DNA replication in the fission yeast: robustness in the face of uncertainty

DNA replication, the process of duplication of a cell's genetic content, must be carried out with great precision every time the cell divides, so that genetic information is preserved. Control mechanisms must ensure that every base of the genome is replicated within the allocated time (S-phase) and only once per cell cycle, thereby safeguarding genomic integrity. In eukaryotes, replication starts from many points along the chromosome, termed origins of replication, and then proceeds continuously bidirectionally until an opposing moving fork is encountered. In contrast to bacteria, where a specific site on the genome serves as an origin in every cell division, in most eukaryotes origin selection appears highly stochastic: many potential origins exist, of which only a subset is selected to fire in any given cell, giving rise to an apparently random distribution of initiation events across the genome. Origin states change throughout the cell cycle, through the ordered formation and modification of origin-associated multisubunit protein complexes. State transitions are governed by fluctuations of cyclin-dependent kinase (CDK) activity and guards in these transitions ensure system memory. We present here DNA replication dynamics, emphasizing recent data from the fission yeast Schizosaccharomyces pombe, and discuss how robustness may be ensured in spite of (or even assisted by) system randomness.     

Current strategies for dairy waste management: a review

Industrial waste management is nowadays one of the main issues for ensuring a sustainable environment. Dairy waste management in particular, is very crucial in view of the high organic matter and high nutrient levels contained in dairy effluents. Dairy waste can be effectively treated either with aerobic or anaerobic processes. The main advantages of the former consist of low yield, high kinetics, pathogen free product, and high temperature operation whereas the latter is a simple, low budget and conservative technology. Occasionally, pre-treatment strategies (i.e. wetlands) are required in order to improve the efficiency of treatment methodology. Wetlands are a promising technology applied in order to remove the greater part of nutrients and minerals contained in milk based products.     

Use of molecular tools to characterize Lactobacillus spp. isolated from Greek traditional fermented sausages

In this study, our purpose was to molecular characterize Lactobacillus strains isolated from naturally fermented sausages, produced in three different processing plants in continental Greece, in order to investigate the differences of strains coming from different producing areas. Three-hundred and thirty eight strains were isolated throughout the fermentation periods on MRS. They were identified by species-specific PCR and sequencing of partial 16S rRNA gene. The results obtained highlighted that the main populations involved in the fermentations studied belonged to the species Lactobacillus sakei, Lactobacillus plantarum and Lactobacillus curvatus. However, for each of the fermentations, the percentage of isolation for the three main species was different. Molecular characterization of these strains was performed by RAPD-PCR with primer M13 and cluster analysis was applied to define relations and degrees of similarities between strains. This analysis led to the understanding that some strains were plant-specific, whereas others shared a degree of homology independently of the provenience. This evidence is highlighting the capability of the strains to adapt to specific production condition, becoming the main responsible for the transformations, thereby influencing the final characteristics of the sausages.     

Investigating the concept of meat quality from the consumers' perspective: The case of Greece

Recent unfortunate food incidents increased consumers' concern about food and especially meat quality. The perception that meat is a hazardous commodity to consume resulted in a stabilization of the, so far increasing, meat consumption in Greece, as well as in the EU. The present survey aims to identify the general trends of meat consumption in Greece, define through factor analysis the way consumers perceive the concept of meat quality and explore by means of cluster analysis the existence of specific consumer types in relation to meat quality perceptions, with clear-cut and statistically solid socio-demographic and behavioural profile .The frequency of meat purchasing and consumption is particularly high, while meat is present in the everyday plate of Greeks in almost any expression of their family and social life. Meat preference is mainly evaluated on the basis of pleasure derived from taste, which has to be evaluated according to visual quality cues (e.g., colour, leanness, etc.). Different consumer types with clear-cut profile are found to evaluate meat quality differently, based on different quality dimensions, such as visual quality, labels and brand name, nutritional value and microbial or chemical safety.     

Transformation of radially traveling cylindrical waves between two skew cylindrical coordinate systems

The transformation of radially traveling cylindrical waves between two cylindrical coordinate systems with skew (nonparallel) axes is derived for the first time to our knowledge. The analytical procedure is based on the complex integral representation of the Hankel function and appropriate contour deformation and change of variables to obtain a final Fourier transform expression of the cylindrical wave in the new system. Scalar and vector waves are considered. This new result is a powerful tool for the rigorous analysis of scattering and coupling in nonparallel optical fiber configurations.     

