Selection of Process Conditions for High Pressure Pasteurization of Sea Buckthorn Juice Retaining High Antioxidant Activity

Sea buckthorn berries juice is a nutritious beverage, rich in vitamin C and carotenoids with high antioxidant activity. The main requirements for a freshly squeezed sea buckthorn juice production are the cloud stability and antioxidant activity retention after processing. Appropriate process technologies and conditions have to be applied in order to inactivate pectin methyl esterase (PME), responsible for cloud loss, while maintaining the nutritional characteristics and antioxidant activity of the juice. The objectives of the present work were to study and model the effect of thermal treatment and high pressure (HP) processing on the inactivation kinetics of endogenous PME and on total antioxidant activity alteration. Thermal treatment significantly affected PME inactivation and residual antioxidant activity. Processing even at mild process conditions (60 °C for 1 min) resulted in 2.5-fold antioxidant activity reduction and 50 % PME inactivation compared to untreated sample. Pressure and temperature acted synergistically for PME inactivation that followed first-order kinetics with a residual PME activity at all pressure–temperature combinations used (200–600 MPa and 25–35 °C). The effect of temperature and pressure on the inactivation rate constants was expressed through the activation energy and activation volume, respectively. Values of 163 kJ/mol and ?17 mL/mol at reference pressure of 600 MPa and reference temperature of 35 °C were estimated, respectively. Antioxidant activity of the samples was expressed through the determination of the effective concentration (EC₅₀). A slight increase in sea buckthorn antioxidant activity when applying pressures (200–600 MPa) at ambient temperature (25 °C) was observed compared to the corresponding value of untreated juice. Processing at higher temperatures did not significantly alter the total antioxidant activity of sea buckthorn juice. For sample treated at 600 MPa–35 °C for 5 min, a 5 % reduction of total antioxidant activity was observed. These conditions are proposed as effective process conditions for sea buckthorn juice cold pasteurization, based on the higher antioxidant activity retention and simultaneous PME inactivation.     

Properties of poly(vinyl alcohol)—Bentonite clay nanocomposite films in relation to polymer–clay interactions

This study describes an effective way for the preparation of well‐dispersed, high‐loaded PVA/bentonite nanocomposites with improved properties, based on nanoscale interactions. To this end, a series of Poly(vinyl alcohol)—bentonite clay nanocomposites have been prepared via solvent casting technique and their properties were thoroughly investigated by atomic force microscopy, transmission electron microscopy, X‐Ray diffraction, oxygen and water permeability, water sorption along with mechanical and thermal studies. Microscopic and XRD techniques revealed highly organized regions. Clay content up to 10% led to nanocomposites with high degree of exfoliation. In addition samples with increased filler content (20%) demonstrated also, apart from the delaminated, well‐organized intercalated regions. The nanocomposites exhibited increased mechanical, thermal and gas barrier properties, though they retained their optical clarity. Thus, the Young's modulus of the sample containing 20% clay was increased by 193 times, while the oxygen permeability was decreased about seven times, in regard to the corresponding values of the neat polymer. The obtained results were explored on the basis of nanoscale phenomena and it was concluded that the organized structures and intercalated regions observed on highly loaded samples are attributed to the competitive effect between weaker polymer–polymer interactions in relation to stronger polymer–clay ones. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The influence of extraction versus non-extraction orthodontic treatment on the soft tissue profile

The aim of the present study was to study profile changes following orthodontic harmonization of enlarged overjet and to attempt to trace predictive aspects regarding prognosis of the soft tissue changes. Lateral cephalograms and study models of 40 female patients, at least 12 years old at the start of treatment, with an overjet of > or = 6 mm were analyzed before (T1) and after treatment (T2). Twenty patients were treated without extractions, while in the remaining 20 patients extractions of premolars were carried out bilaterally in both jaws. The 2 groups were found to be highly homogeneous as regards overjet, cephalometric characteristics, space condition in the upper arch at T1 and both at T1 and T2 as regards age. The most striking aspect of the findings was the considerable amount of variability of the soft tissue changes. These changes were found to be rather unpredictable for the individual patient, since the regression models employed could give only a very wide individual prediction range. The relatively small changes registered, using superimposition methods, in both groups as regards the sagittal position of the lips in comparison to the very strong changes observed in relation to the esthetic line shows that the influence of the growth of the chin and/or the nose on the facial profile might be more important than the influence of the orthodontic treatment. The interpretation of the findings in the present study suggests that, apart from marked cases of skeletal convexity or concavity, the extraction versus non-extraction decision should be based primarily upon current knowledge of long-term stability of orthodontic treatment results.     

