865 research outputs found
Heterogeneous Extractive Batch Distillation of Chloroform - Methanol – Water : Feasibility and Experiments
No full textA novel heterogeneous extractive distillation process is considered for separating the azeotropic mixture chloroform – methanol in a batch rectifying column, including for the first time an experimental validation of the process. Heterogeneous heavy entrainer water is selected inducing an unstable ternary heteroazeotrope and a saddle binary heteroazeotrope with chloroform (ternary diagram class 2.1-2b). Unlike to well-known heterogeneous azeotropic distillation process and thanks to continuous water feeding at the column top, the saddle binary heteroazeotrope chloroform – water is obtained at the column top, condensed and further split into the liquid – liquid decanter where the chloroform-rich phase is drawn as distillate. First, feasibility analysis is carried out by using a simplified differential model in the extractive section for determining the proper range of the entrainer flowrate and the reflux ratio. The operating conditions and reflux policy are validated by rigorous simulation with ProSim Batch Column® where technical features of a bench scale distillation column have been described. Six reproducible experiments are run in the bench scale column matching the simulated operating conditions with two sequentially increasing reflux ratio values. Simulation and experiments agree well. With an average molar purity higher than 99%, more than 85% of recovery yield was obtained for chloroform and methanol
An empirical analysis of entropy search in batch bayesian optimisation: A comprehensive study of function shape, batch size, noise level, and dimensionality impact on information-theoretic methods
No full textBayesian optimisation is a rapidly growing area of research that aims to identify the optimum of the black-box function, as it strategically directs the optimisation process towards promising regions. This paper provides an overview of the theoretical background used by the Entropy Search algorithms under study, mainly Predictive Entropy Search, Max-Value Entropy Search, and Joint Entropy Search. Furthermore, we empirically analyse the performance and sensitivity of the algorithms in different environment settings. In particular, we discuss the impact of function shape, batch size, noise level, and the number of input dimensions on the final simple regret metric. The results show the weak spots of the information-theoretic methods. However, the algorithms perform better for batch optimisation, demonstrating the advantage when considering the information on the maximum function value.https://github.com/ahautelman/entropy-seach-batch-global-optimiation-performanceCSE3000 Research ProjectComputer Science and Engineerin
Design of a Period Batch Control planning system for cellular manufacturing
No full textThesis 1 Introduction 2 Relationships between cells 3 Period Batch Control 4 Design factors for basic unicycle PBC systems 5 Models and methods for determining a period length P 6 Modelling the trade-off between N and P 7 Determining a configuration of the PBC system 8 Co- ordination between cells and PBC system design 9 Conclusions and further research Appendices: Short case descriptionsProduction planning Operations management
Batch correction of taxonomic data of the human gut microbiome for generalization of case-control classification
No full textNext-Generation Sequencing (NGS) has made it possible to perform metagenomic sequencing of environmental microbiome samples. Colorectal cancer (CRC) benefits from early detection, and many studies find correlations between disease presence and abundance of species in samples of the microbiome. However, these studies are hard to reproduce and even harder to build diagnostic tools from, and one of the major factors for this is the inherent bias in the datasets that were collected, the so-called batch effect. To investigate the extent to which batch effect impacts the generalization of binary classifiers, we performed a benchmark of eleven batch correctors: four existing tools, three transformations and three encoders, assessing the subsequent performance of seven supervised binary classifiers using a leave-one-dataset-out (LODO) validation method. In addition, batch effect was measured through both visual (tSNE) and numeric (linear models) methods before and after applying each of the correctors, and the performance at different dataset counts was measured. Batch effect was shown to be present in the shotgun metagenomic data, being reduced by some correction tools while being strengthened by others. Evaluations using AUROC showed that combining datasets without correction improved generalization, even at an equivalent number of samples. When combining batch correctors and different classifiers, the performance over the baseline did not improve significantly. Contrary to its popularity as batch corrector, the performance significantly worsened when using ComBat before training each of the binary classifiers.Thus, even though batch correctors reduce batch effect within our taxonomic count data, they do not significantly improve classification performance when generalizing to separate datasets. We can thus advise against focusing on choosing a batch corrector when building tools for predicting diagnosis of CRC and instead aiming to improve the pool of datasets to learn from.The code for reproducing the results and figures in this work have been made available at https://github.com/AbeelLab/ngs-batch-evaluation Computer Scienc
