The charge effect on the hindrance factors for diffusion and convection of a solute in pores II

The diffusion and convection of a solute suspended in a fluid across porous membranes are known to be reduced compared to those in a bulk solution, owing to the fluid mechanical interaction between the solute and the pore wall as well as steric restriction. If the solute and the pore wall are electrically charged, the electrostatic interaction between them could affect the hindrance to diffusion and convection. In this study, the transport of charged spherical solutes through charged circular cylindrical pores filled with an electrolyte solution containing small ions was studied numerically by using a fluid mechanical and electrostatic model. Based on a mean field theory, the electrostatic interaction energy between the solute and the pore wall was estimated from the Poisson-Boltzmann equation, and the charge effect on the solute transport was examined for the solute and pore wall of like charge. The results were compared with those obtained from the linearized form of the Poisson-Boltzmann equation, i.e.the Debye-Hückel equation. © 2012 The Japan Society of Fluid Mechanics and IOP Publishing Ltd.

The influence of excipients on the diffusion of ibuprofen and paracetamol in gastric mucus

The aim of this study was to examine the diffusion of commonly administered analgesics, ibuprofen and paracetamol, through gastric mucus. As ibuprofen and paracetamol are often formulated with alkalising excipients, or are commonly co-administered with antacids that have been demonstrated to alter their absorption, diffusion was also studied in the presence of a range of soluble and insoluble antacids or buffering agents. The effect of pH, which has been demonstrated to modify the properties of mucus, was also studied. Mucus was a significant barrier to diffusion for both drugs, compared to an unstirred aqueous layer with diffusion rates significantly lower in the presence of a mucus barrier for both drugs; ibuprofen diffusion also demonstrated a significant increase in the lag time. Paracetamol diffusion was not significantly affected by addition of any antacid, whereas ibuprofen rates were affected and the diffusion lag time for ibuprofen was significantly reduced in all cases. Isolated increases in pH increased the rate and reduced the lag time for ibuprofen diffusion. It was shown that mucus acts as a passive barrier in the case of paracetamol diffusion, and an interactive barrier to ibuprofen diffusion. Changes in mucus viscosity at different pH values may be responsible for the observed changes in ibuprofen diffusion rate. © 2004 Elsevier B.V. All rights reserved.

Diffuse beta-amyloid (A beta) deposits and neurons: in situ secretion or diffusion of A beta?

The association between diffuse-type beta -amyloid (AP) deposits and neuronal cell bodies in Alzheimer's disease (AD) and Down's syndrome (DS) could result from the secretion of AP from clusters of neurons in situ or the diffusion of A beta from cell processes, glial cells or blood vessels. To decide between these hypotheses, spatial pattern analysis was used to study the relationship between the degree of clustering of neuronal cell bodies and the presence of diffuse deposits in the temporal lobe of patients with DS. Significant clustering of neuronal cell bodies was present in 17/24 (71%) of brain areas studied. in addition, in 23/24 (96%) of brain areas, there was a positive correlation between the presence of diffuse deposits and the density of neurons. Hence, the data support the hypothesis that diffuse deposits develop in situ mainly as a result of the secretion of A beta by local clusters of neurons rather than by significant diffusion. Furthermore, the size of a diffuse deposit is likely to be determined by the number of neurons within a cluster which secrete A beta. The number and density of neurons could also be a factor determining the evolution of a diffuse into a mature amyloid deposit.

Charge effects on hindrance factors for diffusion and convection of solute in pores I

The transport of a spherical solute through a long circular cylindrical pore filled with an electrolyte solution is studied numerically, in the presence of constant surface charge on the solute and the pore wall. Fluid dynamic analyses were carried out to calculate the flow field around the solute in the pore to evaluate the drag coefficients exerted on the solute. Electrical potentials around the solute in the electrolyte solution were computed based on a mean-field theory to provide the interaction energy between the charged solute and the pore wall. Combining the results of the fluid dynamic and electrostatic analyses, we estimated the rate of the diffusive and convective transport of the solute across the pore. Although the present estimates of the drag coefficients on the solute suggest more than 10% difference from existing studies, depending on the radius ratio of the solute relative to the pore and the radial position of the solute center in the pore, this difference leads to a minor effect on the hindrance factors. It was found that even at rather large ion concentrations, the repulsive electrostatic interaction between the charged solute and the pore wall of like charge could significantly reduce the transport rate of the solute.

