An experimental study of gas void fraction in dilute alcohol solutions in annular gap bubble columns using a four-point conductivity probe

The influence of alcohol concentration on the gas void fraction in open tube and annular gap bubble columns has been investigated using a vertical column with an internal diameter of 0.102 m, containing a range of concentric inner tubes which formed an annular gap; the inner tubes had diameter ratios from 0.25 - 0.69. Gas (air) superficial velocities in the range 0.014-0.200 m/s were investigated. Tap water and aqueous solutions of ethanol and isopropanol, with concentrations in the range 8 - 300 ppm by mass, were used as the working liquids. Radial profiles of the local void fraction were obtained using a four-point conductivity probe and were crosssectionally averaged to give mean values that were within 12% of the volumeaveraged gas void fractions obtained from changes in aerated level. The presence of alcohol inhibited the coalescence between the bubbles and consequently increased the mean gas void fraction at a given gas superficial velocity in both the open tube and the annular gap bubble columns. This effect also extended the range of homogeneous bubbly flow and delayed the transition to heterogeneous flow. Moreover, isopropanol results gave slightly higher mean void fractions compared to those for ethanol at the same mass fraction, due to their increased carbon chain length. It was shown that the void fraction profiles in the annular gap bubble column were far from uniform, leading to lower mean void fractions than were obtained in an open tube for the same gas superficial velocity and liquid composition

Experimental study of void fraction behaviour in vertical bubbly gas-liquid flow using conductivity and measurements

The void fraction is an important variable in describing gas-liquid two-phase flows, since it is required to predict the heat and mass transfer coefficients and the pressure drop and is an indicator of the flow regime. The contrast in conductivity between water and air is one way to measure the void fraction in gas-liquid flow. This project has examined use of the ring conductivity electrodes to measuring the void fraction in an up-flow bubble column. The conductivity method has potential to be a low cost, safe and accurate method of measuring local void fractions in pipes and other process engineering mass transfer devices. In this project, the void fraction was measured in an air-water system by using conductivity in a 2" pipe equipped with two ring electrodes. Further gas hold-up experiments were conducted in the annular channel formed between 2" and a 4" pipe, using a system of four pairs of electrodes. The data obtained from the experiments agreed fairly well with the Maxwell and Burggeman theories which relate the dimensionless conductance to the void fraction. The measured void fractions were correlated using the drift-flux model, as proposed by Zuber and Findlay. Significant differences were observed between the void fraction measurements obtained for the annular channel and for an empty pipe, when operated at the same gas superficial velocity

Destabilisation of a homogeneous bubbly flow in an annular gap bubble column

Experimental results are presented to show that there are very significant differences in the mean gas void fractions measured in an open tube and a annular gap bubble column, when operated at the same gas superficial velocity, using a porous sparger. The mean gas void fraction decreases with increasing ratio of the inner to outer diameter of the annular gap column and the transition to heterogeneous flow occurs at lower gas superficial velocities and lower void fractions. Two reasons are proposed and validated by experimental investigations: (1) the presence of the inner tube causes large bubbles to form near the sparger, which destabilize the homogeneous bubbly flow and reduce the mean void fraction; this was confirmed by deliberately injecting large bubbles into a homogeneous dispersion of smaller bubbles and (2) the shape of the void fraction profiles changes with gap geometry and this affects the distribution parameter in the drift flux model

Destabilisation of a homogeneous bubbly flow in an annular gap bubble column

Destabilisation of a homogeneous bubbly flow in an annular gap bubble colum

A novel NGF mutation clarifies the molecular mechanism and extends the phenotypic spectrum of the HSAN5 neuropathy

Background Nerve growth factor beta (NGF beta) and tyrosine kinase receptor type A (TRKA) are a well studied neurotrophin/receptor duo involved in neuronal survival and differentiation. The only previously reported hereditary sensory neuropathy caused by an NGF mutation, c.661C>T (HSAN5), and the pathology caused by biallelic mutations in the TRKA gene (NTRK1) (HSAN4), share only some clinical features. A consanguineous Arab family, where five of the six children were completely unable to perceive pain, were mentally retarded, did not sweat, could not discriminate temperature, and had a chronic immunodeficiency, is reported here. The condition is linked to a new homozygous mutation in the NGF gene, c. [680C>A]+[681_682delGG].Methods Genetic linkage and standard sequencing techniques were used to identify the causative gene. Using wild-type or mutant over-expression constructs transfected into PC12 and COS-7 cells, the cellular and molecular consequences of the mutations were investigated.Results The mutant gene produced a precursor protein V232fs that was unable to differentiate PC12 cells. V232fs was not secreted from cells as mature NGF beta.Conclusions Both the clinical and cellular data suggest that the c.[680C>A]+[ 681 682delGG] NGF mutation is a functional null. The HSAN5 phenotype is extended to encompass HSAN4-like characteristics. It is concluded that the HSAN4 and HSAN5 phenotypes are parts of a phenotypic spectrum caused by changes in the NGF/ TRKA signalling pathway