The analytic solution for hydrodynamic diffraction by submerged prolate spheroids in infinite water depth

This study investigates the linear hydrodynamic scattering problem by stationary prolate spheroidal bodies and aims at providing an analytic solution for the associated boundary value problem. It extends the work of the present author on the hydrodynamics of oblate spheroidal bodies following the same procedure. The structural model under consideration is a spheroid with its polar axis greater than its equatorial diameter, subjected to the action of monochromatic incident waves. The polar axis is assumed to be perpendicular to the free surface that leads to the axisymmetric case concept. The analytic solution is sought using the method of multipole expansions constructed by employing Thorne’s formulas (Multipole expansions in the theory of surface waves. Proc Cam Philos Soc 49:707–716, 1953) that describe the velocity potential at singular points within a fluid domain with free upper surface and infinite water depth. The final stage of the solution process is the application of the zero velocity condition on the wetted surface of the spheroid. Inevitably this task requires the transformation of the involved velocity potentials, originally expressed with respect to spherical and polar coordinates, into prolate spheroidal coordinates. To this end, the appropriate addition theorems are derived, which recast Thorne’s expressions into infinite series of associated Legendre functions.     

Cycle time reduction by improved MRP-based production planning

The important practical problem of planning the production of large assemblies employing an MRP-based system is considered. The objective is to produce products on-time, with minimal cycle time and low work-in-process costs. The approach is based on the determination of accurate lead-time estimates and on the introduction and use of lead-time offsets in the solution methodology. An effective Lead-time Evaluation and Scheduling Algorithm (LETSA) is employed that can perform detailed backward scheduling of operations belonging to a large assembly on a given facility with an objective of minimizing the cycle time. A scaling procedure is used to account for capacity sharing effects by multiple products in a common facility. These scaled lead-time estimates are then employed by an MRP-based system to release work-orders on the shop-floor. The effectiveness of these lead-times and lead-time offsets are evaluated by simulating production using the MRP generated order release times and verifying on-time completion of the multiple assemblies in the common facility. Numerical experiments are presented to validate the performance of the approach. Optimized batch sizes for minimal work-in-process (WIP) costs can also be obtained using LETSA. Thus, the important objectives of minimizing cycle time for on-time delivery and minimizing schedule costs can be accomplished simultaneously.     

Distributed evolutionary algorithms with hierarchical evaluation

A distributed evolutionary algorithm is presented that is based on a hierarchy of (fitness or cost function) evaluation passes within each deme and is efficient in solving engineering optimization problems. Starting with non-problem-specific evaluations (using surrogate models or metamodels, trained on previously evaluated individuals) and ending up with high-fidelity problem-specific evaluations, intermediate passes rely on other available lower-fidelity problem-specific evaluations with lower CPU cost per evaluation. The sequential use of evaluation models or metamodels, of different computational cost and modelling accuracy, by screening the generation members to get rid of non-promising individuals, leads to reduced overall computational cost. The distributed scheme is based on loosely coupled demes that exchange regularly their best-so-far individuals. Emphasis is put on the optimal way of coupling distributed and hierarchical search methods. The proposed method is tested on mathematical and compressor cascade airfoil design problems.     

Quality assessment of salted, modified atmosphere packaged rainbow trout under treatment with oregano essential oil

The present study evaluated the effect of oregano essential oil (EO) on fresh salted, packaged (45%CO(2)/5%O(2)/50%N(2)) rainbow trout fillets and stored for a period of 21 d at 4 °C. Treatments included the following: M1 (control without added EO), M2 (EO 0.2%, v/w), and M3 (0.4%, v/w). Populations of lactic acid bacteria (LAB), H(2)S-producing bacteria (including Shewanella putrefaciens), Enterobacteriaceae, and Pseudomonas spp. reached higher final numbers in control (M1) than for M2 and M3 samples. Under treatments M2 and M3, total volatile basic nitrogen (TVBN) and trimethylamine nitrogen (TMAN) values were lower than for M1 samples, whereas lipid oxidation, as judged by determination of thiobarbituric acid values (TBA), did not occur during the refrigerated storage period. Interestingly, treatment M2 resulted in a shelf-life extension of 7 to 8 d for the fresh trout fillets, whereas treatment M3 proved unsuitable (due to strong odor) for trout fillet preservation, as determined by sensory evaluation. PRACTICAL APPLICATION: The use of an essential oil such as oregano oil in fresh fish preservation may be considered an alternative "natural" additive, enhancing the sensory characteristics and extending the shelf life of the product.