A Structural Model for the Coevolution of Networks and Behavior

This paper introduces a structural model for the coevolution of networks and behavior. We characterize the equilibrium of the underlying game and adopt the Bayesian Double Metropolis-Hastings algorithm to estimate the model. We further extend the model to incorporate unobserved heterogeneity and show that ignoring unobserved heterogeneity can lead to biased estimates in simulation experiments. We apply the model to study R&D investment and collaboration decisions in the chemical and pharmaceutical industry and find a positive knowledge spillover effect. Our model also provides a tractable framework for a long-run key player analysis

R&D Decisions and Productivity Growth: Evidence from Switzerland and the Netherlands

The fraction of R&D-active firms decreased in Switzerland but increased in the Netherlands from 2000-2016. This paper examines reasons for this divergence and its impact on productivity growth. Our micro-data reveal R&D concentration among high-productivity firms in Switzerland. Innovation support sustains firms’ R&D activities in both countries. Our structural growth model identifies the impact of innovation, imitation and R&D costs on firms’ R&D decisions. R&D costs gained importance in Switzerland but not in the Netherlands, explaining the diverging R&D trends. Yet, counterfactual analyses show that policies should prioritize enhancing innovation and imitation success over cost reduction to boost productivity growth

Collaboration in Bipartite Networks, with an Application to Coauthorship Networks

This paper studies the impact of collaboration on research output. First, we build a micro-founded model for scientific knowledge production, where collaboration between researchers is represented by a bipartite network. The equilibrium of the game incorporates both the complementarity effect between collaborating researchers and the substitutability effect between concurrent projects of the same researcher. Next, we develop a Bayesian MCMC procedure to estimate the structural parameters, taking into account the endogenous matching of researchers and projects. Finally, we illustrate the empirical relevance of the model by analyzing the coauthorship network of economists registered in the RePEc Author Service

Social networks and collective action in large populations: An application to the Egyptian Arab Spring

We study a dynamic model of collective action in which agents interact and learn through a co-evolving social network. Our approach highlights the importance of communication in this problem and conceives the social network – which is continuously evolving – as the structure through which agents not only interact but also communicate. We consider two alternative scenarios that differ only on how agents form their expectations: while in the “benchmark” context agents are completely informed, in the alternative one their expectations are formed through a combination of local observation and social learning à la DeGroot. We completely characterize the long-run behavior of the system in both cases and show that only in the latter scenario (arguably the most realistic) there is a significant long-run probability that agents eventually achieve collective action within a meaningful time scale. This, we argue, sheds light on the puzzle of how large populations can coordinate on globally desired outcomes. Finally, we illustrate the empirical potential of the model by showing that it can be efficiently estimated for the so-called Egyptian Arab Spring using large-scale cross-sectional data from Twitter

Computational and experimental analysis identified 6-diazo-5-oxonorleucine as a potential agent for treating infection by Plasmodium falciparum

Plasmodium falciparum (PF) is the most severe malaria parasite. It is developing resistance quickly to existing drugs making it indispensable to discover new drugs. Effective drugs have been discovered targeting metabolic enzymes of the parasite. In order to predict new drug targets, computational methods can be used employing database information of metabolism. Using this data, we performed recently a computational network analysis of metabolism of PF. We analyzed the topology of the network to find reactions which are sensitive against perturbations, i.e., when a single enzyme is blocked by drugs. We now used a refined network comprising also the host enzymes which led to a refined set of the five targets glutamyl–tRNA (gln) amidotransferase, hydroxyethylthiazole kinase, deoxyribose–phophate aldolase, pseudouridylate synthase, and deoxyhypusine synthase. It was shown elsewhere that glutamyl– tRNA (gln) amidotransferase of other microorganisms can be inhibited by 6-diazo-5-oxonorleucine. Performing a half maximal inhibitory concentration (IC50) assay, we showed, that 6-diazo-5-oxonorleucine is also severely affecting viability of PF in blood plasma of the human host. We confirmed this by an in vivo study observing Plasmodium berghei infected mice

Assessment of proximal outcomes of self-management programs : translation and psychometric evaluation of a German version of the Health Education Impact Questionnaire (heiQtm)

Purpose This paper describes the translation, cultural adaption, and psychometric evaluation of a German version of the Health Education Impact Questionnaire (heiQ&trade;), a widely used generic instrument assessing a wide range of proximal outcomes of self-management programs.Methods The translation was carried out according to international standards and included forward and backward translations. Comprehensibility and content validity were tested using cognitive interviews with 10 rehabilitation inpatients. Psychometric properties were examined in rehabilitation inpatients (n = 1,202) with a range of chronic conditions. Factorial validity was assessed using confirmatory factor analysis; concurrent validity was explored by correlations with comparator scales.Results The items of the German heiQ&trade; were well understood by rehabilitation inpatients. The structure of the eight heiQ&trade; scales was replicated after minor adjustment. heiQ&trade; scales had higher correlations with comparator scales with similar constructs, particularly mental health concepts than with physical health. Moreover, all heiQ&trade; scales differentiated between individuals across different levels of depression.Conclusion The German heiQ&trade; is comprehensible for German-speaking patients suffering from different types of chronic conditions; it assesses relevant outcomes of self-management programs in a reliable and valid manner. Further studies involving its practical application are warranted.<br /

SURVEILLANCE FOR VANCOMYCIN RESISTANT ENTEROCOCCI IN A TERTIARY INSTITUTION IN SOUTH WESTERN NIGERIA

Background. Enterococci are responsible for up to 12% of cases of healthcare associated infections worldwide and cause life threatening infections among critically ill patients. They show intrinsic and acquired resistance to a wide range of antimicrobial agents. Glycopeptide resistance is due to vanA, vanB, vanC, vanD, vanE, vanG and vanL genes. Objectives. To determine the carriage rate of VRE among patients on prolonged hospitalization in LUTH, assess the antimicrobial resistance pattern of VRE, identify factors associated with VRE colonization and describe the genetic determinants of enterococcal resistance to Vancomycin. Methods. VRE were isolated from rectal swabs collected from patients hospitalized for seven days or more in Lagos University Teaching Hospital and identified by Matrix Assisted Laser Desorption Ionization (MALDI) and Polymerase Chain Reaction (PCR). Antimicrobial susceptibility testing was performed by E-test. PCR assay for Vancomycin resistance genes was also performed. Data on demographic and risk factors collected by questionnaire was tested for significance using chi square. Results. Thirteen of 319 patients surveyed were colonized with VRE; one with vanA E. faecium, two with vanB E. faecium, ten with E. gallinarum and one with E. casseliflavus. Univariate analysis for risk factors associated with VRE colonization was only significant for the ward of admission. Only one VRE isolate showed full resistance to vancomycin and Teicoplanin. Three were resistant to Ampicillin and nine to Ciprofloxacin but all were susceptible to Linezolid. High-level resistance to Gentamicin was found in four VRE isolates. Conclusion. There is a low prevalence of VRE in Lagos University Teaching Hospital which may be spreading among patients in affected wards