Influence of pH on the sonolysis of ciprofloxacin: Biodegradability, ecotoxicity and antibiotic activity of its degradation products

The presence of antibiotics in the aquatic environment has raised concerns due to the potential risk for the emergence or persistence of antibiotic resistance. Antibiotics are often poorly degraded in conventional wastewater treatment plants. In this study, sonolysis at 520 kHz and 92 W L⁻¹ was used for the degradation of the fluoroquinolone antibiotic ciprofloxacin. In a first experiment at pH 7, 57% of the ciprofloxacin (15 mg L⁻¹) was degraded after 120 min of ultrasonic irradiation at 25 °C. pH proved to be an important parameter determining the degradation rate, since the pseudo first order degradation constant increased almost fourfold when comparing treatment at pH 7 (0.0058 min⁻¹) and pH 10 (0.0069 min⁻¹) with that at pH 3 (0.021 min⁻¹). This effect can be attributed to the degree of protonation of the ciprofloxacin molecule. The BOD/COD ratio of the solutions, which is a measure for their biodegradability, increased from 0.06 to 0.60, 0.17, and 0.18 after 120 min of irradiation depending on the pH (3, 7, and 10, respectively). The solution treated at pH 3 can even be considered readily biodegradable (BOD/COD > 0.4). The antibiotic activity against Escherichia coli (G−) and Bacillus coagulans (G+) of the treated solutions also reduced after sonolysis. The highest decrease was again found when irradiated at pH 3. In contrast, ecotoxicity of the solutions to the alga Pseudokirchneriella subcapitata increased 3- to 10-fold after 20 min of treatment, suggesting the formation of toxic degradation products. The toxicity slowly diminished during further treatment.     

安全生产与经济社会发展关系理论研究

对美、英、加、日、澳等发达国家的安全生产状况近百年的统计数据进行了分析研究,发现大都经历了从事故频发到达高峰.逐步下降到平稳发展的"驼峰"过程,安全生产状况与经济社会发展阶段存在着相互制约、相互影响的联系,这是建立安全生产状况与经济发展水平的理论模型的事实依据.安全生产状况随经济社会发展而呈现出阶段性的变化趋势.影响一个国家的职业安全健康水平的直接原因有经济上的(安全投入)、科学技术方面、管理制度方面以及教育文化水平方面的,其中经济发展水平是各种原因的根本.重点揭示了安全生产与经济社会发展关系的内在规律,建立了相应的理论模型.并把所建立的理论模型应用到我国的煤矿安全领域.理论模型与实际统计数据基本吻合.     

应用电性拓扑状态指数预测烷烃自燃点

建立了一个基于人工神经网络的定量结构-性质相关性模型,用于52种烷烃化合物自燃点的预测研究。应用原子类型电性拓扑状态指数作为表征分子结构特征的描述符。该指数既能表征分子的电子特性,又反映其拓扑特征,同时易于计算,并有较强的同分异构体区分能力。采用误差反向传播（BP）神经网络方法对烷烃自燃点与电性拓扑状态指数间可能存在的非线性关系进行拟合。将52种烷烃样本随机划分为训练集（30种）、验证集（8种）和测试集（14种）,并通过“试差法”确定网络的最优参数。运用最佳网络结构[64—1]对实验样本进行模拟,结果表明,多数样本的自燃点预测值与实验值符合良好,对于测试集,平均预测绝对误差为8．4℃,均方根误差为11．8,优于多元线性回归方法和传统基团贡献法所得结果。该方法的提出为工程上提供了一种根据分子结构预测有机物白燃点的有效方法。     

人类活动对浙江近海赤潮发生频率的影响分析

根据1933年到2004年间的统计资料,以10 a为周期分析了浙江沿岸赤潮的发展变化历程,并进一步以1997～2004年的统计资料为基础,采用灰色系统关联分析法研究了的浙江近海赤潮的发生频率和人类活动引起的营养物质输入的关系.结果表明,各相关因子对赤潮发生频率影响的关联序为:海水养殖产量(0.03)＞海水养殖面积(0.99)＞工业废水(0.89)＞生活污水(0.88)＞生活COD(0.79)＞总悬浮颗粒物(0.75)＞工业COD(0.72)＞降雨量(0.71)＞粉尘(0.69)＞烟尘(0.68).可见,赤潮发生与人类活动关系密切,其中海洋养殖自身污染是赤潮发生频率的主要诱因,陆源污染和大气湿沉降起着重要作用.     

