Reduction of Listeria monocytogenes, Salmonella spp., and Escherichia coli O157:H7 During Processing of Country-cured Hams

ABSTRACT: The country-cured ham process, including curing, equalization, cold-smoked or nonsmoked, and aging up to 6 mo, was validated and showed its effectiveness in achieving a 6-log reduction of Listeria monocytogenes, Salmonella spp., and Escherichia coli O157:H7. The viable counts of L. monocytogenes populations decreased to below detection levels after 206 d, Salmonella populations required 122 d, and E. coli O157:H7 required 66 d. However, L. monocytogenes -inoculated hams were positive and Salmonella spp-inoculated and E. coli O157:H7-inoculated hams were negative following enrichment procedures at the end of the aging process. Therefore, the survival of L. monocytogenes on country-cured ham represents a risk.     

A frequency-domain analytical model of an uncontrolled single-phasevoltage-source rectifier

The harmonic currents generated by the single-phase rectifier are well known. As the levels of these currents become larger, the use of power conditioners, such as shunt active filters, to lower the levels is becoming more attractive. In order to analyze the interaction between the condition, AC system and rectifier, it is necessary to have an accurate model of the rectifier. This paper describes a frequency-domain analytical model of the single-phase rectifier. The model includes the dominant frequency transfer mechanisms. These are the direct transfer and that due to the modulation of the switching instants. A small-signal linearized analysis is presented and the behavior predicted is confirmed by perturbation analysis using time-domain simulation. Accurate results are obtained, and the importance of including the switching instant modulation is shown     

Performance of a building integrated photovoltaic/thermal (BIPVT) solar collector

The idea of combining photovoltaic and solar thermal collectors (PVT collectors) to provide electrical and heat energy is an area that has, until recently, received only limited attention. Although PVTs are not as prevalent as solar thermal systems, the integration of photovoltaic and solar thermal collectors into the walls or roofing structure of a building could provide greater opportunity for the use of renewable solar energy technologies. In this study, the design of a novel building integrated photovoltaic/thermal (BIPVT) solar collector was theoretically analysed through the use of a modified Hottel-Whillier model and was validated with experimental data from testing on a prototype BIPVT collector.The results showed that key design parameters such as the fin efficiency, the thermal conductivity between the PV cells and their supporting structure, and the lamination method had a significant influence on both the electrical and thermal efficiency of the BIPVT. Furthermore, it was shown that the BIPVT could be made of lower cost materials, such as pre-coated colour steel, without significant decreases in efficiency.Finally, it was shown that by integrating the BIPVT into the building rather than onto the building could result in a lower cost system. This was illustrated by the finding that insulating the rear of the BIPVT may be unnecessary when it is integrated into a roof above an enclosed air filled attic, as this air space acts as a passive insulating barrier.     

Identification of hepatic metabolites of two highly carcinogenic polycyclic aza-aromatic compounds, 7,9-dimethylbenz[c]acridine and 7,10-dimethylbenz[c]acridine

The hepatic microsomal metabolites of the highly carcinogenic dimethylbenzacridines, 7,9-dimethylbenz[c]acridine (7,9-DMBAC), and 7,10-dimethylbenz[c]acridine (7,10-DMBAC) were obtained with preparations from 3-methylcholanthrene-pretreated rats. Metabolites were separated by reversed-phase HPLC and characterized using UV spectral data and chemical ionization-mass spectrometry after trimethylsilylation and GC. Comparisons with products formed in the presence of the epoxide hydrolase inhibitor, 1,1,1-trichloropropane 2,3-oxide and with those formed from the three synthetic alcohol derivatives of each parent compound, aided the assignment of firm or tentative structures to 16 products from 7,9-DMBAC found in 22 reversed-phase chromatographic peaks, and for 17 products of 7,10-DMBAC found in 19 chromatographic peaks. The more abundant metabolites were derived from oxidation of the methyl groups. Other metabolites were dihydrodiols, epoxides, phenols and secondary metabolites. The 9-methyl group prevented dihydrodiol formation at the 8,9-position from 7,9-DMBAC, and for each carcinogen, the 3,4-dihydrodiol was formed. As well, 3,4-dihydrodiols of methyl oxidized compounds were found.     

Pretest-posttest field studies on psychological restoration: a descriptive review and reflections for the future

Almost four decades ago, Attention Restoration Theory and Stress Recovery Theory postulated that nature could help people to recover from the attentional fatigue and the emotional negative outcomes coming from their daily performance. Since then, these theories have inspired a great amount of research. In this review, 19 restoration pretest-posttest field studies were selected. A systematic analysis of the papers was conducted using two rating tools to assess the quality of the studies and to detect their main strengths and weaknesses. The results allowed us to synthesise the results of this sample of studies, to reflect about the nature of the research conducted until today and to point to some issues and challenges that might be addressed in future studies.     

Autonomous pollination of individual kiwifruit flowers: Toward a robotic kiwifruit pollinator

There is an increasing concern that the traditional approach of natural kiwifruit pollination by bees may not be sustainable. The alternatives are currently too costly for most growers due to high labor requirements or inefficient usage of expensive pollen. This paper presents a performance evaluation of a novel kiwifruit pollinating robot designed to provide a more efficient, reliable, and cost‐effective means of producing kiwifruit. The robot comprises a novel air‐assisted sprayer, a machine vision system employing convolution neural networks, and a flower targeting system for efficient and effective application of pollen to individual flowers. We show that this pollination system is capable of individually targeting and pollinating 79.5% of flowers at 3.5 km/hr while using comparable amounts of pollen to commercial Cambrian operators. Furthermore, flowers that were successfully pollinated at 1 km/hr grew into the first robotically pollinated kiwifruit which were comparable in quality to commercially grown kiwifruit. However, the overall fruit set was found to be well below commercial requirements and further work on increasing the overall yield is required.     

Real-time optimization of an active filter's performance

Recent advances in power electronics have meant that many loads now draw a distorted current from the power supply. For the same real power consumed, the apparent power for the distorted load is greater than the equivalent sinusoidal load. A real-time active filter optimization algorithm has been implemented in a TMS320C30 DSP, with the aim of maximizing the monetary saving from active filtering by reducing the apparent power consumed at the point of supply. As the basis for this optimization a savings function which takes into account active filter efficiency, the cost of energy, and the supply and load current distortion before and after filtering, has been derived. A simplex optimization technique, which is able to find the optimum operating point even under varying load conditions, is used to maximize these energy savings     

Plasticity in peeling

Contrary to classical theory, a high proportion of bond failures by peeling involve progressive plastic adherend flexural yield. Such yield occurs with adherend thicknesses below a critical value, T_c, which is shown calculable by combining elastic peel mechanics with plastic bending criteria. The geometry of such “peel with yield,” and thence the moment-controlled peel forces, can be accounted for only if the adhesive is also recognized as behaving essentially plastically. Subsequent plastic adherend unbending is important with highly extensible adhesives. The geometry of “legging” peel in such cases is best described by fully plastic mechanics. These are derived and shown to account for literature data on dependencies of peel force upon peel rate and adhesive thickness. “Stick-slip” peel phenomena are indicated to be controlled by recurring interacting plastic–elastic transitions, in both adhesive and adherend: adhesive strain rate is critical in such phenomena. Four regimes of peel behavior can therefore apply as adherend thickness (T) increases, with peel forces proportional respectively to T⁰, T^2/3, T^3/2 (above T_c) and finally controlled by moment limitations due to joint configurational constraints (“cleavage”).