不同血清浓度培养条件对博尔纳病病毒感染滴度的影响比较

目的：探讨不同血清浓度对博尔纳病病毒（BDV）感染少突胶质细胞（OL细胞）感染力的影响,寻找BDV病毒感染细胞最适宜的血清浓度。方法：接种BDV的OL细胞（OL/BDV）于培养皿中,培养24小时后,通过反复冻融、超声破碎的方法获取BDV病毒液,用于感染正常的OL细胞。在保证除血清浓度因素不同而其余因素均相同的条件下,用DMEM、2%FCS、5%FCS、10%FCS四种不同浓度的血清培养基在96孔板中培养BDV新感染的OL细胞,测定病毒感染滴度,比较各组之间是否有统计学差异。结果：DMEM、5%FCS和10%FCS组所测得的BDV病毒滴度两组之间无统计学差异,2%FCS组所测得的病毒滴度和DMEM、5%FCS、0%FCS组之间有明显统计学差异,2%FCS组病毒滴度明显高于其它两组。结论：不同浓度的血清浓度对Boma病毒对细胞的感染力有影响,2%FCS的培养条件可能更适合于BDV感染OL细胞实验。     

Effect of axial conduction on the ice crystal growth in laminar falling filmsEffet de la conduction axiale sur la vitesse de formation de cristaux de glace à l'intérieur de films tombants laminaires

A finite volume numerical code has been developed to numerically approximate the rate of ice crystal growth in a laminar falling film flowing down a cooled vertical plate. The governing energy equation contains the phase energy as the source term. Enhancement of heat transfer as a result of suspended ice crystals is accounted for in the use of effective values of thermal conductivity, viscosity, thermal diffusivity, and specific heat as function of volumetric concentration of ice crystals in the falling film. Nusselt number, overall heat transfer coefficients between the fluid and cooled plate, and ice crystal growth rate were calculated for different film thicknesses with and without axial diffusion. Nusselt number and ice crystal growth rates were found to be dependent on film thickness. Axial diffusion effects were found to be negligible for larger film thickness (large flowrate).     

纤维镍基板的化学浸渍过程

本文利用真空和静态浸渍相结合的方法,研究了新型纤维镍基板化学浸渍过程若干参数对浸渍增重的影响;对化学浸渍过程,推导出活性物质填充量及镍基板活性物质载量水平与浸渍次数关系的数学表达式,并将实验结果与理论曲线进行了比较分析。     

Two-dimensional mathematical model of a reciprocating room-temperature Active Magnetic Regenerator

A time-dependent, two-dimensional mathematical model of a reciprocating Active Magnetic Regenerator (AMR) operating at room-temperature has been developed. The model geometry comprises a regenerator made of parallel plates separated by channels of a heat transfer fluid and a hot as well as a cold heat exchanger. The model simulates the different steps of the AMR refrigeration cycle and evaluates the performance in terms of refrigeration capacity and temperature span between the two heat exchangers. The model was used to perform an analysis of an AMR with a regenerator made of gadolinium and water as the heat transfer fluid. The results show that the AMR is able to obtain a no-load temperature span of 10.9 K in a 1 T magnetic field with a corresponding work input of 93.0 kJ m⁻³ of gadolinium per cycle. The model shows significant temperature differences between the regenerator and the heat transfer fluid during the AMR cycle. This indicates that it is necessary to use two-dimensional models when a parallel-plate regenerator geometry is used.     

Mixed plaques: statistical evidence how plaque assays may underestimate virus concentrations

Even at very low concentrations human pathogenic viruses may result in infection and possibly subsequent disease. Ideally, viruses are quantified by use of cell culture assays to determine their infectivity. Plaque assays are common tools for enumeration of viruses in inocula and this process is straightforward when a plaque results from the offspring of a single infectious virus particle. In the course of a study on the usefulness of sewage monitoring for surveillance of polio-virus transmission, sewage samples containing a mixture of two live polio vaccine strains (type 1 and type 3) were analyzed. The total poliovirus concentration in plaque forming units (pfu) was estimated by means of a monolayer plaque assay on L20B cells. Subsequent typing of virus directly by neutralisation of virus from excised plaques revealed the occurrence of plaques containing both type 1 and type 3 virus. This means that there must be plaques that originate from more than one initial infectious virus particle. As a consequence, the estimated virus concentration is incorrect. We present statistical methods that utilize these mixed plaque counts to estimate the concentrations of either virus type in our sewage samples. We can also calculate a correction factor for the error in virus concentration, which would result from equating a pfu to a single infectious particle. Since many quantitative methods in microbiology are based on colony counts, we conclude that such counts should be interpreted with caution, especially when data are used in quantitative microbial risk assessment to estimate the public health impact.     

