An advanced design method for propellers behind bodies of revolutionCalcul de l'hélice fonctionnant en arrière d'un corps à symétrie axiale

The flow around the unshrouded marine propellers operating in the wake of an axisymmetric body is rotational and tridimensional. An inverse method based on the model of inviscid and rotational fluid and coupling two complementary steps (axisymmetric computation + 3D panel method) is proposed for the design of the marine propellers. The meridional flow computation leads to the determination of axisymmetrical stream sheets as well as the approximate camber surface of the blades and gives a good estimation of the surface of the free vortex wake. The new aspects developed in this method are the involvement of the contraction and the stretching of the free vortex wake, the rotational character of the incoming flow in the axisymmetric computation with tridimensional effects due to 3D panel method. To cite this article: N. Settou, B. Viney, C. R. Mecanique 331 (2003).     

Novel bis-(3-cyano-2-pyridones) derivatives: synthesis and fluorescent properties

Research on Chemical Intermediates - Novel substituted bis-(3-cyano-2-pyridone) derivatives were prepared via a powerful method using enaminonitriles push–pull dienes as key building blocks....     

Chemical Composition and Antioxidant,Anti-Inflammatory,and Enzyme Inhibitory Activities of an Endemic Species from Southern Algeria: Warionia saharae

Warionia saharae Benth. & Coss. (Asteraceae) is an endemic species of North Africa naturally grown in the southwest of the Algerian Sahara. In the present study, this species’ hydromethanolic leaf extract was investigated for its phenolic profile characterized by ultra-high-performance liquid chromatography coupled with a diode array detector and an electrospray mass spectrometer (UHPLC-DAD-ESI/MS). Additionally, the chemical composition of W. saharae was analyzed by gas chromatography–mass spectrometry, and its antioxidant potential was assessed through five in vitro tests: DPPH^● scavenging activity, ABTS^●+ scavenging assay, galvinoxyl scavenging activity, ferric reducing power (FRP), and cupric reducing antioxidant capacity. The UHPLC-DAD-ESI/MS analysis allowed the detection and quantification of 22 compounds, with taxifolin as the dominant compound. The GC–MS analysis allowed the identification of 37 compounds, and the antioxidant activity data indicate that W. saharae extract has a very high capacity to capture radicals due to its richness in compounds with antioxidant capacity. The extract also showed potent α-glucosidase inhibition as well as a good anti-inflammatory activity. However, weak anti-α-amylase and anticholinesterase activities were recorded. Moreover, an in silico docking study was performed to highlight possible interactions between three significant compounds identified in W. saharae extract and α-glucosidase enzyme.     

Influence of morphological and conformational changes on the molecular mobility in poly(ethylene naphthalene-2,6-dicarboxylate)

Dynamic electric (DEA) and mechanical (DMA) analyses were combined to explore the relaxational processes in amorphous and semicrystalline poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) samples. Differential scanning calorimetry measurements were carried out to investigate the crystallinity of the samples following isothermal annealing treatment at 443 K. The two secondary relaxations β and β*, the main α relaxation, as well as the ρ-relaxational process, were revealed by both electric and mechanical viscoelastic responses of the PEN samples. DMA results clearly identified the above T_α loss factor peak, ρ, as a probe of the cold crystallization. However, the association of both DMA and DEA investigations pointed out that electric and non-electric aspects might govern the ρ-process.     

Bioactive Compounds from Ephedra fragilis: Extraction Optimization,Chemical Characterization,Antioxidant and AntiGlycation Activities

Response surface methodology (RSM) with a Box–Behnken design (BBD) was used to optimize the extraction of bioactive compounds from Ephedra fragilis. The results suggested that extraction with 61.93% ethanol at 44.43 °C for 15.84 h was the best solution for this combination of variables. The crude ethanol extract (CEE) obtained under optimum extraction conditions was sequentially fractionated with solvents of increasing polarity. The content of total phenolic (TP) and total flavonoid (TF) as well as the antioxidant and antiglycation activities were measured. The phytochemical fingerprint profile of the fraction with the highest activity was characterized by using RP-HPLC. The ethyl acetate fraction (EAF) had the highest TP and TF contents and exhibited the most potent antioxidant and antiglycation activities. The Pearson correlation analysis results showed that TP and TF contents were highly significantly correlated with the antioxidant and antiglycation activities. Totally, six compounds were identified in the EAF of E. fragilis, including four phenolic acids and two flavonoids. Additionally, molecular docking analysis also showed the possible connection between identified bioactive compounds and their mechanisms of action. Our results suggest new evidence on the antioxidant and antiglycation activities of E. fragilis bioactive compounds that may be applied in the treatment and prevention of aging and glycation-associated complications.     

