Showing papers by "Tunis University published in 2016"

A century of trends in adult human height

Abstract: Being taller is associated with enhanced longevity, and higher education and earnings. We reanalysed 1472 population-based studies, with measurement of height on more than 18.6 million participants to estimate mean height for people born between 1896 and 1996 in 200 countries. The largest gain in adult height over the past century has occurred in South Korean women and Iranian men, who became 20.2 cm (95% credible interval 17.5–22.7) and 16.5 cm (13.3–19.7) taller, respectively. In contrast, there was little change in adult height in some sub-Saharan African countries and in South Asia over the century of analysis. The tallest people over these 100 years are men born in the Netherlands in the last quarter of 20th century, whose average heights surpassed 182.5 cm, and the shortest were women born in Guatemala in 1896 (140.3 cm; 135.8–144.8). The height differential between the tallest and shortest populations was 19-20 cm a century ago, and has remained the same for women and increased for men a century later despite substantial changes in the ranking of countries.

Mycobacterium tuberculosis lineage 4 comprises globally distributed and geographically restricted sublineages.

Abstract: Generalist and specialist species differ in the breadth of their ecological niches Little is known about the niche width of obligate human pathogens Here we analyzed a global collection of Mycobacterium tuberculosis lineage 4 clinical isolates, the most geographically widespread cause of human tuberculosis We show that lineage 4 comprises globally distributed and geographically restricted sublineages, suggesting a distinction between generalists and specialists Population genomic analyses showed that, whereas the majority of human T cell epitopes were conserved in all sublineages, the proportion of variable epitopes was higher in generalists Our data further support a European origin for the most common generalist sublineage Hence, the global success of lineage 4 reflects distinct strategies adopted by different sublineages and the influence of human migration

Convolutional neural network for video fire and smoke detection

Abstract: Research on video analysis for fire detection has become a hot topic in computer vision. However, the conventional algorithms use exclusively rule-based models and features vector to classify whether a frame is fire or not. These features are difficult to define and depend largely on the kind of fire observed. The outcome leads to low detection rate and high false-alarm rate. A different approach for this problem is to use a learning algorithm to extract the useful features instead of using an expert to build them. In this paper, we propose a convolutional neural network (CNN) for identifying fire in videos. Convolutional neural network are shown to perform very well in the area of object classification. This network has the ability to perform feature extraction and classification within the same architecture. Tested on real video sequences, the proposed approach achieves better classification performance as some of relevant conventional video fire detection methods and indicates that using CNN to detect fire in videos is very promising.

Effect of salt stress on ion concentration, proline content, antioxidant enzyme activities and gene expression in tomato cultivars.

Abstract: Salinity is a constraint limiting plant growth and productivity of crops throughout the world. Understanding the mechanism underlying plant response to salinity provides new insights into the improvement of salt tolerance-crops of importance. In the present study, we report on the responses of twenty cultivars of tomato. We have clustered genotypes into scale classes according to their response to increased NaCl levels. Three local tomato genotypes, representative of different saline scale classes, were selected for further investigation. During early (0 h, 6 h and 12 h) and later (7 days) stages of the response to salt treatment, ion concentrations (Na+, K+ and Ca2+), proline content, enzyme activities (catalase, ascorbate peroxidase and guiacol peroxidase) were recorded. qPCR analysis of candidate genes WRKY (8, 31and 39), ERF (9, 16 and 80), LeNHX (1, 3 and 4) and HKT (class I) were performed. A high K+, Ca2 +and proline accumulation as well as a decrease of Na+ concentration-mediated salt tolerance. Concomitant with a pattern of high-antioxidant enzyme activities, tolerant genotypes also displayed differential patterns of gene expression during the response to salt stress.

