K2B4O7-Li2B4O7-MgB4O7-H2O四元体系288 K相平衡研究

采用等温溶解平衡法研究了288 K时K2B4O7-L i2B4O7-MgB4O7-H2O四元体系的相平衡关系,测定了平衡液相的等温溶解度和密度。研究发现:该体系属于简单共饱和体系,无复盐和固溶体生成;该四元体系288 K时的等温溶解度图存在三个固相结晶区,其平衡固相分别为:L i2B4O7.3H2O,K2B4O7.4H2O和MgB4O7.9H2O;一个共饱点E,三条单变量曲线E1-E,E2-E,E3-E;文章最后对实验结果进行了简单讨论。     

K_2B_4O_7-Li_2B_4O_7-MgB_4O_7-H_2O四元体系288K相平衡研究

采用等温溶解平衡法研究了288 K时K2B4O7-L i2B4O7-MgB4O7-H2O四元体系的相平衡关系,测定了平衡液相的等温溶解度和密度。研究发现:该体系属于简单共饱和体系,无复盐和固溶体生成;该四元体系288 K时的等温溶解度图存在三个固相结晶区,其平衡固相分别为:L i2B4O7.3H2O,K2B4O7.4H2O和MgB4O7.9H2O;一个共饱点E,三条单变量曲线E1-E,E2-E,E3-E;文章最后对实验结果进行了简单讨论。     

298K时Na2SO4-Na2B4O7-Na2CO3-H2O四元体系相平衡研究

采用等温溶解平衡法研究了298K时Na2SO4-Na2B4O7-Na2CO3-H2O四元体系的相平衡关系,测定了平衡液相的等温溶解度和主要物化性质(密度、电导率、pH值).研究发现:该体系属于简单共饱和体系,无复盐和固溶体生成;该四元体系298K时的等温溶解度图存在三个固相结晶区,其平衡固相分别为:Na2SO4·10H2O,Na2B4O7·10H2O,Na2CO3·10H2O;一个共饱点E,三条单变量曲线E1-E, E2-E, E3-E;文章最后对实验结果进行了简单讨论.     

K2B4O7-K2SO4-KCl-H2O四元体系288K相平衡研究

采用等温溶解平衡法研究了四元体系K2B4O7-K2SO4-KCl-H2O在288K的相平衡及平衡液相,测定了平衡液相的溶解度及密度。研究结果表明该四元体系为简单共饱和型,无复盐及固溶体形成。根据实验数据绘制了相应的相图。相图中有一个共饱点E,三条单变曲线E1E,E2E和E3E4三个结晶区平衡固相分别为：K2B4O7·4H20,K2SO4和KCl。实验结果表明KCl对K2B4O7·4H2O和K2SO4有盐析作用,并简要讨论了密度变化规律。     

K2B4O7-K2SO4-KCl-H2O四元体系288 K相平衡研究

采用等温溶解平衡法研究了四元体系K2B4O7-K2SO4-KCl-H2O在288 K的相平衡及平衡液相,测定了平衡液相的溶解度及密度.研究结果表明该四元体系为简单共饱和型,无复盐及固溶体形成.根据实验数据绘制了相应的相图.相图中有一个共饱点E,三条单变曲线E1E,E2E和E3E;三个结晶区平衡固相分别为:K2B4O7·4H2O,K2SO4和KCl.实验结果表明KCl对K2B4O7·4H2O和K2SO4有盐析作用,并简要讨论了密度变化规律.     

288K 时四元体系 Na+,K+ //Cl-,B4O2-7-H2O相平衡研究

采用等温溶解平衡法研究了288 K时Na+,K+//Cl-,B4O72--H2O四元体系的相平衡关系,测定了平衡液相的溶解度和密度。依据实验测定的平衡溶解度数据及对应的平衡固相,绘制了该四元体系的平衡相图及其密度-组成图。研究结果表明:四元体系Na+,K+//Cl-,B4O27--H2O 288 K时的固液相平衡实验中,平衡相图中有2个共饱点,5条单变量曲线,4个结晶区,其平衡固相分别为:Na2B4O7.10H2O,K2B4O7.4H2O,NaCl和KCl;并对实验结果进行了简要讨论。     

