GARCH models with leverage effect : differences and similarities

In this paper, we compare the statistical properties of some of the most popular GARCH models with leverage effect when their parameters satisfy the positivity, stationarity and nite fourth order moment restrictions. We show that the EGARCH specication is the most exible while the GJR model may have important limitations when restricted to have nite kurtosis. On the other hand, we show empirically that the conditional standard deviations estimated by the TGARCH and EGARCH models are almost identical and very similar to those estimated by the APARCH model. However, the estimates of the QGARCH and GJR models differ among them and with respect to the other three specications.EGARCH, GJR, QGARCH, TGARCH, APARCH

l-Amino Acid Production by a Immobilized Double-Racemase Hydantoinase Process: Improvement and Comparison with a Free Protein System

Protein immobilization is proving to be an environmentally friendly strategy for manufacturing biochemicals at high yields and low production costs. This work describes the optimization of the so-called “double-racemase hydantoinase process,” a system of four enzymes used to produce optically pure l-amino acids from a racemic mixture of hydantoins. The four proteins were immobilized separately, and, based on their specific activity, the optimal whole relation was determined. The first enzyme, d,l-hydantoinase, preferably hydrolyzes d-hydantoins from d,l-hydantoins to N-carbamoyl-d-amino acids. The remaining l-hydantoins are racemized by the second enzyme, hydantoin racemase, and continue supplying substrate d-hydantoins to the first enzyme. N-carbamoyl-d-amino acid is racemized in turn to N-carbamoyl-l-amino acid by the third enzyme, carbamoyl racemase. Finally, the N-carbamoyl-l-amino acid is transformed to l-amino acid by the fourth enzyme, l-carbamoylase. Therefore, the product of one enzyme is the substrate of another. Perfect coordination of the four activities is necessary to avoid the accumulation of reaction intermediates and to achieve an adequate rate for commercial purposes. The system has shown a broad pH optimum of 7–9, with a maximum activity at 8 and an optimal temperature of 60 °C. Comparison of the immobilized system with the free protein system showed that the reaction velocity increased for the production of norvaline, norleucine, ABA, and homophenylalanine, while it decreased for l-valine and remained unchanged for l-methionine

The influence of social capital on risk-taking propensity. A study on Chinese immigrant entrepreneurs

This paper studies the influence of social capital on immigrant entrepreneurs’ risk-taking propensity. The paper has a particular focus on Chinese immigrants and also explores the effects of the so-called “guanxi”, a specific form of social capital for Chinese communities. The empirical research is based on a survey conducted in 2012 on Chinese immigrant entrepreneurs in Andalusia (Spain). An ordinal logistic regression specification was employed to test the hypotheses. The results show that the Chinese immigrant entrepreneurs with greater structural, relational and cognitive social capital and better “guanxi” have a higher risk-taking propensity in their business activity

Experimental study of MIMO-OFDM transmissions at 94 GHz in indoor environments

Millimeter wave (mm-wave) frequencies have been proposed to achieve high capacity in 5G communications. Although meaningful research on the channel characteristics has been performed in the 28, 38and 60 GHz bands ─in both indoor and short-range scenarios─,only a small number of trials (experiments) have been carried out in other mm-wave bands. The objective of this work is to study the viability and evaluate the performance of the 94 GHz frequency band for MIMO-OFDM transmission in an indoor environment. Starting from a measurement campaign, the performance of MIMO algorithms is studied in terms of throughput for four different antenna configurations.This work was supported in part by the Ministerio de Economía y Competitividad MINECO, Spain under Grant TEC2016-78028-C3-2-P, and in part by the European FEDER funds

Employability skills developed by non-traditional students along their undergraduate program

