Joint Determination of the State Dimension and Autoregressive Order for Models with Markov Regime Switching

Abstract. This paper is concerned with the problem of joint determination of the state dimension and autoregressive order of models with Markov‐switching parameters. A model selection procedure is proposed which is based on optimization of complexity‐penalized likelihood criteria. The efficacy of the procedure is evaluated by means of Monte Carlo experiments.     

The hurdle effect of osmotic pretreatment and high‐pressure cold pasteurisation on the shelf‐life extension of fresh‐cut tomatoes

Tomatoes are perishable products due to the activity of microorganisms and endogenous enzymes. The objective was to produce cut tomatoes with extended shelf life, using the combined hurdle effect of osmotic pretreatment (OD) and high pressure (HP), instead of a conventional one‐step thermal process. Samples were processed in a multicomponent osmotic solution at 35 °C, subsequently cold‐pasteurised in pack at 600 MPa and stored at 5–15 °C. Quality deterioration during isothermal and nonisothermal storage was kinetically modelled. Both OD process and OD‐HP combined process caused an increase in lycopene content that was well retained. Texture, colour and flavour of treated samples were evaluated as similar to fresh, with OD‐HP samples showing better retention during storage. Being microbiologically stable, shelf life of OD‐HP samples was limited by sensory deterioration, whereas OD samples were rejected due to eventual microbial growth. Shelf life of OD and OD‐HP samples was estimated at 77 and 181 days, respectively, at 5 °C.     

Survival of Escherichia coli O157:H7 in Galotyri cheese stored at 4 and 12 degrees C

Post-process contamination of fresh acid-curd cheeses with Escherichia coli O157:H7 may pose a risk considering the low infectious dose and the ability of the pathogen to survive in acidic foods. To evaluate its survival in Galotyri, a traditional Greek acid-curd cheese, portions (0.5 kg) of two commercial fresh products, one artisan (pH 3.9+/-0.1) and the other industrial (pH 3.7+/-0.1), were inoculated with approximately 3.0 or 6.5 log cfu g(-1) of a five-strain cocktail of E. coli O157:H7, including rifampicin-resistant derivatives of the strains ATCC 43895 and ATCC 51657, and stored aerobically at 4 and 12 degrees C. Survival was monitored for 28 days by plating cheese samples on tryptic soy agar with 100 mg l(-1) rifampicin (TSA+Rif), SMAC and Fluorocult E. coli O157:H7 agar media. The pathogen declined much faster (P<0.05) in the industrial as compared to the artisan cheeses at both temperatures. Thus, while E. coli O157:H7 became undetectable by culture enrichment after 14 days at 4 degrees C in industrial samples, irrespective of the inoculation level, populations of 1.4-1.9 and 4.2-5.1 log cfu g(-1) survived after 28 days in the corresponding artisan cheeses with the low and high inocula, respectively. Survival was longer and greater (P<0.05) on TSA+Rif than on SMAC and Fluorocult, indicating the presence of acid-injured cells. Interestingly, survival of E. coli O157:H7 after 14-28 days in cheeses was better at 12 degrees C than at 4 degrees C, probably due to yeasts which grew on the surface of temperature-abused cheeses. The large difference in the pathogen's inactivation between the industrial and artisan cheeses at 4 degrees C could not be associated with major differences in pH or type/concentration of organic acids, suggesting another anti-E. coli O157:H7 activity by the industrial starter. The high survival of the pathogen in artisan Galotyri under conditions simulating commercial storage should be of concern.     

Determination of organochlorine pesticides in marine sediments samples using ultrasonic solvent extraction followed by GC/ECD

A rapid multiresidue method has been developed for the analysis of 17 organochlorine pesticides (OCPs) (-HCH, γ-HCH, β-HCH, δ-HCH, aldrin, heptachlor epoxide, endosulfan I, 4,4-DDE, dieldrin, endrin, 4,4-DDD, endosulfan II, 4,4-DDT, endrin aldehyde, endosulfan sulfate, methoxychlor and endrin ketone) in marine sediments. The method is based on the ultrasonic solvent extraction (USE) of sediment samples. The extraction procedure was optimised with regard to the solvent type, amount of solvent and duration of sonication steps. Analytical determinations of the 17 OCPs were carried out by gas chromatography using electron capture detector (GC/ECD). The highest recoveries from sediment samples spiked at trace concentrations of 50 ng g⁻¹ obtained when samples were extracted two times by ultrasonication for 20 min with 5 mL of dichloromethane. Recovery studies were performed at 1, 2, 5, 10 and 50 ng g⁻¹ fortification levels and correlation coefficients obtained ranged from 0.9652 to 0.9993 showing that the method is linear over the range assayed. The detection limits (signal/noise = 3) for the organochlorine compounds tested in marine sediments varied from 0.1 to 1 ng g⁻¹ dry weight. USE of OCPs from marine sediments using dichloromethane showed satisfactory extraction efficiencies combined with simplicity of use and low solvent consumption.     

