Comparison of analytical descriptions of nocturnal low-level jets within the Ekman model framework

This study focuses on the inertial oscillation aspect of the nocturnal low-level jet (NLLJ). In the context of the Ekman model solutions, conceptual NLLJ inertial oscillation analytical frameworks proposed by Blackadar in 1957 and Shapiro and Fedorovich and van de Wiel et al. in 2010 are compared. Considering a NLLJ produced via direct numerical simulation over flat terrain with no baroclinic influence as a reference case, the deficiencies of each framework in representing a realistic NLLJ are assessed. The Blackadar theory results in unrealistic wind profiles near the surface. While extensions of Blackadar’s framework by Shapiro and Fedorovich and van de Wiel et al. produce more realistic NLLJs, the simpler approach taken by van de Wiel et al. does not describe the NLLJ wind hodograph at later times sufficiently in qualitative terms.     

The evolution of the Canadian mining industry: The role of regulatory punctuation

In this study, we analyze the evolution of Canada's mining industry from 1929 to 2006, focussing on the determinants of the number of firms in the industry and why this number changed over that period. Most empirical studies of industry evolution have focused on manufacturing industries that share similar structural characteristics. Perhaps because of this, extant models of industry evolution tend to ignore industry-specific and national-specific factors that can cause atypical trajectories, that is, heterogeneous industry evolution. Initial inspection of the Canadian mining industry shows that it is atypical in that it exhibits “negative skew” over time in the number of firms rather than the typical “positive skew.” We review two dominant theoretical approaches to industry evolution: the density-dependence theory and variants of industrial organization economics. We also consider possible sources of industry evolution heterogeneity, focussing particularly on “regulatory punctuation”. Using Canadian mining data, we find that the traditional models do not fully explain the changes in population size in Canada's mining industry. As a result, we introduce a number of hybrid models. The results from these hybrid models suggest that Canadian-specific regulatory punctuations, particularly the introduction of significant new taxes, environmental legislation, and incentives have shaped the trajectory of mining firm participation.     

ANALYZING THE IMPACT OF LAND USE ON SEWER SERVICE AREA PLANNING1

ABSTRACT: The density and distribution of land uses has important consequences for the planning of sewerage systems and for the costs of these systems. This paper examines these consequences using a simplified service area model. The model determines the area to be served by a central waste treatment plant, where alternative on-lot disposal systems are also available. The model is applied to various urban area configurations, which are summarized by their total populations and by their population density distributions. Both minimum regional cost and minimum local cost service area configurations are determined. In addition, the sensitivity of the model to the parameters of the cost and population density functions is assessed. It is found that the model is most sensitive to the parameters of the collection cost function.     

Characterization of demethylation of methylmercury in cultured astrocytes

Mercury (Hg) is a well-known neurotoxicant but its toxicity depends on the species present. A steady emergence of inorganic Hg in the brain following chronic and accidental exposure to methylmercury (MeHg) has suggested that MeHg can undergo demethylation. The objective of this study is to develop an in vitro model to study factors affecting Hg demethylation in the central nervous system. Astrocytes obtained from neonatal rat pups were cultured for 24h with 1 microM MeHg in the presence of two pro-oxidants, buthionine sulphoximine (BSO) and rotenone. The BSO treatment produced a 21% increase in reactive oxygen species (ROS) content compared to the control (control vs. BSO; 100+/-1.35 vs. 121+/-1.52 relative fluorescence units (RFU)mg(-1) protein, p<0.001) but did not affect total Hg accumulation (control vs. BSO=86.5+/-4.14 ng mg(-1) vs. 95.7+/-9.26 ng mg(-1)). Rotenone increased ROS levels 107% (control vs. rotenone; 100%+/-1.35 vs. 207%+/-6.78RFU mg(-1)protein, p<0.001) and significantly increased the accumulation of total Hg (control vs. rotenone=86.5+/-4.14 ng mg(-1) vs. 124+/-3.80 ng mg(-1), p<0.001). There was no detectable demethylation in the control or BSO treated group, however, the rotenone treatment significantly increased the demethylation (control vs. rotenone=-1.86+/-5.57% vs. 16.3+/-2.68%, p<0.05). For the first time, we have demonstrated in an in vitro primary astrocyte culture model that MeHg can be converted to inorganic Hg and demethylation increases with oxidative stress. Our results provide a useful model to study demethylation of Hg in astrocytes and to explore potential ways to protect against Hg toxicity.     

