Electrical conductivity of milk: ability to predict mastitis status

Electrical conductivity (EC) of milk has been introduced as an indicator trait for mastitis over the last decade, and it may be considered as a potential trait in a breeding program where selection for improved udder health is included. In this study, various EC traits were investigated for their association with udder health. In total, 322 cows with 549 lactations were included in the study. Cows were classified as healthy or clinically or subclinically infected, and EC was measured repeatedly during milking on each quarter. Four EC traits were defined; the inter-quarter ratio (IQR) between the highest and lowest quarter EC values, the maximum EC level for a cow, IQR between the highest and lowest quarter EC variation, and the maximum EC variation for a cow. Values for the traits were calculated for every milking throughout the entire lactation. All EC traits increased significantly (P < 0.001) when cows were subclinically or clinically infected. A simple threshold test and discriminant function analysis was used to validate the ability of the EC traits to distinguish between cows in different health groups. Traits reflecting the level rather than variation of EC, and in particular the IQR, performed best to classify cows correctly. By using this trait, 80.6% of clinical and 45.0% of subclinical cases were classified correctly. Of the cows classified as healthy, 74.8% were classified correctly. However, some extra information about udder health status was obtained when a combination of EC traits was used.     

Effects of carbon dioxide on bacterial growth parameters in milk as measured by conductivity

Inhibition of bacterial growth by dissolved carbon dioxide (CO2) has been well established in many foods including dairy foods. However, the effects of dissolved CO2 on specific growth parameters such as length of lag phase, time to maximum growth rate, and numbers of organisms at the stationary phase have not been quantified for organisms of concern in milk. The effect of dissolved CO2 concentrations of 0.6 to 61.4 mM on specific bacterial growth parameters in raw or single organism inoculated sterile milk was determined at 15 degrees C by conductance. Commingled raw or sterile milks were amended to a final concentration of 0.5 mg/ml each of urea and arginine HCl. Sterile milks were inoculated singly with one of six different microorganisms to a final concentration of approximately 10(2) to 10(3) cfu/ml; raw milk was adjusted to a final indigenous bacterial population of approximately 10(3) cfu/ml. Conductivity of the milk was recorded every 60 s over 4 to 5 d in a circulating apparatus at 15 degrees C. Conductivity values were fit to Gompertz equations and growth parameters calculated. Conductance correlated with plate counts and was satisfactory for monitoring microbial growth. Data fit the Gompertz equation with high correlation (R2 = 0.96 to 1.00). In all cases, dissolved CO2 significantly inhibited growth of raw milk bacteria, influencing lag, exponential, and stationary growth phases as well as all tested monocultures.     

人居环境“阅读”——北京四合院居住文化

四合院建筑文化作为中华民族的特征之一,具有十分悠久的历史渊源,早在辽代就已经出现了,它不仅反映了中华民族的居住文化,也体现了一种“天然合一”的人文关系,本文就北京的四合院为例,浅析了它的历史背景和文化内涵。     

《数据库系统原理》课程教学方法研究

从分析研究教材、注重学科联系出发,提出了概念教学的重要性,探讨了课程设计在数据库系统原理课程中的重要地位。     

A novel key agreement protocol based on chaotic maps

Based on the semi-group property of Chebyshev chaotic map and some effective improvements of our original protocol, we propose a novel chaotic maps-based key agreement protocol which is proved to be secure, feasible and extensible.     

基于ROI分割和相干映射的裸手字母手势识别

提出了实时条件下裸手单目的手部定位和跟踪算法。结合改进的差分法提出了实用的手部约束条件，从每帧图像中提取手部图像，确定感兴趣区域（ROI，region of interesting），得到较为满意的手部分割结果，再对手部图像特征进行深入分析和提取，利用改进的相干映射算法（VCM，vector coherence mapping）进行跟踪，针对手的运动增加了约束，保证了顽健性。在这个基础上，提出了时间相关的运动预测模型，满足了实时性的要求，保证前后分析结果的一致性。实验结果证明，在不同光照和复杂背景下系统有最高达99％的识别率，与已有的系统相比，性能显著提高。     

To ask, or not to ask, about abuse--New Zealand research.

Comments on the article by K. Becker-Blease and J. Freyd (see record 2006-03947-003), which addressed the ethics of asking and not asking research subjects about abuse. J. Read reviews some clinical research in New Zealand in which there was a low level of inquiry about abuse by mental health staff, and notes that this is consistent with the results of similar studies elsewhere. He agrees with Becker-Blease and Freyd that there are many consequences to researchers and clinicians of not asking. (PsycINFO Database Record (c) 2010 APA, all rights reserved)