Synchronverter-Based Emulation and Control of HVDC Transmission

Abstract: This paper presents a new control strategy for high voltage direct current (HVDC) transmission based on the synchronverter concept: the sending-end rectifier controls emulate a synchronous motor (SM), and the receiving end inverter emulates a synchronous generator (SG). The two converters connected with a DC line provide what is called a synchronverter HVDC (SHVDC). The structure of the SHVDC is firstly analyzed. It is shown that the droop and voltage regulations included in the SHVDC structure are necessary and sufficient to well define the behavior of SHVDC. The standard parameters of the SG cannot be directly used for this structure. A specific tuning method of these parameters is proposed in order to satisfy the usual HVDC control requirements. The new tuning method is compared with the standard vector control in terms of local performances and fault critical clearing time (CCT) in the neighboring zone of the link. The test network is a 4-machine power system with parallel HVDC/AC transmission. The results indicate the contribution of the proposed controller to enhance the stability margin of the neighbor AC zone of the link.

Testing the relationships between energy consumption, CO2 emissions, and economic growth in 24 African countries: a panel ARDL approach

Abstract: This study complements existing literature by examining the nexus between energy consumption (EC), CO2 emissions (CE), and economic growth (GDP; gross domestic product) in 24 African countries using a panel autoregressive distributed lag (ARDL) approach. The following findings are established. First, there is a long-run relationship between EC, CE, and GDP. Second, a long-term effect from CE to GDP and EC is apparent, with reciprocal paths. Third, the error correction mechanisms are consistently stable. However, in cases of disequilibrium, only EC can be significantly adjusted to its long-run relationship. Fourth, there is a long-run causality running from GDP and CE to EC. Fifth, we find causality running from either CE or both CE and EC to GDP, and inverse causal paths are observable. Causality from EC to GDP is not strong, which supports the conservative hypothesis. Sixth, the causal direction from EC to GDP remains unobservable in the short term. By contrast, the opposite path is observable. There are also no short-run causalities from GDP, or EC, or EC, and GDP to EC. Policy implications are discussed.

Greater effects of high- compared with moderate-intensity interval training on cardio-metabolic variables, blood leptin concentration and ratings of perceived exertion in obese adolescent females.

Abstract: This study examined the effects of high- vs. moderate-intensity interval training on cardiovascular fitness, leptin levels and ratings of perceived exertion (RPE) in obese female adolescents. Forty-seven participants were randomly assigned to one of three groups receiving either a 1:1 ratio of 15 s of effort comprising moderate-intensity interval training (MIIT at 80% maximal aerobic speed: MAS) or high-intensity interval training (HIIT at 100% MAS), with matched 15 s recovery at 50% MAS, thrice weekly, or a no-training control group. The HIIT and MIIT groups showed improved (p < 0.05) body mass (BM), BMI Z-score, and percentage of body fat (%BF). Only the HIIT group showed decreased waist circumference (WC) (p = 0.017). The effect of exercise on maximal oxygen uptake (VO2max) was significant (p = 0.019, ES = 0.48 and p = 0.010, ES = 0.57, HIIT and MIIT, respectively). The decrease of rate-pressure product (RPP) (p < 0.05, ES = 0.53 and ES = 0.46, HIIT and MIIT, respectively) followed the positive changes in resting heart rate and blood pressures. Blood glucose, insulin level and the homeostasis model assessment index for insulin decreased (p < 0.05) in both training groups. Significant decreases occurred in blood leptin (p = 0.021, ES = 0.67 and p = 0.011, ES = 0.73) and in RPE (p = 0.001, ES = 0.76 and p = 0.017, ES = 0.57) in HIIT and MIIT, respectively. In the post-intervention period, blood leptin was strongly associated with %BF (p < 0.001) and VO2max (p < 0.01) in the HIIT and MIIT groups, respectively, while RPE was strongly associated with BM (p < 0.01) in the HIIT group. The results suggest that high-intensity interval training may produce more positive effects on health determinants in comparison with the same training mode at a moderate intensity.

