The indentation behaviour of carbon fibre composite tubes-experiments & modelling

Metallic tubes have been extensively studied for their crashworthiness as they closely resemble automotive crash rails. Recently, the demand to produce lighter weight, yet safer vehicles has led to the need to understand the crash behaviour of novel materials, such as fibre reinforced polymer composites, metallic foams and sandwich structures. This paper discusses the static indentation response of Carbon Fibre Reinforced Polymer (CFRP) tubes. The side impact on a CFRP tube involves various failure mechanisms. This paper highlights these mechanisms and compares the energy absorption of CFRP tubes with similar Aluminium tubes. The response of the CFRP tubes during bending was modelled using ABAQUS finite element software with a composite fabric material model. The material inputs were given based on standard tension and compression test results and the in-plane damage was defined based on cyclic shear tests. The failure modes and energy absorption observed during the tests were well represented by the finite element model.

Sperm cells of the pollen tubes of Brassica : ultrastructure and isolation

Sperm cells of pollen tubes grown both in vivo and in vitro form a male germ unit. Extensions from both sperm cells of each pollen tube are closely associated with the tube nucleus. A high yield (2.7 × 104. 20 mg−1 pollen grains germinated) of intact sperm cells was obtained following release by osmotic shock from pollen tubes grown in vitro. Structural integrity of isolated sperm was maintained by isolation at low temperature in an osmotically balanced medium. At 4° C many isolated sperm pairs were still enclosed within the pollentube inner plasma membrane. Sperm cells not enclosed within this membrane no longer remained connected as a pair. During isolation vesicles formed on the sperm cell surface from disruption of the fibrillar components bridging the periplasmic space. Both in the pollen tube and after isolation the sperm nucleus is in close association with at least one region of the sperm plasma membrane. Sperm isolated at room temperature showed the presence of nucleopores, and nuclei were euchromatic, instead of heterochromatic as in intact sperm in the pollen tube.

Ultrastructural analysis of plastids in angiosperm pollen tubes

When Rhododendron pollen tubes are cultured in the dark, electron-dense bodies are present that appear to be a metabolically altered form of a proplastid that is difficult to fix for electron microscopy, and whose membranes may not be intact. When similar pollen tubes are cultured in a dark/light regime, ultrastructurally well-defined proplastids are present after fixation in glutaraldehyde with PIPES buffer and tannic acid, followed by osmic acid. This fixation technique also gave the best ultrastructural images of those proplastids in pollen tubes grown in the dark. Pollen tube plastids have the potential to become chromoplasts when cultured in a dark/light regime as evidenced by the presence of branched tubules characteristic of these organelles. Light appears to be a hitherto neglected environmental factor involved in regulating pollen tube growth. This improved fixation procedure demonstrates the bilayered nature of the membranes surrounding sperm cells and the existence of cytoplasmic channels connecting sperm cell and pollen tube plasma membranes.

Medication administration via enteral tubes : a survey of nurses' practices

Aim: This article is a report of a study examining the practices of acute care nurses when administering medication via enteral tubes. Background. Administering medication via enteral tubes is predominantly a nursing responsibility across countries. It is important to establish what nurses actually do when giving enteral medication to inform policy and continuing education development.

Method: In 2007, a survey was conducted using a random sample of acute care nurses at two large metropolitan hospitals in Melbourne, Australia. There were 181 Registered Nurses who participated in the study; 92 (50Æ8%) practised in intensive care units, 52 (28Æ7%) in surgical areas, 30 (16Æ6%) in medical areas and 7 (3Æ9%) were from combined medical–surgical areas. The questionnaire was developed by the researchers and a pilot study was conducted in August 2006 to test reliability, face validity and user-friendliness of the tool.

Results: Nurses reported using a range of methods to verify enteral tube position prior to administering enteral medication; some were unreliable methods. A majority reported administering enteric-coated and slow or extended release forms of medication, and giving solid forms of medication when liquid form was available. Nearly all (96%) reported flushing a tube after giving medication, 28% before, and 12% always flushed between each medication.

Conclusion: Enteral medication administration practices are inconsistent. Some nurses are using unsafe practices and may therefore compromise patient care.

Impact response and energy absorption of aluminium foam-filled tubes

The effect of foam fillers on the impact behaviour and energy absorption of an aluminium tube is investigated. Both experimental test and computational simulation are employed in current study. For comparison, hollow tubes and foams are also tested, respectively. Foam filler is found to be ineffective in increasing the crushing loads of the composite tubes over the simple superposition of the crushing loads of hollow tube and foam. Also, foam filler increases the tendency for the concertina mode of folding. The foam fillers of tubes additionally result in increasing the SAE values over those of hollow tubes.

A study on bending behaviours of aluminium foam-filled tubes

In the study, the strengthening effect of aluminium foam in thin-walled aluminium tubes subject to bending load in investigated experimentally and numerically. Bending tests are conducted on foam filler, hollow tube and foam-filled tube. The finite element method is used as well to get deeper insight into the crush failure modes via focusing on the influence from wall thickness of the tube. The obtained information is useful to optimally design foam-filled tubes as energy absorbing devices in automotive engineering. The optimisation results can be implemented to find an optimum foam-filled tube that absorbs the same energy as the optimal hollow tube but with much less weight. © (2014) Trans Tech Publications, Switzerland.

