Showing papers by "Tunis University published in 2011"
TL;DR: This article examined the extent of the current global crisis and the contagion effects it induces by conducting an empirical investigation of the extreme financial interdependences of some selected emerging markets with the US.
Abstract: The paper examines the extent of the current global crisis and the contagion effects it induces by conducting an empirical investigation of the extreme financial interdependences of some selected emerging markets with the US. Several copula functions that provide the necessary flexibility to capture the dynamic patterns of fat tail as well as linear and nonlinear interdependences are used to model the degree of cross-market linkages. Using daily return data from Brazil, Russia, India, China (BRIC) and the US, our empirical results show strong evidence of time-varying dependence between each of the BRIC markets and the US markets, but the dependency is stronger for commodity-price dependent markets than for finished-product export-oriented markets. We also observe high levels of dependence persistence for all market pairs during both bullish and bearish markets.
504 citations
TL;DR: The interaction between zinc and cadmium was investigated in tomato plants and suggested that higher Zn concentrations and Cd are synergistic in their effect on plant growth parameters and oxidative stress.
Abstract: The interaction between zinc and cadmium was investigated in tomato plants (Solanum lycopersicum). Ten-day-old seedlings were treated with 10 micromol/L CdCl2 associated to different concentrations of ZnCl2 (10, 50, 100, and 150 micromol/L). Zn supply clearly reduced Cd accumulation in leaves and simultaneously increased Zn concentration. Cd induced oxidative stress in leaves as indicated by an increase in thiobarbituric acid-reactive substances (TBARS) level and chlorophyll breakdown. Furthermore, compared with control, Cd-treated plants had significantly higher activities of superoxide dismutase (SOD, EC 1.15.1.1), whereas, catalase (CAT, EC 1.111.1.6), ascorbate peroxidase (APX, EC 1.11.1.11), and glutathione reductase (GR, EC 1.6.4.2) activities were significantly suppressed by Cd addition. Zn supplementation, at low level, restored and enhanced the functional activity of these enzymes (SOD, CAT, APX and GR) as compared to Cd-alone-treated plants. The beneficial effect of adequate Zn level on Cd toxicity was confirmed by a significant decrease in TBARS level and restoration of chlorophyll content. However, when Zn was added at high level in combination with Cd there was an accumulation of oxidative stress, which was higher than that for Cd or excess Zn alone treatments. These results suggested that higher Zn concentrations and Cd are synergistic in their effect on plant growth parameters and oxidative stress.
192 citations
TL;DR: Common fixed point theorems for four mappings satisfying a generalized nonlinear contraction type condition on partial metric spaces are proved.
177 citations
TL;DR: In this article, the authors established coincidence fixed point and common fixed point theorems for mappings satisfying ( ψ, φ ) -weakly contractive condition in an ordered complete metric space.
Abstract: We establish coincidence fixed point and common fixed point theorems for mappings satisfying ( ψ , φ ) -weakly contractive condition in an ordered complete metric space. Some applications of our obtained results are given.
177 citations
TL;DR: The results showed the effect of 14 d stress on the tomato root proteome and underlined significant genotype differences, suggesting the importance of making use of genetic variability.
Abstract: To evaluate the genotypic variation of salt stress response in tomato, physiological analyses and a proteomic approach have been conducted in parallel on four contrasting tomato genotypes. After a 14 d period of salt stress in hydroponic conditions, the genotypes exhibited different responses in terms of plant growth, particularly root growth, foliar accumulation of Na(+), and foliar K/Na ratio. As a whole, Levovil appeared to be the most tolerant genotype while Cervil was the most sensitive one. Roma and Supermarmande exhibited intermediary behaviours. Among the 1300 protein spots reproducibly detected by two-dimensional electrophoresis, 90 exhibited significant abundance variations between samples and were submitted to mass spectrometry for identification. A common set of proteins (nine spots), up- or down-regulated by salt-stress whatever the genotype, was detected. But the impact of the tomato genotype on the proteome variations was much higher than the salt effect: 33 spots that were not variable with salt stress varied with the genotype. The remaining number of variable spots (48) exhibited combined effects of the genotype and the salt factors, putatively linked to the degrees of genotype tolerance. The carbon metabolism and energy-related proteins were mainly up-regulated by salt stress and exhibited most-tolerant versus most-sensitive abundance variations. Unexpectedly, some antioxidant and defence proteins were also down-regulated, while some proteins putatively involved in osmoprotectant synthesis and cell wall reinforcement were up-regulated by salt stress mainly in tolerant genotypes. The results showed the effect of 14 d stress on the tomato root proteome and underlined significant genotype differences, suggesting the importance of making use of genetic variability.
