Influence of controlled lactic fermentation on growth and sporulation of Bacillus cereus in milk

The growth and sporulation of Bacillus cereus NVH 45 in a fermentor with controlled pH or simulated pH conditions were investigated. The study was carried out in a fermentor to measure the influence of a rapid and a slow lactic acid production on the inhibition of B. cereus in a controlled environment during the initial part of fermentation and to observe if other factors than lactic acid influenced the inhibition. In the controlled pH experiments the pH was allowed to decrease to an end pH 5.0, 5.5 or 6.0 either by Lactobacillus casei 2756 (a fast acid producer) or Lactobacillus acidophilus NCFB 1748 (a slow acid producer). In co-cultures of Lb. casei 2756 and B. cereus NVH 45, low numbers (10-70 cfu/ml) of B. cereus NVH 45 were observed at end pH 5.5 (72 h) while at pH 5.0 no viable cells (<10 cfu/ml) were detected (48-72 h). B. cereus NVH 45 did not sporulate in co-culture with Lb. casei 2756. In co-culture with Lb. acidophilus NCFB 1748, B. cereus NVH 45 sporulated and survived as spores. In these co-cultures B. cereus NVH 45 grew to higher maximum counts (>10(7) cfu/ml) than with Lb. casei 2756 (<10(7) cfu/ml). Significantly different amounts of lactic acid were observed between the two co-cultures after 7 and 12 h. A rapid decrease of pH appears to prevent B. cereus from sporulating and it seems that it is enough to just reach pH 5.0 rapidly and keep that pH to achieve the desirable inhibition of B. cereus. In the simulated pH experiments B. cereus NVH 45 was inoculated in the fermentor and the different pH developments from different LAB strains were monitored by addition of lactic acid. These experiments showed the same tendency: a fast pH reduction during the initial hours of fermentation, simulating lactococci, resulted in complete inhibition of B. cereus NVH 45 (<10 cfu/ml). However, when simulating the pH development of the two different Lactobacillus strains, complete inhibition of B. cereus NVH 45 was not seen. In co-cultures competition for nutrients with consequences for cell density appears to be important. Based on these results it seems that B. cereus must reach a certain density to induce sporulation.     

奥斯陆莫藤斯鲁德教堂

该教堂坐落在一个小山脊的顶部,周围是高大的松树林和一些裸露的岩石。从几何学角度来说,这座教堂是现有基地的附加体,除了小心地移除薄薄的土壤层之外,基地不需要进行爆破和挖掘。这种处理方法更易于保持现有的植被和地形,从而增加了人们对建筑另一层面上的体验。     

Grasping devices and methods in automated production processes

In automated production processes grasping devices and methods play a crucial role in the handling of many parts, components and products. This keynote paper starts with a classification of grasping phases, describes how different principles are adopted at different scales in different applications and continues explaining different releasing strategies and principles. Then the paper classifies the numerous sensors used to monitor the effectiveness of grasping (part presence, exchanged force, stick-slip transitions, etc.). Later the grasping and releasing problems in different fields (from mechanical assembly to disassembly, from aerospace to food industry, from textile to logistics) are discussed. Finally, the most recent research is reviewed in order to introduce the new trends in grasping. They provide an outlook on the future of both grippers and robotic hands in automated production processes.     

Thermal conductivity of anisotropic,inhomogeneous high‐density foam calculated from three‐dimensional reconstruction of microtome images

An effective method is developed to predict the thermal conductivity of thick foam insulation on offshore oil and gas pipelines. High‐resolution three‐dimensional (3D) images (212 megavoxels) spanning macroscopic sample volumes (38 × 19 × 4 mm³) are obtained and used to create a 3D geometry of the foam. A gravimetric technique is developed to measure the mass density through the foam thickness and used to verify the 3D geometry. The local anisotropic thermal conductivity through the thickness of the foam is calculated using the finite element method on the 3D geometry and the results are verified against measurements and found to be in good agreement. Results show that thermal conductivity is dependent on morphology. For the highly anisotropic part of the foam where the long axes of the bubbles are oriented parallel to the axial direction of the pipe, the radial thermal conductivity is lowered significantly compared to more isotropic foam. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1020‐1028, 2013     

Barrier and operational risk analysis of hydrocarbon releases (BORA-Release). Part I. Method description

Investigations of major accidents show that technical, human, operational, as well as organisational factors influence the accident sequences. In spite of these facts, quantitative risk analyses of offshore oil and gas production platforms have focused on technical safety systems. This paper presents a method (called BORA-Release) for qualitative and quantitative risk analysis of the platform specific hydrocarbon release frequency. By using BORA-Release it is possible to analyse the effect of safety barriers introduced to prevent hydrocarbon releases, and how platform specific conditions of technical, human, operational, and organisational risk influencing factors influence the barrier performance. BORA-Release comprises the following main steps: (1) development of a basic risk model including release scenarios, (2) modelling the performance of safety barriers, (3) assignment of industry average probabilities/frequencies and risk quantification based on these probabilities/frequencies, (4) development of risk influence diagrams, (5) scoring of risk influencing factors, (6) weighting of risk influencing factors, (7) adjustment of industry average probabilities/frequencies, and (8) recalculation of the risk in order to determine the platform specific risk related to hydrocarbon release. The various steps in BORA-Release are presented and discussed. Part II of the paper presents results from a case study where BORA-Release is applied.     

