Experimental determination of solids suspension with angled impeller in a pharmaceutical mixing vessel

Angled-mounted impellers are commonly used in a number of pharmaceutical industry applications, from laboratory reactors to full-scale tanks. In these systems, the impeller is not centrally and vertically mounted, as in most stirred vessels, but it enters the vessel, and is therefore immersed in the fluid, at an angle from the vertical. This arrangement provides some baffling effects that would not otherwise exist if the impeller was centrally mounted. One common requirement for such systems is that they are capable of suspending small solids dispersed in the liquid. Therefore, it is critical to know the value of the minimum agitation speed at which solids become just suspended,Njs. Despite their common use in industry, and especially the pharmaceutical industry, these systems have received little attention in the literature in general and as far as their ability to solid suspension is concerned in particular. Therefore, the focus of this work was to determine under what conditions fine divided solids become suspended in a liquid-filled, unbaffled stirred vessel provided with angled-mounted impellers. A small laboratory vessel with a hemispherical bottom was used here. Different types of axial and radial impellers mounted at different angles (0°, 5° and 10°) at different off-bottom impeller clearances were tested. The value ofNjs was experimentally obtained by visually inspecting the tank bottom and determining the impeller agitation speed at which the solids were observed to rest on the tank bottom for no more than 1-2 seconds before being swept away. In addition, a novel observer-independent criterion was developed, relying on the experimental determination of the fraction of solids remaining on the vessel bottom at increasing agitation speeds. This approach results in values ofNjs that are close agreement with the visually determined Njs values. This approach was used to determineNjs for different impellers under a number of operating conditions. In general, mounting the impeller at an angle resulted inNjsvalues lower than those obtained with centrally mounted impellers. In addition, it was found that lower impeller clearances resulted in lowerNjs values, although the minimum for Njs was obtained when the impeller clearance was about 20% of the vessel diameter. The results obtained in this work are expected to be applicable to a number of systems currently used in the pharmaceutical industry

Examining medical doctors’ internship training experience and labour market transition in Kenya

Kenya has a severe shortage of doctors. Despite medical schools increasing the numbers of medical officers (MO) in training, less than half of newly qualified/registered MOs were absorbed by the public sector between 2015 and 2018. It seems timely to understand the labour market for this profession in system terms and in personal terms for doctors, especially during their labour market entry. I used a multiple-method approach including literature reviews, quantitative survey and qualitative interviews to examine doctors’ internship training experiences and labour market transition in Kenya. I found that the resources available in hospitals overall was often inadequate to support medical internship training in Kenya, especially for Level 4/district or smaller hospitals. Over half reported that their hospitals did not have enough consultants, physical resources and supplies of diagnostics, equipment and medications required for their study and work. Over half of the interns experienced burnout and anxiety, some did not have good supervision at all times and had to perform inappropriate tasks, especially in smaller hospitals. Such poor internship experiences influenced MOs’ career intentions. Some preferred to leave the public sector, however the majority still preferred to work in the public sector or continue with specialist training immediately after internship. Nonetheless, as decentralisation in 2013 led to county governments being responsible for local workforce recruitment, they are not absorbing these MOs into the public sector. This is for reasons including limited health system financing, a willingness to rely on interns to provide hospital care, and preference for recruiting other cheaper health worker cadres. These findings suggest that Kenya needs to take a strategic approach to match the demand and supply of physicians, especially at labour market entry (i.e. internship) as well as improve the internship training resources and capacity. Poor planning and management not only wastes resources and undermines healthcare delivery, but can also be detrimental to individual physicians

Investigating pericyte progenitor cells in glioma angiogenesis and postnatal brain development

