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1.
Oladele Samuel Ajayi 《Radiation and environmental biophysics》2009,48(3):323-332
Activity concentrations of the selected radionuclides 40K, 226Ra and 232Th were measured in surface soil samples collected from 38 cities in the southwest region of Nigeria by means of gamma spectroscopy
with a high-purity germanium detector. Measured activity concentration values of 40K varied from 34.9 ± 4.4 to 1,358.6 ± 28.5 Bq kg−1 (given on a dry mass (DM) basis) with a mean value of 286.5 ± 308.5 Bq kg−1; that of 226Ra varied from 9.3 ± 3.7 to 198.1 ± 13.8 Bq kg−1 with a mean value of 54.5 Bq kg−1 and a standard deviation of 38.7 Bq kg−1, while that of 232Th varied from 5.4 ± 1.1 to 502.0 ± 16.5 Bq kg−1 with a mean value of 91.1 Bq kg−1 and standard deviation of 100.9 Bq kg−1. The mean activity concentration values obtained for 226Ra and 232Th are greater than the world average values reported by the United Nations Scientific Committee on Effects of Atomic Radiation
for areas of normal background radiation. Radiological indices were estimated for the radiation/health hazards of the natural
radioactivity of all soil samples. Estimated absorbed dose rates in air varied from 12.42 ± 2.25 to 451.33 ± 19.06 nGy h−1, annual outdoor effective dose rates from 0.015 ± 0.003 to 0.554 ± 0.023 mSv year−1, internal hazard index from 0.10 ± 0.03 to 3.02 ± 0.16, external hazard index from 0.07 ± 0.01 to 2.60 ± 0.11, representative
level index from 0.19 ± 0.03 to 6.84 ± 0.29, activity index from 0.09 ± 0.02 to 3.42 ± 0.15, and radium equivalent activity
from 26.95 ± 5.04 to 963.15 ± 41.87 Bq kg−1. Only the mean value of the representative level index exceeds the limit for areas of normal background radiation. All other
indices show mean values that are lower than the recommended limits. 相似文献
2.
J. W. Mietelski M. A. Olech K. Sobiech-Matura B. J. Howard P. Gaca M. Zwolak S. Błażej E. Tomankiewicz 《Polar Biology》2008,31(9):1081-1089
There are few data reported on radionuclide contamination in Antarctica. The aim of this paper is to report 137Cs, 90Sr and 238,239+240Pu and 40K activity concentrations measured in biological samples collected from King George Island (Southern Shetlands, Antarctica),
mostly during 2001–2002. The samples included: bones, eggshells and feathers of penguin Pygoscelis papua, bones and feathers of petrel Daption capense, bones and fur of seal Mirounga leonina, algae Himantothallus grandifolius, Desmarestia anceps and Cystosphaera jacquinotii, fish Notothenia corriceps, sea invertebrates Amphipoda, shells of limpet Nacella concina, lichen Usnea aurantiaco-atra, vascular plants Deschampsia antarctica and Colobanthus quitensis, fungi Omphalina pyxidata, moss Sanionia uncinata and soil. The results show a large variation in some activity concentrations. Samples from the marine environment had lower
contamination levels than those from terrestrial ecosystems. The highest activity concentrations for all radionuclides were
found in lichen and, to a lesser extent, in mosses, probably because lichens take up atmospheric pollutants and retain them.
The only significant correlation (except for that expected between 238Pu and 239+240Pu) was noted for moss and lichen samples between plutonium and 90Sr. A tendency to a slow decrease with time seems to be occurring. Analyses of the activity ratios show varying fractionation
between various radionuclides in different organisms. Algae were relatively more highly contaminated with plutonium and radiostrontium,
and depleted with radiocesium. Feathers had the lowest plutonium concentrations. Radiostrontium and, to a lesser extent, Pu
accumulated in bones. The present low intensity of fallout in Antarctic has a lower 238Pu/239+240Pu activity ratio than that expected for global fallout. 相似文献
3.
