Artis Scribendi scite quasi libamentum frustumve praecidaneum

Jacobus author cujus est Melsdorpius Frisius Professor Artis in ubijs [Kupferstiche von Crispijn van de Passe].

Nonlinear quasi-static finite element simulations predict in vitro strength of human proximal femora assessed in a dynamic sideways fall setup

Osteoporotic proximal femur fractures are caused by low energy trauma, typically when falling on the hip from standing height. Finite element simulations, widely used to predict the fracture load of femora in fall, usually include neither mass-related inertial effects, nor the viscous part of bone's material behavior. The aim of this study was to elucidate if quasi-static non-linear homogenized finite element analyses can predict in vitro mechanical properties of proximal femora assessed in dynamic drop tower experiments. The case-specific numerical models of thirteen femora predicted the strength (R2=0.84, SEE=540 N, 16.2%), stiffness (R2=0.82, SEE=233 N/mm, 18.0%) and fracture energy (R2=0.72, SEE=3.85 J, 39.6%); and provided fair qualitative matches with the fracture patterns. The influence of material anisotropy was negligible for all predictions. These results suggest that quasi-static homogenized finite element analysis may be used to predict mechanical properties of proximal femora in the dynamic sideways fall situation.

Inseparable, incapable, or invisible: Why public organizations award no-bid contracts

No-bid contracting is a highly prevalent practice in public procurement of technology services. Alt-hough no-bid contracting is a substantial problem since it reduces competition and welfare, the litera-ture lacks theoretical explanations and empirical tests for why public organizations award no-bid con-tracts. In this paper, we propose three theoretical explanations for no-bid contracting, drawing on transaction cost economics, organizational learning, and institutional theory. We also present how we test these explanations using a comprehensive sample of public procurement transactions. We expect to contribute theoretical explanations for no-bid contracting and practical implications for policy-makers.

Experimental and Theoretical Electron Density Analysis of Copper Pyrazine Nitrate Quasi-Low-Dimensional Quantum Magnets

The accurate electron density distribution and magnetic properties of two metal-organic polymeric magnets, the quasi-one-dimensional (1D) Cu(pyz)(NO3)2 and the quasi-two-dimensional (2D) [Cu(pyz)2(NO3)]NO3·H2O, have been investigated by high-resolution single-crystal X-ray diffraction and density functional theory calculations on the whole periodic systems and on selected fragments. Topological analyses, based on quantum theory of atoms in molecules, enabled the characterization of possible magnetic exchange pathways and the establishment of relationships between the electron (charge and spin) densities and the exchange-coupling constants. In both compounds, the experimentally observed antiferromagnetic coupling can be quantitatively explained by the Cu-Cu superexchange pathway mediated by the pyrazine bridging ligands, via a σ-type interaction. From topological analyses of experimental charge-density data, we show for the first time that the pyrazine tilt angle does not play a role in determining the strength of the magnetic interaction. Taken in combination with molecular orbital analysis and spin density calculations, we find a synergistic relationship between spin delocalization and spin polarization mechanisms and that both determine the bulk magnetic behavior of these Cu(II)-pyz coordination polymers.

Capital Accumulation in the Presence of Informal Credit Contracts: Does the Incentive Mechanism Work Better than Credit Rationing Under Asymmetric Information?

Credit markets with asymmetric information often prefer credit rationing as a profit maximizing device. This paper asks whether the presence of informal credit markets reduces the cost of credit rationing, that is, whether it can alleviate the impact of asymmetric information based on the available information. We used a dynamic general equilibrium model with heterogenous agents to assess this. Using Indian credit market data our study shows that the presence of informal credit market can reduce the cost of credit rationing by separating high risk firms from the low risk firms in the informal market. But even after this improvement, the steady state capital accumulation is still much lower as compared to incentive based market clearing rates. Through self revelation of each firm's type, based on the incentive mechanism, banks can diversify their risk by achieving a separating equilibrium in the loan market. The incentive mechanism helps banks to increase capital accumulation in the long run by charging lower rates and lending relatively higher amount to the less risky firms. Another important finding of this study is that self-revelation leads to very significant welfare improvement, as measured by consumptiuon equivalence.

