NATURAL RESTABILIZATION OF STREAM CHANNELS IN URBAN WATERSHEDS1

ABSTRACT: Stream channels are known to change their form as a result of watershed urbanization, but do they restabilize under subsequent conditions of constant urban land use? Streams in seven developed and developing watersheds (drainage areas 5–35 km²) in the Puget Sound lowlands were evaluated for their channel stability and degree of urbanization, using field and historical data. Protocols for determining channel stability by visual assessment, calculated bed mobility at bankfull flows, and resurveyed cross‐sections were compared and yielded nearly identical results. We found that channel restabilization generally does occur within one or two decades of constant watershed land use, but it is not universal. When (or if) an individual stream will restabilize depends on specific hydrologic and geomorphic characteristics of the channel and its watershed; observed stability is not well predicted by simply the magnitude of urban development or the rate of ongoing land‐use change. The tendency for channel restabilization suggests that management efforts focused primarily on maintaining stability, particularly in a still‐urbanizing watershed, may not always be necessary. Yet physical stability alone is not a sufficient condition for a biologically healthy stream, and additional rehabilitation measures will almost certainly be required to restore biological conditions in urban systems.     

北京市大气PM2.5中矿物成分的污染特征

为了解北京市大气细粒子中矿物成分的浓度水平和污染特征,在清华园和车公庄进行了连续1a的PM_2.5累积周采样和全样品分析.Al、Si、Ca、Mg和Fe等地壳元素的周变化相似,最大周均浓度均出现在春季有强沙尘天气的一周;其季节变化显著,显示季节性的源排放以及气象条件对矿物成分的含量影响显著.土壤尘的季节平均浓度从夏季逐步上升,至次年春季达到最高(21.1 μg·m^-3),表明春季频繁发生的沙尘天气对土壤尘细粒子有重要贡献.大量的建筑活动可能大大增加了北京细粒子中Ca的负荷,应加强其排放控制.     

Familial congenital diaphragmatic hernia: Prenatal diagnosis,management, and outcome

Congenital diaphragmatic hernia (CDH) is a developmental defect of as yet unknown aetiology which accounts for 8 per cent of all major congenital anomalies and is associated with up to 80 per cent mortality despite optimal postnatal treatment. The risk of recurrence of CDH for future sibs after one affected infant is about 2 per cent. A multifactorial/threshold inheritance pattern with an observed high male:female sex ratio is currently favoured for the rare occurrence of familial CDH, although other modes of inheritance have also been described. We report three cases of familial CDH, two of whom were brother and sister sibs and the third was a first cousin, born within 18 months of each other. The diagnosis was by ultrasound and there were several factors predicting a poor outcome. The mortality in this group was 100 per cent. The prenatal diagnosis, treatment options, the unusual genetic aspects, outcome, and the pathology involved are discussed.     

Defense mechanisms and antipredator behavior in two sympatric species of spiny lobsters, Panulirus argus and P. guttatus

The congeneric spiny lobsters Panulirus argus and P. guttatus co-occur throughout the Caribbean Sea, where they may share the coral reef habitat. Despite their phylogenetic closeness, both species have many different life-history traits that may partially explain their coexistence. However, even though both species may face the same predators, their defense mechanisms and antipredator strategies had not been compared. We compared the performance between species in 18 morphological and behavioral defense mechanisms commonly expressed by most spiny lobsters, including predator-avoidance mechanisms (activity schedule, sheltering behavior, delay to disturbance, and effect of conspecific damage-released scents on shelter choice) as well as antipredator mechanisms (body size, several parameters of the escape response and limb autospasy, clinging strength, antennal strength, and cooperative defense). As hypothesized, both species expressed all these defense mechanisms (except cooperative defense, shown only by P. argus), reflecting their phylogenetic closeness, but performed significantly differently in most, in accordance with their particular ontogenetic traits. Their comparative performance in individual defense mechanisms as well as the antipredator strategies displayed by groups of lobsters of each species in the presence of a common predator (the triggerfish Balistes vetula) showed that, in general, the defensive behavioral type of P. argus is more bold and that of P. guttatus more shy. Therefore, their distinct defensive behaviors contribute to their niche differentiation.     

Involvement of bioemulsifier in heptadecane uptake in Pseudomonas nautica

A microbial surfactant was investigated for its potential to enhance the biodegradation of heptadecane. The bioemulsifier used in this study was extracted from culture supernatants of Pseudomonas nautica after growth on heptadecane. The heptadecane uptake rate-could be increased 15-fold by the addition of 1.5 mg protein of bioemulsifier per 100 mg of heptadecane. Scanning electron microscopy showed that bioemulsification was the main mode allowing the transfer of hydrocarbon in the presence of the isolated compound.     

