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1.
This study examined a non-insecticidal tactic for suppressing boll weevil, Anthonomus grandis grandis Boheman, damage to cotton, Gossypium hirsutum L. In cage assays, kaolin, a reflective white mineral, applied to excised cotton squares or to the cotton foliage, initially resulted in lower levels of boll weevil injury to squares than nontreated squares. Boll weevil oviposition and feeding on kaolin-treated squares and squares on kaolin-treated cotton plants increased when nontreated squares and cotton plants were in short supply. A laboratory assay and field trials suggested that boll weevils distinguished between cotton plots based on color differences caused by kaolin and this appeared to influence levels of damage to squares. Random sampling in small plots indicated that oviposition damage to squares in plots treated with kaolin was reduced (P < 0.05) compared with nontreated controls, except when rain washed the kaolin off the foliage. Lint yield differences were not detected between the small plots, but the kaolin-treated small plots yielded as much as 2.36 times more cotton lint than a large but unreplicated adjacent nontreated control plot, and up to 1.39 times more than another large but unreplicated adjacent plot sprayed twice with preemptive applications of azinphosmethyl when cotton squares were first developing (pinhead stage). Potentially important avenues for future research on boll weevil injury suppression using kaolin are discussed.  相似文献   

2.
Stigmatic pollen loads of pin and thrum forms of distylous Lithospermum caroliniense (Walt.) MacMill. generally have very large proportions of incompatible pollen grains. Assortative pollination probably results from large components of self-pollination rather than geitonogamous pollinations, because pollen loads of large and small individuals are the same, although large individuals would be expected to experience more geitonogamous pollinator flights than small individuals. The distylous reproductive system appears relatively insensitive to changes in pollinator activity and preferential pollen flow between pins and thrums cannot be demonstrated. In contrast to the relatively uniform proportions of pin and thrum pollen on stigmas, absolute pollen loads vary substantially in different years and localities. Extremely low fecundity, which appears to be characteristic of this species, may result in part from lack of pollinator activity. However, even under optimal conditions for pollination, fecundity is less than 20%. Although L. caroliniense appears to have an inefficient pollination system, intrinsic low fecundity may represent a more critical feature of the life history.  相似文献   

3.
This paper examines the effect of thermal environment on movement patterns of free-ranging yellow baboons (Papio cynocephalus). For Amboseli baboons, one source of potential thermal stress is intense midday heat, and a plausible thermoregulatory response is for animals to simply move into the shade. I therefore examined the hypothesis that baboons would choose quadrats with higher shade availability (as measured by vegetation cover) in response to increasing midday heat loads (as measured by air temperature and solar radiation). Surprisingly, this was not the case—neither ambient air temperature, ambient solar radiation, nor quadrat plant species composition had a significant effect on shade availability of quadrat selected. Instead, thermal conditions affected a different aspect of baboon movements; namely, spatial displacement rates. At high air temperatures, baboons as a group traversed woodland habitats more slowly, and bare pans more quickly, than at lower air temperatures. I surmised that this relationship might reflect thermal effects on movement patterns at a smaller scale: if individuals exposed to high heat loads spent more time resting in shade under clumps of vegetation, they would thereby traverse densely-vegetated (hence shaded) quadrats more slowly. To address this question directly, I obtained focal sample data on activity and microhabitat budgets of individual baboons in relation to environmental temperature. The frequency of most combinations of activity state (e.g., grooming, social behavior) and microenvironment state (e.g., elevation, proximity to vegetation) did not vary monotonically with air temperature. However, baboons in shaded locations (but not those in unshaded locations) spent more time resting and less time moving at high air temperatures than low. In other words, baboon activity budgets depended on both microclimate and microhabitat—animals reduced their activity, particularly movement, when they encountered shade under hot conditions. This pattern of microhabitat choice in turn led to temperature-dependent changes in travel rate at the habitat level. These observational studies of movement patterns suggest that Amboseli baboons employ opportunistic thermoregulation—they do not seek out densely-shaded habitats or individual patches of shade at high air temperatures. Instead, they respond to environmental heat loads by resting, and thereby slowing down, when they happen to encounter plant shade. Aspects of baboon ecology that favor such an opportunistic mode of thermoregulation include large body size and non-thermal constraints on movement patterns.  相似文献   

