SN 2004A: another Type II-P supernova with a red supergiant progenitor     

M. A. Hendry  S. J. Smartt  R. M. Crockett  J. R. Maund  A. Gal-Yam †  D.-S. Moon  S. B. Cenko  D. W. Fox  R. P. Kudritzki  C. R. Benn  R. Østensen 《Monthly notices of the Royal Astronomical Society》2006,369(3):1303-1320

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The SCUBA 8-mJy survey – II. Multiwavelength analysis of bright submillimetre sources     

M. J.Fox  A.Efstathiou  M.Rowan-Robinson  J. S.Dunlop  S.Scott  S.Serjeant  R. G.Mann  S.Oliver  R. J.Ivison  A.Blain  O.Almaini  D.Hughes  C. J.Willott  M.Longair  A.Lawrence  J. A.Peacock 《Monthly notices of the Royal Astronomical Society》2002,331(4):839-852

We present the results of a multiwavelength study of the 19 most significant submillimetre (submm) sources detected in the SCUBA 8-mJy survey. As described in Scott et al. , this survey covers ≃260 arcmin² using the submillimetre camera SCUBA, to a limiting source detection limit   S _850 μm≃8 mJy  . One advantage of this relatively bright flux-density limit is that accurate astrometric positions are potentially achievable for every source using existing radio and/or millimetre-wave interferometers. However, an associated advantage is that spectral energy distribution (SED) based redshift constraints should be more powerful than in fainter submm surveys. Here we therefore exploit the parallel SCUBA 450-μm data, in combination with existing radio and Infrared Space Observatory ( ISO ) data at longer and shorter wavelengths to set constraints on the redshift of each source. We also analyse new and existing optical and near-infrared imaging of our SCUBA survey fields to select potential identifications consistent with these constraints. Our derived SED-based redshift constraints, and the lack of statistically significant associations with even moderately bright galaxies allow us to conclude that all 19 sources lie at   z >1  , and at least half of them apparently lie at   z >2  .  相似文献   

Food Habits of Large Nektonic Fishes: Trophic Linkages in Delaware Bay and the Adjacent Ocean     

K. W. Able  J. M. Morson  D. A. Fox 《Estuaries and Coasts》2018,41(3):866-883

Fish diets play a critical role in our understanding of aquatic trophic dynamics and are an important component in developing ecosystem-based approaches to fisheries management. Although large nektonic fishes exert top-down predator effects on the food web and typically support viable commercial and recreational fisheries, little is known about the diet of this guild. We evaluated the diets (6327 stomachs) of four nektonic predatory fishes (Pomatomus saltatrix [78–395 mm], Cynoscion regalis [91–520 mm], Morone americana [156–361 mm], and Morone saxatilis [82–785 mm]) in Delaware Bay and in the adjacent ocean. To assess ontogenetic, geographic, and interspecific variation in diets, observations from individual fish stomachs were clustered into species-size class groups, and dietary overlap was estimated using multivariate analyses. A shift in diet composition, as well as diversity, occurred along the estuarine gradient and into the adjacent ocean. Some prey were shared by most predators, including some crustaceans (dominated by Callinectes sapidus, mysids, and Palaemonetes spp.), fundulids (dominated by Fundulus heteroclitus), engraulids (dominated by Anchoa mitchilli), and clupeids (dominated by Brevoortia tyrannus). However, inter- and intra-specific variation in diet was observed as well. In particular, M. americana consumed fewer engraulids and clupeids, and many more and diverse types of invertebrates, while P. saltatrix consumed more clupeids and less invertebrates. The lack of overlap in diet between the four predators evaluated, and between size groups for each predator, supports previous evidence that these groups feed in trophic guilds defined by species and by size within a species. The highly variable diets for these predators suggest high resolution spatial data are necessary in order to quantify their most important prey and their role in coastal ecosystems.  相似文献   

Channel network extent in the context of historical land use,flow generation processes,and landscape evolution in the North Carolina Piedmont     

