AGGREGATIONAL GAUSSIANITY AND BARELY INFINITE VARIANCE IN CROP PRICES

This paper aims at reconciling two apparently contradictory empirical regularities of financial returns, namely the fact that the empirical distribution of returns tends to normality as the frequency of observation decreases (aggregational Gaussianity) combined with the fact that the conditional variance of high frequency returns seems to have a unit root, in which case the unconditional variance is infinite. We show that aggregational Gaussianity and infinite variance can coexist, provided that all the moments of the unconditional distribution whose order is less than two exist. The latter characterises the case of Integrated GARCH (IGARCH) processes. Finally, we discuss testing for aggregational Gaussianity under barely infinite varianaggregational Gausianity, infinite variance, IGARCH, crop prices

Volatility Trends and Optimal Portfolios: the Case of Agricultural Commodities

While the financial world is experiencing a crisis, the prices of most agricultural commodities have remained high, although exhibiting extreme volatilidy. Motivated by evidence showing that volatility trends are present in agricultural commodity prices, we analyze stochastic processes whose unconditional variance changes with time. This analysis suggests a semi-parametric model for capturing the trending behavior of second moments, in which these moments are polynomial-like functions of time. Based on this model, we formulate the portfolio problem faced by an investor when the variances and the covariances of the returns of the available assets are trending. Then, we obtain an approximate solution of the problem, which is based on the consistent estimation of the order of variance-covariance growth and apply it for the construction of an optimal portfolio of agricultural commodities. It is shown that the performance of this portfolio is superior to those of alternative portfolios which are formed by employing methods not accounting for the presence of volatility trends in commodity returns.

Selectivity, market timing and the morningstar star-rating system

This paper evaluates the Morningstar mutual fund ranking system. We find that indeed higher Morningstar ratings are associated with higher returns on the portfolios including respectively five-, four-, three-, two- and one-star funds only (STAR5 to STAR1). We then perform an unconditional and conditional portfolio performance evaluation. In both cases the evidence suggests that the better performance of the STAR3, STAR4 and STAR5 categories reflects superior stock selection rather than market timing abilities. Overall, the implication for the Morningstar ranking system is that this is most effective in identifying the worst-performing funds (STAR1 or STAR2) rather than the best-performing ones

INNOVATION IN EDUCATION – ADMINISTRATION AND ACTIONS OF ENCOURAGEMENT & SUPPORT IN PRIMARY EDUCATION

The promotion and implementation of educational innovations by the principal of a school organization is an important challenge that he is called upon to undertake together with the teachers of the educational organization. This paper focuses on leaders̉ actions to encourage the organization and implementation of innovations in the school organization. In the present work, an attempt is made to investigate in a sample of 104 directors of Primary Education in the Region of Western Greece issues related to the necessity and climate of introducing innovative actions in the school organization they serve, the suitability of specific models - leadership style for implementing innovations in school organization and encouraging and supporting actions to implement innovations in schools. The research highlighted the need for education through the implementation of innovative actions with an important factor being the existence of a positive communication climate through a democratic leadership style. Innovation incentives seem to be related to having a relevant master's degree, training and years of management, while in-school training as an innovation support action seems to be related to the years of management. In fact, the success of an innovative action is never guaranteed, but it depends on many factors, making the role of the principal in the school organization crucial.  Article visualizations

Digital cholangioscopy-guided electrohydraulic lithotripsy for intraepathic and difficult biliary stones with peroral and percutaneous approach. A three-year experience in a single surgical tertiary center

