Corporate Governance: Theory and Practice

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Coordination and Sustainability of River Observing Activities in the Arctic

To understand and respond to changes in the world’s northern regions, we need a coordinated system of long-term Arctic observations. River networks naturally integrate across landscapes and link the terrestrial and ocean domains. Changes in river discharge reflect changes in the terrestrial water balance, whereas changes in water chemistry are linked to changes in biogeochemical processes and water flow paths. Sustained measurements of river water discharge and water chemistry are therefore essential components of an Arctic observing network. As we strive to establish and sustain long-term observations in the Arctic, these two measurements must be coupled. Although river discharge and chemistry measurements are already coupled to some extent within national boundaries, this is not done in a consistent and coordinated fashion across the pan-Arctic domain. As a consequence, data quality and availability vary widely among regions. International coordination of river discharge and chemistry measurements in the Arctic would be greatly facilitated by formal commitments to maintain a set of core sites and associated measurements that are mutually agreed upon among pan-Arctic nations. Involvement of the agencies currently operating river discharge gauges around the Arctic and establishment of an overarching coordination entity to implement shared protocols, track data quality, and manage data streams would be essential in this endeavor. Focused studies addressing scale-dependent relationships between watershed characteristics and water chemistry, in-stream processes, and estuarine and coastal dynamics are also needed to support interpretation and application of Arctic river observing data as they relate to land and ocean change.Pour comprendre les changements qui s’opèrent dans les régions nordiques du monde et y réagir, nous devons nous doter d’un système coordonné d’observation à long terme dans l’Arctique. Les réseaux fluviaux s’intègrent naturellement dans les paysages et relient le domaine terrestre au domaine océanique. Les changements qui s’exercent dans les réseaux fluviaux sont le reflet des changements dans l’équilibre hydrique terrestre, tandis que les changements qui s’exercent sur l’hydrochimie sont liés aux changements caractérisant les processus biogéochimiques et les parcours d’écoulement de l’eau. Par conséquent, un réseau d’observation arctique devrait essentiellement être assorti de mesures durables d’évacuation des eaux fluviales et d’hydrochimie. Au moment où nous nous efforçons d’établir et de soutenir des observations à long terme dans l’Arctique, ces deux types de mesures doivent être suivies en parallèle. Bien que les mesures de l’évacuation fluviale et les mesures chimiques soient déjà, dans une certaine mesure, suivies en parallèle à l’intérieur des frontières nationales, cela ne se fait pas de manière uniforme et coordonnée à la grandeur du domaine panarctique, et en conséquence, la qualité et la disponi­bilité des données varient beaucoup d’une région à l’autre. La coordination internationale des mesures d’évacuation fluviale et chimiques dans l’Arctique serait grandement facilitée par l’existence d’engagements officiels visant à maintenir une série d’emplacements fondamentaux et de mesures connexes fixées par entente mutuelle au sein des nations panarctiques. La partic­ipation des agences qui gèrent les manomètres d’évacuation fluviale dans l’Arctique et l’établissement d’une entité de coordi­nation générale mettant en oeuvre des protocoles partagés, vérifiant la qualité des données et gérant les flux de données seraient également essentiels. Des études ciblées portant sur les relations influencées par l’échelle entre les caractéristiques du bassin hydrographique et l’hydrochimie, sur les processus s’opérant à l’intérieur des cours d’eau et sur la dynamique des estuaires et des rives s’avèrent également nécessaires pour étayer l’interprétation et l’application des données d’observation fluviale de l’Arctique en matière de changement terrestre et océanique

Pharmacological ablation of the airway smooth muscle layer—Mathematical predictions of functional improvement in asthma

