Viability of bifidobacteria in commercial yogurt products in North Carolina during refrigerated storage

Fifty-eight commercial yogurt products of seven brands (which claimed to include bifidobacteria) were obtained from local stores in Greensboro, North Carolina, USA. These products were examined at 0, 1, 2, 3 and 4 weeks for the viability of bifidobacteria and yogurt starter culture during refrigerated storage at 4°C. Our results showed that bifidobacteria counts were variable, ranging from 0 to 5.5 log cfu/mL. The average yogurt starter culture counts ranged from 5.20 to 8.87 log cfu/mL and 7.51–8.94 log cfu/mL for Lactobacillus delbrueckii spp. bulgaricus and Streptococcus thermophilus , respectively. Of the 58 products tested, only 44 products (76%) contained viable cultures. Viability of bifidobacteria in yogurt samples remained within the same levels during 3 weeks of storage at 4°C; however, the bacterial count started to decline during the fourth week. These results suggest optimal beneficial consumption of yogurt foods with live bifidobacteria should occur within 3 weeks of production. Results obtained from this research could be used by the industry to develop new technologies to ensure consumers receive high-quality products.     

EFFECTS OF SODIUM LACTATE, SODIUM ACETATE AND SODIUM DIACETATE ON MICROBIOLOGICAL QUALITY OF VACUUM-PACKED BEEF DURING REFRIGERATED STORAGE

Beef samples were cut into the pieces and treated with solutions of 1.8 and 2.5% sodium lactate (SL), 0.1% sodium acetate (SA), 0.1 and 0.2% sodium diacetate (SDA) and their combinations, packed under vacuum and stored in a refrigerator at 4C. Microbiological quality of the samples was investigated during their storage for 21 days. Sodium salts and their combinations significantly (P < 0.05) affected the aerobic plate count (APC). Although growth of lactic acid bacteria (LAB), psychrotrophs and coliforms was delayed in treated samples, they were not completely inhibited. The most effective treatment to delay the growth of microorganisms was the combination of 2.5% SL + 0.2% SDA. The count of bacteria of the samples reached and exceeded the spoilage limit (10⁷?10⁸log cfu/g) after 14 days at 4C.     

基于SVM的维吾尔文文本分类研究

文本自动分类技术在提高文本信息利用的有效性和准确性上具有重要的现实意义和广阔的应用前景。随着Internet上维吾尔文信息的迅速发展,维吾尔文文本分类成为处理和组织这些大量文本数据的关键技术。研究维吾尔文文本分类相关技术和方法,针对维吾尔文文本在向量空间模型表示下的高维性,本文采用词干提取和χ2统计量相结合的方法对表示空间进行降维。采用SVM算法构造了维吾尔文文本分类器。针对维吾尔文文本分类语料进行的实验结果表明,SVM分类器的MacroF1值达到了84.6%,明显好于kNN方法。     

Al掺杂锰酸锂材料在水系锂离子电池中的循环稳定性

水系锂离子电池具有优良的安全性能和高离子导电性等优点,得到了广泛研究.LiMn2O4材料在水系锂离子电池中较差的循环稳定性使其应用受到限制.为了改善这一缺陷,以乙炔黑为模板,采用简单的高温固相法合成了Al掺杂的LiMn2O4材料(LiMn1.9Al0.1O4),并应用于水系锂离子全电池中.实验结果表明,在0.1 A/g的电流密度下,LiMn2O4材料放电比容量高达125.5 mA·h/g,略高于LiMn1.9Al0.1O4材料的比容量(121.6 mA·h/g).在0.1 A/g电流密度下,经200次循环LiMn1.9Al0.1O4材料的容量保持率(90％)高于LiMn2O4材料(78％).将电流密度提升到1 A/g经500次循环后LiMn1.9Al0.1O4和LiMn2O4材料的容量保持率分别为88％和57％.上述结果表明Al掺杂的锰酸锂材料在水系锂离子电池中的循环稳定性以及倍率性能均有明显提高,说明Al的掺杂能显著提升锰酸锂正极材料的结构稳定性,并且能够缓解Mn的溶解和抑制Jahn-Teller效应,改善循环性能.     

