Segmentation and kinematics of the North America‐Caribbean plate boundary offshore Hispaniola          下载免费PDF全文

Sylvie Leroy  Nadine Ellouz‐Zimmermann  Jordane Corbeau  Frédérique Rolandone  Bernard Mercier de Lépinay  Bertrand Meyer  Roberte Momplaisir  José‐Luis Granja Bruña  Anne Battani  Céline Baurion  Evgueni Burov  Valérie Clouard  Rémy Deschamps  Christian Gorini  Youri Hamon  Manfred Lafosse  Jottin Leonel  Laetitia Le Pourhiet  Pilar Llanes Estrada  Nicolas Loget  Francis Lucazeau  Daniel Pillot  Jeffrey Poort  Kevin R. Tankoo  José‐Luis Cuevas  José‐Fernando Alcaide  Claude Jean Poix  Alfonso Muñoz‐Martin  Serge Mitton  Yamil Rodriguez  Julien Schmitz  Leonardo Seeber  Andres Carbo‐Gorosabel  Santiago Muñoz 《地学学报》2015,27(6):467-478

We explored the submarine portions of the Enriquillo–Plantain Garden Fault zone (EPGFZ) and the Septentrional–Oriente Fault zone (SOFZ) along the Northern Caribbean plate boundary using high‐resolution multibeam echo‐sounding and shallow seismic reflection. The bathymetric data shed light on poorly documented or previously unknown submarine fault zones running over 200 km between Haiti and Jamaica (EPGFZ) and 300 km between the Dominican Republic and Cuba (SOFZ). The primary plate‐boundary structures are a series of strike‐slip fault segments associated with pressure ridges, restraining bends, step overs and dogleg offsets indicating very active tectonics. Several distinct segments 50–100 km long cut across pre‐existing structures inherited from former tectonic regimes or bypass recent morphologies formed under the current strike‐slip regime. Along the most recent trace of the SOFZ, we measured a strike‐slip offset of 16.5 km, which indicates steady activity for the past ~1.8 Ma if its current GPS‐derived motion of 9.8 ± 2 mm a^?1 has remained stable during the entire Quaternary.  相似文献   

Moving from rhetoric into action: effectiveness of state–civil society synergy for healthcare delivery in rural Ghana     

Francis Jagri  Thomas Yeboah 《GeoJournal》2016,81(3):411-425

The issue of extending healthcare to marginalized underserved rural population remains a cardinal rhetoric policy of the Ghana Government. Meanwhile we note a growing inequity in terms of access and utilization of quality and affordable healthcare between urban and rural areas of the country. The Government of Ghana through its various policy initiatives in 2002 collaborated with civil societies with the aim of bringing healthcare to the doorsteps of rural folks in the country. Using a mixed method approach through a semi structured interviews and questionnaire administration, and focusing on the Community-based Health Planning and Services (CHPS) programme in Nsanfo community in the Mfanstiman municipal area, this study assesses the effectiveness and challenges confronting state–civil society partnership in co-producing a public good (healthcare). We found that synergy between the state (Mfanstiman Municipal Health Directorate) and the civil society (community health volunteers) has yielded positive results in bringing healthcare to the door steps as well as improving the health conditions of the local people in the study area. Nonetheless, certain challenges such as lack of volunteer motivation, deplorable state of the CHPS compound and logistics threaten the very existence of this collaboration. Our study has far reaching implications for healthcare planning in Ghana.  相似文献   

Attribution of extreme temperature changes during 1951–2010     

Yeon-Hee Kim  Seung-Ki Min  Xuebin Zhang  Francis Zwiers  Lisa V. Alexander  Markus G. Donat  Yu-Shiang Tung 《Climate Dynamics》2016,46(5-6):1769-1782

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Marine Community Ecology and Conservation M.D. Bertness,J.F. Bruno,B.R. Silliman,J.J. Stachowicz (Eds) Sunderland,MA: Sinauer Associates Inc., 2014. 556 pp. ISBN 978‐1‐60535‐228‐2. Hardback: US$109.95.          下载免费PDF全文

Anne Shaffer  Mauricio Carrasquilla‐Henao  Francis Juanes 《Marine Ecology》2016,37(4):927-928

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The removal kinetics of dissolved organic matter and the optical clarity of groundwater     

