发呆,也是一种小美好

正白岩松说,没事儿的时候发发呆。我们疲于追逐成功的路上,发呆成了一种奢侈。是啊,回想一下,在我们每天仅有的24小时中,工作、交际以及各种琐事占据了大半,剩下的注意力又被手机等携带大量娱乐信息的产品夺走。我们每天生活的似乎都很"丰满",迈着急促的脚步穿梭于公司、学校、商场、电影院之间,甚至感觉时间不够用,经常熬夜到凌晨,因此,我们没有多余的时间去发呆,或者说,在这个充满娱乐信息的时代,我们不需要去孤独地发呆。     

Effect of agitation, turbidity, aluminium foil reflectors and container volume on the inactivation efficiency of batch-process solar disinfectors

We report the results of experiments designed to improve the efficacy of the solar disinfection of drinking water, inactivation process. The effects of periodic agitation, covering the rear surface of the container with aluminium foil, container volume and turbidity on the solar inactivation kinetics of Escherichia coli (starting population = 10(6) CFU ml(-1)) were investigated. It was shown that agitation promoted the release of dissolved oxygen from water with subsequent decrease in the inactivation rates of E. coli. In contrast, covering the rear surface of the solar disinfection container with aluminium foil improved the inactivation efficiency of the system. The mean decay constant for bacterial populations in foil-backed bottles was found to be a factor of 1.85 (std. dev. = 0.43) higher than that of non-foil-backed bottles. Inactivation rates decrease as turbidity increases. However, total inactivation was achievable in 300 NTU samples within 8 h exposure to strong sunshine. Inactivation kinetics was not dependent on the volume of the water container for volumes in the range 500-1500 ml.     

Enrichment of Cu,Ni, Zn,Pb and As in an ombrotrophic peat bog near a Cu-Ni smelter in southwest Finland

The accumulation of selected trace elements (Cu, Ni, Zn, Pb, As) in the surface peat layer of an ombrotrophic bog 2.4 km from a Cu-Ni smelter at Harjavalta, Finland was studied using a peat core. A reference core was taken from an ombrotrophic bog at a background site, Hietaj?rvi, in eastern Finland. Element concentrations were analysed from 1-cm slices and enrichment factors (EF) were calculated. The enrichment factors of both Cu and Ni in the Harjavalta peat bog are extremely high compared to the Hietaj?rvi site. However, only the 6-cm surface peat Pb values are higher in Harjavalta compared to Hietaj?rvi. Precipitation was collected during 1992-1996, in the vicinity of the Harjavalta smelter, in order to estimate the current atmospheric deposition load. Comparison between the precipitation and peat data reveals that at Harjavalta the surface peat is relatively much more polluted than the current precipitation. The variation in EF of the Harjavalta peat core with respect to depth shows two patterns: Cu and Pb are similar, as are Ni, Zn and As. The vertical gradient in Harjavalta Cu EF suggests that Cu supplied to the peat by atmospheric deposition is very well preserved by the bog.     

Heavy metals in maternal and cord blood

Heavy metal concentrations have been determined in maternal and cord blood samples collected from mothers in the age group 20-25 years with full-term neonates (37-40 weeks). The concentrations of Pb, Cd, Cu and Zn were found to be low in cord blood as compared to mother's blood and the ratio between cord blood and maternal blood for the respective elements was found to be approximately 0.80, 0.86, 0.47 and 0.40. On the other hand, the concentrations of Fe and Mg in the mother's blood were found to be lower than those in the cord blood. Prenatal exposure to lead in Mumbai, though low (5.1 microg/dl), is approximately 2-3 times higher than that observed in Canada or Italy. A strong correlation (r = 0.79) between the maternal and cord blood lead levels has been observed during the present study.     

高等级公路半刚性基层沥青路面水损坏的防治

论述了高等级公路沥青路面水损坏的特点、表现形式以及成因，从包括原材料控制、沥青混合料配合比设计、施工工艺、压实工艺、结构排水以及预防性养护和控制交通等方面对防治沥青路面水损坏提出了相应的技术措施及建议。     

Trace element concentrations in the Pacific harbor seal (Phoca vitulina richardii) in central and northern California

To determine concentrations of trace elements (THg, MeHg, Se, and Pb) in tissues of the Pacific harbor seal (Phoca vitulina richardii), live (n=186) and dead seals (n=53) were sampled throughout central and northern California from March 2003 to January 2005. There were significant differences in THg concentrations in blood and hair based on age (p<0.001). Adult male harbor seals had greater THg concentrations in their hair than adult female harbor seals (p<0.003). THg concentrations in liver increased linearly with age and delta15N (p<0.001); whereas, MeHg concentrations in liver increased exponentially until approximately 5 years of age with an asymptote at 1.3 microg/g wet weight. MeHg expressed as a percentage of THg (%MeHg) was best described by a decay function (r2=0.796, p<0.001), decreasing to a minimum at 4 years of age. Hepatic Se increased with age and was in equimolar ratios with THg in adults; whereas, molar ratio of Se:THg in pups deviated from a 1:1 ratio. Significant differences among study locations in THg concentrations in blood and hair were not detected. Assessing the possible effect of sampling location on Hg concentrations, however, was confounded and limited by lack of equal sample sizes for basic age and sex cohorts, a common dilemma in pinniped research.     

Confirmation of putative stormwater impact on water quality at a Florida beach by microbial source tracking methods and structure of indicator organism populations

The effect of a stormwater conveyance system on indicator bacteria levels at a Florida beach was assessed using microbial source tracking methods, and by investigating indicator bacteria population structure in water and sediments. During a rain event, regulatory standards for both fecal coliforms and Enterococcus spp. were exceeded, contrasting with significantly lower levels under dry conditions. Indicator bacteria levels were high in sediments under all conditions. The involvement of human sewage in the contamination was investigated using polymerase chain reaction (PCR) assays for the esp gene of Enterococcus faecium and for the conserved T antigen of human polyomaviruses, all of which were negative. BOX-PCR subtyping of Escherichia coli and Enterococcus showed higher population diversity during the rain event; and higher population similarity during dry conditions, suggesting that without fresh inputs, only a subset of the population survives the selective pressure of the secondary habitat. These data indicate that high indicator bacteria levels were attributable to a stormwater system that acted as a reservoir and conduit, flushing high levels of indicator bacteria to the beach during a rain event. Such environmental reservoirs of indicator bacteria further complicate the already questionable relationship between indicator organisms and human pathogens, and call for a better understanding of the ecology, fate and persistence of indicator bacteria.     

自润滑关节轴承磨损量在线测量精度的影响因素

自润滑关节轴承的磨损量是其寿命评价的关键指标,系统分析了影响自润滑关节轴承在线磨损量测量精度的因素,并提出了针对性的改进措施和建议,为提高自润滑关节轴承磨损量在线测量精度提供一定的参考和借鉴。     

沿空巷道锚杆支护参数优化及应用研究

通过数值分析手段,采用普氏冒落拱理论对沿空巷道内采用类比法得到的锚杆长度进行了重新校核,探讨了在此种条件下锚杆长度的变化对围岩变形、应力变化、巷道破坏的影响,并最终确定了合理的支护参数,得到了在此种条件下的围岩控制技术。     

拱桥立柱盖梁裂缝分析

以某拱桥立柱盖梁为例,针对其裂缝发展进行参数分析,以期找到盖梁裂缝产生的原因,为后期桥梁的养护和运营提供参考。分析发现,裂缝的产生虽然是多因素作用的结果,但温度作用较其他因素来说影响较大,检测时发现盖梁普遍存在水蚀、垃圾堆积现象,后期养护应及时处治。