The current study established that a transgenic mouse model, Nes-CreERT2 Tdtomato, is of use to trace the fate of nestin-expressing cells in glioma progression and postnatal brain development. Through a series of cell type identification tests, using immunofluorescence labelling and confocal microscopy, it was shown that these nestin-positive cells generate new pericytes, but initially do not have a pericyte identity, this is corroborated by the following findings: (1) In the Nes-CreERT2 Tdtomato mouse model, the number of traced cells (RFP positive cells) increased during the intracranial tumor growth. At an early time point (7 days) few of the RFP positive cells co-localized with pericyte markers while at a later time point (21 days) most of the RFP positive cells co-localized with pericyte markers, which indicated that the new pericytes in glioma derived from the pericyte progenitor cells (defined as RFP positive and pericyte marker negative cells) in the Nes-CreERT2 Tdtomato mouse model; (2) In the JnesCreERT2 Tdtomato mouse model, the traced cells were found to express astrocyte-markers like GFAP but not pericyte markers, which indicated that the traced cells in the JnesCreERT2 Tdtomato mouse model were originally neural stem cells rather than pericyte progenitor cells. Hence, only the Nes-CreERT2 Tdtomato mouse model is useful to study pericyte development in the brain. (3) The cells traced with the NesCreERT2-tdTomato mouse model over a postnatal period develop into pericytes in the brain, which indicates that the NesCreERT2-tdTomato strain is a useful model to trace the pericyte lineage both in pathological neoangiogenesis during glioma growth and in physiological postnatal angiogenesis. (4) In this study RFP-expressing pericyte marker positive cells were detected in the postnatal mouse retina, indicating that RFP-traced pericytes play an important role in both pathological angiogenesis and physiological vascular development of retina

Reverse engineering of short-chain fatty acid tolerance and production in Escherichia coli

Product toxicity is a common problem in microbial production of biorenewable fuels and chemicals. Historically, the field of metabolic engineering has relied on enrichment of expression libraries and strain evolution for improving tolerance. Reverse engineering of these strains can aid in the identification and development of rational design strategies for strain improvement, according to Orgel’s Second Rule that “evolution is cleverer than you are”. Here, we investigated the evolved strain with increased short-chain fatty acid tolerance and 5-fold higher fatty acid titer relative to its parent strain to discover and understand the mechanisms of the phenotypic changes. Four mutations were identified in the evolved strains, as well as the chronological order of mutations during adaptive evolution. Then we studied each mutation and their synergistic interaction by characterizing the reconstructed strains, which had single mutation, double mutation or triple mutations replaced into the genome of the parent strain. The waaG mutation contributed to increased C8 tolerance, fatty acid titer, and membrane integrity. The increased fatty acid titer was mainly affected by the mutant rpoC gene. The decreased membrane fluidity and increased cell surface hydrophobicity of evolved strain were caused by the synergistic interaction of waaG, rpoC, and basR mutations. We also noticed each mutation was able to alter the membrane lipid composition differently. The association between mutations and phenotypic changes we identified could be used as rational engineering strategies for improving tolerance and production of microbial biocatalyst. However, the rpoC and basR encode transcriptional regulators, and we were not able to fully understand the mechanisms of these two mutations by only genome-level reverse engineering. Thus, we further investigated these two mutations by transcriptome analysis. Compared evolved strain LAR1 to parent strain ML115 during fatty acid producing, twenty-nine genes made statistically significant changes in transcript abundance, which could be influenced by rpoC mutation. Also, nine genes were identified had differential transcript abundance, which could be impacted by the basR mutation. Characterization of these interesting genes is in progress to discover the mechanisms of increased short-chain fatty acids tolerance and production of evolved strain LAR1. In order to deepen our understanding the association between fatty acid production and cell membrane properties, we characterized a small group of environmental E. coli isolates with significantly higher short-chain fatty acids production in minimal medium relative to lab strain MG1655. Consistent with previous studies, decreased membrane fluidity was associated with increased fatty acid production. The C16:1/C16:0 ratio (mol/mol) was suggested to be one of the important metrics, when rationally engineering membrane lipid composition for improving short-chain fatty acids production in E. coli. We also discovered the direct association between cell surface hydrophobicity and short-chain-fatty acids titer. In short, the findings of our work could provide new insights into the mechanisms of short-chain fatty acid tolerance and production, and rational engineering strategies for improving performance of biocatalyst