Francis H. Chapelle  Yuan Shen  Eric W. Strom  Ronald Benner 《Hydrogeology Journal》2016,24(6):1413-1422

Concentrations of dissolved organic matter (DOM) and ultraviolet/visible light absorbance decrease systematically as groundwater moves through the unsaturated zones overlying aquifers and along flowpaths within aquifers. These changes occur over distances of tens of meters (m) implying rapid removal kinetics of the chromophoric DOM that imparts color to groundwater. A one-compartment input-output model was used to derive a differential equation describing the removal of DOM from the dissolved phase due to the combined effects of biodegradation and sorption. The general solution to the equation was parameterized using a 2-year record of dissolved organic carbon (DOC) concentration changes in groundwater at a long-term observation well. Estimated rates of DOC loss were rapid and ranged from 0.093 to 0.21 micromoles per liter per day (μM d^?1), and rate constants for DOC removal ranged from 0.0021 to 0.011 per day (d^?1). Applying these removal rate constants to an advective-dispersion model illustrates substantial depletion of DOC over flow-path distances of 200 m or less and in timeframes of 2 years or less. These results explain the low to moderate DOC concentrations (20–75 μM; 0.26–1 mg L^?1) and ultraviolet absorption coefficient values (a ₂₅₄?<?5 m^?1) observed in groundwater produced from 59 wells tapping eight different aquifer systems of the United States. The nearly uniform optical clarity of groundwater, therefore, results from similarly rapid DOM-removal kinetics exhibited by geologically and hydrologically dissimilar aquifers.  相似文献   

Variable Nitrification Rates Across Environmental Gradients in Turbid,Nutrient-Rich Estuary Waters of San Francisco Bay     

Julian Damashek  Karen L. Casciotti  Christopher A. Francis 《Estuaries and Coasts》2016,39(4):1050-1071

Understanding rates of nitrogen cycling in estuaries is crucial for understanding their productivity and resilience to eutrophication. Nitrification, the microbial oxidation of ammonia to nitrite and nitrate, links reduced and oxidized forms of inorganic nitrogen and is therefore an important step of the nitrogen cycle. However, rates of nitrification in estuary waters are poorly characterized. In fall and winter of 2011–2012, we measured nitrification rates throughout the water column of all major regions of San Francisco Bay, a large, turbid, nutrient-rich estuary on the west coast of North America. Nitrification rates were highest in regions furthest from the ocean, including many samples with rates higher than those typically measured in the sea. In bottom waters, nitrification rates were commonly at least twice the magnitude of surface rates. Strong positive correlations were found between nitrification and both suspended particulate matter and ammonium concentration. Our results are consistent with previous studies documenting high nitrification rates in brackish, turbid regions of other estuaries, many of which also showed correlations with suspended sediment and ammonium concentrations. Overall, nitrification in estuary waters appears to play a significant role in the estuarine nitrogen cycle, though the maximum rate of nitrification can differ dramatically between estuaries.  相似文献   

Evidence for centennial-scale Lateglacial and early Holocene climatic complexity from Quoyloo Meadow,Orkney, Scotland     

Rhys G. O. Timms  Ashley M. Abrook  Ian P. Matthews  Christopher P. Francis  Agnieszka Mroczkowska  Ian Candy  Stephen J. Brooks  Alice M. Milner  Adrian P. Palmer 《第四纪科学杂志》2021,36(3):339-359

The influence of the North Atlantic on the margins of Europe means the region is particularly sensitive to changes in the ocean–atmospheric system. During the Last Glacial–Interglacial Transition (16–8 cal ka bp ) this system was repeatedly disrupted, leading to a series of abrupt and short-lived shifts in climate. Despite much research, the number and magnitude of these ‘centennial-scale’ events is not well understood. To address this, we expand upon investigations at Quoyloo Meadow, Orkney, Scotland, one of the best chronologically constrained palaeoclimate records in northern Britain. By coupling stable isotope and chironomid fossil analyses with existing data, this study identifies multiple phases of centennial-scale disturbance at: c. 14.0, 11.1, 10.8, 10.5, 10.45 and 10.3 cal ka bp , with the events at 14.0 and 10.3 exhibiting a particularly pronounced cold-climate signature. During the Holocene, the strongest response to climate forcing was at c. 10.3–10.0 cal ka bp , expressed as a two-stage drop in mean July temperatures, a shift in pollen spectra indicative of ‘less-stable’ climatic regimes, and a depletion in δ¹⁸O values. We interpret this as the first reliably dated incidence of the ‘10.3-ka event’ in the British Isles and consider the wider impact of this climatic reversal in other Holocene records.  相似文献   