Preventing Chronic Disease (PCD)
No full textIntroductionNeighborhood characteristics such as racial segregation may be associated with hypertension, but studies have not examined these relationships using spatial models appropriate for geographically patterned health outcomes. The objectives of our study were to 1) evaluate the geographic heterogeneity of hypertension; 2) describe whether and how patient-level risk factors and racial isolation relate to geographic heterogeneity in hypertension; and 3) examine cross-sectional associations of hypertension with racial isolation.MethodsWe obtained electronic health records from the Duke Medicine Enterprise Data Warehouse for 2007\u20132011. We linked patient data with data on racial isolation determined by census block of residence. We constructed a local spatial index of racial isolation for non-Hispanic black patients; the index is scaled from 0 to 1, with 1 indicating complete isolation. We used aspatial and spatial Bayesian models to assess spatial variation in hypertension and estimate associations with racial isolation.ResultsRacial isolation ranged from 0 (no isolation) to 1 (completely isolated). A 0.20-unit increase in racial isolation was associated with 1.06 (95% credible interval, 1.03\u20131.10) and 1.11 (95% credible interval, 1.07\u20131.16) increased odds of hypertension among non-Hispanic black and non-Hispanic white patients, respectively. Across Durham, census block-level odds of hypertension ranged from 0.62 to 1.88 among non-Hispanic black patients and from 0.32 to 2.41 among non-Hispanic white patients. Compared with spatial models that included patient age and sex, residual heterogeneity in spatial models that included age, sex, and block-level racial isolation was 33% lower for non-Hispanic black patients and 20% lower for non-Hispanic white patients.ConclusionRacial isolation of non-Hispanic black patients was associated with increased odds of hypertension among both non-Hispanic black and non-Hispanic white patients. Further research is needed to identify latent spatially patterned factors contributing to hypertension
Low-Power CMOS Smart Temperature Sensor With a Batch-Calibrated Inaccuracy of ±0.25 °C (±3σ) from −70 °C to 130 °C
No full textIn this paper, a low-power CMOS smart temperature sensor is presented. The temperature information extracted using substrate PNP transistors is digitized with a resolution of 0.03 °C using a precision switched-capacitor (SC) incremental A/D converter. After batch calibration, an inaccuracy of ±0.25 °C (±3σ ) from −70 °C to 130 °C is obtained. This represents a two-fold improvement compared to the state-ofthe-art. After individual calibration at room temperature, aninaccuracy better than ±0.1 °C over the military temperature range is obtained, which is in-line with the state-of-the-art. This performance is achieved at a power consumption of 65 μW during a measurement time of 100 ms, by optimizing the power/inaccuracy tradeoffs, and by employing a clock frequencyproportional to absolute temperature. The latter ensures accurate settling of the SC input stage at low temperatures, and reduces the effects of leakage currents at high temperatures.Electronic Instrumentatio
A BJT-Based Temperature-to-Digital Converter with ±60 mK (3 σ) Inaccuracy From-55 °c to +125 °c in 0.16-μm CMOS
No full textThis paper presents a precision CMOS temperature-to-digital converter (TDC), which senses the temperature-dependent base-emitter voltage of substrate PNPs. Measurements on 20 samples from one batch show that it achieves an inaccuracy of ±60 mK (3σ) from-55 °C to +125 °C, after a single room-temperature trim. This state-of-the-art result is mainly due to the extensive use of dynamic error cancellation techniques to generate the PNP's collector currents, thus minimizing the spread in their base-emitter voltages, together with a digital PTAT trim to correct for the spread in the PNP's saturation currents. The effect of process variation on the TDC's inaccuracy was investigated by measuring 80 samples from three different batches. Using the same calibration parameters, they exhibit a maximum untrimmed inaccuracy of ±2 °C (3σ) from-55 °C to +125 °C. This drops to ±100 mK (3σ) after a single point trim. The proposed TDC thus reduces calibration costs by obviating the need for batch-specific calibration parameters, which would otherwise require the multipoint calibration of several samples. The effect of the PNP's current gain β was also investigated with the help of a novel β-detection circuit. Implemented in 0.16-μm CMOS, the TDC occupies 0.16 mm2 and draws 4.6 μA from 1.5 to 2 V supply voltages. It achieves a resolution Figure of Merit of 7.8 pJ°C2, and a state-of-the-art supply sensitivity of 0.01 °C/V.Accepted Author ManuscriptElectronic InstrumentationMicroelectronic
Feedback optimization of fed-batch baker\u27s yeast fermentation