This article evaluates the health risk raised by exposure to naturally occurring radionuclides in soil around Khak-Sefid, Ramsar, Iran, which is an area of high natural background radiation. A high purity germanium detector was used to determine levels of radionuclides in soil samples and the cancer morbidity risk for a hypothetical resident farmer was evaluated using the RESidual RADioactivity (RESRAD) code. The average activity concentrations of 226Ra, 232Th, and 40K were found to be 13,201 ± 391, 27.9 ± 2.4, and 415.5 ± 16 Bq/kg, respectively. The maximum assessed cancer morbidity risks were calculated from external and internal exposure pathways as 4.73 × 10?2 and 3.40 × 10?2 for 226Ra, 1.41 × 10?4 and 7.88 × 10?5 for 232Th, and 1.3 × 10?4 and 4.233 × 10?4 for 40K. The RESRAD calculations also showed total cancer morbidity risks from external gamma and plant ingestion pathways were more important than from other exposure pathways. A sensitivity analysis was also performed to determine the input parameter values in the risk assessment process. In general, due to the high calculated risk of 226Ra compared with 232Th and 40K it can be the major source of concern for human heath in the study area. 相似文献
4.
5.
S. O. Dodonova N. A. Krupenina A. A. Bulychev 《Biochemistry (Moscow) Supplemental Series A: Membrane and Cell Biology》2010,4(4):389-396
Photosynthesizing cells of characean algae exposed to light are able to produce pH bands corresponding to alternate areas
with dominant H+-pump activity and high H+-conductance of the cell membrane. The action potential generation temporally arrests the counter-directed H+ fluxes, which gives rise to opposite pH shifts in different cell regions and represents a suitable indicator for activities
of the plasma membrane H+-transporting systems. Measurements of pH near the cell surface by means of microelectrodes and microspectrophotometry in
the presence of pH-indicating dye thymol blue have shown that the treatment of cells with dithiothreitol (SH-group reducing
agent) suppresses pH changes induced by the action potential generation in the alkaline cell areas and considerably increases
the concurrent pH changes in the acid regions. Measurements of plasma membrane resistance in the alkaline zones revealed that
dithiothreitol inhibits the light-dependent conductance of the resting cell and diminishes the conductance inactivation caused
by the action potential generation. The data suggest that the reduction of accessible disulfide bonds results in the decrease
of H+-conductance, whereas the activity of plasma membrane H+-pump remains unimpaired or is even enhanced. 相似文献
6.
Great deal of work has been devoted to determine doses from alpha particles emitted by 222Rn and 220Rn progeny. In contrast, contribution of beta particles to total dose has been neglected by most of the authors. The present
work describes a study of the detriment of 222Rn and 220Rn progeny to the human lung due to beta particles. The dose conversion factor (DCF) was introduced to relate effective dose
and exposure to radon progeny; it is defined as effective dose per unit exposure to inhaled radon or thoron progeny. Doses
and DCFs were determined for beta radiation in sensitive layers of bronchi (BB) and bronchioles (bb), taking into account
inhaled 222Rn and 220Rn progeny deposited in mucus and cilia layer. The nuclei columnar secretory and short basal cells were considered to be sensitive
target layers. For dose calculation, electron-absorbed fractions (AFs) in the sensitive layers of the BB and bb regions were
used. Activities in the fast and slow mucus of the BB and bb regions were obtained using the LUNGDOSE software developed earlier.
Calculated DCFs due to beta radiation were 0.21 mSv/WLM for 222Rn and 0.06 mSv/WLM for 220Rn progeny. In addition, the influence of Jacobi room parameters on DCFs was investigated, and it was shown that DCFs vary
with these parameters by up to 50%. 相似文献
7.
