快速城市化地区小流域降雨径流污染特征

降雨径流污染对快速城市化地区的水环境安全造成巨大威胁.在对深圳市石岩水库6条入库支流的4次降雨径流事件进行水文水质监测的基础上,选择CODcr、NH3-N、TN、TP、SS和BOD5 6种常见水质测试指标对该区域的降雨径流污染的水质状况、空间差异和初始冲刷效应等基本特征进行了分析.结果表明,研究区降雨径流中耗氧性污染物...     

湖南"5·31"特大暴雨山洪成因及对策

介绍了2005年5月31日湖南特大暴雨山洪的特点,对引发这次山洪的气象因素、地质地貌因素及人为因素作了逐一分析,特别对造成这次暴雨过程的天气系统的发展和演变作了详细分析总结,对提高山洪地质灾害的监测预报预警水平提出建议,为预报及防御同类自然灾害提供参考。     

Responses of soil organic matter and microorganisms to freeze-thaw cycles

Soil organic matter (SOM) biomarker methods were utilized in this study to investigate the responses of fungi and bacteria to freeze-thaw cycles (FTCs) and to examine freeze-thaw-induced changes in SOM composition and substrate availability. Unamended, grass-amended, and lignin-amended soil samples were subject to 10 laboratory FTCs. Three SOM fractions (free lipids, bound lipids, and lignin-derived phenols) with distinct composition, stability and source were examined with chemolysis and biomarker Gas Chromatography/Mass Spectrometry methods and the soil microbial community composition was monitored by phospholipid fatty acid (PLFA) analysis. Soil microbial respiration was also measured before and during freezing and thawing, which was not closely related to microbial biomass in the soil but more strongly controlled by substrate availability and quality. Enhanced microbial mineralization (CO₂ flush), considered to be derived from the freeze-thaw-induced release of easily decomposable organic matter from microbial cell lyses, was detected but quickly diminished with successive FTCs. The biomarker distribution demonstrated that free lipids underwent a considerable size of decrease after repeated FTCs, while bound lipids and lignin compounds remained stable. This observation indicates that labile SOM may be most influenced by increased FTCs and that free lipids may contribute indirectly to the freeze-thaw-induced CO₂ flush from the soil. PLFA analysis revealed that fungal biomass was greatly reduced while bacteria were unaffected through the lab-simulated FTCs. Microbial community shifts may be caused by freezing stress and competition for freeze-thaw-induced substrate release. This novel finding may have an impact on carbon and nutrient turnover with predicted increases in FTCs in certain areas, because fungi and bacteria have different degradation patterns of SOM and the fungi-dominated soil community is considered to have a higher carbon storage capacity than a bacteria-dominated community.     

Physiological and Technical Aspects of Cactus Pear [Opuntia ficus-indica (L.) Mill.] Double Rellowering and Out-of-Season Winter Fruit Cropping

Abstract

A commercial cactus pear plantation in Sicily, Italy was manipulated to induce late cropping. The spring flush of flowers and cladodes were removed as was the second induced bloom of flowers and cladodes. The third induced bloom was harvested for a late out-of-season crop of cactus pear (Opuntia ficus-indica Mill.). The double removal induced a third flush of flowers and cladodes during late August with a fruit production that ripened the following winter (to March). The number of flowers per fertile cladode was halved after the double removal and the length of the fruit development period increased from 100-120 days to 160-190 days for the out-of-season crop. Polyethylene covering reduced sunlight but was essential for establishing optimal temperatures for cladode photosynthetic activity and fruit growth and ripening. Out-of-season fruits were regular in size and percent flesh with only a slight reduction in total soluble solid content.     

Dynamic computed tomography of the pituitary gland in dogs with pituitary-dependent hyperadrenocorticism

Dynamic computed tomography (CT) of the pituitary gland was performed in 55 dogs with pituitary-dependent hyperadrenocorticism (PDH) that underwent transsphenoidal hypophysectomy. On routine contrast-enhanced CT images, microadenomas of the pituitary gland often are indistinguishable from nontumorous pituitary tissue because of isoattenuation. Dynamic CT may allow visualization of these adenomas. The changes in the contrast-enhancement pattern of the pituitary during dynamic CT in 55 dogs with PDH were correlated with surgical and histopathologic findings. In 36 dogs, dynamic CT identified distinct contrast enhancement of the neurohypophysis (pituitary flush). In 24 dogs, this pituitary flush was displaced, which indicated the presence of an adenoma. This observation was confirmed surgically and histopathologically in 18 of the 24 dogs. In 19 dogs, there was a diffusely abnormal contrast-enhancement pattern. CT findings agreed with surgical findings in 13 of these dogs and with histopathologic findings in all 19 dogs. It is concluded that a dynamic series of scans should be included in the CT protocol of the pituitary gland in dogs with PDH because it allows for identification of an adenoma or a diffusely abnormal pituitary gland.     