170 citations
TL;DR: It is concluded that, despite the importance of a good functionality of the associated microbiota in preserving insect health has been proved, the mechanisms involved in honeybee gut dysbiosis are still unknown.
Abstract: Since a few decades, apiculture is facing important economic losses worldwide with general major consequences in many areas of agriculture. A strong attention has been paid towards the phenomenon named Colony Collapse Disorder in which colonies suddenly disappear with no clear explanations. Honeybee colonies can be affected by abiotic factors, such as environmental pollution or insecticide applications for agricultural purposes. Also biotic stresses cause colony losses, including bacterial (e.g. Paenibacillus larvae) and fungal (e.g. Ascosphaera apis) pathogens, microsporidia (e.g. Nosema apis), parasites (i.e. Varroa destructor) and several viruses. In the light of recent research, intestinal dysbiosis, considered as the relative disproportion of the species within the native microbiota, has shown to affect human and animal health. In arthropods, alteration of the gut microbial climax community has been shown to be linked to health and fitness disequilibrium, like in the medfly Ceratitis capitata for which low mate competitiveness is determined by a gut microbial community imbalance. According to these observations, it is possible to hypothesize that dysbiosis may have a role in disease occurrence also in honeybees. Here we aim to discuss the current knowledge on dysbiosis in the honeybee and its relation with honeybee health by reviewing the investigations of the microbial diversity associated to honeybees and the recent experiments performed to control bee diseases by microbial symbionts. We conclude that, despite the importance of a good functionality of the associated microbiota in preserving insect health has been proved, the mechanisms involved in honeybee gut dysbiosis are still unknown. Accurate in vitro, in vivo and in field investigations are required under healthy, diseased and stressed conditions for the host.
156 citations
TL;DR: Coupled coincidence and coupled common fixed point theorems for a mixed g -monotone mapping satisfying nonlinear contractions in partially ordered G -metric spaces are proved.
152 citations
TL;DR: The presented review summarizes information concerning the morphology, ethnopharmacology, phytochemistry, and biological activities of caper plants.
138 citations
TL;DR: In this article, nano-emulsions based on natural food ingredients were used as delivery systems of two different bioactive compounds, resveratrol and curcumin, with the ultimate goal of improving the antioxidant and/or antimicrobial activities of the encapsulated compounds.
Abstract: Encapsulation into nanoemulsion-based delivery systems of bioactive compounds characterized by low solubility in aqueous phase, represents an effective approach to improve the dispersion of the bioactives into food products, to protect them against degradation or interaction with other ingredients, to reduce the impact on organoleptic properties of the food and to improve their bioavailability The aim of the present work is the fabrication of nanoemulsions, based on natural food ingredients, to be used as delivery systems of two different bioactive compounds, resveratrol and curcumin, with the ultimate goal of improving the antioxidant and/or antimicrobial activities of the encapsulated compounds A preliminary screening study of the optimal emulsion ingredients was carried out through the construction of a pseudo-ternary phase diagram of kinetic stability The formation of very fine emulsions in the nanometric range (
124 citations
TL;DR: It is shown that the proposed implementation method enables high switching frequency operation with high pulse resolution as well as a negligible propagation time for the generation of the gating pulses.
