Conditional Correlations in the Returns on Oil Companies Stock Prices and Their Determinants

The identification of the forces that drive stock returns and the dynamics of their associated volatilities is a major concern in empirical economics and finance. This analysis is particularly relevant for determining optimal hedging strategies based on whether shocks to the volatilities of returns of oil companies stock prices, relevant stock market indexes and oil spot and futures prices are high or low, and positively or negatively correlated. This paper investigates the correlations of volatilities in the stock price returns and their determinants for the most important integrated oil companies, namely Bp (BP), Chevron-Texaco (CVX), Eni (ENI), Exxon-Mobil (XOM), Royal Dutch (RD) and Total-Fina Elf (TFE). We measure the actual co-risk in stock returns and their determinants “within” and “between” the different oil companies, using multivariate cointegration techniques in modelling the conditional mean, as well as multivariate GARCH models for the conditional variances. We focus first on the determinants of the market value of each company using the cointegrated VAR/VECM methodology. Then we specifiy the conditional variances of VECM residuals with the Constant Conditional Correlation (CCC) multivariate GARCH model of Bollerslev (1990) and the Dynamic Conditional Correlation (DCC) multivariate GARCH model of Engle (2002). The “within” and “between” DCC indicate low to high/extreme interdependence between the volatilities of companies’ stock returns and the relevant stock market indexes or Brent oil prices.Constant conditional correlations, Dynamic conditional correlations, Multivariate GARCH models, Stock price indexes, Brent oil prices, Spot and futures prices, Multivariate cointegration, VECM

Day-case management of chronic suppurative otitis media with cholesteatoma with canal wall down technique surgery: long-term follow-up

The overall number of day-case otologic surgery cases is increasing; however, there is limited experience about performing canal wall down tympanoplasty in patients with chronic suppurative otitis media with cholesteatoma in this setting. The objective of this study was to assess the success of this technique as day-case surgery in terms of results and complications over an 8-year follow up period. We included in this study 42 patients undergoing canal wall down technique tympanoplasty surgery for chronic suppurative otitis media with cholesteatoma performed as day cases during a 2-year period. 30 cases (71.4%) were discharged on the day of surgery, whereas 12 cases (28.6%) were hospitalized and discharged the day after. The principal reasons for failure of discharge on the day of surgery were asthenia (6 cases), vertigo and asthenia (4 cases), undetermined (2 cases). Based on our experience, with a proper preoperative selection, assessment and screening of the patients, mastoidectomy with timpanoplasty for chronic suppurative otitis media with cholesteatoma can be carried out in a day surgery setting with no significant effects on effectiveness of surgery, post-operative symptoms and relapse of disease even in the long term

The innervation of human muscularis mucosae: an ultrastructural study

The muscularis mucosae, a thin band of smooth muscle located at the base of the gastrointestinal mucosa, has been the topic of very few studies .The muscularis mucosae might regulate the absorptive and secretory functions of the gut through movements of the mucosal surface (1).The autonomic innervation of this tissue is almost completely unknown.Therefore we have carried out an ultrastructural study on nerve fibers of muscolaris mucosae by using archived mucosal rectal biopsies of children of different age , examined in the past for the diagnosis of neurometabolic disease and resulted negative. Nerve fibers of muscularis mucosae were unmyelinated. They contain several axons with the characteristics of intervaricose tract completely or almost surrounded by Schwann cells . Other axons in the nerve fibers appear as varicosities partly covered with Schwann cell cytoplasm or naked, and filled with vesicles and mitochondria .The vesicles in the same varicosity appear pleomorphic: small clear-core vesicles , dense -core of small diameter or less often dense-core of larger type. The membrane of muscle cells often protruded toward the varicosity . No synaptic specialization was observed.With very low frequency we found varicosities in intimate contact with the plasmalemma . Pleomorphic vesicles inside the same varicosity suggest a complex neurotransmission based on the release of classical transmitter and cotransmitters.The physiological relevance of these nerves remains unclear. Strips of longitudinal muscularis mucosae isolated from the human, guinea pig and rat colon responded with concentration-dependent contractions to the application of several spasmogens (1). In the human muscularis mucosae, neurokinin A was most potent, followed by carbachol, prostaglandin F2 and acetylcholine. These findings suggest the possibility that the muscularis mucosae is innervated by excitatory cholinergic nerves (1).On the other hand in oesophagus exogenously applied adrenaline inhibited spontaneous activities of the muscularis mucosae motor activity. Adrenergic nerves might inhibit spontaneous motility via the inhibition of cholinergic neurotransmission. VIP- , NPY-, CGRP- and galanin-immunoreactive nerve fibers were observed in the human esophageal muscularis mucosae but their function remains unknown (2)

Abrasive waterjet intensifier model for machine diagnostics

This paper investigates the dynamics of a waterjet plant with multiple phased single-acting plungers. An object oriented dynamic model is proposed and discussed. The simulator may be tuned to generate signals under different health conditions to train multi-fault diagnosis tools. In fact, due to the challenging pressure conditions and the aggressiveness of abrasive materials, the reliability of machine tool components is a major concern. The information throughput provided by the model is validated with respect to real-industrial data, acquired in reference cutting scenarios

