Two-sided reputation in certification markets

We consider a market where privately informed sellers resort to certification to overcome adverse selection. There is uncertainty about the certifier's ability to generate accurate information. The profit of a monopolistic certifier is an inverted U-shaped function of his reputation for accuracy: being perceived as more precise allows to attract more good sellers but a high expected precision also deters bad sellers. Since the certifier tries to reach a balanced reputation to attract both types, reputation has a disciplining effect when the certifier is perceived as insufficiently accurate, but gives incentives to decrease precision when he is perceived as “too" accurate. The impact of competition depends on whether sellers “multihome" or “singlehome". Under singlehoming, certifiers compete to attract good sellers, which makes higher reputation more valuable. Multihoming makes higher reputations less desirable because the competitor exerts a negative externality by providing extra information. Therefore, singlehoming attenuates bad reputation effects, while multihoming exacerbates inefficiencies

Counter-rotation in an orbitally shaken glass of beer

Swirling a glass of wine induces a rotating gravity wave along with a mean flow rotating in the direction of the applied swirl. Surprisingly, when the liquid is covered by a floating cohesive material, for instance a thin layer of foam in a glass of beer, the mean rotation at the surface can reverse. This intriguing counter-rotation can also be observed with coffee cream, tea scum, cohesive powder, provided that the wave amplitude is small and the surface covering fraction is large. Here we show that the mechanism for counter-rotation is a fluid analog of the rolling without slipping motion of a planetary gear train: for sufficiently large density, the covered surface behaves as a rigid raft transported by the rotating sloshing wave, and friction with the near-wall low-velocity fluid produces a negative torque which can overcome the positive Stokes drift rotation induced by the wave.Comment: To appear in EPL (2018

Entangled single-wire NiTi material: a porous metal with tunable superelastic and shape memory properties

NiTi porous materials with unprecedented superelasticity and shape memory were manufactured by self-entangling, compacting and heat treating NiTi wires. The versatile processing route used here allows to produce entanglements of either superelastic or ferroelastic wires with tunable mesostructures. Three dimensional (3D) X-ray microtomography shows that the entanglement mesostructure is homogeneous and isotropic. The thermomechanical compressive behavior of the entanglements was studied using optical measurements of the local strain field. At all relative densities investigated here ($\sim$ 25 - 40$\%$), entanglements with superelastic wires exhibit remarkable macroscale superelasticity, even after compressions up to 25$\%$, large damping capacity, discrete memory effect and weak strain-rate and temperature dependencies. Entanglements with ferroelastic wires resemble standard elastoplastic fibrous systems with pronounced residual strain after unloading. However, a full recovery is obtained by heating the samples, demonstrating a large shape memory effect at least up to 16% strain.Comment: 31 pages, 10 figures, submitted to Acta Materiali

«Jamendo: The Heartbeat of Free Music!» Musicians and the Creative Commons

Jamendo is a website for the legal, free downloading of music. This platform of "free" online music, the biggest in the world, operates on the basis of Creative Commons licences. The survey presented here was carried out on a sample of 767 artists (solo musicians or groups) who are members of Jamendo. Our purpose in carrying out this survey was to identify as precisely as possible the characteristics of the artists present on Jamendo and the type of CC licence they choose in order to better understand the motives for their choices. To go further, the question is that of the Jamendo business model from the artists' point of view. Does Jamendo simply represent a great opportunity for amateurs to showcase their music and win an audience? Or is Jamendo also capable of attracting professional artists, for whom earning an income from their music is essential? To put it another way, the underlying question is whether platforms like Jamendo constitute a possible alternative model for the music industry of tomorrow

Ultrastructural characteristics of glucocorticoid-induced osteoporosis

International audienc

Glucose-dependent insulinotropic polypeptide (GIP) directly affects collagen fibril diameter and collagen cross-linking in osteoblast cultures.

Glucose-dependent insulinotropic polypeptide (GIP) is absolutely crucial in order to obtain optimal bone strength and collagen quality. However, as the GIPR is expressed in several tissues other than bone, it is difficult to ascertain whether the observed modifications of collagen maturity, reported in animal studies, were due to direct effects on osteoblasts or indirect through regulation of signals originating from other tissues. The aims of the present study were to investigate whether GIP can directly affect collagen biosynthesis and processing in osteoblast cultures and to decipher which molecular pathways were necessary for such effects. MC3T3-E1 cells were cultured in the presence of GIP ranged between 10 and 100pM. Collagen fibril diameter was investigated by electron microscopy whilst collagen maturity was determined by Fourier transform infra-red microspectroscopy (FTIRM). GIP treatment resulted in dose-dependent increases in lysyl oxidase activity and collagen maturity. Furthermore, GIP treatment shifted the collagen fiber diameter towards lower value but did not significantly affect collagen heterogeneity. GIP acted directly on osteoblasts by activating the adenylyl cyclase-cAMP pathway. This study provides evidences that GIP acts directly on osteoblasts and is capable of improving collagen maturity and fibril diameter

Internet Poker Websites and Pathological Gambling Prevention Policy

Despite the widespread increase in online poker playing and the risk related to excessive poker playing, research on online poker websites is still lacking with regard to pathological gambling prevention strategies offered by the websites. The aim of the present study was to assess the pathological gambling-related prevention strategies of online poker websites. Two keywords ("poker” and "poker help”) were entered into two popular World Wide Web search engines. The first 20 links related to French and English online poker websites were assessed. Seventy-four websites were assessed with a standardized tool designed to rate sites on the basis of accountability, interactivity, prevention strategies, marketing, and messages related to poker strategies. Prevention strategies appeared to be lacking. Whereas a substantial proportion of the websites offered incitation to gambling such as betting "tips,” few sites offered strategies to prevent or address problem gambling. Furthermore, strategies related to poker, such as probability estimation, were mostly reported without acknowledging their limitations. Results of this study suggest that more adequate prevention strategies for risky gambling should be developed for online poke

Monoclonal gammopathy of undetermined significance, multiple myeloma, and osteoporosis

The finding of monoclonal gammopathy of undetermined significance (MGUS) is not infrequent during an evaluation for osteoporosis or a fracture. In most cases, the diagnosis is MGUS, whose prevalence increases with age. Although the impact of MGUS on bone mineral density, bone remodeling, and the fracture risk remains unclear, this asymptomatic hematological disorder may constitute a risk factor for osteoporosis. Furthermore, each year, 1% of patients with MGUS progress to multiple myeloma, a disease whose pathophysiology and association with bone loss and pathological fractures are increasingly well understood. Osteoporotic fractures, although probably common in myeloma patients, are less likely to be recognized. Here, we discuss the pathophysiology of myeloma and MGUS and their impact in terms of bone mineral density, osteoporotic fractures, and bone turnover markers