Abstract: This paper proposes a real-time DSP- and FPGA-based implementation method of a space vector modulation (SVM) algorithm for an indirect matrix converter (IMC). Therefore, low-cost and compact control platform is built using a 32-bit fixed-point DSP (TMS320F2812) operating at 150 MHz and a SPARTAN 3E FPGA operating at 50 MHz. The method consists in using the event-manager modules of the DSP to build specified pulses at its PWM output peripherals, which are fed to the digital input ports of a FPGA. Moreover, a simple logical processing and delay times are thereafter implemented in the FPGA so as to synthesize the suitable gate pulse patterns for the semiconductor-controlled devices. It is shown that the proposed implementation method enables high switching frequency operation with high pulse resolution as well as a negligible propagation time for the generation of the gating pulses. Experimental results from an IMC prototype confirm the practical feasibility of the proposed technique.
106 citations
TL;DR: A Riemannian framework for smoothing data that are constrained to live in $\mathcal{P}(n)$, the space of symmetric positive-definite matrices of order n, which is equivalent to the heat flow or isotropic linear diffusion which smooths data everywhere.
Abstract: In this paper we present a Riemannian framework for smoothing data that are constrained to live in $\mathcal{P}(n)$ , the space of symmetric positive-definite matrices of order n. We start by giving the differential geometry of $\mathcal{P}(n)$ , with a special emphasis on $\mathcal{P}(3)$ , considered at a level of detail far greater than heretofore. We then use the harmonic map and minimal immersion theories to construct three flows that drive a noisy field of symmetric positive-definite data into a smooth one. The harmonic map flow is equivalent to the heat flow or isotropic linear diffusion which smooths data everywhere. A modification of the harmonic flow leads to a Perona-Malik like flow which is a selective smoother that preserves edges. The minimal immersion flow gives rise to a nonlinear system of coupled diffusion equations with anisotropic diffusivity. Some preliminary numerical results are presented for synthetic DT-MRI data.
TL;DR: This paper focuses on a widely known würtzite structured crystal and finds that Urbach tailing was inhibited once doping charged loci succeeded to establish local coordinated donors networks or so-called topological filaments.
Abstract: Doping-related behavior divergence of some crystalline materials has raised doubts about Urbach tailing universality. In this paper, we infer the atomic scale interpretation of this divergence on the basis of experimental records and comparative studies. We focus on a widely known wurtzite structured crystal and find that Urbach tailing was inhibited once doping charged loci succeeded to establish local coordinated donors networks or so-called topological filaments. The case of doping-free and saturated ZnO networks unexpected Urbach tailing features has been discussed. All the observed behaviors confirm the Urbach tailing universality despite their controversial aspect.
TL;DR: The results suggest that coupling is surprisingly on the same order of magnitude or even larger in conductance measurements whereas electron transfer occurs on larger distances than in transient electrochemistry.
Abstract: We measured single-molecule conductances for three different redox systems self-assembled onto gold by the STMBJ method and compared them with electrochemical heterogeneous rate constants determined by ultrafast voltammetry It was observed that fast systems indeed give higher conductance Monotonous dependency of conductance on potential reveals that large molecular fluctuations prevent the molecular redox levels to lie in between the Fermi levels of the electrodes in the nanogap configuration Electronic coupling factors for both experimental approaches were therefore evaluated based on the superexchange mechanism theory The results suggest that coupling is surprisingly on the same order of magnitude or even larger in conductance measurements whereas electron transfer occurs on larger distances than in transient electrochemistry
TL;DR: In this paper, a thin film of Cu2SnS3 was synthesized by solid state reaction under vapour sulphur pressure at 530°C, during 6h, via a sequentially deposited copper and tin layers.
01 Sep 2011
TL;DR: An interactive version of TKR-NSGA-II is proposed which is useful when the DM has no a priori information about the number of existing knees in the Pareto optimal front and can provide competitive and better results when compared to other recently proposed methods.
