Biomedical subjects

M Ronen

Publications and source records attributed to M Ronen.

At least 19 recordsLinked to original sources

PubMed2002

Optimization of feeding profile for a fed-batch bioreactor by an evolutionary algorithm.

The optimal feeding profile of a fed batch process was designed by means of an evolutionary algorithm. The algorithm chromosomes include the real-valued parameters of a profile function, defined by previous knowledge. Each chromosome is composed of the parameters that define the feeding profile: the feed rates, the singular arc parameters and the switching times between the profile states. The feed profile design was tested on a fed-batch process simulation. The accepted profiles were smooth and similar to those derived analytically in other studies. Two selection functions, roulette wheel and geometric ranking, were compared. In order to overcome the problem of model mismatches, a novel optimization scheme was carried out. During its operation the process was sampled, the model was updated and the optimization procedure was applied. The on-line optimization showed improvement in the objective function for relatively low sample times. Choosing the sampling frequencies depends on the process dynamics and the time required for the measurements and optimization. Further study on experiments of fed-batch process demonstrated the use of complex, non-differentiable model and produced improved process performances using the optimal feeding profile.

Algorithms↗

PubMed2002

Monitoring and control of pullulan production using vision sensor.

The production of the polysaccharide pullulan by the yeast-like fungi, Aureobasidium pullulans, is accompained by cellular morphogenetic changes. High productivity and yield of the process have been found to correlate with high concentration of yeast-like cells in the culture. The morphogenetic changes of A. pullulans cells depend on the culture conditions, e.g., dissolved oxygen, shear rate and medium composition. In order to improve the productivity of the process, a novel control law was formulated. A feeding strategy dependent on the culture cellular composition was designed and aimed to keep the yeast-like cell concentration high. The culture morphogenetic composition during the process was monitored by a recently developed vision sensor. Feeding was actuated when the yeast-like cell concentration decreased below a threshold. The proposed control strategy improved pullulan production by increasing both productivity and yield of the cells by 67% and 80%, correspondingly. The results point to the advantage and the potential of using the monitoring and control system and algorithm to increase productivity and yield in cellular bioprocesses.

Ascomycota↗

PubMed2002

Hybrid model building methodology using unsupervised fuzzy clustering and supervised neural networks.

This paper suggests a model building methodology for dealing with new processes. The methodology, called Hybrid Fuzzy Neural Networks (HFNN), combines unsupervised fuzzy clustering and supervised neural networks in order to create simple and flexible models. Fuzzy clustering was used to define relevant domains on the input space. Then, sets of multilayer perceptrons (MLP) were trained (one for each domain) to map input-output relations, creating, in the process, a set of specified sub-models. The estimated output of the model was obtained by fusing the different sub-model outputs weighted by their predicted possibilities. On-line reinforcement learning enabled improvement of the model. The determination of the optimal number of clusters is fundamental to the success of the HFNN approach. The effectiveness of several validity measures was compared to the generalization capability of the model and information criteria. The validity measures were tested with fermentation simulations and real fermentations of a yeast-like fungus, Aureobasidium pullulans. The results outline the criteria limitations. The learning capability of the HFNN was tested with the fermentation data. The results underline the advantages of HFNN over a single neural network.

Biotechnology↗

PubMed2001

Ordering genes in a flagella pathway by analysis of expression kinetics from living bacteria.

The recent advances in large-scale monitoring of gene expression raise the challenge of mapping systems on the basis of kinetic expression data in living cells. To address this, we measured promoter activity in the flagellar system of Escherichia coli at high accuracy and temporal resolution by means of reporter plasmids. The genes in the pathway were ordered by analysis algorithms without dependence on mutant strains. The observed temporal program of transcription was much more detailed than was previously thought and was associated with multiple steps of flagella assembly.

Algorithms↗

PubMed2001

Garlic burns.

A patient with a second-degree burn of the forehead, induced by topical application of crushed garlic is reported. The literature on garlic burns is reviewed.

Asthma↗

PubMed1998

Light/dark cycles in the growth of the red microalga porphyridium sp

The effect of light/dark cycles on the growth of the red microalga Porphyridium sp. was studied in a tubular loop bioreactor with light/dark cycles of different frequencies and in two 35-L reactors: a bubble column reactor and an air-lift reactor. Photon flux densities were in the range of 50 to 300 μE m-2 s-1, and flow rates were 1 to 10 L min-1. Under conditions of low illumination and high flow rates, similar results were obtained for the bubble column and air-lift reactors. However, higher productivities-in terms of biomass and polysaccharide-were recorded in the air-lift reactor under high light intensity and low gas flow rates. The interactions of both photosynthesis and photoinhibition with the fluid dynamics in the bioreactors was taken as the main element that allowed us to interpret the differences in performance of the bubble column and the air-lift reactor. It is suggested that the cyclic distribution of dark periods in the air-lift reactor facilitates better recovery from the photoinhibition damage suffered by the cells. Copyright 1998 John Wiley & Sons, Inc.

Journal Article↗

PubMed1993

Pseudotumor cerebri induced by vitamin A combined with minocycline.

A 16-year-old girl complained about a headache of one-month's duration, accompanied by vertical diplopia that had appeared ten days earlier. The girl reported receiving vitamin A and minocycline to treat acne vulgaris for the previous six weeks. An examination revealed bilateral optic disc edema. Normal computed tomographic and magnetic resonance imaging examinations enabled a diagnosis of pseudotumor cerebri to be made. Soon after discontinuation of those medications, the headaches and diplopia diminished. We suggest a periodic ophthalmologic examination during systemic therapy with vitamin A combined with minocycline to detect the early occurrence of pseudotumor cerebri.

Acne Vulgaris↗

PubMed1990

[Sea-urchin injuries].

Sea urchins (Echinoidea) are found along the Mediterranean and especially the Red Sea coasts of Israel. The most important species are Diadema setosum on the Red Sea coast, and Paracentrus lividus on the Mediterranean. When stepped on, the brittle spines penetrate and the venom they carry causes further damage. Thus the injuries are mainly mechanical, but may be complicated by a foreign body reaction to the bits of spine, to small detached segments of their covering epithelium, and damage by the epithelial venom. Severe pain, edema, local sensory loss and sometimes suppuration ensue.

Animals↗

PubMed1986