4.
Scope  In this study, a dynamic model was built in which LCA and PBM were integrated to quantitatively assess the total environmental impacts induced by the product population in a society over time. Specifically, a determination was carried out concerning how Japan’s air conditioner population is used (lifetime distribution, number of units, etc.) and an assessment was made concerning the Global Warming Potential (GWP) associated with the air conditioner population. Methods  The proposed dynamic model was applied to air conditioners for analyzing the total GWP caused by the air conditioner population in Japan from 1990 to 2010. To create a trend forecast model for future environmental load, scenarios for air conditioner production up to 2010 were formulated and the total GWP from the air conditioner population was predicted. Conducted also were sensitivity analyses whose parameters were air conditioner performance, lifetime and the rate of refrigerant recovery when retired units are processed. Results and Discussion  Applying the PBM to the air conditioner population in 2000, it was found that 81.5 million units consumed 5.94 x 10p10 kWh in that year, which was a 6.1 % increase in the total annual power consumption in 1990. In both a stationary scenario and a steady growth (1.5% annual increase), it was found that the total GWP would be 27.7% higher than in 1990 under the stationary scenario and 37.8% higher under the steady growth scenario. The improvements in air conditioner performance will have a small effect on reducing the total GWP from that population. Furthermore, in connection with the average lifetime, it was found that the GWP, due to refrigerant releases when units are disposed of, would be relatively large in 2000 and the following years. Conclusions  Thus, shorter product lifetimes will spur a replacement of air conditioners with new units, a situation that will only lead to the reduction of GWP if the recovery rate of refrigerant is to be achieved to more than 50% under the stationary scenario. Recommendations and Outlook  To meet COP3 targets for Japan in 2010 (i.e. to reach the same level as in 1990 for household appliances), our study shows that it will be vital to raise the refrigerant recovery rate. If the number of air conditioners in use remains unchanged, recovery would have to be 45.7%, but under the steady growth scenario it would have to be at least 60.4%. Therefore, it will be difficult to meet COP3 targets unless the refrigerant recovery rate is strongly increased. This method is applicable to assess not only the GWP of air conditioners, but also other environmental impacts caused by a variety of product populations, which will be quite effective for setting targets of products’ performance, policymaking, etc.  相似文献   

5.
Human metapneumovirus (hMPV) is a newly described member of the Paramyxoviridae family causing acute respiratory tract infections, especially in young children. We studied the pathogenesis of this viral infection in two experimental small animal models (BALB/c mice and cotton rats). Significant viral replication in the lungs of both animals was found following an intranasal challenge of 10(8) 50% tissue culture infectious doses (TCID50) and persisted for <2 and <3 weeks in the case of cotton rats and mice, respectively. Peak viral loads were found on day 5 postinfection in both mice (mean of 1.92 x 10(7) TCID50/g lung) and cotton rats (mean of 1.03 x 10(5) TCID50/g). Clinical symptoms consisting of breathing difficulties, ruffled fur, and weight loss were noted in mice only around the time of peak viral replication. Most significant pulmonary inflammatory changes and peak expression of macrophage inflammatory protein 1alpha, gamma interferon, and RANTES occurred at the time of maximal viral replication (day 5) in both models. Cellular infiltration occurred predominantly around and within alveoli and persisted for at least 21 days in mice, whereas it was more limited in time with more peribronchiolitis in cotton rats. Both animal models would be of great value in evaluating different therapeutic agents, as well as vaccine candidates against hMPV.  相似文献   

6.
Argentavis magnificens , the largest known flying bird, had a wingspan of over 6 m with a mass of 80 kg. Its enormous size suggests that it was not a powerful flapper. The wing shape is inferred as more like that of large extant birds that soar relatively slowly on thermals over land than of large pelagic birds that soar over water. Its high wing loading would have allowed it to fly in moderate to strong winds that must have been prohibitive for the largest known contemporary thermal soarers. The high wing loading would have been ill-suited to flight under poor thermal conditions, but it would have been useful in slope-soaring on uprising air current against hillsides. We propose that Argentavis had a large home range that included a nesting area in the mountains of western and northwestern Argentina, and a feeding area in the Pampas.  相似文献   