Abstract: Evolutionary Algorithms (EAs) have been recognized to be well suited to approximate the Pareto front of Multi-objective Optimization Problems (MOPs). In reality, the Decision Maker (DM) is not interested in discovering the whole Pareto front rather than finding only the portion(s) of the front that matches at most his/her preferences. Recently, several studies have addressed the decision-making task to assist the DM in choosing the final alternative. Knee regions are potential parts of the Pareto front presenting the maximal trade-offs between objectives. Solutions residing in knee regions are characterized by the fact that a small improvement in either objective will cause a large deterioration in at least another one which makes moving in either direction not attractive. Thus, in the absence of explicit DM’s preferences, we suppose that knee regions represent the DM’s preferences themselves. Recently, few works were proposed to find knee regions. This paper represents a further study in this direction. Hence, we propose a new evolutionary method, denoted TKR-NSGA-II, to discover knee regions of the Pareto front. In this method, the population is guided gradually by means of a set of mobile reference points. Since the reference points are updated based on trade-off information, the population converges towards knee region centers which allows the construction of a neighborhood of solutions in each knee. The performance assessment of the proposed algorithm is done on two- and three-objective knee-based test problems. The obtained results show the ability of the algorithm to: (1) find the Pareto optimal knee regions, (2) control the extent (We mean by extent the breadth/spread of the obtained knee region.) of the obtained regions independently of the geometry of the front and (3) provide competitive and better results when compared to other recently proposed methods. Moreover, we propose an interactive version of TKR-NSGA-II which is useful when the DM has no a priori information about the number of existing knees in the Pareto optimal front.
TL;DR: In this paper, a methanol oxidation reaction was investigated on platinum nanoparticles supported by TiO 2 nanotubes (XC72), and the electrocatalytic activity of the catalyst was measured by cyclic voltammetry.
Abstract: Titanium dioxide nanotubes were prepared via a hydrothermal treatment of TiO 2 powder (Degussa P25). Obtained samples were analyzed by various techniques, such as transmission electron microscopy (TEM) and X-ray diffraction (XRD), which revealed that the crystal structure of the obtained materials was similar to that of H 2 Ti 2 O 5 ·H 2 O nanotubes, and were about 50 nm in length and 20 nm in diameter. Nitrogen adsorption–desorption isotherms indicated that synthesized solids are mesoporous materials with a multi-walled nanotubular structure and high specific surface area. The methanol oxidation reaction was investigated on platinum nanoparticles supported TiO 2 nanotubes (XC72). The electrocatalytic activity of the catalyst was measured by cyclic voltammetry. CO stripping voltammetry in acidic solutions was investigated to study the reaction of the catalysts towards poisoning by carbonyl compounds. The results demonstrated that Pt/TiO 2 nanotubes catalyst exhibits the best activity for methanol oxidation and were favorable for improving the tolerance to poisoning species.
TL;DR: In this paper, the reverse osmosis desalination unit powered by photovoltaic-Wind hybrid system for producing potable water from brackish water is an appropriate solution to southern Tunisia (salinity about 6g/l).
TL;DR: Using both marker systems, the Tunisian fig germ plasm is characterised by having a large genetic diversity at the deoxyribonucleic acid level, as most of AFLP bands were detected and all SSR markers were polymorphic.
Abstract: This study characterises the genetic variability of fig, Ficus carica L., using simple sequence repeat (SSR) and amplified fragment length polymorphism (AFLP) markers. It compares the efficiency and utility of the two techniques in detecting variation and establishing genetic relationships among Tunisian fig cultivars. Our results show that using both marker systems, the Tunisian fig germ plasm is characterised by having a large genetic diversity at the deoxyribonucleic acid level, as most of AFLP bands were detected and all SSR markers were polymorphic. In fact, 351 (342 polymorphic) and 57 (57 polymorphic) bands were detected using AFLP and SSR primers, respectively. SSR markers were the most polymorphic with an average polymorphic information content value of 0.94, while AFLP markers showed the highest effective multiplex ratio (56.9) and marker index (45.2). The effective marker index was recorded highest (4.19) for AFLP markers and lowest (0.70) for the SSR ones. Our results demonstrate that (1) independent as well as combined analyses of cluster analyses of SSR and AFLP fragments showed that cultivars are clustered independently from their geographical origin, horticultural classifications and tree sex; (2) the analysis of molecular variance allowed the partitioning of genetic variation within and among fig groups and showed greater variation within groups and (3) AFLP and SSR markers datasets showed positive correlation. This study suggests the SSR and AFLP markers are suitable for diversity analysis and cultivars fingerprinting. An understanding of the genetic diversity and population structure of F. carica in Tunisia can also provide insight into the conservation and management of this species.