Plant–herbivore asynchrony necessitates augmentative releases of the exotic beetle,Zygogramma bicolorata,to enhance the biological control of P arthenium hysterophorus

Systematic information on the quantitative impact of Z ygogramma bicolorata on the biology of P arthenium hysterophorus is crucial as the seeds of this weed continue to germinate from the accumulated soil seed bank throughout the year in the form of different germinating flushes, while the activity of the beetle ceases during winter as it enters diapause. Therefore, plant–herbivore interactions need to be explored to develop predictions of the overall impact of the introduced beetle on the weed. The findings revealed that defoliation by Z . bicolorata had a significant impact on the plant height, density and flower production in flushes F ₃, F ₄ and F ₅, but not in F ₁ and F ₂ that exhibited longer periodicity, profuse branching, a longer flowering period and maximum flower production and contributed mostly to the existing seed soil bank. Therefore, total depletion of the existing soil seed bank was not possible. Consequently, the effect of augmentative field releases of laboratory‐reared beetles was explored on F ₁ and F ₂ in February for three consecutive years (2011–2013). Before initiating the trial, random soil samples were taken from the plots that were assigned to the paired treatments (i.e. with the beetle and without the beetle [insecticide‐treated]) and it was found that the seed bank in those samples did not differ. The single release of Z . bicolorata adults at five per plant at the six‐leaf stage significantly reduced the soil seed bank, compared to without the biocontrol agent, irrespective of the flushes at the end of the season.     

输水渠系着生藻类水力生消动态建模及仿真研究

明渠输水系统由于着生藻类生长等因素,渠道糙率增加、渠道输水能力降低.现有的物理、化学、生物除藻方法因其各自的局限性而无法在灌区管理中广泛应用.水力除藻从水动力学角度出发,通过增大剪切层内水流对边界的剪应力,达到剥离水藻的目的.而研究水力除藻,水藻不能视为固定、静态的边界,因此需要建立藻类的生态系统模型.综合了以流速、温...     

非饱和土壤中氟离子迁移规律实验研究

采用实验室土柱法,在3种pH(4.0,5.5,7.5)淹灌和降雨条件下,研究了非饱和土壤中氟离子的迁移转化。结果表明:不同pH降雨、淹灌条件下,随着淋洗时间的增加,淋滤液中的可溶性氟含量逐渐增大,特别是pH5.5和pH7.5淋滤液中氟的变化规律明显。淹灌条件下淋滤液中氟含量低于降雨条件下淋滤液的氟含量。淋溶前后土壤表层的氟含量变化明显,淋滤后表层土壤表现为淋溶状态。土壤pH值是影响土壤氟存在形态的重要因素之一,对土壤可溶性氟有着重要的影响。     

A preliminary study of changes in tear film proteins in the feline eye following nictitating membrane removal

Objective To investigate the influence of nictitating membrane (third eyelid) removal on selected proteins in feline tears. Animal studied Domestic short‐haired cats (7–17 months; 2.6–5.2 kg) were used. Procedures Eye‐flush tears were collected periodically for up to 18 weeks from both eyes of animals with nictitating membranes removed, but nictitating gland left intact, (n = 4) or with nictitating membranes intact (n = 4). Tear comparisons were based on total protein content (TPC) using micro bicinchoninic acid assay, immunoglobulin A (IgA), and matrix‐metalloproteinase (MMP)‐9 measurements using sandwich enzyme‐linked immunosorbent assay (ELISA) and tear gelatinase activity using gelatin zymography. Expression of MMP‐2 and ‐9 in nictitating membranes removed at baseline (week 0) and eyes collected at 18 weeks were also investigated in histological sections using immunoperoxidase for visualization. Results Nictitating membrane removal did not significantly change TPC and MMP‐9 in tears within the first 4 weeks. MMP‐9 was not detected by ELISA in tears from eyes without nictitating membranes from week 5 onwards. IgA (%IgA of TPC) data varied between animals. Gelatin zymography showed increased MMP‐2 and ‐9 activity in tears from eyes without nictitating membranes at week 1 and a decrease following week 2 post‐surgery. MMP‐2 and ‐9 were immunolocalised to conjunctival goblet cells of removed nictitating membranes and to the conjunctival epithelium, respectively. After 18 weeks, the distribution of MMPs in tissue was comparable between eyes with and without nictitating membranes. Conclusions Based on this preliminary study, nictitating membrane removal appeared to cause long‐term changes in expression of tear proteins, including reduced MMP‐9 expression.