Contractual and Relational Governances: Are they Complementary or Substitutable in the Context of Value Chains

Interactions among value chain actors can be governed either through contractual or relational governance mechanisms or through the use of both at the same time. The question of complementarity or substitutability of these two governance mechanisms has already attracted the attentions of researchers nowadays. This essay is the review of selected scientific journals in the area of contractual and relational governance mechanisms. The purpose is to compile the research findings in a way it assists readers to better understand whether contractual and relational governance mechanisms are complementary or substitutable. Keywords: contractual governance, relational governance, complementary, substitutabilit

Stress control of frictional hangingwall accommodation above thrust ramps

Experimental models are used to study the stress control of frictional hangingwall accomodation above rigid flat-ramp-flat footwalls. Hangingwall accommodation involves shear or kink-band nucleation above the lower fault bend and migration of these as the hangingwalls climb over the underthrusting footwall. The kinkbands change shape and localise to thrusts as they migrate over the flat-ramp-flat footwall. When the shear stress to gravity stress ratio is low the thrusts reactivate to normal faults. With increase in the shear stress to gravity stress ratio reactivation of the kink bands was by tensile failure, at the upper fault bend. The models show that by changing the strength of materials deforming under otherwise similar conditions it is possible to study the geometry of frictional hangingwall accommodation, at different scales. In nature, hangingwall accommodation by thrust nucleation above thrust ramps and their subsequent normal reactivation may be anticipated in frictional sediments at shallow crustal levels, where temperatures and pressures are low

A Model for Perimeter-Defense Problems with Heterogeneous Teams

We develop a model of the multi-agent perimeter-defense game to calculate how an adaptive defense should be organized. This model is inspired by the human immune system and captures settings such as heterogeneous teams, limited resource allocations, partial observability of the attacking side, and decentralization. An optimal defense, that minimizes the harm under constraints of the energy spent to maintain a large and diverse repertoire, must maintain coverage of the perimeter from a diverse attacker population. The model characterizes how a defense might take advantage of its ability to respond strongly to attackers of the same type but weakly to attackers of diverse types to minimize the number of diverse defenders and while reducing harm. We first study the model from a steady-state perimeter-defense perspective and then extend it to mobile defenders and evolving attacker distributions. The optimal defender distribution is supported on a discrete set and similarly a Kalman filter obtaining local information is able to track a discrete, sometimes unknown, attacker distribution. Simulation experiments are performed to study the efficacy of the model under different constraints.Comment: 8 pages, 6 figure

The newly developed CRF1-receptor antagonists, NGD 98-2 and NGD 9002, suppress acute stress-induced stimulation of colonic motor function and visceral hypersensitivity in rats.

Corticotropin releasing factor receptor 1 (CRF1) is the key receptor that mediates stress-related body responses. However to date there are no CRF1 antagonists that have shown clinical efficacy in stress-related diseases. We investigated the inhibitory effects of a new generation, topology 2 selective CRF1 antagonists, NGD 98-2 and NGD 9002 on exogenous and endogenous CRF-induced stimulation of colonic function and visceral hypersensitivity to colorectal distension (CRD) in conscious rats. CRF1 antagonists or vehicle were administered orogastrically (og) or subcutaneously (sc) before either intracerebroventricular (icv) or intraperitoneal (ip) injection of CRF (10 µg/kg), exposure to water avoidance stress (WAS, 60 min) or repeated CRD (60 mmHg twice, 10 min on/off at a 30 min interval). Fecal pellet output (FPO), diarrhea and visceromotor responses were monitored. In vehicle (og)-pretreated rats, icv CRF stimulated FPO and induced diarrhea in >50% of rats. NGD 98-2 or NGD 9002 (3, 10 and 30 mg/kg, og) reduced the CRF-induced FPO response with an inhibitory IC50 of 15.7 and 4.3 mg/kg respectively. At the highest dose, og NGD 98-2 or NGD 9002 blocked icv CRF-induced FPO by 67-87% and decreased WAS-induced-FPO by 23-53%. When administered sc, NGD 98-2 or NGD 9002 (30 mg/kg) inhibited icv and ip CRF-induced-FPO. The antagonists also prevented the development of nociceptive hyper-responsivity to repeated CRD. These data demonstrate that topology 2 CRF1 antagonists, NGD 98-2 and NGD 9002, administered orally, prevented icv CRF-induced colonic secretomotor stimulation, reduced acute WAS-induced defecation and blocked the induction of visceral sensitization to repeated CRD