Journal Article•
TL;DR: The identification of Th17 cells helps to explain some of the anomalies seen in the Th1/Th2 axis and has broadened the understanding of the immunopathological effects of Th 17 cells in the development of Behçet's disease.
Abstract: Accumulating evidence suggests that the abnormality of innate and adaptive immunity responses plays an important role in Behcet's disease (BD). T helper (Th) cells have a central role in modulating immune responses. Traditionally, BD is regarded as a Th1-mediated inflammatory disease. Recently, Th17 cells were identified as a new subset of Th cells unrelated to Th1 or Th2 cells, and several cytokines are involved in regulating their activation and differentiation. Naive murine CD4+ Th can be induced to differentiate towards Th1, Th2, Th17 and Treg phenotypes according to the local cytokine milieu. The committed cells are characterised by expression of specific transcription factors, T bet for Th1, GATA-3 for Th2, Foxp3 for Tregs and RORγt (RORγt/RORC) for Th17 cells. It has been demonstrated that the skewing of murine Th towards Th17 and Treg is mutually exclusive. Th17 cells regulate inflammation via production of distinct cytokines such as interleukin (IL)-17. There is growing evidence that Th17 cells are pathological in many human autoimmune and inflammatory diseases, leading to intense interest in defining their origins, functions and developing strategies to block their pathological effects. Evidence from human disease such as BD suggests that specialised antigen-presenting cells drive their in vivo development. Knowledge of how Th17 cells interact with other immune cells is limited, but recent data suggest that Th17 cells may not be subject to strict cellular regulation by T regulatory cells. Notably, Th17 cells and Treg cells appear to share common developmental pathways and both cell types retain significant plasticity. Herein, we will discuss the molecular and cellular regulation of Th17 cells with an emphasis on BD. The identification of Th17 cells helps us to explain some of the anomalies seen in the Th1/Th2 axis and has broadened our understanding of the immunopathological effects of Th17 cells in the development of BD.
TL;DR: In this paper, the antioxidant activity of 3,4-dihydroxyphenylpyruvic acid (3-4-DHPPA) was investigated using B3LYP/6-31+G*, 6-311++G** and Integral Equation Formalism Polarizable Continuum Model (PCM) methods.
TL;DR: In this article, the synthesis and the study of physico-chemical and catalytic properties of a series of lanthanum manganite perovskite-type oxide using the one-step combustion method were investigated.
Abstract: The present work deals with the synthesis and the study of physico-chemical and catalytic properties of a series of lanthanum manganite perovskite-type oxide using the one-step combustion method. Glycine was used as complexing agent and fuel. Seven glycine-to-nitrate ratios from 0.32 to 0.8 were investigated. XRD patterns show a single phase perovskite type oxide when glycine-to-nitrate ratio is above 0.37. Glycine/nitrate ratio affects significantly the surface areas, which range in 18–37 m2/g. The use of fuel-rich precursor allows an enhancement of the specific surface area, the reducibility of manganese and the mobility of desorbed oxygen. The light-off temperature for 50% and 90% of methane conversion was found to be directly related to surface areas. The highest catalytic activity was obtained for glycine-to-nitrate ratio of 0.8, which exhibits the highest superficial concentration of manganese and the highest amount of active oxygen. This catalyst shows also a good thermal stability.
