Influence of super-absorbent polymer on the growth rate of gas hydrate

The growth rate of hydrate and morphology of methane hydrate formation were studied in a visual pressure cell at 5.5 MPa. The gas hydrate formation was carried out (coal mine methane (CMM) + tetrahydrofuran (THF) + sodium dodecyl sulphate (SDS) + H₂O) with and without SAP. Experimental data on the hydrate growth rate and induction time were obtained for three different CMM samples. The influence of SAP on hydrate growth rate was determined. Results showed that after the addition of SAP, with the methane concentration increased in CMM, the induction time was reduced by 9 min, 10 min and 3 min, and the growth rate was shortened by 0.56 × 10⁻⁶/m³ min⁻¹, 0.53 × 10⁻⁶/m³ min⁻¹ and 1.42 × 10⁻⁶/m³ min⁻¹, respectively. This study could be useful for the recovery of methane from CMM by forming hydrate in the chemical and mining industry.     

Growth accounting in a fishery

Since 1950, the real value of fish catches in Norway has about doubled, while the number of fishermen has declined by about 85 percent. This has made it possible to maintain fishermen's incomes roughly on par with other occupational groups in Norway. It is investigated to what extent this increase in labor productivity is due to accumulation of capital, increasingly abundant fish stocks, or technological progress. Since the capital stock in recent years is not much greater in real terms than in the early 1960s, it is tempting to ascribe most of the increase in labor productivity to technical progress. This, however, would leave out the role of fish stocks; if stocks have increased over this period, this would explain some of what otherwise appears as a technical progress. Using data on labor, capital, fish catches, and fish stock abundance 1961–2004 the development of total factor productivity is examined. Ignoring changes in fish stocks, total factor productivity is estimated to have increased by 0.8 percent per year. Accounting for changes in fish stocks raises this to 1.7–4.3 percent per year, depending on the importance assigned to stocks as factors of production.     

The role of images of conspecifics as visual cues in the development and behavior of larval anurans

Tadpoles can alter their behavior, morphology, and life history in response to habitat change. Although chemical signals from conspecifics or predators play an important role in tadpole habitat assessment, little is known about the role of visual cues and the extent to which tadpoles rely on their vision for intraspecific social assessment. The aim of our experiments was to determine whether larval anurans use visual images of other tadpoles as indicators of density and to analyze how, and to what extent, images of conspecifics alone affect tadpole development, growth, and behavior. To assess this, we raised both Rana sylvatica and Bufo americanus tadpoles in aquaria with either quarter- or half-mirrored walls. Both physically increased density and increased density simulated with mirrors decreased tadpole growth and developmental rates, and increased activity in Rana tadpoles. Bufo tadpoles did not significantly alter their growth and development in response to visually increased density. Only true, i.e., physically, increased density had an effect on growth and activity in Bufo tadpoles. Our data show that images of conspecifics are used as visual cues by Rana tadpoles and can induce phenotypically plastic changes in several traits. This response to visual cues is taxon-specific. An erratum to this article can be found at     

Growth rates in a wild primate population: ecological influences and maternal effects

Growth rate is a life-history trait often linked to various fitness components, including survival, age of first reproduction, and fecundity. Here we present an analysis of growth-rate variability in a wild population of savannah baboons (Papio cynocephalus). We found that relative juvenile size was a stable individual trait during the juvenile period: individuals generally remained consistently large-for-age or small-for-age throughout development. Resource availability, which varied greatly in the study population (between completely wild-foraging and partially food-enhanced social groups), had major effects on growth. Sexual maturity was accelerated for animals in the food-enhanced foraging condition, and the extent and ontogeny of sexual dimorphism differed with resource availability. Maternal characteristics also had significant effects on growth. Under both foraging conditions, females of high dominance rank and multiparous females had relatively large-for-age juveniles. Large relative juvenile size predicted earlier age of sexual maturation for both males and females in the wild-feeding condition. This confirmed that maternal effects were pervasive and contributed to differences among individuals in fitness components.Communicated by J. Setchell     

Effects of golden shiner (Notemigonuscrysoleucas ) nest association on host pumpkinseeds (Lepomisgibbosus ): evidence for a non-parasitic relationship

The reproductive success of male parental pumpkinseeds, Lepomisgibbosus, was studied in relation to the use of their nests by spawning golden shiners, Notemigonuscrysoleucas. The brood size of pumpkinseeds with and without golden shiner's young was compared in a field population. Mean egg and larval numbers of pumpkinseeds did not differ between broods with and without shiners, suggesting that shiners had no net effect on the fitness of host pumpkinseeds. In the laboratory, however, hatching success of pumpkinseed embryos was significantly lower with shiners than without. This difference was attributable to fungal infection. Against this fitness loss, the presence of shiner larvae reduced predation on pumpkinseed larvae in laboratory experiments. Thus, two counteracting mechanisms are proposed to account for no observed net effect on the host: (1) increased fungal infection on pumpkinseed embryos and (2) decreased predation on pumpkinseed young. Received: 10 January 1997 / Accepted after revision: 9 August 1997     

Does begging affect growth in nestling tree swallows,<Emphasis Type="Italic"> Tachycineta bicolor</Emphasis>?

