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Viscous Materials (viscous + material)
Selected AbstractsVariations of sperm release in three batches of zebrafishJOURNAL OF FISH BIOLOGY, Issue 2 2004J. R. Kemadjou Njiwa By collecting and counting the number of sperm released during separate matings in three batches of zebrafish Danio rerio, aged 3,4, 4,5 and 5,6 months, males were observed to release sperm before the female started laying their eggs. After the female left the nest, the number and motility of sperm and life span of sperm of younger fish were higher than those of older fish in water samples collected under the nest and at the surface of the tank. Sperm were released in the form of sperm trails laid on the nest surface, subsequently active spermatozoa left the trails and moved in the water for several minutes. Sperm trails consisted of bands of viscous material in which the sperm were embedded. In most cases eggs were not laid directly over the sperm trail, suggesting that sperm may contact the eggs after the latter are released into the water. In all the three tested groups there was no significant difference (P > 0·05) between the number of sperm collected on some portions of the acetate sheets which lined the nest ceiling. This result demonstrated that the greater activity of younger fish accelerated the sperm dispersal in water. Male sperm duct glands, seminal vesicles, known to secrete mucosubstances are probably involved in the production of sperm trails. The possible influence of insemination on the mating style of zebrafish is discussed. [source] Characterization of ultrasound extrudated and cut citric acid/paracetamol blendsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2009P. Hoppu Abstract The purpose of the present work was to study the effect of ultrasound extrusion and cutting on the physical stability of a viscous and sticky supercooled melt containing (50/50, w/w, %) citric acid anhydrate and paracetamol. Samples were extrudated at temperatures of 50, 60, and 70°C using power levels of 0, 50, 100, and 150 W. Similarly, extrudates prepared at 60°C were cut at temperatures ranging from 25,60°C with an ultrasound knife in the range 0, 50, and 100 W. The characterization methods used were: high performance liquid chromatography, differential scanning calorimetry, Karl Fischer titration, X-ray powder diffraction, Fourier transform infrared microscopy, optical- and stereomicroscopy. There was no physical difference in extrudates or cut surfaces whether processed with or without ultrasound. During 1-year aging time in dry conditions, all the samples were observed to crystallize slowly and ultrasound processing did not enhance the crystallization. Ultrasound thus holds some promise for processing of viscous and sticky pharmaceuticals, provided the material is physically stable enough to withstand mechanical and thermal stress. Processing of sticky and viscous material would be difficult without ultrasound with the methods currently used in pharmaceutical industry. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:2140,2148, 2009 [source] Synthesis and characterization of low relative molecular weight trans -1,4-poly(isoprene)JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Huafeng Shao Abstract Low relative molecular weight trans-1,4-polyisoprene oligomers were synthesized successfully by bulk precipitation and solution polymerization with supported titanium catalyst using hydrogen as relative molecular weight modifier. The effects of polymerization conditions on intrinsic viscosity ([,]), catalyst efficiency (CE) and structure of polymer were studied. Increasing the hydrogen pressure resulted in the decrease of [,] of the polymer. With the increasing of hydrogen pressure and reaction temperature, CE decreased but still maintained above 2500 g polymer/g Ti. The percentage composition of (trans-1, 4-unit) in the polymer was over 90% in all results. The crystallinity of polymer was about 50,60% with Tm being about 60°C. The relative molecular weight distribution index (MWD) was quite difference according to the polymerization method. While number average molecular weight (Mn) exceeded 860, polymer turned from viscous materials to fragile wax materials, and then to toughness materials at 1800. Dynamic property testing showed that the additional of this oligomer could increase the wet-skid resistance of the rubber. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Reactive extrusion to synthesize intumescent flame retardant with a solid acid as catalyst and the flame retardancy of the products in polypropyleneJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Yuan Liu Abstract Reactive extrusion and solid acid catalysis technologies were adopted in the pentaerythritol,melamine phosphate (PER-MP) reaction to synthesize intumescent flame retardant, melamine salt of pentaerythritol phosphate (MPP), which was applied in flame retardant polypropylene (PP). This environment-friendly synthesis method provided a solution to the problems of conventional methods. On one hand, reactive extrusion in a twin screw extruder can effectively mix and transfer viscous materials that usually results in a tough stir in a conventional reactor, and achieve a continuous synthesis process. On the other hand, the solid acid, silicotungstic acid (STA) serving as a catalyst, can maintain a satisfactory conversion even with a low extrusion temperature and a short residence time, thus effectively suppressing foaming in the process of the reaction. Furthermore, without removal like other catalysts in general chemical reactions, STA was kept in produced MPP to constitute a synergism flame retardant system, therefore further improved the flame retardancy. LOI and UL94 test showed that the STA-catalyzed MPP (by reactive extrusion) possessed much better flame retardancy in PP when compared with the noncatalyzed MPP (by reactive extrusion), as well as present commercial MPP (by POCl3 method). In our investigation, the catalytic and synergistic effects of STA, as well as the related factors of the reactive extrusion affecting the conversion of the PER-MP reaction, flame retardancy and mechanical performance of the corresponding flame retardant PP, were systematically investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Magnetic signal prospecting using multiparameter measurements: the case study of the Gallic Site of LevrouxARCHAEOLOGICAL PROSPECTION, Issue 3 2010M. Pétronille Abstract The ,magnetic signal' that combines both the induced (Ji) and the remanent (Jr) magnetization is widely used in archaeological and pedological prospecting. Magnetic prospecting recording the lateral variations of the total magnetization is the most frequently used measurement before in-phase magnetic susceptibility (Kph) and magnetic viscosity (Kqu) mapping. The work presented here brings together three types of prospecting technique: magnetic field survey and electromagnetic measurements with both frequency and time domain devices that measure magnetic susceptibility and viscosity respectively. The site studied, the Gallic town of Levroux (Indre, France), is particularly interesting because it includes features such as pits and ditches dug into the calcareous substratum partly filled with topsoil and with residues of different metallurgical and fire activities. The field results indicated anomalies with different types of characterization: (i) many compact features filled with magnetic, electrically conductive and minimally viscous materials; and (ii) elongated anomalies characterized by lower magnetic properties and electric conductivity but relatively higher magnetic viscosity than those of the compact features. In addition to the location of the features, the combination of the information brought by the different types of measurements allows us to evaluate the possible erosion of their upper parts by ploughing, to assess their depth (never deeper than 1.30,m) and to precise the nature of the feature's fill. Copyright © 2010 John Wiley & Sons, Ltd. [source] | ||||||||||