7.
The impact of consuming biologically active compounds is often dose-dependent, where small quantities can be medicinal while larger doses are toxic. The consumption of plant secondary compounds can be toxic to herbivores in large doses, but can also improve survival in parasitized herbivores. In addition, recent studies have found that consuming nectar secondary compounds may decrease parasite loads in pollinators. However, the effect of compound dose on bee survival and parasite loads has not been assessed. To determine how secondary compound consumption affects survival and pathogen load in Bombus impatiens, we manipulated the presence of a common gut parasite, Crithidia bombi, and dietary concentration of anabasine, a nectar alkaloid produced by Nicotiana spp. using four concentrations naturally observed in floral nectar. We hypothesized that increased consumption of secondary compounds at concentrations found in nature would decrease survival of uninfected bees, but improve survival and ameliorate parasite loads in infected bees. We found medicinal effects of anabasine in infected bees; the high-anabasine diet decreased parasite loads and increased the probability of clearing the infection entirely. However, survival time was not affected by any level of anabasine concentration, or by interactive effects of anabasine concentration and infection. Crithidia infection reduced survival time by more than two days, but this effect was not significant. Our results support a medicinal role for anabasine at the highest concentration; moreover, we found no evidence for a survival-related cost of anabasine consumption across the concentration range found in nectar. Our results suggest that consuming anabasine at the higher levels of the natural range could reduce or clear pathogen loads without incurring costs for healthy bees.  相似文献   

8.
Water-soluble nutrients can be absorbed across the intestinal epithelium by transcellular and paracellular processes. Recent studies suggest that small birds (<180 g) have more extensive paracellular absorption of glucose than nonflying mammals. This may be a feature that compensates for a reduced small intestine size because small birds have smaller mass-corrected intestinal length than do nonflying mammals, but the difference diminishes in larger birds. We hypothesized that if this explanation were correct, there would be a negative correlation between paracellular absorption and body mass in birds and that larger birds would have paracellular absorption comparable to that of nonflying mammals. We tested this hypothesis, using consistent methodology, by measuring the extent of absorption of a series of inert carbohydrate probes in heavier bird species (>300 g) selected from diverse taxa: American coots, mallards, pheasants, and pigeons. Absorption of carbohydrate probes was inversely related to body mass in birds, and absorption of these probes in large birds (>500 g) was comparable to absorption measurements in nonflying mammals. Higher paracellular uptake in the smaller avian species may offer a physiologically inexpensive means of nutrient absorption to compensate for a reduced small intestine size but may make those species more vulnerable to toxicant absorption.  相似文献   

9.
Ribonuclease (RNase), which often represents molecular biological contamination, is a thermostable enzyme. When RNase is heated at 121°C by autoclave sterilization for 20 min, it does not lose its activity. However, the nature of the molecular events by which the irreversible denaturation occurs remains unknown. The purpose of this study was to elucidate the molecular mechanisms of irreversible thermal denaturation of RNase A and to develop an advanced sterilization method using soft‐hydrothermal processing, which has the advantages of improved safety and cost‐efficiency. The enzymatic activity of RNase was measured using polyacrylamide gel electrophoresis with torula yeast RNA. We evaluated the temperature and time course of irreversible thermoinactivation of RNase by normal autoclaving, hot‐air sterilization, and soft‐hydrothermal processing that had been controlled to the desired steam saturation ratio. The results indicated that RNase A was deactivated by autoclave sterilization (121°C, 20 min) immediately after treatment, but was reactivated over time. Hot‐air sterilization (180°C, atmospheric pressure, 60 min) produced results similar to that of autoclave sterilization. In contrast, RNase A was irreversibly thermoinactivated by soft‐hydrothermal processing (110°C, 20 min) at 100% steam saturation ratio. We also determined that the mechanism of irreversible thermoinactivation of RNase A involved hydrolysis and deamidation under this condition at a steam saturation ratio of more than 100%. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009  相似文献   

10.
1. In a helium atmosphere, heat is dissipated from a surface 3.5 times faster than it is in air. Eggs in a helium-oxygen atmosphere cool only 1.4 times faster than they cool in air. This signifies that internal resistance to heat flow is a significant factor in the cooling rates of eggs. 2. Heat flow occurs inside an egg in two ways: by conduction through the tissues and in flowing blood. Killing an embryo stops the latter, but not the former. Eggs cool more slowly after they have been killed, signifying that blood flow can be an important component in an egg's internal flows of heat. 3. Blood flow should be a relatively more important component of heat flow in large eggs than in small eggs. The difference in conductance between living and killed eggs is larger in 60 g chicken eggs than it is in 10 g quail eggs.  相似文献   

