Foci of contamination of Listeria monocytogenes in different cheese processing plants

Listeria monocytogenes is a ubiquitous bacterium widely distributed in the environment that can cause a severe disease in humans when contaminated foods are ingested. Cheese has been implicated in sporadic cases and in outbreaks of listeriosis worldwide. Environmental contamination, in several occasions by persistent strains, has been considered an important source of finished product contamination. The objectives of this research were to (i) evaluate the presence of L. monocytogenes within the factory environments and cheeses of three processing plants, artisanal producer of raw ewe's milk cheeses (APC), small-scale industrial cheese producer (SSI) and industrial cheese producer (ICP) each producing a distinct style of cheese, all with history of contamination by L. monocytogenes (ii) and identify possible sources of contamination using different typing methods (arsenic and cadmium susceptibility, geno-serotyping, PFGE). The presence of markers specific for 3 epidemic clones (ECI–ECIII) of L. monocytogenes was also investigated. Samples were collected from raw milk (n = 179), whey (n = 3), cheese brining solution (n = 7), cheese brine sludge (n = 505), finished product (n = 3016), and environment (n = 2560) during, at least, a four-year period. Listeria monocytogenes was detected in environmental, raw milk and cheese samples, respectively, at 15.4%, 1.1% and 13.6% in APC; at 8.9%, 2.9% and 3.4% in SSI; and at 0%, 21.1% and 0.2% in ICP. Typing of isolates revealed that raw ewe's milk and the dairy plant environment are important sources of contamination, and that some strains persisted for at least four years in the environment. Although cheeses produced in the three plants investigated were never associated with any case or outbreak of listeriosis, some L. monocytogenes belonging to specific PFGE types that caused disease (including putative epidemic clone strains isolated from final products) were found in this study.     

Remote sensing estimates of boreal and temperate forest woody biomass: carbon pools, sources, and sinks

The relation between satellite measurements of the normalized difference vegetation index (NDVI), cumulated over the growing season, and inventory estimates of forest woody biomass carbon is estimated statistically with data from 167 provinces and states in six countries (Canada, Finland, Norway, Russia and the USA for a single time period and Sweden for two periods). Statistical tests indicate that the regression model can be used to represent the relation between forest biomass and NDVI across spatial, temporal and ecological scales for relatively long time scales. For the 1.42 billion ha of boreal and temperate forests in the Northern Hemisphere, the woody biomass carbon pools and sinks are estimated at a relatively high spatial resolution (8×8 km). We estimate the carbon pool to be 61±20 gigatons (10⁹) carbon (Gt C) during the late 1990s and the biomass sink to be 0.68±0.34 Gt C/year between the 1982 and 1999. The geographic detail of carbon sinks provided here can contribute to a potential monitoring program for greenhouse gas emission reduction commitments under the Kyoto Protocol.     

相干光源的研制现状

本文叙述了近年来国外相干光源的研究及其进展。并对频谱线宽、FM 调制特性和波长可变特性作了介绍。     

1.3μm high—power superluminescent diode

The result of the evaporation of Sio/SiO2 two layer antireflection coatings monitored by the MODEL IL 400 DEPOSITION CONTROLLER is re-ported.A superluminescent diode with high output power is fabricated by evaporate-ing antireflection coating on the front facet of 1.3цm buried heterostructure laser.     

国际基本安全标准的进展

本文主要阐述了由国际原子能机构等国际组织制定的“国际电离辐射防护和辐射源安全的基本安全标准”的主要特点。标准主要是基于国际放射防护委员会１９９０年建议书，但也考虑了国际核安全咨询组建议的原则。其内容不仅包括辐射防护，还包括辐射源的安全，在总结世界各国辐射防护和安全实践经验的基础上，在潜在照射、医学照射、废物管理、豁免值、事故应急、慢性照射、天然照射和医学防护等方面均提出了一些新的和具体的要求。我国有必要在仔细研究这一标准的基础上结合具体情况，修订现行标准。文中提出了在采用这一标准时需要研究的一些问题。     

S波段低相位噪声参考原

阐述了研制Ｓ波段低相噪参考源所需的晶振相噪特性、倍频器相噪特性，指出研制低相噪参考源的途径，在此基础上研制出了Ｓ波段极低相噪参考源，经严格测量，其相位噪声在１ｋＨｚ处优于－１２１ｄＢｃ／Ｈｚ，１００ｋＨｚ以外的相噪平底优于－１３５ｄＢｃ／Ｈｚ。所用２０次培频器几乎无附加相噪。     

浅议博览建筑设计的象征性——以安徽广德文化中心设计实践为例

博览建筑具有强烈的象征性,如何继承和汲取传统建筑文化的精华、创造出具有地域特色的博览建筑是设计师面临的一个重要课题,本文从建筑象征性的分类、意向来源及载体等方面,探讨表现博览建筑象征性的设计方法及策略。     

How should price-responsive electricity tariffs evolve? An analysis of the German net demand case

This research proves, using daily data, that net demand has a higher impact on the German wholesale market price than the traditional concept of electricity demand. The aim of this paper is to develop a broader framework for the design of new tariffs for German consumers, taking net demand as its primary reference. To accomplish this, a classification of net demand by level was developed. The findings of this research provide new insights about the occurrence of net valley and net peak periods, something which is useful for designing tariffs, affecting how the price should be differentiated during the day.     

A comparative study of VOCs in Singapore and European office buildings

This study compares the characteristics of volatile organic compounds (VOCs) and the associated factors affecting them within European (EU) and Singapore buildings. Generally, concentrations of target VOCs determined in the two types of buildings were within health and comfort guidelines. This study found that concentrations of 2-methylpentane and n-heptane were significantly higher in the EU buildings, while those of n-tetradecane, 2-ethyl 1-hexanol, benzene, toluene, m/p-xylene, benzaldehyde and naphthalene significantly higher in Singapore buildings. Area specific emission rates of the methylpentane isomers, n-heptane and isoprene were significantly higher in the EU buildings, while those of 2-ethyl 1-hexanol, benzene, toluene and naphthalene were significantly higher in Singapore buildings. Lower ventilation rates within Singapore buildings caused relatively higher concentrations of m/p-xylenes and benzaldehyde despite no differences in emission rates between the two types of buildings. Elevated levels of 2-ethyl 1-hexanol in Singapore buildings are due to the higher air velocities and relative humidity indoors. There were no differences in 1,1,1-trichloroethane and 2-propanone levels, suggesting similar use of consumer products and occupant densities relating these two VOCs. Higher emission rates of methylpentane isomers and heptane were associated with the use of adhesives and solvents related to internal surfaces while higher emission rates for isoprene in the EU buildings were associated with environmental tobacco smoke (ETS). Higher levels of benzene, toluene and naphthalene in ETS-free Singapore buildings were associated with human-related activities.     

入侵检测系统研究综述

首先论述了入侵检测系统(IDS)的研究概况,然后使用五种分类标准对入侵检测系统进行了科学分类,它们分别是控制策略、同步技术、信息源、分析方法和响应方式。接着,介绍了入侵检测系统的一些重要工具,并重点研究分析了基于信息源IDS和基于分析方法IDS,最后给出了入侵检测系统研究趋势和展望。