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971.
972.
Ingestion of a chelating agent (ethylenediaminetetraacetic acid) by female rats during pregnancy impaired reproduction and resulted in congenitally malformed young. When ethylenediaminetetraacetic acid was fed from days 6 to 21 of gestation, all of the full-term young had gross congenital malformations. These effects were prevented by simultaneous supplementation with 1000 parts per million of dietary zinc. 相似文献
973.
Fertilizer nitrogen: contribution to nitrate in surface water in a corn belt watershed 总被引:15,自引:0,他引:15
Measurements of nitrate concentration and relative enrichment in nitrogen-15 were made on samples of the surface waters of a typical Illinois corn belt watershed and the effluent of the subterranean tiles that drain the cropped land in the region. From these measurements, we estimate that at the time of peak nitrate concentration in the spring of 1970 a minimum of 55 to 60 percent of the nitrogen found as nitrate in the surface waters of this watershed originated from fertilizer nitrogen 相似文献
974.
Galactose-fed chicks have been found to develop severe hyperosmolar dehydration. Although biochemical abnormalities have been observed in the brain of the galactose-toxic chick, the observed physiologic alteration of serum osmolality could be the major factor responsible for the galactose toxicity syndrome in the chick. 相似文献
975.
Buffer combinations for mammalian cell culture 总被引:30,自引:0,他引:30
H Eagle 《Science (New York, N.Y.)》1971,174(8):500-503
The growth and metabolism of cultured mammalian cells are markedly affected by the pH variation in ordinary hicarbonate-buffered media (pH 8.0 to 6.9). Those pH swings can be reduced and the pH of the culture can be stabilized as desired in the range pH 6.4 to 8.3 by appropriate combinations of two or three organic buffers, each at 10 to 15 millimolar, in conjunction with phosphate and bicarbonate. The initial alkalinization in sparse cultures is then minimized, and the metabolic acidificatiotn in 24 hours is usually less than 0.4 pH unit except in heavy cultutres. 相似文献
976.
977.
Peatlands are highly valued for their range of ecosystem services, including distinctive biodiversity, agricultural uses, recreational amenities, water provision, river flow regulation and their capacity to store carbon. There have been a range of estimates of carbon stored in peatlands in the United Kingdom, but uncertainties remain, in particular with regard to depth and bulk density of peat. In addition, very few studies consider the full profile with depth in carbon auditing. The importance of sub‐peat soils within peatland carbon stores has been recognized, but remains poorly understood and is included rarely within peatland carbon audits. This study examines the importance of the carbon store based on a study of blanket peat on Dartmoor, UK, by estimating peat depths in a 4 × 1 km survey area using ground penetrating radar (GPR), extraction of 43 cores across a range of peat depth, and estimation of carbon densities based on measures of loss‐on‐ignition and bulk density. Comparison of GPR estimates of peat depth with core depths shows excellent agreement, to provide the basis for a detailed understanding of the distribution of peat depths within the survey area. Carbon densities of the sub‐peat soils are on average 78 and 53 kg C/m3 for the overlying blanket peat. There is considerable spatial variability in the estimates of total carbon from each core across the survey area, with values ranging between 56.5 kg C/m2 (1.01 m total depth of peat and soil) and 524 kg C/m2 (6.63 m total depth). Sub‐peat soil carbon represents between 4 and 28 per cent (mean 13.5) of the total carbon stored, with greater values for shallower peat. The results indicate a significant and previously unaccounted store of carbon within blanket peat regions which should be included in future calculations of overall carbon storage. It is argued that this store needs to be considered in carbon audits. 相似文献
978.
Biochar is obtained by the pyrolysis of biomass, and contains abundant carbon and minerals. Biochar supplementation of soils can greatly improve soil health and quality, but these beneficial effects typically develop slowly over time. Depending on the quality of the biochar and the soil to which it is applied, it may take years before positive effects are apparent. This is because organic substances are slowly sorbed onto the biochar over time, and the biochar eventually becomes part of the sorption complex of the soil. It is therefore advisable to apply biochar together with some organic material. We examined the effect of co-application of different doses of biochar with manure on soil dehydrogenase activity (DHA), soil oxidizable carbon (COX), cumulative soil respiration, soil buffering capacity, the soil exchange reaction (pH/KCl) and the production yield of winter rape seeds. We also determined seed production when artificial granular fertilizers were added to biochar and manure. The results showed that the application of biochar and manure significantly increased grain yield, DHA, the soil exchange reaction and cumulative respiration. Thus, application of biochar with organic material can increase seed yield and some properties of agricultural soils. However, the positive effect of biochar on seed yield was not directly proportional to biochar dose, in that the seed yield was lower for a biochar dose of 45 t/ha than 30 t/ha. 相似文献
979.
Kies AK De Jonge LH Kemme PA Jongbloed AW 《Journal of agricultural and food chemistry》2006,54(5):1753-1758
The interaction between protein and phytate was investigated in vitro using proteins extracted from five common feedstuffs and from casein. The appearance of naturally present soluble protein-phytate complexes in the feedstuffs, the formation of complexes at different pHs, and the degradation of these complexes by pepsin and/or phytase were studied. Complexes of soluble proteins and phytate in the extracts appeared in small amounts only, with the possible exception of rice pollards. Most proteins dissolved almost completely at pH 2, but not after addition of phytate. Phytase prevented precipitation of protein with phytate. Pepsin could release protein from a precipitate, but the rate of release was increased by phytase. Protein was released faster from a protein-phytate complex when phytase was added, but phytase did not hydrolyze protein. Protein was released from the complex and degraded when both pepsin and phytase were added. It appears that protein-phytate complexes are mainly formed at low pH, as occurs in the stomach of animals. Phytase prevented the formation of the complexes and aided in dissolving them at a faster rate. This might positively affect protein digestibility in animals. 相似文献
980.
In 2002, the Kentucky Farm Tractor Overturn Survey was administered, in which 6,063 randomly selected farm operators responded to questions that addressed the presence and use of seatbelts in the event of a tractor overturn. Data were analyzed to determine the proportion of seatbelt presence and use on tractors that overturned differentiated by whether they were equipped or not equipped with a rollover protective structure (ROPS). In 537 overturns reported for which the ROPS status was known, 92 involved ROPS-equipped tractors, of which 60 had a functioning seatbelt, and 19 operators of these tractors used the seatbelt that was present during the overturn. However, of the 445 overturns of non-ROPS tractors, eight had a functioning seatbelt, and three of these operators wore the seatbelt. Two of the three operators that wore seatbelts on non-ROPS tractors suffered a permanent disability. In contrast, of the 19 operators who wore a seatbelt on ROPS-equipped tractors, 18 experienced no or minor injuries, and one required outpatient care. Seatbelts are known to save lives but are a secondary safety device to ROPS, for ROPS alone saves lives and is a necessary pre-condition for seatbelt presence and use. 相似文献