Comparison of photochemical behavior of various humic substances in water: II. Photosensitized oxygenations

The photochemical oxygenation of 2,5-dimethylfuran (DMF) in water was studied under a variety of reaction conditions employing various humic substances as photosensitizers. As predicted by theory, the reactions at low DMF concentrations were first order with respect to DMF, and the reaction rate constants were directly proportional to the average light intensity and to the concentration of humic substance. The rate of oxygenation photosensitized by the humic matter from a river was independent of hydrogen ion activity in the pH 5 to 9 range. Wavelength studies indicate that oxygenations photosensitized by humic substances are induced by ultraviolet and blue radiation. Rate constants computed for this photosensitized reaction in sunlight were in close agreement with experimental values. Calculations also show that the ratio of the sunlight rate constants to total visible solar irradiance (400 to 700 nm) is approximately constant. Therefore, it may be possible to calibrate rate constants for photosensitized reactions in terms of commonly measured units of visible light intensity such as foot candles.     

Uptake and release of phosphorus by phytoplankton in the Chesapeake Bay estuary,USA

The phytoplankton uptake and release rates for inorganic phosphate, dissolved organic phosphate and polyphosphate were estimated during 5 cruises on the Chesapeake Bay over a 9-month period. Phosphorus in all pools turned over in several minutes to 100 h, and each soluble pool appeared to contain fractions which were metabolically useful to the phytoplankton. Maximal uptake rates (V _m ) for orthophosphate ranged from 0.02 to 2.95 μg-at P (1.h)^-1 with half saturation constants (K _s ) between 0.09 and 1.72 μg-at P l^-1. At low soluble reactive phosphorus concentrations, the uptake rate of trace ³²P orthophosphate was initially rapid, but declined after 15 to 60 min incubation. The data suggest that the initial uptake phase was dominated by exchange of ³²PO₄ ^≡ for ³¹PO₄ ^≡ in the membrane transport systems whereas the subsequent phase represented the net incorporation of orthophosphate into phytoplankton cells.     

Male residence and the patterning of serum testosterone in vervet monkeys (<Emphasis Type="Italic">Cercopithecus aethiops</Emphasis>)

This study investigated hormonal and demographic processes underlying unimale and multimale mating systems in primates. Reproductive skew and challenge models of male competition provide conflicting predictions of the relationship of male residence to group composition and androgen regulation. These predictions were tested using endocrine and socioecological data from Kenyan vervet monkeys (Cercopithecus aethiops). Serum samples from 57 adult male monkeys, drawn from 19 separate groups and 4 populations, were assayed for testosterone by radioimmunoassay. Male ability to respond to conspecific challenge was assessed by their testosterone response to the capture protocol.Analyses showed that reproductive skew models were useful predictors of intergroup and interpopulation variation in male residence and T profiles. The Limited Control model of male residence was supported by positive correlations of the number of males per group with the number of females without dependent offspring, demonstrating that monopolization potential was a key determinant of male residence. Testosterone concentrations under conditions that elevated serum levels were positively correlated with infanticide risk, supporting the Concession model. Population comparisons provided evidence for increased T responsiveness where groups were predominantly unimale. Unimale populations were from sites with higher rainfall, suggesting that ecological factors contributed to population differences in male residence and T regulation.For species name, we follow the 2000 taxonomy of the IUCN/SSC Primate Specialist Groups workshop (Grubb et al. 2003)     

Cultivated cells from mid-trimester amniotic fluids. IV. Cell type identification via one and two-dimensional electrophoresis of clonal whole cell homogenates

Clones of cultivated amniotic fluid cells that have distinct morphologic and growth characteristics (F, AF and E-type) were examined by one-dimensional SDS polyacrylamide gel electrophoresis (SDS-PAGE) and by two-dimensional electrophoresis employing isoelectric focusing and SDS-PAGE (IEF-PAGE). No qualitative differences in band pattern were observed in SDS-PAGE between the various amniotic fluid cell types, but consistent quantitative differences in the ratios of four bands of presumed filamentous proteins provided good distinction between amniotic fluid cells and postnatal skin fibroblast-like cells. By adding separation on the basis of electrical charge to that of molecular size (IEF-PAGE), we observed reproducible qualitative differences in the protein spot patterns between F and both AF and E-type amniotic fluid cells. At least eight discrete proteins appear not to be synthesized by prenatal F-type cells in comparison with their isogenic AF and E counterparts under identical culture conditions. The two-dimensional electrophoretic patterns thus confirm that F and AF amniotic cells, in spite of their morphologic and growth kinetic similarities, are developmentally distinct cell types that retain their differentiated states in culture.