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231.
D S Smyly B B Woodward E C Conrad 《Journal of the Association of Official Analytical Chemists》1976,59(1):14-19
A reverse phase high-pressure liquid chromatographic method is presented for the simultaneous separation and determination of sacchrain, sodium benzoate, and caffeine in soft drinks, fruit juices, fruit cocktails, fruit punches, coffee, and artificial sweetener concentrates. Decarbonated soft drinks, fruit punches, and artificial sweetener concentrates are injected directly into the chromatograph. Fruit juices and coffee solutions require filtration through a 0.45 mum pore membrane filter prior to injection. Samples are eluted from a mu-Bondapak/C18 column with 5% glacial acetic acid and are quantitated with an ultraviolet detector. The results of saccharin, sodium benzoate, and caffeine determinations in 34 soft drinks (representing 11 manufacturers and 20 flavors); 8 fruit juices, cocktails, and punches; 7 coffees; and 6 artificial sweetener concentrates are presented. Average recoveries of saccharin, sodium benzoate, and caffeine from soft drinks are 99.0, 99.3, and 100.2%, respectively. 相似文献
232.
Methane oxidation in the soil surface layer of a flooded rice field and the effect of ammonium 总被引:15,自引:0,他引:15
Summary The CH4 flux from intact soil cores of a flooded rice field in Italy was measured under aerobic and anaerobic incubation conditions. The difference between the anaerobic and aerobic CH4 fluxes was apparently due to CH4 oxidation in the oxic soil surface layer. This conclusion was supported by measurements of the vertical CH4 profile in the upper 2-cm layer, and of the V
max of CH4 oxidation in slurried samples of the soil surface layer. About 80% of the CH4 was oxidized during its passage through the soil surface layer. CH4 oxidation was apparently limited by the concentration of CH4 and/or O2 in the active surface layer. The addition of ammonium to the water layer on top of the soil core reversibly increased the aerobic CH4 fluxes due to inhibition of CH4 oxidation in the soil surface layer. 相似文献
233.
Bai Y Rahman MS Perera CO Smith B Melton LD 《Journal of agricultural and food chemistry》2002,50(11):3179-3185
The structure of heat pump dried apple slices, developed as a function of air temperature and constant humidity, was studied by measuring porosity and using electron microscopy. The porosity of the apple rings increased linearly when the moisture content decreased during drying and then reached a constant value. In all dried apple slices, a degree of cellular collapse occurred. Case hardening occurred in the surface of the dried tissue when the apple slices were dried at 40-45 and 60-65 degrees C, and in the extreme case (at 60-65 degrees C) cracks were formed on the surface. 相似文献
234.
Soils are a major source of atmospheric NO and N2O. Since the soil properties that regulate the production and consumption of NO and N2O are still largely unknown, we studied N trace gas turnover by nitrification and denitrification in 20 soils as a function
of various soil variables. Since fertilizer treatment, temperature and moisture are already known to affect N trace gas turnover,
we avoided the masking effect of these soil variables by conducting the experiments in non-fertilized soils at constant temperature
and moisture. In all soils nitrification was the dominant process of NO production, and in 50% of the soils nitrification
was also the dominant process of N2O production. Factor analysis extracted three factors which together explained 71% of the variance and identified three different
soil groups. Group I contained acidic soils, which showed only low rates of microbial respiration and low contents of total
and inorganic nitrogen. Group II mainly contained acidic forest soils, which showed relatively high respiration rates and
high contents of total N and NH4
+. Group III mainly contained neutral agricultural soils with high potential rates of nitrification. The soils of group I produced
the lowest amounts of NO and N2O. The results of linear multiple regression conducted separately for each soil group explained between 44–100% of the variance.
The soil variables that regulated consumption of NO, total production of NO and N2O, and production of NO and N2O by either nitrification or denitrification differed among the different soil groups. The soil pH, the contents of NH4
+, NO2
– and NO3
–, the texture, and the rates of microbial respiration and nitrification were among the important variables.
Received: 28 October 1999 相似文献
235.
Thermal habitat experienced by Atlantic salmon (Salmo salar L.) kelts in coastal Newfoundland waters
David G. Reddin Kevin D. Friedland Peter Downton J. Brian Dempson Conrad C. Mullins 《Fisheries Oceanography》2004,13(1):24-35
Thermal habitat was recorded by data storage tags (DSTs) applied to Atlantic salmon (Salmo salar L.) kelts during their seaward migration in the spring of 1998 at enumeration facilities in Highlands River, Humber River, Western Arm Brook, and Campbellton River, Newfoundland. In total, 139 DSTs were applied and data were downloaded from eleven of the recovered tags. The recovered tags had been applied at Highlands, Campbellton and Western Arm rivers and recovered in the coastal waters of Newfoundland and Québec and at the enumeration facilities at Highlands and Campbellton rivers. Water temperatures experienced by the fish were recorded for periods of 62–118 days at resolutions of 15–30 min. The data from the sea record on the DSTs were analysed for temperature patterns in relation to migration behaviour and diurnal movement of the fish. A variety of patterns were exhibited on the temperature records suggesting that the fish were behaving in various ways at different times. For Campbellton and Highlands fish over the course of some 24 h periods, night‐time temperatures changed little and were among the highest daily temperatures experienced by the fish, whereas daytime temperatures often showed dramatic and frequent shifts in temperature presumably as the fish rapidly and frequently changed depth. For the Western Arm Brook fish, rapid fluctuations in temperature occurred sometimes during the day and night without a consistent diurnal pattern. We also considered large‐scale aspects of the data by examining oceanographic conditions in relation to the temperatures recorded by the tags. 相似文献
236.
