钛石膏的性能研究

钛石膏为硫酸法钛白生产过程中的副产品,钛石膏大量堆积对环境造成污染,研究钛石膏的性能特点,对于选择合理的回收利用方案具有重要的指导意义。主要对钛石膏的物相组成、脱水温度、脱水时间和凝结特点进行试验研究。结果表明:钛石膏的主要物相为二水硫酸钙,少量物相为白云石,钛石膏脱除结晶水温度控制在200℃左右,脱除结晶水时间控制在50 min左右较适宜。添加柠檬酸作缓凝剂时,煅烧温度从120℃提高到200℃,钛石膏的凝结时间从1 800 s缩短为1 000 s,可以满足浇注成型的时间要求。     

Coagulation of turbid water and softening of hardwater with Moringa oleifera seeds

In this study, the effects of 5 process variables on softening hardwater and coagulation of surface water with a M. oleifera seed extract were investigated. Multiple regression analysis showed a strong correlation (R² (adj.) = 0.99 between M. oleifera seed dosage and the initial hardness of synthetic hardwater. Since M. oleifera is known to be a polyelectrolyte, the softening mechanism is likely to be adsorption. An adsorption isotherm developed was approximately linear and conformed to the Langmuir type. For the coagulation studies, the water samples were from three rivers in Kano, Nigeria over a three month period during the rainy season (June‐August 1994). The turbidity of the water sample varied from 105–350 NTU. When used as primary coagulant, M. oleifera was able to achieve up to 99% turbidity removal for two of the water samples at the optimum dosage of 250 mg/l. For the third water sample, the optimum dosage was 450 mg/l which is assumed to be due the high value of the colour of the water. Saving in alum usage of up to 40% was achievable when M. oleifera was used in conjunction with alum.     

Newly identified mutations at the CSN1S1 gene in Ethiopian goats affect casein content and coagulation properties of their milk

Very high casein content and good coagulation properties previously observed in some Ethiopian goat breeds led to investigating the α_s1-casein (CSN1S1) gene in these breeds. Selected regions of the CSN1S1 gene were sequenced in 115 goats from 5 breeds (2 indigenous: Arsi-Bale and Somali, 1 exotic: Boer, and 2 crossbreeds: Boer × Arsi-Bale and Boer × Somali). The DNA analysis resulted in 35 new mutations: 3 in exons, 3 in the 5′ untranslated region (UTR), and 29 in the introns. The mutations in exons that resulted in an amino acid shift were then picked to evaluate their influence on individual casein content (α_s1-, α_s2-, β-, and κ-CN), micellar size, and coagulation properties in the milk from the 5 goat breeds. A mutation at nucleotide 10657 (exon 10) involved a transversion: CAG→CCG, resulting in an amino acid exchange Gln₇₇→Pro_77. This mutation was associated with the indigenous breeds only. Two new mutations, at nucleotide 6072 (exon 4) and 12165 (exon 12), revealed synonymous transitions: GTC→GTT in Val₁₅ and AGA→AGG in Arg₁₀₀ of the mature protein. Transitions G→A and C→T at nucleotides 1374 and 1866, respectively, occurred in the 5′ UTR, whereas the third mutation involved a transversion T→G at nucleotide location 1592. The goats were grouped into homozygote new (CC), homozygote reference (AA), and heterozygote (CA) based on the nucleotide that involved the transversion. The content of α_s1-CN (15.32 g/kg) in milk samples of goats homozygous (CC) for this newly identified mutation, Gln₇₇→Pro₇₇ was significantly higher than in milks of heterozygous (CA; 9.05 g/kg) and reference (AA; 7.61 g/kg) genotype animals. The α_s2-, β-, and κ-CN contents showed a similar pattern. Milk from goats with a homozygous new mutation had significantly lower micellar size. Milk from both homozygote and heterozygote new-mutation goats had significantly shorter coagulation rate and stronger gel than the reference genotype. Except the transversion, the sequence corresponded to allele A and presumably derived from it. Therefore, this allele is denoted by A₃. All goats from the reference genotype (AA) were homozygous for the allele at nucleotide position 1374 and 1866, whereas all mutations in the 5′ UTR existed in a heterozygous form in both heterozygous (CA) and the new mutation (CC) genotype. The newly identified mutation (CC) detected in some of the goat breeds is, therefore, important in selection for genetic improvement and high-quality milk for the emerging goat cheese-producing industries. The finding will also benefit farmers raising these goat breeds due to the increased selling price of goats. Further studies should investigate the effect of this amino acid exchange on the secondary and tertiary structure of the α_s1-CN molecule and on the susceptibility of peptide hydrolysis by digestive enzymes.     

