Delta spots and great flares     

Harold Zirin  Margaret A. Liggett 《Solar physics》1982,113(1-2):267-283

Using eighteen years of observations at Big Bear, we summarize the development of δ spots and the great flares they produce. We find δ groups to develop in three ways: eruption of a single complex active region formed below the surface, eruption of large satellite spots near (particularly in front of) a large older spot, or collision of spots of opposite polarity from different dipoles. Our sample of twenty-one δ spots shows that once they lock together, they never separate, although rarely an umbra is ejected. The δ spots are already disposed to their final form when they emerge. The driving force for the shear is spot motion, either flux emergence or the forward motion of p spots in an inverted magnetic configuration. We observe the following phenomena preceding great flares:

1. δ spots, preferentially Types 1 and 2.
2. Umbrae obscured by Hα emission.
3. Bright Hα emission marking flux emergence and reconnection.
4. Greatly sheared magnetic configurations, marked by penumbral and Hα fibrils parallel to the inversion line.

We assert that with adequate spatial resolution one may predict the occurrence of great flares with these indicators.  相似文献   

    

Margaret Armstrong 《Mathematical Geology》1987,19(8):785-787

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Crustal attenuation for Jamaica, West Indies   总被引：1，自引：0，他引：1  

Margaret D. Wiggins-Grandison  Jens Havskov 《Journal of Seismology》2004,8(2):193-209

The S and coda wave spectra of small earthquakes on the island of Jamaica were used to determine the near surface and coda Q attenuation, and Q _c,respectively. Q _c determined by the single-station method was found in the range of 1 to 10 Hertz to be given by the relationship, Q _c= 60 ± 5f ^0.87±0.05. This suggests that the Jamaican crust is highly attenuating which is further supported by the observation of rapid intensity fall-off with distance for earthquakes that have affected the island in the past. , determined from S-wave spectra with short travel times was found to be 0.058 ± 0.012 on the central crustal block, which makes up nearly two-thirds of the island, and 0.080 ± 0.014 in surrounding belt sub-regions. The pattern of values seems to fit with the surface geology in that the central block has areas of exposed outcrops of older and harder rock than the belts, which are characterized by thicker sedimentary sequences as well as intense fracturing and faulting.Atkinson and Boore (1998) and Atkinson(2001) presented an alternative method to stochastic modelling for ground motion in Eastern North America, whereby California attenuation relationships were modified to account for crustal differences invelocity-depth profile, Q and between both regions. Following their example, the California spectral attenuation relation of Boore, Joyner and Fumal (1997) was modified to account for differences between the California and Jamaica crust, resulting in an attenuation relation that is deemed to be more appropriate for Jamaica. Spectral accelerations for Jamaica when compared to California, are especially reduced beyond 20 km from the source and at high frequencies, f 1 hertz.The study concludes that the Jamaican crust, although having an oceanic composition is highly attenuating, which may be a result of intensive tectonic processes, whereas is consistent with near-rock conditions on the central block and soft rock conditions elsewhere on the island.  相似文献   

Phosphorus distribution in sinking oceanic particulate matter   总被引：2，自引：1，他引：2  

Kristina L. Faul  Adina Paytan  Margaret L. Delaney 《Marine Chemistry》2005,97(3-4):307-333

Despite the recognition of the importance of phosphorus (P) in regulating marine productivity in some modern oceanic systems and over long timescales, the nature of particulate P within the ocean is not well understood. We analyzed P concentration in particulate matter from sediment traps and selected core tops from a wide range of oceanic regimes: open ocean environments (Equatorial Pacific, North Central Pacific), polar environments (Ross Sea, Palmer Deep), and coastal environments (Northern California Coast, Monterey Bay, Point Conception). These sites represent a range of productivity levels, temporal (seasonal to annual) distributions, and trap depths (200–4400 m). P associations were identified using an operationally defined sequential extraction procedure. We found that P in the sediment traps is typically composed of reactive P components including acid-insoluble organic P ( 40%), authigenic P ( 25%), and oxide associated and/or labile P ( 21%), with lesser proportions of non-reactive detrital P depending on location ( 13%). The concentrations and fluxes of all particulate P components except detrital P decrease or remain constant with depth between the shallowest and the deepest sediment traps, indicating some regeneration of reactive P components. Transformation from more labile forms of P to authigenic P is evident between the deepest traps and core top sediments. Although for most sites the magnitudes of reactive P fluxes are seasonally variable and productivity dependent, the fractional associations of reactive P are independent of season. We conclude that P is transported from the upper water column to the sediments in various forms previously considered unimportant. Thus, acid-insoluble organic P measurements (typically reported as particulate organic P) likely underestimate biologically related particulate P, because they do not include the labile, oxide-associated, or authigenic P fractions that often are or recently were biologically related. Organic C to reactive P ratios are typically higher than Redfield Ratio and are relatively constant with depth below 300 m suggesting that preferential regeneration of P relative to C occurs predominantly at shallow depths in the water column, but not deeper in the water column (> 300 m). The view of P cycling in the oceans should be revised (1) to include P fractions other than acid-soluble organic P as important carriers of reactive P in rapidly sinking particles, (2) to include the efficient transformation of labile forms of P to authigenic P in the water column as well as in sediments, and (3) to consider the occurrence of preferential P regeneration at very shallow depths.  相似文献   

Individual variation in patterns of benzo[a]pyrene metabolism in the marine fish scup (Stenotomus chrysops)     

John J. Stegeman  Margaret O. James 《Marine environmental research》1985,17(2-4)