A Secure Routing Protocol Based on RPL for Internet of Things

Abstract: Data transportation and routing in Internet of Things (IoT) is a challenging issue where massive data collection and gathering are predictable. The Routing Protocol for Low- power and Lossy Networks (RPL) is one of the best candidates to ensure routing in 6LoWPAN networks. However, RPL is vulnerable to a number of attacks related to exchanged control messages. In this paper, we propose a new secure routing protocol based on RPL referred to as Secure-RPL (SRPL). The main aim of SRPL is to prevent misbehaving nodes from maliciously changing control message values such as the rank of a node that may disturb a network by creating a fake topology. We introduce the concept of rank threshold along with hash chain authentication technique to deal with internal attacks like sinkhole, black hole, selective forwarding attacks etc. Simulation results show that SRPL is robust and resistant to this kind of attacks based on malicious manipulation of RPL metrics.

Appropriateness of percutaneous revascularization of coronary chronic total occlusions: An overview

Abstract: Coronary chronic total occlusions (CTOs) are commonly encountered in patients undergoing coronary angiography. Several observational studies have demonstrated that successful CTO revascularization is associated with better cardiovascular outcomes and enhanced quality of life (QOL). However, in the absence of randomized trials, its prognostic benefit for patients remains debated. Over the past decade, the interest of the interventional community in CTO percutaneous coronary intervention (PCI) has exponentially grown due to important developments in dedicated equipment and techniques, resulting in high success and low complication rates. Both European and American guidelines have assigned a class IIa (level of evidence B) recommendation for CTO PCI. In the current review, we focus on the impact of CTO revascularization on clinical outcomes and QOL and on appropriate patient selection, and we provide a critical assessment of the current guidelines and recommendations on CTO PCI.

Plant-associated microbiomes in arid lands: diversity, ecology and biotechnological potential

Abstract: Aridification is a worldwide serious threat directly affecting agriculture and crop production. In arid and desert areas, it has been found that microbial diversity is huge, built of microorganisms able to cope with the environmental harsh conditions by developing adaptation strategies. Plants growing in arid lands or regions facing prolonged abiotic stresses such as water limitation and salt accumulation have also developed specific physiological and molecular stress responses allowing them to thrive under normally unfavorable conditions. Under such extreme selection pressures, special root-associated bacterial assemblages, endowed with capabilities of plant growth promotion (PGP) and extremophile traits, are selected by the plants. In this review, we provide a general overview on the microbial diversity in arid lands and deserts versus specific microbial assemblages associated with plants. The ecological drivers that shape this diversity, how plant-associated microbiomes are selected, and their biotechnological potential are discussed. Selection and recruitment of the plant associated bacterial assemblages is mediated by the combination of the bio-pedo-agroclimatic conditions and the plant species or varieties. Diversity and functional redundancy of these associated PGPR makes them very active in supporting plant improvement, health and resistance to drought, salt and related stresses. Implementing proper biotechnological applications of the arid and desert-adapted PGPR constitute the challenge to be raised.

A platform as-a-service for hybrid cloud/fog environments

Abstract: Fog computing brings cloud close to end-users and data sources by enabling computation and storage at the edges of the network. An application can have some of its components running in a “distant” cloud and interacting with the other components running in the fog, closer to end-users and data sources such as wireless sensors. Low latency is the main benefit. Applications spanning cloud and fog, such as Internet of Things (IoT) applications, are still provisioned manually nowadays. This paper proposes an architecture for a Platform as-a-Service (PaaS) to automate applications provisioning in a hybrid cloud/fog environment. Cloud Foundry is used as the basis for its implementation. As a use case, the proposed PaaS was employed to provision a simple component-based IoT application that detects fire and dispatches robots to fight the fire. A prototype is built and measurements are made.

Bacteriocins: Not Only Antibacterial Agents.

Abstract: This commentary was aimed at shedding light on the multifunction of bacteriocins mainly those produced by lactic acid bacteria. These antibacterial agents were first used to improve food safety and quality. With the increasing antibiotic resistance concern worldwide, they have been considered as viable agents to replace or potentiate the fading abilities of conventional antibiotics to control human pathogens. Bacteriocins were also shown to have potential as antiviral agents, plant protection agents, and anticancer agents. Bacteriocins were reported to be involved in shaping bacterial communities through inter- and intra-specific interactions, conferring therefore to producing strains a probiotic added value. Furthermore, bacteriocins recently were shown as molecules with a fundamental impact on the resilience and virulence of some pathogens.