11.
The sticky trap and stationary aerial 'tow-net' catch insects which alight or fly on to them or are blown against them by the wind. It would be expected that such traps would be inefficient in light winds or in calm weather; and even though their efficiency should increase with stronger winds, errors of unknown magnitude may occur not only in estimations of density and of proportions of species in the air, but also with comparisons of actual catches. These errors are due to unknown degrees of weighting as the traps sample by means of a variable wind from a changing population density. The suction trap, on the other hand, samples a constant quantity of air in all relevant wind-speeds and does not appear to suffer so seriously from these disadvantages. It also works efficiently in perfectly calm weather when maximum densities of insects are often in the air.
The performances of the three traps in the field operating over a range of wind-speeds are described. Particular attention has been paid to aphids, for which the sticky trap and tow-net are generally used and for which the suction trap was primarily designed. Density estimates of these insects in winds below about 3 m.p.h. are much larger when calculated from suction trap catches as compared with estimates from sticky trap and tow-net catches. There is reason for the belief that the suction trap is neither attractive nor repellent to aphids to a significant extent, and that it catches these insects at random by virtue of its air stream alone; weighting of catches due to variable quantities of air being sampled does not occur. It is considered, therefore, that the suction-trap values of density are likely to be the more accurate ones. Sampling of other small insects is also discussed.  相似文献   

12.
The nectivorous ant Camponotus mus shows a broad size variation within the worker caste. Large ants can ingest faster and larger loads than small ones. Differences in physiological abilities in fluid ingestion due to the insect size could be related to differences in decision-making according to ant size during nectar foraging. Sucrose solutions of different levels of sugar concentration (30% or 60%w/w), viscosity (high or low) or flow rate (ad libitum or 1microl/min) were offered in combination to analyse the behavioural responses to each of these properties separately. Differences were found depending on ant body size and the property compared. A regulated flow produced smaller crop loads for medium and large ants compared to the same solution given ad libitum. All foragers remained longer times feeding at the regulated flow source but larger ants often made longer interruptions. When sugar concentration was constant but viscosity was high, only large ants increased feeding time. Constant viscosity with different sugar concentration determined longer feeding time and bigger loads for the most concentrated solution for small but not for large ants. Small ants reached similar crop loads in a variety of conditions while large ants did not. These differences could be evidence of a possible specialization for nectar foraging based on ant body size.  相似文献   

13.
I examined effects of pollination intensity on fruit, seed and seedling characteristics in Campsis radicans, and joint effects of pollen donor and pollination intensity on fruit production. Large pollen loads were more likely to initiate fruit production than small pollen loads, and the former fruits contained more seeds and a greater total seed mass. No further increases in seed number or mass occurred for pollen loads above 4,000 grains. The weight of individual seeds was unaffected by pollen load. Effects of pollen donor were generally larger than effects of pollen load, and fruit production from small loads of pollen from one donor were sometimes equal to fruit production from larger pollen loads from another donor. The ratio of pollen grains deposited to resultant seeds increased with pollen load, and several explanations are proposed. Seeds from heavy pollinations emerged better than seeds from light pollinations, but did not differ in speed of germination or in the performance of seedlings up to 126 days. The emergence differences are probably due to differing intensities of pollen tube competition.  相似文献   

14.
PHYSICAL ASPECTS OF STERILIZING COTTON ARTICLES BY STEAM   总被引:4,自引:4,他引:0  
SUMMARY: In this paper some of the physical processes occurring when cotton articles are sterilized in metal drums or bare packages in an autoclave are discussed, with special reference to the case where a good vacuum is drawn before the admission of steam. It is shown that under these conditions the heating will be quick, uniform, regular and reversible, and that no separate drying-off period should be needed. Calculation of the temperatures and moisture contents reached during the 'quasiequilibrium'period shows that the 'superheating'of the cotton is self-limiting, can never exceed a few degrees Centigrade, and will not give rise to serious weakening of the cotton. Calculation of the rate of irreversible penetration of moisture into the contents of the drum shows that this can easily be limited to the wrapping layer. Information is given on the 'heat-tendering'of cotton, and the advantages of using a good vacuum are summarized.  相似文献   