卤水对碱性印染废水脱色处理的初步研究

采用含镁量高的废弃卤水处理碱性印染废水。考察了pH值、卤水投加量、温度、沉降时间对脱色率的影响。实验表明:废水的脱色率主要受pH值、卤水投加量的影响,温度也有一定的影响。pH11时脱色率可达98%以上。利用废弃的卤水对印染废水进行脱色处理具有实际应用前景。     

Associations between pathogen-specific cases of subclinical mastitis and milk yield,quality, protein composition,and cheese-making traits in dairy cows

The aim of this study was to investigate associations between pathogen-specific cases of subclinical mastitis and milk yield, quality, protein composition, and cheese-making traits. Forty-one multibreed herds were selected for the study, and composite milk samples were collected from 1,508 cows belonging to 3 specialized dairy breeds (Holstein Friesian, Brown Swiss, and Jersey) and 3 dual-purpose breeds of Alpine origin (Simmental, Rendena, and Grey Alpine). Milk composition [i.e., fat, protein, casein, lactose, pH, urea, and somatic cell count (SCC)] was analyzed, and separation of protein fractions was performed by reversed-phase high performance liquid chromatography. Eleven coagulation traits were measured: 5 traditional milk coagulation properties [time from rennet addition to milk gelation (RCT, min), curd-firming rate as the time to a curd firmness (CF) of 20 mm (k₂₀, min), and CF at 30, 45, and 60 min from rennet addition (a₃₀, a₄₅, and a₆₀, mm)], and 6 new curd firming and syneresis traits [potential asymptotical CF at an infinite time (CF_P, mm), curd-firming instant rate constant (k_CF, % × min^?1), curd syneresis instant rate constant (k_SR, % × min^?1), modeled RCT (RCT_eq, min), maximum CF value (CF_max, mm), and time at CF_max (t_max, min)]. We also measured 3 cheese yield traits, expressing the weights of total fresh curd (%CY_CURD), dry matter (%CY_SOLIDS), and water (%CY_WATER) in the curd as percentages of the weight of the processed milk, and 4 nutrient recovery traits (REC_PROTEIN, REC_FAT, REC_SOLIDS, and REC_ENERGY), representing the percentage ratio between each nutrient in the curd and milk. Milk samples with SCC > 100,000 cells/mL were subjected to bacteriological examination. All samples were divided into 7 clusters of udder health (UH) status: healthy (cows with milk SCC < 100,000 cells/mL and uncultured); culture-negative samples with low, medium, or high SCC; and culture-positive samples divided into contagious, environmental, and opportunistic intramammary infection (IMI). Data were analyzed using a linear mixed model. Significant variations in the casein to protein ratio and lactose content were observed in all culture-positive samples and in culture-negative samples with medium to high SCC compared to normal milk. No differences were observed among contagious, environmental, and opportunistic pathogens, suggesting an effect of inflammation rather than infection. The greatest impairment in milk quantity and composition, clotting ability, and cheese production was observed in the 2 UH status groups with the highest milk SCC (i.e., contagious IMI and culture-negative samples with high SCC), revealing a discrepancy between the bacteriological results and inflammatory status, and thus confirming the importance of SCC as an indicator of udder health and milk quality.     

我国给水净化新技术的开发与应用

主要介绍80年代以来我国常规给水净化方面的新理论和新工艺,及其开发应用情况。     

高残渣钻井废水的处理方法探讨

为解决用混凝法处理高残渣钻井废水效果较差这一问题,本文根据实验总结出混凝剂的投加量与钻井废水的总残渣量之间的关系,提出了改善高残渣钻井废水处理效果的方法—稀释法和分级混凝法。     

草浆废水混凝脱色的研究

本文通过草浆废水的混凝试验提出了石灰对草浆废水的混凝机理,并得出草浆废水首先经厌氧预处理可显著地提高其混凝效果并可节省投药量这一具有较大实用价值的结论.     

UHT乳贮存中常见问题及其原因分析

UHT乳作为“营养全价”食品倍受消费者喜爱。但是UHT乳在贮藏中容易出现一些质量问题,常见的有：脂肪上浮、形成沉淀和凝胶、乳清析出、酸包和胀包及色香味的改变等。针对以上问题进行了论述,并探讨了产生的原因及相应的预防措施。     

琥珀山庄居住小区污水处理工艺试验研究

进水 COD、油脂浓度过高 ,使小区污水处理厂难以正常运行 ,造成出水浑浊 ,不能达标排放。混凝沉淀试验证实 ,聚铝对 COD、油脂的去除率比聚铁高 ,在加药量达到 5 0 mg/ L时差异最为明显 ;水解酸化试验表明 ,水解酸化达到 2 h时 ,COD、油脂降解效果显著。采用物化法 ,可选用涡凹气浮工艺 ;采用生物法 ,可选用优点突出的水解酸化工艺。