Protocol optimisation for micropropagation of Ethiopian yam

Yam ( Dioscorea spp.) is a monocotyledonous tuber forming tropical vine, which belongs to the family Dioscoreaceae, and genus Dioscorea. Yam is well known for medicinal properties, as well as nutritional values. Conventional propagation of yam is limited by low propagation rates; hence, in vitro propagation provides the best alternative to overcome such limitations. The objective of this study was to optimise a protocol for in vitro micro-propagation of Ethiopian yam ( D. alata , bulcha variety). Explants were obtained from young leaves of bulcha variety, and sterilised using different concentrations of NaOCl, for different time exposures. Sodium hypochlorite (1%) at 15 minutes exposure time, showed 100% survival of explants. The combination of 0.5 BAP with 1mgl-1 NAA was the best concentration for shoot induction. For shoot multiplication, BAP at 1.5 mg l-1 gave the highest shoots per explants (7.28\ub10.07), with shoot length of 8.72\ub10.43 cm. MS medium with 2.0 mg l-1 NAA and 1.5 mg l-1 IBA gave the highest rooting percentage and root number (10.6\ub10.44), with a root length of 13.80\ub10.44. In vitro acclimatised plantlets,which were transferred to a greenhouse for hardening, had 90% survival rate on soil medium. Thus, for micropropagation of bulcha yam variety, MS + 1.5 mg l-1 and MS plus 2.0 mg l-1 NAA + 1.5 mg l-1 IBA is the best phytohormonal combination for shoot multiplication and invitro rooting, respectively.L\u2019igname ( Dioscorea spp.) est un tubercule monocotyl\ue9done qui forme la vigne tropicale, qui appartient \ue0 la famille des Dioscoreaceae et au genre des Dioscorea. L\u2019igname est bien connue pour ses propri\ue9t\ue9s m\ue9dicinales, ainsi que pour ses valeurs nutritionnelles. La propagation conventionnelle de l\u2019igname est limit\ue9e par de faibles taux de propagation; par cons\ue9quent, la propagation in vitro offre la meilleure alternative pour surmonter ces limitations. L\u2019objectif de cette \ue9tude \ue9tait d\u2019optimiser un protocole de micro-propagation in vitro de l\u2019igname Ethiopienne ( D. alata , vari\ue9t\ue9 bulcha). Des explants ont \ue9t\ue9 obtenus \ue0 partir de jeunes feuilles de la vari\ue9t\ue9 bulcha et st\ue9rilis\ue9s en utilisant diff\ue9rentes concentrations de NaOCl, pour des expositions temporelles diff\ue9rentes. L\u2019hypochlorite de sodium (1%) \ue0 un temps d\u2019exposition de 15 minutes a montr\ue9 une survie de 100% des explants. La combinaison de 0,5 BAP avec 1mgl-1 NAA s\u2019est av\ue9r\ue9e \ueatre la meilleure concentration pour l\u2019induction des pousses. Pour la multiplication des pousses, le BAP \ue0 1,5 mg l-1 a donn\ue9 les pousses les plus \ue9lev\ue9es par explants (7,28 \ub1 0,07), avec une longueur de pousses de 8,72 \ub1 0,43 cm. Le milieu MS avec 2,0 mg l-1 NAA et 1,5 mg l-1 IBA a donn\ue9 le pourcentage d\u2019enracinement et le nombre de racines les plus \ue9lev\ue9s (10,6 \ub1 0,44), avec une longueur de racine de 13,80 \ub1 0,44. Les plantules acclimat\ue9es in vitro, qui ont \ue9t\ue9 transf\ue9r\ue9es dans une serre pour durcissement, avaient un taux de survie de 90% sur un milieu de sol. Ainsi, pour la micropropagation de la vari\ue9t\ue9 bulcha yam, MS + 1,5 mg l-1 et MS plus 2,0 mg l-1 NAA + 1,5 mg l-1 IBA est la meilleure combinaison phytohormonale pour la multiplication des pousses et l\u2019enracinement in vitro, respectivement

