Decandrinin, an unprecedented C9C_9-spiro-fused 7,8-seco−ent seco-ent-abietane from the Godavari mangrove Ceriops decandraCeriops\ decandra

Decandrinin (1), an unprecedented $C_9$-spiro-fused 7,8-$seco-ent$-abietane, was obtained from the bark of an Indian mangrove, $Ceriops\ decandra$, collected in the estuary of Godavari, Andhra Pradesh. The constitution and the relative configuration of 1 were determined by HRMS (ESI) and extensive NMR investigations, and the absolute configuration by circular dichroism (CD) and optical-rotatory dispersion (ORD) spectroscopy in combination with quantum-chemical calculations. Decandrinin is the first 7,8-$seco-ent$-abietane

Penggunaan Metode Eksperimen Pada Pembelajaran Materi Sifat Bahan Dan Kegunaannya Terhadap Hasil Dan Respon Belajar Siswa Kelas IV Min Tungkob Aceh Besar

The research on the use of experimental methods in learning characteristics of material and its usefulness toward students\u27 achievements and learning responses of Level 4 primary school students of MIN Tungkob Aceh Besar aims to determine students\u27 learning outcomes and responses toward the use of the method. This study uses experimental research. The data collection techniques were using test and distributing questionnaire to the students. The samples in this experimental study were students of class IV3 totaling 34 people as the experimental class and the class IV4 totaling 31 people as the control class. The data, which is the students\u27 learning outcomes collected from pretest and posttest, were analyzed using t-test formula. The data from the students\u27 questionnaire responses were analyzed using percentage formula.The result was that the students\u27 learning outcomes from the experimental class and the control class showed significant differences. Students\u27 responses toward the use of experimental methods in learning material characteristics and its usefulness were also very positive, where the students are very excited and interested in learning to use the experimental method in the study of material characteristics and its usefulness

Border dispute settlements in Africa and their impact on human rights of indigenous occupants of displaced territories

Africa has, within its vast territory, seen many disputes over boundaries between states. These disputes in Africa usually emanate from conflict between states, which arises, in some cases, from division between different ethnic groups, and more often than not, from different interests with regard to the land which forms the subject of the dispute. Africa has witnessed a large number of these disputes culminate in war between states, which carry on for years, with resolution seeming impossible or far-fetched. Examples of such are the long-running war between Eritrea and Ethiopia, Nigeria and Cameroon, just to name a few. This is why border disputes are sensitive issues which must be handled with utmost delicacy.Border disputes usually centre on, and are often presented as claims to territory, over which there lays uncertainty as to which state has sovereign title, the said territory being situated in a border area. The disputes that arise are often due to imprecision or lack of a frontier line between disputant states. Depending on the circumstances of a particular case, settlement may take the form of interpretation of a border treaty, delimitation (i.e. the agreed description of the common boundary on paper), demarcation (i.e. laying more precise alignment on the ground, by means of detailed survey and emplacement of beacons) or indeed all of the aforementioned1. The methods of reaching settlement may be through negotiation between heads of state, mediation by an appointed head of state, arbitration by an international tribunal or judicial settlement by an international court such as the International Court of Justice (ICJ) ". Border dispute settlement involves states, as parties to the case, trying to put to rest a dispute in a manner that is to the common benefit of the states involved. However, the dispute appears more complex when territories under dispute, are populated with occupants who are indigenous to the said territory. There exists the question of possible human rights implications created for these occupants due to the outcome of the dispute settlements for the state parties. An example of such a scenario can be found in the dispute over the Lake Mweru-Lake Tanganyika border between Zambia and the Democratic Republic of Congo (DRC). The border area is inhabited by the Bwile people who exist both on the Zambian and the Cogolese side of the border. Another such example is the case of the dispute between Nigeria and Cameroon over the Bakassi Peninsula. The peninsula is home to the Efike and Ambazonian people although the territory, by an ICJ ruling was awarded to Cameroon.This directed research investigates the existence possible human rights implications for the indigenous occupants of the disputed territories, as a result of the border dispute settlement reached by the state parties