表皮生长因子对脊髓灰质炎病毒增殖的影响

在细胞培养维持液中,加入人表皮生长因子(h-EGF),观察在不同温度下、不同浓度EGF 对脊髓灰质炎病毒生长繁殖的情况。结果发现,维持液中加含10～100ng/ml EGF,能获得最高感染滴度,高于100ng/ml 则有所下降,5ng/ml 时与对照组无差别。在36℃培养的滴度高于33℃,病毒滴度变化与温度呈平行关系。所培养的子代病毒,可被抗脊髓灰质炎Ⅰ型血清中和。10ng～100ng/ml 浓度的 EGF 对细胞不产生毒性作用。     

Automatic plaque segmentation based on hybrid fuzzy clustering and k nearest neighborhood using virtual histology intravascular ultrasound images

Thin cap fibroatheroma (TCFA) or “vulnerable plaque” is responsible for the majority of coronary artery death. Virtual Histology Intravascular Ultrasound (VH-IVUS) image is a clinically available method for visualizing color coded tissue maps. However, this technique has considerable limitations in providing medical relevant information for identifying vulnerable plaque. The aim of this paper is to improve the identification of TCFA in VH-IVUS image. Therefore, this paper proposes a set of algorithms for segmentation, feature extraction, and plaque type classification to accurately identify TCFA. A hybrid model using the FCM and kNN (HFCM-kNN) is proposed to accurately segment the VH-IVUS image. The proposed technique is capable of eliminating outliers and detecting clusters with different densities in VH-IVUS image. The next process is extracting plaque features to provide an accurate definition of the unstable (vulnerable) plaque. To achieve the above contribution, five algorithms are proposed to extract significant features from VH-IVUS images. Machine learning approaches are applied for training 440 in-vivo images obtained from 8 patients. Results proved the dominance of the proposed method for TCFA detection with accuracy rate of 98.02% compared with the 76.5% obtained by the cardiologist decision. Moreover, by validation of VH-IVUS images and their corresponding Optical Coherence Tomography (OCT) images, accuracy of 92.85% is achieved.     

不同补料工艺对林可霉素发酵的影响

研究补料工艺对林可霉素发酵生产的作用,考察在不同时间1次和2次补加小料对菌体形态和发酵效价的影响。结果显示：发酵过程中补糖和补硫酸铵可提高林可霉素发酵的效价,在此基础上分批增补小料对林可霉素发酵效价的增加效果更好,其中2次补小料的最优时间分别在发酵48 h和96 h。进行2次补小料的林可霉素发酵效价达到7.421 g/L,比不补小料和补1次小料林的林可霉素发酵效价分别提高192.7%和135.4%。     

Characteristics on host specificity,infection, and temperature stability of Weissella phages from watery kimchi

Three bacteriophages (phage), ΦWC53, ΦWC54, and ΦWC56, of Weissella were isolated from watery kimchi and characterized. ΦWC53 belonged to Siphoviridae and ΦWC54 and ΦWC56 belonged to Myoviridae family. By one-step growth, the burst sizes were 5–260 particles/infected cells and the latent periods were 20–45 min. The phages infected Weissella spp., Leuconostoc mesenteroides, and Lactobacillus spp., differently by showing clear or turbid plaques. The phage adsorption rates on lactic acid bacteria were high on Weissella and low on Leuconostoc and Lactobacillus. However, the adsorption of ΦWC53 occurred variously among Weissella spp. and Weissella host grew well in the liquid culture without lysis after challenging by ΦWC53. Tolerances of these phages to temperature showed more various than those to pH. ΦWC53 was stable at 7 °C and 30 °C, but ΦWC54 and ΦWC56 were stable only at 7 °C. Therefore, three Weissella phages belonged to the different families and indicated diverse infection patterns on Weissella, Leuconostoc, and Lactobacillus with various stabilities for pH and temperature.

     

基于斑块理论的哈尔滨老城区历史绿地解析

文章借助景观生态学中的斑块理论,对哈尔滨老城区历史绿地的演化、分布、尺度、类型等方面进行了研究,探讨并剖析了历史老城区斑块状绿地的发展过程、作用及其保护价值。