Conflicting Tasks and Moral Hazard: Theory and Experimental Evidence

We study a multi-task principal-agent problem in which tasks can be in direct conflict with each other. In theory, it is difficult to induce a single agent to exert efforts in two conflicting tasks, because effort in one task decreases the success probability of the other task. We have conducted an experiment in which we find strong support for the relevance of this incentive problem. In the presence of conflict, subjects choose two efforts significantly less often when both tasks are assigned to a single agent than when there are two agents each in charge of one task.moral hazard, conflicting tasks, experiment

HYDRA: Hybrid Deep Magnetic Resonance Fingerprinting

Purpose: Magnetic resonance fingerprinting (MRF) methods typically rely on dictio-nary matching to map the temporal MRF signals to quantitative tissue parameters. Such approaches suffer from inherent discretization errors, as well as high computational complexity as the dictionary size grows. To alleviate these issues, we propose a HYbrid Deep magnetic ResonAnce fingerprinting approach, referred to as HYDRA. Methods: HYDRA involves two stages: a model-based signature restoration phase and a learning-based parameter restoration phase. Signal restoration is implemented using low-rank based de-aliasing techniques while parameter restoration is performed using a deep nonlocal residual convolutional neural network. The designed network is trained on synthesized MRF data simulated with the Bloch equations and fast imaging with steady state precession (FISP) sequences. In test mode, it takes a temporal MRF signal as input and produces the corresponding tissue parameters. Results: We validated our approach on both synthetic data and anatomical data generated from a healthy subject. The results demonstrate that, in contrast to conventional dictionary-matching based MRF techniques, our approach significantly improves inference speed by eliminating the time-consuming dictionary matching operation, and alleviates discretization errors by outputting continuous-valued parameters. We further avoid the need to store a large dictionary, thus reducing memory requirements. Conclusions: Our approach demonstrates advantages in terms of inference speed, accuracy and storage requirements over competing MRF method

Network growth model with intrinsic vertex fitness

© 2013 American Physical SocietyWe study a class of network growth models with attachment rules governed by intrinsic node fitness. Both the individual node degree distribution and the degree correlation properties of the network are obtained as functions of the network growth rules. We also find analytical solutions to the inverse, design, problems of matching the growth rules to the required (e.g., power-law) node degree distribution and more generally to the required degree correlation function. We find that the design problems do not always have solutions. Among the specific conditions on the existence of solutions to the design problems is the requirement that the node degree distribution has to be broader than a certain threshold and the fact that factorizability of the correlation functions requires singular distributions of the node fitnesses. More generally, the restrictions on the input distributions and correlations that ensure solvability of the design problems are expressed in terms of the analytical properties of their generating functions

Were Presolar Grains Destroyed by the Nebular Process Responsible for the Volatile Element Fractionation?

We present SiC abundances from a number of CM and CR chondrites using NanoSIMS raster ion imaging of acid residues. We find higher SiC abundances for CRs than previously estimated based on noble gases

Observability of information gathering in agency models

We consider an adverse selection model in which the agent can gather private information before the principal offers the contract. There are two scenarios. In scenario I, information gathering is a hidden action, while in scenario II, the principal observes the agent's information gathering decision. We study how the two scenarios differ with respect to the agent's expected rent, the principal's expected profit, and the expected total surplus. In particular, it turns out that the principal may be better off when the agent's information gathering decision is a hidden action

Observability of information gathering in agency models

We consider an adverse selection model in which the agent can gather private information before the principal offers the contract. There are two scenarios. In scenario I, information gathering is a hidden action, while in scenario II, the principal observes the agent's information gathering decision. We study how the two scenarios differ with respect to the agent's expected rent, the principal's expected profit, and the expected total surplus. In particular, it turns out that the principal may be better off when the agent's information gathering decision is a hidden action

Public-private partnerships versus traditional procurement: An experimental investigation

A government agency wants an infrastructure-based public service to be provided. Our experimental study compares two different modes of provision. In a public-private partnership, the two tasks of building the infrastructure and operating it are delegated to one private contractor (a consortium), while under traditional procurement, these tasks are delegated to separate contractors. We find support for the theoretical prediction that, compared to traditional procurement, a public-private partnership provides stronger incentives to make cost-reducing investments (which may increase or decrease service quality). In two additional treatments, we study governance structures which explicitly take subcontracting within private consortia into account.experiment, incomplete contracts, procurement, public-private partnerships

Overexpression, purification and characterisation of the Plasmodium falciparum Hsp70-z (PfHsp70-z) protein.