For assessment of external radiation doses to frogs in a wetland area contaminated with 137Cs, frog phantoms were constructed from polymethyl methacrylate (PMMA). The frog phantoms contained thermoluminescence (TL)
chips and were used in situ at two study sites to measure doses. To test if higher doses are received by the sensitive skin
of frogs, extra-thin TL chips were applied close to the surface of the frog phantoms. In addition, the measured doses were
compared with those calculated on the basis of soil sample data from the wetland multiplied with dose-conversion coefficients
from the US Department of Energy’s RESRAD-BIOTA code and from the ERICA assessment tool. Measured doses were generally lower
than those calculated to ellipsoids used to model frogs. Higher doses were measured at the frog phantoms’ surfaces in comparison
to inner parts at one of the two sites indicating that the frogs’ thin skin could receive a higher radiation dose than expected.
In the efforts to assure protection of non-human biota, in situ measurements with phantoms provide valuable dose information
and input to dose models in site-specific risk assessments of areas contaminated with radionuclides. 相似文献
8.
Nutrient uptake by forest trees is dependent on ectomycorrhizal (EM) mycelia that grow out into the soil from the mycorrhizal root tips. We estimated the production of EM mycelia in root free samples of pure spruce and mixed spruce-oak stands in southern Sweden as mycelia grown into sand-filled mesh bags placed at three different soil depths (0–10, 10–20 and 20–30 cm). The mesh bags were collected after 12 months and we found that 590±70 kg ha–1 year–1 of pure mycelia was produced in spruce stands and 420±160 kg ha–1 year–1 in mixed stands. The production of EM mycelia in the mesh bags decreased with soil depth in both stand types but tended to be more concentrated in the top soil in the mixed stands compared to the spruce stands. The fungal biomass was also determined in soil samples taken from different depths by using phospholipid fatty acids as markers for fungal biomass. Subsamples were incubated at 20°C for 5 months and the amount of fungal biomass that degraded during the incubation period was used as an estimate of EM fungal biomass. The EM biomass in the soil profile decreased with soil depth and did not differ significantly between the two stand types. The total EM biomass in the pure spruce stands was estimated to be 4.8±0.9×103 kg ha–1 and in the mixed stands 5.8±1.1×103 kg ha–1 down to 70 cm depth. The biomass and production estimates of EM mycelia suggest a very long turnover time or that necromass has been included in the biomass estimates. The amount of N present in EM mycelia was estimated to be 121 kg N ha–1 in spruce stands and 187 kg N ha–1 in mixed stands. The 13C value for mycelia in mesh bags was not influenced by soil depth, indicating that the fungi obtained all their carbon from the tree roots. The 13C values in mycelia collected from mixed stands were intermediate to values from pure spruce and pure oak stands suggesting that the EM mycelia received carbon from both spruce and oak trees in the mixed stands. The 15N value for the EM mycelia and the surrounding soil increased with soil depth suggesting that they obtained their entire N from the surrounding soil. 相似文献
9.
Duraffourg N Choudens SO Fontecave M Loiseau L Barras F Marion D Blanchard L 《Journal of biomolecular NMR》2004,30(3):379-380
10.
Aims
Poorly drained arctic ecosystems are potential large emitters of methane (CH4) due to their high soil organic carbon content and low oxygen availability. In wetlands, aerenchymatous plants transport CH4 from the soil to the atmosphere, but concurrently transport O2 to the rhizosphere, which may lead to oxidation of CH4. The importance of the latter process is largely unknown for arctic plant species and ecosystems. Here, we aim to quantify the subsurface oxidation of CH4 in a waterlogged arctic ecosystem dominated by Carex aquatilis ssp. stans and Eriophorum angustifolium, and evaluate the overall effect of these plants on the CH4 budget.Methods
A mesocosms study was established based on the upper 20 cm of an organic soil profile with intact plants retrieved from a peatland in West Greenland (69°N). We measured dissolved concentrations and emissions of 13CO2 and 13CH4 from mesocosms during three weeks after addition of 13C-enriched CH4 below the mesocosm.Results
Most of the recovered 13C label (>98 %) escaped the ecosystem as CH4, while less than 2 % was oxidized to 13CO2.Conclusions
It is concluded that aerenchymatous plants control the overall CH4 emissions but, as a transport system for oxygen, are too inefficient to markedly reduce CH4 emissions.11.
