Multilayer Aggregation with Statistical Validation: Application to Investor Networks

Multilayer networks are attracting growing attention in many fields, including finance. In this paper, we develop a new tractable procedure for multilayer aggregation based on statistical validation, which we apply to investor networks. Moreover, we propose two other improvements to their analysis: transaction bootstrapping and investor categorization. The aggregation procedure can be used to integrate security-wise and time-wise information about investor trading networks, but it is not limited to finance. In fact, it can be used for different applications, such as gene, transportation, and social networks, were they inferred or observable. Additionally, in the investor network inference, we use transaction bootstrapping for better statistical validation. Investor categorization allows for constant size networks and having more observations for each node, which is important in the inference especially for less liquid securities. Furthermore, we observe that the window size used for averaging has a substantial effect on the number of inferred relationships. We apply this procedure by analyzing a unique data set of Finnish shareholders during the period 2004-2009. We find that households in the capital have high centrality in investor networks, which, under the theory of information channels in investor networks suggests that they are well-informed investors

The hydrothermal synthesis of hydrotalcite by using different partially soluble and insoluble in water mangesium and aluminium components

In this work, the influence of different partially soluble and insoluble in water Mg and Al components on the formation of hydrotalcite by using only hydrothermal synthesis was examined. Hydrothermal synthesis duration was 4, 24 and 72 h at 200°C and Mg/Al ratio was equal to 3:1. The starting materials were: 4MgCO3•Mg(OH)2•5H2O, Mg5(CO3)4•(OH)2•4H2O, Al(OH)3 and γ-Al2O3. It was determined that Mg and Al containing compounds have most important influence on the formation of hydrotalcite by hydrothermal conditions. 4MgCO3⋅Mg(OH)2⋅5H2O as raw material is not recommendable for the synthesis of hydrotalcite, because even after 24 h of isothermal curing at 200°C temperature hydrotalcite is not formed and magnesium aluminum hydroxide hydrate is dominant in the synthesis products. Besides, initial magnesium containing component is decomposed into magnesium carbonate and hydroxide. It was examined that hydrotalcite is formed already after 4 h of hydrothermal synthesis at 200°C temperature when Mg/Al molar ratio is equal to 3:1 in the Mg5(CO3)4•(OH)2•4H2O - γ-Al2O3/ Al(OH)3 - H2O system. However, together with this compound a fair amount of an intermediate compounds (boehmite and magnesium carbonate) are formed. The duration of isothermal curing determines the formation of a hexagonal plates which are characteristic to hydrotalcite

Facebook drives behavior of passive households in stock markets

Recent studies using data on social media and stock markets have mainly focused on predicting stock returns. Instead of predicting stock price movements, we examine the relation between Facebook data and investors' decision making in stock markets with a unique data on investors' transactions on Nokia. We find that the decisions to buy versus sell are associated with Facebook data especially for passive households and also for nonprofit organizations. At the same time, it seems that more sophisticated investors---financial and insurance institutions---are behaving independently from Facebook activities.Comment: This paper is forthcoming in Finance Research Letter

Aqueous-Based Synthesis of Photocatalytic Copper Sulfide Using Sulfur Waste as Sulfurizing Agent

Most of the copper sulfide synthetic approaches developed until now are still facing issues in their procedure, such as long synthesis duration, high energetic consumption, and high implementation costs. This publication reports a facile and sustainable approach for synthesizing copper sulfides on a large scale. In particular, an industrial by-product of sulfur waste was used as a sulfurizing agent for copper sulfide synthesis in a water medium. The reaction was performed in the hydrothermal environment by following a novel proposed mechanism of copper sulfide formation. The investigation of morphological and optical properties revealed that the target products obtained by using waste possess the resembling properties as the ones synthesized from the most conventional sulfurizing agent. Since the determined band gap of synthesis products varied from 1.72 to 1.81 eV, the photocatalytic properties, triggered under visible light irradiation, were also investigated by degrading the methylene blue as a model pollutant. Importantly, the degradation efficiency of the copper sulfide synthesized from sulfur waste was equivalent to a sample obtained from a reference sulfurizing agent since the value for both samples was 96% in 180 min. This very simple synthetic approach opens up a new way for large-scale sustainable production of visible-light-driven photocatalysts for water purification from organic pollutants

