Search

Numerous animal models of intervertebral disc (IVD) degeneration have been proposed in the literature. The rat caudal disc has been used in disc degeneration studies because of its low cost and simplicity. However, no consensus on the size of the needle to be used during this process has been reached, yet.This study aims to select an optimal needle size to establish a reproducible IVD degeneration model.This is a randomized, experimental trial.Cell therapy and experimental surgery of musculoskeletal system LR18SP1 Lab, The Faculty of Medicine of Sfax, Tunisia.The validity was verified by magnetic resonance imaging (MRI), histological, and immunohistochemical examinations.The MRI, histological, and immunohistochemical examinations showed that a disc that is perforated with a 21G needle degenerated acutely one week after the surgery, while a 29G needle puncture failed to develop disc degeneration. A 25G needle induced progressive degeneration in the IVD.This study was not very long (6 weeks).We conclude that the size of the needle affects the onset and the progression of disc degeneration; a larger needle size leads to a more extended histological and radiographic degeneration within the IVD and in a relatively short time. Therefore, a 21G needle is an optimal choice to induce rapid degeneration in rats' caudal discs. However, the use of a 29G needle failed to establish a degenerative IVD model, which makes it ideal for IVD injection of drugs, plasmids, and growth factors. A 25G needle may be used to induce gradual degeneration.

PurposeThis paper analyzes the connectedness with network among the major cryptocurrencies, the G7 stock indexes and the gold price over the coronavirus disease 2019 (COVID-19) pandemic period, in 2020.Design/methodology/approachThis study used a multivariate approach proposed by Diebold and Yilmaz (2009, 2012 and 2014).FindingsFor a stock index portfolio, the results of static connectedness showed a higher independence between the stock markets during the COVID-19 crisis. It is worth noting that in general, cryptocurrencies are diversifiers for a stock index portfolio, which enable to reduce volatility especially in the crisis period. Dynamic connectedness results do not significantly differ from those of the static connectedness, the authors just mention that the Bitcoin Gold becomes a net receiver. The scope of connectedness was maintained after the shock for most of the cryptocurrencies, except for the Dash and the Bitcoin Gold, which joined a previous level. In fact, the Bitcoin has always been the biggest net transmitter of volatility connectedness or spillovers during the crisis period. Maker is the biggest net-receiver of volatility from the global system. As for gold, the authors notice that it has remained a net receiver with a significant increase in the network reception during the crisis period, which confirms its safe haven.Originality/valueOverall, the authors conclude that connectedness is shown to be conditional on the extent of economic and financial uncertainties marked by the propagation of the coronavirus while the Bitcoin Gold and Litecoin are the least receivers, leading to the conclusion that they can be diversifiers.

The development of Islamic finance in the Maghreb countries faces today the question of the existence of a potential pool of customers. In fact, the population is apparently very sensitive to the religious argument regarding savings and financing. In addition, the population is still underbanked. The banking rate is only 30% on average in the region. The articulation between Islamic finance and retail banking in the Maghreb is therefore obvious. Some Islamic Gulf banks could perfectly consider geographic diversification and thus penetrate the retail banking market in the Maghreb countries. However, the establishment of Islamic finance in the Maghreb should be very gradual. The Maghreb banking authorities will have to find a balance between the social demand for this kind of banks and the competition of these entrants in territories already occupied by conventional local banks which are not very aggressive. We first present an overview of Islamic finance in each of the Maghreb countries. We then examine the determinants of demand for Islamic banking services, taking Mauritania as an example. The latter, whose official name is "Islamic Republic of Mauritania" is undoubtedly one of the most advanced countries in the Maghreb in this area. Classification JEL : G21, O16, O55.

We analyze the impact of macroeconomic news surprises for Canada, the Euro area, Japan, the UK, and the US relating to returns and volatility for West Texas Intermediate and Brent crude oil futures. We look at futures markets, since they are widely believed to predict spot market movements. We also investigate the possibility of an asymmetric impact of good and bad macroeconomic news surprises, as well as the role of economic uncertainty for these economies in affecting oil futures market movements. Two major conclusions can de drawn from our study: (a) macroeconomic surprises, as well as uncertainties for other economies (over and above that of the US) were found to be important in driving oil futures, with the effect of these other economies being relatively stronger than the US in some instances; and (b) there is strong evidence of asymmetric effects, especially for volatility.