Ana Paula Madeira Di Beneditto Roberto Weider de Assis Franco 《Journal of biological physics》2018,44(3):471-482
The Mn2+ concentrations in the sagittae otoliths of 12 fish families (and 19 species) that co-occur in a coastal area of southeastern Brazil (~21°S) were quantified using electron paramagnetic resonance (EPR). Inferences were made about the relationship between fish habitat and trace element incorporation. Inferences were made on the relationship between trace element concentration and otolith shape. The differences in Mn2+ concentrations among the species suggest that habitat (and feeding habits) might drive the incorporation of this trace element into fish otoliths, with higher values in bottom-associated fish species than in surface-associated species. In surface-associated fish species, the correlation between trace element concentrations and otolith shape was stronger than in bottom-associated species. Thus, while the Mn bioavailability in a fish’s habitat, especially from feeding resources, is a local driving influence of trace element incorporation in sagittae otoliths, species-specific requirements also have an influence. Quantitative EPR is a non-destructive technique that is very useful when the available samples cannot be damaged, like with otolith collections. 相似文献
12.
Kurata A Uchimura K Shimamura S Kobayashi T Horikoshi K 《Applied microbiology and biotechnology》2007,77(2):311-319
The acpI gene encoding an alkaline protease (AcpI) from a deep-sea bacterium, Alkalimonas collagenimarina AC40T, was shotgun-cloned and sequenced. It had a 1,617-bp open reading frame encoding a protein of 538 amino acids. Based on analysis
of the deduced amino acid sequence, AcpI is a subtilisin-like serine protease belonging to subtilase family A. It consists
of a prepropeptide, a catalytic domain, and a prepeptidase C-terminal domain like other serine proteases from the genera Pseudomonas, Shewanella, Alteromonas, and Xanthomonas. Heterologous expression of the acpI gene in Escherichia coli cells yielded a 28-kDa recombinant AcpI (rAcpI), suggesting that both the prepropeptide and prepeptidase C-terminal domains
were cleaved off to give the mature form. Analysis of N-terminal and C-terminal amino acid sequences of purified rAcpI showed
that the mature enzyme would be composed of 273 amino acids. The optimal pH and temperature for the caseinolytic activity
of the purified rAcpI were 9.0–9.5 and 45°C in 100 mM glycine–NaOH buffer. Calcium ions slightly enhanced the enzyme activity
and stability. The enzyme favorably hydrolyzed gelatin, collagen, and casein. AcpI from A. collagenimarina AC40T was also purified from culture broth, and its molecular mass was around 28 kDa, indicating that the cleavage manner of the
enzyme is similar to that in E. coli cells. 相似文献
13.
Garçon DP Lucena MN França JL McNamara JC Fontes CF Leone FA 《The Journal of membrane biology》2011,244(1):9-20
We investigated the effect of the exogenous polyamines spermine, spermidine and putrescine on modulation by ATP, K+, Na+, NH4
+ and Mg2+ and on inhibition by ouabain of posterior gill microsomal Na+,K+-ATPase activity in the blue crab, Callinectes ornatus, acclimated to a dilute medium (21‰ salinity). This is the first kinetic demonstration of competition between spermine and
spermidine for the cation sites of a crustacean Na+,K+-ATPase. Polyamine inhibition is enhanced at low cation concentrations: spermidine almost completely inhibited total ATPase
activity, while spermine inhibition attained 58%; putrescine had a negligible effect on Na+,K+-ATPase activity. Spermine and spermidine affected both V and K for ATP hydrolysis but did not affect ouabain-insensitive ATPase activity. ATP hydrolysis in the absence of spermine and
spermidine obeyed Michaelis–Menten behavior, in contrast to the cooperative kinetics seen for both polyamines. Modulation
of V and K by K+, Na+, NH4
+ and Mg2+ varied considerably in the presence of spermine and spermidine. These findings suggest that polyamine inhibition of Na+,K+-ATPase activity may be of physiological relevance to crustaceans that occupy habitats of variable salinity. 相似文献
14.
