Electronic Structure Of Amorphous Si3n4 In The Cluster-bethe-lattice Approximation

We present a calculation of the electronic structure of amorphous Si3N4, using a model tight-binding Hamiltonian with a basis set of Si 3s and 3p, and N 2s and 2p orbitals. Clusters of 13 atoms, centered at either a Si or a N atom, are constructed using structural data from crystalline 2-Si3N4. These clusters are employed to generate a self-consistent transfer-matrix approximation for an infinite effective medium (Bethe lattice). The local and average densities of states are evaluated using standard one-particle Greens operator techniques. We also simulate photoemission spectra by weighting orbitally decomposed partial densities of states with appropriate photoemission cross sections. Our results are in good agreement with recent experimental data. © 1985 The American Physical Society.32128332833

Analyses phytochimiques et propriétés des composés bioactifs: amélioration d’une huile végétale par incorporation des extraits de plantes steppiques

La multitude de structures phénoliques qui pourraient être contenus dans un matériel végétal donné, ainsi que leur teneur élevée en polyphénols totaux, permet leur utilisation en tant que facteurs antioxydants efficaces pour les corps gras. Le but de cette recherche est d'évaluer l'efficacité des extraits de deux plantes médicinales préparés à partir de trois solvants différents (EtOH, Ethyacétate et l’eau) dans une huile d'olive algérienne pauvre en antioxydants naturels exposée à une oxydation forcée au rancimat. Les extraits ont été ajoutés à 300, 500 et 900 ppm de niveau d'équivalence phénolique. Après oxydation on réévalue les paramètres physico-chimiques pour suivre la dégradation des échantillons d’huiles sujettes à la thermo-oxydation. Tandis qu’une étape primordiale du dosage des antioxydants tant qu’une évaluation de leur potentiel antioxydant a également été réalisés comme première étape dans les extraits de plantes et de l'huile avant le chauffage, et seulement sur l'huile après le chauffage pour évaluer les la perte en antioxydants intervenant dans le processus antioxydant. Ainsi une teneur élevée en polyphénols totaux (en mg eq AG/g MS) et flavonoïdes (en mg eq CAT/gMS) a était respectivement notée pour l’extrait EtOH/H2O (456,05±8,54, 30,21±0,28) suivi de l’extrait aqueux (424,23±7,79, 46,45±0,11) et l’Ethylacétate (229,76±4,76, 9,13±0,19). Ce qui permet tout de même à l’extrait EtOH/H2O d’avoir le potentiel antioxydant le plus remarquable (IC50= 88,687μg/ml). Les résultats du Rancimat conduisent à conclure qu’une concentration moyenne en extrait pourra avoir des temps d’induction les plus élevés (15h +/- 0,5). Sur la base des analyses statistiques obtenus, il est irréfutable que l'utilisation d’additifs naturels d'origine végétale pour l'enrichissement de lipides (graisses et huiles) et les aliments contenant des lipides est une perspective a considéré afin de prolonger la durée de vie des matières grasses.info:eu-repo/semantics/publishedVersio

Dilution and magnification effects on image analysis applications in activated sludge characterization

The properties of activated sludge systems can be characterized using image analysis procedures. When these systems operate with high biomass content, accurate sludge characterization requires samples to be diluted. Selection of the best image acquisition magnification is directly related to the amount of biomass screened. The aim of the present study was to survey the effects of dilution and magnification on the assessment of aggregated and filamentous bacterial content and structure using image analysis procedures. Assessments of biomass content and structure were affected by dilutions. Therefore, the correct operating dilution requires careful consideration. Moreover, the acquisition methodology comprising a 100 magnification allowed data on aggregated and filamentous biomass to be determined and smaller aggregates to be identified and characterized, without affecting the accuracy of lower magnifications regarding biomass representativeness.AGERE (Empresa de Águas, Efluentes e Resíduos de Braga – EM) and AGS(Administração e Gestão de Sistemas de Salubridade, S.A.)Fundação para a Ciência e Tecnologia (FCT

Bioactive properties of medicinal plants from the Algerian flora: selecting the species with the highest potential in view of application purposes