Measurements and modeling of gas fluxes in unsaturated mine waste materials

Accurate measurements and predictions of surface CO₂ fluxes are needed to quantify biogeochemical reaction rates in unsaturated geologic media and soils. However, no standard appears to exist for establishing the accuracy of field measurements of soil respiration rates. As a result, a technique to measure CO₂ fluxes from the soil surface to the atmosphere was recently developed and verified in mesocosms over the range of CO₂ fluxes reported for field conditions. The method, termed the dynamic closed chamber (DCC), was shown to accurately measure CO₂ fluxes from ground surface to the atmosphere in mesocosms. The main advantage of this direct technique is the almost instantaneous estimation of the CO₂ flux. Although the DCC is a promising technique, its ability to accurately quantify surface CO₂ flux under field conditions remains to be verified. The field application of the DCC is investigated in this thesis with a particular focus on quantifying reaction rates in waste-rock piles at the Key Lake uranium mine in northern Saskatchewan, Canada. It should, however, be noted that the dominant geochemical reactions in the two waste-rock piles at the Key Lake mine were not typical of acid rock drainage (ARD) waste-rock piles. The CO₂ fluxes measured in this study occur in the organic material underlying the waste rocks, in contrast to ARD waste-rock piles where O₂ consumption and CO₂ production are the results of sulphide oxidation and carbonate buffering. This work provided a complete suite of measurements required to characterize spatial distribution of CO₂ fluxes on larger-scale studies of waste-rock piles. There has been no previous field-scale study to quantify CO₂ fluxes across a waste-rock pile. The ability of the DCC method to accurately quantify field soil respiration was demonstrated by comparing the DCC fluxes to those obtained using two other CO₂ flux measurement techniques: the static closed chamber (SCC) and eddy covariance (EC) methods. The DCC yielded comparable data but had distinct advantages over the two other methods in terms of speed and repeatability. The DCC was also used to investigate CO₂ fluxes under the climatic variables (e.g., rainfall and evaporation) that affect soil water content at the Deilmann north (DNWR) and Deilmann south (DSWR) waste-rock piles, at the Key Lake uranium mine. The effects of rainfall events on waste-rock surface-water conditions and CO₂ fluxes were of short duration. A simple model for predicting the effects of soil water content on CO₂ diffusion coefficient and concentration profiles was developed. The model was verified with measured CO₂ fluxes obtained from mesa-scale columns of unsaturated sand. Verification of the model showed good agreement between predicted and measured data. The model was subsequently used to predict CO₂ diffusion and concentration profiles in response to changes in soil water contents in the piles and also to predict surface CO₂ fluxes from the DNWR and DSWR for a 6-d test period [August 1 (day 3) to August 6 (day 8) 2002] following a 72.9 mm precipitation event over the initial 48-h [July 30 (day 1) to July 31 (day 2) 2002]. The model predicted surface CO₂ fluxes trends that were very similar to the measured surface CO₂ fluxes from the DNWR and DSWR piles during the test period. Based on the tests conducted in this thesis the DCC method has shown to be suitable for field applications to quantify CO₂ fluxes and to characterize the spatial and temporal dynamics of CO₂ fluxes from unsaturated C-horizon soils and waste-rock piles.Applied Science, Faculty ofMining Engineering, Keevil Institute ofGraduat

Chemical profiling of cultivated and wild African ginger and absolute configurations of compounds from mangroves and Ancistrocladus species