青藏高原古里雅冰芯中痕量元素镉记录的大气污染:1900-1991

对取自青藏高原古雅冰帽的冰芯上部２０ｍｎ的样品中有毒金属镉反映的大气污染进行了研究,利用电感耦合等等离子体质谱仪对镉的浓度进行了检测,镉的浓度在２．２８－３０１ｐｇ．ｍｌ＾－１,平均为５１ｐｇ．ｍｌ＾－１,镉的浓度高于极地雪冰相应的时间的浓度。     

Length of feeding day and body weight of great tits in a single- and a two-predator environment

The risk of predation may influence the acquisition of energy and the feeding activity of animals. Feeding activity and body reserves of wintering great tits Parus major in response to the priority to food access were studied in two areas differing in incidence of predators. The one-predator area contained sparrowhawks Accipiter nisus only, whereas the two-predator area contained both sparrowhawks and pygmy owls Glaucidium passerinum, whose hunting periods overlap at dawn and dusk. In the two-predator area dominant great tits arrived at feeders significantly later in the morning, and left earlier in the evening, than their subordinate flock-mates. Hence, feeding day length of dominants was found to be significantly shorter. The reverse was true for the one-predator area. In addition, dominants carried significantly greater reserves than subordinates in the area inhabited by two predators. Factors constraining subcutaneous energy reserves were also studied in removal experiments. After the removal of dominant individuals, subordinate great tits did not reduce their body reserves in the two predator area. In contrast, subordinate great tits significantly reduced evening body reserves in the single-predator area. I concluded that the presence of the two predators increases unpredictability in feeding conditions for great tits. Dominant individuals responded to this by shortening their feeding day and increasing body reserves at dusk. Received: 8 December 1999 / Received in revised form: 15 March 2000 / Accepted: 31 March 2000     

不同硫源对红串红球菌生长和脱硫比活性的效应

本文牛磺酸、硫酸镁和二苯噻吩（ＤＢＴ）分别作为唯一硫源以及ＤＢＴ不同供给量对红串红球菌生长和脱硫比活性的效应进行了研究,结果表明,红串红球菌肯 利用有机和无机硫化合物作为硫源的能力。与牛磺酸和到镁相比,ＤＢＴ是促进红串红球菌生长和提高其脱硫比活红串红球菌的最大脱硫比活性达７９．１ｍｍｏｌ２ＨＢＰ．ｋｇ＾－１．ｈ＾－１。影响红串红球菌脱硫比活性的因素主要是其生长的不同阶段、ＤＢＴ供给量和羟基二苯生产     

Spermatophore characteristics in bushcrickets vary with parasitism and remating interval

Male bushcrickets provide females with a nuptial gift, a spermatophore, which is transferred to females at mating. The spermatophore consists of a gelatinous mass, the spermatophylax, and the sperm-containing ampulla. Male spermatophore size is positively correlated with insemination rate and female refractory period and therefore with male reproductive success. In this study, we examined spermatophylax weight, ampulla weight and sperm number in males of Poecilimon mariannae parasitized by the acoustically orienting fly Therobia leonidei. We show that in parasitized males, spermatophylax weight decreases with the level of parasitism. In line with the hypothesis that parasitism is a cost to reproduction, we found that spermatophylax weight was reduced at remating. In contrast, the replenishment of the spermatophylax in unparasitized males was complete after 2 days and was increased no further after 3 days. Both sperm number and ampulla weight showed an increase over time since last mating and sperm production was estimated at a constant rate of 500,000 per day in all individuals, regardless of parasitism. The allocation of investment in components of the spermatophore varies greatly with parasitism and remating. Both factors had rather independent effects on spermatophore constitution, revealing functional constraints acting on spermatophore characteristics in bushcrickets, which are important for understanding the selection pressures working on its components. Received: 13 September 1999 / Received in revised form: 4 February 2000 / Accepted: 13 March 2000     

Analysis of gross alpha, gross beta activities and beryllium-7 concentrations in surface air: their variations and statistical prediction model

Measurement of gross α, gross β activities and cosmogenic beryllium-7 (⁷Be) concentrations were made both daily and weekly during the years 2001–2004 from samples of atmospheric aerosols filtered from the air at Tehran Nuclear Research Center (35 41′ N) and Zahedan (28 29′ N). Weekly aerosol samples collected with the high-volume air samplers on cellulose filters were used to determine the ⁷Be contents of samples, using a semiconductor gamma spectrometer. Airborne dust samples were collected daily on fiber glass filters and used to determine the gross β and gross α activities with automatic beta analyzer and a ZnS(Ag) counter, respectively. In this work, the concentration and meteorological data were used to determine models for gross α, gross β and ⁷Be. The air concentrations of gross β and gross α activities and ⁷Be concentrations displayed lognormal distributions during the study period. Both β and ⁷Be have maximum activity concentrations during warm mid-year months.     

Start-up performances of dry anaerobic mesophilic and thermophilic digestions of organic solid wastes

Two dry anaerobic digestions of organic solid wastes were conducted for 6 weeks in a lab-scale batch experiment for investigating the start-up performances under mesophilic and thermophilic conditions. The enzymatic activities, i.e., β-glucosidase, N-α-benzoyl-Largininamide （BAA）-hydrolysing protease, urease and phosphatase activities were analysed. The BAA-hydrolysing protease activity during the first 2-3 weeks was low with low pH, but was enhanced later with the pH increase. β-Glucosidase activity showed the lowest values in weeks 1-2, and recovered with the increase of BAA-hydrolysing protease activity. Acetic acid dominated most of the total VFAs in thermophilic digestion, while propionate and butyrate dominated in mesophilic digestion. Thermophilic digestion was confirmed more feasible for achieving better performance against misbalance, especially during the start-up period in a dry anaerobic digestion process.