The Algerian flora contains a wide variety of plant species with potential to be used in medicinal applications. Herein, the bioactive properties of medicinal plants from Algeria were evaluated to select the species with highest suitability to be used under specific purposes, while scientifically validating their health claims. The antioxidant activity of the infusions was screened by using several tests and cytotoxic properties were evaluated against human tumor cell lines (as also against non-tumor cells). Different hydrophilic bioactive compounds were also quantified. The results were analyzed considering individual variations in each parameter (ANOVA), but also in an aggregated approach by applying principal component analysis to acquire a comprehensive knowledge regarding the overall bioactive potential of the studied species. Limoniastrum guyonianum and Thymus pallescens showed the highest antioxidant activity (EC50 values ranging from 29 to 229 μg/mL and 54 to 240 μg/mL, respectively), whilst Asteriscus graveolens and L. guyonianum gave the best cytotoxicity against human tumor cell lines (GI50 values ranging from 11 to 29 μg/mL and 22 to 70 μg/mL, respectively). T. pallescens stood out as the species with highest bioactive compounds contents (phenols: 463 mg GAE, flavonoids: 194 mg CE, esters; 186 mg CAE; flavonols: 85 mg QE, considering g of lyophilized infusion basis). From a global point of view, T. pallescens, Saccocalyx satureioides and Ptychotis verticillata proved to be the preferable choices as high potential sources of bioactive compounds, while Haloxylon scoparium, L. guyonianum and A. graveolens would be the most suitable matrices considering the bioactivity (especially cytotoxicity) criterion, as inferred from the PCA outputs.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support to CIMO (PEst-OE/AGR/UI0690/2014), R.C. Calhelha (SFRH/BPD/68344/2010), J.C.M. Barreira (SFRH/BPD/72802/2010) and L. Barros (“Compromisso para a Ciência 2008” contract)

A comparison between bright field and phase-contrast image analysis techniques in activated sludge morphological characterization

Different approaches using microscopy image analysis procedures were employed for characterization of activated sludge systems. The approaches varied mainly on the type of visualization and acquisition method used for collection of data. In this context, this study focused on the comparison of the two most common acquisition methods: bright field and phase-contrast microscopy. Images were acquired from seven different wastewater treatment plants for a combined period of two years. Advantages and disadvantages of each acquisition technique and the results are discussed. Bright field microscopy proved to be more simple and inexpensive and provided the best overall results.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/32329/2006, POCI/AMB/57069/200

The Influence Of Method And Environment In Torquing Screws Used In Bucket Wheel To Stacker-reclaimer Machine

Mining machines are of heavy-duty and robust type, and at the same time, they are keys to mining performance and operation. It is well known that mining environment is dirty and dusty as a whole, and this scenario contributes detrimentally for machines and equipment maintenance. This article reveals quantitatively the effect of the environment and the method in tightening screws to clamp the wheel buckets of a Stacker Reclaimer Machine at an Iron Ore Mining. For this study, a statistical tool called Minitab was utilized. The data were collected in the field during an intervention in the machine and treated statistically afterward. The elongations of the screws were measured by ultrasound which revealed that, when only torques are used to tighten the screws, referenced on the theoretical torque (N m) value, the aimed elongation (elastic strain) of screws might not be reached, with the worst case being it may be widely spread; the values obtained by ultrasound revealed such differences. After knowing such discrepancy, the screws were tightened properly to insure that the bucket wheel was correctly clamped. This statistical study quantified the spread values of torque versus elongation condition (bell curves). The ultrasound measurement credited the method utilized. © ASM International 2012.124382390Monaghan, J.M., The influence of lubrication on the design of yield tightened joints (1991) J. Strain Anal., 26 (2), pp. 124-129Luo, G.-P., Xu, L.J., Zhang, J.-G., Combination effect of fretting and corrosion on bolt-Type power connectors (2000) Proceedings Of The Forty-Sixth, pp. 60-66. , IEEE Holm Conference, Chicago(2011) Methods of Tightening Threads., , http://www.boltscience.com/pages/tighten.htm, Bolt ScienceMelkonian, S., (2009) Elementos de Máquinas, , 9a Ediçao(2010) Mechanical Engineering, , Shigley: Mechanical Engineering Design McGraw-Hill Series 9a Ediçao. McGraw-Hill, New York(2009), Minitab 15, User Manualhttp://www.metso.com, Catalogue-Metso Mining Productshttp://www.hytorc.com/products/hydraulic/avanti, Catalogue-AVANTI-Torque/Tension Machinehttp://www.ibt-usa.com/bolt_meter.html, Catalogue-USM-3 Ultrasonic Stress Mete

Phenolic compounds characterization by LC-DAD- ESI/MSn and bioactive properties of Thymus algeriensis Boiss. & Reut. and Ephedra alata Decne

