Which firms survive in a crisis? Corporate dynamics in Greece 2001-2014

Using a panel dataset of more than 40,000 Greek corporations over the period 2001- 2014, the paper examines how their size measured by past turnover affects survival prospects and turnover growth. The analysis is carried out along three dimensions: (a) time-wise, by looking at the dynamics before and after the crisis in 2010; (b) sector-wise, by grouping firms in six areas of economic activity, namely manufacturing, construction, trade, recreation, real-estate, and the combined sectors of transport & communications; (c) region-wise, by examining firms in Northern Greece, the wider Attiki region, and the rest of the country. Other firm’s characteristics like age, market share, leverage, and fixed asset ratio are also used as explanatory variables in the econometric estimation. Investigation takes place in the framework known in the literature as the Gibrat’s Law, according to which market turnover is a random walk process and larger-size firms belong to the same population with smaller ones. Our findings suggest that in Greece larger-size firms were, in general, more likely to survive in the market than smaller ones and this relative advantage grew stronger during the crisis. Focusing on sectors, it is established that large companies in the manufacturing sector are by far more robust over the cycle, while those in the Real Estate and construction sectors manifest the highest extinction rate. Moreover, the rate of turnover growth for those firms survived is found to be negatively associated with their size, thus not confirming Gibrat’s Law in Greece

Testing optically stimulated luminescence dating on sand-sized quartz of deltaic deposits from the Sperchios delta plain, central Greece

This study reports on the first investigation into the potential of luminescence dating to establish a chronological framework for the depositional sequences of the Sperchios delta plain, central Greece. A series of three borehole cores (20 m deep) and two shallow cores (4 m deep), from across the delta plain, were extracted, and samples were collected for luminescence dating. The luminescence ages of sand-sized quartz grains were obtained from small aliquots of quartz, using the Single-Aliquot Regenerative-dose (SAR) protocol. The equivalent dose determination included a series of tests and the selection of the Minimum Age Model (MAM) as the most appropriate statistical model. This made it possible to confirm the applicability of quartz Optically Stimulated Luminescence (OSL) dating to establish absolute chronology for deltaic sediments from the Sperchios delta plain.Testing age results of the five cores showed that the deltaic sediments were deposited during the Holocene. A relatively rapid deposition is implied for the top ∼14 m possibly as a result of the deceleration in the rate of the sea-level rise and the transition to terrestrial conditions, while on the deeper parts, the reduced sedimentation rate may indicate a lagoonal or coastal environment

Electrical Brain Responses to an Auditory Illusion and the Impact of Musical Expertise

The presentation of two sinusoidal tones, one to each ear, with a slight frequency mismatch yields an auditory illusion of a beating frequency equal to the frequency difference between the two tones; this is known as binaural beat (BB). The effect of brief BB stimulation on scalp EEG is not conclusively demonstrated. Further, no studies have examined the impact of musical training associated with BB stimulation, yet musicians' brains are often associated with enhanced auditory processing. In this study, we analysed EEG brain responses from two groups, musicians and non-musicians, when stimulated by short presentation (1 min) of binaural beats with beat frequency varying from 1 Hz to 48 Hz. We focused our analysis on alpha and gamma band EEG signals, and they were analysed in terms of spectral power, and functional connectivity as measured by two phase synchrony based measures, phase locking value and phase lag index. Finally, these measures were used to characterize the degree of centrality, segregation and integration of the functional brain network. We found that beat frequencies belonging to alpha band produced the most significant steady-state responses across groups. Further, processing of low frequency (delta, theta, alpha) binaural beats had significant impact on cortical network patterns in the alpha band oscillations. Altogether these results provide a neurophysiological account of cortical responses to BB stimulation at varying frequencies, and demonstrate a modulation of cortico-cortical connectivity in musicians' brains, and further suggest a kind of neuronal entrainment of a linear and nonlinear relationship to the beating frequencies

Underinvestment and Unemployment: The Double Hazard in the Euro Area

An alarming legacy of the austerity programs in the euro area is the vast disinvestment that has taken place over the recent years, and especially so in the peripheral economies. Unless it is quickly reversed, disinvestment not only hinders long-term growth but also undermines the prospects of a gradual reduction of unemployment and risks further imbalances in, and threats to, the monetary union. Combining a neoclassical Diamond model with labour market imperfections, the paper shows that unemployment is a function of capital investment under either CES or Cobb-Douglas production functions. A cross-section estimate for the euro area economies confirms the theoretical findings

Using Bio-inspired Intelligence for Web Opinion Mining

This work proposes a bio-inspired based methodology in order to extract and evaluate user’s web texts / posts. To validate the methodology, a dataset is constructed using real data arising from Greek fora. The obtained results are compared with a commonly used machine learning technique (decision trees- C4.5 algorithm). The bio-inspired algorithm (namely the hybrid PSO/ACO2 algorithm) achieved average classification accuracy 90.59 % in a 10 fold cross validation experiment, outperforming the C4.5 algorithm (83.66%). The proposed methodology could be easily integrated with a decision support system providing services in the fields of e-commerce or e-government in order to help merchants acquire customer satisfaction or public administrators capture common understanding

Design of a signature file method that accounts for non-uniform occurrence and query frequencies

Summarization: In this paper we study a variation of the signature file access method for text and attribute retrieval. According to this method, the documents (or records) are stored sequentially in the "text file". Abstractions ("signatures") of the documents (or records) are stored in the "signature file". The latter serves as a filter on retrieval: It helps discarding a large number of nonqualifying documents. We pro-pose a signature extraction method that takes into account the query and occurrence frequencies, thus achieving better performance. The model we present is general enough, so that results can be applied not only for text retrieval but also for files with formatted data.Παρουσιάστηκε στο: 11th international conference on Very Large Data Base

Description and performance analysis of signature file methods

Summarization: Signature files have attracted a lot of interest as an access method for text and specifically for messages in the office environment. Messages are stored sequentially in the message file, whereas their hash-coded abstractions (signatures) are stored sequentially in the signature file. To answer a query, the signature file is examined first, and many nonqualifying messages are immediately rejected. In this paper we examine the problem of designing signature extraction methods and studying their performance. We describe two old methods, generalize another one, and propose a new method and its variation. We provide exact and approximate formulas for the dependency between the false drop probability and the signature size for all the methods, and we show that the proposed method (VBC) achieves approximately ten times smaller false drop probability than the old methods, whereas it is well suited for collections of documents with variable document sizes.Presented on: ACM Transactions on Information and System Securit