Much of the theoretical work on the evolution of begging assumes this elaborate display is costly. The evidence for an energetic cost to begging has, however, been equivocal. Metabolic studies on nestling birds suggest that begging requires minimal energy, but some growth studies have shown that excess begging reduces growth rates. One difficulty in interpreting these results is that metabolic and growth studies have each been performed on different species. Here, we test whether high begging frequencies depress growth in nestling tree swallows, Tachycineta bicolor, a species in which the metabolic cost of begging has been measured. When we compared the growth of nestlings stimulated to beg at either high or low frequencies, we found no significant differences in their mass gained, wing growth or portion of ingested energy devoted to begging either during the experimental period or in the 24 h following the end of the experiment. We also found no significant relationship between begging intensity and growth measurements. The results of our study are consistent with previous metabolic studies on this species suggesting that the energetic cost of begging is relatively low. More generally, evidence for a fitness cost of begging via decreased growth is equivocal.Communicated by J. Dickinson     

Fitness benefits of multiple mating versus female mate choice in the cellar spider (Pholcus phalangioides)

Recent studies have demonstrated that mating with multiple males can be beneficial for females and her offspring even if males contribute nothing but sperm. This was mainly established for species in which sperm from several males mix in the reproductive tract of the female, thus allowing sperm competition and/or female sperm choice. However, in species with last male sperm precedence, female re-mating decides against the previous male by strongly limiting his reproductive success. We tested the effect of female re-mating behaviour using the cellar spider Pholcus phalangioides, which shows strong last males sperm precedence and moderate levels of polyandry under natural situations. We predicted that females prevented from remating even though they are receptive would show reduced reproductive success compared to females that accept two copulations and females that reject a second male, since the latter two treatments were allowed to behave according to their decisions. However, if the number of matings per se had an effect on oviposition or on offspring performance, double-mated females should perform better compared to both treatments of once-mated females. We measured female fecundity and fertility over a period of 140 days, comparable to the species' natural reproductive peak season. Two thousand one hundred and fifty-two offspring from 67 first egg sacs were reared under two feeding levels. We registered development time and survival, and measured offspring adult size and mass. We found a positive effect of double mating, as in this treatment, oviposition probability was higher compared to the other treatments. Interestingly, adult female offspring of the DM treatment that were raised under low food level had a higher condition index compared to those from FS and RM, but development time, size and mass at adulthood were not affected by mating treatment. Female choice only seemed to affect hatching latency of the offspring. Overall, the main predictor of female reproductive output and success was female body size.     

测定氨氮的经验点滴

用纳氏比色法测定NH3-N时,在保证斜率不变(b=0.0037)的条件下,减少显色剂中HgCI2-KI三分之二的含量,聚乙烯醇做胶体稳定剂,显著提高了显色剂和显色的稳定度,并大大降低了空白吸光度.以KOH和酒石酸钾纳做缓冲溶液,并增加KOH一倍的含量,保持恒定的显色碱度,同时也掩蔽了金属离子的干扰.测定废水,先做一条件试验,确定氨氮废水的稀释比,是测定氨氮的重要步骤.     

Contaminated sediments and bioassay responses of three macroinvertebrates, the midge larva Chironomus riparius, the water louse Asellus aquaticus and the mayfly nymph Ephoron virgo

Bioassays are widely used to estimate ecological risks of contaminated sediments. We compared the results of three whole sediment bioassays, using the midge larva Chironomus riparius, the water louse Asellus aquaticus, and the mayfly nymph Ephoron virgo. We used sediments from sixteen locations in the Dutch Rhine-Meuse Delta that differed in level of contamination. Previously developed protocols for each bioassay were followed, which differed in sediment pretreatment, replication, and food availability. The Chironomus bioassay was conducted in situ, whereas the other two were conducted in the laboratory. The measured endpoints, survival and growth, were related to contaminant levels in the sediment and to food quantity in water and sediment.

Only the response of A. aquaticus in the bioassay was correlated with sediment contamination. Food availability in overlying water was much more important for C. riparius and E. virgo, thereby masking potential sediment contaminant effects. We conclude that growth of A. aquaticus was depressed by sediment contamination, whereas growth of E. virgo and C. riparius was stimulated by seston food quantity. We discuss that the trophic state of the ecosystem largely affects the ecological risks of contaminated sediments.     

引入稀释因素后的废水处理效果估算方法讨论

讨论了经稀释后废水处理时几种常州的污染物去除率及削减量的估算方法，通过实例分析了各估算方法的区别与联系，并提出了在选用估算方法时的注意事项。