Background Hepatolithiasis (HL) and difficult common bile duct (CBD) stones represent a challenging condition when associated with anatomic variations due to previous surgical procedures. Several endoscopic therapeutic approaches have been proposed. A combined radiologic-endoscopic technique using electrohydraulic or laser lithotripsy under percutaneous transhepatic cholangiography (PTC) has been also described. The aim of our study is to evaluate the efficacy and safety of the SpyGlass™-guided electrohydraulic lithotripsy (SpEHL) for intrahepatic and difficult CBD stones using peroral and percutaneous approach. Materials and Methods From September 2014 to September 2017 data from symptomatic patients with intrahepatic and/or difficult CBD stones that underwent SpEHL were collected. All patients initially underwent an abdominal ultrasound exam and then magnetic resonance cholangiopancreatography (MRCP) and/or computed tomography (CT) to confirm the diagnosis, to detect the biliary stones and to evaluate anatomical abnormalities due to previous abdominal surgical operation. CT and/or MRCP results were classified according to the Tsunoda classification. ERCP was the first line treatment for difficult CBD stones and/or HL. Peroral SpEHL was performed in case of ERCP failure (stone diameter >25mm, strictures). PTC was performed in case of intrahepatic (Tsunoda class III/IV) or impacted stones associated with narrowed CBD. In these cases, percutaneous transhepatic cholangioscopy (PTCS) and SpEHL was performed. Patients with anatomic modifications due to previous surgery with a bilio-enteric anastomosis had a direct PTC approach with SpEHL. In cases of biliary anastomosis after liver transplantation a PTC approach was performed only after ERCP and SpEHL failure. The average follow-up period was 24±3.6 months. Results Complete stone clearance was achieved in 29/30 (96.6%) after a maximum of 3 consecutive procedures. 10 patients presented only difficult CBD stones (3 with Billroth type II gastrectomy), 5 with intrahepatic and CBD stones and 15 patients with only HL (9 with bilio-enteric anastomosis, 6 with biliary anastomosis due to liver transplantation). Intrahepatic or CBD strictures were observed in 12 patients and biopsies made with Spybite© biopsy forceps (histological report: 10 benign and 2 malign). 1 patient underwent surgery (left hepatectomy with no histological evidence of oncological disease) after 3 procedure failures caused by a non-dilatable left lobe biliary duct stricture. Major adverse events were: 1 (3.3%) case of massive bleeding with the need of embolization and 4 (13%) cases of mild cholangitis treated with medical therapy. Recurrence of stones was observed in 4 cases (13.7%) successfully retreated. Conclusion Peroral-SpEHL is an effective and safe rescue treatment in patients who have failed standard ERCP stone removal techniques. PTCS-SpEHL seems to be very effective in patients with altered anatomy, showing low complication and recurrence rates

EDUCATION IN UNIVERSITIES - TEACHER TRAINING AS A QUALITY FACTOR

In recent decades, the quality of education has been a matter of priority for educational systems in the European as well as in the wider international environment. It is a common feeling that the vast majority of teachers consider that they were not adequately and properly prepared during their studies in Hellenic Universities to fully perform the work of a teacher. In Hellenic universities, there are no organized training programs at any stage of the teachers' careers, except for the Pedagogical Schools where education is their primary subject. In this work, the identification and investigation of the educational needs of the teachers (scientific and laboratory assistants) of the Department of Mechanical Engineering of Technological Educational Institution of Patras, on a cognitive-academic level, a pedagogical level and a level of use - integration of new technologies in teaching, aiming to provide quality education. Also, the intention and motivations of the teachers of the department for training at all levels with the aim of their professional development are investigated. From the findings of the research, it emerged that there is a high desire for the training of young age mainly teachers with little professional and teaching experience, in a subject mainly cognitive and pedagogical and with training hours up to 50 hours, to acquire new knowledge and skills.  Article visualizations

Selectivity, Market Timing and the Morningstar Star-Rating System

This paper evaluates the Morningstar mutual fund ranking system. We find that indeed higher Morningstar ratings are associated with higher returns on the portfolios including respectively five-, four-, three-, two- and one-star funds only (STAR5 to STAR1). We then perform an unconditional and conditional portfolio performance evaluation. In both cases the evidence suggests that the better performance of the STAR3, STAR4 and STAR5 categories reflects superior stock selection rather than market timing abilities. Overall, the implication for the Morningstar ranking system is that this is most effective in identifying the worst-performing funds (STAR1 or STAR2) rather than the best-performing ones.mutual fund, Morningstar Star-Rating System, CAPM, conditional and unconditional portfolio performance evaluation

THE IMPACT OF RETAILER\u27S CENTRALIZED PURCHASING STRUCTURE ON VENDOR ORDER FULFILLMENT: A CASE STUDY ANALYSIS

To remain competitive in today\u27s market and economy, retail companies must provide products and services in the form, time and place that their consumers demand. The rise in e-commerce and improved logistics capabilities have changed how products are sold. Companies are looking to decrease costs and lead times to remain profitable as competition and consumer demands intensify. Retailers are looking to lower costs in their supply chain. Using sales data and forecasting methods, retailers are placing smaller, more frequent orders to decrease inventory and associated inventory costs throughout their network. This faster replenishment model has led to small containers becoming more common in wholesale fulfillment than large containers.Though there has been a shift in order size and frequency, there has been little change in ordering structure. Many major retailers use a centralized purchasing structure. Within the structure, there are different product categories, or departments, with buyers that place orders for the entire company. This allows for departmental expertise. Under this structure, employees from each buying department are placing multiple orders per week. This has a huge impact on vendors that supply products that fall into more than one retail category. Different orders cannot be combined so vendors could potentially receive multiple orders from the same customers that originated from different buying departments.A case study on buying strategy and structure demonstrates that a change from current retailer ordering structure with multiple buying departments to a single source of orders can decrease vendor corrugate and labor costs by 16%. This change allows the vendor to deliver the same products while using less labor and packaging materials. A company’s supply chain can be a competitive advantage for those that constantly evaluate their current systems and practices. The process of placing and fulfilling orders will remain an essential activity in the supply chain, so these processes and practices should be evaluated