Levels of microbial contamination of domestic refrigerators in Italy

AimAccording to the EFSA Report 2013, 32.7% of outbreaks of foodborne illness registered in Europe occurs within the home, due to inadequate hygienic behaviour of consumers when preparing foods in the kitchen. The efficacy of proper cleaning of cutting boards, dishes and cutlery in limiting microbial cross-contaminations in the kitchen has been documented many times, whereas few researches have been performed to determine the microbial load of the internal walls of domestic refrigerators, in Italy. The aim of this investigation is to ascertain the role played by internal surfaces of home refrigerators as possible sources of microbial contamination of foods.Material and methodsWe analyzed 293 domestic refrigerators of students or workers at the university campus of Agripolis (Legnaro, Italy). For each refrigerator, 2 internal surfaces were sampled using sponge-bags. The amounts of total viable count (TVC), Gram-negative spoiling bacteria, moulds and yeasts and the main pathogenic bacterial species were determined.ResultsTVCs greater than 1 log CFU cm⁻² are in a little over 50% of the samples analyzed and are found mainly on the bottom of the refrigerator (61%) compared to the walls (39%) (P < 0.001). Even for other microbial counts the risk ratio of finding them on the bottom of the refrigerator is significantly higher than on the walls; the possibility of there being a finding on the bottom with respect to the walls varies from 2.5 to 8.5 times respectively for moulds and Aeromonas spp. Salmonella spp. was found in 1.7% of the samples, Bacillus cereus in 5.6%, Coagulase-positive staphylococci (CPS) in 4%, the prevalence of which is always higher on the bottom of the refrigerator. Listeria monocytogenes and Yersinia enterocolitica were never found.ConclusionsIt is necessary to better educate consumers to clean their appliances more frequently.     

Development of TSACO and application to Chinese HCCB TBM cooling system

In this study, a thermal-hydraulic and safety analysis code (TSACO) for helium cooling system has been developed using Fortran 90 language, and the simulation has been performed for the cooling system of the Chinese helium cooled ceramic breeder test blanket module (CH HCCB TBM). The semi-implicit finite difference technique was adopted for the solution of the dynamic behavior of helium cooling system. Furthermore, a detailed illustration of the numerical solution for heat structures and critical model was presented. The code was verified by the comparison of RELAP5 code with the same initial condition, boundary condition, heat transfer and flow friction models. The TBM inlet/outlet temperatures and pressure drop were obtained and the results simulated by TSACO were shown in good agreement with those by RELAP5. Thereafter, the design basis accident in-vessel loss of coolant accident (LOCA), was investigated for the CH HCCB TBM cooling system. The critical flow model was also verified by comparing with RELAP5 code. The results indicated that the TBM can be cooled down effectively. The vacuum vessel (VV) pressure and the mass of helium spilled into the VV maintained below the design limits with a large margin.     

The design and utilization of a high-temperature helium loop and other facilities for the study of advanced gas-cooled reactors in the Czech Republic

This paper focuses on the research infrastructure of advanced gas cooled reactors in the Czech Republic, particularly on the high-temperature helium loop HTHL, which is a unique facility of its kind. HTHL is intended mainly for testing structural materials. It also can be used to research technologies relating to helium coolant. The maximum temperature and pressure that can be used within the specimen testing space are 900 °C and 7 MPa, respectively, and the maximum gas flow rate in the main loop is 38 kg/hr. Originally, the equipment was envisaged as a device for corrosion tests of materials in the reactor LVR-15 but, according to current plans, a different equipment will be built for this purpose within the frame of the SUSEN project. At the same time, an additional helium loop (S-Allegro) will be built to test selected components of advanced gas-cooled reactors.     

活性炭纤维吸附装置在发泡剂CFCs回收中的应用

在冰箱拆卸过程中，聚氨酯硬质泡沫会释放出大量CFCs，而CFCs是重要的温室气体之一，因此，冰箱拆卸过程中尾气中CFCs回收受到大家重视。本文介绍了利用活性炭纤维回收家电拆卸过程中释放出氟里昂的装置。该装置自动运行，工艺先进，并且利用高效的吸附剂一活性炭纤维。运行实践表明，利用该装置可以有效的处理冰箱拆卸过程中释放出的CFCs。     

4min快速脱模环戊烷型组合聚醚

开发了一种以聚醚多元醇、泡沫稳定剂、叔胺催化剂、环戊烷、水等原料配置的组合聚醚,可用于4 min快速脱模冰箱组合料的生产.讨论了聚醚多元醇、催化剂、泡沫稳定剂、环戊烷等对快速脱模的影响.结果表明,该组合聚醚贮存稳定性好,制得的的泡沫性能优良,能满足4 min快速脱模冰箱组合料的生产.     

