Microbiological analysis of seed sprouts in Norway

As part of larger survey of microbial contamination of fruits and vegetables in Norway, four different sprouted seed products were analysed for bacterial and parasitic contaminants (n = 300 for bacterial analyses and n = from 17 to 171 for parasite analyses, depending on parasite). Escherichia coli O157, Salmonella, Listeria monocytogenes, Cyclospora oocysts, Ascaris eggs and other helminth parasites were not detected in any of the sprout samples. Thermotolerant coliform bacteria (TCB) were isolated from approximately 25% of the sprout samples, with the highest percentage of TCB positive samples in alfalfa sprouts. Most TCB were Enterobacter spp. and Klebsiella. E. coli was isolated from 8 of 62 TCB positive mung bean sprout samples. Cryptosporidium oocysts were detected in 8% of the sprout samples and Giardia cysts were detected in 2% of the samples. All the Cryptosporidium positive samples, and most of the Giardia positive samples, were mung bean sprouts. Parasite concentrations in positive samples were low (between 1 and 3 oocysts/cysts per 50 g sprouts). Sprout irrigation water was also analysed for microbial contaminants. E. coli O157 and L. monocytogenes were not detected. TCB were isolated from approximately 40% of the water samples. Salmonella reading was isolated from three samples of spent irrigation water on 3 consecutive days. Cryptosporidium and Giardia were also isolated from spent irrigation water. Additionally, eight samples of unsprouted mung bean seed were analysed for Cryptosporidium oocysts and Giardia cysts. One or both of these parasites were detected in six of the unsprouted seed samples at concentrations of between 1 and 5 oocysts/cysts per 100 g unsprouted seed. Whilst our results support spent irrigation water as the most suitable matrix for testing for bacteria, unsprouted seed is considered the more useful matrix for analysing for parasite contaminants.     

Phospholipases a(1)

Phospholipase A(1) (PLA(1)) is an enzyme that hydrolyzes phospholipids and produces 2-acyl-lysophospholipids and fatty acids. This lipolytic activity is conserved in a wide range of organisms but is carried out by a diverse set of PLA(1) enzymes. Where their function is known, PLA(1)s have been shown to act as digestive enzymes, possess central roles in membrane maintenance and remodeling, or regulate important cellular mechanisms by the production of various lysophospholipid mediators, such as lysophosphatidylserine and lysophosphatidic acid, which in turn have multiple biological functions.     

Mid-Pliocene sea level and continental ice volume based on coupled benthic Mg/Ca palaeotemperatures and oxygen isotopes

Ostracode magnesium/calcium (Mg/Ca)-based bottom-water temperatures were combined with benthic foraminiferal oxygen isotopes in order to quantify the oxygen isotopic composition of seawater, and estimate continental ice volume and sea-level variability during the Mid-Pliocene warm period, ca 3.3-3.0Ma. Results indicate that, following a low stand of approximately 65m below present at marine isotope stage (MIS) M2 (ca 3.3Ma), sea level generally fluctuated by 20-30m above and below a mean value similar to present-day sea level. In addition to the low-stand event at MIS M2, significant low stands occurred at MIS KM2 (-40 m), G22 (-40m) and G16 (-60m). Six high stands of +10m or more above present day were also observed; four events (+10, +25,+15 and +30 m) from MIS M1 to KM3, a high stand of +15m at MIS K1, and a high stand of +25m at MIS G17. These results indicate that continental ice volume varied significantly during the Mid-Pliocene warm period and that at times there were considerable reductions of Antarctic ice.     

A Stochastic Kinematic Model of Class Averaging in Single-Particle Electron Microscopy

Single-particle electron microscopy is an experimental technique that is used to determine the 3D structure of biological macromolecules and the complexes that they form. In general, image processing techniques and reconstruction algorithms are applied to micrographs, which are two-dimensional (2D) images taken by electron microscopes. Each of these planar images can be thought of as a projection of the macromolecular structure of interest from an a priori unknown direction. A class is defined as a collection of projection images with a high degree of similarity, presumably resulting from taking projections along similar directions. In practice, micrographs are very noisy and those in each class are aligned and averaged in order to reduce the background noise. Errors in the alignment process are inevitable due to noise in the electron micrographs. This error results in blurry averaged images. In this paper, we investigate how blurring parameters are related to the properties of the background noise in the case when the alignment is achieved by matching the mass centers and the principal axes of the experimental images. We observe that the background noise in micrographs can be treated as Gaussian. Using the mean and variance of the background Gaussian noise, we derive equations for the mean and variance of translational and rotational misalignments in the class averaging process. This defines a Gaussian probability density on the Euclidean motion group of the plane. Our formulation is validated by convolving the derived blurring function representing the stochasticity of the image alignments with the underlying noiseless projection and comparing with the original blurry image.     

Optimal load distribution between units in a power plant

This paper presents a strategy for load distribution between the generating units in hydro power plants. The objective is to reach the maximum energy conversion efficiency for a given dispatched power. The developed tool employs a heuristic-based combinatorial optimization technique in conjunction with a set of system variables measurement allowing real-time load sharing. The developed equipment is used to give online energy conversion efficiency from each unit of the power plant. No specific previous information about the efficiency of system components is required. Simulation results of the proposed optimization technique when applied to typical hydro power plant data are presented.     

