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801.
Zoran S. Petrović Yijin Xu Jelena Milić Gregory Glenn Artur Klamczynski 《Journal of Polymers and the Environment》2010,18(2):94-97
Thermoplastic urethanes based on polyricinoleic acid soft segments and MDI/BD hard segments with varied soft segment concentration
were prepared. Soft segment concentration was varied from, 40 to 70 wt%. Biodegradation was studied by respirometry. Segmented
polyurethanes with soft segments based on polyricinoleic acid degrade relatively slow losing about 11% carbon after 30 days,
but faster than corresponding petrochemical polyesterurethanes. Since biodegradation proceeds mainly through the soft segments,
higher soft segment content polymers displayed slightly higher biodegradation. Polyurethanes with dispersed hard domains in
the soft phase displayed slightly faster biodegradation than those with co-continuous morphology. Polyester diol degrades
slower than castor oil but significantly faster than the polyurethanes with built in soft segments from the same diol. Castor
oil biodegrades slower than soybean oil. 相似文献
802.
Christopher J. Anderson William J. Mitsch 《Journal of the American Water Resources Association》2008,44(6):1512-1520
Abstract: Tree basal growth in response to flooding regime was evaluated at a 5.2‐ha bottomland forest along the Olentangy River in central Ohio. Tree‐ring analysis was used to develop a 14‐year basal area increment (BAI) (cm2/year) series for 42 canopy trees (representing 10 species) throughout the bottomland. Mean annual BAI was evaluated relative to the frequency and duration of bankfull (>70 m3/s) and high‐flood (>154 m3/s) river discharge for a given water year (October 1‐September 30) and growing season (April 1‐September 30). A significant polynomial relationship was detected between the number of days of high‐flood river discharge over a combined two‐year period (Year i + Year i ? 1) and mean annual BAI. No significant relationships were detected when only the concurrent‐year or previous‐year flood regimes were considered or when growing season was considered. A similar relationship was detected when duration of high‐flood discharge days and BAI were both evaluated in two‐year increments (Year i + Year i ? 1). Mean annual BAI was most influenced by boxelder (Acer negundo) which was the dominant species and exhibited strong agreement with the overall BAI series. In each case, the resulting parabolic curve of tree basal growth in response to flooding suggests an optimal number of flooding days, a response to perturbation consistent with the subsidy‐stress model. Dendrochronology may be a useful tool for managers looking to restore environmental flows to regulated rivers. 相似文献
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Rachael M. Tomb Michelle Maclean John E. Coia Elizabeth Graham Michael McDonald Chintamani D. Atreya Scott J. MacGregor John G. Anderson 《Food and environmental virology》2017,9(2):159-167
The requirement for novel decontamination technologies for use in hospitals is ever present. One such system uses 405 nm visible light to inactivate microorganisms via ROS-generated oxidative damage. Although effective for bacterial and fungal inactivation, little is known about the virucidal effects of 405 nm light. Norovirus (NoV) gastroenteritis outbreaks often occur in the clinical setting, and this study was designed to investigate potential inactivation effects of 405 nm light on the NoV surrogate, feline calicivirus (FCV). FCV was exposed to 405 nm light whilst suspended in minimal and organically-rich media to establish the virucidal efficacy and the effect biologically-relevant material may play in viral susceptibility. Antiviral activity was successfully demonstrated with a 4 Log10 (99.99%) reduction in infectivity when suspended in minimal media evident after a dose of 2.8 kJ cm?2. FCV exposed in artificial faeces, artificial saliva, blood plasma and other organically rich media exhibited an equivalent level of inactivation using between 50–85% less dose of the light, indicating enhanced inactivation when the virus is present in organically-rich biologically-relevant media. Further research in this area could aid in the development of 405 nm light technology for effective NoV decontamination within the hospital environment. 相似文献
806.
The influence of genetic relatedness on the individual performance (e.g. growth, development) of animals is often tied to
agonistic or cooperative behaviors among conspecifics, and studies of the effects of kinship have produced mixed results.
To explore genetic relatedness independent of these behaviors, we investigated the effects of kinship on the growth of the
kelp perch Brachyistius frenatus, a live-bearing, planktivorous marine reef fish that is capable of only limited dispersal. Although juveniles occur in aggregations
and compete for food resources, they do not exhibit overt aggressive or cooperative behavioral interactions. We hypothesized
that under competition and in the absence of these behaviors, sibling and non-sibling groups of juvenile B. frenatus raised at the same densities in the field would not differ in average growth, but that siblings would exhibit lower variation
in growth, simply due to genetic similarities in inherent growth rates. Pregnant, female kelp perch were collected and placed
in cages until parturition was complete. Groups of young, recently born from the same mother or from different mothers, were
then raised in the field for 9 wk. Our results revealed that average growth rates were similar between sibling and non-sibling
treatments. While variation in growth increased initially in non-siblings, siblings showed little such variation. This divergence,
however, was not consistent over the duration of the experiment, and variation in the growth of siblings ultimately converged
with that of non-siblings. Effects of genetic relatedness would be most likely to manifest themselves early after birth, before
environmental factors exert their influence, and this may explain the initial separation but eventual convergence in variation
in growth between sibling and non-sibling treatments. For B. frenatus and other organisms that will encounter relatives and compete for resources without overt behavioral interactions, the degree
of kinship may play a minor role in the demography of local populations.
