Phosphorus Inputs to Lake Simcoe from 1990 to 2003: Declines in Tributary Loads and Observations on Lake Water Quality

Total phosphorus (TP) inputs to Lake Simcoe have led to hypolimnetic dissolved oxygen (DO) depletion and loss of cold water fish habitat. Since 1990, efforts have been made to reduce the total TP input to the lake below a defined target of 75 t/year, which was predicted to lead to reductions in spring TP concentration and improvements in end-of-summer hypolimnetic DO concentrations. The total TP load to the lake during the most recent period of record (1998/99-2003/04) ranged from 53 to 76 t/yr and averaged 67 t/yr, compared to an average of 114 t/yr estimated between 1990/91 and 1997/98 (range 85-157 t/yr). Reductions in TP loads from the catchment via tributary discharge (∼26 t) accounted for the majority of the decrease in total load between the two time periods. Total P concentrations decreased significantly in four out of six long-term monitored tributaries; however, concentrations in all six tributaries remain above the level recommended to avoid nuisance plant growth (30 μg/L). Although TP loads to the lake are currently below the target 75 t/yr, excessive growths of filamentous algae and macrophytes continue to be a problem in the nearshore zone. End-of-summer minimum hypolimnetic DO concentrations (average 4.3 mg/L, 1998/99-2003/04) remain substantially below the level (7 mg/L) that is considered protective of lake trout. Efforts to reduce TP loads to the lake therefore need to continue.     

Distribution, relative abundance, and prey demand by double-crested cormorants on Manitoulin Island lakes vs. Lake Huron Coast

An aerial distance sampling survey of double-crested cormorants (Phalacrocorax auritus) was conducted in the northern region of Lake Huron (North Channel; four largest lakes of Manitoulin Island; South Shore of Manitoulin Is. facing the main body of the lake) to assess the relative distribution, abundance and prey demand by cormorants on inland lake vs. coastal habitat. On a per area basis, the density (approx. 1-2 cormorants ? km^− 2) and prey demand (approx. 1.2 kg ha^− 1) of cormorants in the four inland lakes matched that of the North Channel. The South Shore had approximately half the density and prey demand as the other two areas. Cormorants on the inland lakes of Manitoulin Island represented 13% early in the season and a high of 33% of the total population for this region of Lake Huron later in the summer. Estimating regional distributions of cormorants within the Great Lakes basin is important because mapped nest colonies and nest counts are not representative of the actual distribution of foraging cormorants during and after the nesting season. There are two general conclusions to emerge from this survey. First, aquatic productivity from both Great Lakes coast and inland lakes contributes to trends in population and distribution of cormorants in the northern region of Lake Huron and perhaps elsewhere. Second, inland aquatic ecosystems are important throughout a season for foraging cormorants from the Great Lakes and may become more important as Great Lake productivity trends downward.     

Spawning Migration of Great Lakes Pink Salmon (Oncorhynchus Gorbuscha): Size and Sex Distributions,River Entrance and Exit

Pink salmon (Oncorhynchus gorbuscha) migrated in an easterly direction into the Carp and Pancake rivers, Lake Superior, from 26 August to 30 September 1981. Population estimates were 7,500 and 7,285 at the Carp and Pancake rivers, respectively. Peaks in numbers of fish entering the rivers followed onshore wind events. River entrance peaked between 2000 and 2400. Fish moved within the rivers at approximately 1 km/d. The proportions of females, 35 and 45% at the Carp and Pancake rivers, respectively, were low compared to those of Pacific stocks, and varied temporally, being lowest early in the migrations. Mean size of male migrants varied over time, with smaller males coming first, followed by larger males. Toward the end of the migrations, mean length of males decreased. Mean length of females did not vary temporally. At each river, several hundred fish that had not spawned were recaptured attempting to return to the lake. Many were recaught several times, each time being replaced upstream. Thirty-two such fish were subsequently recaught in nearshore nets. This exiting of rivers was greater than previously reported for Pacific stocks. We hypothesize that in Great Lakes pink salmon, exiting rivers is a characteristic of straying behaviour, and that straying has been selected for in this stock.     

Seasonal Movements and Habitats of Brown Trout (Salmo Trutta) in Southcentral Lake Ontario

