Determination of Silver Binding to Natural Organic Matter Using Ion Selective Electrode

Natural organic matter (NOM) is considered an important factor in the protection of the aquatic environments; organic ligands can complex with metals, to decrease their toxicity and bioavailability. NOM is measured as dissolved organic carbon (DOC) in mg C/L. Silver metal can enter into the aquatic environment from natural and anthropogenic sources, and is found in different chemical forms. Free silver ion (Ag+) is considered as the most toxic form of the metal. However, it can form complexes with both inorganic and organic ligands, such as ammonia, chloride, hydroxyl, carbonato, phosphato, and thiol groups. Thiol is the most important ligand because it forms very strong complexes with Ag. To date, the behavior of silver in the aquatic environment, is still not well understood. The aim of this research is divided to three steps. First, the experimental objective of this study was to determine free silver ion binding to NOM in three different commercially available sources. Also, samples were tested under different pH (4.0, 6.0, 8.0 and 10.0) conditions. In the laboratory tests, the technique that was used was a flow through ion selective electrode (ISE) system utilizing an Ag2S electrode. In the second step, Windermere Humic Aqueous Model (WHAM), which is a very important risk assessment tool, was validated by comparison WHAM and ISE silver speciation results. Silver binding to NOM depends on the specific ligands in each samples. For example, the sample with the most sulphur content was also strongest in binding to silver. Also, pH plays an important role in silver bioavailability. When pH increases, NOM has more sites available to bind to silver ions. In contrast, proton concentration increases at low pH and competes with free silver cations to bind with NOM. Finally, optical characterization of NOM was performed using absorbance (SAC340) and fluorescence indices (FI) in order to distinguish among NOM samples. It found that optical characteristics have similar value for all NOM samples

Prevalence of overweight and obesity among 6-13 year old Kuwaiti school children: secular trends, risk factors and their implications

Evidence of childhood obesity as a strong predictor of risk of non-commnuicable diseases has been accumulating world wide over the last three decades. The focus of this study was to provide a cross-sectional picture of the influence of the demographic and epidemiological transition on health habits, lifestyle changes, dietary patterns and obesity risk among 6-13 year old Kuwaiti school children. A sample of 1536 Kuwaiti school children was recruited in 2001 through a multi-stage cluster and stratified sampling technique to investigate the impact of these environmental factors. The study design included administration of a structured and pretested socio-demographic, health habits and lifestyle questionnaire. Of these a sub-sample of 224 ramdomly selected subjects( >14% of total) (with a response rate of 86.6% n=194) undertook a 7-day dietary intake and physical activity record and anthropometric measurements. Some biochemical indices of nutritional risk were further assessed among 224 of eligible subjects (mean age 10.3± 2-4 yrs; response rate 50.9%,n =114)in 2003. Findings from this study confirm the presence of high income and increased food availability and choice the consequences of which included intake of high energy, high fat, sugar and salt-based diets (above recommended intakes) coupled with a sedentary lifestyle with low levels of daily total energy expenditure. Positive energy balance was confirmed by evidence of overweight and obesity (>65% above 85th percentile for BMI cut-off of 25k gm-2) with at least 21% obese (above 95h percentile i.e. BMI 30 kg/m2), increased ZSFT and increased WHR. Furthermore, biochemical evidence of the nutritional risk was found with high levels of serum fasting glucose, total triacylglycerols and total cholesterol levels associated with low HDL-c levels, the latter further supporting the notion that their levels of physical activity were low (mean physical activity level PAL of 1.29 ±0.13). The biochemical indices suggest that nearly 15% of subjects were at risk of the metabolic complications. These findings also evidenced by increasing trends of obesity over the last two decades in a similar age-matched cohort suggest the presence of a nutritional transition with potentially serious health consequences. This provides opportunities for action and implementation of new nutrition and public health actions to avert any health crisis in this population. A strategic framework for intervention involving school-based nutrition and health promotion, community, family and stakeholder participation and government policy reviews and interventions have been proposed as a medium to long term solution

An E-Learning Investigation into Learning Style Adaptivity

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The Word gid in Najdi Arabic: An Evidentiality Head

