Accuracy-Risk Trade-Off Due to Social Learning in Crowd-Sourced Financial Predictions

A critical question relevant to the increasing importance of crowd-sourced-based finance is how to optimize collective information processing and decision-making. Here, we investigate an often under-studied aspect of the performance of online traders: beyond focusing on just accuracy, what gives rise to the trade-off between risk and accuracy at the collective level? Answers to this question will lead to designing and deploying more effective crowd-sourced financial platforms and to minimizing issues stemming from risk such as implied volatility. To investigate this trade-off, we conducted a large online Wisdom of the Crowd study where 2037 participants predicted the prices of real financial assets (S&P 500, WTI Oil and Gold prices). Using the data collected, we modeled the belief update process of participants using models inspired by Bayesian models of cognition. We show that subsets of predictions chosen based on their belief update strategies lie on a Pareto frontier between accuracy and risk, mediated by social learning. We also observe that social learning led to superior accuracy during one of our rounds that occurred during the high market uncertainty of the Brexit vote.     

Dual‐wavelength optical parametric oscillator using antiresonant ring interferometer

A novel technique for coupling of two resonant optical cavities using an antiresonant ring (ARR) interferometer is reported. By deploying two synchronously‐pumped femtosecond optical parametric oscillators (OPOs), it is shown that the use of an ARR can provide an intracavity common path for the two oscillating fields, but without gain coupling between the two nonlinear media. The new technique permits the generation of two signal (idler) wavelengths, which can be independently and arbitrarily varied across the OPO tuning range. The absence of gain coupling also enables unrestricted and uninterrupted tuning through wavelength degeneracy at any arbitrary point within the OPO tuning range. It is shown that signal wavelength pairs tunable across 1500–1580 nm, corresponding to a frequency separation from ∼ 10 THz down to exact degeneracy, can be generated from the coupled OPOs, limited only by the reflectivity of the available mirrors.     

Computational modelling of blood flow in side arterial branches after stenting of cerebral aneurysms

The major concern with the use of stents as flow diverters for the treatment of intracranial aneurysms is the potential occlusion of a perforating artery or other side branches which can cause ischemic strokes. This article presents image-based patient-specific models of stented cerebral aneurysms in which a small side artery has been jailed by the stent mesh. The results indicate that, because of the large resistances of the distal vascular beds which dominate the flow divisions among the different arterial branches, the flow reduction in jailed side branches is quite small even when a large percentage of the inlet area of these branches has been blocked. This suggests that unless the side branch is completely occluded, it will likely maintain its normal blood flow. Although this conclusion eases the concern of stenting cerebral aneurysms, a complete occlusion can still be caused depending on the conformability characteristics of the stents.     

Anodic behaviour of 2-mercaptoethanol at a mercury electrode

The anodic processes which occur at the mercury electrode in 2-mercaptoethanol solutions are studied by various polarographic techniques (d.c., a.c. and differential pulse), controlled-potential coulometry, cyclic voltammetry and differential capacity curves. Two steps are distinguished in the process: a one-electron charge transfer and a dismutation step leading to the formation of a mercury(II) mercaptide. The final product is isolated and analyzed. Differential-pulse polarography can be used to determine ?10^?4 M 2-mercaptoethanol with a limit of M.     

Alkylation of phenol with alcohols on an aluminium orthophosphate-alumina system as catalyst

The results obtained in the alkylation of phenol in gas phase with different alcohols on an aluminium orthophosphate-alumina system of Kearby type are presented. We conclude that an O-alkylation coexists with a C-alkylation and that the alkylating ability of the alcohols decreases for higher and more branched hydrocarbon chains. Influences of temperature and space time are also discussed.

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Morphologic and kinetic study of an epoxy-poly(ethyleneoxide) system. The fluorescence to predict miscibility

The kinetic of the curing process in the ethylenediamine (EDA)-poly (bisphenol A-co-epichlorohydrin) glycidyl end-capped (DGEBA) mixture modified with poly(ethylene oxide) (PEO) was studied. The epoxy component was labeled with a fluorescence group (dansyl) treating the DGEBA with the reactive dansyl derivative DNS-EDA. Dynamic DSC experiments were carried out and from their results the effect of the PEO composition on the epoxy curing was discussed. Furthermore, the effect of cure temperature and PEO composition on the morphology and crystallinity of the blend were studied as well. The morphologic study was carried out using complementarily optical transmission (TOM) and epifluorescence (EFM) microscopy. It was observed that: i) the addition of a non-reactive thermoplastic leads to a dilution effect of the reactive groups and therefore a decrease of the epoxy amine reaction rate; ii) the PEO composition does not seem to affect the non catalyzed process of the epoxy curing, while an increase in the PEO fraction within the epoxy/PEO mixture seems to change the mechanism of the cure reaction; iii) dynamic DSC scans, TOM and EFM images and steady state fluorescence spectra of the cured samples suggest that when the curing temperature increases there is an increase in the miscibility between PEO and the epoxy-amine reaction mixture; and iv) a reduction in the PEO/cured epoxy miscibility as the fraction of PEO increases was observed.     

Synthesis and characterization of Pd(II) Complexes with bis-pyridinium and isoquinolinium N-ylides: moderate C-H...O=C intramolecular hydrogen bonds as source of conformational preferences

The bis(N-ylide) Pd(II) complexes cis-[PdX2[eta2-[C(H)NCxHy]2CO]] (X=I, NCxHy=NC5H5, 2a; X=Br, NCxHy=NC5H5 and NC5H3-2,3-Me2, 2c, isoquinolinium NC9H7, 2d) have been prepared by reaction of the corresponding bis-pyridinium salts with Pd(OAc)2 (1:1 molar ratio). Compounds 2 react with AgClO4 and Tl(acac) (1:1:1 molar ratio) to give the acetylacetonato derivatives [Pd(acac-O,O'[eta2-[C(H)NCxHy]2CO]]ClO4 (3a, c, d). In compounds 2 and 3, the bis-ylide is bonded as a C,C-chelate ligand through the two ylidic Calpha atoms. The reaction is stereoselective, and only one diastereoisomer is observed (meso form, RS/SR). The origin of the observed stereoselectivity lies with the establishment of intramolecular C-H...O=C hydrogen bonds between the ortho protons of the pyridine or isoquinoline fragments and the carbonyl oxygen, as it has been shown by density functional theory (DFT) calculations (B3LYP level) and Bader analysis of the electron density on model pyridinium ylides. Despite the inherent weakness of the C-H...O=C bonds, the results show that in these N-ylides the hydrogen bonds are stronger than expected and should be classified as moderate H bonds.     

Influence of the radical size on the Ca + ROH → CaOH + R (R=CH3, C2H5 and C3H7) reaction cross section

Absolute values of the reaction cross section, σ_R, for the title reaction family have been measured by chemiluminescence emission under beam-gas conditions. The σ_R values diminish as the radical group R increases in size, showing an important overall steric effect. These results are discussed in the light of simple models for reaction stereodynamics.     

Relationship between torsional angles and ring-puckering coordinates

A relationship between torsional angles and ring puckering coordinates, applicable to any puckered ring, is deduced assuming infinitesimal displacements from a planar reference conformation. For equilateral polygons there is only one maximum torsion angle θ_m and one phase angle φ_m for each value of m, whereas for non-equilateral polygons there is one maximum θ_m^j,j+1 and a correction, ?_m^j,j+1, to be applied to the phase angle φ_m for each torsion angle θ_j,j+1. The resulting expressions for equilateral pentagons and hexagons are equivalent to the empirical ones proposed previously.