During 1980–82 the movements, seasonal locations, and habitat preferences of brown trout in southcentral Lake Ontario were examined using radio telemetry and vertical gill nets. In fall and spring 85% of the 28 brown trout tracked by radio moved east from tagging sites. Movements frequently centered around original stocking sites, streams, and power plant outflows. Fish moved farther in spring (4.4 ± 2.5 km/d) than in fall (2.4 ± 1.7 km/d) seasons, but short-term movement rates did not differ between seasons (0.4 ±0.1 km/h in spring vs. 0.4 ± 0.3 km/h in fall). Females moved farther and faster than males in the fall. Brown trout generally occupied shallow waters < 1 km from shore; 81% of temperatures occupied by trout were between 8–18°C in spring (10.6 ± 2.3°C) and fall (10.1 ± 3.9°C), but turbidity appeared to influence presence or absence of trout near shore on a daily basis. In summer 78% of the 75 brown trout netted were in 8–18° C water (12.6 ± 4.0°C); 88% were caught in or within ±3 m of the thermocline region. Brown trout occupied regions near the thermocline despite widely varying bottom depths and thermocline temperatures. All brown trout were netted within 3.2 km of shore in summer, most in water ≤ 30 m deep; 70% were caught more than 3 m off bottom. The strong association of brown trout with nearshore and thermocline regions may distinguish their distributions from other salmonid species in Lake Ontario.     

Catalyst selection for the synthesis of methylpyrazine

An exploratory research programme on catalysts for the cyclisation of a diamine and a glycol to methylpyrazine is described. More than 80 preparations were tested in standard conditions. The best results were obtained with a mixture of ZnO/Zn-chromite, promoted with a few wt % Pd salt, when working at 640–700 K, atmospheric pressure and in presence of excess steam. Under such conditions, up to 60 mol % selectivity was obtained at over 90% conversion. The aged catalyst was easily regenerable, by simple oxidation of the carbonaceous deposits in flowing air.     

A Monte Carlo approach to X-ray fluorescence analysis at low energies using an annular 55Fe source

The Monte Carlo technique was used to obtain the relative fluorescent intensities of thick samples of calcium, potassium and chlorine as a function of the distance from an annular ⁵⁵Fe source. Comparison with experimentally measured values shows excellent agreement. This study shows that uniformity of excitation intensity across the sample is not the same as uniformity of fluorescent intensity as seen by the detector. Unless dealing with completely homogeneous samples, placement, centering and size of samples at a particular distance from the exciting source are important parameters to be considered.     

Urban development boards in Nigeria: The case of Kano

Among the urban development authorities created in the Third World, those of the state governments in Nigeria are relatively recent. Major legal, institutional and political obstacles hamper their success, particularly their difficult relationship with local government. Technical aspects of their master planning and layout planning illustrate these handicaps, as does their unwillingness to attempt improvement programmes for the older residential areas.     

Molecular Identification of the G-Protein Genes and Their Expression Profiles in Response to Nitrogen Deprivation in Brassica napus

Heterotrimeric guanine nucleotide binding protein (G-protein) consisting of Gα, Gβ, and Gγ subunits is one of the key signal transducers in plants. Recent studies indicated that G-protein has been proposed as an important mediator of nitrogen responses in rice, wheat, and Arabidopsis. However, little is known about these G-proteins in Brassica napus (B. napus), except for three identified G-proteins, BnGA1, BnGB1, and BnGG2. Therefore, the aim of the present study is to characterize the members of the G-protein gene family in allotetraploid B. napus and to analyze their expression profiles in response to nitrogen deprivation. In total, 21 G-protein family members were identified in B. napus, encoding two Gα, six Gβ, and 13 Gγ. Sequence and phylogenetic analyses showed that although genome-wide triploid events increased the number of genes encoding Gα, Gβ, and Gγ subunits, the gene structure and protein properties of the genes encoding each G-protein subunit were extremely conserved. Collinearity analysis showed that most G-protein genes in B. napus had syntenic relationships with G-protein members of Arabidopsis, Brassica rape (B. rapa), and Brassica oleracea (B. oleracea). Expression profile analysis indicated that Gα and C-type Gγ genes (except BnGG10 and BnGG12 were highly expressed in flower and ovule) were barely expressed in most organs, whereas most Gβ and A-type Gγ genes tended to be highly expressed in most organs. G-protein genes also showed various expression patterns in response to nitrogen-deficient conditions. Under nitrogen deficiency, Gα and five C-type Gγ genes were upregulated initially in roots, while in leaves, Gα was downregulated initially and five C-type Gγ genes were highly expressed in different times. These results provide a complex genetic dissection of G-protein genes in B. napus, and insight into the biological functions of G-protein genes in response to nitrogen deficiency.     

基于相位补偿核的GNSS⁃SAR改进后向投影成像算法

在利用全球导航卫星系统反射信号（GNSS?R）的无源合成孔径雷达体制中,目前常采用后向投影算法进行成像处理,但该算法逐点精确聚焦的处理过程使得算法的运算量大。针对上述问题,提出了一种数据分块和构造相位补偿核的改进后向投影算法。改进算法对回波矩阵进行分块,将目标区域成像网格点的最长延迟距离与最短延迟距离等间隔划分,建立相位补偿核,通过距离向搜索操作得到各网格点的相位补偿结果,在方位向相干叠加形成子图,递归合并得到最终图像。定量分析得出,改进算法可有效降低运算量,同时节省内存。仿真结果验证了所提算法的有效性。