288K时四元体系Na~＋,K~＋//Cl~-,B_4O_7~（2-）-H_2O相平衡研究

采用等温溶解平衡法研究了288 K时Na＋,K＋//Cl-,B4O72--H2O四元体系的相平衡关系,测定了平衡液相的溶解度和密度。依据实验测定的平衡溶解度数据及对应的平衡固相,绘制了该四元体系的平衡相图及其密度-组成图。研究结果表明：四元体系Na＋,K＋//Cl-,B4O27--H2O 288 K时的固液相平衡实验中,平衡相图中有2个共饱点,5条单变量曲线,4个结晶区,其平衡固相分别为：Na2B4O7.10H2O,K2B4O7.4H2O,NaCl和KCl;并对实验结果进行了简要讨论。     

Na2B4O7-K2B4O7-H2O三元体系288K相平衡研究

采用等温溶解平衡法研究了三元体系Na2 B4O7—K2 B4O7—H2 O 2 88K时的相平衡及平衡液相的主要物化性质 (密度、电导率 ,pH)。研究发现 ,该三元体系为简单共饱和型 ,无复盐及固溶体形成 ,根据溶解度数据绘制了相图 ,相图中单变量曲线所对应的平衡固相分别为 :K2 B4O7·4H2 O ,Na2 B4O7·10H2 O ;实验结果表明 :K2 B4O7对Na2 B4O7有增溶作用 ,并简要讨论了物化性质的变化规律     

Na2CO3-Na2B4O7-H2O三元体系273K相平衡实验研究

采用等温蒸发法研究了Na2CO3-Na2B4O7-H2O三元体系在273 K时的相平衡以及平衡液相的密度.利用溶解度数据绘制了该三元体系273K下的相图.研究发现,该体系属于简单共饱型,无复盐及固溶体形成,Na2CO3和Na2B4O7互有增溶作用.相图中单变量曲线所对应的平衡固相分别为Na2CO3·10H2O和Na2B4O7·10H2O.     

三元体系Na2B4O7-NaBr-H2O 298K相平衡研究

采用等温溶解平衡法研究了三元体系Na2B4O7-NaBr-H2O 298K时的相平衡及平衡液相的主要物化性质(密度,电导率,pH).研究发现:该三元体系为简单共饱和型,无复盐及固溶体形成.根据溶解度数据绘制了相图,相图中单变量曲线所对应的平衡固相分别为:Na2B4O7·10H2O,NaBr·2H2O;并简要讨论了物化性质的变化规律.     

三元体系Li2SO4-Li2B4O7-H2O在323．15K时相平衡研究

采用等温溶解平衡法研究了三元体系Li2SO4-Li2B4O7-H2O在323．15K时的溶解度及其平衡溶液的密度、pH性质,根据实验数据绘制了相应的平衡相图及其物化性质组成图。研究结果表明：该三元体系在323．15K时有2个结晶相区（Li2B4O7·3H2O和Li2SO4·H2O）、2条单变量溶解度曲线、1个共饱点,属简单共饱型。     

Li2CO3-Li2SO4-Li2B4O7-H2O四元体系273.15K介稳相平衡研究

采用等温蒸发法研究了四元体系Li2CO3-Li2SO4-Li2B4O7-H2O273.15K介稳相平衡,测定了该四元体系273.15K条件下介稳相平衡溶液的溶解度和密度,根据实验数据绘制了相应的相图.研究发现:该体系为简单共饱和型,无复盐及固溶体形成;相图中包含一个共饱点E,三条单变度曲线EE1,EE2,EE3,三个单盐结晶区,单盐形式分别为Li2CO3,Li2SO4·H2O,LBO2·8H2O.     

Antibacterial effect of lactoferricin B on Escherichia coli O157:H7 in ground beef.

