Rank-order competition in the voluntary provision of impure public goods

Publicly provided goods often create differential payoffs due to timely or spatial distances of group members. We design and test a provision mechanism which utilizes rank competition to mitigate free-riding in impure public goods. In our Rank-Order Voluntary Contribution Mechanism (Rank-Order-VCM) group members compete via observable contributions for a larger share of the public good; high contributors receive preferential access (a larger share), while low contributors receive restricted access (a lower share). In a laboratory experiment Rank-Order-VCM elicits median contributions equal to the full endowment throughout the finitely played games with constant groups. In the control treatment, with randomly assigned ranks, the contributions are significantly lower and decline over time. We thus provide evidence of rank competition, in situations where discriminatory access to public goods is possible, being efficiency enhancing

Analysis of cryptocurrency dependencies

In a world where no country, market, or economy is an island, interconnectivity is becoming a fundamental feature of almost all social and economic systems. In the case of digital assets like cryptocurrencies, the impact of interconnectivity on their performance and price trajectory is amplified. Studying these phenomena is essential for understanding the processes driving the crypto-markets. In this paper, we propose seven different approaches to create a network of eighteen most important cryptocurrencies. The first three approaches discover correlations between cryptocurrencies based on their daily prices, daily returns, and sentiment extracted from Reddit data. The following two approaches offer insights from the frequency of joint appearance of cryptocurrencies in Google news and Reddit data. The remaining two approaches determine each cryptocurrency’s impact over the others when forecasting prices and returns. Furthermore, we explore the networks’ interdependencies to explore the similarities of the cryptocurrency networks generated by different approaches. The proposed methodology allows us to understand the dynamics in the cryptocurrency markets and the different processes that influence their performance.Published versio

Copper complexes as a source of redox active MRI contrast agents

The study reports an advance in designing copper-based redox sensing MRI contrast agents. Although the data demonstrate that copper(II) complexes are not able to compete with lanthanoids species in terms of contrast, the redox-dependent switch between diamagnetic copper(I) and paramagnetic copper(II) yields a novel redox-sensitive contrast moiety with potential for reversibility

Perfluorocarbon lipid nanoparticles for dual-frequency MR Neuroimaging applications

Introduction Although BOLD-based fMRI is extensively used to indicate neuronal activity, a great step forward in detecting brain activity directly would be the measurement of [Ca2+] by means of bioresponsive MRI contrast agents, probes able to modulate their signal-enhancement effect in response to [Ca2+] fluctuations. Here we report a lipid nanoparticle (GdPFLNPs) with a surface bearing Ca-responsive Gd3+ complexes (GdL) and a perfluorocarbon core. Such nanoprobe would enable the dual-frequency imaging of [Ca2+], coregistering its 1H MRI Ca-enhanced contrast with the quantitative signal of 19F MRI. Methods The lipid nanoparticles were obtained through the rehydration of a lipid film (L/DPPC/DSPE-PEG2000 in 20:75:5 ratio) with a suspension of perfluoro-15-crown-5-ether (PFCE) in aqueous HEPES and NaCl. The obtained suspension was sonicated and extruded with 200 nm cutoff filters. Complexation was performed after extrusion in order to decorate with Gd3+ exclusively the ligand molecules exposed on the outer nanoparticle surface. The final nanoparticles were purified by dialysis and ultracentrifugation. The size and shape of the obtained particles were assessed by dynamic light scattering (DLS) and cryo-TEM imaging, the relaxometric properties were characterized by 1H and 19F NMR spectrometry, while the imaging potential was demonstrated by means of 1H and 19F MRI on tube phantoms at 7 T. Results/Discussion The obtained suspension was analyzed by DLS resulting in a polydisperse system, with particle diameter of 78.2 nm and 236.9 nm (PDI 0.30). Cryo-TEM images confirmed the size distribution of the sample and revealed particles of spherical shape with an electron-dense core, characteristic for this kind of system.1 Furthermore, no evident change of size or shape of the particles seems to occur upon binding of Ca2+. The potential of GdPFLPNs as Ca-responsive 1H MRI contrast agents was characterized by means of relaxometric titrations at 25 °C and 7 T (Figure 1), resulting in a significant increase of longitudinal and transverse relaxivities, r1 (+31%) and r2 (+343%), respectively. On the other hand, 19F T1 value (974 ms) did not change throughout the titration. Additionally, 1H MRI on tube phantoms showed the great potential of this system as T2w and T2/T1w Ca-responsive agent, while 19F T1w MRI images of the samples exhibited very high SNR for corresponding low [Gd3+] samples (Figure 2). Conclusions In this work we report a nanosized Ca-responsive probe for dual-frequency MRI. The possibility of exploiting its advantageous performances as T2- and T2/T1-sensitive contrast agent, together with the high SNR obtained with quantitative 19F MRI, opens new realms for a wide range of possible future applications, focused on the monitoring and mapping of [Ca2+] in the brain, such as Ca-dependent molecular- and stimuli-coupled functional neuroimaging

Title Dinuclear Heterometallic Lanthanide Complexes Exhibiting MRI and Luminescence Response

Heteronuclear lanthanide complexes have gained an increased level of interest recently, due to their high potential for application in various molecular imaging techniques. They appear primarily as the most rational choice for agents to be used in multimodal imaging approaches.[1-2] Namely, due to their versatile physicochemical properties, they are widely used in MRI or luminescence imaging. Several lanthanide complexes have been reported recently with the potential to be used as multimodal agents. Depending on the approach the final ligand structure contained a single chelator for the lanthanide ion, or consisted of two chelating units, consequently bearing same or different Ln3+. Following these principles, we designed and synthesized a ligand containing two different chelators where the antenna acts not only as a linker between these two chelators, but also as an integral component in one of their structures. The macrocyclic, DOTA-type moiety of this ligand forms a stable complex with Eu3+ and Gd3+ which exhibit the expected luminescence emission and relaxometric characteristics, respectively. An aryl-containing acyclic chelator 5A-PADDTA (abbreviated from 5-aminoisophthalamide diethylenediaminetetraacid) of this ligand also forms complexes with lanthanides and their existence is confirmed by the means of luminescence and NMR spectroscopy. Depending on the choice of the metal ion (Gd3+, Tb3+, Eu3+, Nd3+, Yb3+ or Er3+), the system could act as a potential dual-modal (MRI / Vis or NIR luminescence imaging) or dual-emissive (luminescence imaging at various wavelengths in Vis/NIR region) contrast agent

Preparation and In Vitro Characterization of Dendrimer-based Contrast Agents for Magnetic Resonance Imaging

This protocol describes the preparation and characterization of a dendrimeric magnetic resonance imaging (MRI) contrast agent that carries cyclen-based macrocyclic chelates coordinating paramagnetic gadolinium ions. In a series of MRI experiments in vitro, this agent produced an amplified MRI signal when compared to the commercially available monomeric analogue