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排序方式: 共有123条查询结果,搜索用时 31 毫秒
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Coupled Hydrological/Hydraulic Modelling of River Restoration Impacts and Floodplain Hydrodynamics
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H. M. Clilverd J. R. Thompson C. M. Heppell C. D. Sayer J. C. Axmacher 《河流研究与利用》2016,32(9):1927-1948
Channelization and embankment of rivers has led to major ecological degradation of aquatic habitats worldwide. River restoration can be used to restore favourable hydrological conditions for target species or processes. However, the effects of river restoration on hydraulic and hydrological processes are complex and are often difficult to determine because of the long‐term monitoring required before and after restoration works. Our study is based on rarely available, detailed pre‐restoration and post‐restoration hydrological data collected from a wet grassland meadow in Norfolk, UK, and provides important insights into the hydrological effects of river restoration. Groundwater hydrology and climate were monitored from 2007 to 2010. Based on our data, we developed coupled hydrological/hydraulic models of pre‐embankment and post‐embankment conditions using the MIKE‐SHE/MIKE 11 system. Simulated groundwater levels compared well with observed groundwater. Removal of the river embankments resulted in widespread floodplain inundation at high river flows (>1.7 m3 s?1) and frequent localized flooding at the river edge during smaller events (>0.6 m3 s?1). Subsequently, groundwater levels were higher and subsurface storage was greater. The restoration had a moderate effect on flood peak attenuation and improved free drainage to the river. Our results suggest that embankment removal can increase river–floodplain hydrological connectivity to form a more natural wetland ecotone, driven by frequent localized flood disturbance. This has important implications for the planning and management of river restoration projects that aim to enhance floodwater storage, floodplain species composition and biogeochemical cycling of nutrients. © 2016 The Authors. River Research and Applications Published by John Wiley & Sons Ltd. 相似文献
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Keeton Courtney Pierce; Perry-Jenkins Maureen; Sayer Aline G. 《Canadian Metallurgical Quarterly》2008,22(2):212
In this study, the authors examined the relationship between sense of control and depressive and anxious symptoms for mothers and fathers during the 1st year of parenthood. Participants were 153 dual-earner, working-class couples who were recruited during the 3rd trimester of pregnancy at prenatal education courses. Data were collected 1 month antenatally and 1, 4, 6, and 12 months postnatally. Sense of control was decomposed into 2 distinct parts: an enduring component and a malleable component that changes with context. Consistent with a cognitive theory of emotional problems, results demonstrated that a sense of control served a protective function for mental health outcomes. A higher sense of enduring control predicted lower levels of psychological distress for new parents, and increases in control over time predicted decreases in depression and anxiety. Findings hold implications for interventions with expectant parents, such as expanding prenatal education courses to include strategies for enhancing and maintaining a sense of personal control. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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Jane M. Sayer Jamshed H. Shah Chengyi Liang Guojian Xie Heiko Kroth Haruhiko Yagi 《Polycyclic Aromatic Compounds》2013,33(1-4):95-104
For oligonucleotide duplexes derived from trans opening of benzo[a]pyrene diol epoxides (BaP DEs) by the exocyclic N6-amino group of deoxyadenosine (dA), the hydrocarbon is intercalated toward the 5′-end of the modified strand when the configuration at the site of attachment of the base to the hydrocarbon (C-10) is R, and toward the 3′-end when this configuration is S. In oligonucleotide 11-mer duplexes modified by BaP DE-1 (benzylic 7-OH and epoxide oxygen cis) and DE-2 (7-OH and epoxide oxygen trans), as well as 7,8,9,10-tetrahydro BaP 9,10-epoxide, 10R adducts had consistently higher (5–9d°C) Tm values than the corresponding 10S adducts. Dodecamer duplexes from the HPRT gene with trans opened 10S (but not those with 10R) BaP DE-2 adducts at either of two adjacent dA residues exhibited blue shifts at ~350 nm at temperatures well below the Tm. We propose that these blue shifts result from a conformation in which the hydrocarbon is not stacked with the DNA bases. 相似文献
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CW Critchlow CM Surawicz KK Holmes J Kuypers JR Daling SE Hawes GM Goldbaum J Sayer C Hurt C Dunphy 《Canadian Metallurgical Quarterly》1995,9(11):1255-1262