EAST氦制冷机静态模拟分析

采用机理建模的方法建立了EAST制冷机单元部件和流程的静态数学模型,用C++语言开发出对应静态模型的模拟计算软件,应用该软件分别对4.5 K液化/制冷和4.5 K液化/制冷+3.5 K制冷流程进行静态模拟计算,并分析了4.5 K液化/制冷+3.5 K制冷模式下制冷机各单元部件的有效能损失以及制冷量与各项热力学参数之间的...     

Experimental study on the sealing clearance between the labyrinth sealing displacer and cylinder in the 10 K G-M refrigerator

The labyrinth sealing displacer has been optimal designed to improve the operating stability and life-time of 10 K G-M refrigerator. The displacer was made of stainless steel 304 or inconel 718, coated with PTFE on its outer surface. Compared to the traditional piston-ring sealing displacer, the sealing clearance between the ridge of the labyrinth sealing displacer and cylinder is critical to the cooling performance of the G-M refrigerator. The displacers with different sealing clearances were experimentally studied, and the optimal clearance was given. The effects of the materials of the displacers and the system charge pressures on the performance of the labyrinth sealing were also tested and analyzed.     

Experimental results for a magnetic refrigerator using three different types of magnetocaloric material regenerators

Magnetic refrigeration is a potentially environmentally-friendly alternative to vapor compression technology because it has a potentially higher coefficient of performance and does not use a gaseous refrigerant. The active magnetic regenerator refrigerator is currently the most common magnetic refrigeration device for near room temperature applications, and it is driven by the magnetocaloric effect in the regenerator material. Several magnetocaloric materials with potential magnetic refrigeration applications have recently been developed and characterized; however, few of them have been tested in an experimental device. This paper compares the performance of three magnetocaloric material candidates for AMRs, La(Fe,Co,Si)₁₃, (La,Ca,Sr)MnO₃ and Gd, in an experimental active magnetic regenerator with a parallel plate geometry. The performance of single-material regenerators of each magnetocaloric material family were compared. In an attempt to improve system performance, graded two-material regenerators were made from two different combinations of La(Fe,Co,Si)₁₃ compounds having different magnetic transition temperatures. One combination of the La(Fe,Co,Si)₁₃ materials yielded a higher performance, while the performance of the other combination was lower than the single-material regenerator. The highest no-load temperature span was achieved by the Gd regenerator.     

Review on numerical modeling of active magnetic regenerators for room temperature applications

The active magnetic regenerator (AMR) is an alternative refrigeration cycle with a potential gain of energy efficiency compared to conventional refrigeration techniques. The AMR poses a complex problem of heat transfer, fluid dynamics and magnetic field, which requires detailed and robust modeling. This paper reviews the existing numerical modeling of room temperature AMR to date. The governing equations, implementation of the magnetocaloric effect (MCE), fluid flow and magnetic field profiles, thermal conduction etc. are discussed in detail as is their impact on the AMR cycle. Flow channeling effects, hysteresis, thermal losses and demagnetizing fields are discussed and it is concluded that more detailed modeling of these phenomena is required to obtain a better understanding of the AMR cycle.     

Test of a micromegas detector with helium-based gas mixtures for active target time projection chambers utilizing radioactive isotope beams

A Micromegas detector was tested in a helium-carbon dioxide mixture at atmospheric pressure. A stable operation of the detector was confirmed at a gain of over 10³ for a standard alpha source of ²⁴¹Am. In order to realize a position-dependent gain, an anode strip was biased while keeping the other strips at the ground potential. The gain of the biased strip was reduced by one order of magnitude without affecting the gains of the neighboring strips. The energy spectra at 3.7 MeV, the energy deposited by Am alpha particles in the sensitive region of the Micromegas, were obtained from the total charge and the charge deposit profile along the track. The energy resolutions for helium:carbon dioxide 90:10 mixture at a gas gain of about 100 were 11% FWHM for the former and 4% FWHM for the latter. The present results highlight the Micromegas as a promising electron amplifier of the forthcoming active target time projection chambers that will be dedicated to nuclear reactions with radioactive isotope beams.