Search results for "FIX"

Spatial segregation of the biological soil crust microbiome around its foundational cyanobacterium, Microcoleus vaginatus, and the formation of a nit…

2019

12 pages; International audience; Background Biological soil crusts (biocrusts) are a key component of arid land ecosystems, where they render critical services such as soil surface stabilization and nutrient fertilization. The bundle-forming, filamentous, non-nitrogen-fixing cyanobacterium Microcoleus vaginatus is a pioneer primary producer, often the dominant member of the biocrust microbiome, and the main source of leaked organic carbon. We hypothesized that, by analogy to the rhizosphere of plant roots, M. vaginatus may shape the microbial populations of heterotrophs around it, forming a specialized cyanosphere. Results By physically isolating bundles of M. vaginatus from biocrusts, we …

Quantification of denitrifying bacteria in soils by nirK gene targeted real-time PCR.

2004

Abstract Denitrification, the reduction of nitrate to nitrous oxide or dinitrogen, is the major biological mechanism by which fixed nitrogen returns to the atmosphere from soil and water. Microorganisms capable of denitrification are widely distributed in the environment but little is known about their abundance since quantification is performed using fastidious and time-consuming MPN-based approaches. We used real-time PCR to quantify the denitrifying nitrite reductase gene (nirK), a key enzyme of the denitrifying pathway catalyzing the reduction of soluble nitrogen oxide to gaseous form. The real-time PCR assay was linear over 7 orders of magnitude and sensitive down to 102 copies by assa…

Immunological diagnosis of human hydatid cyst relapse: utility of the enzyme-linked immunoelectrotransfer blot and discriminant analysis.

2000

ABSTRACT A discriminant technique was applied to the different serological patterns obtained by enzyme-linked immunoelectrotransfer blotting (EITB) and by conventional immunological tests, in order to differentiate the residual antibody patterns present in healed hydatidosis from the ones present in patients with active hydatidosis. For this purpose, specific antibodies against Echinococcus granulosus were detected by indirect hemagglutination, agglutination of latex particles, basophil degranulation, and EITB for 23 patients with active hydatidosis and 45 patients with surgically cured hydatidosis. Discriminant analysis of the different serological patterns obtained by EITB and conventiona…

Isolation and Characterization of High-Efficiency Rhizobia From Western Kenya Nodulating With Common Bean.

2021

Common bean is one of the primary protein sources in third-world countries. They form nodules with nitrogen-fixing rhizobia, which have to be adapted to the local soils. Commercial rhizobial strains such as Rhizobium tropici CIAT899 are often used in agriculture. However, this strain failed to significantly increase the common bean yield in many places, including Kenya, due to the local soils’ low pH. We isolated two indigenous rhizobial strains from the nodules of common bean from two fields in Western Kenya that have never been exposed to commercial inocula. We then determined their ability to fix nitrogen in common beans, solubilize phosphorus, and produce indole acetic acid. In greenhou…

Most-favored-customer pricing, product variety, and welfare

2013

Abstract Most-favored-customer (MFC) clauses are usually seen as anticompetitive co-ordination devices that firms adopt for the purpose of higher prices. Here, I examine the welfare impact of MFC clauses under endogenous product variety. Product variety is relevant because prospective higher prices from MFC clauses can be anticipated by multi-product firms in their provision of product lines. Under such circumstances, I find that these clauses can be socially harmful, but this is not always the case: they tend to be socially neutral for relatively large fixed costs of product-line assortment, harmful for intermediate costs, and beneficial for relatively small costs.

Portfolio Models for Fixed Income

2010

Dynamic Portfolio Optimization with Stochastic Programming

2010

Welfare, Home Market Effects, and Horizontal Foreign Direct Investment

2005

We investigate the spatial distribution and organization of an imperfectly competitive industry when firms may choose to operate more than a single production unit. Focusing on a short-run setting with a fixed mass of firms, we fully characterize the spatial equilibria analytically. Comparing the equilibrium and the first-best, we show that both organizational and spatial inefficiencies may arise. In particular, when fixed costs are low enough the market outcome may well lead to overinvestment and, therefore, to too many multinationals operating from a social point of view. Furthermore, once multinationals are taken into account, the market outcome may well lead too little agglomeration.

Contract, Renegotiation, and Holdup: When Should Messages be Sent?

2015

I consider a setting of complete but unverifiable information in which two agents enter a contractual relationship to induce mutually beneficial investments. As my main result, I establish that the famous irrelevance of contracting paradigm, that arises due to the detrimental effect of renegotiation, is resolved if there is a fixed point in time when actions have to be chosen and one accounts for the fact that renegotiation takes time. What drives my optimality result is that, by stipulating when the mechanism is to be played, the agents ensure that renegotiation is possible ex ante but not ex post.

Fixed Costs Per Shipment

2011

Exporting firms do not only decide how much of their products they ship abroad but also at which frequency. Doing so, they face a trade-off between saving on fixed costs per shipments (by shipping large amounts infrequently) and saving on storage costs (by delivering just in time with small and frequent shipments). The firm's optimal choice defines a mapping from size and frequency of shipments to fixed costs per shipment. We use a unique dataset of Swiss cross-border trade on the transaction level to analyze the size and shape of the underlying fixed costs. The data suggest that for the average Swiss exporter the fixed costs per shipment are economically important: 0.82 percent of the valu…