Anne J. Jefferson  Ralph W. McGee 《地球表面变化过程与地形》2013,38(6):601-613

Intensive agricultural land use in the 18th to early 20th centuries on the southeastern Piedmont resulted in substantial soil erosion and gully development. Today, many historically farmed areas have been abandoned and afforested, and such landscapes are an opportunity to study channel network recovery from disturbance by gullying. Channel initiation mapping, watershed area–slope relationships, and field monitoring of flow generation processes are used to identify channel network extent and place it in hydrologic, historical and landscape evolution context. In six study areas in the North Carolina Piedmont, 100 channel heads were mapped in fully‐forested watersheds, revealing a channel initiation relationship of 380 = AS^1.27, where A is contributing area (m²) and S is local slope (m/m). Flow in these channels is generated by subsurface and overland flow. The measured relative slope exponent is lower than expected based on literature values of ~2 for forested watersheds with subsurface and overland flow, suggesting that the channel network extent may reflect a former hydrological regime. However, geomorphic evidence of recovery in channel heads within fully forested watersheds is greater than those with present day pasture. Present day channel heads lie within hollows or downslope of unchanneled valleys, which may be remnants of historical gullies, and area–slope relationships provide evidence of colluvial aggradation within the valleys. Channel network extent appears to be sensitive to land use change, with recovery beginning within decades of afforestation. Channel initiation mapping and area–slope relationships are shown to be useful tools for interpreting geomorphic effects of land use change. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

The role of short-wave troughs on the formation and development of sea-effect snowbands in the western Black Sea     

Yavuz  Veli  Lupo  Anthony R.  Fox  Neil I.  Deniz  Ali 《Theoretical and Applied Climatology》2022,149(1-2):501-510

Theoretical and Applied Climatology - The short waves (less than 6000 km) embedded within the long waves and the resulting short-wave troughs have an effect on the sea-effect snow (SES)....  相似文献   

Explaining global patterns and trends in marine protected area (MPA) development     

Helen E. Fox  Carrie S. Soltanoff  Michael B. Mascia  Kelly M. Haisfield  Alfonso V. Lombana  Christopher R. Pyke  Louisa Wood 《Marine Policy》2012

The relative paucity and heterogeneous distribution of marine protected areas (MPAs) indicates the need for better understanding of factors that foster MPA establishment at local, sub-national, and national levels. The relationship between national-level MPA establishment and geographic, ecological, social, and political factors that may drive patterns and trends in MPA establishment were assessed. A country's coastline length is the strongest predictor of both the number and spatial extent of MPAs. Controlling for coastline, the Human Development Index (HDI) and spatial overlap with designated conservation priority areas are positively correlated with MPA establishment. Surprisingly, some factors influencing MPA establishment in case studies, such as percentage of fishers within a population, were not correlated with MPA establishment on a national scale. These national dynamics explain a relatively small proportion of variation, however, indicating that other biological or social factors, as well as sub-national processes, also influence MPA establishment. Positive and negative outliers illuminate the importance of policy engagement at both national and local levels. Ensuring a supportive enabling environment at the national or even multi-national level can enhance success at the local level.  相似文献   

Bank undercutting and tension failure by groundwater seepage: predicting failure mechanisms          下载免费PDF全文

Garey A. Fox  Rachel G. Felice 《地球表面变化过程与地形》2014,39(6):758-765

Groundwater seepage can lead to the erosion and failure of streambanks and hillslopes. Two groundwater instability mechanisms include (i) tension failure due to the seepage force exceeding the soil shear strength or (ii) undercutting by seepage erosion and eventual mass failure. Previous research on these mechanisms has been limited to non‐cohesive and low cohesion soils. This study utilized a constant‐head, seepage soil box packed with more cohesive (6% and 15% clay) sandy loam soils at prescribed bulk densities (1.30 to 1.70 Mg m^?3) and with a bank angle of 90° to investigate the controls on failure mechanisms due to seepage forces. A dimensionless seepage mechanism (SM) number was derived and evaluated based on the ratio of resistive cohesion forces to the driving forces leading to instability including seepage gradients with an assumed steady‐state seepage angle. Tension failures and undercutting were both observed dependent primarily on the saturated hydraulic conductivity, effective cohesion, and seepage gradient. Also, shapes of seepage undercuts for these more cohesive soils were wider and less deep compared to undercuts in sand and loamy sand soils. Direct shear tests were used to quantify the geotechnical properties of the soils packed at the various bulk densities. The SM number reasonably predicted the seepage failure mechanism (tension failure versus undercutting) based on the geotechnical properties and assumed steady‐state seepage gradients of the physical‐scale laboratory experiments, with some uncertainty due to measurement of geotechnical parameters, assumed seepage gradient direction, and the expected width of the failure block. It is hypothesized that the SM number can be used to evaluate seepage failure mechanisms when a streambank or hillslope experiences steady‐state seepage forces. When prevalent, seepage gradient forces should be considered when analyzing bank stability, and therefore should be incorporated into commonly used stability models. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Laboratory soil piping and internal erosion experiments: evaluation of a soil piping model for low‐compacted soils          下载免费PDF全文