Purpose The purpose of this paper is to investigate whether the interaction between sentiments and past prices can lead to higher abnormal profit in futures markets. Such examinations allow the authors to relate the paper to the debate that focuses on examining the behavior of different types of traders in futures market, and who among these traders destabilize the markets. Design/methodology/approach First, the authors develop new dynamic strategies in US futures market that combine sentiment by type of traders based on trader position provided by the Disaggregated Commitments of Traders with short-term contrarian signals. Next, the authors adjust the abnormal profits to the CAPM model and Miffre and Rallis’s (2007) model. Finally, the authors use the Du (2012) decomposition methodology. Findings The main findings are that the abnormal profit is more pronounced when the authors combine past returns with lagged high producer/merchant/processor/user or low managed money sentiment. The results from swap dealer or other reportable groups show that there is no pervasive directional relation between their sentiment and contrarian profit. A further investigation of the sources of abnormal profits demonstrates that these profits survive even after the adjustment of obtained return to risk. Instead, these profits are mainly due to the overreaction to the news by irrational traders. Originality/value Based on behavioral finance theories, the authors conclude that producer, merchant, processor and user behave like irrational traders, while managed money traders behave like rational ones. Given that current regulatory proposes the limitation of speculation, the policy implications of these results are important. Therefore, these findings suggest that policy distinctions on trading motives may be more challenging to construct than ever.

Juncal Cunado gratefully acknowledges financial support from Ministerio de Economia, Industria y Competitividad (ECO2017-83183-R).

In this paper, we use data from the DCOT report to test the usefulness of trader-position-based sentiment in explaining returns and volatility in 13 major futures markets. Our main findings are that shifts in Producer/Merchant/Processor/User sentiment are positively related to price volatility in the majority of the tested markets and tend to destabilize these markets, while shifts in Money Manager sentiment tend to stabilize futures markets by reducing market volatility. we further investigate the relevance of behavioral finance and noise trader theory in futures markets by allowing for asymmetry in the variance equation of the used EGARCH model. We find that Producer/Merchant/Processor/User entities may behave like irrational investors and thus destabilize markets as they become bullish, while Money Managers may behave like rational traders and then tend to counterbalance price deviations from fundamental values caused by irrational trades.

Our study adds to the literature by providing initial evidence on the interaction between short-horizon return predictability and investors’ sentiment by traders’ types on US commodity futures market. We find that the short-term contrarian profit is more associated with an increase rather than a decrease in hedgers’ sentiment. However, the interaction between lagged return and past change in speculators’ sentiment illustrates that the short-term contrarian profit is more associated with a decrease rather than an increase in sentiment. Based on behavioral finance theories, we conclude that hedgers behave like irrational traders while speculators behave like rational ones. Using Chou et al. (2007) decomposition, our results confirm the obtained relations between change in trader's sentiment and the overreaction. By expanding this decomposition, we find that the winners’ portfolio tends to more overreact with futures specific information. Also, the cross-autocorrelation between winners and losers and between losers and winners can represent another source of contrarian profits.

This paper analyses the connectedness network for commercial traders’ sentiment across agriculture, energy, metals and livestock futures markets. The findings find that: (a) producer/merchant/processor/user (PMPU) in agricultural and energy markets are mainly engaged in cross-hedging in the futures market, and most of them would avoid risks in these markets by operating in the metal markets, which can be considered safe for PMPU traders, and that the cross-hedging strategies may play the role of PMPU sentiment spillover across futures markets; (b) as index traders, the swap dealers operate more in two markets, namely between the agricultural and metal markets, or between the agricultural and energy markets; (c) the influence of geopolitical risks in some countries can affect the stability of energy markets, which in turn can cause PMPU system-wide connectedness.

PurposeMany factors like CEO (“the chief executive officer”) decision can influence efficiency and productivity in insurance firms. This paper seeks to address this issue.Design/methodology/approachTo test the effect of CEO power on the efficiency and the productivity of the European insurance industries, the authors use the flexible Fourier cost function and they decompose the total factor productivity growth.FindingsThe result shows that after the integration of the CEO power score, not only efficiency scores in each country have changed, but also the order of non‐life insurance systems. Also, the CEO power influences the growth of productivity and an optimal power of the CEO can allow the insurance firm to be more productive and more efficient.Originality/valueIn this paper the authors model a new cost function in which they include the CEO power score; they also decompose the total factor of productivity in which they include the effect of the growth in the CEO power score.

Polypropylene/titanium dioxide (PP/TiO2) nanocomposites can be prepared using a novel method based on the hydrolysis–condensation reactions (sol–gel method) of titanium alkoxide inorganic precursors that have been premixed with polypropylene under molten conditions. The resultant nanocomposites were characterised by transmission electronic microscopy (TEM), X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). These techniques showed the formation of the titanium oxi-hydroxide chemical structure (TixOy(OH)z) with a diameter of approximately 10 nm in the polymer matrix. Furthermore, a condensation degree of around 17% was determined using XPS analysis. The antibacterial activity was tested according to the JIS Z 2801:2000 standard with Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in the absence of light. Correlations between the microstructure and the chemical composition of PP/TiO2 nanocomposites and the antibacterial properties of these nanocomposites were discussed. The structure of titanium oxi-hydroxide derivative particles (TixOy(OH)z) within the polypropylene matrix has been shown to impact strongly on the antibacterial properties in comparison with the results obtained with a dispersion of anatase titanium dioxide into the PP.