The metabolism at specific sites on carcinogenic hydrocarbons such as benzo[a]pyrene (BP) is responsible for activation to the ultimate mutagens and carcinogens, and patterns of metabolism can thus influence the biological effect of such compounds. Marine fish are known to efficiently metabolize BP at the benzo-ring, forming high percentages of the 9,10-dihydrodiol (DHD) and 7,8-DHD, the latter including the penultimate carcinogen.^1,2 Hydrocarbon-induced cytochrome P-450 in fish is responsible for initiating metabolism on the benzo-ring, but epoxide hydrolase (EH) activity is required for DHD formation.^3,4 Both factors could influence formation of the DHD leading to the ultimate carcinogenic diol-epoxide. In the present study, patterns of BP metabolism were evaluated in a number of individual scup Stenotomus chrysops sampled from local Woods Hole waters, and a correlation is described between variation in the DHD formation and EH activity in these feral fish.  相似文献   

The Phytoplankton of the Menai Straits   总被引：1，自引：0，他引：1  

Jones  Margaret; Spencer  C. P. 《ICES Journal of Marine Science》1970,33(2):169-180

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Continental shelves : Edited by H. Postma and J.J. Zijlstra. Ecosystems of the World, 27. Elsevier, Amsterdam, 1988, x+421 pp., US$189.50/Dfl.360.00. Hardback. ISBN-0444-42609-4.     

Margaret Barnes 《Marine Chemistry》1989,26(4)

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Characterisation of choline esterases and their tissue and subcellular distribution in mussel (Mytilus edulis)     

Brown M  Davies IM  Moffat CF  Redshaw J  Craft JA 《Marine environmental research》2004,57(3):155-169

Acetylcholinesterase in mussel is potentially a useful biomarker of exposure to organophosphates (OP) in the marine environment. This study looked at cholinesterase activity in subcellular fractions of various tissues from the common mussel, Mytilus edulis. Measurement of enzyme rates demonstrated that although highest specific activity was found in foot 'mitochondrial' fraction, recovery of activity was very low. Gill 'microsomal' fraction had the second highest specific activity with a useful level of recovery and therefore was the most suitable tissue fraction for biomarker applications. Comparative studies of alternative alkylthiocholine substrates and competitive inhibitors suggest there is a single cholinesterase enzyme type present in this fraction. Inhibition of alkylcholine hydrolysis by BW284C51, specific to acetylcholinesterase in vertebrates, showed that cholinesterase activity in gill 'microsomal' fraction is inhibited by this compound but to a lesser extent than in vertebrate AChE. Inhibition of cholinesterase activity by azamethiphos in gill 'microsomal' fraction gave an IC50 of approximately 100 microM and showed both time and concentration dependence. However this indicates a lower potency compared to other animals and it is debatable whether mussel cholinesterase activity is useful as a biomarker of exposure in the field.  相似文献   

Identifying and Preventing Biopiracy in Australia: patent landscapes and legal geographies for plants with Indigenous Australian uses     

Daniel Robinson  Margaret Raven 《The Australian geographer》2017,48(3):311-331

There are legal and moral imperatives to protect biological resources and the ‘traditional knowledge’ associated with them. These imperatives derive from complex legal geographies: international law (such as the Convention on Biological Diversity and the Nagoya Protocol), State and federal laws, Indigenous customary law, codes of ethics and research protocols. This paper reports on a ‘patent landscape’ analysis of patents that refer to Australian plant species for which there is Indigenous Australian knowledge. We have identified several patents of potential new biopiracy concern. The paper highlights the way in which actors can gain private property monopolies over biological resources and associated traditional knowledge, even though there are overlapping sovereign rights and Indigenous rights claims. Regulatory gaps need to be closed nationally to fully govern the diverse human–plant bio-geographies in Australia. Further, Indigenous laws and governance have largely been ignored by these actors. We suggest that the introduction of ‘disclosure of origin’ requirements in patent applications, sui generis Indigenous knowledge protections, the development of biocultural protocols, and a more nationally consistent system for ‘access and benefit-sharing’ are required to ensure more ‘fair and equitable’ use of plants and Indigenous knowledge in/from Australia, and to ensure the recognition of Indigenous rights to knowledge.  相似文献   

The stream hydrology response of converting a headwater pasture catchment to Pinus radiata plantation     

Andrew O. Hughes  Rob Davies-Colley  Margaret Bellingham  Gareth van Assema 《新西兰海洋与淡水研究杂志》2020,54(3):308-328

ABSTRACT

The planting of degraded land with tree plantations may be effective at improving land use sustainability and profitability but it can also have significant effects on stream hydrology. In this paired catchment study, we report the stream hydrological response to partial (62%) afforestation of a steep pastoral catchment in the western Waikato Region, North Island, New Zealand. We comprehensively analyse the hydrological regime changes over a 23-year period (including eight years before pine planting) with reference to a native-forested ‘control’ catchment. Our results show that afforestation has markedly affected stream hydrology. Seven years after planting, the total annual runoff was 380?mm lower than predicted for the catchment in pasture. Two phases of plantation thinning resulted in the difference between measured and predicted runoff reducing to only 129?mm. Peak flows reduced by ～50% while total stormflow reduced by ～30% – which we attribute to canopy interception attenuating and delaying water yield. The impact of plantation establishment on low flows is not so clear, although afforestation appears to have reduced low flows by ～25%. This study provides information on the hydrological impact of afforestation within a hitherto poorly-represented New Zealand environment (i.e. high rainfall, sedimentary lithology-based, North Island hill country).  相似文献