The rate of deposition of carotenoids in pen-reared coho salmon was investigated by the addition of known carotenoid levels to diets. The carotenoids added to the diets were derived from red crab (P. planipes), and a process is described for the preparation of a soya oil carotenoid concentrate. Using a 3-stage counter-current extraction process, extracts containing 155 mg/100 g oil were prepared from red crab (P. planipes). Oregon moist pellets containing 3, 6, and 9 mg carotenoid/100 g were prepared using these extracts and were fed to coho salmon (Oncorhynchus kisutch) for 120 days. The amount of carotenoid deposited in the flesh of the fish was related to the carotenoid content of the diet and to the weight of the fish. Fish fed diets containing 6 and 9 mg carotenoid/100 g for the same length of time contained 60% more flesh carotenoids than those fed 3 mg/100 g. In general, after 120 days of feeding, only those fish feeding on diets containing 6.0 and 9.0 mg carotenoid/100 g and weighing over 215 g were assessed as having good-to-excellent coloration. Analysis of the flesh showed that there was no correlation between its carotenoid and fat contents. 相似文献
237.
Jobst Conrad 《Land Degradation \u0026amp; Development》1990,2(1):57-68
Based on the findings from the research project: ‘Alternative Uses for Land and the New Farmworker—Segregation versus Integration’, this paper analyses broad lines of development and available options for rural areas in the European Community. Taking into account various limitations on agricultural, forestry, and nature conservation activities, the emergence of three agro-structural regional types is likely to occur:
- —rural areas with intensive agriculture;
- —rural areas constituting mainly agrarian-touristic peripheries, which exploit their endogenous development potentials on the basis of quasi-tourism
- —less-favoured areas with a tendency towards depopulation, which may serve as ecological balance areas.
238.
Felipe Schwahofer Landuci Douglas Fraga Rodrigues Alexandre Macedo Fernandes Philip Conrad Scott Luis Henrique da Silva Poersch 《Aquaculture Research》2020,51(8):3305-3322
Worldwide, the availability of suitable areas for aquaculture has become a significant concern. In Brazil, the former Ministry of Fisheries and Aquaculture (MPA) has begun to promote discussions and plan meetings on Local Mariculture Development Plans (PLDMs): a planning tool for the establishment of parks and aquatic areas. However, hundreds of groups and individuals still practice aquaculture awaiting a definitive license. This study aimed to serve as a tool to identify suitable sites for the installation of cobia cage farming and also to contribute to the PLDM zoning process. We created 27 criterion maps for marine fish farming. Their individual weights were assigned based on the best judgment of technicians, researchers and other stakeholders using the pair‐wise comparison method. The criteria and their weights were combined using multi‐criteria decision rules, and a final map according to suitability was derived by reclassification. Of the total area, 54,663 ha (14%) were composed of restrictions, and 341,083 ha (86%) were found useful; of which <1% is considered top score. Even so, these are more than enough to ensure the growth of activity. In Rio de Janeiro state, two bays have suitable areas to marine fish culture development. To ensure the sustainability of marine fish farming, we suggested the adoption of limited production areas based on assimilation and production capacity. Through this methodological approach, it was possible to identify suitable areas for cobia farming development. Additionally, the results may serve as a useful tool on which the PLDM can be based on. 相似文献
239.
Carbon nanotube quantum resistors 总被引:1,自引:0,他引:1
The conductance of multiwalled carbon nanotubes (MWNTs) was found to be quantized. The experimental method involved measuring the conductance of nanotubes by replacing the tip of a scanning probe microscope with a nanotube fiber, which could be lowered into a liquid metal to establish a gentle electrical contact with a nanotube at the tip of the fiber. The conductance of arc-produced MWNTs is one unit of the conductance quantum G0 = 2e2/h = (12.9 kilohms)-1. The nanotubes conduct current ballistically and do not dissipate heat. The nanotubes, which are typically 15 nanometers wide and 4 micrometers long, are several orders of magnitude greater in size and stability than other typical room-temperature quantum conductors. Extremely high stable current densities, J > 10(7) amperes per square centimeter, have been attained. 相似文献
240.