Optimal Central Banker Contracts and Common Agency

This paper considers the contacting approach to central banking in the context of a simple common agency model. The recent literature on optimal contracts suggests that the political principal of the central bank can design the appropriate incentive schemes that remedy for time-inconsistency problems in monetary policy. The effectiveness of such contracts, however, requires a central banker that attaches a positive weight to the incentive scheme. As a result, delegating monetary policy under such circumstances gives rise to the possibility that the central banker may respond to incentive schemes offered by other potential principals. We introduce common agency considerations in the design of optimal central banker contracts. We introduce two principals - society (government) and an interest group, whose objectives conflict with society's and we examine under what circumstances the government-offered or the interest-group-offered contract dominates. Our results largely depend on the type of bias that the interest group contract incorporates. In particular, when the interest group contract incorporates an inflationary bias the outcome depends on the principals' relative concern of the incentive schemes' costs. When the interest group contract incorporates an expansionary bias, however, it always dominates the government contract. A corollary of our results is that central banker contracts aiming to remove the expansionary bias of policymakers should be written explicitly in terms of the perceived bias.

Can a Newly Proposed Mechanism for Allocating Contracts in U.S. Electricity Wholesale Markets Lead to Lower Prices? A Game Theoretic Analysis

This study of the wholesale electricity market compares the cost-minimizing performance of the auction mechanism currently in place in U.S. markets with the performance of a proposed replacement. The current mechanism chooses an allocation of contracts that minimizes a fictional cost calculated using pay-as-offer pricing. Then suppliers are paid the market clearing price. The proposed mechanism uses the market clearing price in the allocation phase as well as in the payment phase. In concentrated markets, the proposed mechanism outperforms the current mechanism even when strategic behavior by suppliers is taken into account. The advantage of the proposed mechanism increases with increased price competition.

A Case Study of an Agency's Three Family Preservation Contracts

This article presents a case study of a nonprofit child welfare agency that delivered family preservation services under three different purchase-of-service (POS) contracts. The research specifically focuses on how certain POS contract provisions and reimbursement rates influence the delivery of family preservation services. The three contacts examined differed on criteria, such as reimbursement mechanism, service volume, definition of clientele, and reimbursement rate. The study found that as reimbursement rates decline and as administrative costs increase, the service provider struggled with cash flow, staffing, fundraising, and service provision, among other things. It is concluded that contract-related resources, policies, and procedures impact provider agencies in multiple, significant ways that are critical to the provision of services and the accomplishment of positive client outcomes.

Incentives Embedded in Institutions: The Case of Share Contracts in Ghanaian Cocoa Production

Providing price incentives to farmers is usually considered essential for agricultural development. Although such incentives are important, regarding price as the sole explanatory factor is far from satisfactory in understanding the complex realities of agricultural production in Africa. By analyzing the share contracts widely practiced in Ghana, this article argues that local institutions such as land tenure systems and agrarian contracts provide strong incentives and disincentives for agricultural production. Based on data derived from fieldwork in the 1990s, the study analyzes two types of share contracts and the incentive structures embedded in them. The analysis reveals that farmers' investment behavior needs to be understood in terms of both short-term incentive to increase yield and long-term incentive to strengthen land rights. The study concludes that the role of price incentives in agricultural production needs to be reconsidered by placing it in wider incentive structures embedded in local institutions.

Quasi-experimental evidence on the drivers of index-based livestock insurance demand in Southern Ethiopia

Microinsurance is widely considered an important tool for sustainable poverty reduction, especially in the face of increasing climate risk. Although index-based microinsurance, which should be free from the classical incentive problems, has attracted considerable attention, uptake rates have generally been weak in low-income rural communities. We explore the purchase patterns of index-based livestock insurance in southern Ethiopia, focusing in particular on the role of accurate product comprehension and price, including the prospective impact of temporary discount coupons on subsequent period demand due to price anchoring effects. We find that randomly distributed learning kits contribute to improving subjects' knowledge of the products; however, we do not find strong evidence that the improved knowledge per se induces greater uptake. We also find that reduced price due to randomly distributed discount coupons has an immediate, positive impact on uptake, without dampening subsequent period demand due to reference-dependence associated with price anchoring effects.