OBJECTIVE: To determine the risk of developing high grade anal squamous intraepithelial neoplasia (HG-AIN) in relation to HIV infection and immunosuppression, after controlling for the effects of human papillomavirus (HPV) infection. DESIGN: Prospective cohort study of 158 HIV-seropositive and 147 HIV-seronegative homosexual men presenting to a community-based clinic with initially negative anal cytologic and colposcopic findings. METHODS: Subjects completed self-administered questionnaires, underwent cytologic screening, and standardized unaided and colposcopic examination of the proximal anal canal for presence of abnormalities suggestive of AIN. Anal specimens were screened for HPV DNA. RESULTS: HG-AIN developed in eight (5.4%) and 24 (15.2%) HIV-seronegative and -seropositive men, respectively. Risk of HG-AIN among HIV-seronegative men was associated with detection of anal HPV types 16 or 18 by Southern transfer hybridization (STH), detection of HPV 16 or 18 at the lower levels by polymerase chain reaction but not by STH, and with number of positive HPV tests; HG-AIN risk among HIV-seropositive men was associated with detection of HPV 16 or 18 only by STH, detection of HPV types other than 16 or 18, CD4 count < or = 500 x 10(6)/l, and number of positive HPV tests. HIV-induced immunosuppression remained an independent predictor of HG-AIN after adjusting for type and level of detection of HPV; HIV infection predicted HG-AIN risk after adjustment for number of positive HPV tests. CONCLUSIONS: The association of HG-AIN with HIV, independent of HPV type, level of HPV detection and number of positive HPV tests, suggests that this increased risk cannot be entirely explained by an effect of HIV on HPV detection. Future studies focusing on factors more specific to the local microenvironment in the anal canal should help clarify these issues. 相似文献
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Experimental and theoretical investigations of optical phase modulation induced by thick piezoelectric lead zirconate titanate (PZT) film coated coaxially on single mode optical fibres are presented for the first time. PZT film thicknesses up to 120 μm have been realised by a sol-gel based process. The measured phase modulation ranges from hundreds of kilohertz to several megahertz 相似文献
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Stuss Donald T.; Alexander Michael P.; Palumbo Carole L.; Buckle Leslie; Sayer Lisa; Pogue Janice 《Canadian Metallurgical Quarterly》1994,8(3):355
To define the capacity to organize verbal learning after frontal lobe injury, 32 patients with stable frontal lesions were evaluated with list learning tasks. Lesion size and site were determined from CAT or magnetic resonance imaging (MRI) scans. The lists were contructed to assess several potential organizational processes. A mild deficit in recognition performance was observed in patients with left frontal lesions accompanied by residual minor language impairments or in patients with septal lesions. Patients with frontal lesions also had a verbal recall deficit that was related to several factors: poor higher order organization of learning, independent of lesion size or site; a selective secondary memory impairment, associated with a language deficit and size of the lesion in the left frontal region; and excess intralist repetitions in patients with right frontal lesions. Impaired list learning after frontal lesions involves several independent psychological processes. This functional heterogeneity is based on regional anatomical specialization and dissociation of task processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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JW Sayer C Gutteridge D Syndercombe-Court P Wilkinson AD Timmis 《Canadian Metallurgical Quarterly》1998,32(7):1962-1968
OBJECTIVES: To examine circadian changes in the sympathovagal balance, the activity of the renin-angiotensin system and hemostatic variables in patients with stable coronary artery disease, and the effects of beta-adrenoceptor blockade and angiotensin-converting enzyme inhibition. BACKGROUND: Sympathovagal balance and key components of the fibrinolytic system show circadian variability. The effects of beta-adrenergic blocking agents and angiotensin-converting enzyme inhibitors on these autonomic and hemostatic rhythms are not well defined. METHODS: Twenty patients with coronary artery disease underwent 24-h Holter monitoring for heart rate variability and blood sampling (6 hourly for 24 hours) after three consecutive treatment phases, (firstly with placebo, then bisoprolol, and finally quinapril). The effects on sympathovagal balance, hemostatic variables and the renin-angiotensin system activity were measured. RESULTS: The fibrinolytic capacity showed marked circadian variation at the end of the placebo phase (p = 0.002), plasminogen activator inhibitor-1 (PAI-1) activity peaking at 06.00 AM when tissue plasminogen activator (tPA) activity was at its nadir. Sympathovagal balance showed a sharp increase at approximately the same time but plasma renin activity did not rise until later in the day. Inspection of the 24-h profiles suggested that bisoprolol reduced sympathovagal balance and the morning peak of PAI-1 activity and antigen, with a small increase in tPA activity, although these changes were not significant. Quinapril produced a substantial rise in renin (p = 0.01) but did not significantly affect either PAI-1 or tPA. Sympathovagal balance was unaffected by quinapril. CONCLUSIONS: In patients with stable coronary artery disease, angiotensin-converting enzyme inhibition with quinapril does not affect either sympathovagal balance or the endogenous fibrinolytic system. Our data suggest that the sympathoadrenal system may modify fibrinolytic activity, judged by the response to beta-adrenoreceptor blockade with bisoprolol. 相似文献