Airway smooth muscle (ASM) plays a major role in acute airway narrowing and reducing ASM thickness is expected to attenuate airway hyper-responsiveness and disease burden. There are two therapeutic approaches to reduce ASM thickness: (a) a direct approach, targeting specific airways, best exemplified by bronchial thermoplasty (BT), which delivers radiofrequency energy to the airway via bronchoscope; and (b) a pharmacological approach, targeting airways more broadly. An example of the less well-established pharmacological approach is the calcium-channel blocker gallopamil which in a clinical trial effectively reduced ASM thickness; other agents may act similarly. In view of established anti-proliferative properties of the macrolide antibiotic azithromycin, we examined its effects in naive mice and report a reduction in ASM thickness of 29% (p <.01). We further considered the potential functional implications of this finding, if it were to extend to humans, by way of a mathematical model of lung function in asthmatic patients which has previously been used to understand the mechanistic action of BT. Predictions show that pharmacological reduction of ASM in all airways of this magnitude would reduce ventilation heterogeneity in asthma, and produce a therapeutic benefit similar to BT. Moreover there are differences in the expected response depending on disease severity, with the pharmacological approach exceeding the benefits provided by BT in more severe disease. Findings provide further proof of concept that pharmacological targeting of ASM thickness will be beneficial and may be facilitated by azithromycin, revealing a new mode of action of an existing agent in respiratory medicine

A new class of integrable diffusion-reaction processes

We consider a process in which there are two types of particles, A and B, on an infinite one-dimensional lattice. The particles hop to their adjacent sites, like the totally asymmetric exclusion process (ASEP), and have also the following interactions: A+B -> B+B and B+A -> B+B, all occur with equal rate. We study this process by imposing four boundary conditions on ASEP master equation. It is shown that this model is integrable, in the sense that its N-particle S-matrix is factorized into a product of two-particle S-matrices and, more importantly, the two-particle S-matrix satisfy quantum Yang-Baxter equation. Using coordinate Bethe-ansatz, the N-particle wavefunctions and the two-particle conditional probabilities are found exactly. Further, by imposing four reasonable physical conditions on two-species diffusion-reaction processes (where the most important ones are the equality of the reaction rates and the conservation of the number of particles in each reaction), we show that among the 4096 types of the interactions which have these properties and can be modeled by a master equation and an appropriate set of boundary conditions, there are only 28 independent interactions which are integrable. We find all these interactions and also their corresponding wave functions. Some of these may be new solutions of quantum Yang-Baxter equation.Comment: LaTex,16 pages, some typos are corrected, will be appeared in Phys. Rev. E (2000

Natural variation in Arabidopsis thaliana reveals shoot ionome, biomass, and gene expression changes as biomarkers for zinc deficiency tolerance

Zinc (Zn) is an essential nutrient for plants, with a crucial role as a cofactor for many enzymes. Approximately one-third of the global arable land area is Zn deficient, leading to reduced crop yield and quality. To improve crop tolerance to Zn deficiency, it is important to understand the mechanisms plants have adopted to tolerate suboptimal Zn supply. In this study, physiological and molecular aspects of traits related to Zn deficiency tolerance were examined in a panel of 19 Arabidopsis thaliana accessions. Accessions showed a larger variation for shoot biomass than for Zn concentration, indicating that they have different requirements for their minimal Zn concentration required for growth. Accessions with a higher tolerance to Zn deficiency showed an increased expression of the Zn deficiency-responsive genes ZIP4 and IRT3 in comparison with Zn deficiency-sensitive accessions. Changes in the shoot ionome, as a result of the Zn treatment of the plants, were used to build a multinomial logistic regression model able to distinguish plants regarding their Zn nutritional status. This set of biomarkers, reflecting the A. thaliana response to Zn deficiency and Zn deficiency tolerance, can be useful for future studies aiming to improve the performance and Zn status of crop plants grown under suboptimal Zn concentrations

Orbital reconstruction and two-dimensional electron gas at the LaAlO3/SrTiO3 interface

Conventional two-dimensional electron gases are realized by engineering the interfaces between semiconducting compounds. In 2004, Ohtomo and Hwang discovered that an electron gas can be also realized at the interface between large gap insulators made of transition metal oxides [1]. This finding has generated considerable efforts to clarify the underlying microscopic mechanism. Of particular interest is the LaAlO3/SrTiO3 system, because it features especially striking properties. High carrier mobility [1], electric field tuneable superconductivity [2] and magnetic effects [3], have been found. Here we show that an orbital reconstruction is underlying the generation of the electron gas at the LaAlO3/SrTiO3 n-type interface. Our results are based on extensive investigations of the electronic properties and of the orbital structure of the interface using X-ray Absorption Spectroscopy. In particular we find that the degeneracy of the Ti 3d states is fully removed, and that the Ti 3dxy levels become the first available states for conducting electrons.Comment: 12 pages, 3 figure