Gonadal structure and population characteristics of the protogynous goby Coryphopterus glaucofraenum

Protogynous hermaphroditism has been reported in two gobiid species within the genus Coryphopterus, including C. nicholsi from the temperate northeastern Pacific and C. personatus from the Caribbean. In a third species from the Caribbean, C. glaucofraenum, experimental groups were established and gonad structure of experimental individuals (collected off the southwest coast of Puerto Rico between February 1985 and June 1987) was subsequently examined histologically to determine the sexual pattern. Protogyny was confirmed in C. glaucofraenum. Sex change was either initiated or completed, typically by the largest female, in all-female groups held for 10 to 40 d. Ovarian, transitional, and testis structure were similar to that of C. nicholsi and C. personatus. No preformed testicular tissue was evident in the ovary proper and ovarian features were not retained in the sex-changed testis beyond the newly transformed stage. Secretory accessory gonadal structures associated with the testis and which develop at the time of sex change arose from precursive tissue masses associated with the ventral portion of the ovarian wall in the region of the common genital sinus. The rapid development and onset of function in these structures, generally preceding that of the associated developing testis, suggest that they may play an important role in sex change events and in advertising new male status. Based on observed similarities of ovarian, transitional and secondary testis structure in three protogynous Coryphopterus species, including one species isolated since the last closing of the American landbridge, it is probable that protogyny is an ancestral condition in this genus.     

Nutrients and biomass distribution in the Gulf of Aqaba (Elat), Red Sea

The distribution of phosphate, nitrate and silicate values obtained from 300 samples and of biomass determined by displacement volume in about 1,900 vertical plankton hauls (65, 200 and 330 m) collected from 8 oceanographic station during 1974–1975 in the Gulf of Aqaba (Elat) are summarized and illustrated by crosssections. Generally, the Gulf is poor in nutrients and the data indicate that it is filled with upper (150 m) Red Sea waters, flowing in over the sill of Tiran. Nutrient content of the upper and deep waters immediately outside the sill are well within the known range of those in the northern Red Sea. Biomass values are relatively low in the Gulf are generally similar to those reported from the northern Red Sea. Both nutrients and biomass values display seasonal and bathymetric variations in the Gulf and outside the sill.     

环境中的药物——LC-MS/MS分析地表水和地下水

成百上千的活性物质正被用于人药和兽药处方中.由于药物的广泛应用,它们的残留物可通过多种途径进入环境.虽然主要通过尿和粪便的排泄,但是药品生产中的排放也应被考虑.当抗生素用于水产业,就会产生更直接的影响.污水处理设备不能完全除去药物,因此药物会出现在地表和地下水样品中.近年来,人们对环境中药物的兴趣正在增加,需要建立一种快速、灵敏、有选择性的方法来分析水样.     

Evidence for division of labor in the social caterpillar Eucheira socialis (Lepidoptera: Pieridae)

The caterpillars of Eucheira socialis westwoodi cooperatively spin and maintain a hollow silken nest and an elaborate network of silken foraging trails on their host plant, madrone (Arbutus spp.: Ericaceae). Nests typically contain several hundred larvae. Two populations are known to harbor a sex ratio distorter. The primary sex ratio in these two populations for four generations has been exceedingly male biased (64–79% male). Lepidoptera larvae are easily sexed using external morphology, allowing us to uniquely mark male and female larvae and to assemble larval groups of particular sex ratios. We report here the results of experiments on sex-specific larval behavior and physiology and the effect of colony sex ratio on individual behavior. We found that male larvae spent more time spinning silk on the nest and less time feeding than female larvae. Males were the first to emerge from the nest and the first to venture out along trails to feed. Male-biased nests had a significantly greater amount of silk deposited on their surfaces than female-biased nests. In the field, male-biased nests produced heavier male and female pupae than female-biased nests. Male and female larvae in 75% male nests became active earlier than males and females in other sex ratio treatments. Received: 11 September 1998 / Received in revised form: 24 February 1999 / Accepted: 27 March 1999     

The race is not to the swift: long-term data reveal pervasive declines in California's low-elevation butterfly fauna

Understanding the ecology of extinction is one of the primary challenges facing ecologists in the 21st century. Much of our current understanding of extinction, particularly for invertebrates, comes from studies with large geographic coverage but less temporal resolution, such as comparisons between historical collection records and contemporary surveys for geographic regions or political entities. We present a complementary approach involving a data set that is geographically restricted but temporally intensive: we focus on three sites in the Central Valley of California, and utilize 35 years of biweekly (every two weeks) surveys at our most long-sampled site. Previous analyses of these data revealed declines in richness over recent decades. Here, we take a more detailed approach to investigate the mode of decline for this fauna. We ask if all species are in decline, or only a subset. We also investigate traits commonly found to be predictors of extinction risk in other studies, such as body size, diet breadth, habitat association, and geographic range. We find that population declines are ubiquitous: the majority of species at our three focal sites (but not at a nearby site at higher elevation) are characterized by reductions in the fraction of days that they are observed per year. These declines are not readily predicted by ecological traits, with the possible exception of ruderal/non-ruderal status. Ruderal species, in slightly less precipitous decline than non-ruderal taxa, are more dispersive and more likely to be associated with disturbed habitats and exotic hosts. We conclude that population declines and extirpation, particularly in regions severely and recently impacted by anthropogenic alteration, might not be as predictable as has been suggested by other studies on the ecology of extinction.