大数据时代勘探云建设模式探索

按照大数据定义,油气勘探数据处理工作显然是一种大数据应用模式,而作为油气勘探核心工作平台的勘探云计算中心,其建设目的首先是为了满足企业内部业务数据处理工作需求,在确保计算力分享和协同工作的基础上,勘探云更注重数据存储、数据管理以及数据应用业务的支持,对照一般公用云建设模式,勘探私有云建设具备其独特的建设模式。笔者企业结合自身特点,对照当前大数据应用需求开展勘探私有云建设工作,取得了一定的效果,对企业主营业务的支持效果明显。     

融合奇异性和扩散过程的协同过滤模型

作为解决信息过载问题的有效方式,推荐系统能够根据用户偏好对海量信息进行过滤,为用户提供个性化的推荐。但在推荐过程中,性能表现优异的协同过滤模型并没有充分利用上下文信息,这在一定程度上使系统面临性能瓶颈。为了进一步提高系统性能,从评分上下文信息着手,通过对项目评分进行分类统计获得评分奇异性,同时借鉴多渠道扩散相似性模型将推荐系统作为用户-项目二分网络的思想,提出了融合奇异性和扩散过程的协同过滤模型(collaborative filtering model fusing singularity and diffusion process,简称CFSDP)。为了表明模型的优越性,比较实验基于MovieLens,NetFlix和Jester这3个不同的数据集展开。实验结果表明,该模型不仅具有良好的扩展性,而且在合理的时间开销下,可以显著提高系统的预测和推荐质量。     

石河子地区酿酒葡萄成熟度与葡萄酒质量的研究

研究结果表明,石河子地区梅鹿辄、霞多丽葡萄含糖量的变化符合"S"型曲线,而它们的含酸量从8月1日起处于下降趋势.在石河子的生态条件下,梅鹿辄葡萄糖酸比在30-40之间,霞多丽的糖酸此在28～37之间,所酿的葡萄酒质量最好.本文还探讨了确定葡萄成熟度其它的方法,如糖×pH值、糖×(pH值)2.     

MODELING the AVERAGE SHEAR RATE IN A CO-ROTATING TWIN SCREW EXTRUDER

A procedure similar to the one commonly used with mixers has been utilized to develop a model for estimating the shear rate in co-rotating twin screw extruders. Newtonian and non-Newtonian fluids were used to estimate the average shear rate for three screw configurations of a Baker Perkins (MPF-50D) twin screw extruder. As would be expected, the shear rate was highly correlated to the screw speed. At a given screw speed, 30 forwarding paddles generate the highest rate of shear, followed by feed screws and single lead screws. No data was found in the published literature to provide comparison with the results of this work. However, the model has performed well in heat transfer analysis of twin screw processes. The procedure is sensitive to screw configuration, accounts for the shearing effects in the different regions within the extruder barrel, and covers a range of screw speeds (100–400 RPM) typical of what is encountered in industrial pilot plants. Even though much more work remains to be done before the shear rate can be confidently characterized for composite screw configurations, this technique provides a sound foundation.     

过渡金属氧化物LaFe1-xCrxO3体系的晶体结构和光电子能谱研究

我们在端点化合物LaFeO3中掺入Cr^3 ，制备了LaFe1-xCrxO3体系的系列样品。经XRD分析证明所制备的样品为单相体系，用MarqX程序对XRD数据进行分析得到其晶格常数。分别测定了入射光子能量在Fe2p吸收边以下和以上的O1s芯能级谱。从电子结构角度探讨了该体系晶体结构变化趋势。初步得出结论：随着Cr^3 掺杂量在LaFe1-xCrxO3中的增加，O2p向Cr 3d的电荷转移量也发生有规律的变化。