An experimental study of gas void fraction in dilute alcohol solutions in annular gap bubble columns using a four-point conductivity probe

This is the author’s version of a work that was accepted for publication in the journal Chemical Engineering Science. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published at: http://dx.doi.org/10.1016/j.ces.2011.03.061The influence of alcohol concentration on the gas void fraction in open tube and annular gap bubble columns has been investigated using a vertical column with an internal diameter of 0.102 m, containing a range of concentric inner tubes which formed an annular gap; the inner tubes had diameter ratios from 0.25 - 0.69. Gas (air) superficial velocities in the range 0.014-0.200 m/s were investigated. Tap water and aqueous solutions of ethanol and isopropanol, with concentrations in the range 8 - 300 ppm by mass, were used as the working liquids. Radial profiles of the local void fraction were obtained using a four-point conductivity probe and were crosssectionally averaged to give mean values that were within 12% of the volumeaveraged gas void fractions obtained from changes in aerated level. The presence of alcohol inhibited the coalescence between the bubbles and consequently increased the mean gas void fraction at a given gas superficial velocity in both the open tube and the annular gap bubble columns. This effect also extended the range of homogeneous bubbly flow and delayed the transition to heterogeneous flow. Moreover, isopropanol results gave slightly higher mean void fractions compared to those for ethanol at the same mass fraction, due to their increased carbon chain length. It was shown that the void fraction profiles in the annular gap bubble column were far from uniform, leading to lower mean void fractions than were obtained in an open tube for the same gas superficial velocity and liquid composition

From Boatyard to Museum: 3D laser scanning and digital modelling of the Qatar Museums watercraft collection, Doha, Qatar

This is the final version of the article. Available from Wiley via the DOI in this record.This article presents the results of a project to 3D laser scan and digitally model 14 watercraft from the Qatar Museums collection, comprising a range of regional vessels: most had not been surveyed previously. The project used the resulting point clouds generated 2D naval lines and orthographic records of the vessels in their current condition, and photorealistic 3D digital models for gallery display. This case study provides illustrative examples of the intermediate stages and final outputs. It assesses the pros and cons of 3D laser scanning as a survey technology for nautical scholars in terms of the time, cost, and skillset, as well as logistical considerations. It also compares the accuracy of traditional hand survey methods.We wish to thank QM for enabling and funding this research (Grant number SL-05894)

Centrifuge modelling of wet deep mixing processes in soft clays

Ph.DDOCTOR OF PHILOSOPH

Seeking Relevance in a Social Media Age: A Guide for the FRAXA Research Foundation

The purpose of this project was to provide the FRAXA Research Foundation with recommendations for improving social media presence on Facebook, Twitter, and YouTube. By performing a SWOT analysis, creating experiments, and analyzing data from social media accounts, we demonstrated the importance of posting frequently, tailoring content to specific audiences, and cross-posting to maintain a strong social media presence. These strategies will help FRAXA increase outreach and obtain a higher likelihood of donors and volunteers dedicated to advancing FRAXA's mission

Experimental study on bubbly flow transition in vertical annular gap bubble column

Mean and local gas void fractions in vertical upward, two-phase flows contained within the annular gap between two concentric tubes are presented. For a given gas superficial velocity, jg, the mean void fraction, , was found to decrease as the diameter ratio of the two tubes approached unity (i.e. for narrower gaps). Moreover, was significantly lower than that obtained in an open tube at the same jg. Two explanations were proposed: (i) large bubbles, generated in the annular gap, destabilised the flow, and (ii) the driftflux distribution parameter in an open tube was different to that in an annular gap, which results in a different mean . It was shown that injection of large bubbles into a homogeneous flow led to an early transition. Furthermore, the void fraction profiles in the annular gaps depended on both jg and the gap geometr