Received: 26 January 1998 / Accepted: 30 September 1998 相似文献
807.
As the theoretical bases for the dynamics of spatially subsidized communities emerge, ecologists question whether spatially subsidized communities exhibit similar structure or dynamics to communities that receive strongly pulsed resources. In both cases, communities may be structured by responses to resources that are potentially absent at any given point in time (pulsed communities) or space (subsidized communities), even if pulsed resources are part of the in situ productivity of the system or the subsidies arrive as a relatively constant input from a nearby system. The potential for significant spatial or temporal resource limitation, therefore, may be a key factor influencing in similar ways the persistence of populations, the structure and dynamics of communities, and the evolution of specific life history traits. In most complex systems, however, multiple resources may arrive for various trophic entities at various points in time and from various points in space, and thus it may be difficult to separate or compare the dynamics of spatially subsidized and pulsed systems. In this paper, we explore the effects of interactions between pulses and subsidies in plant and animal populations and communities on highly pulsed and variably subsidized islands in the Gulf of California. While many of the plant and animal communities on the unsubsidized islands in this system respond to pulses of rain in classic ways, responses to these rain pulses on islands subsidized by seabird guano or other marine resources are quite different and variable, and depend on a combination of life history characteristics, physiology, competitive interactions, and trophic relationships. These variable responses to rain pulses then translate into large differences in dynamics and community structure of subsidized vs. unsubsidized islands. Indeed, most systems experience both temporal pulses and spatial subsidies. When considered in tandem, complementary or synergistic effects of the multiple, temporally and spatially variable resources may emerge that help explain complex food web structure and dynamics. 相似文献
808.
William A. Searcy Rindy C. Anderson Stephen Nowicki 《Behavioral ecology and sociobiology》2008,62(7):1213-1216
We advocate assessing the reliability of signals of aggressive intent by eliciting aggressive signaling from a subject, giving
the subject an opportunity to attack a model, and testing whether the subject’s displays predict a subsequent attack. Using
this design, we found that most singing behaviors are poor predictors of attack in song sparrows (Melospiza melodia). Laidre and Vehrencamp (Behav Ecol Sociobiol, DOI 10.1007/s00265-007-0539-3, 2008) suggested altering our experimental design to make the model more realistic; it remains
to be seen whether such design changes would change the association between display and attack. Laidre and Vehrencamp (Behav Ecol Sociobiol, DOI 10.1007/s00265-007-0539-3, 2008) also suggested that the reliability of soft song, the one display that predicts attack
in song sparrows, can be explained by a vulnerability cost. We question the rationale for a vulnerability cost for this display
and suggest instead that soft song has a competing functions cost, in that, by using soft song to counter an intruder, a male
sacrifices other possible functions of vocal signaling. 相似文献
809.
Martin M. Karpiscak Glenn W. France K James DeCook Richard G. Brittain Kennith E. Foster Susan B. Hopf 《Journal of the American Water Resources Association》2001,37(5):1237-1248
ABSTRACT: Casa del Agua (Casa) in suburban Tucson, Arizona, was designed as a residential water conservation facility for applied research, demonstration of operational results, and transfer of technology to the general public. Starting in 1983, an existing residence was located, modified and retrofitted to acquire operational data on residential water use. Modifications included retrofitting existing landscapes and enlarging the rooftop to collect and harvest rainwater; separating blackwater and graywater lines; installing meters, low‐water‐use appliances and fixtures, and underground storage tanks for rainwater and graywater; and creating a public information center. Over the 13‐plus years of actual operation, both the interior and exterior water use research results indicate large reductions in water use can be effected using water‐saving devices andlor harvesting and reusing rainwater and graywater. Casa achieved over a 24 percent reduction in total water use and a 47 percent reduction in municipal water used compared to the typical Tucson residence. Overall water used was comprised of harvested rainwater (10 percent), recycled graywater (20 percent), and municipal water (70 percent). Casa's Information Center was visited by approximately 13,000 people from September 1985 through April 1999 and the research has been featured in local, national, and international media. 相似文献
810.