Scientific research has been focused on finding natural occurring molecules from plant origin. Herein, infusion, decoction and hydroethanolic extracts of Thymus algeriensis Boiss. & Reut. and Ephedra alata Decne. from Algeria were phytochemically characterized by LC-DAD-ESI-MSn, and evaluated regarding bioactive properties (antioxidant and antibacterial). Flavonol and flavone glycoside derivatives and phenolic acids, specially rosmarinic acid and kaempferol-O-glucuronide were the major compounds in T. algeriensis extracts. Otherwise, E. alata presented isoflavones and flavonol derivatives as main compounds, being hydroxypuerarin isomer 1 the major molecule. Aqueous extracts had significantly higher antioxidant activity, being this activity correlated with the amount of phenolic compounds. Antimicrobial activity of the extracts was tested against multi-resistant bacteria strains from clinical isolates. The obtained MIC values indicate that the hydroethanolic extracts revealed the highest effect, especially the one of T. algeriensis against Gram-positive bacteria. Hence, these plant extracts could be used in the development of bioactive ingredients.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) and FEDER under Programme PT2020 for financial support to CIMO (UID/AGR/00690/2013), S. Heleno grant (SFRH/BPD/101413/2014) and L. Barros contract. The authors are also grateful to the Interreg España-Portugal for financial support through the project 0377_Iberphenol_6_E.info:eu-repo/semantics/publishedVersio

Infusions obtained from two medicinal plants as a source of polyphenols with antibacterial activity

Several researches are now oriented towards studying natural molecules of plant origin. In Algeria, many herbs are used as traditional remedies to treat different diseases. In this context, the phenolic compounds of the aqueous extracts, obtained by infusion, of two plant species, Saccocalyx satureioides Coss.& Dur and Limoniastrum guyonianum Boiss., from the Algerian flora, were identified and quantified by HPLC-DADESI/ MS, and their antibacterial activity was evaluated against clinical isolates. The results indicate the presence of several phenolic acids, in particular, derivatives of caffeic acid with glycosylated flavonoids. While for S. satureioides 13 phenolic compounds were identified and the rosmarinic acid was the most abundant phenolic acid, L. guyonianum showed a high abundance of myricetin and derivatives such as myricetin-3-O-glucoside and myricetin-O-rhamnoside among the eight molecules detected. The antibacterial activity of the infusions was significant with MIC values between 2.5 and 20 mg/mL, however, L. guyonianum had the highest activity on all the tested bacteria. Staphylococcus aureus and Pseudomonas aeruginosa were the most sensitive and the most resistant strains, respectively. Consequently, the studied plant species are sources of natural antibacterial substances that can be used to fight against pathogenic microorganisms.info:eu-repo/semantics/publishedVersio

Profiling polyphenol composition by HPLC-DAD-ESI/MSn and the antibacterial activity of infusion preparations obtained from four medicinal plants

The infusions of Thymus pallescens Noë, Saccocalyx satureioides Coss. et Dur., Ptychotis verticillata Briq. and Limoniastrum guyonianum Boiss. have been used as medicinal remedies for many diseases in Algerian folk medicine. These species have also been well documented as rich sources of phytochemicals, such as phenolic compounds with wide diversified chemical structures, which exhibit far-ranging biological activities. Thus, the phenolic compound profile of the aqueous extracts, obtained by infusing, of the mentioned species was obtained by HPLC-DAD-ESI/MS, and their antibacterial activity was evaluated against clinical isolates. Several phenolic acids were identified and quantified, particularly caffeic acid derivatives along with glycosylated flavonoids. T. pallescens and S. satureioides contain 13 phenolic compounds, where rosmarinic acid was the most abundant phenolic acid present, while L. guyonianum presented myricetin-3-O-glucoside and myricetin-O-rhamnoside as the main compounds among the eight detected molecules. P. verticillata presented a profile of ten phenolic compounds, where 5-O-caffeoylquinic acid was the most abundant phenolic acid, followed by the flavone luteolin-3-O-glucoside. The antibacterial activity of the infusions ranged between 2.5 and 20 mg mL−1 (MIC values), and L. guyonianum showed the highest activity against all of the tested bacteria, Staphylococcus aureus and Pseudomonas aeruginosa being the most sensitive and resistant strains, respectively. Thus, the studied plant species are sources of natural antibacterial substances that can be used to fight against pathogenic microorganisms.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) and FEDER under Programme PT2020 for financial support to CIMO (UID/AGR/00690/2013), S. Heleno (SFRH/BPD/101413/2014) grant and L. Barros contract. The authors are also grateful to the Interreg España- Portugal for financial support through the project 0377_Iberphenol_6_E.info:eu-repo/semantics/publishedVersio

Phenolic profiling, biological activities and in silico studies of Acacia tortilis (Forssk.) Hayne ssp. raddiana extracts

The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support through national funds FCT/MCTES to CIMO (UIDB/00690/2020). L. Barros and R. C. Calhelha thank the national funding by the FCT, P.I., through the institutional scientific employment program-contract for their contracts. M. Carocho also thanks the project ValorNatural for his research contract. The authors are also grateful to the FEDER-Interreg España- Portugal programme for financial support through the project 0377_Iberphenol_6_E.info:eu-repo/semantics/publishedVersio