Effect of gallium focused ion beam milling on preparation of aluminium thin foils

Focussed ion beam milling has greatly extended the utility of the atom probe and transmission electron microscope because it enables sample preparation with a level of dimensional control never before possible. Using focussed ion beam it is possible to extract the samples from desired and very specific locations. The artefacts associated with this sample preparation method must also be fully understood. In this work, issues specifically relevant to the focussed ion beam milling of aluminium alloys are presented. After using the focussed ion beam as a sample preparation technique it is evident that gallium will concentrate in three areas of the sample: on the surface, on grain boundaries and at interphase boundaries. This work also shows that low-energy Ar ion nanomilling is potentially quite effective for removing gallium implantation layers and gallium from the internal surfaces of aluminium thin foils.     

Ti微合金化对22MnB5热成形钢组织和性能的影响

通过热膨胀试验、显微组织分析和硬度测试,分析了冷却速率和Ti元素对两种22MnB5热成形试验钢相变温度、显微组织、析出相以及硬度等的影响,并绘制了CCT曲线。结果表明,当冷却速率低于5 ℃/s时,试验钢的显微组织主要为铁素体和珠光体;冷却速率达到5 ℃/s后开始形成贝氏体;冷却速率达到30 ℃/s时,获得单一马氏体组织。Ti微合金化可降低Ms点,并通过析出Ti(C, N) 相细化奥氏体晶粒,从而获得细小的马氏体板条,产生的析出强化和细晶强化效应提高了试验钢的强度。     

Fluorescence resonance energy transfer and anisotropy reveals both hetero- and homo-energy transfer in the pleckstrin homology-domain and the parathyroid hormone-receptor

We present a method and an apparatus of polarized fluorescence resonance energy transfer (FRET) and anisotropy imaging microscopy done in parallel for improved interpretation of the photophysical interactions. We demonstrate this apparatus to better determine the protein-protein interactions in the pleckstrin homology domain and the conformational changes in the Parathyroid Hormone Receptor, a G-protein coupled receptor, both fused to the cyan and yellow fluorescent proteins for either inter- or intramolecular FRET. In both cases, the expression levels of proteins and also background autofluorescence played a significant role in the depolarization values measured in association with FRET. The system has the sensitivity and low-noise capability of single-fluorophore detection. Using counting procedures from single-molecule methods, control experiments were performed to determine number densities of green fluorescence protein variants CFP and YFP where homo resonance energy transfer can occur. Depolarization values were also determined for flavins, a common molecule of cellular background autofluorescence. From the anisotropy measurements of donor and acceptor, the latter when directly excited or when excited by energy transfer, we find that our instrumentation and method also characterizes crucial effects from homotransfer, polarization specific photobleaching and background molecules.     

面向切削力测量的圆环式测力仪耦合分析

切削力是描述机械加工时切屑去除过程的重要参数,其精确测量是判断加工状态和提高加工系统可靠性的重要基础。为了提高切削力的测量精度,对圆环式测力仪进行了耦合分析。通过分析圆环式测力仪的组成结构,并通过理论分析研究了多个圆环式复合传感结构之间的耦合关系,修正了切削力分力计算公式。此外,根据刚度的计算公式,利用激光位移传感器测得了圆环式测力仪中多个圆环式复合传感结构的刚度。最后,通过试验研究了经过耦合分析后的圆环式测力仪的基本性能,验证了圆环式测力仪的耦合分析有助于提高切削力的测量精度。     

Understanding the influence of suspended solids on water quality and aquatic biota

Over the last 50 years the effects of suspended solids (SS) on fish and aquatic life have been studied intensively throughout the world. It is now accepted that SS are an extremely important cause of water quality deterioration leading to aesthetic issues, higher costs of water treatment, a decline in the fisheries resource, and serious ecological degradation of aquatic environments. As such, government-led environmental bodies have set recommended water quality guidelines for concentrations of SS in freshwater systems. However, these reference values are often spurious or based on the concept of turbidity as a surrogate measure of the concentration of SS. The appropriateness of these recommended water quality values is evaluated given: (1) the large variability and uncertainty in data available from research describing the effects of SS on aquatic environments, (2) the diversity of environments that these values are expected to relate to, and (3) the range of conditions experienced within these environments. Furthermore, we suggest that reliance solely upon turbidity data as a surrogate for SS must be treated with caution, as turbidity readings respond to factors other than just concentrations of SS, as well as being influenced by the particle-size distribution and shape of SS particles. In addition, turbidity is a measure of only one of the many detrimental effects, reviewed in this paper, which high levels of SS can have in waterbodies. In order to improve the understanding of the effects of SS on aquatic organisms, this review suggests that: First, high-resolution turbidity monitoring should be supplemented with direct, measurements of SS (albeit at lower resolution due to resource issues). This would allow the turbidity record to be checked and calibrated against SS, effectively building a rating-relationship between SS and turbidity, which would in-turn provide a clearer picture of the exact magnitude of the SS problem. Second, SS should also be characterised in terms of their particle-size distribution and chemical composition. This would provide information to develop a more comprehensive understanding of the observed variable effects of a given concentration of SS in aquatic habitats. These two suggested improvements, combined with lower-resolution concurrent measures of aquatic ecological status, would improve our understanding of the effects of SS in aquatic environments and together with a more detailed classification of aquatic environments, would provide an environment-specific evidence base for the establishment of effective water quality guidelines for SS.