Natural history of a visceral leishmaniasis outbreak in highland Ethiopia

In May 2005, visceral leishmaniasis (VL) was recognized for the first time in Libo Kemken, Ethiopia, a highland region where only few cases had been reported before. We analyzed records of VL patients treated from May 25, 2005 to December 13, 2007 by the only VL treatment center in the area, maintained by Médecins Sans Frontières-Ethiopia, Operational Center Barcelona-Athens. The median age was 18 years; 77.6% were male. The overall case fatality rate was 4%, but adults 45 years or older were five times as likely to die as 5-29 year olds. Other factors associated with increased mortality included HIV infection, edema, severe malnutrition, pneumonia, tuberculosis, and vomiting. The VL epidemic expanded rapidly over a several-year period, culminating in an epidemic peak in the last third of 2005, spread over two districts, and transformed into a sustained endemic situation by 2007

Enzyme–free uric acid electrochemical sensors using β–cyclodextrin modified carboxylic acid functionalized carbon nanotubes

Carboxylic acid-functionalized multi-walled carbon nanotubes (COOH-MWCNT) were modified via ultrasonication with β-cyclodextrin (β-CD) to obtain a COOH-MWCNT:β-CD nanocomposite material for the purpose of developing an enzyme-free electrochemical sensor for uric acid—a clinically relevant molecule implemented in pregnancy-induced hypertension diagnosis. The nanocomposite material is deposited onto glassy carbon electrodes and subsequently capped with layers of Nafion and Hydrothane polyurethane. The surface morphology and electronic structure of the nanocomposite material were characterized using UV–Vis, TEM, and FTIR. The performance of the electrochemical sensor was measured through direct injection of UA during amperometry. With the high surface area of the COOH-MWCNT in concert with the selectivity provided by β-CD, the composite system outperforms similar COOH-MWCNT systems, displaying enhanced UA sensitivity versus films with only COOH-MWCNT. With the improved sensitivity (4.28 ± 0.11 µA mM−1) and fast response time (4.0 ± 0.5 s), the sensors offer wide detection of UA across clinically relevant ranges (100–700 μM) as well as demonstrated selectivity against various interferents

Continental rift architecture and patterns of magma migration: a dynamic analysis based on centrifuge models.

Small-scale centrifuge models were used to investigate the role of continental rift structure in controlling patterns of magma migration and emplacement. Experiments considered the reactivation of weakness zones in the lower crust and the presence of magma at Moho depths. Results suggest that surface deformation, which reflects the weakness zone geometry, exerts a major control on patterns of magma migration. In the case of a single rift segment, the experimental lower crust and magma were both transferred in an extension-parallel direction toward the rift flanks. This lateral migration reflected the dominance of far-field stresses over extension-induced buoyancy forces. Local pressure gradients favored the raise of experimental magma in correspondence of marginal grabens. The lateral migration gave rise to major accumulations below the footwall of major boundary faults, providing the magma source able to feed off-axis volcanoes in nature, as inferred for the Main Ethiopian Rift. In the case of two offset rift segments, a major transfer zone developed. This transfer zone was characterized by prominent experimental lower crust doming and strong magma accumulation. Dynamic analysis showed that the transfer zone development caused a strong pressure difference in a rift-parallel direction, which dominated over the farfield thinning. Owing to this pressure gradient, almost all the underplated experimental magma collected below the lower crust dome, suggesting a rift-parallel (extension-orthogonal) migration. This process has a direct relevance for the localization of magmatic activity at transfer zones in natural continental rifts, such as in the Western Branch of the East African Rift System. Copyright 2004 by the American Geophysical Union