Craniofacial bone remodeling in growing rats fed a low-calcium and vitamin-D-deficient diet and the influence of masticatory muscle function

Fifty-two male growing rats were randomly divided into three groups. The first group (n = 18) received a hard deficient diet, and the second (n = 18) a soft deficient diet. The control group (n = 16) was fed the normal hard diet. At the beginning and in the middle of the 28-day experimental period oxytetracycline was injected. Two representative coronal sections of the snout and the corresponding contact microradiographs were analyzed. The bone mass of the premaxillary and nasal bones seemed to be less in the two deficient diet groups than in the normal one, due to an increased endosteal bone resorption and decreased bone formation. No difference in the bone apposition rate and pattern could be seen between the deficient hard and soft diet groups, except in the dorsal part of the premaxilla, where the bone formed in the first half of the experiment was markedly more resorbed in the deficient soft diet group during the remaining period than in the deficient hard diet group. The morphology of the sutures was influenced by the altered function, since the sutural space became narrower, and premature obliterations of the internasal suture were observed in the deficient soft diet group. In conclusion, poor bone quality was observed in the skull of rats fed a low-calcium and vitamin-D-deficient diet, with less bone mass than in normal conditions. Masticatory function was a significant factor influencing bone remodeling and sutural growth even in situations in which a metabolic bone disturbance exists.     

Characterisation of porous solids by simplified gas relative permeability measurements

A novel design for the application of a simplified experimental procedure, capable of providing satisfactory relative permeability data for porous media at low relative pressures, is presented. The technique avoids the two-component mixing complications as well as the problems arising from the sample macroscopic inhomogeneity. The latter has been reduced with the aid of a variable pressure compaction procedure. Thus, it becomes easier to utilise the powerful relative permeability technique for the characterisation of the structure of porous solids. Emphasis is given to the combination of the relative permeability data obtained with an analytical approach based on Effective Medium Theory for the calculation of pore connectivity.     

Cloud Computing: Distributed Internet Computing for IT and Scientific Research

Cloud computing is a disruptive technology with profound implications not only for Internet services but also for the IT sector as a whole. Its emergence promises to streamline the on-demand provisioning of software, hardware, and data as a service, achieving economies of scale in IT solutions' deployment and operation. This issue's articles tackle topics including architecture and management of cloud computing infrastructures, SaaS and IaaS applications, discovery of services and data in cloud computing infrastructures, and cross-platform interoperability. Still, several outstanding issues exist, particularly related to SLAs, security and privacy, and power efficiency. Other open issues include ownership, data transfer bottlenecks, performance unpredictability, reliability, and software licensing issues. Finally, hosted applications' business models must show a clear pathway to monetizing cloud computing. Several companies have already built Internet consumer services such as search, social networking, Web email, and online commerce that use cloud computing infrastructure. Above all, cloud computing's still unknown "killer application" will determine many of the challenges and the solutions we must develop to make this technology work in practice.     