No full textA feedback optimization scheme for a fed-batch fermentation was developed. Saccharomyces cerevisiae, commonly known as baker\u27s yeast, was chosen as a model system. As the first part of the proposed feedback optimization scheme, open-loop optimization studies have been carried out for the fed-batch baker\u27s yeast culture. The simulation results demonstrated that the proposed feedback optimization scheme could handle the situations in which there are uncertainties in initial conditions and system parameters. The feedback optimization scheme could even overcome the changes in substrate feed concentration. A fully computerized fed-batch fermentation system has been built. It consisted of a 15 L fermentor equipped with a local controller; to which a microcomputer, on-line cell density measurement devices, and a feeding system were interfaced. A fermentor offgas line was connected to a mass spectrometer. The mass spectrometer was also interfaced to the microcomputer for control and data acquisition. The feedback optimization scheme has been implemented in low and high cell density fed-batch baker\u27s yeast fermentations. The experimental results demonstrated the superiority of closed-loop implementation to the open-loop implementation for both low and high cell density runs. The performance indices in the closed-loop implementations were typically 10-20% greater than those in open-loop implementations. In the high cell density fermentations, experiments were carried out with an enriched oxygen source to overcome oxygen limitation, while measuring cell density on-line using a fiber optic device. A computational algorithm has been developed using the extended Kalman filter to estimate state variables and model parameters simultaneously. This algorithm was applied to a batch baker\u27s yeast culture; based upon measurements of oxygen uptake rate, carbon dioxide evolution rate, and cell mass concentration. The Kalman filter yielded good estimates of the state variables, as well as kinetic model parameters, during exponential growth phases. A number of experimental studies have been carried out to investigate unequal uptake of -glucose and -glucose by yeast. (Abstract shortened with permission of author.
Optimisation of the production of cathepsin L1 from a recombinant saccharomyces cerevisiae
No full textCathepsin L1 is a cysteine protease that has been previously isolated and functionally expressed in Saccharomyces cerevisiae. It has the potential to be employed as a vaccine for liver-fluke disease in cattle and other ruminants. Production of this recombinant enzyme, which is secreted into the media from recombinant yeast, was studied initially in shake flask cultures and subsequently in 5L and 15L fermenters.
In early studies, low productivity and especially variations in Cathepsin L1 production was a significant problem. A standard operating protocol (SOP) has been designed to consistently supply an optimum inoculum for large-scale fermentations. This SOP which involved 'blending' colonies for inoculum cultures in conjunction with sub-culturing starter flasks for two successive cycles of 48 hours, proved to be the most successful for consistently high levels of enzyme production during the ensuing fermentation.
The pH and temperature optima are pH 6.5 and 30°C respectively for culturing the recombinant yeast to produce both both high biomass levels and high enzyme activity. Addition of casamino acids to the selective media or replacing it with complex YEPD resulted in poor plasmid stability and low Cathepsin L1 production. By supplementing the selective media with extra yeast nitrogen base, using a glucose concentration of 20g/L, enzyme activity increased by 3-4 fold and much higher levels of plasmid stability than observed in non-selective media were sustained. Enzyme activity of 0.74 units/mL were obtained in supplemented media compared to 0.19 units/mL in selective media.
Investigations were performed on the constitutive behaviour of the ADH1 promoter, which controls the expression of Cathepsin L1 in this recombinant yeast strain. It revealed that enzyme production is repressed at high concentrations of glucose but gradually increases as glucose is utilised. Cathepsin L1 is still expressed during the ethanol consumption phase, albeit at a slower rate than during the latter stages of glucose consumption
Kinetic models for heterotrophic growth of Chlamydomonas reinhardtii in batch and fed-batch cultures
No full textHeterotrophic growth of Chlamydomonas reinhardtii using acetate as a carbon source and nitrate, ammonium and urea as nitrogen sources in batch cultures was investigated. These nitrogen sources supported good growth of C. reinhardtii, the resulting cell concentrations for nitrate, ammonium chloride and urea were 0.48, 0.44 and 0.61 g l, respectively. The specific growth rate μ(x) of the urea culture was the highest (0.071 h), followed by that of the nitrate culture (0.062 h), and the specific growth rate μ(x) of the ammonium culture was the lowest (0.058 h). Urea is therefore considered to be the best nitrogen source for the growth of the alga. Based on these results fed-batch cultures were performed to reach the maximum cell concentration of 1.1482 g l, about 1.9-fold that obtained in batch culture. Finally, a group of kinetic models for describing cell growth, pH variation and acetate consumption were proposed and a satisfactory fit between the experimental results and predicted values was demonstrated. The effects of dilution rate and acetate feed concentration on cell growth were analyzed with those with these models
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