Geomagnetic control of the foF2 long-term trends     

A. V. Mikhailov  D. Marin 《Annales Geophysicae》2000,18(6):653-665

Further development of the method proposed by Danilov and Mikhailov is presented. The method is applied to reveal the foF2 long-term trends on 30 Northern Hemisphere ionosonde stations. Most of them show significant foF2 trends. A pronounced dependence of trend magnitude on geomagnetic (invariant) latitude is confirmed. Periods of negative/positive foF2 trends corresponding to the periods of long-term increasing/decreasing geomagnetic activity are revealed for the first time. Pronounced diurnal variations of the foF2 trend magnitude are found. Strong positive foF2 trends in the post-midnight-early-morning LT sector and strong negative trends during daytime hours are found on the sub-auroral stations for the period with increasing geomagnetic activity. On the contrary middle and lower latitude stations demonstrate negative trends in the early-morning LT sector and small negative or positive trends during daytime hours for the same period. All the morphological features revealed of the foF2 trends may be explained in the framework of contemporary F2-region storm mechanisms. This newly proposed F2-layer geomagnetic storm concept casts serious doubts on the hypothesis relating the F2-layer parameter long-term trends to the thermosphere cooling due to the greenhouse effect.  相似文献   

A luminescence‐based chronology for the Harletz loess sequence,Bulgaria     

Johanna Lomax  Markus Fuchs  Pierre Antoine  Denis‐Didier Rousseau  France Lagroix  Christine Hatt  Samuel N. Taylor  Jessica L. Till  Maxime Debret  Olivier Moine  Diana Jordanova 《Boreas: An International Journal of Quaternary Research》2019,48(1):179-194

The Harletz loess‐palaeosol sequence is located in northwestern Bulgaria and represents an important link between well‐studied loess sequences in eastern Romania and further sites to the west of the Carpathians (e.g. Serbia and Hungary). The aim of this study was to establish a chronostratigraphy of the deposits, using various methods of luminescence dating, together with basic stratigraphical field observations as well as magnetic properties. Luminescence dating was carried out using the quartz fine grain fraction and a SAR protocol, and the feldspar coarse grain fraction, applying the MET‐pIRIR protocol. Due to underestimation of the quartz fine grain fraction in the lower parts of the sequence, the resulting chronology is mainly based on the feldspar ages, which are derived from the stimulation temperature at 150 °C. A comparison with nearby sequences from Serbia, Hungary and Romania, and interpretations obtained through the stratigraphical and sedimentological signature of the sequence, supports the established chronology. Our data suggest that the prominent palaeosol (soil complex) in the upper quarter of the sequence was formed during MIS 5. It would follow that large parts of the Last Glacial loess overlying this palaeosol were probably eroded, and that the thick loess accumulation underlying this soil complex can be allocated to the penultimate glacial (MIS 6). A prominent MIS 6 tephra, which has been reported from other sequences in the area, is also present at Harletz.  相似文献   

Erratum to: The Quadrennial Ozone Symposium 2016     

Sophie GODIN-BEEKMANN  Irina PETROPAVLOSKIKH  Stefan REIS  Paul NEWMAN  Wolfgang STEINBRECHT  Markus REX  Michelle L. SANTEE  Richard S. ECKMAN  Xiangdong ZHENG  Matthew B. TULLY  David S. STEVENSON  Paul YOUNG  John PYLE  Mark WEBER  Johanna TAMMINEN  Gina MILLS  Alkiviadis F. BAIS  Clare HEAVISIDE  Christos ZEREFOS 《大气科学进展》2018,35(3):368-369

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A Model for Understanding the Effects of Sediment Dynamics on Oyster Reef Development     

Rachel M. Housego  Johanna H. Rosman 《Estuaries and Coasts》2016,39(2):495-509

Previous field studies have demonstrated that sedimentation is an important factor that can limit oyster reef growth and restoration success. High relief reefs are more productive and resilient than low relief reefs, in part, because increasing reef height reduces sedimentation and enhances oyster growth. In this study, we investigated the relationship between initial reef height and reef development using a simple model. The model contains three coupled differential equations that describe changes in oyster volume, shell volume, and sediment volume per unit area of reef with time. The model was used to investigate how parameters such as flow speed, sediment grain size, and food concentration affect reef survival and final reef height. Whether or not a reef survives depends primarily on the shape of the sediment concentration profile relative to the initial reef height. Over a long time period, three different steady-state reef heights are possible, depending on the environmental parameters and initial reef height: (1) If growth outpaces sedimentation, the reef achieves the maximum possible height, which is independent of sedimentation parameters; (2) if deposition outpaces growth and the shear stress does not exceed the critical shear stress, the reef is buried in sediment and dies; and (3) if deposition outpaces growth and the shear stress exceeds the critical shear stress, a reduced steady-state height is achieved that depends on both growth and sedimentation parameters. The model can be used to assess the ways in which measurable environmental parameters affect reef restoration success.  相似文献   

