Achlya mitochondrial DNA: gene localization and analysis of inverted repeats

Mitochondrial DNA from four strains of the oomycete Achlya has been compared and nine gene loci mapped, including that of the ribosomal protein gene, var1 . Examination of the restriction enzyme site maps showed the presence of four insertions relative to a map common to all four strains. All the insertions were found in close proximity to genic regions. The four strains also cotained the inverted repeat first observed in A. ambisexualis (Hudspeth et al. 1983), allowing an examination by analysis of retained restriction sites of the evolutionary stability of repeated DNA sequences relative to single copy sequences. Although the inverted repeat is significantly more stable than single copy sequences, more detailed analysis indicated that this stability is limited to the portion encoding the ribosomal RNA genes. Thus, the apparent evolutionary stability of the repeat does not appear to derive from the inverted repeat structure per se.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47563/1/438_2004_Article_BF00330510.pd

Process Integration for Food Drying with Air Dehumidified by Zeolites

Zeolites have potential to increase efficiency of mediumtemperature drying in the food industry. This work concerns the comparison between conventional dryers and dryers using air dehumidified by zeolite. Steady-state mass and energy balances have been used and the work concerns drying temperatures ranging from 52 to 70C. Process integration based on pinch analysis has been applied and nine different heat exchanger networks for energy recovery are compared. Results indicated that dryers using air dehumidifier by zeolites are 10–18% more efficient than conventional dryers. Keywords Adsorption; Energy efficiency; Process integration; Zeolite dryin

Energy Efficiency of Multi-Stage Adsorption Drying for Low-Temperature Drying

This work discusses the evaluation of multi-stage adsorption dryers with air dehumidification by zeolite and alumina pillared clay. In a multi-stage dryer, product is dried in succeeding stages while air leaving a stage is fed to the next stage after dehumidification by an adsorbent. Energy efficiency of the drying system is evaluated for low-temperature drying (10–50C) and compared with conventional condenser drying. Results showed that the efficiency of the multi-stage adsorption dryers increases with the number of stages. For low drying temperatures, zeolite is most favorable; for drying temperatures 40–50C, alumina pillared clay needs less cooling and deserves preference. Keywords Adsorption; Alumina pillared clay; Condensation drying; Energy efficiency; Multi-stage drying; Zeolit

Computational Fluid Dynamics for Multistage Adsorption Dryer Design

Two-dimensional Computational Fluid Dynamic(CFD) calculations for multistage zeolite drying are performed for two dryer configurations 1) a continuous moving bed zeolite dryer and 2) a discrete bed zeolite dryer. The calculations concern drying of tarragon (Artemisia dracunculus L.) as a herbal product. The results reveal the profiles of water, vapor and temperature in dryer, adsorber and regenerator in the flow directions. The thermal efficiency ranges between 80-90% and is close to overall model calculations. The performance of continuous moving bed zeolite dryer is the best. Residence time of air, product and zeolite are in accordance to other drying systems. Key words and phrases: Adsobent drying; regeneration; zeolite; terragon; thermal efficiency; model; Moving bed drye

Multistage Zeolite Drying for Energy-Efficient Drying

This work discusses the potential of three multistage zeolitemdrying systems (counter-, co-, and cross-current) with a varying number of stages. The evaluation showed that for 2–4 stages with heat recovery the efficiency of the systems ranges between 80 and 90%. Additionally, by introducing a compressor, the latent heat in the exhaust air from the regenerator is recovered and used to heat the inlet air for an additional drying stage. As a result, for the counter-current drying system and compressor pressure 1.5–2 bar, a maximum energy efficiency of 120% is achieved, which results in halving the energy consumption compared to conventional drying systems. Keywords Drying; Efficiency; Heat recovery; Multistage; Zeolit

Low Temperature Drying With Air Dehumidified by Zeolite for Food Products: Energy Efficiency Aspect Analysis

Developments in low temperature drying of food products are still an interesting issue; especially with respect to the energy efficiency. This research studies the energy efficiency that can be achieved by a dryer using air which is dehumidified by zeolite. Experimental results are fitted to a dynamic model to find important variables for the drying operation. The results show that ambient air temperature as well as the ratio between air flow for drying and air flow for regeneration, affect the energy efficiency significantly. Relative humidity of used air, and shift time have a minor effect on the dryer performance. From the total work, it can be noted that the dryer efficiency operated at 50-60°C achieves 75 percent, which is attractive for drying of food products. Keywords: drying; adsorption; regeneration; energy efficiency; zeolite Citation Information: International Journal of Food Engineering. Volume 7, Issue 6, Pages –, ISSN (Online) 1556-3758, DOI: 10.2202/1556-3758.1930, December 201

Assessment of a Two-Stage Zeolite Dryer for Energy-Efficient Drying

Multistage adsorption drying with zeolite is experimentally evaluated for a single- and a two-stage dryer. For a 1:1 ratio between air flows for drying and regeneration, the energy efficiency for a single-stage system 50–54% and for the two-stage system 63%. Calculations with a calibrated model show that the two-stage system achieves a 4:1 ratio between the air flows an efficiency of 85%, 12% above that of a single-stage system. A sensitivity analysis shows the influence of operational conditions on the energy efficiency. Options to realize multistage adsorption dryer systems and to control such systems as well as the economic aspects are discussed. Keyword Adsorption; Drying; Energy efficiency; Regeneration; Zeolit

Low-cost small scale processing technologies for production applications in various environments-Mass produced factories

The requirements for chemical and food production technologies will change in the future as a result of shorter time to market and increasing market volatility. Especially the rising use of renewable resources will require the implementation of flexible and fast to install small-scale production technologies. The increasing number of necessary apparatuses and their distributed operation, however, will constitute major challenges, both economically and procedurally.The proposed solution to face the economic challenge is modularization and standardization. For food production, dewatering represents a key issue. Thus, biomass processing should first be divided into small-scale water separation steps and then into further large-scale processing steps. As dewatering usually happens thermally and heat exchangers often benefit from the economies of scale, heat supply and energy consumption or heat transfer with little capital investment are further issues. Therefore, temperature levels should be decreased and the use of solar heat increased. For the production of biofuels and chemicals from biomass, process integration and process simplification are proposed to improve the efficacy of production equipment and processes. Choosing raw materials with molecular structures, similar to the desired chemical building block, will lower the need for heat exchange and make small-scale manufacturing of fuels and chemicals possible. © 2011 Elsevier B.V.status: publishe