Staphylococcus aureus in Animals and Food: Methicillin Resistance, Prevalence and Population Structure. A Review in the African Continent.

Abstract: The interest about Staphylococcus aureus (S. aureus) and methicillin resistant S. aureus (MRSA) in livestock, and domestic and wild animals has significantly increased. The spread of different clonal complexes related to livestock animals, mainly CC398, and the recent description of the new mecC gene, make it necessary to know more about the epidemiology and population structure of this microorganism all over the world. Nowadays, there are several descriptions about the presence of S. aureus and/or MRSA in different animal species (dogs, sheep, donkeys, bats, pigs, and monkeys), and in food of animal origin in African countries. In this continent, there is a high diversity of ethnicities, cultures or religions, as well as a high number of wild animal species and close contact between humans and animals, which can have a relevant impact in the epidemiology of this microorganism. This review shows that some clonal lineages associated with humans (CC1, CC15, CC72, CC80, CC101, and CC152) and animals (CC398, CC130 and CC133) are present in this continent in animal isolates, although the mecC gene has not been detected yet. However, available studies are limited to a few countries, very often with incomplete information, and many more studies are necessary to cover a larger number of African countries.

Does gender diversity on corporate boards increase risk-taking?

Abstract: We study the impact of board gender diversity on firm risk-taking in a developing market. Our study is drawn from a sample of 30 Tunisian-listed firms between 1997 and 2010. First, we found that women have a risk perception that leads to risk avoidance behaviour: the presence of women directors, even when there is one woman director, is positively associated with cash ratio. Second, we showed no significant relationship between board gender diversity and the propensity to take strategic or financial risk-taking. Third, the presence of state officer/bureaucrats and/or politically connected women have a positive effect on cash holding and investment opportunities. Finally, we found that foreign investors do not invest in firms with gender-diverse boards. We conclude with a discussion of contributions to scholarship and practice, and present avenues for future research. Copyright © 2015 ASAC. Published by John Wiley & Sons, Ltd. Resume Nous etudions l'impact de la diversite de genre au sein du conseil d'administration sur la prise de risque des firmes dans les marches en voie de developpement. Notre etude se base sur un echantillon de 30 firmes tunisiennes cotees entre 1997 et 2010. D'abord, nous avons constate que les femmes ont une perception de risque qui se traduit par un contournement des risques : la presence de femmes membres du conseil d'administration, une ou plus, est positivement associee au ratio de liquidite. Deuxiemement, nous n'avons montre aucune relation significative entre la diversite de genre et la propension de prendre des risques strategiques ou financiers. Troisiemement, la presence des femmes employees de l'Etat/bureaucrates et/ou des femmes politiquement connectees a un effet positif sur la liquidite des actifs et les opportunites d'investissement. Finalement, nous avons constate que des investisseurs etrangers n'investissent pas dans des firmes avec des conseils caracterises par la diversite de genre. Nous concluons avec une discussion de contributions a la litterature et la pratique et presentons des avenues pour la recherche future. Copyright © 2015 ASAC. Published by John Wiley & Sons, Ltd.

DSP-based adaptive backstepping using the tracking errors for high-performance sensorless speed control of induction motor drive.

Abstract: This paper presents a modified structure of the backstepping nonlinear control of the induction motor (IM) fitted with an adaptive backstepping speed observer. The control design is based on the backstepping technique complemented by the introduction of integral tracking errors action to improve its robustness. Unlike other research performed on backstepping control with integral action, the control law developed in this paper does not propose the increase of the number of system state so as not increase the complexity of differential equations resolution. The digital simulation and experimental results show the effectiveness of the proposed control compared to the conventional PI control. The results analysis shows the characteristic robustness of the adaptive control to disturbances of the load, the speed variation and low speed.