Chemical and microbiological evaluation of the internal surfaces of aluminum tubes both unlined and lined with epoxi resin by means of the stereoscope and scanning electron microscope

A superfície interna das bisnagas fabricadas com alumínio não revestido e revestido com resina epóxi, utilizadas para acondicionar cremes, pomadas, géis, etc., foram avaliadas quimicamente e por métodos microbiológicos correlacionados com a aderência de microrganismos. A prova da porosidade e da resistência à remoção da resina foi observada por meio do microscópio eletrônico de varredura (Topcon FM300) e estereoscópio Leica (MZ12) acoplado a Sistema de Digitalização de Imagens. Para avaliar a ação dos microrganismos foram utilizados corpos-de-prova esterilizados (discos de 10mm de diâmetro), imersos em caldo Mueller Hinton (Difco) e colocados em tubos de polipropileno com tampa de rosca (Corning). Foram inoculados tubos com meio de cultura para cada uma das suspensões bacterianas (10(9)UFC/mL) de Streptococcus agalactiae, Staphylococcus aureus, Acinetobacter lwoffii e Candida albicans, incubados a 37°C, sob agitação constante durante 12 dias. O meio de cultura era trocado a cada 3 dias. Após esse período, os corpos-de prova foram removidos, processados e observados em microscópio eletrônico de varredura JEOL-JSM (T330A). A observação por meio do microscopio eletrônico de varredura mostrou a aderência e a formação de biofilme sobre a superfície de alumínio não revestido e revestido com resina epóxi.

Numerical analysis of refrigerant flow along non-adiabatic capillary tubes using a two-fluid model

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A mathematical model for wave propagation in elastic tubes with inhomogeneities: Application to blood waves propagation

We study the propagation of waves in an elastic tube filled with an inviscid fluid. We consider the case of inhomogeneity whose mechanical and geometrical properties vary in space. We deduce a system of equations of the Boussinesq type as describing the wave propagation in the tube. Numerical simulations of these equations show that inhomogeneities prevent separation of right-going from left-going waves. Then reflected and transmitted coefficients are obtained in the case of localized constriction and localized rigidity. Next we focus on wavetrains incident on various types of anomalous regions. We show that the existence of anomalous regions modifies the wavetrain patterns. (c) 2007 Elsevier B.V. All rights reserved.

Demulsification of water/sunflower oil emulsions by a tangential filtration process using chemically impregnated ceramic tubes

A tangential filtration process was implemented in this study using porous ceramic tubes made of alpha-alumina produced by the slip-casting technique. These tubes were sintered at 1450 degrees C and characterized by mercury intrusion porosimetry, which revealed a mean pore size of 0.5 mu m. The tubes were chemically impregnated with a zirconium citrate solution, after which they were calcined and heat treated at temperatures of up to 600 and 900 degrees C to eliminate volatile organic compounds and transform the zirconium citrate into zirconium oxide impregnated in the alumina in the form of nanoparticle agglomerates. The microporous pipes were tested on a microfiltration hydraulic system to analyze their performance in the demulsification of sunflower oil and water mixtures. The fluid-dynamic parameters of Reynolds number and transmembrane pressure were varied in the process. The volume of permeate was analyzed by measuring the Total Organic Carbon concentration (TOC), which indicated 99% of oil phase retention. The emulsified mixture was characterized by optical microscopy, while the morphology and composition of the impregnated microporous tubes were analyzed by scanning electron microscopy (SEM). Quantification of the TOC values for the tube impregnated once at 600 degrees C showed the best demulsification performance, with the concentration on permeate smaller than 10 mg/L. The impregnated tube sintered once at 900 degrees C presented low carbon concentration (smaller than 20 mg/L), has the advantage of presenting the greatest trans-membrane flux in relation to the other microporous tube. (c) 2006 Elsevier B.V. All rights reserved.

Comparison of metallic and ceramic tubes as atomization cells for tin determination by TS-FF-AAS

This work describes the development of an analytical procedure for on-line tin determination using thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS). Two tubes were evaluated as atomization cells: a metallic tube (Ni-Cr, principal components composition: 73.95% Ni and 16.05% Cr) and a ceramic tube (99.8% Al2O3). The use of air as the carrier was made by employing a Rheodyne valve to inject the samples, allowing an analytical frequency of 90 h(-1) and avoiding sample dispersion. The carrier flow rate (air), sample volume injected, and acid concentration (HCl) were evaluated for the optimization of the TS-FF-AAS system. The sensitivity for 50 mL of analytical solution with TS-FF-AAS was 2 and 5 times higher (to metallic and ceramic tube, respectively) than using an acetylene-nitrous oxide flame with pneumatic aspiration (requiring a sample volume of approximately 20 times higher.

Construction and calibration of permeation tubes.

A dynamic system for stablishing a known standard gas mixture is necessary for many studies such as development and testing of analytical methods. A permeation tube can be used for this purpose. The work described here shows the construction, operation and calibration of a simple permeation tube which can be used to obtain large amounts of a standard gas.

Reaction of rat connective tissue to implanted dentin tubes filled with mineral trioxide aggregate or calcium hydroxide

This study was conducted to observe the rat subcutaneous connective tissue reaction to the implanted dentin tubes filled with calcium hydroxide or mineral trioxide aggregate. The animals were sacrificed after 7 and 30 days, and the specimens were prepared for morphological study. Some undecalcified specimens were prepared for histological analysis with polarized light and Von Kossa technique for calcium. The results were similar for both studied materials. At the tube openings, there were Von Kossa-positive granules that were birefringent to polarized light. Next to these granulations, there was an irregular tissue like a bridge that was Von Kossa-positive. The dentin walls of the tubes exhibited in the tubules a structure highly birefringent to polarized light, usually like a layer and at different depths. It is possible that the mechanism of action of both materials has some similarity. Copyright © 1999 by The American Association of Endodontists.