RDX and HMX with Reduced Sensitivity Towards Shock Initiation–RS‐RDX and RS‐HMX

Reduced Sensitivity RDX (RS‐RDX) has received a lot of attention and interest from the explosive community in the recent years. There are several producers of RS‐RDX, most of them using a direct nitration (Woolwich process) for the RDX synthesis, while Chemring Nobel uses the Bachmann process. The processes for obtaining the RS properties probably differ between the various producers. Chemring Nobel has also developed an HMX quality that shows Reduced Sensitivity (RS‐HMX) of different particle size distributions. The shock sensitivity is at the same level as for RS‐RDX in comparable compositions. Reduced shock sensitivity has been obtained for RS‐RDX and Reduced Sensitivity (RS‐HMX) in both pressable and cast‐cured compositions. By using a pressable composition, it is possible to get the results from a BICT gap test faster than from a cast‐cured composition that has to go through a curing process. Chemring Nobel in cooperation with FFI have performed an extensive accelerated ageing testing of RS‐RDX produced by the Bachmann process. The samples have been aged at 60 and 70 °C and the shock sensitivity tested by two different gap tests. The results demonstrate that the Chemring Nobel RS‐RDX retain the insensitivity towards shock during ageing and show no degradation at all. Accelerated ageing testing of RS‐HMX has also been performed and shows no degradation in the shock sensitivity.     

Reliability Evaluation of Multistate Systems with Multistate Components

This paper presents two efficient algorithms for reliability evaluation of monotone multistate systems with s-independent multistate components. The algorithms are based on the Doulliez & Jamoulle decomposition method. Algorithm 1 requires the minimal paths to be known; Algorithm 2 requires the minimal cuts to be known (the state of the system need not be specified for each vector of component states). Computer programs for implementing the algorithms are given. Computational-times are presented, and compared with the ``Inclusion-Exclusion Method' and the ``State Enumeration Method'. The results demonstrate clearly the superiority of the algorithms to the two other methods.     

Myosin denaturation in pale, soft, and exudative (PSE) porcine muscle tissue as studied by differential scanning calorimetry

Myofibrillar tissue from pale, soft, and exudative (PSE) pork was compared to tissue from normal pork by differential scanning calorimetry at pH 5.4. Thermograms of myofibrillar tissue from normal pork were characterised by three major peaks with temperature maxima at 58 and 66°C, associated with myosin denaturation, and at 78°C, associated with actin denaturation. In thermograms of PSE pork, the peak at 58°C was markedly reduced, and appeared as a shoulder. When the thermograms were divided into segments corresponding to the three major peaks, the area of the low temperature myosin segment was shown to be reduced by about 50% in PSE pork, as compared to normal pork. This indicates approximately 50% denaturation of the least thermostable parts of the myosin molecule. The more thermostable parts of the myosin molecule were largely unaffected, as was actin.     

Inhibition of Bacillus cereus by strains of Lactobacillus and Lactococcus in milk

The growth and death or survival of Bacillus cereus in sterile skimmed milk fermented with 18 different lactic acid bacteria (LAB) were investigated. B. cereus alone in milk reached about 10(7)-10(8) colony-forming units (cfu)/ml. When B. cereus was cultivated together with different Lactobacillus or Lactococcus cultures at 30 or 37 degrees C, the B. cereus counts after 72 h of fermentation ranged between < 10 cfu/ml and about 10(6) cfu/ml. The inhibition patterns for the different Lactobacillus and Lactococcus cultures varied. All the Lactococcus cultures (with one exception) reduced pH to 5.3 or lower in 7 h. After 24 h, B. cereus was not detected in any of the fast Lactococcus-fermented milk samples. After 48 h, B. cereus was not detected for 4 of the 12 Lactobacillus cultures. These cultures reduced pH to below 5.0 in 24 h. The other Lactobacillus cultures also inhibited B. cereus, but the counts of B. cereus were still 10(4)-10(6) cfu/ml after 72 h. They also reduced pH at a slower rate. Survival of B. cereus was to a variable extent linked with formation of endospores. Proteinase K did not affect the antimicrobial activity observed. Acid production with decreasing pH, particularly the initial rate of pH decrease, appears to be most important for control of B. cereus with LAB.     

Propeller blade stresses,application of finite element methods

This paper presents results from application of shell elements for prediction of quasi static and dynamic stresses in marine propeller blades.Stresses and deformations calculated for ordinary geometry and highly scewed propellers are compared with experiments.Specially designed data generators are employed to facilitate the helicoidal geometry involved.