Climate change implications for Torres Strait fisheries: assessing vulnerability to inform adaptation     

Johanna E. Johnson  David J. Welch 《Climatic change》2016,135(3-4):611-624

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Unique paragenesis of cerium and yttrium allanites in tourmalinite of the Severny massif (Chukotka)     

V. I. Alekseev  Yu. B. Marin 《Doklady Earth Sciences》2016,469(1):748-750

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Across shore variability and trophodynamic features of meiofauna in a microtidal beach of the NW Mediterranean   总被引：2，自引：0，他引：2  

M. Moreno  T.J. Ferrero  V. Granelli  V. Marin  G. Albertelli  M. Fabiano 《Estuarine, Coastal and Shelf Science》2006,66(3-4):357-367

The across shore variability and trophodynamics of meiofauna were studied in a microtidal beach of the Thyrrenian Sea (NW Mediterranean). Two sites were sampled at Collelungo beach (Maremma Park, Italy) subjected to different regimes of sediment erosion and deposition. At each site, four levels were sampled in November 2002 and May 2003 along a transect from the supralittoral zone to the surf zone. Sediment cores were taken down to a depth of 10 cm and meiofaunal abundance and community structure were analyzed and related to the principal trophic resources (quantity and quality of organic matter, chlorophyll a, bacteria density and biomass).Meiofaunal abundance ranged between 14 ind. 10 cm⁻² and 716 ind. 10 cm⁻² in the top 0–10 cm of sediment. Abundance was lower in the surface (0–2 cm) than in the deeper (5–10 cm) sediment layers but no significant differences were found between the two sites.Multivariate BIOENV analysis showed that dryness, grain size (related to physical processes) and bacterial biomass, were the main variables explaining meiofauna distribution in these beaches. Meiofaunal densities and number of taxa were always higher at the swash level, while lower abundances were observed at the dry sampling level (+5 m). This across shore trend was also observed for the quality of the organic matter (PRT/CHO) and bacterial densities. Nematode assemblage structure at the swash sampling level showed a dominance of non-selective deposit feeders (1B), with Xyalidae as the dominant family (56%), followed by Thoracostomopsidae (14%) and Selachnematidae (12%).According to the findings, physical and biological variables at the swash level create optimal living conditions for the meiobenthos, making the swash a key area within the beach ecosystem, with potential implications within basic and applied ecological studies.  相似文献   

New Zealand coastal planning: an issue-based approach     

Johanna Rosier  Wayne Hastie 《Ocean & Coastal Management》1996,33(1-3)

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Cell responses to xenobiotics: comparison of MCF7 multi-drug- and mussel blood cell multi-xenobiotic-defense mechanisms     

Marin M  Legros H  Poret A  Leboulenger F  Le Foll F 《Marine environmental research》2004,58(2-5):209-213

Multi-drug resistance (MDR) in MCF7 breast cancer cells and multi-xenobiotic resistance (MXR) in mussel (Mytilus edulis) blood cells (MBC) are well known mechanisms that contribute to the decrease in intracellular concentrations of many unrelated but cytotoxic compounds. In the present work, we have carried out comparative investigations of the MDR/MXR protective mechanisms using a rapid colorimetric assay for cell viability and calcein accumulation for MDR/MXR activities. These studies were performed using cultured MCF7 and MBC before and after in vitro exposure to xenobiotics. Our results indicate that a 5-day exposure to doxorubicin or vincristine decreased calcein accumulation in MBC which is consistent with an induction of multi-xenobiotic resistance. The increase in calcein accumulation provoked by 1-h treatment with 50 microM verapamil was much lower in MBC when compared to the P-glycoprotein overexpressing MCF7 cell line. We conclude that such microplate assays could be used in primary cultures of MBC to estimate the effects of various chemicals on MXR activity.  相似文献   

The Palaeocene “top chron C27n” transient greenhouse episode: evidence from marine pelagic Atlantic and peri‐Tethyan sections     

Jaume Dinarès‐Turell  Victoriano Pujalte  Kristalina Stoykova  Juan I. Baceta  Marin Ivanov 《地学学报》2012,24(6):477-486

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