Teachers' Beliefs in Successful Education in China and Germany

Education acts as the powerful influence not only on a nation’s comprehensive strength, but also on the individual’s whole life, so the topic on successful education has important research value and significance for the reality. Within the process of education teachers undeniably play a main role, whose teaching minds and behaviors crucially affect the outcomes of education and decide the success/failure of educational reforms. Former research has found that teachers’ beliefs, as one of the most valuable psychological constructs, are strong guidance and predictors of their teaching behaviors, and some beliefs which are important for teachers are believed to remain stable and unchanged regardless of situations, where teachers try to hold on their beliefs and put into practice. Therefore, in the past years teachers’ beliefs have been a priority among the research topics in the educational area, and a large quantity of articles have focused on the discussion about teachers’ beliefs in different aspects. However, there has been no research connecting teachers’ beliefs to successful education in a cross-cultural comparative perspective between China and Germany. So this study could be expected to fill in this blank and open a fresh but practical angle to look into the education and school systems in both countries through the eyes of teachers, and hopefully it could provide an effective and helpful reference for teacher education and educational reforms in the future

Critical Evaluations Of Modis And Misr Satellite Aerosol Products For Aerosol Modeling Applications

The study of uncertainties in satellite aerosol products is essential to aerosol data assimilation and modeling efforts. In this study, with the assistance of ground- based observations, uncertainties in Moderate Resolution Imaging Spectroradiometer (MODIS) collection 5 Deep Blue (DB), Multi-Angle Imaging Spectroradiometer (MISR) version 22 aerosol products, and the newly released collection 6 Dark Target over-ocean and DB products were evaluated. For each product, systematic biases were analyzed against observing conditions. Empirical correction procedures and data filtering steps were generated to develop noise and bias reduced DA-quality aerosol products for modeling related applications. Special attention was also directed at the potential low bias in satellite aerosol optical depth (AOD) climatology due to misclassification of aerosols as clouds over Asia. A heavy aerosol identifying system (HAIS) was developed through the combined use of the Ozone Monitoring Instrument (OMI) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) products for detecting heavy smoke aerosol plumes. Upon extensive evaluation, HAIS was applied to one year of collocated OMI, CALIOP, and MODIS data to study the misclassifications related low bias. This study suggests that the misclassification of heavy smoke aerosol plumes by MODIS is rather infrequent and thus introduces an insignificant low bias to its AOD climatology. Still, this study confirms that misclassification happens in both active- and passive- based satellite aerosol products and needs to be studied for forecasting these events

Re-order the order of thing

Humanocentrism positions humans as the measure of all things; what we know as the ‘real’ or ‘true’ is perceived through this limited perspective. As a designer, I challenge the hierarchy, actively moving away from the notion that inanimate objects are subjugated matter. In this body of work, I turn to actions of world-building to create immersive experiences where ‘objects’ become ‘subjects.’ They are rescaled and re-centered — called into prominence to become protagonists on the cultural and environmental stage. Through generating, collaging, and juxtaposing recycled facts, imagery and organic materials using digital filters, I insert absurdity as a breakpoint to equalize the imbalance. Performing in both real and digital spaces, what is often rendered passive and mundane becomes extraordinary, even kindred in the vast arena of human preoccupation

Towards an understanding of consumer´s behavior of buying secondhand products on social media

Due to the research scarcity in consumers’ secondhand shopping behaviors and consumer-to-consumer (C2C) businesses on social media platforms, this thesis decided to concentrate on both secondhand products and social media. The aim of this thesis is to explore the consumers’ behaviors of buying secondhand products on social media – a new channel of doing C2C businesses. To achieve the research aim, I conducted a combined method consisting of 106 questionnaires and ten semi-structured interviews to collect empirical data in this study. After an analysis of empirical data including both qualitative and quantitative data, three main findings were concluded. (1) The thesis firstly explored the social media as an open online marketplace for doing secondhand transactions. Consumers exchange secondhand products on social media in an ‘informal’ way. (2) The finding highlighted that, when consumers buy secondhand products on social media platforms, they are involved either in a ‘passive shopping’ process or an ‘active shopping’ process, and it is highly possible for them to experience hedonic factors (e.g. excitement, fun) due to the occasional and unexpected shopping results. This finding provides two new angels (passive shopping and active shopping) for researchers to analyze consumer behaviors in the future. (3) By extending the study of secondhand shopping motivation from Guiot & Roux (2009, 2010) in an online trading environment, the findings showed that utilitarian aspects of shopping such as price, convenience, product information, and trust mainly drive consumers’ behavior of buying secondhand products on social media. Environmental consideration and recreational motivation are less important than those utilitarian aspects