting point and questions this conceptualization of the CGIAR and its outputs. It questions the appropriateness of such a 'neutral' concept to a system born of the imperatives of Cold War geopolitics, and shaped by a history of attempts to secure its relevance in a changing world. This paper draws on a multi-sited, ethnographic study of a research effort highlighted by the CGIAR as an exemplar of GPG-oriented research. Behind the ubiquitous language of GPGs, 'partnership' and 'consensus', however, new forms of exclusion and restriction are emerging within everyday practice, reproducing North-South inequalities and undermining the ability of these programmes to respond to the needs of projected beneficiaries

Ginzburg-Landau functional for nearly antiferromagnetic perfect and disordered Kondo lattices

Interplay between Kondo effect and trends to antiferromagnetic and spin glass ordering in perfect and disordered bipartite Kondo lattices is considered. Ginzburg-Landau equation is derived from the microscopic effective action written in three mode representation (Kondo screening, antiferromagnetic correlations and spin liquid correlations). The problem of local constraint is resolved by means of Popov-Fedotov representation for localized spin operators. It is shown that the Kondo screening enhances the trend to a spin liquid crossover and suppresses antiferromagnetic ordering in perfect Kondo lattices and spin glass ordering in doped Kondo lattices. The modified Doniach's diagram is constructed, and possibilities of going beyond the mean field approximation are discussed.Comment: 18 pages, RevTeX, 7 EPS figures include

Seed systems smallholder farmers use

Seed can be an important entry point for promoting productivity, nutrition and resilience among smallholder farmers. While investments have primarily focused on strengthening the formal sector, this article documents the degree to which the informal sector remains the core for seed acquisition, especially in Africa. Conclusions drawn from a uniquely comprehensive data set, 9660 observations across six countries and covering 40 crops, show that farmers access 90.2 % of their seed from informal systems with 50.9 % of that deriving from local markets. Further, 55 % of seed is paid for by cash, indicating that smallholders are already making important investments in this arena. Targeted interventions are proposed for rendering formal and informal seed sector more smallholder-responsive and for scaling up positive impacts

Food biofortification : reaping the benefits of science to overcome hidden hunger

Biofortification is a process of increasing the density of minerals and vitamins in a food crop through conventional plant breeding, genetic engineering, or agronomic practices (primarily use of fertilizers and foliar sprays). Biofortified staple food crops, when substituted consistently for non-biofortified staple food crops, can generate measurable improvements in human nutrition and health. This monograph describes the progress made in developing, testing, and disseminating biofortified staple food crops, primarily through the use of conventional plant breeding, summarizing the activities of two consortiums of inter-disciplinary collaborating institutions led the HarvestPlus program and the International Potato Center (CIP). We focus on laying out the evidence base proving the effectiveness and impact to date of biofortified crops. Results of a large number of nutritional bioavailability and efficacy trials are summarized (Chapter 2), crop development techniques and activities are presented and variety releases documented for a dozen staple food crops in low and middle income countries (LMICs) in Africa, Asia, and Latin America (Chapter 3), and strategies for promoting the uptake of specific biofortified crops are discussed, concurrent with policy advocacy to encourage key institutions to mainstream the promotion, and use of biofortified crops in their core activities (Chapters 4 and 5). Statistics will be presented on numbers of farm households adopting biofortified crops (Chapters 3 and 4), now available to farmers in 40 low and middle income countries (LMICs). Each section will outline the way forward on additional future activities required to enhance the development and impact the biofortification through conventional plant breeding. No biofortified staple food crop developed through transgenic techniques has been fully de-regulated for release to farmers in LMICs. Yet transgenic techniques hold the potential for a several-fold increase in the impact/benefits of biofortified crops. This potential is described in Chapter 6 which discusses developmental research already completed, including achieving higher densities of single nutrients than is possible with conventional breeding, combining multiple nutrient traits in single events, slowing down/reducing the level of degradation of vitamins after harvesting, and combining superior agronomic traits with nutrient traits in single events. A final chapter summarizes and discusses key questions and issues that will influence the ultimate mainstreaming of biofortified crops in food systems in LMICs and will allow maximization of the benefits of biofortification