Redox Potential-Controlled 1,3-Propanediol Production from Glycerol by Lactobacillus panis PM1

The fermentation redox potential was controlled during the production of 1,3-propanediol (PDO) by Lactobacillus panis PM1. Results show that the best redox potential level was at -200 mV at which had the highest PDO production (23.38 g/L) when compared to that controlled at -250 mV, -150 mV, and without control. For the redox potential level under investigation, the mass PDO yield with respect to glycerol was between 0.66 and 0.82. Potassium ferricyanide was chosen as an oxidant to control redox potential level. With the addition of oxidant, the batch fermentation time was noticeably reduced compared to the one without redox potential control. Furthermore, co-substrate utilization of glucose and glycerol was observed when potassium ferricyanide was present. It was postulated that such co-substrate utilization pattern was resulting from the redox imbalance where the activities of acetaldehyde dehydrogenase and alcohol dehydrogenase were retarded by the presence of potassium ferricyanide. To overcome the redox imbalance, the glycerol-reductive pathway was triggered to serve as the electron source to fuel glycolysis pathway along with the PDO formation. The developed redox potential control strategy may benefit other specifically isolated PDO-producing strains and industrial PDO green processing to further enhance their productivity

Impact of environmental inputs on reverse-engineering approach to network structures

Background: Uncovering complex network structures from a biological system is one of the main topic in system biology. The network structures can be inferred by the dynamical Bayesian network or Granger causality, but neither techniques have seriously taken into account the impact of environmental inputs. Results: With considerations of natural rhythmic dynamics of biological data, we propose a system biology approach to reveal the impact of environmental inputs on network structures. We first represent the environmental inputs by a harmonic oscillator and combine them with Granger causality to identify environmental inputs and then uncover the causal network structures. We also generalize it to multiple harmonic oscillators to represent various exogenous influences. This system approach is extensively tested with toy models and successfully applied to a real biological network of microarray data of the flowering genes of the model plant Arabidopsis Thaliana. The aim is to identify those genes that are directly affected by the presence of the sunlight and uncover the interactive network structures associating with flowering metabolism. Conclusion: We demonstrate that environmental inputs are crucial for correctly inferring network structures. Harmonic causal method is proved to be a powerful technique to detect environment inputs and uncover network structures, especially when the biological data exhibit periodic oscillations

Local electrochemical impedance spectroscopy: A review and some recent developments

Local electrochemical impedance spectroscopy (LEIS), which provides a powerful tool for exploration of electrode heterogeneity, has its roots in the development of electrochemical techniques employing scanning of microelectrodes. The historical development of local impedance spectroscopy measurements is reviewed, and guidelines are presented for implementation of LEIS. The factors which control the limiting spatial resolution of the technique are identified. The mathematical foundation for the technique is reviewed, including definitions of interfacial and local Ohmic impedances on both local and global scales. Experimental results for the reduction of ferricyanide show the correspondence between local and global impedances. Simulations for a single Faradaic reaction on a disk electrode embedded in an insulator are used to show that the Ohmic contribution, traditionally considered to be a real value, can have complex character in certain frequency ranges

Quantification of measurement and model effects in monopile foundation scour protection experiments

The present work introduces an analysis of the measurement and model effects that exist in monopile scour protection experiments with repeated small scale tests. The damage erosion is calculated using the three dimensional global damage number S3D and subarea damage number S3D,i. Results show that the standard deviation of the global damage number σ(S3D)=0.257 and is approximately 20% of the mean S3D, and the standard deviation of the subarea damage number σ(S3D,i)=0.42 which can be up to 33% of the mean S3D. The irreproducible maximum wave height, chaotic flow field and non-repeatable armour layer construction are regarded as the main reasons for the occurrence of strong model effects. The measurement effects are limited to σ(S3D)=0.039 and σ(S3D,i)=0.083, which are minor compared to the model effects

ROCSAT-3 Constellation Mission

ROCSAT-3 mission is an international collaboration of Taiwan and the United States to deploy in 2005 a constellation of six microsatellites equipped with GPS occultation receivers in low Earth orbits to collect the GPS signal as passing through the atmosphere. The satellites would generate thousands of sounding data everyday uniformly distributed over the world. The satellites will then downlink the GPS occultation measurements to the ground receiving stations for processing and assimilated into the weather forecast model with minimal delay. The design of ROCSAT-3 constellation takes into consideration factors such as the capability of the available launch vehicle, the mass of the propellant, the locations of ground receiving stations, and the deployment period to achieve the final constellation. The six ROCSAT-3 satellites will be delivered by a single Minotaur launch into the same orbit plane initially. The dispersion of the satellites into the target constellation utilizes the principle that satellites at different altitudes will precess into different orbits over the time. By adjusting the altitude profiles, the six ROCSAT-3 microsatellites would be placed into six orbit planes. Considering ionospheric research, the fuel constraint, and the launcher lifting capability, the mission orbit of 800 km is selected. The inclination angle of 72 degrees is selected as the results of the trade studies involving the location of receiving stations and the precession rate of the orbit. The dominant factor in the selection of the separation angle among orbit planes is the requirement of distribution of the sounding data uniformly. With the constraint of the deployment period, the separation angle is currently defined as 24 degrees. Furthermore, in order to minimize the downlink confliction among satellite passes at the ground stations, a true anomaly separation of 52.5 degrees between satellites in adjacent orbit planes is selected. The mission life of ROCSAT-3 is 2 years. The constellation will be achieved 13 months after launch. An early phase mission plan has also been developed for the deployment period when the satellites are at lower altitudes. At altitude below 500 km, a pitch-biased attitude control can be used to point either the forward or aft occultation antenna at the desired angle for conducting the experiment