A controlled, randomized clinical study to verify the efficacy and safety of a new hypertonic solution (Narlisim) in nasal congestion in adults affected by common cold

Background: Nasal congestion is the main symptom of common cold. Symptomatic treatment with nasal decongestant seems to be the only treatment option. We managed a study to assess the efficacy of Narlisim, a developed nasal spray, on nasal congestions in common cold. Materials and methods: In this study, sixty adult patients with common cold were included. Thirty patients were treated with Narlisim nasal spray, and 30 patients with isotonic nasal spray. The primary outcome was the assessment of the speed of relief of nasal congestion; the secondary outcome was the assessment of nasal congestion and nasal secretion symptoms by a 0–100% rating Visual analog score (VAS) scale on 5 items at baseline and after 5, 10, 15, 20, 25 and 30 minutes from treatment. Results: VAS score progressively reduced for all investigated symptoms in both groups; a statistically significant higher mean reduction at each time point was recorded in the study group compared to controls (p<0.001). Conclusions: Our results suggest that Narlisim may be a promising medical device to control nasal congestion and rhinitis in common cold thanks to its nasal washing, hypertonic city, and low pH and osmo protection properties

A comparison study of distribution-free multivariate SPC methods for multimode data

The data-rich environments of industrial applications lead to large amounts of correlated quality characteristics that are monitored using Multivariate Statistical Process Control (MSPC) tools. These variables usually represent heterogeneous quantities that originate from one or multiple sensors and are acquired with different sampling parameters. In this framework, any assumptions relative to the underlying statistical distribution may not be appropriate, and conventional MSPC methods may deliver unacceptable performances. In addition, in many practical applications, the process switches from one operating mode to a different one, leading to a stream of multimode data. Various nonparametric approaches have been proposed for the design of multivariate control charts, but the monitoring of multimode processes remains a challenge for most of them. In this study, we investigate the use of distribution-free MSPC methods based on statistical learning tools. In this work, we compared the kernel distance-based control chart (K-chart) based on a one-class-classification variant of support vector machines and a fuzzy neural network method based on the adaptive resonance theory. The performances of the two methods were evaluated using both Monte Carlo simulations and real industrial data. The simulated scenarios include different types of out-of-control conditions to highlight the advantages and disadvantages of the two methods. Real data acquired during a roll grinding process provide a framework for the assessment of the practical applicability of these methods in multimode industrial applications

Extrafloral-nectar based partner manipulation in plant-ant relationship

Plant–ant interactions are generally considered as mutualisms, with both parties gaining benefits from the association. It has recently emerged that some of these mutualistic associations have, however, evolved towards other forms of relationships and, in particular, that plants may manipulate their partner ants to make reciprocation more beneficial, thereby stabilizing the mutualism. Focusing on plants bearing extrafloral nectaries, we review recent studies and address three key questions: (i) how can plants attract potential partners and maintain their services; (ii) are there compounds in extrafloral nectar that could mediate partner manipulation; and (iii) are ants susceptible to such compounds? After reviewing the current knowledge on plant–ant associations, we propose a possible scenario where plant-derived chemicals, such as secondary metabolites, known to have an impact on animal brain, could have evolved in plants to attract and manipulate ant behaviour. This new viewpoint would place plant–animal interaction in a different ecological context, opening new ecological and neurobiological perspectives of drug seeking and use

Nectar in plant-insect mutualistic relationships: from food reward to partner manipulation

It has been known for centuries that floral and extrafloral nectar secreted by plants attracts and rewards animals. Extrafloral nectar is involved in so-called indirect defence by attracting animals (generally ants) that prey on herbivores, or by discouraging herbivores from feeding on the plant. Floral nectar is presented inside the flower close to the reproductive organs and rewards animals that perform pollination while visiting the flower. In both cases nectar is a source of carbon and nitrogen compounds that feed animals, the most abundant solutes being sugars and amino acids. Plant-animal relationships involving the two types of nectar have therefore been used for a long time as text-book examples of symmetric mutualism: services provided by animals to plants in exchange for food provided by plants to animals. Cheating (or deception or exploitation), namely obtaining the reward/service without returning any counterpart, is however well known in mutualistic relationships, since the interacting partners have conflicting interests and selection may favour cheating strategies. A more subtle way of exploiting mutualism was recently highlighted. It implies the evolution of strategies to maximize the benefits obtained by one partner while still providing the reward/service to the other partner. Several substances other than sugars and amino acids have been found in nectar and some affect the foraging behaviour of insects and potentially increase the benefits to the plant. Such substances can be considered plant cues to exploit mutualism. Recent evidence motivated some authors to use the term “manipulation” of animals by plants in nectar-mediated mutualistic relationships. This review highlights the recent background of the “manipulation” hypothesis, discussing it in the framework of new ecological and evolutionary scenarios in plant-animal interactions, as a stimulus for future research