Medicinal plants and natural products have played a pivotal role as a source of drug leads that has led to improving health conditions and have provided humankind with numerous pharmacologically active drugs. Other than the biological screening and chemical profiling of plant extracts, the isolation, purification and elucidation of the full absolute structures of natural compounds are some of the key areas required in the time-consuming process of drug discovery based on natural products. Elucidation of the absolute configuration (AC) of chiral natural products represents one of the most challenging tasks in the determination of full molecular structures but still remains an essential concept in drug discovery as enantiomers do not always exhibit the same pharmacological activities. The present study successively investigated the UPLC MS and GC MS chemical profiles of organic extracts from the wild and cultivated popular, but threatened medicinal plant, African ginger {i.e., Siphonochilus aethiopicus (Schweinf.) B.L. Burtt} and the absolute configurations of limonoids, diterpenoid and dimeric naphthylisoquinoline (NIQ) alkaloids isolated from mangroves and Ancistrocladus species. The first part of the study aimed at exploring the similarities and/or differences between the UPLC MS and GC MS chemical profiles of wild and cultivated African ginger rhizomes and evaluating the antimalarial activity of extracts from both sources taking into account that traditional healers are not unanimous on using the cultivated material for medicinal purposes. UPLC MS chemical profiling of n-hexane/DCM (1:1) extracts from air-dried rhizomes has revealed the presence of additional peaks in the chromatographic profiles of wild plants but also confirmed the major peak in the profiles of both wild and cultivated rhizomes to be the common furanoterpenoid (4), known as Siphonochilone. The compound was unexpectedly observed to be highly unstable and generated artefact sesquiterpenoids after autoxidation. Autoxidation was observed for the pure compound, as well as in dried and powdered rhizomes. The latter aspect confirmed that the artefact sesquiterpenoids only form after autoxidation and do not occur in the fresh plant as reported in many publications. GC MS analyses of n-hexane extracts from fresh, air-dried and oven-dried plants confirmed the presence of Siphonochilone (4) from both sources but further revealed the presence of eucalyptol, which was significantly depleted after drying. Antimalarial screenings of n-hexane/DCM (1:1) extracts against the chloroquine-sensitive (CQS) strain of Plasmodium falciparum (NF54) did not show substantial change in the IC50 values for both sources. The second part of the study aimed at elucidating the absolute configurations of two limonoids, one diterpenoid and two NIQ dimers. This was tackled by conducting quantum-chemical calculations of chiroptical spectroscopy, such as circular dichroism. Absolute configurations were deduced from the comparison between experimental chiroptical data with the curves predicted for the possible enantiomers. The absolute configurations of the limonoids thaixylomolin A (12) and B (13) were respectively revealed as 1R,5R,8R,9R,10R,13S,14R,15S,17S and 1R,2R,3S,4R,5S,9S,10R,13R,17R while that of the diterpenoid decandrinin (14) was 5S,9S,10R and those for the NIQ dimers mbandakamines A (15a) and B (15b) validated published data.Dissertation (MSc)--University of Pretoria, 2015.ChemistryMScUnrestricte

Spontaneously Settled Refugees in Northwestern Province, Zambia

Recently, the UNHCR commissioned researchers from the University of Zambia to conduct a socioeconomic survey and census of ‘spontaneously settled’ Zairean and Angolan refugees in the Northwestern Province. After a brief description of the methodological issues and logistic difficulties of the research the major results of the survey are presented. </jats:p

Design and application of a dynamic closed chamber system for measuring CO2 flux from unsaturated C-horizon soils and waste-rock piles to the atmosphere

A method based on a dynamic closed chamber system (DCCS) for measuring CO2 effluxes from unsaturated soils and waste-rock piles was developed and tested in well-constrained unsaturated minicosms (0.58 m dia. x 1.2 m thick), a mesocosm (2.4 m dia. x 3.2 m thick), and waste-rock piles. The DCCS method was compared and evaluated against traditional soil respiration measurement methods (e.g., static flux chamber method, and concentration-gradient calculations). Results of the studies showed that the DCCS yielded accurate measurements of CO2 fluxes and that the static chamber underestimated actual effluxes especially when using long adsorption times (> 24 h). The concentration-gradient method yielded reasonable estimates of CO2 effluxes but was time consuming and required the determination of moisture content to calculate gas diffusion coefficients. Results of studies carried out on waste-rock piles, showed that the DCCS is a relatively quick technique (2 to 10 min) that can be used to quantify spatial and temporal distribution of CO2 fluxes at the field scale. The DCCS yielded field measurements of CO2 fluxes that were reproducible over time at individual chamber locations. The average CO2 fluxes obtained over the summer study-period of 2000, for Deilmann north and Deilmann south waste-rock piles were 181 ± 41 mg CO2 m-2 h-1 (n = 27) and 205 ± 60 mg CO2 m-2 h-1 (n = 48), respectively. A statistical Student's t test yielded no significant difference between the two sets of data. As a result, the two mean values were combined to yield an overall mean value of 193 ± 73 mg CO2 m-2 h-1 (n = 68) for the two waste-rock piles. Most temporal changes were attributed to seasonal variations in temperature (7.9 to 16.5 °C). The DCCS has the advantage of being able to measure CO2 fluxes in situ at the same locations using the same chambers without greatly disturbing the soil. The results of this study will be used in future modeling exercises to quantify the rates of sulfide oxidation and carbonate buffering reactions in these waste-rock piles