Hydro-geochemistry of groundwater and surface water in Dschang town(West Cameroon): Alkali and alkaline-earth elements ascertain lithological and anthropogenic constraints          下载免费PDF全文

Yemeli Elida Joelle  Temgoua Emile  Kengni Lucas  Ambrosi Jean-Paul  Momo-nouazi Mathieu  Silatsa-Tedou Francis Brice  Wamba Franck Robean  Tchakam-Kamtchueng Brice 《地下水科学与工程》2021,9(3):212-224

This study focuses on the sources of alkali and alkaline-earth elements based on the geochemistry of groundwater and surface water in Dschang concerning environmental and anthropogenic constraints. A comprehensive set of 50 samples from groundwater and surface water were analyzed by ICPMS and processed by spatial interpolation in a GIS environment. The results highlight a geochemical anomaly at the center of the densely inhabited area subject to a profusion of open dumps discharges. This anomaly with the highest spatial contents of Be(Cs, Rb, Mg) suggests an anthropogenic source that demarcates with the lowest alkali and alkaline-earth elements on the peripheral area of Dschang. Other findings include lithological constraints with volcanic rocks being the main source compared to granitoid.The study points out good correlations between Be, Cs, Rb and Mg spatial distributions and physicochemical parameters of waters(K, EC, TDS), and inversely with the lowest p H. p H is established as the most functioning physico-chemical constraint of alkali and alkaline-earth mobility in Dschang. The p H lowest values within the geochemical anomaly also highlight the impact of human activities on water acidity, which later enhance elements mobility and enrichment. Despite low elements contents relative to WHO standards, our findings point out an example of anthropogenic impact on water geochemistry linked to solid waste pollution; it also demonstrates significant anthropogenic changes of environmental physicochemical parameters of prime importance in the mobility and distribution of elements in the study area.Similar assessments should be extended in major towns in Cameroon.  相似文献   

Examination of climate risk using a modified uncertainty matrix framework—Applications in the water sector     

Marie Ekström  Natasha Kuruppu  Robert L. Wilby  Hayley J. Fowler  Francis H.S. Chiew  Suraje Dessai  William J. Young 《Global Environmental Change》2013,23(1):115-129

Previous climate risk assessments provide important methodological insights into how to derive tractable research questions and the appropriate use of data under uncertainty, as well as identifying steps that benefit from stakeholder involvement. Here we propose the use of a framework for the systematic and objective exploration of climate risk assessments. The matrix facilitates a breakdown of information about aim and context, main results, methodological choices, stakeholder involvement, sources and characteristics of uncertainties and overall weaknesses. We then apply the matrix to three risk assessments in the water sector to explore some methodological strengths and weaknesses of approaches strongly linked to climate model outputs (top-down) versus those that originate from local knowledge of climate exposures (bottom-up), and demonstrate that closer integration with social and physical sciences is more likely to yield robust climate risk assessments.  相似文献   

Ion exchange reactions of KNiAsO4     

A. M. Buckley  S. T. Bramwell  P. Day 《Physics and Chemistry of Minerals》1988,15(5):446-451

The mica-like layer compound KNiAsO₄ easily exchanges its interlayer potassium ions for alkyl ammonium ions, RNH ₃ ⁺ (R=CH₃ - C₁₈H₃₇). Short chain ions (<>₄) will react in aqueous solution and longer chains in ethanolic solution. The reaction of KNiAsO₄ with aqueous solutions of methyl, ethyl and butyl ammonium chlorides of different concentrations has been investigated using a potassium ionselective electrode. Room temperature kinetic curves of percent exchange vs time were obtained. These indicate an apparent cooperative mechanism with some rearrangement of the alkyl ammonium ions between the layers during the reaction. KNiAsO₄ also reacts with water. This reaction may facilitate the exchange reaction with aqueous alkyl ammonium ions. The alkyl ammonium ions form ordered arrangements between the [NiAsO₄]^– layers. Small chains (<>₄) adopt a variety of configurations within the same product.Paper from the NATO Advanced Study Institute on Physical Properties and Thermodynamic Behaviour of Minerals, Cambridge 1987  相似文献