This research paper investigates the word gid which is used in Najdi Arabic, a dialect spoken in Najd region in Arabic peninsula. This particle is analyzed syntactically using the recent assumptions of the minimalist program (Chomsky 1993, 1995, and subsequent work). As for the findings, it turns out that gid functions as a head that instantiates its maximal projection above TP and under CP. So, this word is not a property of TP domain nor a CP domain. Due to the fact that this word is only used when a speaker is certain of the propositional content of his/her utterance, we argue that gid is an evidential head that scopes over the tense layer. Furthermore, we argue that gid has an EPP feature, hence the specifier position of the functional phases headed by it must be filled by some element which is the subject. This accounts for the fact that subject must precede gid in declarative sentences. Additionally, gid has [PAST] feature which is uninterpretable and hence must be deleted before the derivation is handed over to the LF following the general lines of feature deletion of Chomsky (1995 and 2005). We argue that the deletion of [PAST] feature is conducted through an Agree operation that is established between gid and the verb. This is why gid comes exclusively with past tense. Otherwise [PAST] feature on gid remains active, leading to the ungrammaticality of the given sentenc

A differential operator realisation approach for constructing Casimir operators of non-semisimple Lie algebras

We introduce a search algorithm that utilises differential operator realisations to find polynomial Casimir operators of Lie algebras. To demonstrate the algorithm, we look at two classes of examples: (1) the model filiform Lie algebras and (2) the Schr\"odinger Lie algebras. We find that an abstract form of dimensional analysis assists us in our algorithm, and greatly reduces the complexity of the problem.Comment: 22 page

On Casimir Operators of Conformal Galilei Algebras

In previous work, we introduced an algorithm that utilises differential operator realisations to find polynomial Casimir operators of Lie algebras. In this article we build on this work by applying the algorithm to several classes of finite dimensional conformal Galilei algebras with central extension. In these cases we highlight the utility of an algebra anti-automorphism, and give relevant details through key examples.Comment: 18 page

Optimizing Key Distribution in Peer to Peer Network Using B-Trees

Peer to peer network architecture introduces many desired features including self-scalability that led to achieving higher efficiency rate than the traditional server-client architecture. This was contributed to the highly distributed architecture of peer to peer network. Meanwhile, the lack of a centralized control unit in peer to peer network introduces some challenge. One of these challenges is key distribution and management in such an architecture. This research will explore the possibility of developing a novel scheme for distributing and managing keys in peer to peer network architecture efficiently

Clean Energy via Hydrothermal Gasification of Hydrocarbon Resources

Synthesis gas and clean hydrogen will become key components of the energy industry. Their production from fossil fuels is likely to be a major source of these energy vectors and chemical building blocks for many decades ahead. Currently all the hydrocarbon conversion steps are carried out above surface, starting from oil and gas extraction and transportation to dedicated plants, with any separated CO2 returned back to the fields. However, there are increasingly strong drivers to reduce the environmental impact of the oil processing industry, by e.g. minimising the “footprint” of such operations and leaving the undesirable and low- value material underground (CO2, heavy metals, sulphur). One novel approach, which could be key, would be the production of syngas or hydrogen via downhole hydrothermal processing/partial oxidation. This envisages using the sub-surface well system as a continuous processing and reactor network to carry out as much as possible of the required separations and conversions in the well system (underground) or close to it (at the wellhead). The goal is to radically reduce, by design, the overall environmental footprint (by minimising the number of species extracted other than final products, the number of external processing steps and the need for transport to/from the underground fields) while improving the overall economics of new fields and increasing the efficiency of recovery from conventional, mature reservoirs. This thesis presents research work on the hydrothermal gasification and partial oxidation of n-hexadecane, as a heavy hydrocarbon model, under potential downhole conditions. Thermodynamic analysis was carried out to predict equilibrium limits showing optimum conditions for maximising the theoretical yield of hydrogen under oxidative and non- oxidative hydrothermal conditions. This was followed by experimental analysis where hydrothermal gasification of n-hexadecane was conducted in high pressure flow reactor system. Conversion data at different residence times, and temperatures were used to determine the reaction kinetic data at sub- and supercritical water conditions. The new experimental system was modified for partial oxidation of n-hexadecane, to enable combined total decomposition of H2O2, in a separate reactor, with partial oxidation of n-hexadecane, in a gasification reactor. The experimental data were consolidated with the development of a new CFD model for supercritical water gasification of hexadecane, and it was also used to validate and tune our kinetic data obtained experimentally by taking into account the radial effects occurring from the laminar flow under the experimental conditions. Finally, a new subsurface georeactor system model was developed, using ASPEN HYSYS, which shows thermodynamically the optimal conditions for maximising the system’s energy efficiency showing potential conditions for maximising energy recovery with hydrogen cogeneration. These results are discussed with view of opening new routes for clean generation of hydrogen and synthesis gas via underground gasification of hydrocarbons.Open Acces