TL;DR: Some fixed point theorems for T-weakly isotone increasing mappings are presented which satisfy a generalized nonlinear contractive condition in complete ordered metric spaces and the existence theorem for a solution of some integral equations is established.
TL;DR: In this article, a new class of generalized nonlinear contractions on partially ordered partial metric spaces is introduced, and some common fixed-point theorems for these contractions are proved.
Abstract: In this paper, a new class of a pair of generalized nonlinear contractions on partially ordered partial metric spaces is introduced, and some coincidence and common fixed-point theorems for these contractions are proved. Presented theorems are twofold generalizations of very recent fixed-point theorems of Altun and Erduran (Fixed Point Theory Appl 2011(Article ID 508730):10, 2011), Altun et al. (Topol Appl 157(18):2778-2785, 2010), Matthews (Proceedings of the 8th summer conference on general topology and applications, New York Academy of Sciences, New York, pp. 183-197, 1994) and many other known corresponding theorems.
TL;DR: This study describes an outbreak of VIM-2-producing P. aeruginosa in a kidney transplantation unit of Tunis, Tunisia, which showed a high level of resistance to all antimicrobials tested except to colistin.
Abstract: Background
Twenty four non replicate imipenem resistant P. aeruginosa were isolated between January and November 2008, in the kidney transplantation unit of Charles Nicolle Hospital of Tunis (Tunisia). This study was conducted in order to establish epidemiological relationship among them and to identify the enzymatic mechanism involved in imipenem resistance.
TL;DR: This paper studies some coincidence fixed point and common fixed point theorems for three mappings S,T and R satisfying (@j,@f)-weakly contractive condition in an ordered complete metric space, where the mappingsS and T are assumed to be weakly increasing with respect to R.
Abstract: Recently, Heman Kumar Nashine and Bessem Samet [H.K. Nashine, B. Samet, Fixed point results for mappings satisfying (@j,@f)-weakly contractive condition in partially ordered metric spaces, Nonlinear Anal. 74 (2011) 2201-2209] studied some coincidence fixed point and common fixed point theorems for two mappings satisfying (@j,@f)-weakly contractive condition in an ordered complete metric space. In the present paper, we study some coincidence fixed point and common fixed point theorems for three mappings S,T and R satisfying (@j,@f)-weakly contractive condition in an ordered complete metric space, where the mappings S and T are assumed to be weakly increasing with respect to R. Our results generalize several well-known results in the literature.
TL;DR: This article investigated the potential glioprotective effect of pituitary adenylate cyclase-activating polypeptide (PACAP) on astroglial cell survival.
Abstract: Oxidative stress, associated with a variety of disorders including neurodegenerative diseases, results from accumulation of reactive oxygen species (ROS) Oxidative stress is not only responsible for neuron apoptosis, but can also provoke astroglial cell death Numerous studies indicate that pituitary adenylate cyclase-activating polypeptide (PACAP) promotes neuron survival, but nothing is known regarding the action of PACAP on astroglial cell survival Thus, the purpose of the present study was to investigate the potential glioprotective effect of PACAP on H(2)O(2)-induced astrocyte death Pre-treatment of cultured rat astrocytes with nanomolar concentrations of PACAP prevented cell death provoked by H(2)O(2) (300 μM), whereas vasoactive intestinal polypeptide was devoid of protective activity The effect of PACAP on astroglial cell survival was abolished by the type 1 PACAP receptor antagonist, PACAP6-38 The protective action of PACAP was blocked by the protein kinase A inhibitor H89, the protein kinase C inhibitor chelerythrine and the mitogen-activated protein (MAP)-kinase kinase (MEK) inhibitor U0126 PACAP stimulated glutathione formation, and blocked H(2)O(2)-evoked ROS accumulation and glutathione content reduction In addition, PACAP prevented the decrease of mitochondrial activity and caspase 3 activation induced by H(2)O(2) Taken together, these data indicate for the first time that PACAP, acting through type 1 PACAP receptor, exerts a potent protective effect against oxidative stress-induced astrocyte death The anti-apoptotic activity of PACAP on astrocytes is mediated through the protein kinase A, protein kinase C and MAPK transduction pathways, and can be accounted for by inhibition of ROS-induced mitochondrial dysfunctions and caspase 3 activation
TL;DR: The present study unveiled the unexpected finding that osmopriming cannot simply be considered as an advance of germination-related processes but involves other mechanisms improving germination such as the mounting of defense mechanisms enabling osmiprimed seeds to surmount environmental stresses potentially occurring during germination.