The antibacterial activity of lactoferricin B on enterohemorrhagic Escherichia coli O157:H7 in 1% peptone medium and ground beef was studied at 4 and 10 degrees C. In 1% peptone medium, 50 and 100 microg of lactoferricin B per ml reduced E. coli O157:H7 populations by approximately 0.7 and 2.0 log CFU/ml, respectively. Studies comparing the antibacterial effect of lactoferricin B on E. coli O157:H7 in 1% peptone at pH 5.5 and 7.2 did not reveal any significant difference (P > 0.5) at the two pH values. Lactoferricin B (100 microg/g) reduced E. coli O157:H7 population in ground beef by about 0.8 log CFU/g (P < 0.05). No significant difference (P > 0.5) was observed in the total plate count between treatment and control ground beef samples stored at 4 and 10 degrees C. The antibacterial effect of lactoferricin B on E. coli O157:H7 observed in this study is not of sufficient magnitude to merit its use in ground beef for controlling the pathogen.     

The survival of Escherichia coli O157:H7 in the presence of Penicillium expansum and Glomerella cingulata in wounds on apple surfaces

The survival of Escherichia coli O157:H7 in the presence of one of two plant pathogens, Penicillium expansum and Glomerella cingulata, in wounds on apples was observed during 14 days storage at room temperature (RT) and at 4 degrees C. The aim of this work was to determine if changes in apple physiology caused by the proliferation of fungal decay organisms would foster the survival of E. coli O157:H7. Trials were performed where (A) plant pathogens (4 log10 spores) were added to apple wounds 4 days before the wounds were inoculated with E. coli O157:H7 (3 log10 CFU g(-1) apple) (both RT and 4 degrees C storage), (B) plant pathogens and E. coli O157:H7 were added on the same day (both RT and 4 degrees C storage), and (C) E. coli O157:H7 was added 2 days (RT storage) and 4 days (4 degrees C storage) before plant pathogens. In all trials E. coli O157:H7 levels generally declined to <1 log10 at 4 degrees C storage, and in the presence of P. expansum at 4 degrees C or RT. However, in the presence of G. cingulata at RT E. coli O157:H7 numbers increased from 3.18 to 4.03 log10 CFU g(-1) in the apple wound during trial A, from 3.26 to 6.31 log10 CFU g(-1) during trial B, and from 3.22 to 6.81 log10 CFU g(-1) during trial C. This effect is probably a consequence of the attendant rise in pH from 4.1 to approximately 6.8, observed with the proliferation of G. cingulata rot. Control apples (inoculated with E. coli O157:H7 only) were contaminated with opportunistic decay organisms at RT during trials A and B, leading to E. coli O157:H7 death. However, E. coli O157:H7 in control apples in trial C, where no contamination occurred, increased from 3.22 to 5.97 log10 CFU g(-1). The fact that E. coli O157:H7 can proliferate in areas of decay and/or injury on fruit highlights the hazards associated with the use of such fruit in the production of unpasteurized juice.     

Fate of Escherichia coi O157:H7 during on-farm dairy manure-based composting

Studies were conducted to determine the fate of Escherichia coli O157:H7 in dairy manure-based compost in a field setting. Two trials were performed involving duplicate compost heaps constructed at an outdoor fenced site. The compost heaps were composed of dairy manure, old hay, feed waste, a mixture of sawdust and calf feces, and fresh hay. Samples of the composting mixture were inoculated with stx-negative E. coli O157:H7 B6914 at initial concentrations of 10(7) and 10(5) CFU/g for trial 1 and trial 2, respectively. Individual sample bags were placed on the surface and at three locations (top, center, and bottom) within each heap. Although the compost heaps achieved temperatures of 50 degrees C or above at all internal locations for at least 7 days, temperature stratification was observed. In trial 1, E. coli O157:H7 was detected by enrichment through 14 days within the heaps. When inoculated with 10(5) CFU/g in trial 2, E. coli O157:H7 was detected only through days 2, 2, and 5 at the top, center, and bottom locations, respectively. For both trials, the pathogen survived at the heap's surface for up to 4 months. The indicator commensal E. coli and coliforms were inactivated at a rate similar to that for E. coli O157:H7. Results indicate that composting, with periodic heap turning, can be a practical approach to inactivating E. coli O157:H7 in cattle wastes on the farm. Our data also suggest when compost heaps are not turned, E. coli O157:H7 may survive for months at the heap surface.     

