Fast and frugal heuristics for portfolio decisions with positive project interactions

We consider portfolio decision problems with positive interactions between projects. Exact solutions to this problem require that all interactions are assessed, requiring time, expertise and effort that may not always be available. We develop and test a number of fast and frugal heuristics – psychologically plausible models that limit the number of assessments to be made and combine these in computationally simple ways – for portfolio decisions. The proposed “add-the-best” family of heuristics constructs a portfolio by iteratively adding a project that is best in a greedy sense, with various definitions of “best”. We present analytical results showing that information savings achievable by heuristics can be considerable; a simulation experiment showing that portfolios selected by heuristics can be close to optimal under certain conditions; and a behavioral laboratory experiment demonstrating that choices are often consistent with the use of heuristics. Add-the-best heuristics combine descriptive plausibility with effort-accuracy trade-offs that make them potentially attractive for prescriptive use

Holomorphic transforms with application to affine processes

In a rather general setting of It\^o-L\'evy processes we study a class of transforms (Fourier for example) of the state variable of a process which are holomorphic in some disc around time zero in the complex plane. We show that such transforms are related to a system of analytic vectors for the generator of the process, and we state conditions which allow for holomorphic extension of these transforms into a strip which contains the positive real axis. Based on these extensions we develop a functional series expansion of these transforms in terms of the constituents of the generator. As application, we show that for multidimensional affine It\^o-L\'evy processes with state dependent jump part the Fourier transform is holomorphic in a time strip under some stationarity conditions, and give log-affine series representations for the transform.Comment: 30 page

Performance Assessment of Two-parameter Weibull Distribution Methods for Wind Energy Applications in the District of Maroua in Cameroon

Wind speed is the most important parameter to be considered when designing wind energy conversion systems (WECS), since its probability density distribution greatly affects the performance. In this paper, five numerical methods were analysed and their performance evaluated for effectiveness in determining the parameters for the Weibull distribution. Twenty eight years (198

Eutrophication, sediment Phosphorus fractionation and short-term mobility study in the surface and under profile sediment of a water dam. (Okpara dam, Benin, West Africa).

Okpara dam supplies the drinking water treatment station of Parakou town. Aquatic plants proliferation and chemical stratification of the water column in this reserve let see clear manifestation of eutrophication process. Phosphorus concentration in sediments was estimated in the range of 13.479 mg/g to 35.46 mg/g dry wet of sediment. These values are high and not common in the literature. The measured Phosphorus and a-chlorophyll values in the water column show hyper-eutrophication. From N/P ratio, Nitrogen is the limiting factor of eutrophication in Okpara dam, but this does not stop eutrophication. Phosphorus fractionation according to Rydin and Welch (1998) under oxic conditions for surface results sediment and under profile sediment was studied. It was demonstrated that: Fe-bound-P, Al-bound-P and Organic-bound-P comprise the largest phosphorus pool (30% to 51% of Total Phosphorus). High soluble reactive phosphorus content was measured in sediment column compared to other study cases. Organic phosphorus fraction represents 90% of the Total Extracted Phosphorus content. Water and sediment column acidity could allowed iron and humic acids production from the high organic matter amount (21.42% to 28.30%) in the dam to modulate P releasing from sediment. Phosphorus short term remobilization study lets know that deeper sediment organic matters are more mineralized and released more phosphorus (95%) than surface sediment (20%). This fact is not suitable for sediment dredging to 1metter deeper because of eutrophication resumption. In oxic medium aluminum and iron orthophosphate are precipitated more in acidic solution. Phosphorus constitutes iron mobility factor in the dam

Thrombospondin-2 and SPARC/osteonectin are critical regulators of bone remodeling

Thrombospondin-2 (TSP2) and osteonectin/BM-40/SPARC are matricellular proteins that are highly expressed by bone cells. Mice deficient in either of these proteins show phenotypic alterations in the skeleton, and these phenotypes are most pronounced under conditions of altered bone remodeling. For example, TSP2-null mice have higher cortical bone volume and are resistant to bone loss associated with ovariectomy, whereas SPARC-null mice have decreased trabecular bone volume and fail to demonstrate an increase in bone mineral density in response to a bone-anabolic parathyroid hormone treatment regimen. In vitro, marrow stromal cell (MSC) osteoprogenitors from TSP2-null mice have increased proliferation but delayed formation of mineralized matrix. Similarly, in cultures of SPARC-null MSCs, osteoblastic differentiation and mineralized matrix formation are decreased. Overall, both TSP2 and SPARC positively influence osteoblastic differentiation. Intriguingly, both of these matricellular proteins appear to impact MSC fate through mechanisms that could involve the Notch signaling system. This review provides an overview of the role of TSP2 and SPARC in regulating bone structure, function, and remodeling, as determined by both in vitro and in vivo studies

Vigilant Measures of Risk and the Demand for Contingent Claims

I examine a class of utility maximization problems with a not necessarily lawinvariant utility, and with a not necessarily law-invariant risk measure constraint. The objective function is an integral of some function U with respect to some probability measure P, and the constraint set contains some risk measure constraint which is not necessarily P-law-invariant. This introduces some heterogeneity in the perception of uncertainty. The primitive U is a function of some given underlying random variable X and of a contingent claim Y on X. Many problems in economic theory and financial theory can be formulated in this manner, when a heterogeneity in the perception of uncertainty is introduced. Under a consistency requirement on the risk measure that will be called Vigilance, supermodularity of the primitive U is sufficient for the existence of optimal continent claims, and for these optimal claims to be comonotonic with the underlying random variable X. Vigilance is satisfied by a large class of risk measures, including all distortion risk measures. An explicit characterization of an optimal contingent claim is also provided in the case where the risk measure is a convex distortion risk measure

Assessment of the Rural Water Supply Potential by Mechanical Wind Pumping Around the Floodplains of Lake Chad

International audienc

Ebogotermes raphaeli, new genus and new species, an African soldierless termite described from the worker caste (Isoptera, Termitidae, Apicotermitinae)

Ebogotermes raphaeli gen. n. sp. n. is described from workers collected in Cameroon. This soil-feeding termite is the largest soldierless termite from central Africa and aligns with the Anoplotermes subgroup. The enteric valve armature is weakly armed and, as with most apicotermitine species, is uniquely diagnostic.SCOPUS: ar.jinfo:eu-repo/semantics/publishe