Implementation of a Biometric Interface in Voice Controlled Wheelchairs

In order to assist physically handicapped persons in their movements, we developed an embedded isolated word speech recognition system (ASR) applied to voice control of smart wheelchairs. However, in spite of the existence in the industrial market of several kinds of electric wheelchairs, the problem remains the need to manually control this device by hand via joystick; which limits their use especially by people with severe disabilities. Thus, a significant number of disabled people cannot use a standard electric wheelchair or drive it with difficulty. The proposed solution is to use the voice to control and drive the wheelchair instead of classical joysticks. The intelligent chair is equipped with an obstacle detection system consisting of ultrasonic sensors, a moving navigation algorithm and a speech acquisition and recognition module for voice control embedded in a DSP card. The ASR architecture consists of two main modules. The first one is the speech parameterization module (features extraction) and the second module is the classifier which identifies the speech and generates the control word to motors power unit. The training and recognition phases are based on Hidden Markov Models (HMM), K-means, Baum-Welch and Viterbi algorithms. The database consists of 39 isolated speaker words (13 words pronounced 3 times under different environments and conditions). The simulations are tested under Matlab environment and the real-time implementation is performed by C language with code composer studio embedded in a TMS 320 C6416 DSP kit. The results and experiments obtained gave promising recognition ratio and accuracy around 99% in clean environment. However, the system accuracy decreases considerably in noisy environments, especially for SNR values below 5 dB (in street: 78%, in factory: 52%).     

Polysaccharide Chemistry in Drug Delivery,Endocrinology, and Vaccines

Polysaccharides, due to their outstanding properties, have attracted the attention of researchers, working in the biomedical field and especially of those working in drug delivery. Modified/functionalized polysaccharides further increase the importance for various applications. Delivery of therapeutics for diverse ailments in different endocrine glands and hormones safely, is a focal point of researchers working in the field. Among the routes followed, the transdermal route is preferred due to non-exposure of active moieties to the harsh gastric environment and first-pass metabolism. This review starts with the overview of polysaccharides used for the delivery of various therapeutic agents. Advantages of polysaccharides used in the transdermal route are addressed in detail. Types of polysaccharides will be elaborated through examples, and in this context, special emphasis will be on the polysaccharides being used for synthesis of the membranes/films. Techniques employed for their modification to design novel carriers for therapeutics delivery will also be discussed. The review will end with a brief discussion on recent developments and future perspectives for delivery of therapeutic agents, and vaccine development.     

Changes in sugar composition and cellulose content during the secondary cell wall biogenesis in cotton fibers

Two cotton cultivars TX19 and TX55 (Gossypium hirsutum L. cv.) were planted in the greenhouse and fibers were harvested at different stages of development. The percentage of sugars present on the fibers was determined by High Performance Liquid Chromatography and the cellulose content was determined using the anthrone method. The percentage of sugars (sucrose, glucose, fructose, and galacturonic acid) showed statistically significant changes during fiber development. The decrease in the percentages of these sugars as the secondary cell wall develops was associated with an increase in the cellulose content. It is important to point out that these analyses were done on intact fibers, no cell wall extractions and purifications were performed.     

Sorption study of an anionic dye - benzopurpurine 4B - on calcined and uncalcined Mg-Al layered double hydroxides

In this paper, the elimination from aqueous solution of the pollutant benzopurpurine 4B by Mg-Al-CO₃ hydrotalcite and its modified form Mg-Al-500 has been studied. Mg-Al-CO₃²⁻ layered double hydroxide with an Mg/Al molar ratio of 2.0 was synthesized by the co-precipitation method, and its modification was carried out by calcination. The affinity of these materials with a mixture of benzopurpurine 4B was studied as a function of dye-adsorbent contact time, initial pH of the solution, initial dye concentration and temperature. The results indicate that HDLs were effective in removing benzopurpurine 4B anionic dye. Their saturated adsorption capacities are very high, particularly for the calcined material Mg-Al-500 compared to the standard one Mg-Al-CO₃²⁻.The characterisation of the solid Mg-Al-500, both fresh and after removal of the dye by X-ray diffraction and infrared spectroscopy, shows that the benzopurpurine 4B adsorption on this calcined phase is enhanced by reconstruction of a matrix hydrotalcite intercalated by the dye, with basal spacing of 23.77 Å, which is larger than that of Mg-Al-CO₃²⁻ LDHs (7.57 Å).     

Evaluation of the acoustic and non-acoustic properties of sound absorbing materials using a three-microphone impedance tube

This paper presents a straightforward application of an indirect method based on a three-microphone impedance tube setup to determine the non-acoustic properties of a sound absorbing porous material. First, a three-microphone impedance tube technique is used to measure some acoustic properties of the material (i.e., sound absorption coefficient, sound transmission loss, effective density and effective bulk modulus) regarded here as an equivalent fluid. Second, an indirect characterization allows one to extract its non-acoustic properties (i.e., static airflow resistivity, tortuosity, viscous and thermal characteristic lengths) from the measured effective properties and the material open porosity. The procedure is applied to four different sound absorbing materials and results of the characterization are compared with existing direct and inverse methods. Predictions of the acoustic behavior using an equivalent fluid model and the found non-acoustic properties are in good agreement with impedance tube measurements.