Diffusion of technology in flour milling and the emergence of the modern British milling industry

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Intermediation for technology diffusion and user innovation in a developing rural economy:a social learning perspective

Technology intermediaries are seen as potent vehicles for addressing perennial problems in transferring technology from university to industry in developed and developing countries. This paper examines what constitutes effective user-end intermediation in a low-technology, developing economy context, which is an under-researched topic. The social learning in technological innovation framework is extended using situated learning theory in a longitudinal instrumental case study of an exemplar technology intermediation programme. The paper documents the role that academic-related research and advisory centres can play as intermediaries in brokering, facilitating and configuring technology, against the backdrop of a group of small-scale pisciculture businesses in a rural area of Colombia. In doing so, it demonstrates how technology intermediation activities can be optimized in the domestication and innofusion of technology amongst end-users. The design components featured in this instrumental case of intermediation can inform policy making and practice relating to technology transfer from university to rural industry. Future research on this subject should consider the intermediation components put forward, as well as the impact of such interventions, in different countries and industrial sectors. Such research would allow for theoretical replication and help improve technology domestication and innofusion in different contexts, especially in less-developed countries.

Between a rock and a hard place:exploring women's experience of participation and progress in managerial careers

Purpose – The growth of women in management has been argued to offer a route to reduce organizational and social inequality. The purpose of this paper is to explore the careers and experiences of female managers from a variety of organizations operating in the West Midlands region of the UK. Design/methodology/approach – This study is based on 56 interviews conducted with women managers within various sectors. The interviewees also completed pictorial careers maps, which along with interview recordings were analyzed. Findings – The key themes to emerge from this research centre upon the factors that draw women into management (which we term seductive elements) as well as some of the hindering practices that prevent women from progressing. Significantly, we find that managerial careers are associated with gendered assumptions and practices (e.g. facilitating and developing people) which contribute to construct management (done by women) as bounded-up characteristically with “feminized” behaviours. Research limitations/implications – The research is based upon a relatively small sample that is multi-sectorial. Wider studies that increase population size, together with deeper studies that hold sectorial variables constant would further add weight to the findings presented here. Practical implications – The paper draws attention to the “lived reality” of doing management, which, we argue often, for women in particular involves the reconciliation of contradictions and conflicting pressures. We draw attention to the lack of “alternative models” of organization and highlight the potential for gender-focus mentoring and management education. Originality/value – The paper is of value in giving voice to a selection of women managers by allowing them to reflect upon and explore their experience of management. The paper also documents the day-to-day reality of women's managerial careers that require the re-enactment and reproduction of stereotypical gender norms.

Rural road accident investigation and prevention in Iran

The objectives are to examine rural road accident data in order to develop a method by which high accident rate locations and accident causes can be identified, and also to develop proposals for improvements at such locations and to identify measures which will improve road safety throughout the country. The problem of road safety in Iran is an important issue, because of the tragic and unnecessary loss of life, and the enormous cost of accidents in the country. The resources available to deal with the problems are limited and must be allocated on priority basis. This study represents an initial effort to identify the extent of the problem in order to take remedial measures. A study was made of all the available road accident data collected by agencies related to road safety in Iran, and the major organisations responsible for road safety development were visited. The Vice Minister of Roads and Transportation selected for this study a 280 Km rural road in South West Iran. Mainly because of the lack of suitable maps and plans of the roads, it was not possible to accurately identify the location of accidents. Accident scene data was subsequently collected by the highway police and personally by the author. The data for the study road was then analysed to identify 'high accident rate' locations, and also to determine, as far as was possible, the reasons for the accidents. The study suggests specific improvements for each of the high accident rate locations examined (eg. the building of dual carriageways with central guard rails to reduce the risk of collision with oncoming vehicles, pedestrian facilities to allow pedestrians to cross dangerous roadsl]. In addition recommendations are made to guide and assist the major organisations responsible for road safety in Iran. These recommendations are: (al for improving accident data collection and storage (bl for subsequent analysis for taking remedial measures with a view to accident prevention

ICT diffusion and foreign direct investment:a comparative study between Asia-Pacific and the Middle Eastern economies

This chapter investigates the impact of inward and outward FDI on ICT diffusion in the Asia-Pacific and Middle East regions for the period 1996-2008. The results indicate that while inward FDI has generally had a positive and significant impact on ICT diffusion in Asia-Pacific economies, its impact on the Middle Eastern countries has been detrimental. In contrast, the results of this study also show that outward FDI has had, in general, the inverse effect, it has been in general positive and significant for the Middle East countries but insignificant for Asia-Pacific economies.