Influence of SiO2 crystallinity and impurities on the reactivity of lime-silica mixtures

Several industrial by-products (Hi-Silica, thermal silica densified) were characterized from the chemical and mineral viewpoint and investigated their interactions with portlandite at 180 and 200 oC. The molar ratio of primary mixture was CaO/SiO2 = 0.66. The duration of the reaction varies from 24 to 168 hours. The phase composition and properties of calcium silicate hydrates is strongly affected by crystallinity and impurities in SiO2. It was determined that silica fume – Hi-Sil contains a large quantity of absorbed water which retarded the reaction between lime and SiO2. Low-base calcium silicate hydrates form more heavily comparing with pure system. Carbon impurities in silica thermal densified influences reactivity of initial mixture and impede reaction between Ca2+ and Si4+ ions. It was found that reactivity of silica thermal densified significantly increased after burning it at 900 oC and became suitable as raw material for the synthesis of calcium silicate hydrates. Meanwhile, in the lime–quartz– H2O system, due to low quartz solubility rate even in 168 hours of synthesis at 200 oC the main products are 1.13 nm tobermorite and xonotlite. Obtained results were confirmed by XRD, DSC, IR and SEM analysis methods

The Effect of Synthetic Hydrated Calcium Aluminate Additive on the Hydration Properties of OPC

The effect of synthetic CAH (130°C; 8 h; CaO/(SiO2 + Al2O3) = 0.55; Al2O3/(SiO2 + Al2O3) = 0.1, 0.15) with different crystallinity on the hydration kinetics of OPC at early stages of hydration was investigated. Also, the formation mechanism of compounds during OPC hydration was highlighted. It was determined that the synthetic CAH accelerated the initial reaction and shortened the induction period. Also, the second and third exothermic reactions begun earlier, and, during the latter reaction, the higher values of the heat flow were obtained in comparison with pure OPC samples. At later stages of hydration, synthetic CAH affect the OPC hydration as the usual pozzolanic additives; moreover, the larger values of cumulative heat were reached. It should be noted that the nature of synthetic CAH samples accelerated the dissolution of gypsum and stimulates the earliest C3S hydration

Sustainable PHBV/CuS Composite Obtained from Waste Valorization for Wastewater Purification by Visible Light-Activated Photocatalytic Activity

The persistency of antimicrobial compounds in the water cycle accelerates the issue of antimicrobial resistance. Therefore, effective wastewater remediation approaches, which can be implemented on a large scale, are urgently required. This study aims at preparing a sustainable organic/inorganic composite material that can photo-catalyze the degradation of organic pollutants in wastewater by using visible light. Specifically, films and porous composites are composed of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) as supporting material, and copper sulfide (CuS) as active photocatalyst. It is noteworthy that the proposed composite can be fully produced from waste valorization, since PHBV is a polymer, which can be obtained by fermentation of vegetable wastes, and CuS is synthesized from industrial sulfur wastes. The produced composites show remarkable capabilities in the photodegradation of tetracycline and methylene blue, selected as model organic pollutants. Moreover, the PHBV/CuS composites can be reused multiple times with minimal loss in photocatalytic efficiency. The suggested approach is not only sustainable and cost-effective, but also solves issues occurring in the application of the photodegradation techniques currently reported, such as the consumption of fossil-based chemicals and photocatalyst removal from the purified water using with expensive procedures

Trade synchronization and social ties in stock markets

Previous studies suggest that individuals sharing similar characteristics establish stronger social relationships. This motivates us to examine what combinations of socioeconomic investor attributes are more likely to be associated with joint trading behavior. We use a unique data set on actual social ties between investors and find that similarities in investors’ age, geographical location, or length of the co-employment can affect trade synchronization under certain circumstances. Our findings have implications for the analysis of investor networks.publishedVersionPeer reviewe