Garey A. Fox  Rachel G. Felice  Taber L. Midgley  Glenn V. Wilson  Abdul‐Sahib T. Al‐Madhhachi 《地球表面变化过程与地形》2014,39(9):1137-1145

Mechanistic models have been proposed for soil piping and internal erosion on well‐compacted levees and dams, but limited research has evaluated these models in less compacted (more erodible) soils typical of hillslopes and streambanks. This study utilized a soil box (50 cm long, 50 cm wide and 20 cm tall) to conduct constant‐head, soil pipe and internal erosion experiments for two soils (clay loam from Dry Creek and sandy loam from Cow Creek streambanks) packed at uniform bulk densities. Initial gravimetric moisture contents prior to packing were 10, 12 and 14% for Dry Creek soil and 8, 12, and 14% for Cow Creek soil. A 1‐cm diameter rod was placed horizontally along the length of the soil bed during packing and carefully removed after packing to create a continuous soil pipe. A constant head was maintained at the inflow end. Flow rates and sediment concentrations were measured from the pipe outlet. Replicate submerged jet erosion tests (JETs) were conducted to derive erodibility parameters for repacked samples at the same moisture contents. Flow rates from the box experiments were used to calibrate the mechanistic model. The influence of the initial moisture content was apparent, with some pipes (8% moisture content) expanding so fast that limited data was collected. The mechanistic model was able to estimate equivalent flow rates to those observed in the experiments, but had difficulty matching observed sediment concentrations when the pipes rapidly expanded. The JETs predicted similar erodibility coefficients compared to the mechanistic model for the more erodible cases but not for the less erodible cases (14% moisture content). Improved models are needed that better define the changing soil pipe cross‐section during supply‐ and transport‐limited internal erosion, especially for piping through lower compacted (more erodible) soils as opposed to more well‐compacted soils resulting from constructing levees and dams. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Model of particulate organic carbon transport in an agriculturally impacted stream   总被引：1，自引：0，他引：1       下载免费PDF全文

William I. Ford  James F. Fox 《水文研究》2014,28(3):662-675

The present contribution focuses on modeling the total particulate organic carbon (POC) and benthic POC transport from a lowland stream impacted by agricultural land‐use. A mass balance, reach scale model is verified that accounts for water, sediment and POC transport, sediment and POC temporary storage and exchange with the streambed, and production and degradation of carbon pools in the benthos. We found that the POC load is highly variable during individual hydrologic events and is influenced by transport of mixed carbon sources including upland, streambank and benthic POC sources. Benthic POC stocks and transport were found to vary seasonally and annually but are in a state of long‐term equilibrium. Equilibrium is governed by negative feedback mechanisms whereby high POC export due to extreme hydrologic events and high‐frequency hydrologic events reduces benthic POC stocks and inhibits benthic POC growth. Benthic POC accounted for 4 tC y^?1 or 22% of the total annual POC loading in the stream's main stem and 8.9 tC y^?1 or 48% of the POC yield for the entire watershed. These results suggest that further attention should be given to benthic‐derived POC when budgeting stream ecosystem carbon for low‐order stream systems. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Living a century in warm thermal conditions: introduced populations of Pumpkinseed (Lepomis gibbosus) inhabiting the Iberian Peninsula (Spain) show reduced adaptation to North American winter conditions     

Anna C. Rooke  Michael G. Fox 《Aquatic Sciences - Research Across Boundaries》2014,76(4):497-509

In this study, we demonstrate that non-native Pumpkinseed (Lepomis gibbosus) introduced into Spanish water-bodies almost 100 years ago have a reduced capacity to tolerate winter conditions typically experienced by northern native populations. Overwinter survival and changes in lean weight and lipid content of Pumpkinseed from artificial colonies established from two Canadian and two Iberian source populations were compared under winter conditions typically experienced in the northern native range. Adult survival in outdoor ponds was higher in Canadian populations (68 and 78 %) than Iberian populations (31 and 49 %). Under simulated winter conditions in the laboratory, juvenile Iberian Pumpkinseed experienced higher mortality earlier in the winter period than Canadian populations. Lipid content of Iberian juveniles decreased on average by 49 % during the first half of the winter, while that of Canadian populations decreased by only 12–20 %. These results indicate that Iberian Pumpkinseed have lower tolerance of winter conditions relative to native Canadian populations, and suggest that relatively short exposure to warm climates can result in adaptive change in the physiology and bioenergetics of wild fish populations.  相似文献