Inhibition of Salmonella enterica and Escherichia coli O157:H7 on roasted turkey by edible whey protein coatings incorporating the lactoperoxidase system

The effects of whey protein isolate (WPI) coatings incorporating a lactoperoxidase system (LPOS) on the inhibition of Salmonella enterica and Escherichia coli O157:H7 on roasted turkey were studied by testing the initial inhibition as well as the inhibition during storage. The initial antimicrobial effects of WPI coatings incorporating LPOS (LPOS-WPI coatings) were examined with various inoculation levels and LPOS concentrations. LPOS-WPI coatings with 7 and 4% of LPOS demonstrated initial 3- and 2-log CFU/g reductions of S. enterica and E. coli O157:H7, respectively. The antimicrobial effect was observed regardless of whether the turkey was inoculated before or after coating. Storage studies were conducted for 42 days at 4 and 10 degrees C with S. enterica (6.0 log CFU/g)- or E. coli O157:H7 (5.6 log CFU/g)-inoculated sliced turkey. LPOS concentrations for the storage studies of S. enterica and E. coli O157:H7 were 5 and 3% (wt/wt), respectively, in the coating solution and in an LPOS solution for spreading. LPOS-WPI coatings inhibited the growth of both S. enterica and E. coli O157:H7 in turkey at both 4 and 10 degrees C for 42 days. The inhibition was more pronounced when the coating was formed on the surface of the turkey prior to inoculation than when the coating was formed on the inoculated surface. More effective inhibition of S. enterica and E. coli O157:H7 was observed with the LPOS-WPI coatings than with the LPOS solution-spreading treatment. LPOS-WPI coatings also retarded the growth of total aerobes during storage.     

Survival of Escherichia coli O157:H7 in ground-beef patties during storage at 2, -2, 15 and then -2 degrees C, and -20 degrees C

The survival of Escherichia coli O157:H7 and of a nonpathogenic control strain of E. coli was monitored in raw ground beef that was stored at 2 degrees C for 4 weeks, -2 degrees C for 4 weeks, 15 degrees C for 4 h and then -2 degrees C for 4 weeks, and -20 degrees C. Irradiated ground beef was inoculated with one E. coli control strain or with a four-strain cocktail of E. coli O157:H7 (ca. 10(5) CFU/g), formed into patties (30 to 45 g), and stored at the appropriate temperature. The numbers of the E. coli control strain decreased by 1.4 log 10 CFU/g, and pathogen numbers declined 1.9 log 10 CFU/g when patties were stored for 4 weeks at 20 degrees C. When patties were stored at -2 degrees C for 4 weeks, the numbers of the E. coli control strain and the serotype O157:H7 strains decreased 2.8 and 1.5 log 10 CFU/g, respectively. Patties stored at 15 degrees C for 4 h prior to storage at -2 degrees C for 4 weeks resulted in 1.6 and 2.7 log 10-CFU/g reduction in the numbers of E. coli and E. coli O157:H7, respectively. Storage of retail ground beef at 15 degrees C for 4 h (tempering) did not result in increased numbers of colony forming units per gram, as determined with violet red bile, MRS lactobacilli, and plate-count agars. Frozen storage (-20 degrees C) of ground-beef patties that had been inoculated with a single strain of E. coli resulted in approximately a 1 to 2 log 10-CFU/g reduction in the numbers of the control strain and individual serotype O157:H7 strains after 1 year. There was no significant difference between the survival of the control strain and the O157:H7 strains, nor was there a difference between O157:H7 strains. These data demonstrate that tempering of ground-beef patties prior to low-temperature storage accelerated the decline in the numbers of E. coli O157:H7.     

25℃NH3-K2SO4-(NH4)2SO4-H2O体系相平衡的研究

用等温法测定了 2 5℃NH3 K2 SO4 (NH4) 2 SO4 H2 O体系的液固相平衡数据 ,结果表明 ,随着液相中自由氨浓度的增加 ,硫酸钾和硫酸铵的溶解度都在明显降低。依据实验数据绘制的相图 ,提出了氨盐析法从硫酸氢钾水溶液中提取硫酸钾和硫酸铵的生产工艺 ,并对此工艺进行了分析计算。