Measurements and model predictions of the rate of drying with time at the surface of a waste-rock pile after heavy rainfall events

Measurements and model predictions of changes of water contents at the surfaces of waste-rock piles are needed in the development of a long-term management plan for waste-rock piles. This study investigated a short-term multi-day [July 28 to August 4, 2002] rate of drying with time at the near-surface of the Deilmann north waste-rock pile (DNWR) at the Key Lake uranium mine, northern Saskatchewan, following the cessation of 75.9 mm rainfall over the initial 48-h period. The water content was determined using the gravimetric method. The initial measured water content profile data were used with SoilCover numerical model to predict changes in water content profiles with time at the near-surface of the DNWR. Results of both the measurements and numerical predictions showed that the impact of heavy rainfall events on waste-rock surface water content at the DNWR is of relatively short duration. The waste-rock surface (0 m) water content was very sensitive to changes in climatic conditions after precipitation, exhibiting a power decrease with time. The drying rates at greater depths (>0.05 m) decreased slowly with time. This behavior was attributed to hydraulic properties of the waste-rock pile. These data can be of value in the long-term development of a plan for mine waste management.Applied Science, Faculty ofMining Engineering, Keevil Institute ofUnreviewedOthe

Short-Term Predictions of Evaporation Using SoilCover at the Near-Surface of a Mine Waste Pile following Heavy Rainfall Events

Accurate measurements and predictions of near-surface soil drying and evaporation following heavy rainfall events are often needed for research in agriculture and hydrology. However, such measurements and predictions at mine waste pile and tailing settings are limited. The prediction of evaporation at mine waste piles is essential for many problems in geotechnical engineering, including the design of soil cover systems for the long-term closure of hazardous waste sites, and thus mitigates, for example, the generation of acid mine drainage (AMD) and metal leaching. AMD is one of mining&rsquo;s most serious threats to the environment. This study investigated the short-term (8 days) and medium-term (27 days) drying rates and evaporative fluxes at the surface and near-surface of the Deilmann South waste-rock (DSWR) pile at the Key Lake uranium mine, northern Saskatchewan, using the gravimetric (GV) method and SoilCover (SC) model, respectively, during and following heavy rainfall events for the environment. The SC simulation results showed that during the weather-controlled stage (Stage I) of the first 5-day period of rainfall events, while the surface was wet, the potential evaporation (PE) was equal to the actual evaporation (AE) (i.e., AE/PE = 1). As the surface became drier on Day 6, the cumulative PE began to separate from the cumulative AE and the surface&rsquo;s drying rate rapidly diverged from those at the deeper depths. This occurrence signaled the onset of the soil profile property-controlled stage (Stage II). As the drying continued, the surface became desiccated and the slow-rate drying stage (Stage III) was established from Day 7 onward. The SC-simulated AE results were compared to those measured using the eddy covariance (EC) method for the same test period at the DSWR pile in a different study. The comparison showed that the two methods yielded similar AE results, with 18% relative errors. The results of this study provided the opportunity to validate the SC model using actual data gathered under field conditions and to ascertain its ability to accurately predict the PE and AE at the surfaces of mine waste piles