Abstract: Alfalfa, the most widely grown leguminous crop in the world, is generally exposed to severe salinity stress in Tunisia, notably affecting its germination performance. Toward a better understanding of alfalfa seed vigor, we have used proteomics to characterize protein changes occurring during germination and osmopriming, a pretreatment that accelerates germination and improves seedling uniformity particularly under stress conditions. The data revealed that germination was accompanied by dynamic changes of 79 proteins, which are mainly involved in protein metabolism, cell structure, metabolism, and defense. Comparative proteomic analysis also revealed 63 proteins specific to osmopriming, 65 proteins preferentially varying during germination, and 14 proteins common to both conditions. Thus, the present study unveiled the unexpected finding that osmopriming cannot simply be considered as an advance of germination-related processes but involves other mechanisms improving germination such as the mounting of def...
TL;DR: In this paper, an experimental methodology is presented using digital image techniques to assess the internal microcracks and to quantify the rock damage within rock cores, which is then applied to a set of limestone cores which were sampled before and after a real field blast round.
TL;DR: All the results indicated the potential application of titanate nanotubes as solid-phase extraction adsorbents to pre-treat water samples, and the developed method was successfully applied to the analysis of surface water samples.
Abstract: An analytical method based on TiO2 nanotubes solid-phase extraction (SPE) combined with gas chromatography (GC) was established for the analysis of seven polycyclic aromatic hydrocarbons (PAHs): acenaphtylene, acenaphthene, anthracene, fluorene, phenanthrene, fluoranthene and pyrene. Factors affecting the extraction efficiency including the eluent type and its volume, adsorbent amount, sample volume, sample pH and sample flow rate were optimized. The characteristic data of analytical performance were determined to investigate the sensitivity and precision of the method. Under the optimized extraction conditions, the method showed good linearity in the range of 0.01-0.8 microg/mL, repeatability of the extraction (RSD were between 6.7% and 13.5%, n = 5) and satisfactory detection limits (0.017-0.059 ng/mL). The developed method was successfully applied to the analysis of surface water (tap, river and dam) samples. The recoveries of PAHs spiked in environmental water samples ranged from 90% to 100%. All the results indicated the potential application of titanate nanotubes as solid-phase extraction adsorbents to pre-treat water samples.
TL;DR: The numerical results show the effectiveness of the SMA damper to damp the high free vibration and the harmonic vibration better than an optimal TMD.
Abstract: This paper focuses on introducing and investigating the performance of a new passive control device for stay cable in cable-stayed bridges made with shape-memory alloys (SMA). The superelasticity and damping capability of SMA is sought in this study to develop a supplementary energy dissipation device for stay cable. A linear model of a sag cable and a one-dimensional constitutive model for the SMA are used. The problem of the optimal design of the device is studied. In the optimization problem, an energy criterion associated with the concept of optimal performance of the hysteretic connection is used. The maximum dissipation energy depends on the cross-sectional area, the length, and the location of the SMA on the cable. The effectiveness of the SMA damper in controlling the cable displacement is assessed. Furthermore, a study is conducted to determine the sensitivity of the cable response to the properties of the SMA device. The comparison between the SMA damper and a more classical passive control energy dissipation device, i.e., the tuned mass damper (TMD), is carried out. The numerical results show the effectiveness of the SMA damper to damp the high free vibration and the harmonic vibration better than an optimal TMD.