15.
Friction of volar skin on wood is not proportional to load in human beings and prosimians, but to load raised to a fractional power. This meets theoretical expectations for the frictional characteristics of convex elastic surfaces. Although this enables small clawless primates to cling to steeper slopes and larger vertical supports than would otherwise be possible, the magnitude of the effect is not great enough to overcome the disadvantages of clawlessness in climbing vertical or steeply-sloping tree trunks and branches. In human subjects, friction appears to be more nearly proportional to load than in small prosimians used as experimental subjects. It is suggested that this is due to the fact that the small animals have discrete, elevated volar pads. Pad coalescence in large primates may be an adaptation for increasing the power to which load must be raised to become proportional to friction; increasing this exponent yields more friction per unit of adduction force on supports that are small relative to the animals' dimensions and weights.  相似文献   

16.
Predictions of yield for the globe's major grain and legume arable crops suggest that, with a moderate temperature increase, production may increase in the temperate zone, but decline in the tropics. In total, global food supply may show little change. This security comes from inclusion of the direct effect of rising carbon dioxide (CO2) concentration, [CO2], which significantly stimulates yield by decreasing photorespiration in C3 crops and transpiration in all crops. Evidence for a large response to [CO2] is largely based on studies made within chambers at small scales, which would be considered unacceptable for standard agronomic trials of new cultivars or agrochemicals. Yet, predictions of the globe's future food security are based on such inadequate information. Free-Air Concentration Enrichment (FACE) technology now allows investigation of the effects of rising [CO2] and ozone on field crops under fully open-air conditions at an agronomic scale. Experiments with rice, wheat, maize and soybean show smaller increases in yield than anticipated from studies in chambers. Experiments with increased ozone show large yield losses (20%), which are not accounted for in projections of global food security. These findings suggest that current projections of global food security are overoptimistic. The fertilization effect of CO2 is less than that used in many models, while rising ozone will cause large yield losses in the Northern Hemisphere. Unfortunately, FACE studies have been limited in geographical extent and interactive effects of CO2, ozone and temperature have yet to be studied. Without more extensive study of the effects of these changes at an agronomic scale in the open air, our ever-more sophisticated models will continue to have feet of clay.  相似文献   

17.
Errors up to +/- 30 mm in determining the COP with piezoelectric force plates have been reported in the literature. To compensate for these errors, correction formulas were proposed, based on measurements with single point loads. In this paper, it will be shown that the errors in the COP depend on the load distribution. Two examples are presented: (1) simulated balance study, and (2) different pressure patterns during walking. Accurate corrections can only be made for forces distributed over a small area. Errors are expected to be overcompensated if there are only a few pressure peaks separated by large distances. These errors can be as large as the statistical errors (5.8 +/- 3.7 mm) after compensation. For certain situations, it is probably better not to use correction formulas.  相似文献   

18.
Cementless total hip femoral components rely on press-fit for initial stability and bone healing and remodeling for secondary fixation. However, the determinants of satisfactory press-fit are not well understood. In previous studies, human cortical bone loaded circumferentially to simulate press-fit exhibited viscoelastic, or time dependent, behavior. The effect of bone viscoelastic behavior on the initial stability of press-fit stems is not known. Therefore, in the current study, push-out loads of cylindrical stems press-fit into reamed cadaver diaphyseal femoral specimens were measured immediately after assembly and 24 h with stem-bone diametral interference and stem surface treatment as independent variables. It was hypothesized that stem-bone interference would result in a viscoelastic response of bone that would decrease push-out load thereby impairing initial press-fit stability. Results showed that push-out load significantly decreased over a 24 h period due to bone viscoelasticity. It was also found that high and low push-out loads occurred at relatively small amounts of stem-bone interference, but a relationship between stem-bone interference and push-out load could not be determined due to variability among specimens. On the basis of this model, it was concluded that press-fit fixation can occur at relatively low levels of diametral interference and that stem-bone interference elicits viscoelastic response that reduces stem stability over time. From a clinical perspective, these results suggest that there could be large variations in initial press-fit fixation among patients.  相似文献   

19.
20.
Appropriately controlled tests were carried out in two cases of patients with carcinoid tumors and abnormal circulating levels of serotonin to verify a hypothesis that such patients would have a greater tolerance for exogenous serotonin than would normal persons. Contrary to the hypothesis, the patients had not less but more reaction to intradermal injection of serotonin than to histamine and also more reaction than normal persons.If this altered reactivity were to be observed consistently in large series of patients with malignant carcinoid disease, it might be used as a presumptive test.  相似文献   

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