Seasonal variation, effect plants

Total product costs are commonly calculated on one of three bases namely, daily basis, unit-of-product basis, or annual basis, The annual cost basis is probably the best choice for estimation of total cost because (1) the effect of seasonal variations is smoothed out, (2) plant on-stream time or equipment-operating factor is considered, (3) it permits more-rapid calculation of operating costs at less than full capacity, and (4) it provides a convenient way of considering infrequently occurring but large expenses such as annual turnaround costs in a refinery. 

The effects of seasonal variation in insolation levels on seasonal H2 supply/demand balances are presented in Fig. 2. The seasonal H2 production profile is well suited to meet seasonal H2 demand. The positive 0.61 correlation between monthly H2 production levels by PV electrolysis plants and monthly H2 demand reduces the required capacity of underground storage facilities. 

Certain plants have silvery or shiny leaves, which increases the amount of solar irradiation reflected. For instance, the fraction of S reflected by the leaf may increase from typical values of 0.1 or 0.2 (see Fig. 7-4) to 0.3 for silvery leaves, with an accompanying reduction in the absorptance from 0.6 to 0.5 or lower. This reduction in absorptance can have a major influence on T eaf. Other conditions remaining the same, a reduction of the absorptance a by only 0.1 can cause the leaf temperature to decrease from 24°C to 13°C (Table 7-1). Such a reduction in leaf temperature can have substantial effects on transpiration and photosynthesis, which can be particularly important for desert plants in hot environments. For instance, seasonal variations in... 

Coal Tar Products. Elevated red and white cell counts in urine were noted in 6-8% (29-34 of 452) of the employees examined in an industrial health survey in nine coal tar plants in which coal tar creosote and coal tar were the main treatments used (TOMA 1981). Some of these cell count elevations were attributed to urinary tract infections resulting from inadequate personal hygiene, and not to industrial exposure to toxic chemicals. However, some of the workers with elevated red and white cell counts in urine had cellular and granular casts and traces of protein, suggesting abnormal renal function. These individuals were referred to their physicians for diagnosis. No determination of exposure was made at the nine coal tar plants (TOMA 1981). Moreover, no clear relationship could be established because exposure routes in addition to inhalation (e.g., oral and dermal) were likely. Also, the ability to relate renal effects to coal tar creosote and coal tar exposure was further confounded by the possibility that the subjects were also exposed to other chemicals and cigarette smoke. Additional limitations of the study included seasonal and geographical variation in plant locations, past employment history, voluntary participation in the study that could have biased it in favor of healthy workers, lack of statistical analyses, lack of adequate controls, and use of only current employees. 

Studies of the isolation and the constitution of alkaloids of the Papaveraceae family have led to the investigation of the effect of various types of drying on the quantity of alkaloids in the leaves of Macleaya (Bocconia) microcarpa (52), the stability of some Papaver alkaloids (in different solvents) to sunlight (294), the accumulation of alkaloids in the latex of the Papaveraceae (243), the site of origin of the alkaloids in the studied plants (295, 296), the different geographical zones (297, 298), the time after flowering (299), and the seasonal variations in the content of the individual groups of alkaloids, particularly in P. somniferum (300). 

Although a considerable body of information on insect responses to plant N-fertilization has accumulated since 1930 (at least 200 studies), the results are generally not comparable because of variable experimental conditions (e.g. different plant cultivars, soils, insects, temperature). Furthermore, effects of seasonal variation in quantity and quality of plant N content and biochemically associated allelochemics upon post-ingestive growth performance indices of insects were generally unknown at that time, as were the effects upon herbivores of fertilizer-induced variation in plant chemistry (Jones, 1976 Scriber, 1984). 

The influence of seasonal harvest of plants and geographical location still has to be investigated in detail in order to be able to draw the utmost benefit for industrial use. Seasonal variations showed some effects on EOs of the cerrado species ... 

Pollen allelopathy can find utilization in field cultivations that could contain pollen of allelopathic crops or weeds. Pollen allelopathy could be an effective method for annual weed control that reproduce, at least in part, via wind pollination and flower concurrently with the allelopathic species. The effects of allelopathy should result in the loss of genetic variation and so in reduction of reproductive ability, but some plants are probably able to detoxify the pollen allelochemicals (Murphy and Aarssen 1995a, b). Murphy and Aarssen (1989) suggested possible delaying of weed flowering at later, less favorable times of the season or diurnal period, so decrease in weed pressure. However, infestation by perennial weeds can worsen due to compensation of pollen allelopathy through increase in the formation of rhizomes. 

Shorter-term temporal variation in leaf quality should act to complicate the spatial arrays described above. Thus, not only may a foraging insect have difficulty locating suitable feeding sites in space, but their locations may shift from time to time or continuously, as seasonal changes, induction effects, or even plant pathogen attack (44) alter tissue quality. A suitable tissue at one time may not be suitable later in the day, or later in the insect s life. 

The plant sources of lysergic acid amides contain not just one psychoactive molecule but several variations in effect are possible due to growing seasons and other environmental influences on the chemistry of the plant. Again, I should mention that in the American varieties of psychedelic lpomoea there is a uterotonic effect—hence these should not be used by... 

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