Harmonic distortion assessment for a single-phase grid-connected photovoltaic system

Nowadays, grid-connected photovoltaic (PV) systems constitute an emerging technology. This has given rise to concerns about their contribution to harmonic distortion levels in utility grids. Valuable insight into the electrical behavior of such a system, including its impact on power quality, can be obtained through extensive simulation studies. In this paper, models are developed with a focus on not only accurate but also fast simulation of grid-connected PV systems. First, time-consuming processes are identified and discussed. These are mainly associated with the semiconductor power switching devices and the non-linear characteristics of the system components (isolation transformer, PV generator). Next, models are developed in order to increase simulation speed by avoiding time-consuming procedures. The validity of the approach is ascertained by comparing simulation results with published measurements. A case study is then performed in order to obtain current and voltage waveforms and, subsequently, harmonic distortion levels. Further simulations are carried out using different values for various system parameters in order to make an assessment of their impact in terms of waveform distortion.     

BDD anodic oxidation as tertiary wastewater treatment for the removal of emerging micro‐pollutants,pathogens and organic matter

This work reports for the first time the removal of 17α‐ethynylestradiol (EE2), a synthetic estrogen hormone, from secondary treated effluents by electrochemical oxidation. Experiments were conducted in a single compartment reactor comprising a boron‐doped diamond (BDD) anode and a zirconium cathode. EE2, in the range 100–800 µg L^?1, was spiked in the post‐chlorination effluent of a municipal treatment plant and oxidized at 0.9–2.6 mA cm^?2 current density. Complete degradation of 100 µg L^?1 EE2 was achieved in 7 min at 2.1 mA cm^?2 and inherent conditions, while the addition of 0.1 mol L^?1 NaCl achieved removal in just a few seconds. The process was then tested in the pre‐chlorination effluent at 2.1 mA cm^?2 and inherent conditions; complete E. coli killing and EE2 removal occurred in just 1.5 and 3.5 min, respectively, while overall estrogenicity (assessed by the YES assay) and residual organic matter (in terms of chemical oxygen demand (COD)) decreased by 50% and 85% after 30 min, respectively. These results clearly show the potential of BBD electrochemical oxidation to serve as an efficient tertiary wastewater treatment. Copyright © 2011 Society of Chemical Industry     

Diffusion-Induced Void Evolution in Core–Shell Nanowires: Elaborated View on the Nanoscale Kirkendall Effect

In 2006, our group reported the fabrication of ultra-long single-crystal ZnAl₂O₄ spinel nanotubes, starting from ZnO/Al₂O₃ core–shell nanowires, involving the nanoscale Kirkendall effect. In this feature paper, we introduce our up-to-date results on the design of porous and hollow 1D nanostructures following this solid-state interfacial reaction route. In particular, we present our recent understandings on void evolution induced by the unbalanced diffusion. We first give a short introduction on the distinctions of core–shell nanowires in interfacial nanoreactions, in contrast to other systems. Then we discuss the roles of desorption, stress, and/or defects on void evolution and nanotube formation. Our results demonstrate that the stress- and defects-engineered diffusion mechanism can be used to specifically design hollow nanostructures, which will open up a new window in exploitation of the Kirkendall effect at the nanoscale.     

Fair digital signing: The structural reliability of signed documents

The exchange of digitally signed data inherits all the problems related to the indeterminacy of human communication, which are further intensified by the legal implications of signing. One of the fundamental intrinsic weaknesses of digital signatures is that the signer creates a signature on a series of bits, which may be differently transformed and perceived by the verifier (or relying party), due to the inevitable differences in the intention and the purpose of the two agents. As a result, syntactic and semantic distance is introduced between a signer and a relying party. In this paper we suggest a framework that models the process of digital signing, using several virtual and interrelated levels of communication, thereby promoting the analytic and synthetic exploration of the entities and the transformations involved. Based on this exploration, it is possible to indicate the favorable conditions for mutual understanding between the signer and the relying party. We focus on the syntactic and presentation levels of the communication process and we introduce the notion of structural reliability of a syntactic component, as a measure of how securely and accurately a signed document can be used. It is argued that structural reliability depends on a quantitative metric, such as the structural informativeness along with other qualitative characteristics of the syntactic component. The structural reliability of several document representation protocols is evaluated and it is concluded that the higher the informativeness of the protocol, the less the semantic distance produced, provided that the communicating parties have the capacity to handle this protocol.     

Structural analysis of W7-X: From design to assembly and operation

The Wendelstein 7-X (W7-X) modular stellarator is in the assembly phase at the Max-Planck-Institut für Plasmaphysik in Greifswald, Germany. The design of the “basic machine”, i.e. without in-vessel components, diagnostics and periphery, is largely completed, structural parameters such as bolt preload, initial conditions for contact elements, etc. are defined, and most of the components are manufactured and partly assembled. Therefore, the focus of structural analysis was shifted towards fast analyses of non-conformities, changes in the assembly procedure, and exploration of operational limits. Assembly-related work is expected to continue until commissioning of the machine, however, with decreasing intensity. In parallel the analysis requirements for in-vessel components, diagnostics and periphery will increase.This paper focuses on the most remarkable results, on special problems which had to be solved, on strategic issues like parameterization, complex finite element model structuring and benchmarking with alternative models in different codes, on assumptions of reasonable safety margins and expected tolerances, and on confirmation of analysis results by tests. Finally it highlights some lessons learned so far, which might be relevant also for other large fusion machines, and gives an outlook on future work.