High-affinity K+ transporters play an important role in K+ absorption of plants. We isolated a HAK gene from Aeluropus littoralis, a graminaceous halophyte. The amino acid sequence of AlHAK showed high homology with HAK transporters obtained from Oryza sativa (82%) and Hordeum vulgare (82%). When expressed in Saccharomyces cereviae WΔ3, AlHAK performed high-affinity K+ uptake with a Km value of 8 μM, and the growth of transformants was dramatically inhibited by 150 mM Rb+ and 150 mM Cs+ but less affected by 300 mM Na+. AlHAK may thus improve the capacity of plants to maintain a high cytosolic K+/Na+ ratio at high salinity. 相似文献
15.
Evidence Of Botanical Diversity and Species Continuity from Chancay Sites in The Huaura Valley, Peru. This study reports on new botanical evidence from the north-central coast of Peru. The material dates to the Late Intermediate Period (approximately CE 1100–1435) and is from archaeological excavation at the sites of Rontoy, Quipico, and Chambara located in the Huaura Valley. All three sites belong to what has been defined as the Chancay culture. The diversity of species present is consistent with the plants utilized in the region beginning in the Preceramic Period. Data also show differential distribution of plant taxa by site that cannot be explained by ecological zone or site location. 相似文献
16.
The capture of patchily distributed nutrients by tree roots has received extensive research, but the fate of those nutrients has not. We performed experiments to determine if nutrient transport within tree species is preferentially transported from specific roots to specific branches. Saplings of five species with contrasting growth requirements were examined: two Betula species (B. papyrifera and B. lenta), Populus tremuloides, and two Acer species (A. saccharum and A. rubrum). To quantify patterns of long-distance transport, we examined the accumulation of safranin-O dye and 15N in branches when these tracers were applied to isolated lateral roots (dye and 15N) and to the main root system (15N). Because transport of nutrients between sectors requires flow through intervessel pit pairs of adjacent xylem vessel elements, we quantified the area of intervessel pits, the number of pits per unit vessel wall area, and the % vessel wall area as pits in Acer and Betula. We found that the two Betula species were integrated (tracers applied to isolated roots were likely to accumulate in all branches), while P. tremuloides and the two Acer species were sectorial (tracer accumulation was more concentrated in particular branches). Betula had the largest number of intervessel pits per unit vessel wall area and the largest percentage of vessel wall area as pits. The high density of bordered pits may explain the ease of tracer movement throughout the two Betula species. Greater integration may allow certain trees (e.g., Betula) to exploit nutritionally patchy environments such as rocky soils, and may alter plant-herbivore interactions. 相似文献
17.
The paper presents the result of analysis of charred food on the interior part of the vessels from the graves of the East Manych and West Manych Catacomb archaeological cultures (2500–2350 cal bc). The phytolith and pollen analyses identified pollen of wild steppe plants and phytoliths of domesticated gramineous plants determined as barley phytoliths. Direct 14С dating of one of the samples demonstrates that barley spikelets and stems were used in funeral rites by local steppe communities. However, there are no data suggesting that steppe inhabitants of the Lower Don Region were engaged in agriculture in the mid-3000 bc. Supposedly, barley could have reached the steppes through seasonal migrations of mobile pastoralists to the south, use of North Caucasus grasslands in the economic system of seasonal moves and exchange with local people. Nevertheless, presence of carbonized barley seeds in the occupation layers at North Caucasus settlements of 4000–3000 bc requires confirmation by direct 14С dating of such samples. 相似文献
18.