The paper describes different studies linked to extrusion problems encountered during production in the cable industry. Extrusion simulation or rheology analysis can be used to understand the origin of the problems in cable manufacturing and to set up durable industrial solutions by selecting the appropriate compounds, optimizing screw profiles, modifying the geometries of the tooling or adapting the processing conditions. Our investigations based on the COMPUPLAST® Virtual Extrusion Laboratory™ software, have brought large understanding and these investigations are cheaper and faster alternatives to real experiments (trials/errors) when analyzing and optimizing extrusion processes. Three examples are presented in the paper.

The effects of twin-screw extrusion processing conditions upon the formation of polypropylene/titanium dioxide (PP/TiO2) nanocomposites are investigated. To prepare PP/TiO2 nanocomposites by limiting the problem of filler dispersion at the nanoscale, an original method was developed based on the creation of TiO2 through hydrolysis–condensation reactions (sol–gel method) of titanium n-butoxide precursor during PP extrusion. The feed rate, the screw speed, and the amount of inorganic precursor were varied independently. The conversion rate of precursor as a function of process parameters was quantified by gas chromatography and mass spectroscopy combined techniques through the assessment of the alcohol formed. The effects of processing conditions on the development of the sol–gel reaction have also been investigated by using numerical simulations. The comparison between experimental and theoretical results shows that this simulation approach is relevant to predict the conversion of the inorganic precursor to TiO2 through hydrolysis–condensation reactions in molten PP. © 2011 American Institute of Chemical Engineers AIChE J, 2011

International audience; Study of hydrolysis-condensation reactions of titanium n-butoxide precursor into an unusual medium and non-classical conditions was carried out. Kinetic data were reached in a temperature range of 130-250A degrees C from FTIR, TGA-GC-MS and rheological techniques. These results were obtained into an alkane dispersing medium, (Squalane: 2,6,10,15,19,23-hexamethyltetracosane), and compared to the ones determined from the hydrolysis-condensation reactions of the titanium dioxide precursor carried in molten polypropylene (PP) during extrusion process. The transposition of these knowledge to the in situ synthesis of titanium dioxide in molten PP matrix by reactive extrusion lead to the formation of a fine dispersion of few nanometer diameter (similar to 5 nm) of TiO2 particles. Finally, the viscoelastic behaviour of the nanocomposite has been strongly altered in the terminal relaxation zone as permanent secondary plateau (solid-like behavior), attributed to some fractal arrangement of the inorganic domains was observed.

PP/TiO2 nanocomposites were prepared from an original method based on the hydrolysis-condensation (sal-gel method) reactions of titanium alkoxide inorganic precursor premixed with polypropylene (PP) under molten conditions. Nanocomposites with a mean diameter of primary particles lower than 5 nm were then prepared. The TiO2 particle dispersion in the PP matrix was characterized over a wide length scale from the combination of small angle X-ray scattering, transmission electron microscopy, and linear viscoelasticty of molten nanocomposites. As a result, a fractal structure of these particles was highlighted at the highest concentration (phi(r) >= 0.014) with a characteristic aggregation size d(aggr) approximate to 130 nm. The relationships between fractal structure and linear viscoelastic have been discussed from the main works of the literature on the reinforcement of nanocomposites. The drastic alteration of the terminal relaxation zone (solid-like behavior) is correlated to the formation of an aggregate-particle network. The study of the nonlinear viscoelastic behavior (Payne effect) agrees qualitatively with this reinforcement mechanism. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1213-1222, 2010

Poly(ethylene-co-vinyl acetate) (EVA)/poly(butylene terephthalate) copolymers were synthesized by the in situ polymerization of cyclic butylene terephthalate monomer (cBT) in the presence of molten EVA copolymer. Titanium phenoxide Ti(OPh)(4) which leads to the highest degree of grafting compared to the more classical titanium system was used as the initiator for the ring-opening polymerization of the cBT monomer. The corresponding copolymer was characterized fully by H-1 NMR after selective extraction from the blend. As a result, a maximum of 11.3 wt% of EVA-g-PBT copolymer was synthesized by this method. Examination of morphology by transmission electronic microscopy (TEM) showed a fine dispersion of PBT phase with size ranging from 100 to 500 nm in diameter. This gave evidence for a crown structure of the PBT phase that is coated by EVA-g-PBT copolymer. Finally, theological and mechanical studies highlighted a specific behaviour of this material with improved mechanical properties at room temperature. (C) 2009 Elsevier Ltd. All rights reserved.