Six Hsp70-like genes are represented on the genome of Plasmodium falciparum. Of these two occur i0n the cytosol: P. falciparum Hsp70-z (PfHsp70-z) and PfHsp70-1. PfHsp70-1 is a well characterised canonical Hsp70 that facilitates protein quality control and is crucial for the development of malaria parasites. There is very little known about PfHsp70-z. However, PfHsp70-z is known to be essential and is implicated in suppressing aggregation of asparagine-rich proteins of P. falciparum. In addition, its expression at the clinical stage of malaria correlates with disease prognosis. Based on structural evidence PfHsp70-z belongs to the Hsp110 family of proteins. Since Hsp110 proteins have been described as nucleotide exchange factors (NEFs) of their canonical Hsp70 counterparts, it has been speculated that PfHsp70-z may serve as a NEF of PfHsp70-1. In the current study, P. falciparum cells cultured in vitro were subjected to heat stress, triggering the enhanced expression of PfHsp70-z. Biochemical assays conducted using recombinant PfHsp70-z protein demonstrated that the protein is heat stable and possesses ATPase activity. Furthermore, we observed that PfHsp70-z is capable of self-association. The structural-functional features of PfHsp70-z provide further evidence for its role as a chaperone and possible nucleotide exchange factor of PfHsp70-1.This project was through a grant (L1/402/ 14-1) provided to AS by the Deutsche Forchungsgemeinshaft (DFG) under the theme, “German–African Cooperation Projects in Infectology”. The authors are grateful to the Department of Science and Technology/National Research Foundation (NRF) of South Africa for providing an equipment grant (grant UID, 75464) to AS and (grant UID, 78558) to EP. HWD was awarded a research grant (64788) by the NRF (South Africa). AS is a recipient of a Georg Foster researchNCS201

Overexpression, purification and characterisation of the Plasmodium falciparum Hsp70-z (PfHsp70-z) protein.

Six Hsp70-like genes are represented on the genome of Plasmodium falciparum. Of these two occur i0n the cytosol: P. falciparum Hsp70-z (PfHsp70-z) and PfHsp70-1. PfHsp70-1 is a well characterised canonical Hsp70 that facilitates protein quality control and is crucial for the development of malaria parasites. There is very little known about PfHsp70-z. However, PfHsp70-z is known to be essential and is implicated in suppressing aggregation of asparagine-rich proteins of P. falciparum. In addition, its expression at the clinical stage of malaria correlates with disease prognosis. Based on structural evidence PfHsp70-z belongs to the Hsp110 family of proteins. Since Hsp110 proteins have been described as nucleotide exchange factors (NEFs) of their canonical Hsp70 counterparts, it has been speculated that PfHsp70-z may serve as a NEF of PfHsp70-1. In the current study, P. falciparum cells cultured in vitro were subjected to heat stress, triggering the enhanced expression of PfHsp70-z. Biochemical assays conducted using recombinant PfHsp70-z protein demonstrated that the protein is heat stable and possesses ATPase activity. Furthermore, we observed that PfHsp70-z is capable of self-association. The structural-functional features of PfHsp70-z provide further evidence for its role as a chaperone and possible nucleotide exchange factor of PfHsp70-1.This project was through a grant (L1/402/ 14-1) provided to AS by the Deutsche Forchungsgemeinshaft (DFG) under the theme, “German–African Cooperation Projects in Infectology”. The authors are grateful to the Department of Science and Technology/National Research Foundation (NRF) of South Africa for providing an equipment grant (grant UID, 75464) to AS and (grant UID, 78558) to EP. HWD was awarded a research grant (64788) by the NRF (South Africa). AS is a recipient of a Georg Foster researchNCS201

Properties of D-Branes in Matrix Model of IIB Superstring

We discuss properties of D-brane configurations in the matrix model of type IIB superstring recently proposed by Ishibashi, Kawai, Kitazawa and Tsuchiya. We calculate central charges in supersymmetry algebra at infinite N and associate them with one- and five-branes present in IIB superstring theory. We consider classical solutions associated with static three- and five-branes and calculate their interactions at one loop in the matrix model. We discuss some aspects of the matrix-model formulation of IIB superstring.Comment: 15pp., Latex, v2: a few typos corrected, v3: coefficient in Eq.(3.19) correcte