Supply chain management diffusion among firms in the Republic of Ireland

The changing business environment has sharpened the focus on the need for robust approaches to supply chain management (SCM) and the improvement of supply chain capability and performance. This is particularly the case in Ireland, which has the natural disadvantage of a location peripheral to significant markets and sources of raw materials which results in relatively high transport and distribution costs. Therefore, in order to gain insights into current levels of diffusion of SCM, a survey was conducted among 776 firms in the Republic of Ireland. The empirical results suggest that there is a need for more widespread adoption of SCM among Irish firms. This is particularly the case in relation to the four main elements of SCM excellence reported in this paper. The design of supply chain solutions is a highly skilled, knowledge-intensive and complex activity, reflected in a shift from 'box moving' to the design and implementation of customised supply chain solutions. Education and training needs to be addressed by stimulating the development of industry-relevant logistics and SCM resources and skills.

Cellular impermeability and uptake of biocides and antibiotics in Gram-positive bacteria and mycobacteria

Gram-positive bacteria possess a permeable cell wall that usually does not restrict the penetration of antimicrobials. However, resistance due to restricted penetration can occur, as illustrated by vancomycin-intermediate resistant Staphylococcus aureus strains (VISA) which produce a markedly thickened cell wall. Alterations in these strains include increased amounts of nonamidated glutamine residues in the peptidoglycan and it is suggested that the resistance mechanism involves 'affinity trapping' of vancomycin in the thickened cell wall. VISA strains have reduced doubling times, lower sensitivity to lysostaphin and reduced autolytic activity, which may reflect changes in the D-alanyl ester content of the wall and membrane teichoic acids. Mycobacterial cell walls have a high lipid content, which is assumed to act as a major barrier to the penetration of antimicrobial agents. Relatively hydrophobic antibiotics such as rifampicin and fluoroquinolones may be able to cross the cell wall by diffusion through the hydrophobic bilayer composed of long chain length mycolic acids and glycolipids. Hydrophilic antibiotics and nutrients cannot diffuse across this layer and are thought to use porin channels which have been reported in many species of mycobacteria. The occurrence of porins in a lipid bilayer supports the view that the mycobacterial wall has an outer membrane analogous to that of gram-negative bacteria. However, mycobacterial porins are much less abundant than in the gram-negative outer membrane and allow only low rates of uptake for small hydrophilic nutrients and antibiotics.

Discovering knowledge structures in mind maps of mental health risks

This thesis addressed the problem of risk analysis in mental healthcare, with respect to the GRiST project at Aston University. That project provides a risk-screening tool based on the knowledge of 46 experts, captured as mind maps that describe relationships between risks and patterns of behavioural cues. Mind mapping, though, fails to impose control over content, and is not considered to formally represent knowledge. In contrast, this thesis treated GRiSTs mind maps as a rich knowledge base in need of refinement; that process drew on existing techniques for designing databases and knowledge bases. Identifying well-defined mind map concepts, though, was hindered by spelling mistakes, and by ambiguity and lack of coverage in the tools used for researching words. A novel use of the Edit Distance overcame those problems, by assessing similarities between mind map texts, and between spelling mistakes and suggested corrections. That algorithm further identified stems, the shortest text string found in related word-forms. As opposed to existing approaches’ reliance on built-in linguistic knowledge, this thesis devised a novel, more flexible text-based technique. An additional tool, Correspondence Analysis, found patterns in word usage that allowed machines to determine likely intended meanings for ambiguous words. Correspondence Analysis further produced clusters of related concepts, which in turn drove the automatic generation of novel mind maps. Such maps underpinned adjuncts to the mind mapping software used by GRiST; one such new facility generated novel mind maps, to reflect the collected expert knowledge on any specified concept. Mind maps from GRiST are stored as XML, which suggested storing them in an XML database. In fact, the entire approach here is ”XML-centric”, in that all stages rely on XML as far as possible. A XML-based query language allows user to retrieve information from the mind map knowledge base. The approach, it was concluded, will prove valuable to mind mapping in general, and to detecting patterns in any type of digital information.