This paper was developed in the context of the European project EMPLOY (Enhancing the employability of non-traditional students in higher education, Erasmus Plus Program 2015-2017), a qualitative, interdisciplinary and biographical research focusing on nontraditional university students and graduates from six European countries (Sweden, Poland, United Kingdom, Ireland, Portugal and Spain). The project aims are, among others: a) to understand the employability from the perspective of students and graduates; b) to increase knowledge and understanding of the factors that promote or hinder employability; c) to explore the impact of age, gender, social class, ethnicity and disability in employment prospects of students; etc. In spite of the fact that university graduates are in better conditions when accessing to the labor market, non-traditional students might experience special difficulties related to their specific characteristics. We lack of disaggregated information related to employment rates for higher education graduates and there is not specific research which deepens in the transition process of non-traditional groups. Our study is concerned with identifying which employability skills have been developed by non-traditional students during their stay at the University of Seville. For this purpose we consider the formal learning associated to their syllabuses, the extracurricular training they have been involved in, as well as the previous work experiences. We have carried out seven biographical in-depth interviews with students of the University of Seville (4 females, 3 males), all of them studying degrees in different areas of knowledge: Pedagogy, Philosophy, Mechanical Engineering, Pharmacy, Biology and Business Management. All participants were in the final year of their undergraduate program. In addition, all of them represented different characteristics of non-traditional students: adult and mature students (3), immigrants (2) and learners with low economic and cultural capital (2). As for the results and following the classification of professional competences raised by Bunk (1994), we note that through the university syllabuses students developed the methodological competence, that is the reaction from previous experiences and problem solving skills. However, work experience and extracurricular activities promoted social competence, one that enables them to collaborate with others in a communicative and constructive way, showing interpersonal understanding. In addition, in the three training fields, the specific skills or qualifications of the job, technical competence, were also developed. Finally, it can be noted that in the three areas considered in our analysis, there is a lack in the development of the participatory competence, which refers to coordination and organisational skills, leadership and ability to make decisions and take responsibility.Unión Europea 2014-1-UK01-KA203-00184

Validity and Reliability of an Inertial Device for Measuring Dynamic Weight-Bearing Ankle Dorsiflexion

A decrease in ankle dorsiflexion causes changes in biomechanics, and different instruments have been used for ankle dorsiflexion testing under static conditions. Consequently, the industry of inertial sensors has developed easy-to-use devices, which measure dynamic ankle dorsiflexion and provide additional parameters such as velocity, acceleration, or movement deviation. Therefore, the aims of this study were to analyze the concurrent validity and test-retest reliability of an inertial device for measuring dynamic weight-bearing ankle dorsiflexion. Sixteen participants were tested using an inertial device (WIMU) and a digital inclinometer. Ankle dorsiflexion from left and right ankle repetitions was used for validity analysis, whereas test-retest reliability was analyzed by comparing measurements from the first and second days. The standard error of the measurement (SEM) between the instruments was very low for both ankle measurements (SEM 0.05) even though a significant systematic bias (~1.77°) was found for the right ankle (d = 0.79). R2 was very close to 1 in the left and right ankles (R2 = 0.85–0.89) as well as the intraclass correlation coefficient (ICC > 0.95). Test-retest reliability analysis showed that systematic bias was below 1° for both instruments, even though a systematic bias (~1.50°) with small effect size was found in the right ankle (d = 0.49) with WIMU. The ICC was very close to 1 and the coefficient of variation (CV) was lower than 4% in both instruments. Thus, WIMU is a valid and reliable inertial device for measuring dynamic weight-bearing ankle dorsiflexion

Sorting networks implemented as νMOS circuits

A new realisation for n-input sorters is presented. Resorting to the neuron-MOS (νMOS) concept and to an adequate electrical scheme, a compact and efficient implementation is obtained.Comisión Interministerial de Ciencia y Tecnología TIC95-0094, TIC97-064

Social networks and performance in distributed learning communities

Social networks play an essential role in learning environments as a key channel for knowledge sharing and students' support. In distributed learning communities, knowledge sharing does not occur as spontaneously as when a working group shares the same physical space; knowledge sharing depends even more on student informal connections. In this study we analyse two distributed learning communities' social networks in order to understand how characteristics of the social structure can enhance students' success and performance. We used a monitoring system for social network data gathering. Results from correlation analyses showed that students' social network characteristics are related to their performancePostprint (published version

Sustainability drivers, barriers and outcomes: Evidence from European High Performance Manufacturing Industries

Implementing sustainability practices has become a requirement to be able to operate in several markets since the legal requirements are increasing and society (as well as customers) values sustainability behaviors more. The aims of this paper are (1) to analyze the impact that drivers and barriers have on Environmental practices implemented in the high performance manufacturing industries, (2) to identify the relevant drivers and barriers for these environmental practices, and finally, (3) to study the influence that Environmental practices have on companies´ Financial Performance. To carry out our research, we shall consider a European database of companies involved in the High Performance Manufacturing project. Partial Least Squares (PLS) will be used to test our hypotheses