We here present a novel method, based on the targeting of the photoprotein aequorin, for measuring the concentration of Ca2+ ions in defined cellular compartments of intact cells. In this contribution we will discuss the application to mitochondria. A chimaeric cDNA was constructed by fusing in frame the aequorin cDNA with that for a mitochondrial protein. The cDNA encoded a “mitochondrially-targeted” aequorin, composed of a typical mitochondrial targeting signal at the N-terminus and the photoprotein at the C-terminus. The cDNA, inserted in the expression vector pMT2, was co-transfected into bovine endothelial and HeLa cells together with the selectable plasmid pSV2-neo and stable transfectants, selected for high aequorin production, were analyzed. In subcellular fractionations, aequorin was shown to be localized in mitochondria; in intact cells, the first direct measurement of mitochondrial free Ca2+, [Ca2+]m, were obtained, which showed that [Ca2+]m is low at rest (<0.5 μM), but rapidly increases to the micromolar range upon cell stimulation [1]. These data indicate that mitochondria “sense” very accurately the cytosolic Ca2+ concentration ([Ca2+]i), and after cell stimulation [Ca2+]m rises to values capable of activating the Ca2+-sensitive mitochondrial dehydrogenases. 相似文献
19.
A. K. Rai R. Chakravorty Jaishree Paul 《World journal of microbiology & biotechnology》2008,24(12):2879-2887
This study was conducted to evaluate the load of three food- and water-borne parasites, namely, Giardia, Entamoeba, and Cryptosporidium on food items that are consumed either raw or in an unprocessed state in the northern parts of India. A two-step diagnostic method was employed to assess the presence of Giardia and Cryptosporidium, the immunofluorescence assay (IFA) combined with the polymerase chain reactiion (PCR assay), whereas a Tech lab diagnostic kit in combination with PCR assay was used for accurate detection of Entamoeba histolytica in the samples. The methods for isolation and enrichment of cysts/oocysts from the various food items were tested and discussed here. Our results showed that the overall spectrum of incidence of the three parasites on food items in decreasing order were Giardia > Entamoeba > Cryptosporidium. When data were subjected to the chi-square test, the prevalence of all three parasites was found to be independent of the food items. To determine whether the presence of two types of parasites in a food item is uniform, a Poisson distribution test was conducted. On comparing the intensity of occurrence of the different parasites in various food items, it was observed that the occurrence of Giardia and Entamoeba was not of the same order at 5% level of significance only in case of samples of raw meat and milk. This confirmed that a high number of raw or unpasteurized milk and meat samples are more likely to be contaminated with Giardia than with Entamoeba. Therefore, our observations point to the unhygienic practices of food handlers being a major contributor in the transmission of parasites to unprocessed food products. 相似文献
20.
Van Damme V Gómez-Paniagua H de Vicente MC 《Molecular breeding : new strategies in plant improvement》2011,28(4):597-610
Crop genetic resources carry variation useful for overcoming the challenges of modern agriculture. Molecular markers can facilitate
the selection of agronomically important traits. The pervasiveness of genomics research has led to an overwhelming number
of publications and databases, which are, nevertheless, scattered and hence often difficult for plant breeders to access,
particularly those in developing countries. This situation separates them from developed countries, which have better endowed
programs for developing varieties. To close this growing knowledge gap, we conducted an intensive literature review and consulted
with more than 150 crop experts on the use of molecular markers in the breeding program of 19 food security crops. The result
was a list of effectively used and highly reproducible sequence tagged site (STS), simple sequence repeat (SSR), single nucleotide
polymorphism (SNP), and sequence characterized amplified region (SCAR) markers. However, only 12 food crops had molecular
markers suitable for improvement. That is, marker-assisted selection is not yet used for Musa spp., coconut, lentils, millets, pigeonpea, sweet potato, and yam. For the other 12 crops, 214 molecular markers were found
to be effectively used in association with 74 different traits. Results were compiled as the GCP Molecular Marker Toolkit, a free online tool that aims to promote the adoption of molecular approaches in breeding activities. 相似文献