GASIFICATION OF GREEK LIGNITE IN AN INDIRECT HEAT (ALLOTHERMAL) ROTARY KILN GASIFIER

This work reports the performance results of a pilot-size lignite gasification plant. The feed material was Greek lignite (Megalopolis), currently being employed for electricity generation in pulverized lignite-fired thermoelectric stations. Low energy conversion efficiency, low station availability, and environmental issues call for developing improved processes, e.g., an IGCC (Integrated Gasification Combined Cycle). An indirect heat (allothermal) rotary kiln was selected as the lignite gasification reactor for developing an overall gasification process of improved efficiency. Weeklong gasification runs, at near atmospheric pressure and maximum temperature in the range 900-950°C, validated high DAF lignite conversions, i.e., 90-95%, and the production of a medium heating value synthesis gas (i.e., 11-13 MJ/Nm 3 dry basis), despite the use of air for burning recycled product gas for process heating. Gas composition is equivalent to that of autothermal gasifiers (e.g., Lurgi, Winkler, Koppers-Totzek), which operate on oxygen, under pressure and strict moisture and particle size specifications. Similarly, the kiln gas is comparable to that of an allothermal, high-pressure, fluidized bed gasifier running with a high rank coal feed. The data indicate satisfactory gasification efficiency and a good thermal efficiency that should be improved further through heat integration of a scaled-up process based on an indirect heat rotary kiln gasifier.     

Application of High Pressure for Selective Activity Regulation of Starter Cultures Aminopeptidases Involved in Ripening of Brined Cheeses

The combined effect of high pressure processing and temperature on aminopeptidases activity of lactic acid bacteria used as starter cultures in brined cheese manufacturing, in order to find the optimum process conditions for acceleration of the significant long-duration cheese ripening step, was investigated.The effect of high hydrostatic pressure (HP) (100–450 MPa) combined with temperature (20–40 °C) on the activity of five aminopeptidases (PepN, PepX, PepY, PepC, and PepA) of Streptococcus thermophilus ACA-DC 0022 and Lactococcus lactis ACA-DC 0049, used as the starter culture for white Greek brine cheese (feta) production, was studied. S. thermophilus aminopeptidases PepN, PepX, PepA, and PepC were activated at pressures up to 200 MPa, and all studied temperatures (20–40 °C), while for L. lactis, PepN, X, and Y were activated at pressures up to 300 MPa and temperatures up to 30 °C and PepA at the same temperature range but milder pressures (up to 200 MPa). For L. lactis, PepC an increase in activity was observed at all studied pressures but only at 20 °C. A multi-parameter equation was used for predicting the activation of all aminopeptidases in the pressure and temperature domain. Overall, processing at 200 MPa and 20 °C may be selected as the optimum conditions for maximum activation of all aminopeptidases of both S. thermophilus ACA-DC 0022 and L. lactis ACA-DC 0049. A 20-min treatment at these conditions leads to an average threefold increase in activity which could lead to better and faster maturation of white cheese.     

Extensional flow induced miscibility in a polymer blend

Summary Extensional flows can induce miscibility in a polymer blend of polystyrene with poly(vinyl methyl ether). Miscibility is observed as a change from turbidity to optical clarity when a phase separated blend flows isothermally in planar extension. In a start-up experiment at temperatures above the LCST, optical clarity does not appear instantaneously but after a time which depends on the rate of extension and the temperature, and it appears first near the region of highest extension. This effect is opposite to the observation for polymer solutions which exhibit shear-induced demixing. We attribute this to the fact that enthalpic effects largely determine blend miscibility, while the phase behavior of solutions is essentially controlled by entropic contributions. Since a deformation field decreases the configurational degrees of freedom of a polymer molecule, demixing is favored in solutions. However, the alteration of specific interactions rather than this entropic effect appears to be much more important in blends.     

Performance and effectiveness trade‐off for checkpointing in fault‐tolerant distributed systems

Checkpointing has a crucial impact on systems' performance and fault‐tolerance effectiveness: excessive checkpointing results in performance degradation, while deficient checkpointing incurs expensive recovery. In distributed systems with independent checkpoint activities there is no easy way to determine checkpoint frequencies optimizing response‐time and fault‐tolerance costs at the same time. The purpose of this paper is to investigate the potentialities of a statistical decision‐making procedure. We adopt a simulation‐based approach for obtaining performance metrics that are afterwards used for determining a trade‐off between checkpoint interval reductions and efficiency in performance. Statistical methodology including experimental design, regression analysis and optimization provides us with the framework for comparing configurations, which use possibly different fault‐tolerance mechanisms (replication‐based or message‐logging‐based). Systematic research also allows us to take into account additional design factors, such as load balancing. The method is described in terms of a standardized object replication model (OMG FT‐CORBA), but it could also be applied in other (e.g. process‐based) computational models. Copyright © 2006 John Wiley & Sons, Ltd.