The seasonal and spatial variations of labile copper, iron, manganese, lead and zinc sediment fractions in Lake Naivasha, Kenya

Lake Naivasha is a freshwater lake with no surface outlet, lying within a closed basin of the Kenyan Rift Valley. It is perceived to be a lake undergoing anthropogenic stresses. This study is intended to determine the speciation of some selected heavy metals in the sediments of Lake Naivasha, as an indicator of potential pollution of the lake. Sediment and water sampling of the lake was conducted in March and May 2003, during the dry and wet seasons, respectively. Analyses of the speciation of heavy metals in sediment samples (<63 µm faction) were performed on sediment samples collected from five sites within the lake. The study results obtained indicated that influent Malewa River was not a source of labile copper (Cu), lead (Pb) or zinc, despite the river having the highest percentage clay content during the wet season (86%). Copper was highly distributed in the residual sediment fraction (average of 90%). Among the labile sediment factions, the highest quantity of Cu was in the oxidizable phase (3.58 and 2.30 µg g⁻¹ during the dry and wet season, respectively). Carbonate‐bound Cu was sparingly distributed during both the dry and the wet seasons, ranging between 0.74 and 1.81 µg g⁻¹. Iron was highly distributed in the oxidizable sediment phase, exhibiting concentrations ranging between 2.0 and 6.0 (×10³) µg g⁻¹. Relative to the other heavy metals, manganese was distributed in lower proportions in the residual sediment fraction. High concentrations of Pb were observed in the oxidizable phase from most of the sampling sites along the lake shore. Zinc was distributed largely in the oxidizable phase, being highest at sampling site SS, which was located near a municipal sewage input to the lake. The sediments collected at the sampling sites located in the deep portion of the lake exhibited the highest concentrations of labile heavy metals.     

5’-硝基-水杨基荧光酮荧光熄灭法测定煤中微量锗

用荧光熄灭法研究了 5’-硝基-水杨基荧光酮 ( 5’-NSAF) -TritonX 10 0 -Ge 体系的反应条件和测定方法。在0.0 0 2～ 0.0 8mol/L的硫酸介质中 ,TritonX 10 0存在下 ,Ge 与 5’ NSAF反应生成 1∶4的红色络合物 ,使 5’ NSAF溶液的荧光明显熄灭。其激发波长λex=5 0 5nm ,发射波长λem=5 3 3nm。线性范围为 8～ 2 10ng/mL ,检出限为 8ng/mL ,本法灵敏度高 ,选择性好 ,可不经分离直接测定煤中微量锗     

Responses of clonal tea to location of production and plucking intervals

Tea is cultivated in diverse environments causing yield and quality differences in its beverages. To maximise yields and quality, agronomic practices should be optimised. But agronomic recommendations are uniform in different environments in Kenya despite variations in the growth factors responsible for changes in yields and quality. Plucking is labour intensive and a costly agronomic input in tea production. Trials were conducted for ten years in five tea growing regions in Kenya to assess yields and quality responses of clone BBK 35 tea to location of production and harvesting intervals. There were different (P ? 0.05) yields in the various locations, with significant (P ? 0.05) interaction effects between locations and harvesting intervals. Yields declined in three out of five regions but increased in one location with longer plucking intervals. Yields in a geographical area of production can not be used to estimate its expected yields in other tea growing areas. Black tea theaflavins varied significantly (P ? 0.05) with geographical area of production, but other plain tea quality parameters did not vary with location. It is therefore possible to make similar black teas with similar plain tea quality parameters except theaflavins from all tea growing regions of Kenya. Tea quality improved with short plucking rounds. One way to maximise tea quality is through shortening harvesting intervals. It is necessary to establish optimal harvesting rounds in the different tea growing regions in Kenya to maximise yields and quality.     

Information Overload,Similarity, and Redundancy: Unsubscribing Information Sources on Twitter

The emergence of social media has changed individuals' information consumption patterns. The purpose of this study is to explore the role of information overload, similarity, and redundancy in unsubscribing information sources from users' information repertoires. In doing so, we randomly selected nearly 7,500 ego networks on Twitter and tracked their activities in 2 waves. A multilevel logistic regression model was deployed to test our hypotheses. Results revealed that individuals (egos) obtain information by following a group of stable users (alters). An ego's likelihood of unfollowing alters is negatively associated with their information similarity, but is positively associated with both information overload and redundancy. Furthermore, relational factors can modify the impact of information redundancy on unfollowing.     

Ultra-High Strain Ceramics with Multiple Field-Induced Phase Transitions

The induced polarization and longitudinal strain behavior of lanthanum- and titanium-modified antiferroelectric lead zirconate ceramics were measured as functions of electric field as high as 30 kV/mrn (300 kV/cm). Two field-induced phase transitions were observed, both in polarization and strain. Polarization and strain levels greater than 0.5 C/m² and 0.75%, respectively, were achieved in this materials family.     

Comparative Study of Behavior of Lumpy,Small Lumpy,and Lean Chrome Ores During Reduction at Different Temperatures

Metallurgist - The chemical composition of raw material used plays a vital role in achieving the required product quality, in particular, in ferrochrome alloy production. Different types of ore are...     

The Relationship Between Cyberbalkanization and Opinion Polarization: Time‐Series Analysis on Facebook Pages and Opinion Polls During the Hong Kong Occupy Movement and the Associated Debate on Political Reform

Online activity is often cyberbalkanized, but it remains unclear whether this phenomenon leads to polarization of public opinion or if the relationship works in the reverse direction. This study tested the temporal association between cyberbalkanization and opinion polarization during the debate on political reform in Hong Kong. Online communities were constructed by a post‐sharing network of 1,644 Facebook pages (101,410 shares); the differences between intra‐ and inter‐community shares were derived, and a cyberbalkanization index was computed. A time‐series analysis showed that the index temporally preceded the opinion polarization, i.e., most of the opinion poll's respondents gave extreme ratings to government leaders, but not vice versa. The index was particularly predictive of polarization among youth.     

PLZT Phases Near Lead Zirconate: 2. Determination by Capacitance and Polarization

The phases of PLZT, (Pb,La)(Zr,Ti)O₃, or L / Z / T for L <12 and T <10 were detected via determination of capacitance at varying temperatures at 0 field and via polarization at varying fields at room temperature and at selected elevated temperatures. It was possible to determine two different orthorhombic phases, and three rhombohedral (hexagonal) phases, one of which only exists at elevated temperatures. Two sets of phase diagrams were constructed with the phases as a function of temperature, and electric field, respectively. Temperature/field phase diagrams for 0/100/0, 2.95/5, and 4/95/5 were also constructed. A comparison was made between room-temperature and 0 field PLZT phase diagrams determined via X-ray diffraction, capacitance, and polarization.     

Screening of a Novel Fragment Library with Functional Complexity against Mycobacterium tuberculosis InhA

Our findings reported herein provide support for the benefits of including functional group complexity (FGC) within fragments when screening against protein targets such as Mycobacterium tuberculosis InhA. We show that InhA fragment actives with FGC maintained their binding pose during elaboration. Furthermore, weak fragment hits with functional group handles also allowed for facile fragment elaboration to afford novel and potent InhA inhibitors with good ligand efficiency metrics for optimization.