Effects of Alkali Treatment on the Properties of Short Flax Fiber–Poly(Lactic Acid) Eco-Composites

In this study, the influence of alkali (NaOH) treatment on the mechanical, thermal and morphological properties of eco-composites of short flax fiber/poly(lactic acid) (PLA) was investigated. SEM analysis conducted on alkali treated flax fibers showed that the packed structure of the fibrils was deformed by the removal non-cellulosic materials. The fibrils were separated from each other and the surface roughness of the alkali treated flax fibers was improved. The mechanical tests indicated that the modulus of the untreated fiber/PLA composites was higher than that of PLA; on the other hand the modulus of alkali treated flax fiber/PLA was lower than PLA. Thermal properties of the PLA in the treated flax fiber composites were also affected. T_g values of treated flax fiber composites were lowered by nearly 10 °C for 10% NaOH treatment and 15 °C for 30% NaOH treatment. A bimodal melting behavior was observed for treated fiber composites different than both of neat PLA and untreated fiber composites. Furthermore, wide angle X-ray diffraction analysis showed that the crystalline structure of cellulose of flax fibers changed from cellulose-I structure to cellulose-II.     

Manganese in the urban atmosphere: identifying anomalous concentrations and sources

Purpose  

Industrial emissions can raise urban background levels of inhalable Mn particles in an order of magnitude above normal, eclipsing the contribution made by natural sources and traffic.     

Consistent personality differences in house-hunting behavior but not decision speed in swarms of honey bees (<Emphasis Type="BoldItalic">Apis mellifera</Emphasis>)

Speed-accuracy tradeoffs are a common feature of decision-making processes, both in individual animals and in groups of animals working together to reach a single collective decision. Individual organisms display consistent differences in their “impulsivity,” and vary in their tendency to make rapid, impulsive choices as opposed to slower, more accurate decisions. However, we do not yet know whether groups of animals consistently differ in their tendency to prioritize decision speed over accuracy. We challenged 17 swarms of honey bees (Apis mellifera) to simultaneously choose a new nest site in each of three locations, and measured their decision speeds in each trial. We found that swarms displayed consistent personality differences in the number of waggle dances and shaking signals they performed and in how actively they scouted for new nest sites. However, swarms did not consistently differ in how long they took to choose a nest site. We suggest that house-hunting A. mellifera swarms may place an especially high emphasis on decision accuracy when choosing a nest site, and that chance events—such as the time when each swarm discovers a sufficiently high-quality nest site—may consequently play a greater role in determining a swarm’s decision speed than intrinsic characteristics such as a swarm’s “impulsivity.”     

Efficacy of vermicomposting for recycling organic portion of hospital wastes using <Emphasis Type="Italic">Eisenia fetida</Emphasis>: standardization of cow manure proportion to increase enzymatic activities and fungal biomass

Hospital wastes are infectious wastes generated in hospitals and need to be disposed in such a way that they do not spread disease. In this experiment, 5, 10, 15 and 20% cow manure (CM) were mixed with hospital wastes (HW), and mixed wastes were subjected to vermicomposting. In control treatment, only HW was used for vermicomposting. Results suggested that significantly (P ≤ 0.05) higher total nitrogen content was recorded in vermicomposts when 10% or more CM was added to HW. Higher mineralization rate (decrease in C/N ratio) and cellulase activity is probably responsible for rapid organic matter decomposition (loss of total organic carbon). Ergosterol content i.e., total fungal biomass and cellulolytic fungal population were almost constant initially, but increased in the latter stage of vermicomposting. All the vermicompost samples, prepared in this experiment, showed the absence of coliform bacteria. Therefore, it could be concluded that 10% CM addition with HW was the most economical to obtain best quality vermicompost in terms of nutrient content and microbial status.     

Challenges to achieving a successful transition to a low carbon economy in South Africa: examples from poor urban communities

South Africa faces several development challenges including those linked to climate change. Energy usage in South Africa, for example, is already constrained because of a range of development challenges (the dependence on cheap coal as a heating source; energy availability; access; affordability of alternative energy sources; and a range of health impacts, including air pollution). Notwithstanding calls for a transition to a low carbon economy, there have been few, recent assessments in South Africa of the costs associated with such a transition, particularly the social and economic costs for the poor who use energy in a variety of ways. In this paper we focus on trying to unravel some of the complex energy-use behaviour including understanding what drives consumers in resource-poor areas to choose and use persistently risky energy options. Analysis of qualitative data in two township areas, Doornkop and Kwaguqa, shows that township households, whether electrified or not, continue to burn coal. In both study areas, an estimated 80% of electrified households burn coal for space heating and cooking and also make use of multiple fuel sources for a range of activities. Although the major obstacles preventing people from discontinuing domestic coal combustion are poverty, the ready availability and social acceptability of coal together with other social customs cannot be underrated. This paper therefore highlights some of the persistent challenges associated with sustainable energy transitions in South Africa including implications for improved mitigation and adaptation for the energy sector in wider climate change efforts.     

Trade-off between pre- and postcopulatory sexual cannibalism in a wolf spider (Araneae,Lycosidae)

Sexual cannibalism can occur before, during or after mating. Relatively few experimental studies have examined why there is variation in the timing of sexual cannibalism. We examined the latency and number of attacks required for female spiders to capture male spiders pre- vs. postcopulation. We also examined the effects of female mating status and hunger level on the occurrence of pre- and postcopulatory cannibalism, which reflects the contribution of both relative capture success and female motivation to cannibalize males. Precopulatory cannibalism occurred after a shorter interval and required fewer chases and physical interactions for the female to successfully capture the male than was the case for postcopulatory cannibalism. Virgin females were more likely to engage in postcopulatory rather than precopulatory cannibalism and mated females vice versa. Those virgin females that did engage in precopulatory cannibalism had significantly lower body condition than virgin females engaging in postcopulatory cannibalism. While precopulatory cannibalism occurred more quickly and required fewer attacks by females, it comes at a potential cost of not mating with males. Hence, females are more likely to engage in precopulatory cannibalism if they have already mated or, if virgins, if they have low body condition. These results indicate that the decision of when to cannibalize males is dynamic and depends upon the relative value of a male as a mate versus a meal.     

Age before beauty? Relationships between fertilization success and age-dependent ornaments in barn swallows

When males become more ornamented and reproduce more successfully as they grow older, phenotypic correlations between ornament exaggeration and reproductive success can be confounded with age effects in cross-sectional studies, and thus say relatively little about sexual selection on these traits. This is exemplified here in a correlative study of male fertilization success in a large colony of American barn swallows (Hirundo rustica erythrogaster). Previous studies of this species have indicated that two sexually dimorphic traits, tail length and ventral plumage coloration, are positively correlated with male fertilization success, and a mechanism of sexual selection by female choice has been invoked. However, these studies did not control for potential age-related variation in trait expression. Here, we show that male fertilization success was positively correlated with male tail length but not with plumage coloration. We also show that 1-year-old males had shorter tails and lower fertilization success than older males. This age effect accounted for much of the covariance between tail length and fertilization success. Still, there was a positive relationship between tail length and fertilization success among older males. But as this group consisted of males from different age classes, an age effect may be hidden in this relationship as well. Our data also revealed a longitudinal increase in both tail length and fertilization success for individual males. We argue that age-dependent ornament expression and reproductive performance in males complicate inferences about female preferences and sexual selection.